Technical field
[0001]The present invention, hardness prediction method and the steel hardness of cold working parts - about equivalent plastic strain curve acquisition method.
BACKGROUND
[0002]In the processing of cold working parts including the plate forging, knowing the mechanical properties of the material is important on the work process design. Work hardening characteristics, which is one of mechanical properties of the material, the stress of the material - can be obtained based on the strain curve, the greater the work hardening as plastic strain applied to the material is large material. However, when molded parts by cold working, since plastic strain in the interior of the material after cold working is not uniform, the hardness distribution occurs therein. Therefore, a method to accurately obtain the hardness of any region of cold working parts has been demanded.
[0003]
　For example, Patent Document 1, provided with a depression in the cylindrical test piece, depression effect of friction by filling the liquid lubricant by performing cylinder compression test at least the state in, the relationship between the strain and the hardness of the material method of measuring is disclosed.
CITATION
Patent Document
[0004]
Patent Document 1: JP Hei 7-333127
Summary of the Invention
Problems that the Invention is to Solve
[0005]
　However, in the method of Patent Document 1, the aspect ratio of the specimen to prevent buckling during compression of the cylindrical specimen is limited, added strain and aspect ratio of the test piece exceeds 1.0 it is difficult. Also, usually, because of one specimen can only be obtained plastic strain for the amount of one compression (strain amount), to obtain a relationship between the acquired a plastic strain and strain hardness of the material to a plurality of compression amount , it is necessary to perform a plurality of times to a compression test by changing the amount of compression. Furthermore, it is difficult to create a cylinder compression test pieces from sheet steel.
[0006]
　The present invention has been made in view of the above problems, it is an object of the present invention obtains a plastic strain for the amount of compression by the compression test of one, the relationship between the strain and the hardness of the material capable of obtaining a, it is to provide a new and improved hardness prediction method of cold working parts.
Means for Solving the Problems
[0007]
　In order to solve the above problems, according to an aspect of the present invention, there is provided a hardness estimation method of cold working parts, the mounting table of the test specimen is placed, at the contact surface is a curved surface in contact with the test piece using a certain punch, a test piece placed on the table is compressed by a punch to create a hardness measurement test piece having a recess having a shape corresponding to the shape of the contact surfaces of the punch, the recess the direction in which the plate thickness is changed as the measurement direction, by measuring the hardness of the hardness measurement test specimen in a plurality of hardness measurement positions of the measurement direction, to calculate the strain equivalent plastic hardness measurement test specimen by numerical analysis, the hardness measurement based on the hardness equivalent plastic strain and at the position, hardness - acquires the equivalent plastic strain curve, the equivalent plastic strain value of the cold-working parts calculated by numerical analysis, hardness - based on equivalent plastic strain curve, calculates It has been cold-worked Identifying a hardness from equivalent plastic strain value of any portion of the article, hardness estimation method of cold working component is provided.
[0008]
　Specimens may be flat.
[0009]
　Hardness measurement test piece, while constraining the specimen plate width direction, may create the test pieces were compressed by the punch.
[0010]
　Hardness test piece for measurement may be made to have a strain distribution comprises a large strain region than uniform elongation obtained by uniaxial tensile test.
[0011]
　Hardness test piece for measurement is generated as equivalent plastic strain has a strain distribution comprises a strain region becomes greater than 1.0.
[0012]
　Hardness measurement position may be set at a predetermined interval in the measurement direction from the center of the recess portion of the hardness measurement test specimen.
[0013]
　Specimen is preferably set to cold working parts of the same material.
[0014]
　In order to solve the above problems, according to another aspect of the present invention, the steel hardness - a equivalent plastic strain curve acquisition method, the mounting table of the test piece is placed in contact with the test piece by using the punch contact surface is a curved surface, the test piece placed on the table is compressed by a punch to create hardness measurement test piece having a recess having a shape corresponding to the shape of the contact surface of the punch and, the direction in which the plate thickness is changed as the measurement direction in the recess, measured hardness hardness test piece for measurement in a plurality of hardness measurement positions of the measurement direction, by numerical analysis strain equivalent plastic hardness measurement test specimen calculated and, based on the hardness and equivalent plastic strain at each hardness measurement position, hardness - get equivalent plastic strain curve, steel hardness - equivalent plastic strain curve acquisition method is provided.
The invention's effect
[0015]
　According to the present invention described above, one obtains the strain equivalent plastic against the amount of compression by compression test, it is possible to obtain the relationship between the hardness of the material equivalent plastic strain.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016]
FIG. 1 is a flow chart showing a hardness estimation method of cold working component according to an embodiment of the present invention.
FIG. 2 is a schematic side view and a schematic plan view showing a configuration example of a jig for making a hardness measurement test piece according to the embodiment.
It is an explanatory diagram showing [3] and the pressing before the test piece by punching, test piece after pressing by the punch and (hardness measurement test specimen). It should be noted that the present drawing is an image view that was created on the basis of the photograph.
FIG. 4 is a schematic side view and a schematic plan view showing another configuration example of the jig for creating a hardness measurement test piece according to the embodiment.
[5] when creating a hardness measurement test specimen by a jig of Figure 2 the plate width direction of the test piece in a state of not constraining, and pressing the test piece before the by punching, test piece after the pressing by the punch (hardness it is an explanatory view showing a test piece for measurement) and. It should be noted that the present drawing is an image view that was created on the basis of the photograph.
It is an explanatory diagram showing a hardness measurement position of FIG. 6 Hardness test piece for measurement. It should be noted that the present drawing is an image view that was created on the basis of the photograph.
Is an explanatory view showing an equivalent plastic strain distribution in the region A in Fig. 7 Fig.
[8] Hardness - is an explanatory view showing an example of equivalent plastic strain curve.
[9] Hardness was obtained in the embodiment of FIG. 8 - the equivalent plastic strain curve, the hardness obtained by rolling - an explanatory diagram showing the equivalent plastic strain trendline.
DESCRIPTION OF THE INVENTION
[0017]
　Reference will now be described in detail preferred embodiments of the present invention. In the specification and the drawings, components having substantially the same function and structure are a repeated explanation thereof by referring to the figures.
[0018]
　<1. Overview>
　First, an outline of hardness estimation method of a cold-working component according to an embodiment of the present invention. The hardness estimation method of cold working part according to the present embodiment, first, to implement the single compression test for one test specimen, to create a hardness measurement test piece having a plastic strain distribution. Then, based on the measured hardness of hardness measurement test specimen that was created by a plurality of hardness measurement positions, strain equivalent plastic hardness measurement test specimen was determined by the hardness and numerical measured hardness - equivalent plastic strain curve to get. Here, the plastic strain is a vector quantity having a magnitude and direction, the orthogonal coordinate system, x-direction, y-direction, and the normal strain is the change in length in the z-direction, xy plane, yz plane, zx plane consisting of six components of shear strain is a change in the angle of. In this embodiment, based on the relationship of equivalent plastic strain and hardness was converted into a scalar quantity of only plastic strain magnitude, to predict the hardness. Hardness at any point cold working part calculates the equivalent plastic strain value of the cold working parts by numerical analysis, hardness - from equivalent plastic strain curve by identifying the hardness corresponding to the equivalent plastic strain It can be estimated.
[0019]
　The hardness estimation method of cold working component according to the present embodiment, the hardness measurement test piece having a plastic strain distribution by compression test one can easily create, one hardness from the hardness measuring test piece - it is possible to obtain the equivalent plastic strain curve. Further, the hardness estimation method of cold working component according to the present embodiment, in order to obtain the plastic strain distribution of a flat test piece as described later, is also applicable to thin steel sheet. Hereinafter, the hardness estimation method of cold working part according to the present embodiment will be described in detail.
[0020]
　<2. Hardness estimation method of cold working part>
　below with reference to the flow chart illustrating the hardness estimation method of cold working part according to the present embodiment shown in FIG. 1, illustrating the process of hardness estimation method of a cold-working parts.
[0021]
　[2-1. Creation] Hardness test pieces for measuring
　the hardness estimation method of cold working component according to the present embodiment, the hardness relates to materials for cold working part - to get the equivalent plastic strain curve, as shown in FIG. 1, creating a hardness measurement test specimen (S110). Punch hardness measurement test piece, the mounting table of the test piece is placed, with the punch contact surface is a curved surface which contacts the test strip, placed on the base material in a test stand (test piece) in is created by compression. The shape of the test piece, since the shape of the pre-compression of the specimen can be carried out numerical analysis for hardness measurement test specimen if known, are not particularly limited. Particular ease of shape of the test piece, to create a hardness measurement test specimen in a state of restraining the test strips, considering such, test strip is preferably flat planar shape is rectangular. In the following, the test strip will be described as a flat plate. The material of the specimen, the same as the material of the cold working parts to be predicted hardness. For example, when subjecting certain steel cold working, test specimens, steel sheets used for the processing, i.e., made from the same steel sheet prior to processing.
[0022]
　Hardness test piece for measurement is generated by the jig 100 as shown in FIG. 2, for example. Jig 100, as shown in FIG. 2, the test piece 10 while being placed, a die 110 for restraining the placed test piece 10 in the plate width direction (X direction), constrained to the die 110 and the support members 121 and 123 for holding the test piece 10 from above, consisting of a punch 130 that presses the test piece 10 from above.
[0023]
　Die 110 includes a pair of wall portions 111 and 113, made of flat portion 115. has a cross-section of substantially U-shaped. A pair of wall portions 111 and 113, a plate width substantially the same interval of the test piece 10 faces, constraining the specimen 10 in the plate width direction (X direction). Planar portion 115 is located between the pair of walls 111 and 113, and serves as a mounting base test piece 10 is placed. That is, the die 110 according to this embodiment has a groove extending in the longitudinal direction (Y-direction) a plate width substantially the same width of the test piece 10. When the test piece 10 is placed along the groove, the plate width direction is restricted by the die 110. Use In jig 100 shown in FIG. 2, a pair of wall portions 111 and 113 for restraining the plate width direction of the test piece 10, a die 110 which are integrally formed with the planar portion 115 for placing the test piece 10 but had the shape of a jig 100 for creating a hardness measurement test specimen is not limited to such an example.
[0024]
　Pressing members 121 and 123 hold the both longitudinal ends of the installed specimen 10 to the die 110 from above. Both ends of the test piece 10 by the flat portion 115 and the support members 121, 123 of the die 110 is fixed sandwiched thickness direction (Z-direction). At this time, the die 110 and the support members 121 and 123, in a state sandwiching the ends of the test piece 10 is fixed by, for example, bolts (not shown.) Or the like. The test piece 10 by the pressing member 121, 123 and die 110 is fixed to the plate thickness direction, it is possible to suppress the warping of the test piece 10 when it is pressed by the punch 130.
[0025]
　Punch 130 presses the specimens 10 placed on the die 110. Punch 130, contact surface 131 is formed into a curved surface in contact with the test piece 10. For example the punch 130 shown in FIG. 2, the contact surface 131 is formed by the outer peripheral surface of the radius of curvature R, it has a plate width substantially the same width of the test piece 10 is formed as a member having a substantially semicircular plate shape. Punch 130 are opposed to the contact surface 131 on the test piece 10, in a state where the longitudinal direction is made to correspond in the circumferential direction and the test piece 10 of the contact surface 131, presses the test strip 10 between the pressing member 121, 123 . As a result, the plate-like test piece 10 as shown in the upper Figure 3, the hardness measurement test piece 20 having a recess 21 corresponding to the shape of the contact surface 131 of the punch 130, as shown in FIG. 3 the lower side is formed It is.
[0026]
　When creating a hardness measurement test specimen by using a jig 100 shown in FIG. 2, while restraining the test piece 10 in the plate width direction by the wall portion 111, 113 of the die 110, the plate width of the test piece 10 substantially punch 130 having the same width is pressed against the test piece 10. Punch 130 pushes the test strip 10 enters into the groove of the die 110 to form a recess portion 21 to the test piece 10. By forming such a jig 100 recessed part 21 to the test piece 10 using a test piece 10 when the punch 130 is pressed will not deform in the plate width direction, the recessed portion 21 formed, as shown in FIG. as shown in 3 it can be assumed to have been uniformly compressed in the plate width direction. That is, it is possible to obtain a hardness measurement test specimen 20 strain uniform plastic in a plate width direction is imparted. By creating such a hardness measurement test piece 20, by issuing a surface not affected by the previous hardness measurement by grinding the side surface each carrying out one hardness measurement to be described later, again hardness measurement it is possible to perform.
[0027]
　Incidentally, the hardness measurement test specimen can be a mounting table specimen is placed, the contact surface in contact with the test strip to create if any and the punch is a curved surface. For example, as shown in FIG. 4, by using a jig 100A consisting of the punch 130A to compress the test piece 10, push the test strip 10 mounted on the mounting table 200. Punch 130A, for example, similar to FIG. 2, the contact surfaces 131A are formed by the outer peripheral surface of the radius of curvature R, it has a plate width substantially the same width of the test piece 10, be formed as a member having a substantially semicircular plate shape good. Mounting table 200, not to deform even if pressed by the placed test piece 10 is punched 130A, as long as strong.
[0028]
　In this manner, when creating the hardness measurement test piece, since the test piece 10 in a state where the plate width direction is not restrained and compressed by the punch 130A, recess of the hardness measurement test piece was created plate width direction spread slightly. Further, since no use of a pressing member for pressing the test piece 10 from above, the test piece 10 is not fixed in the thickness direction, warpage occurs in the specimen 10 when it is pressed by the punch 130A. However, even if such deformation occurs in the hardness measurement test specimen, the numerical analysis for the hardness measurement test specimen if the known shape of the test piece 10 before the compression by punches 130A can be implemented. Therefore, in the creation of the hardness measurement test piece, not necessarily as shown in FIG. 2, there is no need to restrain the plate width direction and the thickness direction of the test piece 10. Of course, the placed test piece 10 on the mounting table 200, while restraining the either paddle in the plate width direction or thickness direction of the test piece 10, may be compressed by a punch 130A.
[0029]
　Figure 5, is mounted on the mounting table 200 mounting the test piece 10A, in a state that does not constrain the plate width direction, shows an example of the hardness measurement sample 20A which is pushed by forming a punch 130 to the test piece 10A. Hardness measurement sample 20A shown in FIG. 5 is created by using a jig 100 shown in FIG. To achieve a state of not constraining the plate width direction of the test piece 10A, the test pieces 10A in FIG. 5, the longitudinal central region punch 130 is pushed (i.e., recessed portions 21A of the hardness measurement test strip 20A may be formed a plate width of the area), is smaller than the plate width of the end region. Punch Thus, when placing the test pieces 10A in the die 110, a longitudinal central region punch 130 is pushed is now not in contact with the wall portion 111, 113, in a state of not constraining the strip width direction, the test piece 10A it is possible to push the 130. Incidentally, in the creation of the hardness measurement sample 20A shown in FIG. 5, the pressing member 121, 123 was also used.
[0030]
　Engaging test pieces 10A by a punch 130 the plate width direction without restraint, the hardness measurement sample 20A such as that shown in FIG. 5 bottom is created. Figure 5 bottom shows a perspective view and a side view of a hardness measurement test specimen 20A. Hardness measurement sample 20A has a recess 21A having a shape corresponding to the shape of the contact surface 131 of the punch 130, plastic strain is given to the longitudinal direction.
[0031]
　Incidentally, plastic strain is given to the hardness measurement test piece 20,20A can be set by the shape of the contact surface 131 of the punch 130 is pressed against the test piece 10, 10A. For example, the resolution is increased the larger the curvature radius R of the contact surface 131 of the punch 130, it is possible to obtain the relationship between the equivalent plastic strain more detail hardness. Incidentally, it is necessary to apply a large load to the more specimens 10,10A increasing the curvature radius R of the contact surface 131 of the punch 130.
[0032]
　Further, a punch 130,130A illustrated in FIGS. 2 and 4, the contact surfaces 131,131A is formed by the outer peripheral surface of the curvature radius R, and a shape having a plate width substantially the same width of the test piece 10,10A but the present invention is not limited to such an example. Punch 130,130A, for example contact surfaces 131,131A may be a spherical surface.
[0033]
　Thus by using the created hardness measurement test piece 20,20A, the hardness used to estimate the hardness of cold working parts - the process of obtaining the equivalent plastic strain curve is performed. In the following, the hardness using a hardness measuring test piece 20 shown in FIG. 3 - there will be described the case of obtaining the equivalent plastic strain curve, test other hardness measurement of hardness measurement for sample 20A such as that shown in FIG. 5 it may be performed similar process when using the piece.
[0034]
　[2-2. Hardness Measurement]
　Hardness - Upon obtaining the equivalent plastic strain curve, firstly, to measure the hardness of the hardness measurement test piece 20 formed at step S110 (S120). Hardness measurement test piece 20 has a plastic strain distribution in the longitudinal direction. For example, the recess 21 is pressed by the punch 130, high strain equivalent plastic exceeding uniform elongation in uniaxial tensile test is given. The portion not pressed by the punch 130 in hardness measurement for the test piece 20 is not plastic strain is applied, without distortion, which remains as the state of the base material. That is, the hardness measurement test piece 20, plastic strain distribution from strain region to be a uniform elongation greater than the uniaxial tensile test up to the region undistorted left of the base material has been granted. Here, the uniform elongation in uniaxial tensile test, pursuant to JIS Z 2241. Also, the strain equivalent plastic that exceeds the uniform elongation in uniaxial tensile test, for example, is the strain equivalent plastic more than 1.0.
[0035]
　In step S120, the embedding of such hardness measurement test specimen 20 to the resin, the recessed portion in an arbitrary direction of the plate thickness is changed as the measurement direction at 21, hardness measurement test specimen in a plurality of hardness measurement position of the measurement direction 20 to measure the hardness. For example, the longitudinal direction of the hardness measuring test piece 20 as a measurement direction, the hardness is measured at predetermined intervals in the longitudinal direction from the center position of the recessed portion 21 formed by pushing by the punch 130. Measurements of hardness can be measured by JIS Z 2244 Vickers hardness test.
[0036]
　6, the hardness measurement position P of the hardness measurement test specimen 20 n shown (n = 0,1, ···, k ) a. Hardness measurement position P n is along the longitudinal direction of the hardness measurement test piece 20, is set at equal intervals at a predetermined interval. Hardness measurement position P 0 is the center of the recessed portion 21 formed by pressing the punch 130, shows the most pressed position by the punch 130. Such a recess portion 21 of the hardness measuring test piece 20 center (hardness measurement position P 0 more longitudinally from) the hardness measuring position P n by measuring the hardness, the hardness distribution in the longitudinal direction is obtained .
[0037]
　[2-3. Hardness - equivalent plastic strain curve acquired]
　If the hardness of the hardness measuring test piece 20 in step S120 is determined, the equivalent plastic strain to get the distribution, based on the equivalent plastic strain distribution by numerical analysis based on the measured hardness hardness - get a equivalent plastic strain curve (S130).
[0038]
　Specifically, first, based on the hardness distribution in the longitudinal direction of the hardness measuring test piece 20 obtained in step S120, FEM (Finite Element Method; finite element method) Each hardness measurement site P by the numerical analysis, such as n calculating the equivalent plastic strain. Thus, equivalent plastic strain distribution of hardness measurement test specimen 20 is obtained. For example, as shown in FIG. 6, the hardness measurement position P 0 from the hardness measuring position P does not change from a thickness of the base material n After calculating the equivalent plastic strain distribution based on the hardness of the region A to, for example, in FIG equivalent plastic strain distribution is obtained as shown. By equivalent plastic strain and plots actual measurement values and hardness measurement position Hardness, Hardness - equivalent plastic strain curve is obtained.
[0039]
　Note that, in step 130, when a hardness measurement test specimen that was created while restraining the sheet width direction as hardness measurement test piece 20 shown in FIG. 3, for example using a two-dimensional FEM numeric it is possible to analyze. On the other hand, in the case of using a hardness measurement test specimen that was created in a state that does not restrain the sheet width direction as hardness measurement test piece 20A shown in FIG. 5, for example we have to numerical analysis by using the three-dimensional FEM is there. Therefore, preferable to use a hardness measurement test specimen that was created while restraining the plate width direction, than with hardness measurement test pieces were created with no restraining the plate width direction, shortening the analysis time can do.
[0040]
　By the processing of steps S110 ~ S130 above, hardness is used to estimate the hardness of cold working part - equivalent plastic strain curve is obtained.
[0041]
　[2-4. Hardness Estimation
　hardness in step S130 - the equivalent plastic strain curve is obtained, such hardness - it is possible to estimate the hardness of cold working components based on equivalent plastic strain curve (S140). Specifically, first, it calculates the equivalent plastic strain value of the cold working parts by numerical analysis of the FEM, or the like. Then, the equivalent plastic strain value of any portion of the cold worked parts, the hardness obtained in step S130 - using the equivalent plastic strain curve, identifies the hardness. Thus it is possible to estimate the hardness at the site.
[0042]
　<3. Summary>
　has been described above hardness estimation method of cold working component according to the present embodiment. According to this embodiment, the mounting table of the test piece is placed, the contact surface in contact with the test piece using a punch is a curved surface, the test piece was pressed, to create a hardness measurement test specimen. Thus, it is possible by compression tests once, the plastic strain distribution imparted to the test piece, to create a hardness measurement test specimen. Then, while measuring the hardness of the hardness measurement test piece, by calculating the numerical analysis equivalent plastic strain to compression of hardness measurement test piece, hardness is the relationship between the strain equivalent plastic and the hardness of the material - corresponding the plastic strain curve can be easily obtained. Obtained hardness - By using the equivalent plastic strain curve, from the equivalent plastic strain distribution of the resultant cold working parts by numerical analysis, the hardness of any region of the cold working parts can be easily estimated.
[0043]
　For example, in the cold working parts of complex shapes such as gears, conventionally, in order to estimate the hardness of any region of cold working parts, by changing the amount of compression of the test specimen strain measurement and plastic hardness there was a need to make the calculation more than once. In contrast, using the hardness estimation method of cold working component according to the present embodiment, the hardness by the compression test of one - it is possible to obtain the equivalent plastic strain curve, easily any of cold working parts We can estimate the hardness of the site. In the cold working parts of the leaf forging, by work hardening, the hardness is higher than the material before processing. In such as cold working parts, the use of the hardness estimation method of cold working component according to the present embodiment, obtaining the relationship between the equivalent plastic strain and hardness exceeding uniform elongation in a tensile test can. Therefore, for the cold working parts of the leaf forging it can easily estimate the hardness of any site.
[0044]
　Further, the thickness of the test piece used in hardness estimation method of cold working part according to the present embodiment is not particularly limited, and can be applied to the test piece of example 2mm following steel sheet, hardness by compression tests once - it is possible to obtain the equivalent plastic strain curve. The minimum value of the thickness of the specimen is determined according to the maximum load that can be imparted to the specimen by the punch to create the hardness measurement test specimen. Specimens, because in some cases is too thin becomes difficult to identify the distribution of plastic strain, some good hardness it is accurate having a thickness - can be obtained equivalent plastic strain curve. Further, according to the hardness estimation method of cold working component according to the present embodiment, without creating a high aspect ratio specimen, a thin steel sheet using a punch having an arcuate peripheral surface or the contact surface of the spherical high strain can be given to the test piece by crushing.
Example
[0045]
　Using the method according to the present invention, hardness of the hot-rolled steel sheet - has obtained the equivalent plastic strain curve. Hardness - In obtaining the equivalent plastic strain curve, firstly, the plate width 20 mm, Itacho 100 mm, a flat hot-rolled steel sheet having a thickness of 4mm as the base material (test piece), by using a jig shown in FIG. 2 , the outer circumferential surface a central portion of the test piece was compressed by punches arcuate. The radius of curvature of the arc portion of the punch is 20mm, its width was the same 20mm and a plate width of the test piece. In this embodiment, a load of 24tonf added to the test strip by a punch, the most compressed position (i.e., the center of the recessed portion) thickness of compressing the test piece so that 1 mm, a hardness measurement test specimen Created.
[0046]
　Then, after filling the hardness measurement test piece resin, the hardness was measured at 0.3mm intervals in the longitudinal direction from the center of the recess portion formed by being pressed by the punch. Hardness measurements were conducted based on JIS Z 2244 Vickers hardness test. In this Example was carried out three times in hardness measurement for one hardness measurement test specimen. In this case, after issuing the surface not affected by the previous hardness measurement by grinding the side face of the hardness measurement test specimen embodying the hardness measured every implementing one hardness measurement, perform the following hardness measurement It was.
[0047]
　On the other hand, performs numerical analysis by FEM for hardness measurement test specimen were obtained equivalent plastic strain distribution of hardness measurement test specimen. Note that FIG. 7 is a equivalent plastic strain distribution of the obtained hardness measurement test specimen by the numerical analysis.
[0048]
　Then, by using the equivalent plastic strain distribution of hardness measurement test piece shown in the measured value and 7 of the hardness of the hardness measurement test piece, it was identified equivalent plastic strain at each hardness measurement position. 3 times a hardness obtained by the hardness measurement (measurement N1 ~ N3) of the results obtained by plotting the equivalent plastic strain and identified from equivalent plastic strain distribution shown in FIG. As shown in FIG. 8, each plot is on substantially the same curve, it can be seen that there is a certain correspondence relationship between the hardness and the equivalent plastic strain. Incidentally, the hardness is obtained by the method of the present invention - the equivalent plastic strain curve, as shown by the broken line in FIG. 8, the least squares method, for example, from the relationship between the obtained hardness and equivalent plastic strain by measurement N1 ~ N3 it can be obtained using.
[0049]
　Here, in order to verify the validity of the relationship between the hardness obtained by the present invention equivalent plastic strain and the same hardness to impart plastic strain by rolling on specimens - with the result of obtaining the equivalent plastic strain curve , it was compared to the relationship between the hardness and the equivalent plastic strain. 9, the hardness obtained by rolling - shows the equivalent plastic strain trendline in solid lines. As shown in FIG. 9, the hardness obtained by the method of the present invention shown by broken lines - the equivalent plastic strain curve, the hardness obtained by rolling shown by the solid line - approximately equal to the equivalent plastic strain trendline. From this, precisely hardness by a method according to the invention - that the equivalent plastic strain curve can be acquired has been shown.
[0050]
　Further, as shown in FIG. 5, for the hardness measurement test pieces were created with no restraining the sheet width direction, the same test was carried out. That is, the plate width 20 mm, Itacho 100 mm, the base material of the flat hot-rolled steel sheet having a thickness of 4mm as (test piece), by using a jig shown in FIG. 2, the outer circumferential surface a central portion of the test piece compressed by the arc shape of the punch. Incidentally, the plate width of the longitudinal central region of the specimen, in order to avoid contact with the wall of the die, is smaller than the plate width (20 mm) of the edge area as shown in FIG. 5 above. The radius of curvature of the arc portion of the punch is 20mm, its width was the same 20mm and a plate width of the test piece. A load of 24tonf added to the test strip by the punch, the plate thickness of the central recess compresses the test piece so that 1 mm, have created a hardness measurement test specimen. Then, after embedding a hardness measurement test piece resin, the hardness was measured at 0.3mm intervals in the longitudinal direction from the center of the recess portion formed by being pressed by the punch.
[0051]
　As a result, for the hardness measurement test pieces were created with no restraining the plate width direction, similar to the hardness measurement test piece created by restraining the plate width direction strain equivalent plastic as shown in FIG distribution There had been granted. Then, the relationship between the hardness and the equivalent plastic strain was also obtained similar relationship to FIG. 8.
[0052]
　Having described in detail preferred embodiments of the present invention with reference to the accompanying drawings, the present invention is not limited to such an example. It would be appreciated by those skilled in the relevant field of technology of the present invention, within the scope of the technical idea described in the claims, it is intended to cover various changes and modifications , also such modifications are intended to fall within the technical scope of the present invention.
DESCRIPTION OF SYMBOLS
[0053]
　10,10A specimen
　20,20A hardness measurement test piece
　21,21A recess
　100,100A jig
　110 die
　111, 113 wall portion
　115 flat portions
　121 and 123 pressing member
　130,130A punch
　131,131A outer peripheral surface
　200 mounting table

The scope of the claims

[Requested item 1]A hardness estimation method of cold working parts,
　with the mounting table of the test piece is placed, and a punch contact surface is a curved surface in contact with the test piece, the test placed on the mounting table the piece was compressed by the punch to create a hardness measurement test piece having a recess having a shape corresponding to the shape of the contact surface of the punch,
　the direction in which the plate thickness is changed as the measurement direction in the recess, the hardness of the hardness measurement test specimen was measured at a plurality of hardness measurement positions of the measurement direction,
　by numerical analysis to calculate the strain equivalent plastic of the hardness measurement test piece, the equivalent to the hardness of each said hardness measuring position based on plastic strain and hardness - to get the equivalent plastic strain curve,
　the equivalent plastic strain value of the cold-processed part is calculated by numerical analysis, the hardness - based on equivalent plastic strain curve, it was calculated the Identifying the hardness from equivalent plastic strain value of any site between workpieces, the hardness estimation method of cold working parts.
[Requested item 2]
　The test piece is a flat plate, the hardness estimation method of cold working part according to claim 1.
[Requested item 3]
　The hardness measurement test piece, while constraining the specimen plate width direction, the specimen is prepared by compressed by the punch, hardness estimation method of cold working component of claim 2.
[Requested item 4]
　The hardness measurement test specimen has a strain distribution comprises a large strain region than uniform elongation obtained by uniaxial tensile test, hardness estimation cold working component according to any one of claims 1 to 3 Method.
[Requested item 5]
　The hardness measurement test piece, corresponding with the strain distribution comprises a strain region the plastic strain is greater than 1.0, the hardness estimation method of cold working component according to any one of claims 1 to 3.
[Requested item 6]
　The hardness measurement position, the set at a predetermined interval in the measurement direction from the center of the recess portion of the hardness measurement test piece, the hardness of cold working component according to any one of claims 1 to 5 estimation method.
[Requested item 7]
　The test piece, the a cold working parts of the same material, the hardness estimation method of cold working component according to any one of claims 1 to 6.
[Requested item 8]
　The hardness of steel - an equivalent plastic strain curve acquisition method,
　the mounting table of the test piece is placed, the contact surface in contact with the test piece using a punch which is curved, is placed on the mounting table the test pieces were compressed by the punch, said creating a hardness measurement test piece having a recess having a shape corresponding to the shape of the contact surface, of the punch
　measuring direction the direction in which the plate thickness is changed in said recess as the hardness of the hardness measurement test specimen was measured at a plurality of hardness measurement positions of the measurement direction,
　to calculate the strain equivalent plastic of the hardness measurement test specimen by numerical analysis, and the hardness of each said hardness measuring position the equivalent based on plastic strain and hardness - get equivalent plastic strain curve, steel hardness - equivalent plastic strain curve acquisition method.