JP7709026B2 - Manufacturing method of processed materials - Google Patents

Description

This application discloses a method for manufacturing processed materials.

Patent document 1 discloses a technology for shearing a steel plate using a punch and a die to obtain a processed material. In this technology, the fracture surface of the punched material is pressed against the fracture surface of the processed material, thereby reducing the tensile residual stress in the fracture surface of the processed material.

International Publication No. WO 2016/136909

As disclosed in Patent Document 1, the tensile residual stress at the fracture surface of processed materials obtained by shearing steel plates may be large. When obtaining processed materials by shearing steel plates, a new technology is needed that can reduce the tensile residual stress at the fracture surface of the processed materials.

In addition, when the processed material has multiple sheared end faces, it is also important to suppress the variation in the properties of the multiple sheared end faces. For example, as shown in FIG. 1, when a steel plate 5 is sheared to form a first sheared end face 1 and a second sheared end face 2, it is desirable to suppress the variation in the properties of the first sheared end face 1 and the second sheared end face 2 and reduce the tensile residual stress on the fracture surface at both sheared end faces 1 and 2.

As one of the means for solving the above problems, the present application provides:
A method for producing a processed material by shearing a steel plate, comprising the steps of:
disposing the steel plate between a first blade and a second blade, wherein the steel plate has a first surface and a second surface opposite to the first surface, the first surface being disposed on the first blade side and the second surface being disposed on the second blade side; and
shearing the steel plate by moving the first blade and the second blade relatively;
Including,
At a time when a crack is generated in the steel plate by the first blade and the second blade, a plate thickness T (mm) of the steel plate and an inclination angle α of the steel plate satisfy the relationship of the following formula (1), and a plate thickness T (mm) of the steel plate and an inclination angle β of the steel plate satisfy the relationship of the following formula (2),
Manufacturing method of processed material 0°<α≦13.0°/T ^0.7 ... (1)
0°≦β≦7.5°/T ^0.7 ... (2)
Disclose.

The manufacturing method disclosed herein may include disposing the steel plate between the first blade and the second blade, and between a pressing member and the second blade, where the pressing member has a pressing surface that contacts the first surface.

In the manufacturing method disclosed herein, at the time when a crack is generated in the steel plate by the first blade and the second blade, a gap may exist at least either between the pressing member and the steel plate or between the steel plate and the second blade.

In the manufacturing method disclosed herein, at the time when a crack is generated in the steel plate by the first blade and the second blade, a gap larger than the plate thickness T may exist between the pressing member and the second blade.

The manufacturing method disclosed herein may include disposing a support mechanism between the pressing member and the second blade to provide a gap greater than the plate thickness T.

In the manufacturing method disclosed herein, at the time when a crack is generated in the steel plate by the first blade and the second blade, the second blade and the pressing member may face each other with a gap therebetween, and the gap may have a relatively small portion and a relatively large portion, and when the portion with the relatively small gap is defined as the first portion, the gap may increase continuously or intermittently from the first portion toward the tip of the second blade.

The manufacturing method disclosed herein may include disposing a spacer at least one between the pressing member and the steel plate and between the steel plate and the second blade.

In the manufacturing method disclosed herein, the pressing member may have a recessed step at its tip.

In the manufacturing method disclosed herein, the second blade may have a recessed step at its tip.

In the manufacturing method disclosed herein, the tensile strength of the steel plate may be 980 MPa or more.

In the manufacturing method disclosed herein, the tensile strength of the steel plate may be 1470 MPa or more.

According to the manufacturing method disclosed herein, when a steel plate is sheared to obtain a processed material, it is possible to reduce the tensile residual stress at the fracture surface of the processed material. Furthermore, even when the processed material has multiple sheared end surfaces, it is possible to suppress variation in the properties of the multiple sheared end surfaces.

1 is a schematic diagram for explaining an example of a flow of shear processing, in which (A) shows a state in which the first blade and the second blade are separated and a steel plate is disposed between the first blade and the second blade, (B) shows a state in which the first blade and the second blade are moved relatively and brought closer to each other to punch out a part of the steel plate, (C) shows a state in which the first blade and the second blade are separated and returned to the position of (A), and (D) shows a state in which the steel plate is still disposed between the first blade and the second blade. 1 is a schematic diagram for explaining an example of a mechanism for forming a sheared end surface when a steel plate is sheared. The cross section is along the relative movement direction of the first blade and the second blade, and shows the form of the cross section including the first blade, the second blade, and the steel plate. (A) shows a state in which a sag is formed in the steel plate by pressing the first blade and the second blade against the steel plate, (B) shows a state in which a crack is generated in the steel plate by further pressing the first blade and the second blade against the steel plate after the sag is formed, and (C) shows a state in which the shearing of the steel plate is completed by further pressing the first blade and the second blade against the steel plate after the crack is formed. Schematic diagrams for explaining new findings by the inventors. (A) shows a case where the crack propagates from the first blade, (B) shows a case where the crack propagates from both the first blade and the second blade, and (C) shows a case where the crack propagates from the second blade. "◯" means that the tensile residual stress is extremely small, "△" means that the tensile residual stress is small, and "×" means that the tensile residual stress is large. 1A and 1B are schematic cross-sectional views for explaining the relationship between the inclination angle β and the propagation direction of a crack, in which (A) shows a case where the inclination angle β is large and (B) shows a case where the inclination angle β is small. 1 is a schematic diagram for explaining a method for manufacturing a workpiece, which shows a cross section along a relative movement direction of a first blade and a second blade, including the first blade, the second blade, and a steel plate, and shows a state at a time when a crack is generated in the steel plate by the first blade and the second blade. 1 is a schematic diagram for explaining a clearance and a shear angle, in which (A) shows the clearance and (B) shows the shear angle. 1 is a schematic diagram for explaining an example of a method for measuring an inclination angle α and a tilt angle β. FIG 2 shows a cross-sectional shape of a steel plate after shearing. 4 is a schematic diagram for explaining a pressing member used in the method for manufacturing a processed material. FIG. 1 is a schematic diagram for explaining an example of the state of a steel plate etc. at the time when a crack is generated in the steel plate by a first blade and a second blade, (A) shows a case where a gap is provided between the pressing member and the steel plate or between the steel plate and the second blade, and (B) shows a case where the distance between the pressing member and the second blade is larger than the distance between the first surface and the second surface of the steel plate. 11 is a schematic diagram for explaining an example of a support mechanism disposed between the pressing member and the second blade. FIG. 10 is a schematic diagram for explaining an example of a distance between a pressing member and a second blade. FIG. 1A is a schematic diagram for explaining an example of a spacer, and FIG. 1B is a schematic diagram for explaining an example of a spacer, and FIG. 1A shows an example of a spacer disposed between a pressing member and a steel plate, and FIG. 1B shows an example of a spacer disposed between the steel plate and a second blade. 1A is a schematic diagram for explaining an example of a step provided on the pressing member and the second blade, in which (A) shows a case where a step that sinks into the tip of the pressing member is provided, and (B) shows a case where a step that sinks into the tip of the second blade is provided. 1 is a schematic cross-sectional view for explaining an example of the configuration of a processed material produced by the production method of the present disclosure. FIG. 1 is a schematic diagram for explaining an example of a configuration of a sheared end surface of a processed material according to the present disclosure, showing the sheared end surface as viewed from the front. 1A is a schematic diagram for explaining a method for distinguishing between a first portion and a second portion on a fracture surface, in which (A) shows a schematic diagram of the direction of hydrogen embrittlement cracking occurring on the fracture surface, and (B) shows a schematic diagram of the relationship between an arbitrary position X between the sag side and the burr side on the fracture surface and the direction (angle θ) of the hydrogen embrittlement cracking. FIG. 1 is a diagram for explaining a method for measuring a tensile residual stress.

1. Problems and new findings A workpiece having a sheared end surface can be obtained, for example, as follows. First, as shown in FIG. 1(A), a steel plate 5 is placed between a first blade 21 and a second blade 22. Here, the steel plate 5 has a first surface 10a and a second surface 10b opposite to the first surface 10a, the first blade 21 has a first bottom surface 21a, a first side surface 21b, and a first tip portion 21x (see FIG. 2(A)), and the second blade 22 has a second bottom surface 22a, a second side surface 22b, and a second tip portion 22x (see FIG. 2(A)). As shown in FIGS. 1(A) and 1(B), the first bottom surface 21a is placed on the first surface 10a side of the steel plate 5, and the second bottom surface 22a is placed on the second surface 10b side of the steel plate 5. The first blade 21 may be a punch, and the second blade 22 may be a die. Next, as shown in Fig. 1(B), the first blade 21 and the second blade 22 are moved relative to each other to shear the steel plate 5. As a result, as shown in Fig. 1(C), a part of the steel plate 5 is sheared, and a processed material 10 is obtained. As shown in Figs. 1(C) and (D), the first blade 21 and the second blade 22 may be separated from each other, and the steel plate 5 may be placed between the first blade 21 and the second blade 22 again to shear the steel plate 5. By repeating Figs. 1(A) to (D), a plurality of processed materials 10 having a first sheared end surface 1 and a second sheared end surface 2 may be obtained.

1(A) to (D) show a form in which no shear angle is provided between the first blade 21 and the second blade 22, but a shear angle may be provided between the first blade 21 and the second blade 22. Also, in FIG. 1(A) to (D), a form in which the intersection line (tip of the first blade 21) between the first bottom surface 21a and the first side surface 21b of the first blade 21 extends linearly in the longitudinal direction of the first blade 21 is shown, but the tip of the first blade 21 may extend curvedly in the longitudinal direction. That is, the shearing may be performed so that the shape of the sheared end faces 1 and 2 in a plan view is linear, or curved, or a combination of linear and curved. Also, in FIG. 1(A) to (D), a form in which the workpiece 10 is punched out by the first blade 21 is shown, but a punched hole, a slit, or the like may be formed in a part of the steel plate 5 by shearing the steel plate 5 with the first blade 21 and the second blade 22. In this case too, the processed material 10 can have sheared end surfaces 1 and 2.

An example of the mechanism for forming the sheared end faces 1 and 2 will be described. As shown in Figures 2(A) to (C), consider the case where the first blade 21 and the second blade 22 shear the steel plate 5 to form the sheared end faces 1 and 2. As shown in Figure 2(A), the first bottom surface 21a of the first blade 21 is pressed against the first surface 10a of the steel plate 5, forming a sagging 1a on the first surface 10a side of the steel plate 5. The sagging 1a is formed in the process until the first tip portion 21x of the first blade 21 bites into the steel plate 5. After the sagging 1a is formed, the sheared surface 1e (see Figure 14) may be formed in the process in which the first tip portion 21x bites into the steel plate 5. As shown in Figure 2(B), after the sagging 1a and the sheared surface 1e are formed, a first crack 1dx occurs from the first blade 21 side toward the second blade 22 side. On the other hand, on the second blade 22 side, after the second tip 22x bites into the second surface 10b of the steel plate 5, a second crack 1dy occurs from the second blade 22 side toward the first blade 21 side. As shown in FIG. 2C, the first crack 1dx and the second crack 1dy each progress and join with each other to form a fracture surface 1b. In addition, by further moving the first blade 21 and the second blade 22, a part of the steel plate 5 is separated as the processed material 10. At this time, as shown in FIG. 2C, a burr 1c may be formed at the corner of the sheared end surface 1 on the second blade 22 side. On the other hand, the second sheared end surface 2 is also formed in the same manner as above. As shown in FIG. 2C, the second sheared end surface 2 has a sag 2a on the second surface 10b side and a burr 2c on the first surface 10a side, and may have a fracture surface 2b and an arbitrary shear surface between them. The fracture surface 2b is formed when the first crack 1dx and the second crack 1dy grow and join together. As shown in Figures 2(A) to (C), the second shearing end surface 2 can be formed simultaneously with the first shearing end surface 1. The shearing end surfaces 1 and 2 can be formed by the mechanism shown in Figures 2(A) to (C), regardless of the presence or absence of a shear angle between the first blade 21 and the second blade 22, or the shape of the shearing end surface 1 in plan view (straight line, curved line, or a combination of these, punched hole, slit, etc.).

In the sheared end faces 1 and 2 formed as described above, compressive residual stress and tensile residual stress may occur due to damage and distortion caused by shearing. If large tensile residual stress exists in the sheared end faces 1 and 2, the hydrogen embrittlement resistance or fatigue strength of the sheared end faces 1 and 2 may decrease. In this regard, in order to obtain a processed material 10 with high performance, one issue may be how to reduce the tensile residual stress in the sheared end faces 1 and 2. In particular, as disclosed in Patent Document 1, it is desirable to reduce the tensile residual stress in the fracture surfaces 1b and 2b of the sheared end faces 1 and 2.

The inventors conducted numerous experiments and analyses on the relationship between the shear conditions of the steel plate 5 and the properties of the sheared end faces 1 and 2 produced by the shear, and as a result, obtained the following new findings.

As shown in Figures 3(A) to (C), a case will be described in which a part (first part) 11 of the steel plate 5 is punched out by the first blade 21 and another part (second part) 12 of the steel plate 5 is punched out by the second blade 22. In this case, as shown in Figure 3(A), if the crack propagates preferentially from the first blade 21 side, the tensile residual stress at the shear end surface of the part 11 becomes large, while the tensile residual stress at the shear end surface of the other part 12 becomes extremely small. In other words, the part 11 is scrapped, while the other part 12 can be suitably used as a product. Also, as shown in Figure 3(B), if the crack propagates equally from both the first blade 21 side and the second blade 22 side, the same small tensile residual stress can be generated at the shear end surfaces of both the part 11 and the other part 12. In other words, the variation in properties between the part 11 and the other part 12 is suppressed. In this respect, it can be said to be suitable for using both the part 11 and the other part 12 as products. Furthermore, as shown in FIG. 3(C), if the crack propagates preferentially from the second blade 22 side, the tensile residual stress at the sheared end surface of the other part 12 becomes large, while the tensile residual stress at the sheared end surface of the part 11 becomes extremely small. In other words, the other part 12 is scrapped, while the part 11 can be suitably used as a product.

Based on the above findings, the present inventors have found the following (1) to (3).
(1) The tensile residual stress generated at the fracture surfaces 1b and 2b of the sheared edges 1 and 2 varies depending on the propagation direction and length of the cracks 1dx and 1dy that form the fracture surface 1b.
(2) At the fracture surfaces 1b and 2b, the more equivalent the length of the crack 1dx propagating from the sag 1a side (first blade side) and the length of the crack 1dy propagating from the burr 1c side (second blade side) are, the more the variation in the properties of the shear end surfaces 1 and 2 is suppressed, and the more the tensile residual stress of the fracture surfaces 1b and 2b is reduced at both shear end surfaces 1 and 2.
(3) In other words, in the case where the area ratio of the portion originating from the first crack 1dx propagating from the sag 1a side (burr 2c side) in the fracture surfaces 1b, 2b of the processed material 10 is equivalent to the area ratio of the portion originating from the second crack 1dy propagating from the burr 1c side (sag 2a side), the tensile residual stress in the fracture surfaces 1b, 2b can be reduced in both the first shear end surface 1 and the second shear end surface 2.

The inventors conducted numerous experiments and analyses to control the propagation direction and length of cracks 1dx and 1dy when steel plate 5 is sheared, and as a result obtained the following new findings:

As shown in Figures 4(A) and (B), the propagation direction and length of the cracks 1dx and 1dy change depending on the inclination angle β of the steel plate 5 that occurs during shearing. Specifically, when the steel plate 5 is significantly bent by the indentation of the blades 21 and 22 during shearing and the inclination angle β becomes large, as shown by the white arrow in Figure 4(A), the crack 1dx tends to propagate from the first blade 21, and the variation in properties between the first shear end face 1 and the second shear end face 2 tends to become large. On the other hand, when the bending of the steel plate 5 due to the indentation of the blades 21 and 22 during shearing is small and the inclination angle β becomes small, as shown by the white arrow in Figure 4(B), the cracks 1dx and 1dy tend to propagate from both the first blade 21 and the second blade 22, and the variation in properties between the first shear end face 1 and the second shear end face 2 tends to be suppressed.

Based on the above findings, the inventors conducted numerous experiments and analyses on the relationship between the shear conditions of the steel plate 5 and the inclination angle β of the steel plate 5 that occurs during shearing, and discovered that the inclination angle β can be easily reduced by shearing the steel plate 5 in an inclined state (a state in which the inclination angle α, described below, is greater than 0°).

The inventors have also found that the upper limit values of the inclination angle α and the inclination angle β, which can suppress the variation in the properties of the sheared end faces 1 and 2 of the processed material 10 after shearing, change depending on the thickness T of the steel plate 5. In other words, the upper limit values of the inclination angle α and the inclination angle β of the steel plate 5 can be expressed as a function of the plate thickness T, and by setting each of the inclination angle α and the inclination angle β to be equal to or less than the upper limit value expressed by the function, when the steel plate 5 is sheared, it becomes easier to propagate the cracks 1dx and 1dy from both the first blade 21 and the second blade 22, and it becomes easier to suppress the variation in the properties of the first sheared end face 1 and the second sheared end face 2.

2. Manufacturing method of processed material The manufacturing method disclosed herein is a method for manufacturing a processed material 10 by shearing a steel plate 5,
A steel plate 5 is disposed between the first blade 21 and the second blade 22, where the steel plate 5 has a first surface 10a and a second surface 10b opposite to the first surface 10a, and the first surface 10a is disposed on the first blade 21 side and the second surface 10b is disposed on the second blade 22 side ( FIG. 1(A) ); and
Shearing the steel plate 5 by moving the first blade 21 and the second blade 22 relative to each other ( FIG. 1(B) );
5(A) and 5(B), in the manufacturing method of the present disclosure, it is important that, at the time when a crack is generated in the steel plate 5 by the first blade 21 and the second blade 22, the plate thickness T (mm) of the steel plate 5 and the inclination angle α of the steel plate 5 satisfy the relationship of the following formula (1), and that the plate thickness T (mm) of the steel plate 5 and the inclination angle β of the steel plate 5 satisfy the relationship of the following formula (2).
0°<α≦13.0°/T ^0.7 ... (1)
0°≦β≦7.5°/T ^0.7 ... (2)

2.1 First Blade The first blade 21 may have a first bottom surface 21a, a first side surface 21b, and a first tip portion 21x. The first bottom surface 21a may have a surface that intersects with the relative movement direction of the first blade 21, or may have a surface that is perpendicular to the movement direction. The first side surface 21b may have a surface that is aligned with the relative movement direction of the first blade 21, or may have a surface that is inclined with respect to the movement direction. The first tip portion 21x refers to a portion near the intersection line between the first bottom surface 21a and the first side surface 21b. For example, the first tip portion 21x may be a portion that is within a range of 2 mm from the intersection line between the first bottom surface 21a and the first side surface 21b toward both the first bottom surface 21a side and the first side surface 21b side. In cases where the tip of the first blade 21 is machined to have an R or where the tip is chamfered, a line of intersection between a surface extending along the first bottom surface 21a and a surface extending along the first side surface 21b can be assumed, and the portion included within a range of R + 2 mm from the line of intersection toward both the first bottom surface 21a side and the first side surface 21b side can be regarded as the first tip portion 21x.

The shape of the first bottom surface 21a can be determined according to the shape of the sheared end surfaces 1, 2 of the target workpiece 10. The first bottom surface 21a may have a flat surface or a curved surface, and the flat surface or the curved surface can face the first surface 10a when the steel plate 5 is sheared.

The shape of the first side surface 21b can be determined according to the shape of the intended shear end surfaces 1, 2 of the processed material 10. The first side surface 21b may have a flat surface or a curved surface.

The first tip 21x may extend in a straight line or a curved line in the longitudinal direction of the first blade 21 (the forward and backward direction of the paper in Figs. 5(A) and (B)), and can be determined according to the shape of the sheared end faces 1, 2 of the target workpiece 10. When a punch hole is provided in the steel plate 5, the shape of the first tip 21x can be annular along the edge of the punch hole.

In a standby state before the shearing operation, the first blade 21 may be positioned above the second blade 22. In this case, the first blade 21 may be a punch that punches out, from top to bottom, a portion of the steel plate 5 placed on the second bottom surface 22a of the second blade 22.

The first blade 21 is made of a material that is generally used for blades in shearing processes. For example, the first blade 21 may be made of SKD11. The first blade 21 may also have a first coating on its surface.

2.2 Second Blade The second blade 22 may have a second bottom surface 22a, a second side surface 22b, and a second tip portion 22x. The second bottom surface 22a may have a surface that intersects with the relative movement direction of the second blade 22, or may have a surface that is perpendicular to the movement direction. The second side surface 22b may have a surface that is aligned with the relative movement direction of the second blade 22, or may have a surface that is inclined with respect to the movement direction. The second tip portion 22x refers to a portion near the intersection line between the second bottom surface 22a and the second side surface 22b. For example, the second tip portion 22x may be a portion that is within a range of 2 mm from the intersection line between the second bottom surface 22a and the second side surface 22b toward both the second bottom surface 22a side and the second side surface 22b side. In cases where the tip of the second blade 22 is machined to have an R or where the tip is chamfered, a line of intersection between a surface extending along the second bottom surface 22a and a surface extending along the second side surface 22b can be assumed, and the portion included within a range of R + 2 mm from the line of intersection toward both the second bottom surface 22a and the second side surface 22b can be regarded as the second tip portion 22x.

The shape of the second bottom surface 22a can be determined according to the shape of the sheared end surfaces 1, 2 of the target workpiece 10. The second bottom surface 22a may have a flat surface or a curved surface, and the flat surface or the curved surface can face the second surface 10b when the steel plate 5 is sheared.

The shape of the second side surface 22b can be determined according to the shape of the intended sheared end surfaces 1, 2 of the processed material 10. The second side surface 22b may have a flat surface or a curved surface.

The second tip 22x may extend linearly or curvedly in the longitudinal direction of the second blade 22 (into the paper in Figs. 5(A) and (B)) and can be determined according to the shape of the sheared end faces 1, 2 of the target workpiece 10. When a punch hole is provided in the steel plate 5, the shape of the second tip 22x can be annular along the edge of the punch hole.

In a standby state before the shearing operation, the second blade 22 may be positioned below the first blade 21. In this case, the second blade 22 may be a die on which the steel plate 5 is placed.

The second blade 22 is made of a material that is generally used for blades in shearing processes. For example, the second blade 22 may be made of SKD11. The second blade 22 may also have a second coating on its surface.

2.3 Steel Plate The thickness T of the steel plate 5 is not particularly limited and may be appropriately determined depending on the application of the processed material 10. The thickness T of the steel plate 5 may be, for example, 0.5 mm or more, 0.8 mm or more, or 1.0 mm or more, and may be 15 mm or less, 10 mm or less, 6.0 mm or less, or 3.0 mm or less. The steel plate 5 may be formed into some shape by bending or the like.

As shown in FIG. 5(A), the steel plate 5 has a first surface 10a and a second surface 10b opposite to the first surface 10a. The first surface 10a and the second surface 10b may be parallel to each other. Note that "parallel" in this application is not limited to perfect parallelism, but may mean substantially parallelism. In other words, even if the first surface 10a and the second surface 10b are not perfect parallelism, they are considered to be parallel as long as the difference is within the range of tolerance allowed in industrial production. Specifically, when the angle between the first surface 10a and the second surface 10b is 0°±1°, the first surface 10a and the second surface 10b are considered to be parallel.

The steel plate 5 may have a surface treatment layer. Examples of the surface treatment layer include a plating layer and a coating film. The steel plate 5 may also include multiple layers of different steel types. For example, clad steel may be used as the steel plate 5.

The mechanical properties of the steel plate 5 are not particularly limited, and may be appropriately determined depending on the application of the steel plate 5. However, the problem of reduced hydrogen embrittlement resistance or fatigue strength due to tensile residual stress is particularly likely to occur in high-strength steel plates. In this regard, the tensile strength of the steel plate 5 may be, for example, 980 MPa or more, 1180 MPa or more, or 1470 MPa or more. The upper limit of the tensile strength of the steel plate 5 is not particularly limited, but may be, for example, 2500 MPa or less, 2200 MPa or less, or 2000 MPa or less. The "tensile strength" of the steel plate in this application is in accordance with ISO 6892-1:2009.

The chemical composition and metal structure of the steel plate 5 are not particularly limited and may be appropriately determined depending on the application of the processed material 10. According to the technology disclosed herein, the tensile residual stress at the fracture surfaces 1b and 2b can be reduced regardless of the chemical composition and metal structure of the steel plate 5. As an example of the chemical composition, the steel plate 5 has, in mass %, C: 0.050-0.800%, Si: 0.01-3.00%, Mn: 0.01-10.00%, Al: 0.001-0.500%, P: 0.100% or less, S: 0.050% or less, N: 0.010% or less, Cr: 0-3.000%, Mo: 0-1.000%, B: 0-0.0100%, Ti: 0-0.500%, Nb: 0-0.500%, V: 0-0.500%, Cu: 0-0.50 %, Ni: 0-0.50%, O: 0-0.020%, W: 0-0.100%, Ta: 0-0.10%, Co: 0-0.50%, Sn: 0-0.050%, Sb: 0-0.050%, As: 0-0.050%, Mg: 0-0.050%, Ca: 0-0.050%, Y: 0-0.050%, Zr: 0-0.050%, La: 0-0.050%, Ce: 0-0.050%, and the balance: Fe and impurities. In addition, in the above chemical composition of steel plate 5, the lower limit of the content of the optionally added elements Cr, Mo, B, Ti, Nb, V, Cu, Ni, O, W, Ta, Co, Sn, Sb, As, Mg, Ca, Y, Zr, La, and Ce may be 0.0001% or 0.001%.

2.4 Arrangement of Steel Plate In the manufacturing method of the present disclosure, the steel plate 5 is arranged between the first blade 21 and the second blade 22 as described above. Here, as shown in Fig. 1(A), the first surface 10a of the steel plate 5 is arranged on the first blade 21 side, and the second surface 10b is arranged on the second blade 22 side. There is no particular restriction on the arrangement of the steel plate 5 between the first blade 21 and the second blade 22, as long as the steel plate 5 is arranged so as to be appropriately sheared. For example, as shown in Fig. 1(A), the steel plate 5 may be placed on the bottom surface 22a of the second blade 22 while the first blade 21 is arranged above the steel plate 5.

2.5 Actions and Relationship Between the First Blade and the Second Blade During Shearing In the manufacturing method disclosed herein, after the steel plate 5 is placed between the first blade 21 and the second blade 22, the first blade 21 and the second blade 22 are moved relatively to each other to shear the steel plate 5. The relative movement of the first blade 21 and the second blade 22 may be performed by a moving device (not shown). Alternatively, at least one of the first blade 21 and the second blade 22 may be moved manually.

2.5.1 Clearance As shown in FIG. 6A, a clearance C may be provided between the first blade 21 and the second blade 22 during shearing. The clearance C may be appropriately determined depending on the material, shape, etc. of the steel plate 5. For example, when the steel plate 5 is plate-shaped, the clearance C may be 5% or more of the thickness of the steel plate 5, or may be 30% or less of the thickness of the steel plate 5. In addition, according to the inventor's new findings, when the clearance C is 5% or more and 15% or less of the thickness of the steel plate 5, the first crack 1dx and the second crack 1dy are easily allowed to grow equally in the steel plate 5. Note that the "clearance" referred to in this application is in accordance with ISO 16630:2009.

2.5.2 Shear angle As shown in Fig. 6(B) , a shear angle θs may be provided between the first blade 21 and the second blade 22 during shearing. The shear angle θs may be appropriately determined depending on the material, shape, etc. of the steel plate 5. For example, the shear angle θs may be 0° or more and 5° or less. Furthermore, according to the inventor's new findings, when the shear angle θs is 1° or more and 2° or less, the first crack 1dx and the second crack 1dy are easily allowed to propagate equally in the steel plate 5.

2.6 Tilt Angle and Inclination Angle As shown in FIGS. 5(A) and 5(B), in the manufacturing method of the present disclosure, it is important that, at the time when a crack is generated in the steel plate 5 by the first blade 21 and the second blade 22, the plate thickness T (mm) of the steel plate 5 and the inclination angle α of the steel plate 5 satisfy the relationship of the following formula (1), and that the plate thickness T (mm) of the steel plate 5 and the inclination angle β of the steel plate 5 satisfy the relationship of the following formula (2).
0°<α≦13.0°/T ^0.7 ... (1)
0°≦β≦7.5°/T ^0.7 ... (2).

In the present application, the "inclination angle α" and the "inclination angle β" can be specified, for example, based on the traveling direction of the first blade 21 and the second blade, as follows. First, as shown in Figures 5(A) and (B), in a cross section including the first blade 21, the second blade 22, and the steel plate 5, which is perpendicular to the extending direction of the tips 21x and 22x, the relative movement direction of the first blade 21 and the second blade 22 is the Y direction, and the direction perpendicular to the Y direction is the X direction. In addition, the part of the steel plate 5 that is pressed by the first blade 21 (if the first blade 21 is a punch, the part that is punched out by the punch) is the first part 11, and the part that is pressed by the second blade 22 (if the second blade 22 is a die, the part that remains on the die) is the second part 12. Furthermore, at the time when the first blade 21 and the second blade 22 cause a crack in the steel plate 5, the first portion 11 held by the first blade 21 is tilted toward the moving direction of the first blade 21, and the steel plate 5 is bent at the boundary between the first portion 11 and the second portion 12. In this state, as shown in Figs. 5(A) and (B) , in the above cross section, the angle between the line L1 along the X direction and the line L2 along the extension direction of the second portion 12 is defined as the "inclination angle α". In addition, the angle between the line L2 along the extension direction of the second portion 12 and the line L3 along the extension direction of the first portion 11 is defined as the "inclination angle β" (the angle obtained by subtracting the inclination angle α from the angle between the line L1 along the X direction and the line L3 along the extension direction of the first portion 11 is defined as the "inclination angle β"). In the case where the first portion 11 and the second portion 12 extend in a curved shape in the above cross section due to the bending of the steel plate 5 or a pressing member (not shown), as shown in FIG. 5(B), in specifying L2 and L3, it is sufficient to use the "tangent" related to the extension direction of each portion 11, 12 at the boundary between the first portion 11 and the second portion 12. Note that, as shown in FIG. 5(A) and (B), in the above cross section, the straight line obtained by connecting the centers in the thickness direction of the steel plate 5 (centroid in the thickness direction) is regarded as the "extension direction" of the steel plate 5.

Alternatively, in the present application, the "inclination angle α" and the "inclination angle β" can be determined, for example, based on the shape of the sheared end face after shearing, as follows. Figures 7(A) and (B) show an example of a method for determining the inclination angle α and the inclination angle β based on the shape of the sheared end face. Figure 7(A) shows a case where the clearance is small, and Figure 7(B) shows a case where the clearance is large. As shown in Figures 7(A) and (B), the angle γ between the first surface 10a of the first portion 11 and the sheared surface of the sheared end face 2 is determined. Also, the angle α (which coincides with the "inclination angle α") between the second surface 10b of the second portion 12 and the shape of the second surface 10b near the burr of the sheared end face 1, which extends from the burr to the second portion 12 side (the shape of the surface pressed by the second bottom surface of the second blade) is determined. In this case, the "inclination angle β" can be determined as β = 90° - α - γ.

In this manner, in the manufacturing method of the present disclosure, when the steel plate 5 is sheared, the inclination angle β can be reduced by providing a predetermined inclination angle α to the steel plate 5, and the cracks 1dx and 1dy can be easily propagated from both the first blade 21 and the second blade 22. As a result, the variation in the properties of the sheared end faces 1 and 2 is suppressed, and the tensile residual stress in the fracture surfaces 1b and 2b of the sheared end faces 1 and 2 is reduced. In the manufacturing method of the present disclosure, the inclination angle α and the inclination angle β may be within a range that satisfies the above formulas (1) and (2), and may be appropriately determined according to the plate thickness. The inclination angle α may be more than 0°, 1° or more, 2° or more, 3° or more, or 4° or more, and may be 15° or less, 12° or less, or 10° or less. The inclination angle β may be 10° or less, 8° or less, or 6° or less, and may be 0° or more, more than 0°, 2° or more, or 4° or more.

2.7 Control of the inclination angle and the inclination angle Various methods are possible for controlling the inclination angle α and the inclination angle β within the above range when the steel plate 5 is sheared. For example, as shown in Fig. 5 (A), a form in which a part of the second surface 10b of the steel plate 5 is raised from the second bottom surface 22a when the steel plate 5 is sheared can be mentioned. In addition, a specific pressing member to be described later may be adopted, the second blade 22 may be provided with a specific shape, or other members may be arranged. An example of a method capable of controlling the inclination angle α and the inclination angle β within a specific range will be described below.

2.7.1 Pressing member As shown in FIG. 8, the manufacturing method of the present disclosure may include arranging the steel plate 5 between the first blade 21 and the second blade 22 and between the pressing member 31 and the second blade 22, where the pressing member 31 has a pressing surface 31a that contacts the first surface 10a. The pressing member 31 may be capable of appropriately pressing a part of the first surface 10a of the steel plate 5, and the specific shape, size, etc. are not particularly limited. The pressing surface 31a may be a flat surface, a curved surface, or a combination of a flat surface and a curved surface. The pressing member 31 may be connected to a known moving device or the like and be movable relative to the second bottom surface 22a of the second blade 22. That is, the pressing member 31 can be brought relatively close to the second bottom surface 22a to press the steel plate 5 against the second bottom surface 22a.

2.7.2 Distance or gap between the pressing member and the second blade When the pressing member 31 is used, as shown in FIG. 9(A), at the time when the first blade 21 and the second blade 22 cause a crack in the steel plate 5, there may be a gap G1 or G2 between the pressing member 31 and the steel plate 5 and between the steel plate 5 and the second blade 22. Alternatively, as shown in FIG. 9(B), at the time when the first blade 21 and the second blade 22 cause a crack in the steel plate 5, there may be a gap I between the pressing member 31 and the second blade 22 that is larger than the plate thickness T (the distance between the first surface 10a and the second surface 10b). In this way, when the first blade 21 and the second blade 22 cause a crack in the steel plate 5, the predetermined gaps G1 and G2 or the gap I between the pressing member 31 and the second blade 22 make it easy to control the inclination angle α and the inclination angle β within the above range.

2.7.3 Support Mechanism Furthermore, when the pressing member 31 is used, as shown in Fig. 10, the manufacturing method of the present disclosure may include arranging a support mechanism 41 between the pressing member 31 and the second blade 22 to provide a gap I larger than the plate thickness T (the distance between the first surface 10a and the second surface 10b). The support mechanism 41 only needs to have a shape, rigidity, etc. that can hold the pressing member 31 and the second blade 22 at a predetermined gap I. In this way, even when a predetermined support mechanism 41 is arranged between the pressing member 31 and the second blade 22, it is easy to control the inclination angle α and the tilt angle β within the above range.

11(A) and (B), when the pressing member 31 is used, at the time when a crack is generated in the steel plate 5 by the first blade 21 and the second blade 22, the second blade 22 and the pressing member 31 face each other with a gap I therebetween, and the gap I has a relatively small portion and a relatively large portion, and if the portion where the gap I is relatively small is defined as the first portion (narrow portion) F, the gap I may increase continuously or intermittently from the first portion F toward the tip of the second blade 22. In this way, even when the gap I is increased at the tip of the second blade 22, it is easy to control the inclination angle α and the tilt angle β within the above range.

2.7.5 Spacer Furthermore, when the pressing member 31 is used, as shown in Figures 12 (A) and (B), the manufacturing method of the present disclosure may include arranging spacers 51, 52 at least one of between the pressing member 31 and the steel plate 5 and between the steel plate 5 and the second blade 22. The size and shape of the spacers 51, 52 are not particularly limited as long as they can provide a desired gap between the pressing member 31 and the steel plate 5 or between the steel plate 5 and the second blade 22. In this way, even when the spacers 51, 52 are arranged at a predetermined position between the pressing member 31 and the second blade 22, it is easy to control the inclination angle α and the tilt angle β within the above range.

2.7.6 Step As shown in Fig. 13(A), the pressing member 31 may have a recessed step 35 at its tip. The position, depth and size of the step 35 (range in which the step 35 is provided) are not particularly limited and may be determined appropriately depending on the shape of the steel plate 5, etc. By recessing the tip of the pressing member 31 to provide the step 35 in this way, it is easy to control the inclination angle α and the tilt angle β within the above ranges even when the gap I between the pressing member 31 and the second blade 22 at the tip is widened.

As shown in FIG. 13(B), the second blade 22 may have a recessed step 25 at its tip. The position, depth, and size of the step 25 (the range in which the step 25 is provided) are not particularly limited and may be determined appropriately depending on the shape of the steel plate 5, etc. Even in such a case, the inclination angle α and the inclination angle β can be set within the above range. Note that although a pressing member 31 is shown in FIG. 13(B), when a step 25 is provided at the tip of the second blade 22, it is easy to control the inclination angle α and the inclination angle β within the above range even without the pressing member 31.

3. An example of the properties of the processed material According to the manufacturing method of the present disclosure, the variation in the properties of the first sheared end surface 1 and the second sheared end surface 2 can be reduced, and the tensile residual stress can be reduced at the fracture surfaces 1b and 2b of both sheared end surfaces 1 and 2. The first sheared end surface 1 and the second sheared end surface 2 can have the same configuration. Below, an example of the configuration of the first sheared end surface 1 of the processed material 10 will be described, but the form of the processed material obtained by the manufacturing method of the present disclosure is not limited to the following form. As shown in Figures 14 and 15, the first sheared end surface 1 of the processed material 10 has a sag 1a, a fracture surface 1b, and a burr 1c. The fracture surface 1b includes a first fracture portion 1bx and a second fracture portion 1by. The first fracture portion 1bx is formed by a first crack 1dx that has progressed from the sag 1a side to the burr 1c side, and the second fracture portion 1by is formed by a second crack 1dy that has progressed from the burr 1c side to the sag 1a side. As described above, according to the manufacturing method of the present disclosure, by setting the inclination angle α and the tilt angle β within the above ranges, the length of the first crack 1dx and the length of the second crack 1dy tend to be equal to each other.

As shown in Figures 14 and 15, the first sheared end surface 1 has a sag 1a, a fracture surface 1b, and a burr 1c. The first sheared end surface 1 may also have a sheared surface 1e. The sag 1a, burr 1c, and sheared surface 1e of the first sheared end surface 1 may have any shape depending on the shape of the processed material 10. The sag 1a, burr 1c, and sheared surface 1e may have the same shape as conventional ones.

The processed material 10 has one characteristic in the configuration of the fracture surface 1b of the first shear end surface 1. As shown in Figures 14 and 15, the fracture surface 1b includes a first fracture portion 1bx and a second fracture portion 1by. The first fracture portion 1bx is formed by a first crack 1dx that has progressed from the sag 1a side to the burr 1c side, and the second fracture portion 1by is formed by a second crack 1dy that has progressed from the burr 1c side to the sag 1a side.

The propagation direction of the first crack 1dx may be from the sag 1a side to the burr 1c side. When the processed material 10 is plate-shaped, the propagation direction of the first crack 1dx may be along the thickness direction of the processed material 10 (perpendicular to the first surface 10a and the second surface 10b) or inclined to the thickness direction. The propagation direction of the second crack 1dy may be from the burr 1c side to the sag 1a side. When the processed material 10 is plate-shaped, the propagation direction of the second crack 1dy may be along the thickness direction of the processed material 10 (perpendicular to the first surface 10a and the second surface 10b) or inclined to the thickness direction. For example, when the steel plate 5 is sheared, if a clearance C is provided between the first blade 21 and the second blade 22, the propagation direction of the first crack 1dx and the second crack 1dy may be inclined relative to the plate thickness direction, and the larger the clearance, the greater the inclination.

The first crack 1dx only needs to start from the sag 1a side and progress toward the burr 1c side, and join with the second crack 1dy on the burr 1c side; it does not necessarily have to progress along the shortest path from the sag 1a side to the second crack 1dy on the burr 1c side. For example, the first crack 1dx may progress toward the back of the page in FIG. 2(B) (for example, in the plate width direction, if the processed material 10 is plate-shaped) as it progresses from the sag 1a side to the burr 1c side. The same applies to the second crack 1dy.

In the first shear end surface 1, the area ratio X1 of the first fracture portion 1bx in the fracture surface 1b may be equal to the area ratio X2 of the second fracture portion 1by in the fracture surface 1b. In other words, in the first shear end surface 1, the average length of the first cracks 1dx that have progressed from the sag 1a side toward the burr 1c side may be equal to the average length of the second cracks 1dy that have progressed from the burr 1c side toward the sag 1a side. As described above, when the area ratios X1 and X2 are equal, the variation in the properties of the shear end surfaces 1 and 2 can be suppressed, and the tensile residual stress in the fracture surface 1b can be reduced.

In addition, when determining the area ratio of each of the first fracture portion 1bx and the second fracture portion 1by on the fracture surface 1b and the length of each of the first crack 1dx and the second crack 1dy, the unevenness of the surface of the fracture surface 1b is not taken into consideration. For example, as shown in FIG. 15, when the first shear end surface 1 is viewed from the front, if the position of the starting point of the first crack 1dx is P1, the position of the starting point of the second crack 1dy is P2, and the position where the first crack 1dx and the second crack 1dy join is P3, the ratio of the space between P1 and P2 to the space between P1 and P2 can be regarded as the area ratio X1 of the first fracture portion 1bx, and the ratio of the space between P2 and P3 to the space between P1 and P2 can be regarded as the area ratio X2 of the second fracture portion 1by.

According to the inventor's findings, the more similar the area ratio X1 of the first fracture portion 1bx in the fracture surface 1b and the area ratio X2 of the second fracture portion 1by in the fracture surface 1b are, the more the variation in the properties of the sheared end surfaces 1 and 2 can be suppressed.

The burr 1c may be so large that it cannot be seen with the naked eye. Which of the first surface 10a and the second surface 10b of the processed material 10 is the surface on the sag 1a side and which is the surface on the burr 1c side can be easily determined by observing the shape of the processed material 10, even if the burr 1c cannot be seen.

In the first sheared end surface 1, the sheared surface 1e and the fractured surface 1b have different properties. For example, the roughness (glossiness) of the sheared surface 1e and the fractured surface 1b are different. In this regard, the sheared surface 1e and the fractured surface 1b can be easily distinguished from each other just by observing their appearance.

In the fracture surface 1b, the boundary between the first fracture portion 1bx and the second fracture portion 1by (the position where the first crack 1dx and the second crack 1dy join) can be determined, for example, by introducing a large amount of hydrogen into the first shear end surface 1. As described above, the stress generated during the propagation of the crack depends on the propagation direction of the crack. That is, as shown in Figures 16(A) and (B), it can be said that the residual stress suddenly changes at the position where the first crack 1dx and the second crack 1dy join. Therefore, the direction of the hydrogen embrittlement crack caused by the penetration of hydrogen also suddenly changes at the position where the first crack 1dx and the second crack 1dy join. Considering this, the position where the direction of the hydrogen embrittlement crack suddenly changes can be regarded as the position where the first crack 1dx and the second crack 1dy join.

The processed material 10 may have the first shear end surface 1, and the configuration other than the first shear end surface 1 is not particularly limited. As described above, the processed material 10 may have an end surface other than the first shear end surface 1 (for example, the second shear end surface 2). The shape of the processed material 10 corresponds to the shape of the steel plate 5 described above. That is, the processed material 10 may have a plate-shaped portion as described above. In addition, the processed material 10 may have a first surface 10a and a second surface 10b opposite to the first surface 10a as surfaces other than the shear end surfaces 1 and 2, and the first surface 10a and the second surface 10b may be connected via the shear end surfaces 1 and 2. The first surface 10a and the second surface 10b may be parallel to each other. The processed material 10 may also have a surface treatment layer as described above. The processed material 10 may also include multiple layers of different steel types. An example of the mechanical properties and chemical composition of the processed material 10 is also as described above.

The steel plates prepared were steel plate A with a tensile strength of 1470 MPa, steel plate B with a tensile strength of 1310 MPa, steel plate C with a tensile strength of 1180 MPa, and steel plate D with a tensile strength of 980 MPa.

Using a punch as the upper blade (first blade) and a die as the lower blade (second blade), a portion of the steel plate was sheared while maintaining the distance between the punch and the die at 10% of the plate thickness to obtain a processed material. After shearing, the tensile residual stress was measured for each of the shear end surface on the steel plate side (first shear end surface 1, see Figure 1) and the shear end surface on the processed material side (second shear end surface 2, see Figure 1).

The tensile residual stress was measured as follows. Figure 17 shows the method for measuring the tensile residual stress. As shown in Figure 17, residual stress was measured by X-rays with a spot diameter of φ500 μm at the center position in the thickness direction (three different locations in the width direction). The measurement directions of the residual stress were the thickness direction, the width direction, and the 45 degree direction from the thickness direction, and the sin ² ψ method was used to calculate the residual stress. The residual stress in the normal direction of the end face was assumed to be zero, and the maximum principal stress was calculated from the residual stress in the three directions. The values of the maximum principal stress calculated at the three locations were averaged.

1. First embodiment 1.1 Example 1
At the time when a crack was generated in the steel plate (plate thickness: 1.6 mm) by the punch and die, the inclination angle α of the steel plate was set to 4.0° and the inclination angle β was set to 4.5°. The inclination angle α and the inclination angle β were adjusted by providing a gap of 0.5 times the plate thickness between the plate holder (holding member) and the lower blade (die) when the steel plate was sheared, as shown in Figure 9. The measurement results of the tensile residual stress are shown in Table 1 below.

1.2 Example 2
At the time when a crack was generated in the steel plate (plate thickness: 1.6 mm) by the punch and die, the inclination angle α of the steel plate was set to 5.0° and the inclination angle β was set to 3.5°. The inclination angle α and the inclination angle β were adjusted by providing a gap of 1.0 times the plate thickness between the plate holder (holding member) and the lower blade (die) when the steel plate was sheared, as shown in Figure 9. The measurement results of the tensile residual stress are shown in Table 1 below.

1.3 Comparative Example 1
At the time when a crack was generated in the steel plate (plate thickness: 1.6 mm) by the punch and die, the inclination angle α of the steel plate was set to 0°, and the inclination angle β was set to 5.5°. The inclination angle α and the inclination angle β were adjusted so that the shape shown in FIG. 4(A) was obtained when the steel plate was sheared using a tool (punch, die, and pressing member) as shown in FIG. 8. That is, when the steel plate was sheared by the punch while pressing the steel plate with the die and pressing member, the inclination angle β naturally became 5.5°. It was also confirmed that when the steel plate had the same thickness, the inclination angle β was substantially the same regardless of the strength of the steel plate. Table 1 below shows the measurement results of the tensile residual stress.

1.4 Reference Example At the time when a crack was generated in a steel plate (plate thickness: 1.6 mm) by the punch and die, the inclination angle α of the steel plate was set to 0°, and the inclination angle β was set to 0°. The inclination angle α and the inclination angle β were adjusted so that when the steel plate was sheared, a shape as shown in Fig. 4(B) was obtained by installing a reverse plate holder at a position where the upper blade (punch) and the steel plate were sandwiched in addition to the tools (punch, die, and pressing member) as shown in Fig. 8. Table 1 below shows the measurement results of the tensile residual stress.

2. Second embodiment 2.1 Example 3
At the time when a crack was generated in the steel plate (plate thickness: 1.6 mm) by the punch and die, the inclination angle α of the steel plate was set to 1.5° and the inclination angle β was set to 4.5°. The inclination angle α and the inclination angle β were adjusted by providing a step of 0.1 mm in height at a position 10 mm from the tip of the lower blade (die) when the steel plate was sheared, as shown in Figure 12(B) or Figure 13(B). The measurement results of the tensile residual stress are shown in Table 2 below.

2.2 Example 4
At the time when a crack was generated in the steel plate (plate thickness: 1.6 mm) by the punch and die, the inclination angle α of the steel plate was set to 2.2° and the inclination angle β was set to 4.3°. The inclination angle α and the inclination angle β were adjusted by providing a step of 0.2 mm in height at a position 10 mm from the tip of the lower blade (die) when the steel plate was sheared, as shown in Figure 12(B) or Figure 13(B). The measurement results of the tensile residual stress are shown in Table 2 below.

2.3 Example 5
At the time when a crack was generated in the steel plate (plate thickness: 1.6 mm) by the punch and die, the inclination angle α of the steel plate was set to 4.5° and the inclination angle β was set to 4.0°. The inclination angle α and the inclination angle β were adjusted by providing a step of 0.5 mm in height at a position 10 mm from the tip of the lower blade (die) when the steel plate was sheared, as shown in Figure 12 (B) or Figure 13 (B). The measurement results of the tensile residual stress are shown in Table 2 below.

2.4 Example 6
At the time when a crack was generated in the steel plate (plate thickness: 1.6 mm) by the punch and die, the inclination angle α of the steel plate was set to 9.0° and the inclination angle β was set to 2.5°. The inclination angle α and the inclination angle β were adjusted by providing a step of 2.0 mm in height at a position 20 mm from the tip of the lower blade (die) when the steel plate was sheared, as shown in Figure 12 (B) or Figure 13 (B). The measurement results of the tensile residual stress are shown in Table 2 below.

2.5 Example 7
At the time when a crack was generated in the steel plate (plate thickness: 1.6 mm) by the punch and die, the inclination angle α of the steel plate was set to 7.0° and the inclination angle β was set to 3.0°. The inclination angle α and the inclination angle β were adjusted by providing a step of 2.0 mm in height at a position 30 mm from the tip of the lower blade (die) when the steel plate was sheared, as shown in Figure 12 (B) or Figure 13 (B). The measurement results of the tensile residual stress are shown in Table 2 below.

2.6 Comparative Example 2
At the time when a crack was generated in the steel plate (plate thickness: 1.6 mm) by the punch and die, the inclination angle α of the steel plate was set to 14.0° and the inclination angle β was set to 2.0°. The inclination angle α and the inclination angle β were adjusted by providing a step of 2.0 mm in height at a position 10 mm from the tip of the lower blade (die) when the steel plate was sheared, as shown in Figure 12 (B) or Figure 13 (B). The measurement results of the tensile residual stress are shown in Table 2 below.

3. Third embodiment 3.1 Example 8
At the time when a crack was generated in the steel plate (plate thickness: 1.6 mm) by the punch and die, the inclination angle α of the steel plate was set to 1.0° and the inclination angle β was set to 5.0°. The inclination angle α and the inclination angle β were adjusted by providing a step of 2.0 mm in height at a position 20 mm from the tip of the plate holder (holding member) as shown in Figure 12 (A) or Figure 13 (A) when the steel plate was sheared. The measurement results of the tensile residual stress are shown in Table 3 below.

3.2 Example 9
At the time when a crack was generated in the steel plate (plate thickness: 1.6 mm) by the punch and die, the inclination angle α of the steel plate was set to 6.0° and the inclination angle β was set to 3.0°. The inclination angle α and the inclination angle β were adjusted by providing a step of 2.0 mm in height at a position 40 mm from the tip of the plate holder (holding member) as shown in Figure 12 (A) or Figure 13 (A) when the steel plate was sheared. The measurement results of the tensile residual stress are shown in Table 3 below.

4. Fourth embodiment 4.1 Example 10
At the time when a crack was generated in the steel plate (plate thickness: 0.8 mm) by the punch and die, the inclination angle α of the steel plate was set to 2.5° and the inclination angle β was set to 8.0°. The inclination angle α and the inclination angle β were adjusted by providing a step of 0.1 mm in height at a position 10 mm from the tip of the lower blade (die) when the steel plate was sheared, as shown in Figure 12 (B) or Figure 13 (B). The measurement results of the tensile residual stress are shown in Table 4 below.

4.2 Example 11
At the time when a crack was generated in the steel plate (plate thickness: 0.8 mm) by the punch and die, the inclination angle α of the steel plate was set to 3.5° and the inclination angle β was set to 7.5°. The inclination angle α and the inclination angle β were adjusted by providing a step of 0.2 mm in height at a position 10 mm from the tip of the lower blade (die) when the steel plate was sheared, as shown in Figure 12 (B) or Figure 13 (B). The measurement results of the tensile residual stress are shown in Table 4 below.

4.3 Example 12
At the time when a crack was generated in the steel plate (plate thickness: 0.8 mm) by the punch and die, the inclination angle α of the steel plate was set to 7.5° and the inclination angle β was set to 6.5°. The inclination angle α and the inclination angle β were adjusted by providing a step of 0.5 mm in height at a position 10 mm from the tip of the lower blade (die) when the steel plate was sheared, as shown in Figure 12 (B) or Figure 13 (B). The measurement results of the tensile residual stress are shown in Table 4 below.

4.4 Example 13
At the time when a crack was generated in the steel plate (plate thickness: 0.8 mm) by the punch and die, the inclination angle α of the steel plate was set to 15.0° and the inclination angle β was set to 4.0°. The inclination angle α and the inclination angle β were adjusted by providing a step of 2.0 mm in height at a position 20 mm from the tip of the lower blade (die) when the steel plate was sheared, as shown in Figure 12 (B) or Figure 13 (B). The measurement results of the tensile residual stress are shown in Table 4 below.

4.5 Example 14
At the time when a crack was generated in the steel plate (plate thickness: 0.8 mm) by the punch and die, the inclination angle α of the steel plate was set to 11.5° and the inclination angle β was set to 5.0°. The inclination angle α and the inclination angle β were adjusted by providing a step of 2.0 mm in height at a position 30 mm from the tip of the lower blade (die) when the steel plate was sheared, as shown in Figure 12 (B) or Figure 13 (B). The measurement results of the tensile residual stress are shown in Table 4 below.

4.6 Comparative Example 3
At the time when a crack was generated in the steel plate (plate thickness: 0.8 mm) by the punch and die, the inclination angle α of the steel plate was set to 0°, and the inclination angle β was set to 9.0°. The inclination angle α and the inclination angle β were adjusted so that when the steel plate was sheared, a form as shown in FIG. 4(A) was obtained using a tool (punch, die, and pressing member) as shown in FIG. 8. In other words, when the steel plate was sheared by the punch while being pressed by the die and pressing member, the inclination angle β naturally became 9.0°. Table 4 below shows the measurement results of the tensile residual stress.

4.7 Comparative Example 4
At the time when a crack was generated in the steel plate (plate thickness: 0.8 mm) by the punch and die, the inclination angle α of the steel plate was set to 23.0° and the inclination angle β was set to 3.5°. The inclination angle α and the inclination angle β were adjusted by providing a step of 2.0 mm in height at a position 10 mm from the tip of the lower blade (die) when the steel plate was sheared, as shown in Figure 12 (B) or Figure 13 (B). The measurement results of the tensile residual stress are shown in Table 4 below.

The results shown in Tables 1 to 4 reveal the following:
(I) From the results of the reference examples shown in Tables 1 to 3, when the steel sheet is sheared, the steel sheet is pressed against the die using a sheet presser and against the punch using a reverse sheet presser, so that the inclination angle β is not generated with respect to the steel sheet, and thus the variation in the tensile residual stress can be suppressed between the first sheared end face and the second sheared end face. This is considered to be because, as shown in Fig. 4(B), when the steel sheet is sheared, the cracks grow equally from both the punch side and the die side.
(II) From a comparison between Examples 1 to 9 and Comparative Example 1 shown in Tables 1 to 3, the following can be said about the shearing of a 1.6 mm thick steel plate: In other words, when the steel plate is inclined (when the inclination angle α is greater than 0°) during shearing, the inclination angle β becomes smaller than when the steel plate is not inclined, and the variation between the tensile residual stress at the first shearing end face and the tensile residual stress at the second shearing end face is suppressed.
(III) From a comparison between Examples 10 to 14 and Comparative Example 3 shown in Table 4, the following can be said about the shearing of a 0.8 mm thick steel plate. That is, when the steel plate is inclined (when the inclination angle α is greater than 0°) during shearing, the inclination angle β becomes smaller than when the steel plate is not inclined, and the variation between the tensile residual stress at the first shear end face and the tensile residual stress at the second shear end face is suppressed.
(IV) From a comparison between Examples 1 to 9 and Comparative Examples 1 and 2 shown in Tables 1 to 3, the following can be said about the shearing of a 1.6 mm thick steel plate. That is, when the steel plate is sheared, if the inclination angle α of the steel plate becomes 14° or more, the inclination angle β can be reduced, but the variation between the tensile residual stress at the first shearing end face and the tensile residual stress at the second shearing end face becomes larger.
(V) From a comparison of Examples 10 to 14 and Comparative Examples 3 and 4 shown in Table 4, the following can be said about the shearing of a 0.8 mm thick steel plate. That is, when the inclination angle α of the steel plate is increased to 23° or more during shearing of the steel plate, the inclination angle β can be reduced, but the variation between the tensile residual stress at the first shearing end face and the tensile residual stress at the second shearing end face becomes larger.
(VI) The following can be said from a comparison of Examples 1 to 9 and Comparative Examples 1 and 2 shown in Tables 1 to 3 with Examples 10 to 14 and Comparative Examples 3 and 4 shown in Table 4. As described above, when the steel plate is sheared, if the inclination angle α of the steel plate is too large, the inclination angle β can be reduced, but the variation between the tensile residual stress of the first sheared end face and the tensile residual stress of the second sheared end face becomes larger. The upper limit of the inclination angle α that can suppress such variation varies depending on the thickness of the steel plate. Specifically, when the steel plate is thick, the upper limit of α becomes smaller, and when the steel plate is thin, the upper limit of α becomes larger. As described later, the upper limit of the inclination angle α can be expressed as a function of the thickness T of the steel plate.
(VII) From a comparison between Comparative Example 1 shown in Tables 1 to 3 and Comparative Example 3 shown in Table 4, the following can be said. That is, when the steel sheet on the die is pressed by the sheet presser and the inclination angle α is set to 0°, and the steel sheet is sheared by the punch, the thinner the sheet thickness of the steel sheet is, the larger the inclination angle β becomes. In other words, the upper limit value of the inclination angle β can also change depending on the sheet thickness of the steel sheet. As described later, the upper limit value of the inclination angle β can be expressed as a function of the sheet thickness T of the steel sheet.

In relation to the above findings (VI) and (VII), the present inventor confirmed the relationship between the inclination angle α and the inclination angle β during shearing of steel plates of various thicknesses and the tensile residual stress generated at the sheared end face. As a result, it was found that the upper limit values of the inclination angle α and the inclination angle β can be arranged as a function of the plate thickness T of the steel plate. Specifically, it was found that when the inclination angle α of the steel plate satisfies the relationship of the following formula (1) and the inclination angle β satisfies the relationship of the following formula (2) during shearing of the steel plate, the variation in the tensile residual stress between the first sheared end face and the second sheared end face can be suppressed.
0°<α≦13.0°/T ^0.7 ... (1)
0°≦β≦7.5°/T ^0.7 ... (2)
For example, when the thickness of the steel plate is 0.8 mm, the upper limit of the inclination angle α is 13.0°÷0.8 ^° =15.2°, and the upper limit of the inclination angle β is 7.5°÷0.8 ^° =8.8°. When the thickness of the steel plate is 1.6 mm, the upper limit of the inclination angle α is 13.0°÷1.6 ^° =9.4°, and the upper limit of the inclination angle β is 7.5°÷1.6 ^° =5.4°.

The processed materials produced by the method disclosed herein can be used, for example, as components for automobiles, home appliances, building structures, ships, bridges, construction machinery, various plants, penstocks, etc.

1 First shear end surface 1a Sagging 1b Fracture surface 1bx First fracture portion 1by Second fracture portion 1c Burr 1dx First crack 1dy Second crack 1e Shear surface 2 Second shear end surface 2a Sagging 2b Fracture surface 2c Burr 10 Workpiece 5 Steel plate 10a First surface 10b Second surface 11 Part of steel plate (first portion)
12 Other part of steel plate (second part)
21 First blade 21a First bottom surface 21b First side surface 21x First tip portion 22 Second blade 22a Second bottom surface 22b Second side surface 22x Second tip portion 25 Step 31 Pressing member 31a Pressing surface 35 Step 41 Support mechanism 51 Spacer 52 Spacer

Claims (4)

A method for producing a processed material by shearing a steel plate, comprising the steps of:
disposing the steel plate between a first blade and a second blade and between a pressing member and the second blade, wherein the steel plate has a first surface and a second surface opposite to the first surface, the first surface being disposed on the first blade side and the second surface being disposed on the second blade side, and the pressing member has a pressing surface facing the first surface;
shearing the steel plate by moving the first blade and the second blade relatively;
Including,
The pressing member has a recessed step at its tip, so that at the time when a crack is generated in the steel plate by the first blade and the second blade, the plate thickness T (mm) of the steel plate and the inclination angle α of the steel plate satisfy the relationship of the following formula (1), and the plate thickness T (mm) of the steel plate and the inclination angle β of the steel plate satisfy the relationship of the following formula (2).
Manufacturing method of processed materials.
0°<α≦13.0°/T ^0.7 ... (1)
0°≦β≦7.5°/T ^0.7 ... (2) A method for producing a processed material by shearing a steel plate, comprising the steps of:
disposing the steel plate between the first blade and the second blade and between a pressing member and the second blade, wherein the steel plate has a first surface and a second surface opposite to the first surface, the first surface being disposed on the first blade side and the second surface being disposed on the second blade side, and the pressing member has a pressing surface facing the first surface;
A spacer is disposed at least one of between the pressing member and the steel plate and between the steel plate and the second blade; and
shearing the steel plate by moving the first blade and the second blade relatively;
Including,
By shearing the steel plate with the spacer disposed at least either between the pressing member and the steel plate or between the steel plate and the second blade, at the time when a crack is generated in the steel plate by the first blade and the second blade, the plate thickness T (mm) of the steel plate and the inclination angle α of the steel plate satisfy the relationship of the following formula (1), and the plate thickness T (mm) of the steel plate and the inclination angle β of the steel plate satisfy the relationship of the following formula (2).
Manufacturing method of processed materials.
0°<α≦13.0°/T ^0.7 ... (1)
0°≦β≦7.5°/T ^0.7 ... (2) The tensile strength of the steel plate is 980 MPa or more;
The method according to claim 1 or 2 . The tensile strength of the steel plate is 1470 MPa or more.
The method according to claim 3 .