[0001]The present invention relates to a manufacturing method and a different thickness steel tube different thickness steel tube.
　This application, on March 11, 2016, and Japanese Patent Application No. 2016-048657 filed in Japanese, on December 19, 2016, and Japanese Patent Application No. 2016-245864 filed in Japanese on the basis of the priority claiming the rights, incorporated these contents here.
BACKGROUND
[0002]
　As the vehicle body member constituting the vehicle body, a portion of absorbing been collision energy crushed by the impact load when an impact such as a collision, it is desired to have a portion for protecting the vehicle body without being crushed . In order to provide such body member, utilizing the thickness differs different thickness steel tube along the longitudinal direction are considered.
[0003]
　For example, FIG. 7 of Patent Document 1, as preparation of drawn steel pipe having a plurality of diameters, movably secured to the pull-out direction of the die and the tap was pulled while being nipped bearing surface each which faced each other to the method of the stepped drawn pipe is disclosed having a predetermined inner and outer diameters in a plurality of locations.
[0004]
　Further, FIG. 7 of Patent Document 2, as a method for producing a different thickness steel tube and using a die and a plug having a diameter of each of two stages, the bearing diameter of the die d 2 (small) and plugs bearing diameter d 3 ( a step of material steel pipe by a small diameter) is molded is dimensioned regulated, bearing diameter d of the die 2 and (small) bearing diameter d of the plug 4 steps the material steel pipe is molded is dimensioned restricted by the (large) 1 (the large) bearing diameter of the plug d 4 material steel pipe by the (large
CITATION
Patent Document
[0005]
Patent Document 1: Japanese Sho 59-73115 Patent Publication
Patent Document 2: Japanese Patent 2012-16712 JP
Summary of the Invention
Problems that the Invention is to Solve
[0006]
　Incidentally, the vehicle body member or body parts constituting the vehicle body, bending the hollow member closed section processing is given, are those partially bent portion is formed. Different thickness steel tube obtained by the manufacturing method of Patent Document 1 or Patent Document 2, since the process over the entire length of the base pipe is applied, in a state in which the whole has work hardening. This way a whole subjected to a bending process or the like to work hardened differential thickness steel tube, there is a need to mitigate the work hardening of the different thickness steel tube pre heat treatment is performed. If, if this heat treatment is not necessary, it can be expected significant labor saving in processing the different thickness steel tube to a vehicle body member. Further, by omitting the heat treatment, it becomes possible to prevent deterioration of the steel structure of different thickness steel tube.
[0007]
　The present invention was made in view of the above circumstances, there is little processing amount at the time of manufacturing, manufacturing methods and differences of the different thickness steel pipe which does not require heat treatment of annealing or the like when performing processing after bending, etc. the provision of thick steel pipe an object of the present invention.
Means for Solving the Problems
[0008]
　To solve the above problems, the present invention employs the following aspects.
(1) A method of manufacturing differential thickness steel tube according to one embodiment of the present invention is a method of producing a different thickness steel tube from a hollow cylindrical blank tube, placing the blank tube into a die, the blank tube while restricting the movement in the longitudinal direction, the locking process and to push the plug from one end of the base pipe by expanding the outline of the one end engaged with the die; solving the regulation of the mother tube Meanwhile, while the locking of the mother tube was maintained, by pushing towards the other end of the further the mother tube and the plug, in addition to ironing to expand the inner shape while maintaining the outer shape of the base pipe having; and ironing forming a thin portion.
(2) In the method for manufacturing differential thickness steel pipe according to (1), in the ironing step, by stopping the pushing of the plug in the middle, leaving a raw portion in the other end of the base pipe it may be.
(3) In the method for manufacturing differential thickness steel pipe according to (1) or (2), the thinning rate of the thin portion in the ironing process may be in the range of 10% to 90%.
(4) above (1) to (3) In the method for manufacturing differential thickness steel tube according to any one of the locking in the step and the ironing step, smaller outer dimensions than the inner dimensions of the base pipe a tip having a base end portion having an outer dimension less than the magnitude of the external dimensions of larger and the base pipe than inner dimensions of the blank tube, and tapered toward the tip from the base end portion so that may be used the plug and a tapered portion provided between the tip and the base end portion.
(5) above (1) to (3) In the method for manufacturing differential thickness steel tube according to any one of the locking in the step and the ironing step, larger and than said inner dimensions of said base pipe a proximal end portion having an outer dimension less than external dimensions of the blank tube, contiguous to the tip end of said proximal portion, a distal portion that tapers as the distance from the proximal end, may be used the plug with the .
The method of manufacturing a different thickness steel pipe according to (6) above (4) or (5), said proximal end, and a large base end portion arranged on the distal end side than the large base end portion a small proximal end portion is also small outer dimensions, may have.
[0009]
(7) A method of manufacturing differential thickness steel pipe according to another aspect of the present invention is a method of producing a different thickness steel tube from a hollow cylindrical blank tube, placing the blank tube into a die, the blank tube longitudinal to the movement while restricting the direction, the locking process and to push the first plug from one end of the base pipe by expanding the outer dimension of said one end engaged with the die; the mother tube a draw-out step further withdrawing the first plug; while solving the regulation of the mother tube, while the locking of the mother tube was maintained, the second plug having a different outer shape than the first plug by pushing toward the other end side from the one end of the base pipe, and ironing forming a thin portion by the addition of ironing to expand the inner shape while maintaining the outer shape of the mother tube; having.
(8) In the method for manufacturing differential thickness steel pipe according to (7), in the ironing process, a small small tip than inner dimensions of the base pipe, larger outer shape than the inner dimensions of the base pipe a medium-size section having a size, and a large portion having an outer dimension less than external dimensions of larger and the base pipe than the outside dimension of the in-shaped part, provided between the small tip and the in-shaped portion a first tapered portion, a second tapered portion provided between the in the form portion and the large portion, may be used the second plug with a.
(9) In the method for manufacturing differential thickness steel pipe according to (7), in the ironing process, the base end portion having an outer dimension less than external dimensions of larger and the base pipe than inner dimensions of the base pipe When; it may be used the second plug with a; a third tapered portion that tapers toward the tip portion from the proximal portion.
(10) In the method for manufacturing differential thickness steel tube according to any one of the above (1) to (9), wherein the die comprises a hollow small portion having the inner shape dimension corresponding to the outer dimension of the base pipe; a hollow large portion having a larger inner dimensions than the outer dimensions of the base pipe; wherein provided between the hollow small portions and the hollow large portion and, towards the said hollow large part to the hollow small portion hollow tapered portion tapering and; may be provided.
(11) In the method for manufacturing differential thickness steel pipe according to (10), said die, and provided in a part of the longitudinal direction of the hollow small portion, inner dimensions larger than the outside dimension of the base pipe it may further comprise an aerial diameter in with.
(12) In the method for manufacturing differential thickness steel tube according to any one of the above (1) to (11), further comprising a drawing step for working aperture with respect to the base tube after the ironing step it may be.
[0010]
Method for manufacturing differential thickness steel tube according to still another aspect of (13) The present invention is a method for producing the different thickness steel tube from a hollow cylindrical blank tube, placing the blank tube into a die, the element by pushing the plug simultaneously or alternately to each of the one end and the other end of the tube, and the locking step of locked to the die by expanding the outline and outer shape of the other end of the one end; while inserting the plug into the one end side, an extraction step and withdrawing the plug of the other end; while the one end side is engaged in the die, further said plug being inserted into said one end by pushing toward the other end of the base pipe, the first ironing process and to form a first thin portion added ironing to expand the inner shape while maintaining the outer shape of the mother tube; the while withdrawing the plug at one end, the other And insertion step of inserting the plug in the side; leave the other end side is engaged in the die, by pushing the plug of the other end side further toward the one end of the base pipe, said element a second ironing step of forming a second thin portion added ironing to expand the inner shape while maintaining the outer shape of the tube; has, in the locking step, when pushing the plug simultaneously , and freely moving the base tube along the longitudinal direction of the mother tube, when pushing the plug alternately, it restricts the movement of the blank tube in the pushing direction of the plug.
(14) In the method for manufacturing differential thickness steel pipe according to (13), squeezing the blank tube after the second ironing step, may further include a drawing process.
(15) In the method for manufacturing differential thickness steel tube according to any one of the above (1) to (14), said base tube may be a seamless steel pipe.
[0011]
(16) different thickness steel tube according to one embodiment of the present invention adopts the following configuration: and provided on one side of the longitudinal direction, the greatest outer shape when viewed in cross section perpendicular to the longitudinal direction an enlarged portion having dimensions, the provided on the other side of the enlarged portion when viewed along the longitudinal direction and, and a small wall thickness thinner portion than the expansion portion; of the enlarged portion the average value of the hardness H1, the average value of the hardness of the thin portion when the H2, satisfy H2> H1.
　As the method of obtaining the average value of the hardness described herein, the portion in the thickness direction center position of the different thickness steel tube prepared, 5-point at 1mm intervals along the longitudinal direction of the DosaAtsu steel pipe, the hardness was measured and determined by calculating the average value of the hardness of these five points. If, when it is difficult to obtain the measurement points at five points to size is small, the hardness of the 5-point measured at 1mm intervals along the circumferential direction of the different thickness steel tube, calculates the average value of these five points it may be used Te.
(17) In the different thickness steel pipe according to (16), may be employed the following configuration: disposed on the other side of the thin portion when viewed along the longitudinal direction, the thin portion Furthermore the thick-walled portion is thicker than provided; the average value of the hardness of the thick portion in the case of the H3, H2> satisfy H1 ≧ H3.
(18) In the different thickness steel pipe according to (17), may be employed the following configuration: the thin portion, the thickest thin straight tube portion in the thin portion, the straight tube portion and wherein the first tapered portion outer shape with provided between enlarged portion toward the enlarging portion is enlarged, thicker wall thickness toward the thick portion together is provided between the straight tube portion and the thick portion and a second tapered portion comprising a; the average value of the hardness of the first tapered portion H4, the average value of the hardness of the straight pipe portion H5, and the average value of the hardness of the second tapered portion was H6 If, satisfy both equations of H5> H6 ≧ H3 and H5> H4> H1.
In different thickness steel tube according to any one of (19) above (16) to (18), the thickness of the thin portion, when viewed along the longitudinal direction, though partially thickened it may be.
(20) In the different thickness steel pipe according to (16), the combination of the enlarged portion and the thin portion may be symmetrically provided on the longitudinal ends.
(21) In the different thickness steel pipe according to (20), may be employed the following configuration: arranged between a pair of the thin portion, further comprising a thick-walled portion is thicker than the thin portion ; the average value of the hardness of the thick portion in the case of the H7, H2> satisfy H1 ≧ H7.
[0012]
(22) different thickness steel pipe according to another aspect of the present invention adopts the following configuration: and provided on one side of the longitudinal direction, most meat when viewed in cross section perpendicular to the longitudinal direction the thickness and the thick-walled portion, said and provided on the other side of the thick portion, wherein the wall thickness is thin walled portion than the thick portion, the provided; in outer dimensions along the longitudinal direction is constant There; the average value of the hardness of the thick portion H8, the average value of the hardness of the thin portion when a H9, satisfy H9> H8.
In different thickness steel tube according to any one of (23) above (16) to (22), the thin portion, when viewed along a circumferential direction of the thin portion in a cross section perpendicular to the longitudinal direction , relatively, and the thickness is thin and has high hardness region, a low hardness region thicker the wall thickness may have a rotationally symmetrical shape alternating along the circumferential direction.
(24) different thickness steel tube according to any one of the above (16) to (23), a seamless steel pipe or as a material.
　As the above-mentioned various hardness, it can be used, for example Vickers hardness.
Effect of the invention
[0013]
　Of the present invention, for example according to the method of manufacturing differential thickness steel pipe according to (1), while to engage with the die by expanding one end of the outer shape of the base pipe, the plug element tube from the one end by pushing, you can perform ironing to expand the inner shape while maintaining the outer shape of the base pipe. Therefore, the processing amount to be added to one end of the base pipe is requires less processing amount only to expand its external dimensions. Thus, since one end of the base pipe is work hardening is small, the heat treatment of annealing or the like when performing processing after bending or the like can be eliminated.
　Also, in order to perform pushing by ironing the plug while keeping engaged the one end of the base pipe in a die to blank tube, it is not necessary to fix the base pipe itself against the die, relatively moving the plug relative to the die processing can be carried out ironing only by.
　Therefore, according to the manufacturing method of the different thickness steel pipe according to the embodiment of the present invention, a portion of the wall thickness is greater at one end, the different thickness steel tube and the thin portion is formed which receives the ironing can be easily produced .
[0014]
　In particular, according to the method of manufacturing differential thickness steel tube described in above (2), the other end of the base pipe, the processing amount because leave the unprocessed portion of zero, the processing such as bending for this unprocessed portion It can be made unnecessary the heat treatment of annealing, such as when performing the post-processing.
[0015]
　According to the manufacturing method of the different thickness steel pipe according to (7), for example, can be inner shape dimensions in the thin portion provided with two different areas, stepwise thickness along the longitudinal direction and It can produce different differential thickness steel strength.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016]
[1] a process diagram illustrating the manufacturing method of the different thickness steel pipe according to the first embodiment of the present invention, is a cross-sectional view taken in cross-section including the axis of the base pipe.
[Figure 2] A diagram showing an example of a different thickness steel tube manufactured by the manufacturing method of the different thickness steel tube of the embodiment, a sectional view taken in cross-section including the axis.
[Figure 3] A diagram showing another example of a different thickness steel tube manufactured by the manufacturing method of the different thickness steel tube of the embodiment, a sectional view taken in cross-section including the axis.
[4] a process diagram illustrating the manufacturing method of the different thickness steel pipe which is a second embodiment of the present invention, is a cross-sectional view taken in cross-section including the axis of the base pipe.
[5] a process view showing a continuation of the manufacturing method of the different thickness steel pipe according to the embodiment, a sectional view taken in cross-section including the axis of the base pipe.
[6] A diagram showing a differential thickness steel tube manufactured by the manufacturing method of the different thickness steel pipe according to the embodiment, a sectional view taken in cross-section including the axis.
[7] a process diagram illustrating the manufacturing method of the different thickness steel pipe according to a third embodiment of the present invention, is a cross-sectional view taken in cross-section including the axis of the base pipe.
[8] a process diagram illustrating the manufacturing method of the different thickness steel pipe according to the fourth embodiment of the present invention, is a cross-sectional view taken in cross-section including the axis of the base pipe.
[Figure 9] A diagram showing a differential thickness steel tube manufactured by the manufacturing method of the different thickness steel pipe according to the embodiment, a sectional view taken in cross-section including the axis of the base pipe.
[10] a process diagram illustrating the manufacturing method of the different thickness steel pipe according to a fifth embodiment of the present invention, is a cross-sectional view taken in cross-section including the axis of the base pipe.
[Figure 11] A diagram showing an example of a different thickness steel tube manufactured by the manufacturing method of the different thickness steel pipe according to the embodiment, a sectional view taken in cross-section including the axis of the base pipe.
[Figure 12] A diagram showing another example of a different thickness steel tube manufactured by the manufacturing method of the different thickness steel pipe according to the embodiment, a sectional view taken in cross-section including the axis of the base pipe.
[13] a sixth step view for explaining a method for manufacturing differential thickness steel pipe according to the embodiment of the present invention, it is a cross-sectional view taken in cross-section including the axis of the base pipe.
[Figure 14] A diagram showing an example of a different thickness steel tube manufactured by the manufacturing method of the different thickness steel pipe according to the embodiment, a sectional view taken in cross-section including the axis of the base pipe.
[Figure 15] A diagram showing another example of a different thickness steel tube manufactured by the manufacturing method of the different thickness steel pipe according to the embodiment, a sectional view taken in cross-section including the axis of the base pipe.
[16] A seventh process diagram illustrating the manufacturing method of the different thickness steel pipe according to the embodiment of the present invention, is a cross-sectional view taken in cross-section including the axis of the base pipe.
[Figure 17] A eighth process diagram illustrating the manufacturing method of the different thickness steel pipe according to the embodiment of the present invention, is a cross-sectional view taken in cross-section including the axis of the base pipe.
[Figure 18] A diagram showing a differential thickness steel tube manufactured by the manufacturing method of the different thickness steel tube of the embodiment, a sectional view taken in cross-section including the axis of the base pipe.
19 is a schematic perspective view of a plug used in the production method of different thickness steel pipe according to the ninth embodiment of the present invention.
[Figure 20] A diagram showing respective examples of different thickness steel tube manufactured in the embodiment, a sectional view taken in cross-section perpendicular to the middle portion in the longitudinal direction.
DESCRIPTION OF THE INVENTION
[0017]
　Method for manufacturing differential thickness steel pipe and the different thickness steel tube according to embodiments of the present invention will be described below with reference to the drawings. Note that blank tube 1 which is used as raw material in each of the embodiments, tensile strength is preferably used or more of 290 MPa.
[0018]
First Embodiment
　manufacturing method of the different thickness steel pipe according to the first embodiment, using a die and a plug, forming a enlarged diameter portion performs pipe expanding on the one end side portion of the base pipe, to an intermediate portion at the other end side of the enlarged diameter portion has a step of performing ironing whose diameter increases the inner diameter while maintaining the outer diameter of the mother tube, the. Blank tube is a processing object in this embodiment, can be exemplified a hollow cylindrical metal tube, in particular round steel pipe is preferred. The round steel pipe, seamless steel, UO pipe, spiral pipe is applicable to any electric resistance welded steel pipe.
[0019]
　Next, a die and a plug to be used in the manufacturing method of this embodiment will be described with reference to FIG. 1 (a) ~ FIG 1 (c). Die 11 according to this embodiment includes a die body 11d. Within this die body 11d, the outer diameter d of the blank tube 1 1 and the hollow small-diameter portion 11a having an inner diameter corresponding to the outer diameter d of the blank tube 1 1 and the hollow large diameter part 11b having a larger inner diameter than the hollow and the tapered portion 11c provided between the small-diameter portion 11a and a hollow large diameter part 11b is formed. Hollow small-diameter portion 11a, the hollow large diameter portion 11b and the tapered portion 11c is communicated with each other in the die body 11d. The above "the outer diameter d of the base pipe 1 1 and an inner diameter which corresponds to" the outer diameter d of the blank tube 1 1 to the gap degree insertion and removal is possible mother tube 1 into the hollow small-diameter portion 11a and outside It shows the inner diameter plus dimensions.
[0020]
　Tapered portion 21c of the plug 21 in FIG. 1 (a) ~ FIG. 1 (c), when viewed in cross-section including the axis CL of the plug 21, the outer periphery forming the taper angle θ with respect to the line parallel to the axis CL It has a surface. The taper angle theta, is preferably in the range of 1 to 40 degrees. Since the taper angle θ is palatability increases to the entire plug 21 into base pipe 1 is less than 1 degree, the required processing power becomes excessive. On the other hand, the taper angle θ is 40 degrees greater than the local surface pressure becomes excessive occurring tapered portion 21c of the plug 21 when the thinning process, may cause a reduction of the service life of the plug 21.
[0021]
　Plug 21 according to this embodiment, the inner diameter d of the blank tube 1 2 and the small diameter distal portion 21a corresponding to the inner diameter d of the blank tube 1 2 diameters less than the inside diameter of the hollow small-diameter portion 11a of larger diameter and die 11 than It is composed of a large diameter end portion 21b, provided between the small-diameter tip portion 21a and the large diameter base end portion 21b and the tapered portion 21c having. The outer diameter of the large diameter base end portion 21b has an inner diameter d of the hollow small-diameter portion 11a of the die 11 1 is set to less than the size.
[0022]
　To produce the different thickness steel pipe according to the present embodiment, first, as shown in FIG. 1 (a), inserting the base tube 1 coaxially inside the die 11. At this time, one end portion 1a of the blank tube 1 aligned so as to position the hollow large diameter portion 11b of the die 11. Then, the state die 11 and blank tube 1 which is fixed, respectively. That is, in the die 11 is in a state of being fixed to a base (not shown). Further, in base tube 1, the end of the left side of the blank tube 1 has further been dammed up so as not advance deep into the left side, by this, the longitudinal direction of the relative positions of the blank tube 1 with respect to the die 11 is fixed ing.
　After the mother tube 1 is fixed to the die 11, from one end 1a side of the base pipe 1 toward the hollow portion 1b of the base tube 1, inserting the small diameter distal end portion 21a of the plug 21.
[0023]
　Next, as shown in FIG. 1 (b), a flare process, remain in a status of fixing the die 11 and base pipe 1, the tapered portion 21c and the large diameter base end portion 21b of the plug 21, base pipe 1 pushed into the end portion 1a. Plug 21 is pushed until the tapered portion 21c reaches the position of the tapered portion 11c of the die 11. Until the tapered portion 21c in this way to reach the position of the tapered portion 11c of the die 11, the blank tube 1 relative positions continue to be fixed with respect to the die 11, the die 11 base tube 1 by the taper portion 21c It never will be pushed out from.
　Incidentally, whether the taper portion 21c reaches the position of the tapered portion 11c, for example, pushing stroke of the plug 21, or it can be managed by measuring a reaction force to increase with push-in plug 21.
[0024]
　At the time of FIG. 1 (a), when placing the blank tube 1 inside the die 11, since the end portion 1a of the mother tube 1 is positioned within the hollow large diameter portion 11b of the die 11, the hollow of the die 11 gap s is formed between the large diameter portion 11b and one end portion 1a of the base pipe 1. Engaging plug 21 as shown in FIG. 1 (b) from this state, one end portion 1a of the mother tube 1 is expanded by the tapered portion 21c and the large diameter base end portion 21b of the plug 21. Thus, the gap s is gradually reduced and finally the outer peripheral surface of the one end portion 1a is brought into contact with the inner peripheral surface of the inner peripheral surface and a hollow large diameter part 11b of the tapered portion 11c of the die 11. In this way, the one end portion 1a of the base tube 1, and the enlarged diameter portion 1c of the straight pipe shape, and the locking portion 1e1 continuous with the enlarged diameter portion 1c is formed. Locking portion 1e1 form part of the intermediate portion 1e, and a tapered truncated cone shape with the outer peripheral surface of the tapered surface in close contact with the tapered portion 11c of the die 11.
　Incidentally, when forming the enlarged diameter portion 1c at one end 1a of the base tube 1, a slight tensile strain along the circumferential direction is applied.
[0025]
　Next, as shown in FIG. 1 (c), as ironing step, while the fixed die 11 is maintained, the stationary base pipe 1 in a state of being released, the plug 21 of the base pipe 1 and the other end portion 1d further pushed towards the side. That is, as shown in FIG. 1 (b), after the enlarged diameter portion 1c is formed releases the damming of the end of the left side of the base tube 1, then proceed with further pushing the plug 21. By further pushing the plug 21, although mother tube 1 is pushed toward the other end 1d side from one end 1a, said locking portion 1e1 formed blank tube 1 in the previous step, the tapered portion of the die 11 since remains locked to the 11c, mother tube 1 does not move.
[0026]
　By further pushing the plug 21, the large diameter base end portion 21b of the plug 21 is pushed toward the other end 1d side of the blank tube 1. In the intermediate portion 1e of the raw pipe 1 a large diameter base end portion 21b is pushed in the plug 21, the inner diameter d of the original raw material tube 1 2 expand to a size that corresponds to the diameter of the large diameter base end portion 21b of the plug 21 is the diameter. On the other hand, the intermediate portion 1e of the base pipe 1 because the outer diameter is restricted from the ambient located in the hollow small-diameter portion 11a of the die 11, the outer diameter d of intermediate portion 1e 1 is not enlarged. Accordingly, the intermediate portion 1e of the base pipe 1, the original outer diameter d of the blank tube 1 1 remains is maintained, subjected to ironing.
　The reason for releasing the damming of mother tube 1 immediately before the ironing starting is that it does not inhibit the flow of meat raw pipe 1 due to the ironing. That is, when the intermediate portion 1e of the mother tube 1 is thinning by ironing, in order to ensure the destination of the thinning amount of meat, and releases the damming of mother tube 1. Thus, the left side portion of the base pipe 1 is prevented from being buckled. In the present embodiment, since the thickness decrease amount of the mother tube 1 by ironing flows left side, the total length of the blank tube 1 is slightly longer than before processing.
[0027]
　To obtain the effect of improving the strength of the intermediate portion 1e due to ironing needs thinning rate of mother tube 1 by ironing is 10% or more. On the other hand, if the thinning rate of mother tube 1 by ironing exceeds 90%, there is a possibility that the breakage, seizure or the like is generated. Accordingly, thinning rate of mother tube 1 by ironing good in the range of 10-90%. Preferably the thinning rate preferably set to the range of 20-80%. Incidentally, thinning ratio (%) is the thickness of the front ironing raw tube 1 d 0 and the thickness of the intermediate portion 1e when the d after ironing, (d 0 -d) / d 0 × represented by 100 (%).
[0028]
　Here, the thickness d of the intermediate portion 1e after ironing is, when there is a distribution not uniform when viewed along the longitudinal direction of the mother tube 1, a numerical value obtained at the point most thinning amount is large adopted as the thinning rate. That is, in the intermediate portion 1e, d when viewed along its longitudinal direction 0 the value obtained in the largest position difference obtained by subtracting the d (corresponding strain amount) is employed as the thinning rate of the above . More say, when the thickness reduction in the circumferential direction of the mother tube 1 there is a distribution rather than uniform, the value determined at the point most thinning amount is large in the circumferential direction distribution, the above-mentioned adopted as the thinning rate.
　Note that thinning rate can be adjusted by varying the diameter of the large diameter base end portion 21b of the plug 21. Proper range of above about thinning rate in the ironing is also true in other embodiments described later.
[0029]
　In the example shown in FIG. 1 (c), the tapered portion 21c and the large diameter base end portion 21b of the plug 21 is pushed to a position in front of the other end portion 1d of the mother tube 1. When the Figure 1 stops the pushing of the plug 21 in the position shown (c), the other end 1d side portion than the middle portion 1e of the base pipe 1 remains unprocessed. Note that the portion of the referred to herein, "raw remains" in the different thickness steel pipe refers to a moiety having almost the same strength (tensile strength) or hardness to that of mother tube 1 prior to processing a base material.
[0030]
　Figure 2 shows a schematic cross section of a different thickness steel tube 31 which is manufactured through the steps shown in FIG. 1 (a) ~ FIG 1 (c). In the following description, in order to be distinguished from the different thickness steel tube after manufacture and mother tube 1 before and during processing process, assign 31 as a new sign. Similarly, for each unit constituting the differential thickness steel tube 31, but the description will be continued by applying a new sign, respectively, in order to specify a correspondence relationship between each part constituting the base tube 1, in brackets, If also shown the units of sign at the time of mother tube 1 there. This also applies to the other embodiments described below.
[0031]
　Different thickness steel tube 31 shown in FIG. 2, one end portion 31a (1a) is expanded from raw pipe 1 In the side the enlarged diameter portion 31c (1c), the one end portion 31a and the other end portion 31d (1d) an intermediate portion 31e (1e) that received in time by ironing, not receiving processing remains blank pipe 1 in the other end portion 31d side of the intermediate portion 31e composed of a raw portion 31f. The intermediate portion 31e is enlarged diameter portion 31c and the tapered portion 11c of the die 11 and the plug 21 in each of the boundary between the unprocessed portion 31f, also includes a portion receiving the processed by 21c. That is, the intermediate portion 31e, when viewed towards the other end portion 31d from one end 31a, and the engaging portion 31e1 of the inner diameter is the outer diameter of the tapered constant (1e1), constant both inner and outer diameter straight a tube portion 31e2, and includes a tapered portion 31e3 having an outer diameter inner diameter constant tapering, the. Then, the average value of the hardness of the enlarged diameter portion 31c H1, the average value of the hardness of the unprocessed portion 31f H3, the average value H4, the hardness of the engaging portion 31e1, the average value of the hardness of the straight pipe portion 31e2 H5, If the average value of the hardness of the tapered portion 31e3 was H6, satisfy both equations of H5> H6 ≧ H3 and H5> H4> H1.
　In FIG 2, the enlarged diameter portion 31c are illustrated as short ring-shaped, may be straight tube shape long as necessary for the explanation. Similar diameter section 41c in the other embodiments described below, the enlarged diameter portion 61c, the enlarged diameter portion 91c, the enlarged diameter portion 111c, 111f, enlarged diameter portion 121c, the enlarged diameter portion 141c, the enlarged diameter portion 151c, for each of even is there.
[0032]
　Hollow portion 31b of the different thickness steel tube 31, at the enlarged diameter portion 31c and the intermediate portion 31e of the original mother tube 1 inner diameter d 2 is diameter than the unprocessed portion of 31f in the original mother tube 1 inside diameter d 2 of It has become a remain. The outer diameter of the different thickness steel tube 31 has an outer diameter d of the blank tube 1 at the engaging portion 31e1 1 is gradually enlarged from, and in the enlarged diameter portion 31c the outside diameter d of the blank tube 1 1 diameter than It is constant remains. On the other hand, a portion except for the engaging portion 31e1 among the intermediate portions 31e, the unprocessed portion 31f has an outer diameter d of the blank tube 1 1 stuck in the outer diameter equal to. Thus, the thickness of the enlarged diameter portion 31c and the unprocessed portion 31f is relatively thick, the thickness of the intermediate portion 31e is relatively thin, and has a different thickness steel tube 31.
[0033]
　In different thickness steel tube 31 shown in FIG. 2, since the processing amount for the enlarged diameter portion 31c and the unprocessed portion 31f is small, or work hardening does not occur in this portion, it is also very little, have occurred. Thus, the relatively low strength of the enlarged diameter portion 31c and the unprocessed portion 31f, bending even when performing post-processing process or the like, unnecessary annealing treatment or the like for relieving work-hardening for these parts become.
[0034]
　Further, since the processing amount with respect to a large middle portion 31e of the different thickness steel pipe 31, intermediate portion 31e strength by work hardening is relatively high. In other words, the hardness distribution (Vickers hardness distribution. Instead of Vickers hardness distribution, tensile also determinable by the intensity distribution) along the longitudinal direction of the different thickness steel tube 31 when viewed, the lowest hardness of the unprocessed portion 31f , slightly higher than the hardness of the hardness of the enlarged diameter portion 31c is unprocessed portion 31f, and the hardness of the intermediate portion 31e is higher than the hardness of the enlarged diameter portion 31c. Therefore, since the intermediate portion 31e has the highest hardness, it is suitable as a site required a high mechanical strength. Further, the unprocessed portion 31f and the enlarged diameter portion 31c having a relatively low hardness is preferable as a portion required for post-processing such as bending.
　Further, the inner surface of the intermediate portion 31e, the surface roughness is reduced by receiving the ironing. Since surface roughness is the fatigue characteristics is improved small, intermediate portion 31e, in addition to the improvement of strength by work hardening, so also obtained fatigue properties improve due to the reduced surface roughness of the inner surface, while being lightweight high strength It is realized. Such synergy is not obtained by thinning by simply cutting.
[0035]
　Further, FIG. 3 shows another example of FIG. 1 (a) ~ the different thickness steel pipe process is manufactured through the shown in Figure 1 (c). Different thickness steel tube 41 shown in FIG. 3, in the step shown in FIG. 1 (c), the large diameter base end portion 21b of the plug 21 is manufactured by pressing the plug 21 up to the other end portion 1d of the raw pipe 1 it is a different thickness steel pipe.
[0036]
　Different thickness steel tube 41 shown in FIG. 3, one end portion 41a enlarged diameter portion is expanded from raw pipe 1 In the side 41c (1c), one end portion 41a and (1a) and the other end 41d (1d) an intermediate portion 41e (1e) that received in time and ironing, and be in the other end portion 41d side of the intermediate portion 41e and an intermediate portion 41e and second end portion 41f which receives the ironing as well. Intermediate portion 41e, in the boundary between the enlarged diameter portion 41c, also includes a portion receiving the working by the tapered portion 21c of the tapered portion 11c and the plug 21 of the die 11. That is, the intermediate portion 41e includes locking portions 41e1 a (1e1). Engaging portion 41e1 is because it has the same shape as the engaging portion 31e1, here the explanation thereof will be eliminated.
[0037]
　Hollow portion 41b of the different thickness steel tube 41, the entire inner diameter of the longitudinal inner diameter d of the blank tube 1 2 is enlarged than. The outer diameter of the different thickness steel tube 41 has an outer diameter d of the blank tube 1 at the engaging portion 41e1 1 is gradually enlarged from, and in the enlarged diameter portion 41c the outside diameter d of the blank tube 1 1 diameter than It is constant remains. On the other hand, a portion except for the engaging portion 41e1 among the intermediate portions 41e, and the other end portion 41f, the outer diameter d of the blank tube 1 1 stuck in the outer diameter equal to. Thus, the thickness of the engaging portion 41e1 and the enlarged diameter portion 41c is relatively thick, the portion excluding the engaging portion 41e1 of the intermediate portion 41e, the wall thickness at the other end portion 41f relatively thin different thickness It has become a steel pipe 41.
[0038]
　In different thickness steel tube 41 shown in FIG. 3, since the processing amount for the enlarged diameter portion 41c is small, or work hardening does not occur in this portion, it is also very little, have occurred. Accordingly, the strength is relatively low in the enlarged diameter portion 41c, even when performing machining after machining such as bending for this part, such annealing for relieving work hardening is not required.
[0039]
　Further, since the processing amount with respect to a large middle portion 41e and the other end portion 41f of the different thickness steel pipe 41, intermediate portion 41e and the other end portion 41f strength by work hardening is relatively high.
[0040]
　As described above, in the embodiment shown in FIG. 1 (a) ~ FIG. 2, the locking portions 1e1 and enlarged diameter portion 1c provided by performing a pipe expanding the end portion 1a of the base tube 1, the locking portion 1e1 the by pushing further mother tube 1 while the plug 21 is engaged in the die 11, the intermediate portion 1e at the other end portion 1d side of the enlarged diameter portion 1c of the base tube 1, the raw pipe 1 since the ironing whose diameter increases the inner diameter while maintaining an outer diameter, requires less processing amount for the enlarged diameter portion 1c, a heat treatment of annealing or the like when performing processing after processing such as bending respect enlarged diameter portion 1c the can be made unnecessary.
　Further, since the left plug 21 and the enlarged diameter portion 1c to engage with the die 11 performs the ironing push the base tube 1, without the need for labor and the jig for fixing the base tube 1 itself, the die 11 and the plug 21 can be carried out only by ironing moved relative.
[0041]
　In addition, by the other end 1d side of the portion of the base pipe 1 and the raw remain unprocessed portion 31f than the intermediate portion 1e, the processing amount becomes zero for the portion of the other end 1d side, unprocessed portion 31f It can be made unnecessary heat treatment annealing or the like when performing processing after bending or the like on.
[0042]
　Also, different thickness steel tube 31 produced by the above method, since the processing amount of the enlarged diameter portion 31c and the unprocessed portion 31f is small, the wall thickness is thick and strength is relatively low. Meanwhile, since the processing amount in the intermediate portion 31e is large, the thickness is thin and the strength is relatively high. Thus, the enlarged diameter portion 31c and the unprocessed portion 31f is in a state deformability than the intermediate portion 31e remained have become different thickness steel tube 31 which is excellent in workability after working such as bending of these parts. The intermediate portion 31e is because the smaller the inner surface roughness by receiving the ironing working, and has a different thickness steel tube 31 this portion is excellent in fatigue characteristics.
[0043]
[Second Embodiment]
　method of manufacturing differential thickness steel pipe of the second embodiment, using a die and a plug, forming a enlarged diameter portion performs pipe expanding on the one end side portion of the base pipe, the plug the after replaced with another plug, to an intermediate portion at the other end side of the enlarged diameter portion, and performing ironing whose diameter increases the inner diameter while maintaining the outer diameter of the mother tube, consists there. Blank tube is a processing object of this embodiment may be similar to the first embodiment.
[0044]
　In the present embodiment, a die and a plug for use in the formation process of the first expanded diameter section may be used the same first embodiment.
　That is, as in the first embodiment, as shown in FIG. 4 (a), the base tube 1 is inserted into the die 11, one end portion 1a of the base pipe 1 into a hollow large diameter portion 11b of the die 11 There is positioned so as to be located. Die 11 and blank pipe 1 so as to be brought into fixed respectively. Then, the hollow portion 1b of the base pipe 1 from one end 1a side of the base tube 1, inserting the small diameter distal end portion 21a of the plug 21.
[0045]
　Next, as shown in FIG. 4 (b), a flare process, remain in a status of fixing the die 11 and base pipe 1, the tapered portion 21c and the large diameter base end portion 21b of the plug 21, base pipe 1 pushed into the end portion 1a. Plug 21 is pushed until the tapered portion 21c reaches the position of the tapered portion 11c of the die 11. Thus, as in the first embodiment, one end portion 1a of the base tube 1, the locking portion 1e1 and the enlarged diameter portion 1c is formed.
[0046]
　Next, as shown in FIG. 4 (c), pulling out the plug 21 is pushed, the blank tube 1 in order to replace it with another plug. On the other hand, the die 11 is used continuously until the end without exchange.
[0047]
　Next, as shown in FIG. 5 (a), providing a separate plug 51. This another plug 51, the inside diameter d of the blank tube 1 2 and the small-diameter tip portion 51a corresponding to the inner diameter d of the blank tube 1 2 and diameter portion 51b in which has a larger diameter than the outer diameter or small-diameter tip portion 51a, a large diameter end portion 51c having a larger diameter than the intermediate-diameter portion 51b in diameter, and a first tapered portion 51d which is provided between the intermediate diameter portion 51b and a small-diameter tip portion 51a, the intermediate-diameter portion 51b and the large-diameter and a, a second tapered portion 51e provided between the base end portion 51c. The diameter of the large diameter base end portion 51c has an inner diameter d of the hollow small-diameter portion 11a of the die 11 1 is set to less than the size. The diameter of the small-diameter tip portion 51a of the plug 51 is the same size as the diameter of the small diameter distal end portion 21a of the plug 21 previously used.
[0048]
　Then, as shown in FIG. 5 (b), as the ironing process, while maintaining a fixed die 11, the stationary base pipe 1 in a state of being released, the other plug 51 from one end 1a of the base pipe 1 pushed towards the end 1d. By pushing the plug 51, although mother tube 1 is pushed toward the other end 1d side from one end 1a, the front locking portion 1e1 formed blank tube 1 in the process, the taper portion 11c of the die 11 It does not move because it is remains locked in. In the present embodiment, pushing the plug 51 to the tip of the small-diameter tip portion 51a protrudes from the other end 1d of the mother tube 1.
[0049]
　By pushing the plug 51 to the position shown in FIG. 5 (b), diameter 51b and the large diameter base end portion 51c in the plug 51 is pushed into the intermediate portion 1e of the base pipe 1. In the intermediate portion 1e of the base tube 1, the inner diameter d of the original raw material tube 1 2 is enlarged in size corresponding to the diameter of the diameter portion 51b and large diameter end portion 51c in the plug 51. On the other hand, the intermediate portion 1e of the base pipe 1 because it has located in the hollow small-diameter portion 11a of the die 11, the outer diameter d of the intermediate portion 1e 1 is not enlarged. Accordingly, the intermediate portion 1e of the base pipe 1, except for the portion of the locking portion 1e1, original outer diameter d of the blank tube 1 1 remains is maintained, subjected to ironing.
[0050]
　Further, as shown in FIG. 5 (b), the other end 1d side portion than the middle portion 1e of the base pipe 1 is only small diameter tip 51a is inserted and remains raw.
[0051]
　Figure 6 shows a schematic cross section of FIG. 4 (a) ~ FIG 5 (b) is produced through the indicated step in the different thickness steel tube 61. Different thickness steel tube 61 shown in FIG. 6, one end portion 61a enlarged diameter portion is expanded from raw pipe 1 In the side 61c (1c), one end portion 61a and (1a) and the other end 61d (1d) an intermediate portion 61e (1e) that received in time by ironing, not receiving processing remains blank pipe 1 in the other end portion 61d side of the intermediate portion 61e composed of a raw portion 61f. Intermediate portion 61e, at each boundary between the enlarged diameter portion 61c and the unprocessed portion 61f, also includes a portion receiving the working taper portion 51d, by the 51e of the tapered portion 11c and the plug 51 of the die 11. That is, the intermediate portion 61e includes locking portions 61e1 a (1e1). Since the engaging portion 61e1 has the same shape as the engaging portion 31e1, here the explanation thereof will be eliminated.
[0052]
　The inner diameter of the hollow portion 61b of the different thickness steel tube 61 has an inner diameter d of the blank tube 1 in the enlarged diameter portion 61c and the intermediate portion 61e 2 are diameter larger than, and in the unprocessed portion 61f the inner diameter d of the blank tube 1 2 of It has become a remain. Further, of the intermediate portion 61e, the portion of the one end 61a side inside diameter is expanded by the large diameter end portion 51c of the plug 51, the inner diameter by diameter portion 51b in the portion of the other end portion 61d side plug 51 expand are diameter, yet it has different inner diameter from each other. The outer diameter of the different thickness steel tube 61 has an outer diameter d of the blank tube 1 at the engaging portion 61e1 and the enlarged diameter portion 61c 1 is diameter than. On the other hand, a portion except for the engaging portion 61e1 of the intermediate portion 61e, the outer diameter of the unprocessed portion 61f has an outer diameter d of the blank tube 1 1 stuck in the. Thus, the thickness of the enlarged diameter portion 61c and the unprocessed portion 61f is relatively thick, the thickness of the intermediate portion 61e is in the relatively thin different thickness steel tube 61.
[0053]
　In different thickness steel tube 61 shown in FIG. 6, since the processing amount for the enlarged diameter portion 61c and the unprocessed portion 61f is small, or work hardening does not occur in this portion, it is also very little, have occurred. Thus, the enlarged diameter portion 61c or relatively low strength of the unprocessed portion 61f, bending even when performing post-processing process or the like, unnecessary annealing treatment or the like for relieving work-hardening for these parts become.
[0054]
　Further, since a relatively large amount of machining the intermediate portions 61e of the different thickness steel pipe 61, intermediate portion 61e is relatively strength is increased by work hardening.
[0055]
　In the present embodiment, as described above, it performs ironed the intermediate portion 1e of the base pipe 1 by the plug 51. At that time, of the intermediate portion 1e, the diameter of the enlarged diameter portion 1c side of the area to be larger than the diameter of the region of the other end portion 1d side, inner and strength in the intermediate portion 1e is different 2 One area can be provided.
[0056]
　Also, more than different thickness steel tube 61 produced by the process, in the intermediate portion 61e, diameter of the area of ​​the enlarged diameter portion 61c side is larger than the diameter of the region of the other end portion 61d side, the enlarged diameter portion 61c machining amount of the side region is larger than the processing amount in the region of the other end portion 61d side. Therefore, thick and strength in the intermediate portion 61e is in the different thickness steel tube 61 having a different area, respectively.
[0057]
[Third Embodiment]
　A method for manufacturing a different thickness steel tube of the third embodiment will be described with reference to FIG. 7 (a) ~ FIG 7 (c). Method for manufacturing differential thickness steel pipe of the present embodiment is constituted by the same process as that of the first embodiment. In the present embodiment, the production of different thickness steel tube with another plug 71 and the plug 21 used in the first embodiment. Since other points are the same as in the first embodiment, the description thereof is omitted.
[0058]
　Plug 71 used in this embodiment, as shown in FIG. 7 (a), the inner diameter d of the blank tube 1 2 and the taper end portion 71c having a smaller distal end portion 71a than the inner diameter d of the blank tube 1 2 greater than and a proximal end 71b having a diameter, and a. The diameter of the base end portion 71b has an inner diameter d of the hollow small-diameter portion 11a of the die 11 1 is set to less than the size.
[0059]
　In the present embodiment, as in the first embodiment, as shown in FIG. 7 (b), a flare process, it remains in a status of fixing the die 11 and base pipe 1, the tapered tip portion 71c and the plug 71 a proximal end 71b, pushed to one end 1a of the blank tube 1. Plug 71 is pushed until the tapered tip portion 71c reaches the position of the tapered portion 11c of the die 11. Thus, the one end portion 1a of the base tube 1, the locking portion 1e1 and the enlarged diameter portion 1c is formed.
[0060]
　Next, as shown in FIG. 7 (c), as ironing step, while the fixed die 11 is maintained, the stationary base pipe 1 in a state of being released, the plug 71 of the base pipe 1 and the other end portion 1d further pushed towards the side. By further pushing the plug 71, although mother tube 1 is pushed toward the other end 1d side from one end 1a, the front locking portion 1e1 formed blank tube 1 in the process, the tapered portion of the die 11 It does not work because the remains locked to the 11c.
[0061]
　Plug 71 in this embodiment, the taper end portion 71c, which is composed of a proximal portion 71b, since there is no small-diameter tip portion 21a shown in the first embodiment, relatively, the longitudinal length It is shorter. Therefore, in comparison with the first embodiment, and when inserting the plug 71 into base pipe 1, when pulling out the plug 71 from the base pipe 1, the required stroke of the plug 71 is shortened. As a result, on which can shorten the working time required for insertion and removal of the plug 71, because it can adopt a simple as a hydraulic cylinder (not shown) for connecting or disconnecting the plug 71, it can be processed at relatively small production facility.
[0062]
　Different thickness steel pipe manufactured through the steps shown in FIG. 7 (a) ~ FIG. 7 (c), the same shape as the different thickness steel tube 31 shown in FIG. Further, in the step shown in FIG. 7 (c), by pressing the plug 71 to the proximal end portion 71b of the plug 71 reaches the other end portion 1d of the base pipe 1, the same shape as the different thickness steel tube 41 shown in FIG. 3 it may be processed into.
[0063]
　In the above embodiment, as described, by performing the production of the different thickness steel pipe using the longitudinal length is relatively short plug 71, as compared with the first embodiment, the plug 71 at the time of manufacture it can be relatively small required stroke.
[0064]
[Fourth Embodiment]
　Next, a method for manufacturing a different thickness steel tube of the fourth embodiment. Method for manufacturing differential thickness steel pipe of the present embodiment is constituted by the same process as the second embodiment. In this embodiment, the plug 51 used in the ironing step of the second embodiment using another plug 81 performs the ironing. Since other points are the same as in the second embodiment, the description thereof is omitted.
[0065]
　First, in the present embodiment, as in the second embodiment, to form the locking portions 1e1 and enlarged diameter portion 1c base tube 1. Next, as shown in FIG. 8 (a), providing a separate plug 81 from the previous step. Plug 81 has an inner diameter d of the blank tube 1 2 and the taper end portion 81c having a smaller distal end portion 81a than the inner diameter d of the blank tube 1 2 hollow small-diameter portion 11a of larger diameter and die 11 than the inner diameter d 1 of less than and a proximal end 81b having a diameter, and a. Taper end portion 81c of the plug 81 is longer than the length of the taper end portion 71c of the plug 71 shown in Figure 7 (a).
[0066]
　Then, the other as shown in FIG. 8 (b), as the ironing process, while maintaining a fixed die 11, the stationary base pipe 1 in a state of being released, the plug 81 from one end 1a of the base pipe 1 pushed towards the end 1d. By pushing the plug 81, although mother tube 1 is pushed toward the other end 1d side from one end 1a, the front locking portion 1e1 formed blank tube 1 in the process, the taper portion 11c of the die 11 since the remains were locked in, the hollow shell 1 does not move. In the present embodiment, pushing the plug 81 to the tip portion 81a of the plug 81 projects from the other end 1d of the mother tube 1.
[0067]
　By pushing the plug 81 to the position shown in FIG. 8 (b), the taper end portion 81c of the plug 81 is pushed into the intermediate portion 1e of the base pipe 1. In the intermediate portion 1e of the base tube 1, the inner diameter d of the original raw material tube 1 2 is expanded to a size corresponding to the diameter of the taper end portion 81c of the plug 81.
[0068]
　Plug 81 used in this embodiment, since the taper length of the taper end portion 81c is relatively long, inner diameter of the intermediate portion 1e of the base pipe 1 is the same as the outer diameter of the taper end portion 81c of the plug 81 over the entire length . That is, the inner diameter of the intermediate portion 1e of the base pipe 1 is progressively enlarged toward the one end portion 1a side from the other end 1d side.
[0069]
　FIG 9 shows a schematic cross section of a different thickness steel pipe manufactured by this embodiment. Different thickness steel tube 91 shown in FIG. 9, one end portion 91a (1a) is expanded from raw pipe 1 In the side the enlarged diameter portion 91c (1c), the one end portion 91a and the other end portion 91d (1d) and in time by squeezing an intermediate portion 91e which has received the processing (1e), not subject to processing remain blank pipe 1 in the other end portion 91d side of the intermediate portion 91e composed of a raw portion 91f.
[0070]
　The inner diameter of the hollow portion 91b of the different thickness steel tube 91 has an inner diameter d of the blank tube 1 in the enlarged diameter portion 91c and the intermediate portion 91e 2 are diameter larger than, the inner diameter d of the unprocessed portion 91f in raw material tube 1 2 and remains going on. The outer diameter of the different thickness steel tube 91 has an outer diameter d of the blank tube 1 at the engaging portion 91e1 and the enlarged diameter portion 91c 1 is diameter than a portion except for the engaging portion 91e1 among the intermediate portions 91e, the unprocessed portion 91f, the outer diameter d of the blank tube 1 1 stuck in the. The inner diameter of the intermediate portion 91e is progressively increased toward the one end portion 1a side from the other end 1d side. Thus, the thickness of the enlarged diameter portion 91c and the unprocessed portion 91f is relatively thick. Also, when viewing the thickness of the intermediate portion 91e from the enlarged diameter portion 91c toward the unprocessed portion 91f, progressively thinner the locking portion 91E1, and progressively thicker in a portion other than the engaging portion 91E1 ing.
[0071]
　In different thickness steel tube 91 shown in FIG. 9, since the processing amount for the enlarged diameter portion 91c and the unprocessed portion 91f is small, or work hardening does not occur in this portion, it is also very little, have occurred.
[0072]
　In the middle portion 91e of the different thickness steel tube 91, so slowly machining amount toward unprocessed portion 91f from the enlarged diameter portion 91c is smaller, relatively high hardness at the enlarged diameter portion 91c of the intermediate portion 91e, in the unprocessed portion 91f side thereof hardness relatively low.
[0073]
　In the above embodiment, as described, using a plug 81 which has a relatively long tapered tip 81c, performs ironing at an intermediate portion 1e of the base pipe 1. Therefore, in the intermediate portion 1e, the inner diameter of the enlarged diameter portion 1c side to the other end 1d side can be produced progressively smaller difference thick steel.
[0074]
[Fifth Embodiment]
　method of manufacturing differential thickness steel tube of the fifth embodiment, one die and two with a plug, enlarged diameter portion 1c performs pipe expanding to both ends of the blank tube 1, 1f forming a one end of the plug 21 remains the other end inserted into the mother tube 1 plug 22 vent, to an intermediate portion 1g at the other end side than the one end side of the enlarged diameter portion 1c, base pipe 1 of a first step of performing ironing whose diameter increases the inner diameter while maintaining an outer diameter, disconnect the one end side of the plug 21 from the base pipe 1, the other end of the plug 22 is inserted into base pipe 1, the other end to an intermediate portion 1h on the one end side than the side of the enlarged diameter portion 1f, and performing a second ironing whose diameter increases the inner diameter while maintaining the outer diameter of the mother tube 1, and a. Mother tube 1 is a processing object of this embodiment may be similar to the first embodiment.
[0075]
　In the present embodiment, a die 12 shown in Figure 10 (a). Die 12, the outer diameter d of the blank tube 1 1 and the hollow small-diameter portion 12b having an inner diameter corresponding to, provided on both sides in the longitudinal direction of the hollow small-diameter portion 12b, the outer diameter d of the blank tube 1 1 having an inner diameter larger than hollow diameter portion 12a and a hollow large diameter portion 12d, and a. Further, the tapered portion 12c is provided between the hollow small-diameter portion 12b and a hollow large diameter portion 12a, the tapered portion 12e is provided between the hollow small-diameter portion 12b and a hollow large diameter portion 12d. The hollow larger-diameter portion 12a, the tapered portion 12c, a hollow small-diameter portion 12b, a tapered portion 12e, and a hollow large diameter portion 12d are communicated with each other in the die body 12f. Further, the die 12 has a two-piece structure dividable in a vertical direction in FIG. 10 (a).
　Note that dashed lines in the vertical in FIG. 10 (a) ~ FIG 10 (d) is a center line shows a longitudinal half length of the die 12, the die 12 the one-dot chain line axis of symmetry and it has a line-symmetric shape.
[0076]
　Plug 21 shown in FIG. 10 (a) is the same as those used in the first embodiment, its description is omitted with the same reference numerals. Plug 22 has the same shape as the plug 21, the inner diameter d of the blank tube 1 2 and the small diameter distal end portion 22a corresponding to the inner diameter d of the blank tube 1 2 and the large diameter base end portion 22b having a larger diameter than the , and a tapered portion 22c provided between the small-diameter tip portion 22a and the large diameter base end portion 22b. The diameter of the large diameter base end portion 22b has an inner diameter d of the hollow small-diameter portion 12b of the die 12 1 is set to less than the size.
[0077]
　To produce the different thickness steel pipe according to the present embodiment, first, as shown in FIG. 10 (a), inserting the base tube 1 in the interior of the die 12. At this time, the hollow large diameter portion 12a of the die 12, one end portion 1a of the base pipe 1 to 12d, the other end 1d is positioned so as to be located respectively. Then, from one end 1a side and the other end 1d side of the base pipe 1 into the hollow portion 1b of the base pipe 1, inserting the small diameter distal end portion 22a of the small diameter distal end portion 21a and the plug 22 of the plug 21. At this time, blank pipe 1 and the die 12 is a state that is not fixed.
[0078]
　Next, a flare step, as shown in FIG. 10 (b), the tapered portion 21c and the large diameter base end portion 21b of the plug 21 at one end 1a of the base tube 1, the tapered portion 22c and the large diameter of the plug 22 the base end portion 22b at the other end 1d of the base tube 1, pressed respectively at the same time. Moreover, the plug 21 is pushed until the tapered portion 21c reaches the position of the tapered portion 12c of the die 12, the plug 22 is pushed until the tapered portion 22c reaches the position of the tapered portion 12e of the die 12. Thus, the locking portion 1g1 and enlarged diameter portion 1c is formed at one end 1a side of the base tube 1, also, the locking portion 1h1 and the enlarged diameter portion 1f is formed on the other end 1d side.
[0079]
　Then, leaving one end portion 1a side of the plug 21, pulling the other end 1d side of the plug 22 from the base pipe 1. Thereafter, as shown in FIG. 10 (c), as the first ironing process, while fixing the other end portion 12g side of the die 12, the fixed base pipe 1 will remain released, mother tube 1 a plug 21 further pushed toward the other end 1d side. By further pushing the plug 21, although mother tube 1 is pushed toward the other end 1d side from one end 1a, the front locking portion 1g1 formed blank tube 1 in the process, the tapered portion of the die 12 because will remain engaged in 12c, the hollow shell 1 does not move.
[0080]
　In the example shown in FIG. 10 (c), the tapered portion 21c and the large diameter base end portion 21b of the plug 21 is pushed to the position of the one end portion 12h side of the middle position of the die 12. When stopping the pushing of the plug 21 in the position shown in the FIG. 10 (c), the first processing portion 1g, which has received the enlarged diameter portion 1f of the other end portion 1d side of the base tube 1, the ironing of mother tube 1 the portion between the remains raw.
[0081]
　Then, pull the plug 21 from the base pipe 1, inserting the plug 22 at the other end 1d side of the blank tube 1. Then, as shown in FIG. 10 (d), a second ironing step, the plug 22 is further pushed toward the one end portion 1a side of the base pipe 1. At this time, while fixing one end portion 12h side of the die, blank pipe 1 is in a state not fixed. By further pushing the plug 22, although mother tube 1 is pushed toward the one end portion 1a side from the other end 1d side, the engaging portion 1h1 which had been formed in advance mother tube 1 in the diameter expansion step, since locked in the tapered portion 12e of the die 12, blank pipe 1 does not move.
[0082]
　In the example shown in FIG. 10 (d), the tapered portion 22c and the large diameter base end portion 22b of the plug 22 is pushed from the middle of the die 12 to the position of the other end 12g side. When stopping the pushing of the plug 22 in the position shown in the FIG. 10 (d), the intermediate portion 1i between the first working portion 1g and the second processing portion 1h of the base pipe 1 remains unprocessed.
[0083]
　Figure 11 shows a schematic cross section of FIG. 10 (a) ~ FIG 10 different thickness steel tube 111 manufactured through the steps shown in (d). The differential thickness steel tube 111, first there between one end portion 111a (1a) side there are enlarged diameter portion 111c which is expanded from raw pipe 1 (1c), one end portion 111a and the other end portion 111d (1d) 1 of the first processing portion 111g which receives the ironing (1 g), and the other end portion 111d enlarged diameter portion which is enlarged from the base pipe 1 in the side 111f (1f), the other end portion 111d and the end portion 111a the second working portion 111h and (1h), the unprocessed portion not subjected to processing remain blank pipe 1 there between the first working portion 111g and the second processing section 111h which receives the second ironing there between 111i and (1i), composed of.
　The first working portion 111g is at the boundary between each of the enlarged diameter portion 111c and the unprocessed portion 111i, the tapered portion 12c of the die 12 and the plug 21 also includes a portion which has received the processing by 21c. That is, the first processing portion 111g includes a locking portion 111g1 connecting to the enlarged diameter portion 111c (1 g 1), and a tapered portion 111g2 continuing to unprocessed portion 111i.
　The second working portion 111h, in the boundary between each of the enlarged diameter portion 111f and the unprocessed portion 111i, the tapered portion 12c of the die 12 and the plug 22 also includes a portion which has received the processing by 22c. That is, the second working portion 111h includes a locking portion 111h1 connecting to the enlarged diameter portion 111f (1h1), and a tapered portion 111h2 continuing to unprocessed portion 111i.
[0084]
　Hollow portion 111b of the different thickness steel tube 111 has a diameter portion 111c, and a first working portion 111 g, and the enlarged diameter portion 111f, a second working portion 111h, the inner diameter d of the original raw material tube 1 in 2 than diameter It is. On the other hand, in the unprocessed portion 111i, an inner diameter d of the original raw material tube 1 2 stuck in the. The outer diameter of the different thickness steel tube 111 has a diameter portion 111c, a locking portion 111G1, and the enlarged diameter portion 111f, and the locking portion 111H1, the outer diameter d of the blank tube 1 in 1 is diameter than there. On the other hand, a portion except for the engaging portion 111g1 of the first working portion 111 g, a portion except for the engaging portion 111h1 of the second working portion 111h, the unprocessed portion 111i, the outer diameter d of the blank tube 1 1 and has a left.
[0085]
　Regarding the thickness, the thickness of the enlarged diameter portion 111c, the enlarged diameter portion 111f and the unprocessed portion 111i is relatively thick, the thickness of the first working portion 111g and the second processing section 111h is relatively thin different thickness steel tube It has become.
[0086]
　In different thickness steel tube 111 shown in Figure 11, enlarged diameter portion 111c, so the processing amount for the enlarged diameter portion 111f and the unprocessed portion 111i is small, or work hardening does not occur in this portion, even negligible as had occurred it is. Thus, the enlarged diameter portion 111c, since the enlarged diameter portion 111f or unprocessed portion 111i has a relatively low strength, even when performing machining after machining such as bending for this part, for relieving work hardening annealing process or the like is not required.
[0087]
　Further, since the processing amount for the first machining portion 111g and the second processing section 111h is relatively large, the first processing portion 111g and the second processing section 111h is relatively strength is increased by work hardening.
[0088]
　Figure 12 shows another example of FIG. 10 (a) ~ FIG 10 (d) are manufactured through the indicated step in the different thickness steel tube. Different thickness steel tube 121 shown in FIG. 12, in the step shown in FIG. 10 (d), a difference that the large diameter base end portion 22b of the plug 22 is manufactured by pressing the plug 22 up to the end portion 1a of the base pipe 1 it is a thick steel pipe.
[0089]
　Different thickness steel tube 121 shown in Figure 12, expansion of base pipe 1 and the end portion 121a is enlarged from raw pipe 1 In the side enlarged diameter portion 121c (1c), In the other end portion 121d (1d) side the diameter has been enlarged diameter portion 121f (1c), an intermediate portion 121e (1e) which receives the matching ironed between one end portion 121a and the other end portion 121d, composed. Intermediate portion 121e includes a portion receiving the working by the tapered portion 21c of the tapered portion 12c and the plug 21 of the die 12 at the boundary between the enlarged diameter portion 121c, and the tapered portion 12e of the die 12 at the boundary between the enlarged diameter portion 121f and it includes a portion which has received the processing, the by the tapered portion 22c of the plug 22. That is, the intermediate portion 121e includes a locking portion 121e1 connecting to the enlarged diameter portion 121c (1 g 1), the locking portion 122e2 (1h1) leading to the enlarged diameter portion 121f and contains.
[0090]
　Hollow portion 121b of the different thickness steel tube 121, the entirety of the inner diameter of the longitudinal inner diameter d of the blank tube 1 2 is enlarged than. The outer diameter of the different thickness steel tube 121 has a diameter portion 121c, a locking portion 121e1,121e2 at both ends of the intermediate portion 121e, the enlarged diameter portion 121f, the outer diameter d of the blank tube 1 1 than It has been expanded. Moreover, the portion excluding the engaging portion 121e1,121e2 than the intermediate portion 121e, the outside diameter d of the blank tube 1 1 stuck in the. Thus, the thickness of the enlarged diameter portion 121c and the enlarged diameter portion 121f is relatively thick, the thickness of the intermediate portion 41e is in a relatively thin different thickness steel tube 121.
[0091]
　In different thickness steel tube 121 shown in FIG. 12, since the processing amount for the enlarged diameter portion 121c and the enlarged diameter portion 121f is small, or work hardening does not occur in this portion, it is also very little, have occurred. Therefore, even when performing machining after machining such as bending against the enlarged diameter portion 121c or the enlarged diameter portion 121f, such annealing for relieving work hardening is not required.
[0092]
　Further, since the processing amount in the intermediate portion 121e is relatively large, the intermediate portion 121e is relatively strength is increased by work hardening.
[0093]
　As described above, in the embodiment shown in FIG. 10 (a) ~ 11, to produce a different thickness steel tube 111 using one die 12 and two plugs 21, 22. Therefore, to one end portion 1a side and the other end 1d side of the base tube 1, it can be provided enlarged diameter portion 1c (121c) and the enlarged diameter portion 1f (121f). Also, the area between the enlarged diameter portion 1c and the enlarged diameter portion 1f of the base tube 1, and a region not subjected to processing remain blank tube 1, providing an area that received ironing in the longitudinal direction on both sides can be, it can be produced in a stepwise manner different from the different thickness steel pipe wall thickness.
[0094]
　In the fifth embodiment described above, the one-dot chain line in FIG. 10 (a) ~ FIG 10 (d) a symmetric axis, were produced in different thickness steel tube 111 using a die 12 of the axisymmetric shape, the die 12 may be a non-axisymmetric shape, it may also be prepared using two plugs shapes are different from each other.
[0095]
Sixth Embodiment
　Next, a method of manufacturing differential thickness steel tube of the sixth embodiment will be described with reference to FIG. 13 (a) ~ FIG 13 (c). Method for manufacturing differential thickness steel pipe of the present embodiment is constituted by the same process as that of the first embodiment. In this embodiment, the die 11 used in the first embodiment using another die 13, to manufacture a different thickness steel tube. Since the other points are the same as the first embodiment, the description thereof is omitted.
[0096]
　Die 13 used in the present embodiment, as shown in FIG. 13 (a), the outer diameter d of the blank tube 1 1 and the first hollow small-diameter portion 13a and a second hollow small-diameter portion 13b having an inner diameter corresponding to the first a thick forming portion 13e provided between the hollow small-diameter portion 13a and a second hollow small-diameter portion 13b, the outer diameter d of the blank tube 1 1 large inner diameter d than 3 and the hollow large diameter portion 13d having the first a tapered portion 13c which is provided between the hollow small-diameter portion 13a and the hollow large diameter portion 13d, and a. The hollow larger-diameter portion 13d, a tapered portion 13c, the first hollow small-diameter portion 13a, the thick formation unit 13e and the second hollow small-diameter portion 13b are communicated with each other in the die body 13i. Further, the die 13 is adapted to be divided into up-down direction in FIG. 13 (a).
[0097]
　Thick formation unit 13e, and the middle air-diameter portion 13f, the medium air-diameter portion 13f and the tapered portion 13h provided between the first hollow small-diameter portion 13a, the middle air-diameter portion 13f and a second hollow small-diameter portion 13b and a, and a tapered portion 13g provided between the. The inner diameter d of the medium air-diameter portion 13f 3 , the outer diameter d of the blank tube 1 1 is greater than the inner diameter is set to be smaller inner diameter than the inner diameter of the hollow large diameter portion 13d. The inner diameter d of the medium air-diameter portion 13f 3 and the inner diameter is larger than the hollow large diameter portion 13d, the air-diameter portion 13f in during ironing process, remain in base tube 1 is not subject to thinning processing, it is pipe expanding Therefore, the thickness of the mother tube 1 in the thick formation unit 13e, remains of the original raw pipe 1.
[0098]
　Next, in the same manner as the first embodiment, the diameter expansion step, as shown in Figure 13 (b). First, in the state of fixing the ends of the left side of the die 13 and blank tube 1, a small-diameter tip portion 21a and the large diameter base end portion 21b of the plug 21 pushes on one end portion 1a of the base pipe 1. Plug 21 is pushed until the tapered portion 21c reaches the position of the tapered portion 13c of the die 13. Thus, enlarged diameter portion 1c and the locking portion 1e1 is formed at one end 1a of the blank tube 1.
[0099]
　Next, as shown in FIG. 13 (c), as ironing step, while the fixed die 13 is maintained, the stationary base pipe 1 in a state of being released, the plug 21 of the base pipe 1 and the other end portion 1d further pushed towards the side. By further pushing the plug 21, although mother tube 1 is pushed toward the other end 1d side from one end 1a, the front locking portion 1e1 formed blank tube 1 in the process, the tapered portion of the die 13 because will remain engaged in 13c, the hollow shell 1 does not move. Tapered portion 21c and the large diameter base end portion 21b of the plug 21, when pushed to the position shown in FIG. 13 (c), the inner diameter d of the air-diameter portion 13f in the die 13 3 the outer diameter d of blank pipe 1 1 from since also large, meat raw pipe 1 flows into the thick formation unit 13e. Thus, the thick portion 1j is formed in the blank tube 1.
[0100]
　Figure 14 shows a schematic cross-sectional view of FIG. 13 (a) ~ 13 different thickness steel tube 141 manufactured through the indicated step (c). The differential thickness steel tube 141, one end portion 141a (1a) expanded diameter portion is expanded from raw pipe 1 In the side 141c (1c), there between one end portion 141a and the other end portion 141d (1d) ironing an intermediate portion 141e which receives the processed (1e), not subject to processing remain blank pipe 1 in the other end portion 141d side than the intermediate portion 141e composed of a raw portion 141 g. Intermediate portion 141e includes a locking portion 141e1 (1e1) which has received the processing by the taper portion 21c of the tapered portion 13c and the plug 21 of the die 13 at the boundary between the enlarged diameter portion 141c, thick formation unit 13e and the plug of the die 13 and a thick portion 141f which receives the processing by the taper portion 21c of the 21.
[0101]
　Hollow portion 141b of the different thickness steel tube 141 has an inner diameter d of the blank tube 1 in the enlarged diameter portion 141c and the intermediate portion 141e 2 while being expanded than the unprocessed portion of 141g in the original mother tube 1 inside diameter d 2 of It has become a remain. The outer diameter of the different thickness steel tube 141, the enlarged diameter portion 141c, the outer diameter d of the blank tube 1 at the locking portion 141E1, and the thick portion 141 f 1 is diameter than the thick portion of the intermediate portion 141e in 141f and a portion other than the engaging portion 141E1, and the unprocessed portion 141 g, the outer diameter d of the blank tube 1 1 stuck in the. Therefore, when viewed along the longitudinal direction, the inner diameter of the portion excluding the part of the拡形portion 141g and the intermediate portion 141e is constant, yet outside different from each other in the thick portion 141f and the enlarged diameter portion 141c It has a different thickness steel tube 141 having a diameter.
[0102]
　In different thickness steel tube 141 shown in FIG. 14, since the processing amount for the enlarged diameter portion 141c and the unprocessed portion 141g is small, or work hardening does not occur in this portion, it is also very little, have occurred. Thus, the enlarged diameter portion 141c and the unprocessed portion strength of 141g is low, even when performing machining after machining such as bending for this part, the annealing process or the like for relieving work hardening is not required.
[0103]
　Further, since a relatively large amount of machining the intermediate portions 141e of the different thickness steel pipe 141, an intermediate portion 141e is relatively strength is increased by work hardening.
[0104]
　Figure 15 shows another example of FIG. 13 (a) ~ the different thickness steel pipe process is manufactured through the shown in Figure 13 (c). That is, in this example, in the step shown in FIG. 13 (c), the large diameter base end portion 21b of the plug 21 by pushing the plug 21 up to the other end portion 1d of the base tube 1, the shape shown in FIG. 15 It is processed into different thickness steel pipe 151.
[0105]
　Different thickness steel tube 151 shown in FIG. 15, one end portion 151a (1a) is expanded from raw pipe 1 In the side the enlarged diameter portion 151c (1c), the one end portion 151a and the other end portion 151d (1d) an intermediate portion 151e (1e) that received in time and ironing, and be in the other end portion 151d side than the intermediate portion 151e and an intermediate portion 151e and the other end portion 151g which receives the ironing as well. Intermediate portion 151e includes a portion receiving the working by the tapered portion 21c of the tapered portion 13c and the plug 21 of the die 13 at the boundary between the enlarged diameter portion 151c, taper portion 21c of the thick forming portion 13e and the plug 21 of the die 13 and it includes a thick portion 151f which receives the processing, the by a.
[0106]
　Hollow portion 151b of the different thickness steel tube 151 has an inner diameter d of the whole of the inner diameter of the longitudinally raw pipe 1 2 has an enlarged diameter than. The outer diameter of the different thickness steel tube 151 has an outer diameter d of the blank tube 1 in the enlarged diameter portion 151c and the thick portion 151f 1 is diameter than the intermediate portion 151e and the other end portions 151g of the non-thick portion 151f the outer diameter d of the hollow shell 1 1 has become a remain. Therefore, a constant total of the inner diameter of the longitudinal, has a different thickness steel tube 151 having a plurality of portions different outer diameters.
[0107]
　In different thickness steel tube 151 shown in FIG. 15, since the processing amount for the enlarged diameter portion 151c is small, or work hardening does not occur in this portion, it is also very little, have occurred. Thus, enlarged diameter portion strength 151c is relatively low, even when performing machining after machining such as bending for this part, such annealing for relieving work hardening is not required.
[0108]
　Further, since the processing amount with respect to the intermediate portion 151e and the other end portion 151g of the different thickness steel tube 151 is relatively large, relatively, the strength is increased by the intermediate portion 151e and the other end portion 151g is work hardened.
[0109]
　As described above, in the embodiment shown in FIG. 13 (a) ~ 14, using the die 13 having a thick wall forming portion 13e between the first hollow small-diameter portion 13a and a second hollow small-diameter portion 13b , to produce a different thickness steel pipe 141. Therefore, it is possible to produce a different thickness steel tube 141 having a thick portion 1j (141 f) in the base tube 1 of the intermediate portion 1e (141e). Further, it is possible to manufacture the different thickness steel tube 141 having different outer diameters de and thick portion 1j and the enlarged diameter portion 1c (141c).
　Moreover, the different thickness steel tube 141, enlarged diameter portion 1c and the processing amount is at the other end portion 1d (141d) side than the intermediate portion 1e is relatively small for low strength, whereas, the middle portion 1e including the thick portion 1j in the processing amount is relatively large because the strength is high.
[0110]
[Seventh Embodiment]
　Next, a method of manufacturing differential thickness steel tube of the seventh embodiment will be described with reference to FIG. 16 (a) ~ FIG 16 (c). Method for manufacturing differential thickness steel pipe of the present embodiment is constituted by the same process as that of the first embodiment. In the present embodiment, the production of different thickness steel tube with another plug 161 is a plug 21 used in the first embodiment. Since the other points are the same as the first embodiment, the description thereof is omitted.
[0111]
　Plug 161 used in this embodiment, as shown in FIG. 16 (a), the inner diameter d of the blank tube 1 2 and the taper end portion 161b having a tip portion 161a of the outer diameter smaller than, the inner diameter d of the blank tube 1 2 the inner diameter d of the hollow small-diameter portion 11a of the large and die 11 than 1 diameter d of less than 5 and a large diameter portion 161c having a diameter d of the large-diameter portion 161c 5 smaller diameter d than 4 small diameter proximal portion 161e having and it is configured from. Between the large diameter portion 161c and a small diameter proximal portion 161e, the taper portion 161d is provided.
[0112]
　Like the first embodiment, a flare process shown in FIG. 16 (b), in the state of fixing the left side of the die 11 and blank tube 1, tapering tip 161b and the large-diameter portion 161c of the plug 161 and pushed at one end 1a of the mother tube 1. Plug 161 is pushed up taper end portion 161b reaches the position of the tapered portion 11c of the die 11. Thus, enlarged diameter portion 1c and the locking portion 1e1 is formed at one end 1a of the blank tube 1.
[0113]
　Next, the ironing process shown in FIG. 16 (c), while the fixed die 11 is maintained, the stationary base pipe 1 in a state of being released, toward the plug 161 at the other end 1d side of the base pipe 1 further pushed Te. By further pushing the plug 161, although mother tube 1 is pushed toward the other end 1d side from one end 1a, the front locking portion 1e1 formed blank tube 1 in the process, the tapered portion of the die 11 since remains locked to the 11c, mother tube 1 does not move.
[0114]
　Engaging plug 161 as shown in FIG. 16 (c), the intermediate portion 1e of the raw pipe 1 a large diameter portion 161c is pushed in the plug 161, the original inner diameter d of the blank tube 1 2 diameter of plug 161 the diameter d of the section 161c 5 is enlarged in size corresponding to. In this case, the small-diameter base end portion 161e that follows the large diameter portion 161c of the plug 161 has a diameter d 4 is the diameter d of the large-diameter portion 161c 5 smaller than the small diameter proximal portion 161e is ironing the mother tube 1 not in contact with the receiving part of the. Thus, in the ironing process, the plug 161 is in contact with the base tube 1 is only the taper end portion 161b and the large-diameter portion 161c. Accordingly, since the portion in contact with the mother tube 1 in the plug 161 is less than that of the first embodiment, frictional resistance between the mother tube 1 and the plug 161 in the ironing process are reduced.
[0115]
　The diameter d of the small-diameter base end portion 161e of the plug 161 in FIG. 16 (a) 4 and the diameter d of the large-diameter portion 161c 5 difference between (d 5 -d 4 ) is preferably in the following ranges. That is, the thickness of the mother tube 1 d 0 and, when the thickness of the intermediate portion 1e after ironing was d, d 0 the difference between the d (d 0 a -d) thickness reduction t d and definition to. In this case, thickness reduction t d and the diameter d of the small diameter proximal portion 161e 4 and the diameter d of the large-diameter portion 161c 5 difference between (d 5 -d 4 ) is, 2 × t d ≧ (d 5 -d 4 ) it is preferable to. The diameter d of the small diameter proximal portion 161e 5 the diameter d of the large-diameter portion 161c 4 difference between (d 5 -d 4 ) is 2 × t d If it is greater, the combination of strength and thickness reduction of the material is in ironing process shown in FIG. 16 (c), the locking portion 1e1 of mother tube 1 can no longer be engaged in the tapered portion 11c of the die 11.
[0116]
　Different thickness steel tube process is manufactured through the shown in FIG. 16 (a) ~ FIG. 16 (c), the same shape as the different thickness steel tube 31 shown in FIG. Further, in the step shown in FIG. 16 (c), by the large diameter portion 161c of the plug 161 is pushed into the plug 161 until the other end portion 1d of the base pipe 1, the same shape as the different thickness steel tube 41 shown in FIG. 3 it may be processed into.
[0117]
　In the above embodiment, as described, by performing the production of the different thickness steel pipe using a plug 161 having a small diameter proximal portion 161e having a smaller diameter than the diameter of the large-diameter portion 161c, the ironing step without a portion undergoing ironing of the small-diameter base end portion 161e and the blank tube 1 are in contact, it is possible to perform the ironing process. That is, only the taper end portion 161b and the large-diameter portion 161c is in pushing the plug 161 is in sliding contact with the inner surface of the base tube 1, also primarily only the large-diameter portion 161c is in deriving the plug 161 is raw pipe 1 in sliding contact with the inner surface. When connecting or disconnecting the plug 161 in this manner, since the small-diameter base end portion 161e is not in sliding contact with the inner surface of the mother tube 1, base pipe when compared to the first embodiment, connecting or disconnecting the plug 161 in the ironing process it is possible to reduce the frictional resistance between the 1 and the plug 161, the force required for machining can be prevented from becoming excessive.
[0118]
[Eighth Embodiment]
　method of manufacturing differential thickness steel pipe according to the eighth embodiment, the first to fourth embodiments, after the ironing of the embodiments and the seventh embodiment of the sixth, a step of performing drawing. In the present embodiment, as an example, a different thickness steel tube 61 which processes manufactured through a second embodiment the intermediate product 15, performs drawing on this intermediate product 15.
[0119]
　First, the die 14 and the intermediate product 15 used in this embodiment will be described with reference to FIGS. 17 (a) and 17 (b). Intermediate product shown in FIG. 17 (a) 15 is a different thickness steel tube 61 which is manufactured through the steps of the second embodiment. Intermediate product 15 includes a radially enlarged portion 15c that is enlarged from raw pipe 1 In the one end 15a side, and an intermediate portion 15e having received the matching ironed between one end portion 15a and the other end portion 15d, the intermediate portion not receiving processing remains blank pipe 1 in the other end portion 15d side than 15e composed of a raw portion 15f. Intermediate portion 15e, at each boundary between the enlarged diameter portion 15c and the unprocessed portion 15f, the tapered portion 51d of the tapered portion 11c and the plug 51 of the die 11 used in the second embodiment, receiving the processing by 51e parts are also included in.
[0120]
　Die 14 shown in FIG. 17 (a) from a hollow small-diameter portion 14b having an outer diameter and the corresponding inner diameter of the unprocessed portion 15f and the middle portion 15e of the intermediate product 15, a tapered portion 14c continuous with the hollow small-diameter portion 14b It is configured. The above and "outer diameter corresponding the inner diameter of the unprocessed portion 15f and the middle portion 15e", compared the outer diameter of the unprocessed portion 15f and the middle portion 15e, which can connect or disconnect into and out of the hollow small-diameter portion 14b It shows the diameter plus a degree of clearance dimensions. Further, the hollow small-diameter portion 14b and the tapered portion 14c is communicated in the die body 14e.
　The outer diameter of the unprocessed portion 15f and the middle portion 15e of the intermediate product 15 has an outer diameter d of the blank tube 1 1 because it is the same as the inner diameter of the hollow small-diameter portion 14b is the outer diameter d of the blank tube 1 1 corresponds to the. The inner diameter of the tapered portion 14c becomes a maximum diameter at one end 14a side of the die 14, the inner diameter d of the position 6 is set to a larger dimension than the outer diameter of the enlarged diameter portion 15c of the intermediate product 15.
[0121]
　Next, a method for manufacturing differential thickness steel tube according to the present embodiment. First, to produce the intermediate product 15. Since the production method of the intermediate product 15 is similar to the second embodiment, the description thereof is omitted.
　Next, as shown in FIG. 17 (a) and FIG. 17 (b), the state of fixing the die 14 is inserted towards the other end 14d side intermediate product 15 from one end 14a side of the die 14. The locking portion 15e1 of the intermediate product 15 reaches the position of the tapered portion 14c of the die 14, although the enlarged diameter portion 15c is engaged with the tapered portion 14c, further pushing the intermediate product 15 at the other end 14d side. Then, by engaging portion 15e1 and the enlarged diameter portion 15c is pressed against the tapered portion 14c, the outer surface of the locking portion 15e1 and the enlarged diameter portion 15c is pressed, these external with respect to the locking portion 15e1 and the enlarged diameter portion 15c drawing is performed to narrow the diameter.
[0122]
　Engaging intermediate product 15 to the position shown in FIG. 17 (b), drawing is performed on all of the locking portion 15e1 and the enlarged diameter portion 15c. Therefore, the outer diameter of the longitudinal entire intermediate product 15, the inner diameter d of the hollow small-diameter portion 14b of the die 14 1 is the same outer diameter as.
[0123]
　Figure 18 shows a cross-sectional schematic view of a different thickness steel tube 181 manufactured by the present embodiment. The differential thickness steel tube 181, in the one end portion 181a (15a) side, the reduced diameter portion 181c of the enlarged diameter portion 15c of the intermediate product 15 is subjected to drawing, corresponding to the engaging portion 15e1 which has received the same drawing to include a portion. On the other hand, other portions of different thickness steel tube 181 includes an intermediate portion 181e not receiving remains drawing of intermediate product 15 (15e), and the unprocessed portion 181f receiving no remains drawing of intermediate product 15 (15f), It consists of.
[0124]
　Hollow portion 181b of the different thickness steel tube 181, the outer diameter of the whole of its longitudinal direction is kept in the outer diameter of base pipe 1. The inner diameter of the different thickness steel tube 181 has an inner diameter d of the blank tube 1 at reduced diameter portion 181c and the unprocessed portion 181f 2 remains, the intermediate inner diameter d of the base pipe 1, 181e 2 are diameter than . Therefore, the different thickness steel tube 181 has an outer diameter in the longitudinal direction of the whole is constant, the inner diameter has a plurality of regions different in each position in the longitudinal direction.
[0125]
　Differential thickness steel tube 181, the thickness of the reduced diameter portion 181c and unprocessed portion 181f is relatively thick, the wall thickness in the intermediate portion 181e is relatively thin.
[0126]
　In the different thickness steel pipe 181, the processing amount for the unprocessed portion 181f is small, or work hardening does not occur in this portion, it is also very little, have occurred. Accordingly, the strength of the unprocessed portion 181f is relatively low, even when performing machining after machining such as bending for this part, such annealing for relieving work hardening is not required.
[0127]
　In the present embodiment has illustrated the different thickness steel tube 61 produced in the second embodiment as the intermediate product 15, the present embodiment is not limited thereto. Intermediate product in the present embodiment may be, for example, different thickness steel tube 31 produced in the first embodiment shown in FIG.
[0128]
　The inner diameter of the hollow small-diameter portion 14b of the die 14 used in this embodiment, in order to perform the drawing with respect to all of the outer surface of the intermediate product 15, even smaller inner diameter than the outer diameter of the mother tube 1 good. In this case, the inner diameter of the hollow small-diameter portion 14b of the die 14 is too small for the outer diameter of the mother tube 1, the mouth aperture ratio becomes too large, there is a possibility that buckling during drawing occurs. For mouth drawing rate at this time will be described below.
[0129]
　Generally, the steel tube for an automobile, the ratio between the outer diameter of the thickness and steel of the steel pipe (t / D 0 , t: a base pipe thickness, D 0 : the outside diameter of the blank tube) is 0.001 to 0 steel pipe of .15 is used. The present inventors have, as a result of detailed studies about the mouth aperture ratio in the case of performing drawing processing to steel pipe of this size, mouth drawing ratio to obtain a finding that it is preferable to 0.4. Therefore, when performing drawing against all of the outer surface of the intermediate product 15, the inner diameter of the hollow small-diameter portion 14b of the die 14 may be set as the mouth aperture ratio becomes 0.4 or less. Incidentally, the mouth squeezing ratio is represented by the following formula (1), the κ of the following formulas (1) and the mouth aperture ratio, D 0 is the outer diameter of the steel pipe before drawing, D is after drawing it is the outer diameter of the steel pipe.
[0130]
　　κ＝（Ｄ ０－Ｄ）／Ｄ ０・・・（１）
[0131]
　In the above embodiment, as described, with the outer diameter of the entire longitudinal direction of the mother tube 1 is constant, the inner diameter can be produced with different thickness steel tube 181 having a plurality of different areas respectively. The differential thickness steel tube 181, since the processing amount for the unprocessed portion 181f is relatively small, a relatively low intensity of this region, since the processing amount for the reduced diameter portion 181c and the intermediate portion 181e is relatively large, these areas the strength of is relatively high.
[0132]
　Further, by performing drawing to the longitudinal direction of the whole of the outer surface of the intermediate product 15 can be produced different thickness steel tube machining is performed with respect to the longitudinal direction of the entire area. Further, an outer diameter in the longitudinal direction of the whole is constant, the inner diameter can be produced with different thickness steel tube having a plurality of different areas respectively. The differential thickness steel tube, since the processing with respect to the longitudinal direction of the entire area of ​​the mother tube 1 is applied, the strength of the entire area is higher than the original mother tube 1.
[0133]
[Ninth Embodiment]
　The ninth embodiment will be described. Method for manufacturing differential thickness steel pipe of the present embodiment is constituted by the same process as that of the first embodiment. In this embodiment, the plug 21 used in the first embodiment by using a die 11 used in another plug of the first embodiment, to manufacture a different thickness steel tube. Or, the die 11 used in the first embodiment with reference to the plug 21 used in another die to the first embodiment, the production of different thickness steel tube. Since other points are the same as in the first embodiment, the description thereof is omitted. Hereinafter, as an example of the ninth embodiment, and another plug from the plug 21 used in the first embodiment, a method of manufacturing differential thickness steel tube and using a die 11 used in the first embodiment explain.
[0134]
　Plug 19 shown in FIG. 19 has a shape different from the plug 21 shown in FIG. 1 (a). Sectional shape perpendicular to the longitudinal direction of the plug 19 is made in the longitudinal direction of all the rounded square shape. Moreover, the plug 19 includes a small tip 19a, and a large base end portion 19b, and a tapered portion 19c provided between the small tip 19a and large proximal end portion 19b, and a.
　Of a cross section perpendicular to the longitudinal direction of the small tip 19a, a diagonal length d7, the inside diameter d of the blank tube 1 2 and has a diameter corresponding with. In a cross section perpendicular to the longitudinal direction of large proximal end 19b, one side of the rounded rectangles length d8, the inside diameter d of the blank tube 1 2 correspond to the diagonal length d9, the inside diameter d of the blank pipe 1 2 from large and the inner diameter d of the hollow small-diameter portion 11a of the die 11 is also 1 becomes less than.
[0135]
　Shape using a plug 19, when the production of different thickness steel tube by the same process as in the first embodiment, the schematic cross-sectional view perpendicular to the longitudinal direction of the intermediate portion which receives the ironing, which is shown in FIG. 20 (a) become. In large base end portion 19b of the plug 19, a side length d8 inner diameter d of the blank tube 1 2 correspond to major axis d9 inner diameter d of the blank tube 1 2 larger than, the different thickness steel tube produced by the plug 19 intermediate portion of 20A has a raw unit 20a has not received the processing remains mother tube 1, and a workpiece portion 20b which receives the ironing. Unprocessed portion 20a remains its thickness is blank pipe 1, is relatively low strength since the processing amount is small. On the other hand, the machined portion 20b is relatively strong is higher because the thickness is relatively thin, the processing amount is large. Therefore, different thickness steel tube 20A prepared in accordance with the present embodiment, the intermediate portion which receives the ironing, and a receiving portion and a raw leave portions ironing, along the circumferential direction have alternately.
[0136]
　In the above ninth embodiment described, the cross-sectional shape perpendicular to the longitudinal direction of the rounded square shape of the plug 19, to produce a different thickness steel tube 20A through the same process as in the first embodiment by using a die 11 but the sectional shape perpendicular to the longitudinal direction may be used a plug of other shapes. However, may cross section perpendicular to the longitudinal direction of the plug is rotationally symmetrical shape. This is because, if the cross section perpendicular to the longitudinal direction of the plug is not rotationally symmetrical, can not be sufficiently form the enlarged diameter portion by pipe expanding, locking the base pipe 1 to the tapered portion 11c of the die 11 it is because it can not.
　FIG. 20 (b) and the FIG. 20 (c) is a cross section perpendicular to the longitudinal direction in the intermediate portion of the different thickness steel tube 20B, 20C manufactured using another plug is rotationally symmetrical shape in the eighth embodiment, it is a diagram showing a cross section perpendicular to the longitudinal direction.
[0137]
　As described above, in this embodiment, the die 11 used in the first embodiment with reference to the plug 21 used in another die and the first embodiment, even if the production of different thickness steel tube good. The die used in this case, to allow the pipe expanding sufficiently, may cross-section perpendicular to the longitudinal direction of the die is rotationally symmetrical. The outer shape of the blank tube 1 must be shape corresponding to the die.
　For example, a square tube, and a die having a shape corresponding to the RHS, using the same plug 21 in the first embodiment, when as in the first embodiment to produce a different thickness steel pipe 20D, the difference sectional shape perpendicular to the longitudinal direction in the intermediate portion of the thickness steel tube 20D has a shape shown in FIG. 20 (d).
　Figure 20 (e) are cross-sectional outer shape of the blank tube is elliptical, with a die and a plug 21 having a shape corresponding to the base pipe, the different thickness steel tube manufactured by the same method as in the first embodiment it is a schematic cross-sectional view of an intermediate portion of 20E. In this case, a partial and raw remained portion undergoing ironing, along the circumferential direction have alternately.
[0138]
　As described above, the different thickness steel tube having According to the ninth embodiment, in the intermediate portion having received the ironing, and a receiving portion and a raw leave portions ironing, alternately along the circumferential direction it can be manufactured 20A. Moreover, the different thickness steel pipe 20A, the portion receiving the ironing, the wall thickness is thin, relatively strong large because the processing amount is large. On the other hand, part of the left unprocessed, the wall thickness is thick, relatively low strength since the processing amount is small.
[0139]
　As described above, in the manufacturing method of the different thickness steel tube according to embodiments of the present invention, the locking portion is provided by performing a pipe expanding the base tube, the plug while keeping engaged the locking portion to the die element by pushing the tube, the intermediate portion at the other end side of the enlarged diameter portion of the base pipe, performing ironing whose diameter increases the inner diameter while maintaining the outer diameter of the base pipe. Accordingly, requires less processing amount for the enlarged diameter section, it can be made unnecessary heat treatment annealing or the like when performing processing after processing such as bending against the enlarged diameter portion.
　Also, in order to perform ironing of the engaging portion pushes the plug while to engage with the die to blank tube, it is not necessary to fix the base pipe itself during ironing, ironing in a die and a plug only relatively moving working It can be carried out.
[0140]
　Further, in the longitudinal direction of the different thickness steel tube, a relatively high portion thickness is thin strength, it can wall thickness thicker strength to form a relatively low portion. Therefore, when performing a post-processing such as bending relatively low strength portion thicker wall thickness, it can be made unnecessary heat treatment annealing or the like.
[0141]
　For some applications the different thickness steel pipe in the embodiments of the present invention, the cross member in automotive parts, suspension members, frame members such as suspension arms, and the impact countermeasure components such as Perimeter and side impact bar or, for example, a drive shaft, drive system pipe pieces and the like.
　Cross member, a suspension arm, a frame member such as a suspension member, since in many cases thickness particularly to the mounting portion of the other parts are required, the use of different thickness steel pipe in the embodiments of the present invention, where required only it is possible to adopt the the thick of the lightweight structure. Further, in these components, during the processing after shaping the thick portion into a predetermined shape, there is a case where press working or bending process is performed. In this case, since the easy processing and the portion machining is performed is thick and low strength, it is possible to use different thickness steel pipe in the embodiments of the present invention suitably.
　Side impact bar is installed in the door panel, a member for transmitting the impact energy on both sides of the door during a collision, it is desirable not broken at the time of collision. Therefore, if thickening the central portion with a different thickness steel pipe in the embodiments of the present invention, it can be a lightweight construction.
　Perimeter is the front portion of the vehicle body frame member, is a member of the load transfer path at the time of frontal collision, by a thick portion such as bending easily bent shape portion at the time of a collision, can be more lightweight. Also, when bending a thick portion, the thickness since the wall portion is easily processed with a low intensity, can be used different thickness steel pipe in the embodiments of the present invention suitably.
　Drive shaft may perform splined to the different thickness of the tube end, because this part is easier to work with a thick, low intensity, preferably used different thickness steel pipe in the embodiments of the present invention be able to.
[0142]
　Summarized below gist of the embodiments described above.
(1) For example, FIGS. 1 (a) method for producing a different thickness steel pipe according to the first embodiment described with reference to-FIG. 2, different thickness steel tube 31 from the base pipe 1 of the hollow cylindrical (hollow cylinder shape) a method for producing a: the mother tube 1 was placed in a die 11, while restricting the movement in the longitudinal direction of the mother tube 1, plug from one end of the base pipe 1 (one end portion 1a) 21 pushed by the one end of the outer locking step and a larger (outer diameter) to (diameter) is allowed to be engaged with the die 11; while solving the regulation of the mother tube 1, the said mother tube 1 while the locking is maintained, the by pushing toward the plug 21 to further the mother tube 1 on the other end (the other end portion 1d), said base tube 1 outer inner while maintaining the (outer diameter) shape ( having; and ironing forming a thin portion 1e (31e) was added to ironing to expand the inner diameter).
(2) Then, as shown in FIG. 1 (c) and FIG. 2, in the manufacturing method of the different thickness steel pipe according to (1), in the ironing step, by stopping the pushing of the plug 21 in the middle it may be left unprocessed portion 31f to the other end of the blank pipe 1 (the other end portion 1d).
(3) Further, as shown in FIG. 1 (c) and FIG. 2, the (1) or in the method for manufacturing differential thickness steel tube described in (2), the thin portion 1e in the ironing step of (31e) the thinning rate may be in the range of 10% to 90%.
(4) Further, as shown in FIG. 1 (c), in the manufacturing method of the different thickness steel tube according to any one of the above (1) to (3), in the locking step and the ironing step, tip having a smaller outside dimension than the (outer diameter) inner dimensions of the blank tube 1 (inner diameter) and (small-diameter tip portion 21a), and larger than the inner dimensions of the blank tube 1 (inner diameter) proximal section having the base tube 1 outside dimensions size than outside dimensions of (outer diameter) (outer diameter) and (large diameter end portion 21b), said proximal end portion (large diameter end 21b the tip portion from) (to be tapered toward the small-diameter tip portion 21a), said tip portion (small-diameter tip portion 21a) and a tapered portion 21c which is provided between the base end portion (large diameter end portion 21b) When, may be used the plug 21 provided with.
(5) In addition, for example, as in the third embodiment described with reference to FIG. 7 (a) - FIG 7 (c), the different thickness steel tube according to any one of the above (1) to (3) in the method of manufacturing, the locking step and the in ironing process, external dimensions (outer than inner dimensions of the blank tube 1 (inner diameter) greater than and the mother tube 1 outside dimensions (outer diameter) and a proximal end 71b having a diameter), continuous to the distal side of the proximal end portion 71b, the distal end portion that tapers as the distance from the proximal end portion 71b (the taper end portion 71c), said plug 71 having a it may be used.
(6) In addition, for example, as the seventh embodiment described with reference to FIG. 16 (a) ~ FIG 16 (c), in the manufacturing method of the different thickness steel tube described in above (4) or (5), said proximal portion, said large base end disposed at the distal end side (large-diameter portion 161c), the outer dimensions than the large base end portion (outer diameter) is less compact base portion (small diameter a proximal portion 161e), may have.
[0143]
(7) For example, FIGS. 4 (a) production method of different thickness steel pipe according to the second embodiment described with reference to to 6, hollow cylindrical different thickness steel tube from raw pipe 1 (hollow cylinder shape) 61 a method of manufacturing a, the mother tube 1 was placed in a die 11, while restricting the movement in the longitudinal direction of the mother tube 1, first from one end of the base pipe 1 (one end portion 1a) 1 of the plug and the locking step of engaged with the die 11 by external dimension of the one end side is pushed (the plug 21) (one end portion 1a) larger (outer diameter) (increased diameter); and the mother tube 1 more said first plug and extraction step withdrawing the (plug 21); while solving the regulation of the mother tube 1, while the locking of the mother tube 1 was maintained, the first plug (plug 21) than the contour of different second plug from said one end of the (plug 51) the raw tube 1 (one end portion 1a) By pushing toward the end side (the other end portion 1d), to form a thin portion 1e (61e) was added to ironing to expand the blank tube 1 outer inner shape while maintaining the (outer diameter) (inside diameter) having; and ironing process.
(8) Then, as shown in FIG. 5 (a) and 5 (b), in the manufacturing method of the different thickness steel pipe according to (7), in the ironing step, inner dimensions of the blank tube 1 small small tip than (inner diameter) and (small-diameter tip portion 51a), the middle-sized portion having a larger outer dimension (outer diameter) than inner dimensions of the blank tube 1 (inner diameter) (medium diameter 51b a) large with external dimensions (larger than the outer diameter dimension) and said base tube 1 dimensions (outer diameter) of less than external dimensions of the in-shaped portion (middle-diameter portion 51b) (outer diameter) parts and (large diameter end portion 51c), the small distal portion and the first tapered portion provided between (the small-diameter tip portion 51a) and the in-shaped portion (middle-diameter portion 51b) (first tapered portion 51d) the in-shaped portion (medium diameter 51b) and a second taper provided between said large portion (large diameter end portion 51c) (Second tapered portion 51e), it may be used the with the second plug (plug 51).
(9) Further, as the fourth embodiment described with reference to FIGS. 8 (a) and 8 (b), in the manufacturing method of the different thickness steel pipe according to (7), with the ironed step , and a proximal end 81b having the inner dimensions of the blank tube 1 (inner diameter) greater than and the mother tube 1 dimensions (outer diameter) of less than external dimensions (outer diameter); the proximal portion the third tapered portion that tapers toward the tip portion 81a from 81b and (taper end portion 81c); or by using the second plug with a (plug 81).
(10) as in the above first embodiment described with reference to FIG. 1 (a) - FIG. 1 (c), the manufacturing method of the different thickness steel tube according to any one of the above (1) to (9) in the die 11, a hollow small portion having the inner shape dimension (inner diameter) corresponding to the base tube 1 dimensions (outer diameter) and (hollow small-diameter portion 11a); said blank tube 1 dimensions ( hollow large portion having a larger inner dimensions than the outer diameter dimension) (inner diameter) (hollow large diameter portion 11b) and; said hollow small portion (hollow small-diameter portion 11a) and the hollow large portion (hollow large diameter portion and provided 11b) between said hollow large portion (hollow large diameter part 11b) from the hollow small portion (hollow small-diameter portion 11a) tapering toward the hollow tapered portion (tapered portion 11c); includes a it may be.
(11) As in the sixth embodiment described with reference FIG. 13 (a) ~ FIG 13 (c), in the manufacturing method of the different thickness steel pipe according to (10), the die 13, the hollow and provided in a part of the longitudinal direction of the small portion (the hollow small-diameter portion 13a), the air-diameter portion (thickness in having external dimensions of the blank tube 1 inner dimensions (inner diameter) larger than the (outer diameter) meat forming portion 13e) may further comprise a.
(12) as in the eighth embodiment described with reference to FIG. 17 (a) - 18, in the manufacturing method of the different thickness steel tube according to any one of the above (1) to (11), wherein ironing may further include a drawing step of adding drawing to the post-processing step mother tube 1 (intermediate product 15).
[0144]
(13) For example, FIG. 10 (a) the production method of different thickness steel pipe according to the fifth embodiment described with reference to to 11, hollow cylindrical different thickness steel tube from raw pipe 1 (hollow cylinder shape) 111 a method of manufacturing a, the mother tube 1 disposed in the die 12, the plug 21 for each of the one end of the base pipe 1 (one end portion 1a) and the other end (the other end portion 1d), by pushing the 22 simultaneously or alternately engaged with the die 12 by a larger outer shape of the one end side (one end portion 1a) outer shape of (outer diameter) and the other end (the other end 1d) (outer diameter) a locking step of locked; while inserting the plug 21 into the one end side (one end portion 1a), wherein the extraction step of pulling out the plug 22 of the other end (the other end 1d); one end side (one end the parts 1a locking portion of the side 1 g 1) while keeping engaged with the die 12, the one end side (an The other end of the plug 21 which is inserted into section 1a) Further, the raw pipe 1 (by pushing towards the other end 1d), the while maintaining the mother tube 1 outer shape (outer diameter) form a first thin portion added ironing spreading the (inner diameter) of the first ironing process for forming the (intermediate portion 1 g); while withdrawing the plug 21 of the one end side (one end portion 1a), the other end side and insertion step of inserting the plug 22 (the other end portion 1d); while the other end (the engaging portion 1h1 on the other end 1d side) was engaged with the die 12, the other end wherein by pushing toward the one end of addition the mother tube 1 a plug 22 (one end portion 1a), the inner shape (inner diameter while maintaining the outer shape (outer diameter) the base tube 1 (the other end portion 1d) the second thin portion) was added ironing spreading the (second to form the intermediate portion 1h) A mistake processing step; has, in the locking step, when pushing the plug 21 and 22 at the same time, a freely moving the base tube 1 along the longitudinal direction of the mother tube 1, the plug 21 , when pushing the 22 alternately, restricts the movement of the blank tube 1 in the pushing direction of the plug 21.
(14) In the method for manufacturing differential thickness steel pipe according to (13) according to the fifth embodiment shown in FIG. 11, squeezing the blank tube 1 after the second ironing process (different thickness steel tube 111) it may further include a drawing process.
(15) In the manufacturing method of the different thickness steel tube according to any one of the above according to the embodiments (1) to (14), said base tube 1 may be a seamless steel pipe.
[0145]
(16) For example, the different thickness steel tube 31 according to the first embodiment described with reference to FIG. 2, adopts the following configuration: and provided on one side of the longitudinal direction, perpendicular to the longitudinal direction the other enlarged portion (enlarged diameter portion 31c), than the expansion portion (enlarged diameter portion 31c) when viewed along the longitudinal direction having the largest outer dimension (outer diameter) when viewed such in cross-section and provided on the side, the enlargement portion (enlarged diameter portion 31c) the thickness is thin walled portion than (intermediate portion 31e), provided with: the enlarged portion of the average value of the hardness of the (enlarged diameter portion 31c) H1 , the average value of the hardness of the thin portion (the intermediate portion 31e) in the case of the H2, satisfy H2> H1.
In different thickness steel tube 31 according to (17) above (16), may be employed the following configuration: the other side of the thin portion when viewed along the longitudinal direction (middle portion 31e) are arranged, the thin portion wall is thick thick portion than (intermediate portion 31e) (unprocessed portion 31f) further comprises a; If the average value of the hardness of the thick portion (unprocessed portion 31f) was H3 a, H2> satisfy H1 ≧ H3.
(18) For example, in the different thickness steel tube 31 according to the above (17), may be employed the following configuration: the thin portion (the intermediate portion 31e), most in the thin portion (the intermediate portion 31e) and wall thickness thinner straight pipe portion 31e2, the enlarged outer shape toward the enlarged portion (enlarged diameter portion 31c) together is provided between the straight tube portion 31e2 and the enlarged portion (enlarged diameter portion 31c) (outer diameter) a first tapered portion (engaging portion 31e1), wherein the thickness is thick toward the thick portion together is provided between the straight tube portion 31e2 and the thick portion (unprocessed portion 31f) (unprocessed portion 31f) a second tapered portion (tapered portion 31e3), a has made; first tapered portion the average value of the hardness of (engaging portion 31e1) H4, the average value of the hardness of the straight tube portion 31e2 H5, and the first of the hardness of the second tapered portion (tapered portion 31e3) flat When the value was H6, satisfy both equations of H5> H6 ≧ H3 and H5> H4> H1.
(19) In the different thickness steel tube 141 according to any one of the above according to the sixth embodiment described (16) - (18) with reference to FIG. 14, the thickness of the thin portion (intermediate portion 141e) but when viewed along the longitudinal direction, it may be partially thicker (thick portion 141 f).
(20) as the different thickness steel tube 111 according to the above (16) according to the fifth embodiment described with reference to FIG. 11, the enlarged portion (enlarged diameter portion 111c, 111f) and said thin portion (intermediate portion 111 g, a combination of 111h) may also be symmetrically provided in the longitudinal end.
In different thickness steel tube 111 according to (21) above (20), may be employed the following configuration: a pair of said thin portion (middle portion 111g, 111h) is disposed between the thin portion (intermediate portion 111g , further comprising a wall thickness thick-walled portion (the unprocessed portion 111i) than 111h); if the thick portion of the average value of the hardness (unprocessed portion 111i) was H7, H2> the H1 ≧ H7 Fulfill.
[0146]
(22) For example, the different thickness steel tube 181 according to the eighth embodiment described with reference to FIG. 18 employs the following structure: and is provided on one side of the longitudinal direction, perpendicular to the longitudinal direction a thickest is thick-walled portion when viewed in cross-section and (reduced diameter portion 181c), wherein and provided on the other side of the thick portion (reduced diameter portion 181c), the thick portion (reduced diameter of the thick portion (reduced diameter portion 181c); parts 181c) thickness is thin walled portion than (the intermediate portion 181e), the comprising: a longitudinal direction along outer dimensions (outer diameter) is located at a constant the average value of the hardness H8, the thin portion of the average value of the hardness of the (intermediate portion 181e) when the H9, satisfy H9> H8.
(23) In the different thickness steel tube 20 according to any one of FIG. 20 described above according to the ninth embodiment described with reference to (a) (16) ~ (22), said thin wall portion, the longitudinal wherein when viewed along a circumferential direction of the thin portion, relatively, the wall thickness thin has high hardness region (portion to be processed 20b), a region lower hardness the thickness is thicker in a cross section perpendicular to and (unprocessed portion 20a), but may have a rotationally symmetrical shape alternating along the circumferential direction.
(24) different thickness steel tube according to any one of the above (16) to (23), a seamless steel pipe or as a material.
Industrial Applicability
[0147]
　According to the present invention, less processing amount at the time of manufacture, the manufacturing methods and the different thickness steel tube different thickness steel pipe which does not require heat treatment of annealing or the like when performing processing after bending, etc., it can be provided.
DESCRIPTION OF SYMBOLS
[0148]
　1 blank tube
　1a one end (one end
　side) 1d other end (the other
　end) 1e, 31e, 61e thin portion
　1g intermediate part (first thin
　part) 1 g 1 one end of the locking portion (one end
　side) 1h intermediate part (second thin
　part) 1h1 engagement portion of the other end (the other
　end) 11, 12, 13 die
　11a hollow small-diameter portion (hollow small portion)
　11b hollow larger-diameter portion (hollow large
　portion) 11c taper part (hollow tapered
　portion) 13a hollow small-diameter portion (hollow small
　portion) 13e thick forming unit (medium air-diameter
　portion) 20a unprocessed portion (thick low hardness region wall
　thickness) 20b workpiece portion (thickness is thin hardness Te high
　region) 21 plug (first
　plug) 21a small-diameter distal end portion (distal end
　portion) 21b large diameter end portion (base end
　portion) 21c tapered portion
　22,71 plug
　31,61,111,141,181 difference thick steel pipe
　31c, 41c, 61c, 91c, 11 c, 111f, 121c, 141c, 151c enlarged diameter portion (enlarged
　portion) 31e, 111 g, 111h intermediate portion (thin
　portion) 31e1 locking portion (first tapered
　portion) 31e2 straight pipe portion
　31e3 tapered portion (second tapered portion)
　31f, 111i unprocessed portion (the unprocessed portion, the thick
　portions) 51 and 81 plug (second
　plug) 51a small-diameter tip portion (small
　tip) 51b in diameter (medium size
　portion) 51c large diameter end ( large
　portion) 51d first tapered portion (first tapered
　portion) 71b, 81b proximal end
　71c taper end portion (distal end
　portion) 81a tip
　81c taper end portion (the third tapered
　portion) 141e intermediate portion (thin portion )
　161c large diameter portion (large proximal end
　portion) 161e small diameter proximal end (small proximal
　end) 181c reduced diameter portion (thick
　portion) 181e intermediate portion (thin portion)

WE CLAIM

[Requested item 1]
　A method of manufacturing a differential thickness steel tube from a hollow cylindrical blank tube,
　the blank tube was placed in the die, while restricting the movement in the longitudinal direction of the mother tube, from one end of the base pipe push the plug by enlarging the external shape of the one end side locking step and to engaged with the die;
　while solving the regulation of the mother tube, while the locking of the mother tube was maintained, further said plug by pushing towards the other end of the base pipe, and ironing forming a thin portion by the addition of ironing to expand the inner shape while maintaining the outer shape of the base pipe;
and having a, method of manufacturing a different thickness steel pipe.
[Requested item 2]
　Wherein in ironing step, by stopping the pushing of the plug in the middle, leaving a raw portion in the other end of the base pipe
and wherein the method for producing a different thickness steel tube according to claim 1.
[Requested item 3]
　The thinning rate of the thin portion of the ironing step in the range of 10% to 90%
, wherein the method for producing a different thickness steel tube according to claim 1 or 2.
[Requested item 4]
　In the locking step and the ironing step,
　　and a tip portion having a smaller outer dimension than the inner dimensions of the blank tube,
　　greater than the inner dimensions of the base pipe and less than the size of the external dimension of the base pipe a proximal end portion having outer dimensions of,
　　so that the tapered from the proximal end toward the distal end, and a tapered portion provided between the tip and the base end
of the plug with the used
wherein the method for producing a different thickness steel tube according to any one of claims 1 to 3.
[Requested item 5]
　In the locking step and the ironing step,
　　a proximal end portion having an outer dimension less than external dimensions of larger and the base pipe than inner dimensions of the base pipe,
　　continuous to the distal side of the proximal end portion, said , a distal portion that tapers as the distance from the proximal end
using the plug having a
, wherein the method for producing a different thickness steel tube according to any one of claims 1 to 3.
[Requested item 6]
　It said proximal portion has a large proximal end portion disposed on the distal end side, and a small base end outer dimensions smaller than the large base end portion
, characterized in that, according to claim 4 method for manufacturing differential thickness steel tube according to or 5.
[Requested item 7]
　A method of manufacturing a differential thickness steel tube from a hollow cylindrical blank tube,
　the blank tube was placed in the die, while restricting the movement in the longitudinal direction of the mother tube, from one end of the base pipe ; first locking step and to push the plug by enlarging the external dimensions of the one end engaged to the die
　; evacuation step and withdrawing the first plug from the base pipe
　the regulation of the mother tube while solving, while the locking of the mother tube was maintained, and the first plug by pushing toward the different second plug external shape to the other end than the one end of the base pipe, the and ironing forming a thin portion by the addition of ironing to expand the inner shape while maintaining the outer shape of the mother tube;
having
, characterized in that, the production method of different thickness steel tube.
[Requested item 8]
　In the ironing step,
　　a small small tip than inner dimensions of the blank tube,
　　a middle-sized portion having a larger outer dimensions than the inner dimensions of the base pipe,
　　larger than the outer dimensions of the in-shaped portion and a large portion having an outer dimension less than external dimensions of the base pipe,
　　a first tapered portion provided between the small tip and the in-shaped part,
　　between the in-shaped portion and the large portion a second tapered portion provided,
using said second plug having a
, wherein the method for producing a different thickness steel tube according to claim 7.
[Requested item 9]
　In the ironing process,
　　the base end portion and having an outer dimension less than external dimensions of larger and the base pipe than inner dimensions of the base pipe;
　　third that tapers toward the tip portion from the proximal portion a tapered portion;
using said second plug having a
, wherein the method for producing a different thickness steel tube according to claim 7.
[Requested item 10]
　The die is
　　hollow small portions and having a inner shape dimension corresponding to the outer dimension of the base pipe;
　　hollow large portion and having a larger inner dimensions than the outer dimensions of the mother tube;
　　said hollow small portions and the hollow provided between large portion and a hollow tapered portion tapers towards the said hollow large part to the hollow small portion;
comprises
, characterized in that, in any one of claims 1 to 9 manufacturing method of the different thickness steel pipe described.
[Requested item 11]
　The die, and provided in a part of the longitudinal direction of the hollow small portion further comprises an aerial diameter in having inner dimensions larger than the outside dimension of the base pipe
and wherein the claim 10 method for manufacturing differential thickness steel tube described.
[Requested item 12]
　Further comprising a drawing step for working aperture with respect to the base tube after the ironing step
wherein the method for producing a different thickness steel tube according to any one of claims 1 to 11.
[Requested item 13]
　A method of manufacturing a differential thickness steel tube from a hollow cylindrical blank tube,
　the blank tube is placed into the die, forcing the plug simultaneously or alternately to each of the one end and the other end of the base pipe it allows the one end side of the outer shape and the locking step and that by expanding the outline of the other end engaged with the die;
　while inserting the plug into the one end, pulled out the plug of the other end a draw-out step;
　while the one end side is engaged in the die, by pushing the plug is inserted further toward the other end of the mother tube on the one side, the outer shape of the base pipe the first ironing step of forming a first thin portion added ironing to expand the inner shape while maintaining a;
　while withdrawing the plug of the one end side, insertion of inserting the plug into the other end step a;
　the die the other end While keeping locked to, by pushing toward the one end side of further said mother tube the plug of the other end, the addition of ironing to expand the inner shape while maintaining the outer shape of the raw material tube 2 of a second ironing step of forming a thin portion;
has,
　in the locking step,
　　when pushing the plug at the same time, the movable said base tube along the longitudinal direction of the mother tube,
　　when pushing the plug alternately, it restricts the movement of the blank tube in the pushing direction of the plug,
and wherein the method for manufacturing a different thickness steel tube.
[Requested item 14]
　The squeezing the blank tube after the second ironing step, further comprising a drawing step
and wherein the method for producing a different thickness steel tube according to claim 13.
[Requested item 15]
　The blank tube is a seamless steel pipe
and wherein the method for producing a different thickness steel tube according to any one of claims 1 to 14.
[Requested item 16]
　Provided on one side of the longitudinal and enlarged portion and having a largest outer dimension when viewed in cross section perpendicular to the longitudinal direction;
　the enlarged portion the other side than when viewed along the longitudinal direction and provided, and the thickness is thin walled section than the enlarged portion;
includes a,
　an average value of the hardness of the enlarged portion H1, the average value of the hardness of the thin portion when the H2, H2> satisfy H1
different thickness steel tube, characterized in that.
[Requested item 17]
　The longitudinal direction than the thin portion when viewed along disposed on said other side than said thin portion further comprises a wall thickness thick-walled portion;
　the average value of the hardness of the thick portion and H3 ; when, H2> satisfy H1 ≧ H3
different thickness steel tube of claim 16 that is characterized.
[Requested item 18]
　The thin portion,
　　the thickest thin straight tube portion in the thin portion,
　　a first tapered portion to expand the outer shape the toward the enlarged portion with provided between the straight tube portion and the expanding portion,
　　a second tapered portion the wall thickness increases toward the thick portion together is provided between the straight tube portion and the thick portion
has a;
　an average value of the hardness of the first tapered portion H4, the straight the average value of the hardness of the tube portion H5, and the average value of the hardness of the second tapered portion when the H6, H5> H6 satisfy both equations of ≧ H3 and H5> H4> H1;
and wherein the different thickness steel tube of claim 17.
[Requested item 19]
　The thickness of the thin portion, when viewed along the longitudinal direction, characterized in that it partially thicker, the different thickness steel tube according to any one of claims 16-18.
[Requested item 20]
　Different thickness steel tube of claim 16, wherein the combination of the enlarged portion and the thin portion, characterized in that it symmetrically provided on the longitudinal ends.
[Requested item 21]
　Is arranged between a pair of the thin portion than said thin portion further comprises a wall thickness thick-walled portion;
　the average value of the hardness of the thick portion in the case of the H7, H2> satisfy H1 ≧ H7
that different thickness steel tube of claim 20, wherein.
[Requested item 22]
　And provided on one side of the longitudinal direction, said the thickest is thick-walled portion when viewed in cross section perpendicular to the longitudinal direction, and provided on the other side of the thick portion, the thick and the thickness is thin walled section than part, the provided;
　outer dimensions along the longitudinal direction be constant;
　the average value of the hardness of the thick portion H8, the average value of the hardness of the thin portion and H9 when, satisfy H9> H8
different thickness steel tube, characterized in that.
[Requested item 23]
　The thin portion, when viewed along a circumferential direction of the thin portion in a cross section perpendicular to the longitudinal direction, relative, and high hardness region thin wall thickness, hardness is thicker the thick low region has a rotationally symmetrical shape alternating along the circumferential direction
different thickness steel tube according to any one of claims 16-22, characterized in that.
[Requested item 24]
　Different thickness steel tube according to any one of claims 16 to 23, characterized in that the seamless steel pipe as a raw material.