[0001]The present invention is a mandrel, to bend and its manufacturing method and a manufacturing apparatus.
BACKGROUND
[0002]Steel, a method of performing an aluminum or mother tube bending a straight pipe metal such aluminum alloy to produce a curved pipe is known some in the past. Among these, rotary draw bending (Rotary Draw Bending), although large local strain to bend occurs, fast processing speed, is widely used as a bending process for producing a curved pipe efficiently.
[0003]
　5 (a) and 5 (b) is an explanatory diagram showing a situation of manufacturing a bent pipe 6 by rotating draw bending schematically and over time. Incidentally, it is taken as an example the case where the metal pipe is steel pipe in the following description.
[0004]
　Figure 5 (a) and as shown in FIG. 5 (b), rotating draw bending is a bending die (Bending die) 2, and the clamping die (cramping die) 3, a wiper (wiper) 4, a pressure-type ( It is carried out using a pressure die) 5. The rotary draw bending, gripping the ends of the axial direction of the mother tube 1 by the bending die 2 and the clamping die 3, by pressing a raw pipe 1 the bending die 2 rotates, the tensile load in the axial direction of the mother tube 1 perform bending while giving.
[0005]
　Bending die 2 has a groove 2a for guiding the bent inner scheduled portion 1a of the base pipe 1. Bending die 2 is rotatably arranged in two dimensions on the rotation center axis 2b around. The clamping die 3 by pressing the bent outer end portion 1b mother tube 1 is pressed against the bending die 2 a bent inner end 1c of the base pipe 1.
[0006]
　The clamping die 3 is rotatably arranged in two dimensions on the rotation center axis 2b around a bending die 2. Wiper 4 supports the bent inner scheduled portion 1a of the base pipe 1. Further, the pressure type 5, by pushing the bent outer scheduled portion 1d of the blank tube 1, pressing the bent inner scheduled portion 1a of the base pipe 1 to the wiper 4.
[0007]
　Mainly strain elongation in the axial direction is generated in the mother tube 1 during processing. Elongation strain amount of bending outer scheduled portion 1d is greater than the elongation amount of distortion of the bent inner portion to be 1a. Therefore, condition bent such bending speed and tensile force when not appropriate, beyond the bending elongation at break limit of the amount of strain blank pipe 1 of the outer portion to be 1d, blank pipe 1 is broken. It is important in rotary draw bending to reduce only the bending conditions can elongation strain in the bent outer scheduled portion 1d by appropriately selecting.
[0008]
(A) back booster (back booster) that push the blank tube 1 in the axial direction by 7, or
(b) bending tool moving the pressure type 5 at a higher speed than the second rotational speed to the base pipe feed direction
containing the that the tube 1 apply a compressive force in the axial direction is known as a means to reduce the elongation strain of the bent outer scheduled portion 1d blank tube 1.
[0009]
　For example post-processing such as tube hydroforming (Tube hydroforming) is sometimes further made to bend 6 produced by rotating draw bending. Relatively large load is continuously loaded in the bends 6 by a tube hydroforming.
[0010]
　Even mother tube 1 is not broken by a rotationally draw bending, when the total amount of the distortion amount generated newly by elongation strain amount and tube hydroforming already present in the bends 6 by rotating draw bending exceeds fracture limit, bent tube 6 is broken. The total amount is not a simple sum of the distortion amount, the total amount based on plastic mechanical principles. To prevent rupture of the curved pipe 6, it is effective to reduce the elongation strain amount generated mother tube 1 by rotating draw bending.
[0011]
　Previously, and when manufacturing a bent pipe 6 by rotating draw bending as a final product, when the strain amount applied to the bend 6 is not greater was often by rotary draw bending tube hydroforming after processing.
[0012]
　Therefore, heretofore in producing a curved pipe 6 by rotating draw bending of, inhibiting as much as possible under the condition that the bending outer scheduled portion 1d blank tube 1 is not broken, the flattening of the bending portion 9 attention has been paid to. Mandrel (also referred to as metal core or core) 8 has been used as an effective tool for this purpose.
[0013]
　The mandrel 8 is provided with a shank (shank) 8a, for example, a connection mechanism 8b such spherical bearing, the mandrel ball 8c is supported displaceably in two or three dimensions relative to the shank 8a by connecting mechanism 8b.
[0014]
　The mandrel 8 is arranged with a gap between the base pipe 1 inside the base tube 1. Figure 5 (a) and the mandrel 8 shown in FIG. 5 (b), has two connecting mechanism 8b and mandrel ball 8c. Two mandrels ball 8c of circular cross-section which is disposed at the distal end of the shank 8a inhibits flattened bend 9.
[0015]
　Patent Documents 1-3, a mandrel for use in rotary draw bending is disclosed.
CITATION
Patent Document
[0016]
Patent Document 1: JP-A-7-290156 JP
Patent Document 2: JP 2001-232421 Patent Publication
Patent Document 3: JP 2006-187785 JP
Summary of the Invention
Problems that the Invention is to Solve
[0017]
　Recently, high strength and thinning of the bent tube 6 are required in order to further weight reduction of the industrial products of the bent tube 6 as a material. Furthermore, small curvature radius reduction and thinning of the bending portion 9 of the bent tube 6 are required in order to reduce the size of the industrial products.
[0018]
　The present inventors have high strength, and consider produced by rotating draw bending the bent tube 6 having a bent portion 9 is small curvature radius and thin. As a result, as in the conventional, not only breaking due to local thinning of the bending outer 9b bent portion 9, it was found anew that wrinkles and seat Kagamo occurrence of bending inside 9a. Broken bent tube 6 is, of course, also bent tube 6 wrinkling buckling occurs, it can not be used as a final product material.
[0019]
　An object of the present invention, high strength or small curvature radius and the curved pipe having a bent portion which is thin, without causing fracture at the bending outside the bent portion, both the wrinkles and buckling at the bending inside the allowable range enjoyed a, it is to produce a rotating draw bending.
Means for Solving the Problems
[0020]
　The present inventors have made intensive studies in order to solve the above problems, finding A ~ C of listed were obtained in the following, further extensive investigations, and completed the present invention.
[0021]
(A) When producing a curved pipe 6 performs rotary draw bending the base tube 1 by using a conventional mandrel ball having a circular cross-section, the thinning and flattening of the bending portion 9 are in a trade-off relationship.
[0022]
　For example, if the installation position of the reference position from the bent portion 9 side of the mandrel 8 is moved forward in) (right direction in FIG. 5 (a)) enhancing the function of the mandrel 8, although the flattened bend 9 can be suppressed, bending breaking bending outer 9b parts 9 are likely to occur.
[0023]
　On the other hand, when it is retracted to the left in FIG. 5 (b) the installation position of the mandrel 8 from the reference position weakens the action of the mandrel, although the occurrence of fracture at the bending outside 9b bent part 9 can be suppressed, bending portion 9 flattened becomes remarkably.
[0024]
(B) instead of the conventional mandrel ball 8c shown in FIG. 5 (a) and 5 (b), in a cross section perpendicular to the axial direction at the axial center position of the mandrel ball, bending from the mandrel ball center straight tube top dimensions to the first position of the mandrel ball positioned opposite the outer scheduled portion is a predetermined amount smaller than the size of the to a second position of the mandrel ball positioned opposite from the mandrel ball center innermost scheduled portion bending straight tube the mandrel ball having a shape when used (hereinafter, also referred to as "asymmetric mandrel ball"), during rotation draw bending, a gap between the bent outer plan of the mandrel ball and base pipe can be increased than before.
[0025]
　This can suppress to the extent allowed wrinkles and buckling bending the bending while preventing the occurrence of fracture at the outer portion, generated in flattened and bent inside of the bend.
[0026]
Curved pipe manufactured using the (C) asymmetrical mandrel ball has both a high strength, the proper aspect ratio and thinning rate good level. Accordingly, this bent tube is then to it without performing secondary processing such as a tube hydroforming can be used as a product material, or may be a final product further performing secondary processing.
[0027]
　The present invention is as listed below.
(1) comprises a shank, a connecting mechanism rotatable in any direction by the spherical contact with the shank, a mandrel ball which is supported freely displaceable in two or three dimensions relative to the shank by the connecting mechanism a mandrel,
　and the connecting mechanism includes only one set combines the mandrel ball,
　in a cross section perpendicular to the axial direction at the axial center position of said mandrel ball,
　the mandrel ball passes through the mandrel ball center It has a first position and a second position where the first straight line is associated with the mandrel ball outer circumferential surface,
　from the mandrel ball center dimension L to the first position 1 dimensions and, to the second position from the mandrel ball center L 2 ratio of (L 1 / L 2 ) is 0.915 or more 0.976 or less, the mandrel.
[0028]
(2) in a cross section perpendicular to the axial direction at the axial center position of said mandrel ball, said mandrel ball is surrounded by the mandrel ball outer peripheral surface including a second straight line and the first position perpendicular to the first straight line has a first region, a second region surrounded by the mandrel ball outer peripheral surface including said second position and said second straight line, the mandrel according to item 1.
[0029]
(3) in a cross section perpendicular to the axial direction at the axial center position of said mandrel ball, the mandrel ball outer peripheral surface of the mandrel ball outer peripheral surface of the first region and the second region is continuously related to 1 or 2, wherein the mandrel described.
[0030]
(4) In the above cross-section perpendicular to the axial direction at the axial center position of the mandrel ball wherein the shape of the mandrel ball outer peripheral surface of the second region is a semi-circular mandrel according to 2 or 3 wherein.
[0031]
(5) has a groove for guiding a bent inner scheduled portion blank tube is a straight tube, the bending die and rotatable in two dimensions,
　bending the inner end of the base tube by pushing the bent outer end of the base pipe pressed against the bending die and a clamping die rotatable in two dimensions with the bending die,
　a wiper supporting the bending inner portions to be of the mother tube,
　the bending of the raw tube by pushing the bent outer scheduled portion of the raw tube using a pressure type for pressing the inner portion to be in the wiper,
　performs rotational draw bending to the base tube, a method for producing a curved pipe having a bent portion bent in two dimensions,
　one of the 1-4, wherein the mandrel crab, wherein the first position of the mandrel ball, said second position of said mandrel ball while positioned opposite the outermost portion to be bent of the mother tube is innermost expected bending of the base pipe so as to be positioned opposite the part, Performing said rotating draw bending arranged in the interior of the base pipe, the production method of the curved pipe.
[0032]
(6) performs the rotating draw bending while loading the compressive force of the mother tube in the axial direction, the production method of the curved pipe according to Section 5.
[0033]
(7) has a groove for guiding a bent inner scheduled portion blank tube is a straight tube, the bending die and rotatable in two dimensions,
　bending the inner end of the base tube by pushing the bent outer end of the base pipe pressed against the bending die and a clamping die rotatable in two dimensions with the bending die,
　a wiper supporting the bending inner portions to be of the mother tube,
　the bending of the raw tube by pushing the bent outer scheduled portion of the raw tube a pressure type for pressing the inner portion to be in the wiper
comprises a, performs rotational draw bending to the base tube, an apparatus for producing a curved pipe having a curved bend in two dimensions,
　further, the mother tube comprising a mandrel according to any one of 1 to 4, wherein arranged in the interior of,
　the mandrel, the first position of the mandrel ball, with located opposite the outermost portion to be bent of the straight pipe, the second largest of the mandrel ball But so as to be positioned opposite the innermost portion to be bent of the straight pipe, arranged is, the curved pipe manufacturing apparatus.
[0034]
(8) comprising means for loading a compressive force to the rotary draw bending the blank tube in the axial direction being made the machining apparatus for manufacturing a bent pipe according to item 7.
[0035]
(9) and curved bend in two dimensions, a bent tube made of steel with a straight pipe portion,
　the thickness of the bent portion t 1 and (mm), the thickness of the straight tube portion t 2 (mm) and then, the outer diameter of the straight tube portion D 1 when the (mm), the bending radius of the bent portion as R (mm), the bending angle of the bending portion and theta (°),
　t 2 / D 1 : 0.005
　~ 0.3, 　t 2 : 0.5 ~ 30, D 　1 : 15 ~ 700, R: 1D 1 ~ 6D 1 , 　theta: 0 ~ 180, 　maximum thinning rate: 14. 5%, 　the maximum aspect ratio: 8.0% or less, 　the hardness ratio immediately after bending: 8-50% is, bent tube. 　However, 　maximum thinning rate: {(T 2 -T 1

) / T 2 } × 100 maximum value (%),
　the maximum aspect ratio: the bent portion {(maximum outer diameter - minimum outer diameter) / D 1 maximum of} × 100 (%),
　flexural immediately after the hardness ratio :( bend bending 1mm pitch L cross-section of the central portion of the outside to the longitudinal direction of the tube, the average value of values measured five points in Hv (10kg)) - (tube length of L cross-section of the straight tube portion 1mm pitch to-side direction, Hv average of five points measured values (10kg))} / (1mm pitch L section of straight pipe section to the pipe longitudinal direction, Hv (10 kg) average value of values measured 5 points at )
it is.
The invention's effect
[0036]
　The present invention, wrinkles and bends in thin wall, while preventing the occurrence of fracture at the bending outside the bent portion, and the flattening of the cross section of the bending portion, bending the inside with a bending portion of the high-strength or small curvature radius any and the occurrence of buckling is suppressed to an acceptable level, it can be produced cold by rotary draw bending.
[0037]
　Bent tube according to the present invention has both a high strength, the proper aspect ratio and thinning rate good level. Therefore, thereafter, to it can be used as a product material without performing the secondary processing such as tube hydroforming, it may be a final product further performing secondary processing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038]
[1] Figure 1 (a) is a side view of a mandrel according to the present invention, FIG. 1 (b) is an A-A sectional view in FIG. 1 (a).
FIG. 2 is an explanatory diagram showing the beginning of the rotary draw bending.
FIG. 3 is an explanatory view showing the state where the end of the rotary draw bending.
[4] FIG. 4 is a graph showing the results of a thinning rate.
[5] FIGS. 5 (a) and 5 (b) is an explanatory diagram showing a situation of manufacturing a bent pipe by rotating draw bending schematically and over time.
DESCRIPTION OF THE INVENTION
[0039]
　The present invention will be described. In the following description, taking the case where blank tube is high-tensile steel pipe having a tensile strength of 980MPa class, i.e. 980 ~ 1179MPa example. The present invention is not limited to the high-tensile steel. Mother pipe is steel pipe having a tensile strength of less than 980 MPa, stainless steel, industrial pure aluminum tube, an aluminum alloy tube, commercially pure titanium tubes, or even in the case of titanium alloy tube, the present invention applies equally.
[0040]
1. The mandrel 10 according to the present invention
　1 (a) is a side view showing the mandrel 10, 1 (b) is an A-A sectional view in FIG. 1 (a), in the axially central position of the mandrel ball 16 It shows the cross-section. Figure 2 is an explanatory diagram showing the beginning of the rotary draw bending. Further, FIG. 3 is an explanatory view showing the state where the end of the rotary draw bending.
[0041]
　As shown in FIG. 1 (a), the mandrel 10 includes a shank 14, and the connecting mechanism 15, the mandrel ball 16. Connection mechanism 15 is provided on the shank 14. Connecting mechanism 15 is rotatably arranged in an arbitrary direction by a spherical contact with the shank 14.
[0042]
　The mandrel ball 16 is supported in the connection mechanism 15. The mandrel ball 16 is rotatably arranged relative to the shank 14 in the direction of the two-dimensional or three-dimensional by the connection mechanism 15. Maximum value of the displacement angle of the mandrel ball 16 against the shank 14 is 40 °. The mandrel 10 is disposed with a gap between the base pipe 11 in the interior of the base tube 11 shown in FIG.
[0043]
　Shank 14, the material of the connecting mechanism 15 and mandrel ball 16 may be any conventional material which is customary for this type of mandrel, for example, alloy tool steel is used.
[0044]
　As shown in FIGS. 2 and 3, the mandrel 10 is, when manufacturing a bent pipe 13 having a bent portion 12-1 performs rotational draw bending the blank tube 11, the bending is disposed inside the base pipe 11 used to suppress the flattening of the cross section of the section 12-1.
[0045]
　As shown in FIG. 1 (b), in a cross section perpendicular to the axial direction at the axial center position of the mandrel ball 16, the mandrel ball 16, first line m passing through the mandrel ball center 17 coincides with the shank center 14a is having a first position 19 and second position 20 to associate with the mandrel ball outer peripheral surface 21.
[0046]
　Dimension L from the mandrel ball center 17 to the first position 19 1 and the dimension L from the mandrel ball center 17 to the second position 20 2 ratio of (L 1 / L 2 ) is, at 0.915 to 0.976 Yes, preferably from 0.915 to 0.953. That is, the dimension L 1 dimension L 2 2.4 ~ 8.5% less than, preferably 4.7 to 8.5% smaller. Thus, the mandrel ball 16 are asymmetrical mandrel ball.
[0047]
　By mandrel ball 16 are asymmetrical mandrel ball, the gap between the bending outer scheduled portion 11d of the mandrel ball 16 and base pipe 11 can be increased than before. Thus, while preventing the occurrence of fracture at the bending outside 12b of the bent portion 12-1 of the bent tube 13, and the flattening of the cross section of the bent portion 12-1, the occurrence of wrinkles and buckling at the bending inside 12a both can be suppressed to an acceptable degree.
[0048]
　As shown in FIG. 1 (b), in a cross section perpendicular to the axial direction at the axial center position of the mandrel ball 16, the mandrel ball 16 includes a second straight line n and the first position 19 which is perpendicular to the first straight line m having a first region 22 which is surrounded by the mandrel ball outer peripheral surface 21. Furthermore, the mandrel ball 16 has a second region 23 which is surrounded by the mandrel ball outer peripheral surface 21 including a second straight line n and a second position 20. In FIG. 1 (b), given the right up hatching in the first region 22 are denoted by the right down hatching in the second region 23.
[0049]
　As shown in FIG. 1 (b), the mandrel ball outer peripheral surface 21 of the first region 22, the mandrel ball outer peripheral surface 21 of the second region 23 is continuously connected smoothly in order to suppress the deformation of the bent tube 13 and it is desirable that. However, the present invention is not limited to this.
[0050]
　The shape of the mandrel ball outer peripheral surface 21 of the first region 22, the gap between the bending outer scheduled portion 11d of the base tube 11 may be any shape that can be expanded than the bending inner scheduled portion 11a of the base pipe 11. Thus, for example a step or depressions with the mandrel ball outer peripheral surface 21 of the first region 22, it is acceptable to present the meeting position between the mandrel ball outer peripheral surface 21 of the second region 23.
[0051]
　Further, in a cross section perpendicular to the axial direction at the axial center position of the mandrel ball 16, the mandrel ball outer peripheral surface 21 of the first region 22, the curvature need not be constant curve.
[0052]
　The axial dimension L of the mandrel ball 16 3 is the outer diameter of the mother tube 11 D 1 when the (mm), if the range of the small diameter tube (Fai25.4 ~ Fai114.3), 0.3D 1 0.5D ～ 1 it is desirable that.
[0053]
　Mandrel axial distance L to the reference position, which will be described later, from the position of the leading end of the mandrel ball 16 4 , if the range of the small diameter tube (Fai25.4 ~ Fai114.3), 0.5 D 1 ~ 0.7D 1 it is found while preventing the occurrence of fracture at the bending outside 12b of the bent portion 12-1, both the flattened cross section of the bent portion 12-1, bending wrinkles and buckling at the inner side 12a It preferred for suppressing the acceptable degree.
[0054]
　As shown in FIG. 1 (b), in a cross section perpendicular to the axial direction at the axial center position of the mandrel ball 16, the shape of the mandrel ball outer peripheral surface 21 of the second region 23, the inner surface of the bend inside 12a of the bend 13 since a shape along the shape, it is desirable for example semicircular.
[0055]
　In Figure 2, the mandrel 10, with the first position 19 of the mandrel ball 16 is positioned opposite the outermost scheduled portion 11e bend mother pipe 11, the second position 20 of the mandrel ball 16, the straight pipe 11 bent top so as to be positioned opposite the inner side portion to be 11f, it is arranged. However, the present invention is not limited to this embodiment.
[0056]
　Specifically, if the cross-section shown in FIG. 1 (b), i.e., the size of the central angle of the mandrel ball center 17 in a cross section perpendicular to the axial direction at the axial center position of the mandrel ball 16 to 0 °, the mandrel 10 a range of ± 30 ° at the central angle relative to the straight tube 11, desirably be disposed deviated within ± 15 °, an effect is obtained of the present invention.
[0057]
　Configuration other than the above-described mandrel 10, may be the same as the configuration that is customary for this type of mandrel, so well known to those skilled in the art, the description thereof is omitted.
[0058]
2. Manufacturing apparatus 30 according to the present invention
　the manufacturing apparatus 30, as shown in FIGS. 2 and 3, by performing a rotating draw bending the blank tube 11, producing a curved pipe 13 having a bent portion 12-1 bent in two dimensions it is a device that.
[0059]
　The tensile strength of the base pipe 11 If it is more than 980 MPa, the effect of the present invention is more remarkable. If the tensile strength of the base pipe 11 is not less than 980 MPa, bending flattened cross-section during machining bent portion 12-1, fracture at the bending outside 12b of the bent portion 12-1, and the bending inside 12a of wrinkles the occurrence of buckling is because becomes remarkable.
[0060]
　Manufacturing apparatus 30 includes as in the conventional manufacturing apparatus shown in FIGS. 5 (a) and 5 (b), the bending die 31, the clamping die 32, a wiper 33, a pressure type 34. Bending die 31 has a groove 31a. Groove 31a guides the bent inner scheduled portion 11a of the base pipe 11. Bending die 31 is rotatably arranged in two dimensions on the rotation center axis 31b around.
[0061]
　The clamping die 32 is pressed by pressing the bent outer end 11b of the base pipe 11 to the bending die 31 to the inner end portion 11c bend mother pipe 11. The clamping die 32 is rotatably arranged in a two-dimensional with the bending die 31 to the rotation center axis 31b around.
[0062]
　Wiper 33 supports the bent inner scheduled portion 11a of the base pipe 11. Furthermore, the pressure die 34 by pressing the bent outer scheduled portion 11d of the base pipe 11 presses the bent inner scheduled portion 11a of the base pipe 11 to the wiper 33.
[0063]
　Furthermore, the manufacturing apparatus 30 includes a mandrel 10. The mandrel 10 is disposed with a gap between the base pipe 1 inside the base pipe 11.
[0064]
　The mandrel 10 is in the reference position within the base pipe 11, the first position 19 of the mandrel ball 16, while located opposite the outermost scheduled portion 11e bend mother pipe 11, the second position 20 of the mandrel ball 16 , so as to be positioned opposite the innermost scheduled portion 11f bending blank pipe 11 are arranged.
[0065]
　Here, the "reference position", in the rotation plane of the bending tool 31 in the rotational draw bending start shown in FIG. 2, with respect to the feeding direction of the mother tube 11, the linear portion and distal R portion of the shank 14 is associated R stop position means that matches the rotation axis 31b of the bending die 31.
[0066]
　Manufacturing apparatus 30, it comprises a back booster 35 pushing the blank tube 11 in the axial direction, or, by the pressure die 34 at a higher than the rotational speed of the bending tool 31 speed moved blank tube feeding direction, bending during processing to the base tube 11 may be given a compressive force in the axial direction.
[0067]
3. The manufacturing method according to the present invention
　the manufacturing method according to the present invention is carried out by the manufacturing apparatus 30. In accordance with the present invention, the bending tool 31 described above, the clamping die 32, a wiper 33, a pressure mold 34 and mandrel 10, bend curved in two dimensions by performing the rotation draw bending a straight pipe 11 section 12 producing curved pipe 13 having a 1.
[0068]
　At the start of production of the bent tube 13 shown in FIG. 2, the mandrel 10 is at the reference position within the base pipe 11, the first position 19 of the mandrel ball 16, located opposite the outermost scheduled portion 11e bend mother pipe 11 while, the second position 20 of the mandrel ball 16, so as to be positioned opposite the innermost scheduled portion 11f bending blank pipe 11 are arranged.
[0069]
　Therefore, the gap between the bending outermost scheduled portion 11e bending mandrel ball 16 and base pipe 11 during processing can be increased than before. Thus, while preventing the occurrence of fracture at the bending outside 12b of the bent portion 12-1 of the bent tube 13, and the flattening of the cross section of the bent portion 12-1, the occurrence of wrinkles and buckling at the bending inside 12a both can be suppressed within an allowable range.
[0070]
　The axial dimension L of the mandrel ball 16 3 is, L 3 = 0.3D 1 ~ 0.5 D 1 is preferably a mandrel ball axial distance L of the reference position and the leading end of the mandrel ball 16 4 is , L 4 = 0.5 D 1 ~ 0.7D 1 is desirably.
[0071]
　Furthermore, during the bending, pushing the blank tube 11 in the axial direction by the back booster 35, by moving the pressure-type 5 into base pipe feed direction at a higher than the rotational speed of the bending tool 2 speed, the base tube 11 it may provide a compressive force in the axial direction.
[0072]
4. Bend according to the present invention
　bent tube 13 manufactured by the manufacturing method and manufacturing apparatus according to the present invention described above, at least one have the bent portions 12-1 bent in two dimensions. Steel tensile strength in a longitudinal direction of the straight tube portion is desirably not less than 980 MPa, it is further desirable that 980 ~ 1179MPa.
[0073]
　Bends 13, the wall thickness of the bent portion 12-1 of the bent tube 13 t 1 and (mm), the thickness of the bent portion 12-1 except the straight tube portion 12-2 t 2 and (mm), the outer the diameter D 1 and (mm), when the bending radius of the bent portion 12-1 and R (mm), where the bending angle of the bent portion 12-1 and theta (°), further having the characteristics listed below .
[0074]
(4-1) t 2 / D 1 : 0.005 ~ 0.3 (4-2) t 2 : 0.5 ~ 30 (4-3) D 1 : 15 ~ 700 (4-4) R: 1D 1 ~ 6D 1 (4-5) theta: 0 ° ~ 180 ° (4-6) the maximum thinning rate: 14.5% or less 　maximum thinning rate, {(t 2 -t 1 ) / t 2 } × determined as the maximum of 100 (%). 8.0% or less: (4-7) Maximum aspect ratio 　- {(minimum outer diameter maximum outer diameter) / D Maximum flattening the bend 12-1 1 Largest} × 100 (%) It is obtained as a value. (4-8) Hardness ratio immediately after bending: 8-50%

　Hardness ratio immediately after bending, (average value of bending 1mm pitch L cross-section of the central portion of the outer 12b to the tube longitudinal direction of the bending portion 12-1 was measured five points in Hv (10 kg) value) - (straight tube L sectional 1mm pitch to the longitudinal direction of the tube parts 12-2, Hv average of five points measured values ​​(10kg))} / (1mm pitch L cross section of the straight pipe portion 12-2 to the longitudinal direction of the tube, Hv determined as an average of five points measured value (10 kg)).
[0075]
　Thus, the curved pipe 13, combines these features, in particular, combines a high strength, the proper aspect ratio and thinning rate good level. Thus, bent tube 13, to directly even without secondary processing such as a tube hydroforming can be used as a product material, or may be a finished product by performing the secondary processing.
Example
[0076]
　5 (a) and 5 rotating draw bending device disposed in the reference position of a conventional mandrel 8 shown in (b) (conventional example 1),
　conventional ball shown in FIGS. 5 (a) and 5 (b) type rotary draw bending apparatus disposed in a position retracted from the reference position the mandrel 8 of the (conventional example 2),
　rotary draw bending apparatus using a mandrel 10 according to the present invention shown in FIGS. 1-3 (invention examples 1 to 3)
using each, tensile strength of the base pipe 1, 11: 980 MPa, the thickness t of the straight tube portion 12-2 2 : 1.0 mm, outer diameter of the straight tube portion 12-2 D 1 : 38.1 mm, bending radius of the bent portion 12-1,9 R: 76.2mm, the bending angle of the bent portion 12-1,9: under conditions of 90 °, to produce a bent tube 13,6 shown in FIG. 3, 5 (b) the case was analyzed by FE simulation, the maximum flattening of the bending portion 12-1,9, up, down Rate and bending stiffness ratio immediately, was determined by the method described above.
[0077]
　In Table 1, the maximum aspect ratio: 8.0% or less and the maximum thinning rate: and the case where 14.5% or less was evaluated as good.
[0078]
　The results of the thinning rate with illustrated graphically in FIG. 4, Table 1 shows the results of maximum flattening and maximum thinning rate.
[0079]
[Table 1]

[0080]
　In Conventional Example 1, since the maximum thinning rate at the time of rotation draw bending is large, even without cracks occur in rotating draw bending, when after rotating draw bending such as secondary processing tube hydroforming, etc., there is a possibility that cracking is generated in the curved pipe.
[0081]
　Conventional Example 2 is a known method of reducing the maximum thinning rate in the rotary draw bending. Conventional Example 2, although certainly maximum thinning rate can be reduced, and maximum aspect ratio is deteriorated, the resulting bend is not performed secondary processing hydroforming etc. Failure to use as a product.
[0082]
　In contrast, the present invention Examples 1-3, the maximum aspect ratio: 7.5 to 7.9%, the maximum thinning rate: a 13.7 to 14.3%, and the prevention of an increase in the maximum thinning rate can both prevent deterioration of the maximum aspect ratio at a high level.
[0083]
　It bends 13 of the present invention Examples 1-3, combines a high strength, the proper aspect ratio and thinning rate good level. Thus, bent tube 13, it can be subsequently used as the raw product material without performing the secondary processing such as tube hydroforming, or may be a final product further performing secondary processing .
DESCRIPTION OF SYMBOLS
[0084]
1 blank tube
1a bent inward scheduled portion
1b bent outer end
1c bent inner end
1d bent outwardly scheduled portion
2 bending die
2a groove
2b rotation axis
3 clamping die
4 wiper
5 pressure-type
six songs pipe
7 back booster
8 mandrels
8a shank
8b connection mechanism
8c mandrel ball
9 bent portion
9a bent inner
9b bent outer
mandrel according to 10 the invention
11 base pipe
11a bent inward scheduled portion
11b bent outer end portion
11c bent inner end
11d bent outward scheduled portion
bending 11e outermost scheduled portion
11f bent innermost scheduled portion
12a bent inward
12b bent outwardly
13 tracks tube
14 Shank
14a shank center
15 connecting mechanism
16 mandrel ball
17 mandrel ball center
19 first position
20 the second position
21 the mandrel ball periphery surface
22 first region
23 second region
30 manufacturing apparatus
31 bending tool
31a groove
31b rotational center shaft
32 the clamping die
33 wiper
34 pressure type
35 back booster
m first straight line
n second linear

WE CLAIM

A mandrel comprising a shank, a connecting mechanism rotatable in any direction by the spherical contact with the shank, a mandrel balls supported displaceably in two or three dimensions relative to the shank by the connecting mechanism Te,
　in a cross section perpendicular to the axial direction at the axial center position of said mandrel ball,
　the mandrel ball has a first position and a second position where the first straight line passing through the mandrel ball center is associated with the mandrel ball outer peripheral surface together,
　the dimension L from the mandrel ball center to the first position 1 and the dimension L from the mandrel ball center to the second position 2 ratio of (L 1 / L 2 ) is 0.915 to 0.976 in it, the mandrel.
[Requested item 2]
　In a cross section perpendicular to the axial direction at the axial center position of said mandrel ball, said mandrel ball, a first region surrounded by the mandrel ball outer peripheral surface including the first position and the second straight line perpendicular to the first straight line When, a second region surrounded by the mandrel ball outer peripheral surface including said second position and said second straight line, the mandrel according to claim 1.
[Requested item 3]
　In a cross section perpendicular to the axial direction at the axial center position of said mandrel ball, the mandrel ball outer peripheral surface of the mandrel ball outer peripheral surface of the first region and the second region leads to a continuous, according to claim 1 or 2 the mandrel.
[Requested item 4]
　Wherein in a cross section perpendicular to the axial direction at the axial center position of the mandrel ball, the shape of the mandrel ball outer peripheral surface of the second region is a semi-circular mandrel according to claim 2 or 3.
[Requested item 5]
　Has a groove for guiding a bent inner scheduled portion blank tube is a straight tube, the bending die and rotatable in two dimensions,
　the bending bending inner end of the base tube by pushing the bent outer end of the base pipe pressing the mold, the clamping die rotatable in two dimensions with the bending die,
　a wiper supporting the bending inner portions to be of the mother tube,
　bent inward scheduled portion of the raw tube by pushing the bent outer scheduled portion of the raw tube using a pressure-type pressing the wiper,
　performs rotational draw bending to the base tube, a method for producing a curved pipe having a curved bend in two dimensions,
　in any one of claims 1 to 4, the mandrel, wherein the first position of the mandrel ball, said second position of said mandrel ball while positioned opposite the outermost portion to be bent of the raw tube is the innermost portion to be bent of the mother tube as located opposite, before Performing said rotating draw bending arranged in the interior of the base pipe, the manufacturing method of the bent tube.
[Requested item 6]
　Performing said rotating draw bending while loading the compressive force in the axial direction on the raw tube method for producing a curved pipe according to claim 5.
[Requested item 7]
　Has a groove for guiding a bent inner scheduled portion blank tube is a straight tube, the bending die and rotatable in two dimensions,
　the bending bending inner end of the base tube by pushing the bent outer end of the base pipe pressing the mold, the clamping die rotatable in two dimensions with the bending die,
　a wiper supporting the bending inner portions to be of the mother tube,
　bent inward scheduled portion of the raw tube by pushing the bent outer scheduled portion of the raw tube a pressure-type pressing the wiper
comprises a by performing rotating draw bending to the base tube, an apparatus for producing a curved pipe having a bent portion bent in two dimensions,
　further, the interior of the base pipe comprising a mandrel according to any one of claims 1 to 4 arranged,
　said mandrel, said first position of said mandrel ball, with located opposite the outermost portion to be bent of the straight pipe, said mandrel the second position of the ball , So as to be positioned opposite the innermost portion to be bent of the straight pipe, arranged is, the curved pipe manufacturing apparatus.
[Requested item 8]
　Comprising means for loading a compressive force to the rotary draw bending the blank tube in the axial direction being made the machining apparatus for manufacturing a bent pipe according to claim 7.
[Requested item 9]
　A curved bend in two dimensions, a bent tube made of steel with a straight pipe portion,
　the thickness of the bent portion t 1 and (mm), the thickness of the straight tube portion t 2 (mm) and then, the outer diameter of the straight tube portion D 1 and (mm), the bending radius of the bent portion as R (mm), the bending angle of the bent portion in the case of the theta (°),
　t 2 / D 1 : 0.005
　~ 0.3, 　t 2 : 0.5 ~ 30, D 　1 : 15 ~ 700, R: 1D 1 ~ 6D 1 , 　theta: 0 ~ 180, 　maximum thinning rate: 14.5% or less , 　the maximum aspect ratio: 8.0% or less, 　the hardness ratio immediately after bending: 8-50% is, bent tube. 　However, 　maximum thinning rate: {(T 2 -T 1

) / T 2 } × 100 maximum value (%),
　the maximum aspect ratio: the bent portion {(maximum outer diameter - minimum outer diameter) / D 1 maximum of} × 100 (%),
　flexural immediately after the hardness ratio :( bend bending 1mm pitch L cross-section of the central portion of the outside to the longitudinal direction of the tube, the average value of values measured five points in Hv (10kg)) - (tube length of L cross-section of the straight tube portion 1mm pitch to-side direction, Hv average of five points measured values (10kg))} / (1mm pitch L section of straight pipe section to the pipe longitudinal direction, Hv (10 kg) average value of values measured 5 points at )
it is.