JP7388201B2 - Stress evaluation method, bending workability evaluation method, and metal member manufacturing method - Google Patents

Description

The present disclosure relates to a stress evaluation method, a bending workability evaluation method, and a method for manufacturing a metal member.

When manufacturing metal parts by bending metal plates such as electrical connection terminals, the metal material may suffer damage due to shear deformation, such as cracks and wrinkles, after the specified bending process. Materials are selected to prevent this from occurring. As a basis for selecting appropriate materials, it is important to understand the relationship between bending stress and damage occurrence through testing. To this end, tests are conducted to determine how much damage occurs when stress is applied to metal materials.

The method for this type of test is defined, for example, in the standard "JBMA T307:1999" of the Japan Copper Brass Association, published in Non-Patent Document 1 below. In this standard, as shown in FIG. 6A, an upper mold 91 having two convex portions 92, 92 and a lower mold 95 having two concave portions 96, 96 capable of accommodating the convex portions 92, 92 are assembled. Using a jig 90 equipped with the following, bending is applied to the test material S configured as a metal plate. That is, as shown in FIG. 6B, the test material S is sandwiched between the upper mold 91 and the lower mold 95 and bent into a W shape. Then, the bent portion S5 of the test material S, which has become a mountain due to bending, is observed with an optical microscope, and the degree of the formed "cracks" and "wrinkles" is evaluated. Here, "wrinkle" is defined as "a state in which step-like depressions or streaks that appear due to bending can be observed," and "crack" is defined as "a state in which the bottom of the crack is a shear band that cannot be observed from directly above." It is defined as ``a state of being cracked along the line''. The test material S is classified into five levels: "no wrinkles", "small wrinkles", "large wrinkles", "small cracks", and "large cracks".

Additionally, a method for quantitatively evaluating the shear stress generated in metal plates has also been developed. For example, in the method by Miyauchi described in Non-Patent Document 2 below, tension is applied to a test material prepared by processing a metal material into a predetermined shape, and the relationship between shear stress and displacement is evaluated. In the method by Miyauchi, the shape of the test material is defined in which a plurality of slits are formed at predetermined positions from the viewpoint of eliminating the influence of rotation in the shear direction.

"Japan Copper Brass Association Technical Standards: Evaluation method for bending workability of copper and copper alloy thin plates and strips JBMA T307:1999" Japan Copper Brass Association Copper Alloy Standardization Committee for Electronic Components 1999 Kunio MIYAUCHI, “A Proposal of a Planar Simple Shear Test in Sheet Metals”, Scientific Papers of the Institute of Physical and Chemical Research, 1972, Vol. 78, No. 3, pp. 27-40

As a method for evaluating the shear stress that occurs when bending a metal plate material, as in the standard published in Non-Patent Document 1, the bent part is observed under a microscope to evaluate the degree of cracks and wrinkles. In this case, the evaluation index becomes qualitative. This makes it difficult to quantitatively compare the bending workability between different materials. There is a possibility that the evaluation results will change due to differences in examiners. In addition, in order to compare the level of bending workability between different materials, it is necessary to It is necessary to evaluate a large number of test materials S while changing the ratio R/t between the radius of curvature R of the curved surface shape at the top of the portion 97 and the plate thickness t of the test material S, which requires a large amount of labor for the test. It takes.

According to the method disclosed in Non-Patent Document 2, which records the relationship between stress and displacement while applying deformation to a test material, it is possible to quantitatively evaluate shear stress on a metal plate. can do. When stress is measured while applying tension to a test material as in the method of Non-Patent Document 2, the stress obtained by the measurement becomes a shear stress in the plane of the plate material. However, when bending the plate material, the plate material is deformed in an out-of-plane direction. Therefore, when performing bending, it is insufficient to evaluate shear stress in the in-plane direction as an indicator for avoiding damage caused by shearing of the material, such as cracks. It is desirable to quantitatively evaluate shear stress.

Therefore, we developed a stress evaluation method and a bending workability evaluation method that can quantitatively evaluate stress and bending workability when bending a metal plate material, and a method for quantitatively evaluating bending workability. An object of the present invention is to provide a method for manufacturing metal members that allows selection of raw materials.

In the stress evaluation method of the present disclosure, a test material configured as a metal plate is held at two holding points spaced apart from each other within the plane of the test material, and a test material is provided between the two holding points. A load is applied perpendicularly to one side of the test material at the pressed location, and the relationship between stress and displacement until the test material breaks is recorded.

In the bending workability evaluation method of the present disclosure, the stress when the test material breaks is acquired as the maximum shear stress τ _max by the stress evaluation method, the tensile strength of the test material is set as σ _max , and τ _max It is determined that the larger the maximum stress ratio calculated as /σ _max is, the less likely the test material is to crack when deformed in an out-of-plane direction. Alternatively, according to the stress evaluation method, the stress at the maximum point that appears at the lowest displacement in a curve in which the stress is recorded as a function of the displacement amount until the test material breaks is determined by the shear yield stress τ _s and the tensile strength of the test material as σ _max , it is determined that the larger the yield stress ratio calculated as τ _s /σ _max , the less likely the test material is to wrinkle when deformed in an out-of-plane direction. It is something.

The method for manufacturing a metal member of the present disclosure uses a metal material selected as a raw material after evaluation by the bending process evaluation method, and manufactures a metal member through a step including deforming the metal material in an out-of-plane direction. It is something to do.

The stress evaluation method and bending workability evaluation method according to the present disclosure can quantitatively evaluate stress and bending workability when bending a metal plate material. Furthermore, the method for manufacturing a metal member according to the present disclosure can quantitatively evaluate bending workability and select raw materials.

FIGS. 1A to 1C are diagrams showing a test apparatus used in the stress evaluation method and bending workability evaluation method according to an embodiment of the present disclosure. FIG. 1A is a plan view, and FIG. 1B is a sectional view taken along line AA in FIG. 1A. FIG. 1C is an enlarged view of FIG. 1B. Hatching indicating the cross section is omitted. FIGS. 2A and 2B are cross-sectional views illustrating stress evaluation using the above test device. FIG. 2A shows the state before load application, and FIG. 2B shows the state during load application. Hatching indicating the cross section is omitted. FIG. 3 is a diagram showing an example of a shear stress curve obtained in stress evaluation. 4A and 4B are diagrams showing shear stress curves measured for copper alloys in Examples. FIG. 4A shows the case where the test direction is RD for Corson Alloy 1, and FIG. 4B shows the case where the test direction is TD for the Cu-Mg alloy. 5A and 5B are diagrams showing stress evaluation results obtained for various copper alloys in Examples. FIG. 5A shows the maximum stress ratio τ _max /σ _max and FIG. 5B shows the yield stress ratio τ _max /σ _max . FIGS. 6A and 6B are diagrams illustrating a conventional bending workability evaluation method. FIG. 6A shows the state before bending, and FIG. 6B shows the state after bending.

[Description of embodiments of the present disclosure]
First, embodiments of the present disclosure will be listed and described.

In a stress evaluation method according to an embodiment of the present disclosure, a test material configured as a metal plate is held at two holding points spaced apart from each other within the plane of the test material, and the two holding points are A load is applied perpendicularly to one side of the test material at a pressing point provided between the two, and the relationship between stress and displacement until the test material breaks is recorded.

In the above stress evaluation method, a load is applied perpendicularly to the plate surface of a test material configured as a metal plate, and the relationship between stress and displacement until breakage is recorded. By applying a load in the out-of-plane direction to the plate material, shear deformation is applied to the plate material in the out-of-plane direction, and the stress generated in the plate material at that time is evaluated, so the stress generated in the plate material due to shear deformation is evaluated. can be quantitatively evaluated, including components in the out-of-plane direction. Since there is no need to process the plate material into a special shape or to perform measurements on a large number of test materials, quantitative evaluation of the shear stress on the plate material can be easily performed.

Here, it is preferable to record the stress when the test material breaks as the maximum shear stress τ _max . The maximum shear stress has a high correlation with the occurrence of cracks when an out-of-plane displacement such as bending is applied to the test material, and it is possible to quantitatively obtain the stress value related to the occurrence of cracks. can.

In a curve in which the stress is recorded as a function of the displacement amount until the test material breaks, the stress at the maximum point that appears at the lowest displacement amount may be recorded as the shear yield stress τ _s . Shear yield stress has a high correlation with the occurrence of wrinkles when an out-of-plane displacement such as bending is applied to the test material, and it is possible to quantitatively obtain the stress value related to the occurrence of wrinkles. can.

The stress evaluation method is carried out using a measuring device having a first jig, a second jig, and a third jig, and the first jig and the second jig are holds the test material by sandwiching it from the out-of-plane direction at two positions separated from each other within the plane of the test material, and the third jig is connected to the first jig and the third jig. At a position between the second jig, the test material is sandwiched and held from the out-of-plane direction. It is preferable to apply a load to the test material by moving it. Then, with a simple device configuration, it is possible to quantitatively evaluate the stress generated in a metal plate due to shear deformation in an out-of-plane direction. The shape of the test material is not particularly limited as long as it can be held between the jigs.

The test material is prepared as a rectangular plate, and the length direction is along one side of the rectangle, and the first jig, the second jig, and the third jig are each It is preferable to hold the test material in a sandwiched manner over the entire length thereof. Then, the stress is measured while holding the test material in a simple manner by sandwiching it from the out-of-plane direction, so the stress evaluation results are less likely to be influenced by the mechanism used to hold the test material. Become.

The distance between the third jig and each of the first jig and the second jig is preferably 0.5 mm or less along the in-plane direction of the test material. Since the spacing between the jigs is kept small, deformations other than shear deformation in the out-of-plane direction, such as elongation of the test material between the jigs, do not affect the stress evaluation results. It becomes difficult.

In the bending workability evaluation method according to the first embodiment of the present disclosure, the stress when the test material breaks is acquired as a maximum shear stress τ _max by the stress evaluation method, and the tensile strength of the test material is It is determined that the larger the maximum stress ratio calculated as τ _max /σ _max , where σ _max is, the harder the test material is to crack when deformed in an out-of-plane direction.

In the above bending workability evaluation method, the degree of bending workability of a material is evaluated based on the results of measuring the stress generated due to shear deformation when a metal plate is deformed in an out-of-plane direction. It is something. The inventors' research has shown that the shear stress measured by the stress evaluation method described above has a high correlation with the state of the material structure when bending and deforming the plate material, and that the shear stress measured by the stress evaluation method It has been revealed that the maximum stress ratio τ _max /σ _max shows a high correlation with the occurrence of cracks during bending. Therefore, by using the maximum stress ratio as an index and determining that the material with a larger value is less likely to crack when processed in an out-of-plane direction such as bending, it is possible to determine the occurrence of cracks during bending. The possibility of this can be quantitatively evaluated.

Here, it is preferable to determine that the test material has sufficient crack resistance when the maximum stress ratio τ _max /σ _max is equal to or greater than a predetermined maximum stress ratio threshold value. Then, materials that have high crack resistance and do not easily crack even when subjected to bending can be discriminated based on quantitative indicators and selected as raw materials to be subjected to bending or the like.

When the test material is copper or a copper alloy, the maximum stress ratio threshold may be set to 0.58. Then, it becomes possible to discriminate with high accuracy copper or copper alloy having high crack resistance.

In the bending workability evaluation method according to the second embodiment of the present disclosure, the stress evaluation method determines that the stress is the lowest in a curve recorded as a function of the displacement amount until the test material breaks. The stress at the maximum point that appears in the amount of displacement is the shear yield stress τ _s , and the tensile strength of the test material is σ _max . The larger the yield stress ratio calculated as τ _s /σ _max , the more the test material It is determined that wrinkles are unlikely to occur when deformed in an out-of-plane direction.

The inventors' research has shown that the shear stress measured by the stress evaluation method described above has a high correlation with the state of the material structure when bending and deforming the plate material, and that the shear stress measured by the stress evaluation method It has been revealed that the yield stress ratio τ _max /σ _max shows a high correlation with the occurrence of wrinkles during bending. Therefore, by using the yield stress ratio as an index and determining that the material with a larger value is less likely to cause wrinkles when processed in an out-of-plane direction such as bending, it is possible to reduce the occurrence of wrinkles during bending. The possibility of this can be quantitatively evaluated.

Here, it is preferable to determine that the test material has sufficient wrinkle resistance when the yield stress ratio τ _s /σ _max is equal to or greater than a predetermined yield stress ratio threshold value. Then, a material that has high wrinkle resistance and does not easily wrinkle even when subjected to bending can be discriminated based on quantitative indicators and selected as a raw material to be subjected to bending or the like.

When the test material is copper or a copper alloy, the yield stress ratio threshold may be set to 0.20 for the test material having a 30 mm square plate surface. Then, it becomes possible to discriminate copper or copper alloy having high wrinkle resistance with high accuracy.

A method for manufacturing a metal member according to an embodiment of the present disclosure uses a metal material selected as a raw material after evaluation by the bending workability evaluation method, and a step including deforming the metal material in an out-of-plane direction. , which manufactures metal parts.

When manufacturing a metal member through a process that involves deformation in an out-of-plane direction such as bending, when deforming in an out-of-plane direction, there is a possibility that damage caused by shearing such as cracks may occur in the deformed part. When this occurs, it becomes difficult to manufacture metal members having predetermined performance and strength. Therefore, by evaluating the bending workability of the raw metal material based on the stress evaluation results when deformed in an out-of-plane direction using the above bending workability evaluation method, it is possible to achieve high bending workability. Raw materials can be selected based on quantitative indicators. As a result, it becomes possible to manufacture a metal member having predetermined strength and performance with high reliability through bending and the like.

Here, it is preferable to select a metal material determined to have sufficient crack resistance in the bending property evaluation method as the raw material. Then, when performing out-of-plane deformation such as bending, it becomes possible to manufacture a metal member while suppressing the occurrence of cracks.

A metal material determined to have sufficient wrinkle resistance in the bending property evaluation method may be selected as the raw material. Then, when performing out-of-plane deformation such as bending, it becomes possible to manufacture a metal member while suppressing the generation of wrinkles.

The metal member may be an electrical connection terminal. Electrical connection terminals are manufactured by using a metal plate as a raw material and processing it into a predetermined shape through bending and the like. Bending at a steep angle is often added. If damage such as cracks or wrinkles occurs during processing, the mechanical strength and electrical properties of the electrical connection terminals may be affected. Therefore, by manufacturing electrical connection terminals using raw materials determined to have sufficient bendability by the above-mentioned bending workability evaluation method, electrical connection terminals having desired characteristics and strength can be produced. It becomes possible to manufacture with high productivity.

[Details of embodiments of the present disclosure]
Hereinafter, a stress evaluation method, a bending workability evaluation method, and a method for manufacturing a metal member according to an embodiment of the present disclosure will be described in detail using the drawings. The bending workability evaluation method according to the present disclosure can be performed using the evaluation results obtained by the stress evaluation method according to the present disclosure. Further, the method for manufacturing a metal member according to the present disclosure can be performed based on the evaluation result by the bending workability evaluation method according to the present disclosure. Hereinafter, in this specification, various measured values are measured at room temperature and in the atmosphere unless otherwise specified. In addition, concepts such as in-plane, out-of-plane, and perpendicular that express the shape and arrangement of members, as well as dimensional values, include not only geometrically strict concepts but also deviations within the allowable range for evaluation of metal plates. .

<Test equipment>
First, a test apparatus 1 used in the stress evaluation method and bending workability evaluation method according to the embodiment of the present disclosure will be described. 1A to 1C schematically show the configuration of the test apparatus 1. FIG. 1A is a plan view of the test apparatus 1, and FIG. 1B is a cross-sectional view taken along the line AA in FIG. 1A. FIG. 1C is an enlarged view of a portion of FIG. 1B.

The test device 1 includes a support frame 10 and a holder 20. The holder 20 includes a pair of fixed jigs 21 and 22 as a first jig and a second jig, and a movable jig 23 as a third jig. These jigs 21 to 23 each have block-shaped members 21a to 23a and 21b to 23b divided into upper and lower parts, and a plate-shaped test material S can be sandwiched between them. The upper blocks 21a to 23a of each of the jigs 21 to 23 are provided with through holes into which screws 24 can be inserted at positions on the outside of the test material S in the in-plane direction (x direction and y direction). Tap holes into which screws 24 can be fitted are provided at corresponding positions on the lower blocks 21b to 23b.

Three jigs are arranged in a line in the order of the first fixed jig 21, the movable jig 23, and the second fixed jig 22, and one plate-shaped test material S is placed between each of the jigs 21 to 22. The test material S can be held by the holder 20 by sandwiching it between the upper and lower blocks of the holder 23 and tightening the screw 24. Gaps 25, 25 are provided between the upper blocks 21a, 22a constituting the two fixing jigs 21, 22, respectively, and the upper block 23a constituting the movable jig 23, respectively. The distance between the gaps 25, 25 is 0.5 mm or less, for example 0.02 mm. Adjacent blocks 21b to 23b on the lower side of each of the jigs 21 to 23 are in contact with each other.

A holder H with a test material S sandwiched between a holder 20 having three jigs 21 to 23 can be accommodated and held in the support frame 10. In this specification, the direction in which the jigs 21 to 23 are lined up in the holding body H with the test material S sandwiched between the holders 20 is defined as the width direction (x direction). Further, within the plane of the test material S held by the holder 20, the direction orthogonal to the x direction is defined as the length direction (y direction). The thickness direction of the test material S, which is perpendicular to the x direction and the y direction, is defined as the vertical direction (z direction).

The support frame 10 has a housing space 11 that can accommodate the holding body H, and has a placement part 13 on which the holding body H can be placed in the housing space 11. Then, the holding body H accommodated in the accommodation space 11 can be placed on the placement portion 13 in the blocks 21b and 22b below the two fixing jigs 21 and 22. In the holder H, each part of the movable jig 23 is not directly supported by the components of the support frame 10, including the mounting part 13, but due to the continuity of the test material S, the parts of the movable jig 23 are It is held in the same plane as 21 and 22.

Four support columns 14 are erected on the edge 12 of the support frame 10 surrounding the accommodation space 11 . As shown in FIG. 2A, a pressing tool 30 is attached to the support column 14 so as to be movable in the ±z direction (not shown in FIGS. 1A and 1B). The pressing tool 30 has a columnar pressing member 31 at the center in the y direction. With the lower end surface of the pressing member 31 in contact with the upper surface of the movable jig 23, the pressing tool 30 moves downward (in the -z direction) to press the test material S through the movable jig 23. , a load F in an out-of-plane direction can be applied. It is preferable that the area and shape of the lower end surface of the pressing member 31 be set so as to include the entire area (pressing location S2) of the surface of the test material S sandwiched between the movable jig 23.

A load cell (not shown) is attached to the pressing tool 30, and the load F applied to the test material S by the pressing member 31 can be measured. Then, the relationship between the amount of displacement of the pressing member 31 in the z direction and the load F can be recorded. Pressing by the pressing member 31 can be performed using a known material testing machine that can perform tensile tests, compression tests, etc. on metal materials as a device that can measure and record the amount of displacement while applying the load F. can. The crosshead of the material testing machine is connected to the pressing tool 30, the material testing machine is operated in compression mode, and the relationship between the displacement amount of the crosshead and the applied load F is recorded while pressing down the pressing tool 30. .

<Stress evaluation method>
Next, a stress evaluation method according to an embodiment of the present disclosure will be described. In this stress evaluation method, a load is applied to the test material S configured as a metal plate in an out-of-plane direction to cause shear deformation. In the stress evaluation method according to the present embodiment, the test material S is held at two holding points S1, S1 separated from each other in the plane, and at a pressing point S2 provided between the holding points S1, S1, What kind of equipment can be used as long as it can record the relationship between stress and displacement until the test material S breaks while applying a load F perpendicularly to one side of the test material S? However, it can be suitably executed using the test apparatus 1 described above.

As the test material S, a metal material to be evaluated is prepared as a rectangular plate material. The dimensions of the plate material may be such that it has a surface shape that fits inside the area surrounded by the screws 24 of the holder 20 of the testing device 1. Further, the thickness of the test material S may be such that it can be held between the holders 20. A preferred example is a configuration in which the dimensions of the test material S are 30 mm in length x 30 mm in width x 0.15 mm in thickness.

As shown in FIG. 2A, in preparation before the test, each jig constituting the test apparatus 1 is arranged in the order of the first fixed jig 21, the movable jig 23, and the second fixed jig 22, and each jig is The test material S is placed between the upper blocks 21a to 23a and the lower blocks 21b to 23b that constitute the tools 21 to 23. In the test material S, the area sandwiched between the two fixing jigs 21 and 22 becomes the holding locations S1 and S1, and the area sandwiched between the movable jig 23 becomes the pressing location S2. Then, screws 24 are tightened into each of the jigs 21 to 23, and the test material S is held between the upper and lower blocks. Then, the test material S is sandwiched and held by the jigs 21 to 23 of the holder 20 along the entire length direction (y direction). In this way, the holding body H holding the test material S with the holder 20 is placed on the placing part 13 of the support frame 10 of the testing apparatus 1 with the lower surfaces of the two fixing jigs 21 and 22.

In this state, the pressing member 31 of the pressing tool 30 is brought into contact with the upper surface of the movable jig 23 from above. From this state, a downward load F is applied to the pressing tool 30 in the compression mode of the material testing machine to push down the movable jig 23. During the application of the load F, the relationship between the amount of downward displacement of the pressing tool 30 and the load F applied from the pressing tool 30 to the movable jig 23 is recorded.

By applying a downward load F to the movable jig 23, in the test material S sandwiched between the holders 20, the pressing point S2, which is halfway in the x direction, applies a downward load F perpendicular to the plate surface. will be applied. Then, as shown in FIG. 2B, holding points S1 and S1, which are areas held by fixing jigs 21 and 22 at both ends of the test material S in the x direction, are not displaced, whereas The pressing location S2, which is a region held by the movable jig 23, is displaced in an out-of-plane direction. As a result, shear deformation in the out-of-plane direction occurs between the holding locations S1, S1 and the pressing location S2. When the amount of displacement of the pressing point S2 due to the load F is increased and the shear deformation is further increased, a rupture finally occurs between the holding points S1, S1 and the pressing point S2.

When using the test device 1, there are two locations where shear deformation is applied between the holding locations S1 and S1 and the pressing location S2, so the pressing load F measured by a load cell etc. is divided by 2, and By normalizing the cross-sectional area of each location, that is, the area obtained by multiplying the length (dimension in the y direction) of the plate material by the thickness (dimension in the z direction), the shear stress occurring at the shear deformation location of the test material S can be calculated. can be calculated. The stress is recorded with respect to the amount of displacement (stroke) in the z direction until the test material S breaks. FIG. 3 illustrates a shear stress curve recording shear stress as a function of displacement.

As shown in FIG. 3, the shear stress curve shows a tendency for the shear stress to increase as the amount of displacement increases. In the shear stress curve, the shear stress observed at the time when the test material S breaks (in FIG. 3, the point at which the amount of displacement is approximately 0.6 mm) is defined as the maximum shear stress τ _max . In FIG. 3, the maximum shear stress τ _max is approximately 380 MPa.

Further, in the shear stress curve, there is a yield point, that is, a maximum point where the shear stress changes from increasing to decreasing or stagnation as the amount of displacement increases. The stress at this maximum point is defined as shear yield stress τ _s . There may be multiple maximum points in the shear stress curve, but in such cases, the maximum point that appears at the lowest displacement is regarded as the yield point, and the stress at the yield point is defined as the shear yield stress τ It is considered as _s . In the shear stress curve shown in FIG. 3, three maximum points (shoulder structure) can be seen as indicated by arrows. Among these, the maximum point located at the lowest displacement amount (approximately 0.18 mm) indicated by the filled arrow becomes the yield point, and the shear yield stress τ _s is approximately 120 MPa.

In the stress evaluation according to this embodiment, a load F is applied to the plate-shaped test material S in an out-of-plane direction, and stress is measured while deforming the test material S in the out-of-plane direction. Therefore, unlike the conventional shear stress evaluation method as described in Non-Patent Document 2, the shear stress when shearing deformation out of the plane is evaluated instead of the stress when shearing deformation in the plane. It also includes components and can be measured. In this way, by measuring the shear stress associated with out-of-plane deformation, the measurement results can be used to calculate the stress generated in the plate material when processing that involves out-of-plane deformation, such as bending, is performed on the plate material. It can be used as an indicator.

In particular, the maximum shear stress τ _max and the shear yield stress τ _s as representative values of the stress obtained in the shear stress curve can be suitably used as indicators indicating the resistance of the material to shear deformation. The maximum shear stress τ _max corresponds to the stress at which the test material S breaks, and has a high correlation with the occurrence of cracks in the test material S, as shown in later examples. Therefore, it can be said that the larger the maximum shear stress τ _max is, the less likely cracks due to shear deformation will occur in the material. On the other hand, the shear yield stress τ _s corresponds to the stress at which shear bands begin to occur in the test material S, and is related to the occurrence of wrinkles in the test material S, as shown in the later examples. . Therefore, it can be said that the larger the shear yield stress τ _s is, the less likely wrinkles will occur in the material due to shear deformation.

In this evaluation method, a load F is applied perpendicular to the plate surface to the plate-shaped test material S to deform the test material S in an out-of-plane direction, so as in the case of Non-Patent Document 2, There is no need to process the test material into a special shape, and it is sufficient to prepare a test material S with a simple shape such as a rectangle. In addition, like the test device 1 described above, the test material S is held at two holding points S1, S1 that are separated from each other in the plane, and a pressing point S2 is placed between the two holding points S1, S1. By using a device with a simple configuration that applies a load F and appropriately combining it with a general-purpose material testing machine, etc., stress can be easily evaluated.

The specific configuration of the device that performs the evaluation is not particularly limited, but may be a form in which the test material S is sandwiched and held over the entire length direction (y direction), as in the test device 1 described above. By using the holder 20 of can be suppressed. However, depending on the type of the test material S, the shear yield stress τ _s may show dependence on the width (dimension in the x direction) of the test material S, and in that case, the shear yield stress τ s between the materials When comparing stresses, values measured for test materials S having the same width may be used. It has been confirmed that the maximum shear stress τ _max does not substantially depend on the width of the test material S. In addition, it was confirmed that the length (dimension in the x direction) and thickness (dimension in the z direction) of the test material S have almost no effect on the obtained shear stress curve if it is normalized by the cross-sectional area. has been done. Hereinafter, unless otherwise specified, specific numerical values of stress indicate values measured for a test material S having a length of 30 mm x width of 30 mm x thickness of 0.15 mm.

Depending on the type of test material S, there may be anisotropy in shear stress depending on the direction within the plate surface. In that case, the test may be performed with the direction in which the shear stress is to be evaluated aligned with the length direction (y direction) of the sample. For example, when the test material S is copper or a copper alloy, the shear stress exhibits anisotropy within the plate plane in relation to the rolling direction, but the shear stress exhibits anisotropy in the rolling direction (RD) and in the rolling direction. The test material S and the holder H may be prepared so that the test direction in which the stress associated with bending or other processing is to be evaluated faces the y direction among the orthogonal directions (Traverse Directions; TD).

In the test apparatus 1, in order to avoid the influence of friction between the fixed jigs 21, 22 and the movable jig 23, the upper blocks 21a, 22a of the fixed jigs 21, 22 and the movable jig 23 are A gap 25, 25 is provided between the upper blocks 23a. However, when obtaining a shear stress curve, two fixed jigs 21 and 22 and a movable jig 23 are used to prevent the influence of phenomena other than shear deformation, such as elongation of the metal material, from affecting the measurement results. It is preferable that the gap 25, 25 between them is smaller. From this point of view, the width of the gaps 25, 25 along the x direction is set to within 0.5 mm. More preferably, the width of the gaps 25, 25 is smaller than the thickness of the test material S.

<Bending workability evaluation method>
Next, a bending workability evaluation method according to an embodiment of the present disclosure will be described. The bending workability evaluation method according to the present embodiment evaluates the bending workability of a metal material using the evaluation results obtained by the stress evaluation method according to the embodiment of the present disclosure described above. Here, bendability refers to the extent to which damage such as cracks and wrinkles occurs at the bending point when bending a metal material.The less such damage occurs, the better It is considered to have high bendability.

We observed cracks in metal materials such as copper alloys using a scanning electron microscope (SEM) and analyzed their crystal orientation using electron backscatter diffraction (EBSD). It has become clear that wrinkles occur along the shear bands and that wrinkles also occur along with the formation of the shear bands. Furthermore, it was confirmed that shear deformation occurred during bending deformation, and as the shear deformation progressed, crystal grain groups corresponding to shear bands were generated within the crystal structure. Therefore, by using the stress evaluation method described above, it is possible to correlate the results of measuring the stress associated with shear deformation with the likelihood of cracking or wrinkles occurring during bending.

Specifically, the maximum shear stress τ _max obtained in the stress evaluation test can be correlated to the degree of occurrence of cracks during bending. It can be considered that the larger the maximum shear stress τ _max is, the less likely cracks will occur during bending. The values of maximum shear stress τ _max may be directly compared between different materials, but the maximum shear stress τ _max is divided by the tensile strength σ _max of the material to obtain the maximum stress ratio τ _max /σ _max By doing so, the bendability of the material can be evaluated more accurately. It can be evaluated that the larger the value of the maximum stress ratio τ _max /σ _max is, the less likely cracks will occur due to deformation in the out-of-plane direction during bending, that is, the higher the crack resistance will be.

Furthermore, the shear yield stress τ _s obtained in the stress evaluation test can be correlated to the degree of wrinkle generation during bending. It can be considered that the larger the shear yield stress τ _s is, the less likely wrinkles will occur during bending. The values of shear yield stress τ _s may be directly compared between different materials, but the shear yield stress τ _s is divided by the tensile strength σ _max of the material to obtain the yield stress ratio τ _s /σ _max By doing so, the bendability of the material can be evaluated more accurately. It can be evaluated that the larger the value of the yield stress ratio τ _s /σ _max is, the less likely wrinkles will occur due to deformation in an out-of-plane direction during bending, that is, the higher the wrinkle resistance.

Here, the tensile strength σ _max of a material is the tensile stress applied to a sample when the material is pulled and broken, and can be evaluated, for example, by a tensile test based on JIS Z 2241. Deformation associated with bending of metal materials may progress with both plane strain and shear strain, but plane strain is thought to be related to tensile strength, and shear strain is related to shear stress. . As mentioned above, shear strain causes cracks and wrinkles during bending, but plane strain is less likely to cause cracks and wrinkles. Therefore, if the tensile strength σ _max of the material is small and it is easy to bend with plane strain, it can be said that even a material with a certain degree of small shear stress is unlikely to generate cracks or wrinkles due to shear strain during bending. . Therefore, rather than associating the maximum shear stress τ _max or shear yield stress τ _s values themselves with bending workability, the maximum stress ratio τ _max /σ _max or the yield stress ratio τ, which is the value divided by the tensile strength σ _max , By using _s /σ _max as an index, it is possible to more accurately evaluate whether cracks and wrinkles are likely to occur during bending. In many copper alloys, the maximum shear stress τ _max is smaller than the tensile strength σ _max and the maximum stress ratio τ _max /σ _max is 1 or less. The yield stress ratio τ _s /σ _max is smaller than the maximum stress ratio τ _max /σ _max .

By comparing the maximum stress ratio τ _max /σ _max and the yield stress ratio τ _s /σ _max between different materials, it is possible to compare the crack resistance and wrinkle resistance between the materials. In addition, the maximum stress ratio τ _max /σ _max and the yield stress ratio τ _s /σ _max are set as the threshold values above which cracks or wrinkles will not occur in the material, respectively. All you have to do is estimate the ratio threshold. The threshold value can be estimated by, for example, comparing the result of estimating the degree of occurrence of cracks and wrinkles due to bending through microscopic observation as a preliminary test with the result of stress measurement by the stress evaluation method according to the above embodiment. So, it can be done. Then, in the material to be evaluated, if the maximum stress ratio τ _max /σ _max is equal to or greater than a predetermined maximum stress ratio threshold value, the material may be evaluated as having sufficient crack resistance. Further, if the yield stress ratio τ _s /σ _max is equal to or greater than a predetermined yield stress ratio threshold value, it may be evaluated that the material has sufficient wrinkle resistance.

The specific maximum stress ratio threshold and yield stress ratio threshold can be set depending on the main components of the alloy, the type of material, the application, and the like. For example, in the case of copper and copper alloys used as materials for electrical connection terminals, etc., if the maximum stress ratio threshold is set to 0.58, as shown in the example below, it is possible to make materials that are less prone to cracking during bending. can be sorted. More preferably, the maximum stress threshold is 0.60 or more. Furthermore, by setting the yield stress ratio threshold to 0.20, it is possible to select materials that are less likely to wrinkle during bending. It is more preferable that the yield stress ratio threshold is 0.21 or more.

In Mises stress, normal stress σ and shear stress τ have a relationship of σ=√3τ. In other words, τ=(1/√3)σ. This coefficient of (1/√3)≈0.577 coincides with the value of the maximum stress ratio threshold given above based on the example for copper or copper alloy. The ratio of the normal stress σ and the shear stress τ can be mapped to the ratio of the tensile strength σ _max and the maximum shear stress τ _max , and from the coincidence of this coefficient, the maximum stress ratio threshold of 0.58 mentioned above is It is thought that it can be used as an indicator of the presence or absence of cracking in various metal materials, not limited to copper alloys.

When evaluating the bending workability of metal materials, as described in Non-Patent Document 1, the bending process is performed by observing the bending process using a microscope to determine the presence or absence of cracks and wrinkles. It is difficult to quantitatively evaluate properties and use them for comparisons between materials. However, in the bending workability evaluation method according to the present embodiment, a stress evaluation test is performed, and the maximum shear stress τ _max and shear yield stress τ _s are measured as numerical values, and then the bending process is performed by comparing them with threshold values, etc. can be quantitatively evaluated. Therefore, it is possible to estimate bending workability as an objective value by eliminating the effects associated with qualitative evaluation, such as variations between different evaluators, and it is also possible to easily perform quantitative comparisons between different materials. I can do it.

<Method for manufacturing metal parts>
Finally, a method for manufacturing a metal member according to an embodiment of the present disclosure will be described. Here, a metal member having a predetermined shape is manufactured using a plate-shaped metal material as a raw material through a process including deformation of the metal material in an out-of-plane direction, such as bending. At this time, when selecting a metal material to be used as a raw material, the bending workability evaluation method according to the embodiment of the present disclosure described above is applied.

That is, a test is performed using the stress evaluation method described above on a metal material that is a raw material for processing, and the test results are used to perform an evaluation using the bending workability evaluation method described above. For example, if a candidate metal material has a maximum stress ratio τ _max /σ _max that is greater than or equal to a predetermined maximum stress ratio threshold value, it can be evaluated as having sufficient crack resistance. , the metal material can be used as a raw material for processing. Furthermore, if the candidate metal material has a yield stress ratio τ _s /σ _max that is greater than or equal to a predetermined yield stress ratio threshold value, it can be evaluated that it has sufficient wrinkle resistance. Bye. Alternatively, if multiple candidates are compared and a metal material exhibiting a large maximum stress ratio τ _max /σ _max and a large yield stress ratio τ _s /σ _max is selected as the raw material for processing. good.

The type of metal member manufactured is not particularly limited, but electrical connection terminals can be cited as a suitable example. Electrical connection terminals are manufactured by punching a metal plate, typically copper or copper alloy, into a predetermined shape and then bending the plate. It often involves bending to a steep angle, such as 180°. If damage such as cracks or wrinkles occurs to the plate material during punching or bending, the manufactured electrical connection terminal may not have the specified electrical characteristics or mechanical strength. There is sex. After quantitatively evaluating the bending workability of the material through the above bending workability evaluation, if a material with sufficiently high cracking resistance and wrinkle resistance is selected as a raw material, it is possible to achieve the specified electrical properties and mechanical properties. Electrical connection terminals with high physical strength can be manufactured with high productivity.

Examples are shown below. Note that the present invention is not limited to these Examples. Here, the shear stress of various copper alloy materials was measured and compared with the results of bending tests. Each evaluation below was performed at room temperature (25° C.) in the atmosphere.

[Test method]
(Sample preparation)
The following various copper alloy plates were prepared as samples.
- Corson alloys 1 and 2: The contents of component elements are different from each other.
・Cu-Mg alloy ・Cu-Zn alloy 1 to 3: Contents of component elements are different from each other.

(Obtaining shear stress curve)
A shear stress curve was obtained for each sample by the stress evaluation method according to the embodiment described above using a test apparatus having the structure shown in FIGS. 1A to 1C. At this time, a material testing machine ("Autograph AG-10" manufactured by Shimadzu Corporation) was used to apply the load to the pressing tool and measure the amount of displacement and applied load. The displacement speed was 2 mm/min. In the measurement, each sample was oriented in the longitudinal direction (y direction) with two directions, the rolling direction (RD) and the vertical direction (TD), as test directions. Measurements in each test direction were performed three times. The shape of the test material at the time of measurement was 30 mm in length x 30 mm in width x 0.15 mm in thickness. In the holder, the width of the gap between the fixed jig and the movable jig was 0.02 mm.

(Tensile strength)
A tensile test based on JIS Z 2241 was conducted on each sample, and the tensile strength σ _max was measured. The measurement was performed by processing a plate-shaped sample with a thickness of 0.15 mm into a JIS 13B dumbbell shape, and applying a tensile load in each of the RD and TD directions. For the test, a material testing machine ("Autograph AG-10" manufactured by Shimadzu Corporation) was used, the test speed was 2 mm/min, and the distance between the gauge lines was 25 mm.

(Bending evaluation test)
Each sample was subjected to bending and its bending workability was evaluated. Specifically, a sample having a thickness of 0.15 mm and a width of 1.5 mm was bent in two directions, RD and TD. At this time, 180° bending was performed so that the radius of curvature (inner R) on the inside of the bending was 0.3 mm. Thereafter, the portion on the outside of the bend was observed using an optical microscope to check for cracks and wrinkles. At this time, similar to the standard described in Non-Patent Document 1, "cracking" is determined as "a state in which the bottom of the crack cannot be observed from directly above, and it is cracked along a shear band", and "wrinkle" is defined as: It was judged as "a state in which step-like depressions or streaks that appeared due to bending could be observed".

[Test results]
FIG. 4A shows the shear stress curves obtained for the measurement with the test direction RD for Corson Alloy 1, and FIG. 4B shows the shear stress curves obtained for the measurement with the test direction TD for the Cu-Mg alloy. The horizontal axis shows the amount of displacement, and the vertical axis shows the shear stress, and the shear stress generally increases as the amount of displacement increases. Measurements are continued until the sample breaks. Each figure shows the results of three independent measurements.

In FIGS. 4A and 4B, three measurements each show similar results, with similar values of maximum shear stress τ _max (stress at break) and similar amounts of displacement. , a shoulder structure is formed. This confirms that the measurement of shear stress by this stress evaluation method has high reproducibility.

In the shear stress curves of FIGS. 4A and 4B, when the shear stress at fracture, that is, the maximum value of the shear stress, is read as the maximum shear stress τ _max , in both the Corson alloy in FIG. 4A and the Cu-Mg alloy in FIG. 4B, Also, the maximum shear stress τ _max is approximately 380 MPa. Furthermore, in both FIGS. 4A and 4B, three shoulder structures are seen in the shear stress curves, as indicated by arrows in the figures. Among these, when the shear stress corresponding to the shoulder structure that appeared at the lowest displacement amount is read as the shear yield stress, the shear yield stress is approximately 120 MPa for all samples. The average value of three measurements was recorded for both the maximum shear stress τ _max and the shear yield stress τ _s .

The maximum shear stress τ _max and shear yield stress τ _s were read from the shear stress curve obtained for each sample in the same manner as described above with respect to FIGS. 4A and 4B. Then, each was divided by the tensile strength σ _max to calculate the maximum stress ratio τ _max /σ _max and the yield stress ratio τ _s /σ _max . FIGS. 5A and 5B show the values of the maximum stress ratio τ _max /σ _max and the yield stress ratio τ _s /σ _max of each sample, respectively. In the figure, for each alloy type, both the value where the test direction is RD and the value where the test direction is TD are displayed as a bar graph. In addition, the results of the bending evaluation test are displayed at the bottom of the graph along with the name of the alloy type. In the bending evaluation test, if a crack is observed, it is indicated as "crack", and if wrinkles are observed, it is indicated as "wrinkle". If neither cracks nor wrinkles were observed, it was indicated as "good".

Looking at the results summarizing the maximum stress ratio τ _max /σ _max in FIG. 5A, we can see that there are cases where the test results are “good” compared to cases where “cracking” occurs in the bending evaluation test. It can be seen that the maximum stress ratio τ _max /σ _max tends to be larger in cases where only “wrinkles” are generated. This suggests that the maximum shear stress τ _max has a correlation with the occurrence of cracking during bending deformation, and the larger the value, the higher the cracking resistance. Then, the crack resistance can be quantitatively evaluated by dividing the maximum shear stress τ _max by the tensile strength σ _max to obtain the maximum stress ratio τ _max /σ _max . As shown by the broken line in the figure, if the maximum stress ratio τ _max /σ _max is 0.58 or more, "cracking" does not occur during bending deformation, while the maximum stress ratio τ _max /σ _max is 0. If it is smaller than .58, it can be seen that "cracking" has occurred. In this way, by setting a threshold value for the maximum stress ratio τ _max /σ _max and selecting materials whose maximum stress ratio τ _max /σ _max is larger than the threshold value, it is possible to avoid cracking during bending. can. The same threshold value can be applied regardless of the test direction (RD or TD).

Furthermore, looking at the results summarizing the yield stress ratio τ _s /σ _max in Figure 5B, we can see that the test results are "good" compared to when "cracks" or "wrinkles" occur in the bending evaluation test. There is a tendency for the yield stress ratio τ _s /σ _max to be larger when This suggests that the shear yield stress τ _s has a correlation with the occurrence of wrinkles during bending deformation, and the larger the value, the higher the wrinkle resistance. Note that the occurrence of "cracking" in the bending evaluation test means that wrinkles occur when bending is performed under conditions that are gentler than the above. The wrinkle resistance can be quantitatively evaluated by dividing the shear yield stress τ _s by the tensile strength σ _max to obtain the yield stress ratio τ _s /σ _max . As shown by the broken line in the figure, if the yield stress ratio τ _s /σ _max is 0.20 or more, “wrinkles” do not occur during bending deformation, while the yield stress ratio τ _s /σ _max is 0. If it is smaller than .20, it can be seen that "wrinkles" or even "cracks" have occurred. In this way, by setting a threshold value for the yield stress ratio τ _s /σ _max and selecting materials whose yield stress ratio τ _s /σ _max is larger than the threshold value, it is possible to avoid wrinkles during bending. can. The same threshold value can be applied regardless of the test direction (RD or TD).

In FIG. 5A, there is a clear difference in the value of the maximum stress ratio τ _max /σ _max between the case where the bending workability evaluation result is “good” and the case where “wrinkles” are generated. No relationship is seen. Therefore, the maximum stress ratio τ _max /σ _max cannot be applied as a parameter used as an index of the occurrence of “wrinkles”, and it is necessary to use the yield stress ratio τ _s /σ _max . Furthermore, in FIG. 5B, there is no clear relationship in magnitude between the values of the yield stress ratio τ _s /σ _max between the case where "cracking" occurs and the case where only "wrinkles" occur. I can't do it. Therefore, the yield stress ratio τ _s /σ _max cannot be applied as a parameter used as an index of the occurrence of “cracking”, but the maximum stress ratio τ _max /σ _max must be used. Depending on the type of metal member to be manufactured and the type of processing to be performed, if "cracking" is not acceptable, but "wrinkling" is acceptable, only the maximum stress ratio τ _max /σ _max is applied to the material. Using this as an index for selection, a material whose maximum stress ratio τ _max /σ _max is equal to or greater than a predetermined threshold value may be selected. On the other hand, if the occurrence of "wrinkles" is not allowed, the yield stress ratio τ s /σ _max is also used as an index in addition to the maximum stress ratio τ _max /σ _max , _and the maximum stress ratio τ _max /σ _max is What is necessary is to select a material in which the maximum stress ratio is equal to or greater than a predetermined yield stress ratio threshold, and the yield stress ratio τ _s /σ _max is equal to or greater than a predetermined yield stress ratio threshold.

Although the embodiments of the present disclosure have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.

1 Test device 10 Support frame 11 Accommodation space 12 Edge 13 Placement section 14 Support column 20 Holder 21 First fixing jig 21a Upper block 21b of first fixing jig Lower block 22 of first fixing jig Second fixing jig 22a Second fixing jig upper block 22b Second fixing jig lower block 23 Movable jig 23a Movable jig upper block 23b Movable jig lower block 24 Screw 25 Gap 30 Pressing tool 31 Pressing member 90 Conventional jig for bending workability test 91 Upper mold 92 Convex portion 95 Lower mold 96 Recessed portion 97 Joint portion F Load H Holding body S Test material S1 Holding location S2 Pressing location S5 Bending portion t Plate thickness x Width direction y Length direction z Vertical direction

Claims (17)

A test material configured as a metal plate is held at two holding points spaced apart from each other within the plane of the test material,
Applying a load perpendicularly to one side of the test material at a pressing point provided between the two holding points,
When recording the relationship between stress and displacement until the test material breaks,
Using a measuring device having a first jig, a second jig, and a third jig,
The first jig and the second jig sandwich and hold the test material from out-of-plane directions at two positions separated from each other within the plane of the test material,
The third jig holds the test material between the first jig and the second jig from an out-of-plane direction. A stress evaluation method that applies a load to the test material by moving a second jig in an out-of-plane direction of the test material . The stress evaluation method according to claim 1, wherein the stress when the test material breaks is recorded as a maximum shear stress τ _max . 1 . The stress at the maximum point that appears at the lowest displacement in a curve in which the stress is recorded as a function of the displacement amount until the test material breaks is recorded as a shear yield stress τ _s . Or the stress evaluation method according to claim 2. The test material is prepared as a rectangular plate, and the length direction is along one side of the rectangle,
Any one of claims 1 to 3, wherein the first jig, the second jig, and the third jig each sandwich and hold the test material over the entire length direction. The stress evaluation method described in Section 1 . A distance between the third jig and each of the first jig and the second jig is 0.5 mm or less along the in-plane direction of the test material. The stress evaluation method according to any one of claims 1 to 4 . A test material configured as a metal plate is held at two holding points spaced apart from each other within the plane of the test material,
Applying a load perpendicularly to one side of the test material at a pressing point provided between the two holding points,
By a stress evaluation method that records the relationship between stress and displacement until the test material breaks ,
Obtain the stress when the test material breaks as the maximum shear stress τ _max ,
Bending processing in which it is determined that the larger the maximum stress ratio calculated as τ _max /σ _max , where the tensile strength of the test material is σ _max , the more likely the test material is to crack when deformed in an out-of-plane direction. Gender evaluation method. By the stress evaluation method according to any one of claims 1 to 5 , the stress when the test material breaks is obtained as the maximum shear stress τ _max ,
Bending processing in which it is determined that the larger the maximum stress ratio calculated as τ _max /σ _max , where the tensile strength of the test material is σ _max , the more likely the test material is to crack when deformed in an out-of-plane direction. Gender evaluation method. Claim 6 or Claim 7, wherein the test material is determined to have sufficient crack resistance when the maximum stress ratio τ _max /σ _max is equal to or greater than a predetermined maximum stress ratio threshold. The bending workability evaluation method described. The bending workability evaluation method according to claim 8, wherein when the test material is copper or a copper alloy, the maximum stress ratio threshold is set to 0.58. A test material configured as a metal plate is held at two holding points spaced apart from each other within the plane of the test material,
Applying a load perpendicularly to one side of the test material at a pressing point provided between the two holding points,
By a stress evaluation method that records the relationship between stress and displacement until the test material breaks ,
In the curve in which the stress is recorded as a function of the displacement amount until the test material breaks, the stress at the maximum point that appears at the lowest displacement amount is defined as the shear yield stress τ _s ,
A bending process in which it is determined that the larger the yield stress ratio calculated as τ _s /σ _max , where the tensile strength of the test material is σ _max , the harder the test material is to wrinkle when deformed in an out-of-plane direction. Gender evaluation method. According to the stress evaluation method according to any one of claims 1 to 5 , in a curve in which the stress is recorded as a function of the displacement amount until the test material breaks, the stress is determined to be the lowest displacement amount. Let the stress at the maximum point that appears be the shear yield stress τ _s ,
A bending process in which it is determined that the larger the yield stress ratio calculated as τ _s /σ _max , where the tensile strength of the test material is σ _max , the harder the test material is to wrinkle when deformed in an out-of-plane direction. Gender evaluation method. Claim 10 or Claim 11 , wherein the test material is determined to have sufficient wrinkle resistance when the yield stress ratio τ _s /σ _max is greater than or equal to a predetermined yield stress ratio threshold. The bending workability evaluation method described. The bending workability evaluation method according to claim 12 , wherein when the test material is copper or a copper alloy, the yield stress ratio threshold is set to 0.20 for the test material having a 30 mm square plate surface. . Using a metal material selected as a raw material after evaluation by the bending workability evaluation method according to any one of claims 6 to 13 ,
A method for manufacturing a metal member, comprising manufacturing the metal member through a step including deforming the metal material in an out-of-plane direction. Manufacturing the metal member according to claim 14 , wherein a metal material determined to have sufficient crack resistance in the bending workability evaluation method according to claim 8 or 9 is selected as the raw material. Method. According to claim 14 or 15 , a metal material determined to have sufficient wrinkle resistance in the bending property evaluation method according to claim 12 or 13 is selected as the raw material. A method for manufacturing metal parts. The method for manufacturing a metal member according to any one of claims 14 to 16 , wherein the metal member is an electrical connection terminal.

Images