Shearing device and shearing method

Abstract

To prevent a large tensile residual stress from being generated on the end face of the steel sheet remaining on the die, and to suppress deterioration of fatigue characteristics and hydrogen embrittlement resistance.SOLUTION: A shearing device 10 comprises a die 20, a punch 30, a moving device 40, and a holder 50, where a first ridge line portion 26 being a cutting edge, includes a first tilted surface 26B1 and a first curved surface 26B2, a second ridge line portion 36 being a cutting edge forming a shear angle α between the first ridge line portion 26 and itself, includes a second tilted surface 36B1 and a second curved surface 36B2, and a total tilt angle difference ΔCT satisfies (0.15×α2+0.05×α+1)<ΔCT≤40 where the total tilt angle difference ΔCT is a sum of a first tilt angle difference ΔCA [degree] obtained by subtracting a tilt angle C2 of the second tilt surface 36B1 from a tilt angle C1 of the first tilted surface 26B1, and a second tilt angle difference ΔCB calculated from a curvature radius difference ΔR obtained by subtracting a curvature radius R2 of the second curved surface 36B2 from a curvature radius R1 of the first curved surface 26B2.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present disclosure relates to a shearing device and a shearing method.

Background Art

[0002] Conventionally, it has been known that the characteristics of a steel sheet as a workpiece cut by shearing are impaired due to work hardening, surface roughness, large tensile residual stress, etc. occurring on the end face of the steel sheet. As a technique for reducing the influence on the characteristics of the steel sheet, for example, in Patent Document 1, during shearing until a fracture surface occurs in the steel sheet of the workpiece, according to the deformation in the thickness direction of the workpiece, a clearance between the upper blade and the lower blade is increased. A shearing device is disclosed. According to Patent Document 1, it is said that the influence of work hardening on the end face of the member after fracture can be reduced.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] In general shearing, inside the steel sheet, large strain occurs at the portion in contact with the cutting edge of the die, and as a result, cracks are likely to progress from the surface on the die side of the steel sheet. Further, when cracks progress from the surface on the die side of the steel sheet, after shearing, a large tensile residual stress is generated on the end face of the steel sheet remaining on the die, and the fatigue characteristics and the hydrogen embrittlement resistance characteristics deteriorate. In particular, the deterioration of the hydrogen embrittlement resistance characteristics is likely to occur in high-strength steel sheets of 980 MPa or more.

[0005] By the way, for the purpose of reducing the maximum value of the load required for processing in shearing, a method of cutting a workpiece with a shear angle provided between the cutting edge of the die and the cutting edge of the punch is known. However, it has been found that the probability of cracks progressing from the surface on the die side of the steel sheet increases as the applied shear angle increases.

[0006] In both the state where no shear angle is imparted and the state where a shear angle is imparted, when a decrease in fatigue characteristics and hydrogen embrittlement resistance occurs on the scrap side among the steel sheets cut into products and scraps by shearing, the problem is small. On the other hand, when a decrease in fatigue characteristics and hydrogen embrittlement resistance occurs on the product side, there is concern about defects in the product. For this reason, when the inventors subject a steel sheet to shearing and obtain the steel sheet remaining on the die as a product, suppressing the progress of cracks from the surface of the steel sheet on the die side and shortening or making zero the progress distance of cracks from the die side is effective for preventing a decrease in fatigue characteristics and hydrogen embrittlement resistance.

Problems to be Solved by the Invention

[0007] In view of the above problems, the present disclosure aims to provide a shearing device capable of preventing a large tensile residual stress from occurring on the end face of the steel sheet remaining on the die and suppressing a decrease in fatigue characteristics and hydrogen embrittlement resistance, and a shearing method using this shearing device.

Means for Solving the Problems

[0008] The shearing device according to the first aspect of the present disclosure includes a die having a first surface that contacts one surface of a steel plate and a second surface that is continuous with the first surface via a first ridge line portion serving as a cutting edge, a punch having a third surface that contacts the other surface of the steel plate and a fourth surface that is continuous with the third surface via a second ridge line portion that forms a shear angle α with the first ridge line portion, a holder that sandwiches the steel plate between the first surface of the die, and a moving device that relatively moves the die or the punch along the thickness direction of the steel plate between a position where the fourth surface of the punch faces the holder and a position where the fourth surface faces the second surface of the die. The first ridge line portion includes at least one of a first inclined surface and a first curved surface inclined with respect to the first surface, the second ridge line portion includes at least one of a second inclined surface and a second curved surface inclined with respect to the third surface, and when viewed from a direction orthogonal to both the direction of relative movement and the direction in which the fourth surface faces the holder, the first inclination angle difference ΔCA [degrees], which is the smaller angle formed by the first inclined surface and the first surface, minus the inclination angle [degrees], which is the smaller angle formed by the second inclined surface and the third surface, and the radius of curvature difference ΔR [mm], which is the radius of curvature [mm] of the first curved surface minus the radius of curvature [mm] of the second curved surface, ΔCB [degrees] = 80 × ΔR is used in the formula to calculate the second inclination angle difference ΔCB. When the sum of the first inclination angle difference ΔCA and the second inclination angle difference ΔCB is defined as the total inclination angle difference ΔCT, the total inclination angle difference ΔCT is (0.15 × α 2 + 0.05 × α + 1) < ΔCT ≦ 40 is satisfied.

[0009] In the first aspect, the total inclination angle difference ΔCT, which is the sum of the first inclination angle difference ΔCA and the second inclination angle difference ΔCB, is (0.15 × α 2 + 0.05 × α + 1) < ΔCT ≦ 40 The shapes of the first ridge line portion and the second ridge line portion are configured to satisfy the above conditions. When the steel plate is cut with a tool (shearing device) such as in the first aspect, during shearing, the biting of the die-side blade into the steel plate can be suppressed. And, it is possible to promote the progress of cracks from the surface of the steel plate on the punch side, suppress the progress of cracks from the surface of the steel plate on the die side, and shorten or make zero the progress distance of cracks from the die side.

[0010] The shearing device according to the second aspect of the present disclosure includes the step of preparing the shearing device of the first aspect, the step of placing a steel plate on the first surface of the die of the prepared shearing device, the step of supporting the placed steel plate with a holder, and the step of using a moving device to relatively move the die or the punch along the thickness direction of the steel plate so that the first ridge line portion and the second ridge line portion are close to each other to cut the steel plate.

[0011] In the second aspect, since the steel plate is sheared using the shearing device of the first aspect, during shearing, the progress of cracks from the surface of the steel plate on the punch side is promoted, and the progress of cracks from the surface of the steel plate on the die side is suppressed. And, it is possible to shorten or make zero the progress distance of cracks from the die side.

Advantages of the Invention

[0012] According to the present disclosure, it is possible to prevent a large tensile residual stress from occurring on the end face of the steel plate remaining on the die, and it is possible to provide a shearing device capable of suppressing a decrease in fatigue characteristics and hydrogen embrittlement resistance characteristics. Further, according to the shearing method using this shearing device, it is possible to prevent a large tensile residual stress from occurring on the end face of the steel plate remaining on the die, and suppress a decrease in fatigue characteristics and hydrogen embrittlement resistance characteristics.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0014] The first to third embodiments will be described below. In the following description of the drawings, the same parts and similar parts are denoted by the same reference numerals or similar reference numerals. However, the relationship between the thickness and the planar dimensions in the drawings, the ratio of the thicknesses of each device and each member, etc. are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined with reference to the following description. Also, there are parts where the dimensional relationships and ratios are different between the drawings.

[0015] - First Embodiment - <Structure of Shearing Machine>[[ / END]] First, the shearing machine 10 according to the first embodiment will be described with reference to FIGS. 1 to 7. As shown in FIG. 1, the shearing machine 10 is, for example, a crop shear that is arranged in a hot rolling line of a steel mill or the like and cuts the end of a steel plate 12 as a workpiece. The shearing machine 10 includes a die 20, a punch 30, a moving device 40, and a holder 50 (see FIG. 3).

[0016] The die 20 is the lower blade of the shearing machine 10 and has a first surface 22 that contacts one surface (the lower surface in FIG. 3) of the steel plate 12, a second surface 24, and a first ridge line portion 26 located between the first surface 22 and the second surface 24. The first surface 22 is substantially horizontal. The second surface 24 is substantially vertical and is continuous with the first surface 22 via the first ridge line portion 26. The first ridge line portion 26 extends linearly along the shearing direction X (the left - right direction in FIG. 1) of the steel plate 12. All regions from end to end of the first ridge line portion 26 function as cutting edges.[[ / END]]

[0017] The punch 30 is the upper blade of the shearing machine 10 and has a third surface 32 that contacts the other surface (the upper surface in FIG. 3) of the steel plate 12, a fourth surface 34, and a second ridge line portion 36 located between the third surface 32 and the fourth surface 34. The third surface 32 is substantially horizontal. The fourth surface 34 is substantially vertical and is continuous with the third surface 32 via the second ridge line portion 36. The second ridge line portion 36 extends linearly along the shearing direction X of the steel plate 12, similar to the first ridge line portion 26. All regions from end to end of the second ridge line portion 36 function as cutting edges.[[ / END]]

[0018] The moving device 40 is provided above the punch 30 and can be realized by, for example, an electric motor or a hydraulic mechanism. Although not shown in the drawings, the moving device 40 is provided with a driving device, a speed control device, and the like. The moving device 40 moves the second ridge line portion 36 of the punch 30 along the thickness direction of the steel plate 12 between a position where the fourth surface 34 of the punch 30 faces the holder 50 and a position where the fourth surface 34 faces the second surface 24 of the die 20, toward the first ridge line portion 26 side of the die 20. That is, the die 20 and the punch 30 move relative to each other by the moving device 40. The first ridge line portion 26 and the second ridge line portion 36 can be close to and separated from each other. In the first embodiment, the thickness direction of the steel plate 12 is defined as the "direction Y of relative movement".

[0019] In the present disclosure, it is only necessary that the first ridge line portion 26 and the second ridge line portion 36 move relative to each other so as to be close to each other, and the direction Y of relative movement is not limited to the case where the punch 30 is pushed out toward the die 20. The moving device 40 may be provided on the die 20 side, and the die 20 may be pushed out toward the punch 30, or the moving device 40 may be provided on both the die 20 side and the punch 30 side.

[0020] As shown in FIG. 2, the die 20 and the punch 30 are arranged relative to each other such that a certain shear angle α is formed between the first ridge line portion 26 of the die 20 and the second ridge line portion 36 of the punch 30. By performing the shearing process in a state where the shear angle α is imparted, the maximum value of the load required for the process is reduced, and the burden on the shearing device 10 is reduced. Further, as the second ridge line portion 36 descends along the direction Y of relative movement, the contact position (shearing position) between the second ridge line portion 36 and the steel plate 12 moves to the right in FIGS. 1 and 2 along the shearing direction X.

[0021] The method of the present disclosure can achieve the effect regardless of the shear angle α. In the present disclosure, the shear angle α is preferably 0.5 degrees or more and 10 degrees or less (0.5 degrees ≤ α ≤ 10 degrees). When the shear angle α is less than 0.5 degrees, the shear angle is too small, and cutting may be difficult due to the load limitation of the press machine (shearing device). Further, when the shear angle α exceeds 10 degrees, the characteristics of the end face, such as post-processability, deteriorate.

[0022] Further, when the range of the shear angle α is 1 degree or more and 5 degrees or less, the load can be effectively reduced and the characteristics of the end face can be maintained, which is more preferable (1 degree ≤ α ≤ 5 degrees). In the first embodiment, the shear angle α is set to about 3 degrees.

[0023] The holder 50 is provided above the die 20 and sandwiches and supports the steel plate 12 between it and the first surface 22 of the die 20 (see FIG. 3). Note that the holder 50 is not essential in the present disclosure. As shown in FIG. 3, the die 20 and the punch 30 are arranged along the direction Z (the left-right direction in FIG. 3) in which the fourth surface 34 and the holder 50 face each other, with a certain clearance therebetween.

[0024] In the present disclosure, the clearance is preferably 5% or more and 25% or less of the thickness of the steel plate 12. When the clearance is less than 5%, the clearance becomes too narrow, and a secondary shear surface is generated on the end face of the steel plate 12 after shearing, so there is a concern that the ductility may decrease. Further, when the clearance exceeds 25%, the clearance becomes too wide, and relatively large burrs are formed on the end face by shearing, increasing the burden of removing the burrs in subsequent processes. Also, in order to stably ensure high ductility of the end face and reduce the probability of burr generation, the clearance is preferably controlled within the range of 10% or more and 20% or less of the thickness of the steel plate 12.

[0025] (The first ridge line portion and the second ridge line portion) Next, the first ridge line portion 26 of the die 20 and the second ridge line portion 36 of the punch 30 will be specifically described. As shown in FIG. 3, the first ridge line portion 26 is composed of a first inclined surface inclined with respect to the first surface 22, and the second ridge line portion 36 is composed of a second inclined surface inclined with respect to the third surface 32.

[0026] FIG. 3 is a cross-sectional view seen from a direction orthogonal to both the relative movement direction Y and the direction Z in which the fourth surface 34 and the holder 50 face each other, that is, a cross-sectional view seen along the shearing direction X. In the first embodiment, the entire first ridge line portion 26 forms the first inclined surface, and the entire second ridge line portion 36 forms the second inclined surface. The width W of the region of the first inclined surface and the width W of the region of the second inclined surface are equal. Also, the first surface 22 and the third surface 32 are parallel to the direction Z in which the fourth surface 34 and the holder 50 face each other.

[0027] Here, in the present disclosure, the first ridge line portion includes at least one of a first inclined surface inclined with respect to the first surface and a first curved surface (see the first curved surface 26B2 in FIG. 10), and the second ridge line portion includes at least one of a second inclined surface inclined with respect to the third surface and a second curved surface (see 36B2 in FIG. 10). Then, when viewed along the shearing direction X, the inclination angle [degrees] of the second inclined surface with respect to the third surface is subtracted from the inclination angle [degrees] of the first inclined surface with respect to the first surface, which is the smaller angle, to calculate the first inclination angle difference ΔCA [degrees].

[0028] Then, the radius of curvature difference ΔR [mm] is calculated by subtracting the radius of curvature [mm] of the second curved surface from the radius of curvature [mm] of the first curved surface. And the radius of curvature difference ΔR is ΔCB [degrees]=80×ΔR ··· Equation (1) is used in the formula to calculate the second inclination angle difference ΔCB.

[0029] Equation (1) is a conversion formula introduced to treat the difference in the radius of curvature of the curved surface as an amount equivalent to the difference in the tilt angle. For example, when the difference in the radius of curvature ΔR is 0.1 mm, the second tilt angle difference ΔCB is 8 degrees according to Equation (1). Equation (1) is set in consideration of the result of measuring the tensile residual stress on the end face of the product 12A obtained by the shearing process using the shearing apparatus with X-rays. Also, the shearing process is carried out by changing the shear angle α, the first tilt angle difference ΔCA, and the second tilt angle difference ΔCB of the shearing apparatus in a plurality of patterns.

[0030] Here, it is desirable that the difference in the radius of curvature ΔR is uniform along the direction in which the cutting edge extends (the shearing direction X in FIG. 1). When the difference in the radius of curvature ΔR is non-uniform along the shearing direction X in FIG. 1, for example, when there is a partial depression formed on the cutting edge, the roughness of the fracture surface increases, and the fatigue characteristics and the hydrogen embrittlement resistance characteristics deteriorate. In the present disclosure, it is preferable that the variation width of the difference in the radius of curvature ΔR in the range of 1 mm along the shearing direction X in FIG. 1 is 20% or less of the average value of the difference in the radius of curvature ΔR over the entire shearing direction X, in terms of effectively suppressing the roughness of the fracture surface and the deterioration of the fatigue characteristics and the hydrogen embrittlement resistance characteristics. However, the present disclosure holds even when the difference in the radius of curvature ΔR is non-uniform along the shearing direction X in FIG. 1.

[0031] Also, in the present disclosure, when the difference in the radius of curvature ΔR of the cutting edge is non-uniform in the cross section, by defining an approximate circle, the difference in the radius of curvature ΔR for use in the calculation formula of the present disclosure can be calculated. Specifically, for example, in the cross section of FIG. 4, it is exemplified that a depression D is formed between the bottom surface BS and the side surface SS, and curved surfaces are formed above and below the depression D, respectively. Note that the bottom surface BS corresponds to the first and third surfaces of the present embodiment. Also, the side surface SS corresponds to the second and fourth surfaces of the present embodiment.

[0032] An intersection point of the contour of the curved surface SC1 above the depression D in FIG. 4 and the contour of the side surface SS above the curved surface SC1 is defined as "a". Also, an intersection point of the contour of the curved surface SC2 below the depression D in FIG. 4 and the contour of the bottom surface BS on the left side of the curved surface SC2 is defined as "b".

[0033] Next, an approximate ellipse P is defined that passes through intersection point a and intersection point b and has the smallest deviation from the cross-sectional profile of the cutting edge composed of the curved surface SC1 and the curved surface SC2. Specifically, among a plurality of approximate ellipses passing through intersection point a and intersection point b, the separation distance between the cross-sectional profile of the cutting edge along the respective normal directions at each point on the approximate ellipse is measured. Then, an approximate ellipse is defined in which the total sum of the separation distances in the section sandwiched between intersection point a and intersection point b is minimized. In FIG. 4, the defined approximate ellipse P is illustrated by a broken line.

[0034] Next, on the defined approximate ellipse P, a midpoint c that is equidistant from intersection point a and intersection point b is defined on the cross-sectional profile side of the curved surface SC1 and the curved surface SC2 (the lower right side in FIG. 4). Then, an approximate circle Q is defined that passes through the midpoint c and is closest to the bottom surface BS and the side surface SS in the cross-section. In FIG. 4, the defined approximate circle Q is illustrated by a dashed-dotted line. The radius of the defined approximate circle Q can be used as the curvature radius difference ΔR for use in the calculation formula of the present disclosure.

[0035] Then, the sum of the first inclination angle difference ΔCA and the second inclination angle difference ΔCB is defined as the total inclination angle difference ΔCT. The total inclination angle difference ΔCT satisfies (0.15×α 2 +0.05×α + 1) < ΔCT ≦ 40 ··· Equation (2) In the present disclosure, the total inclination angle difference ΔCT may be composed of only the first inclination angle difference ΔCA or may be composed of only the second inclination angle difference ΔCB. The first embodiment is a case where the first ridge line portion 26 includes only the first inclined surface and the second ridge line portion 36 includes only the second inclined surface. When the total inclination angle difference ΔCT exceeds 40, the burr formed on the cutting edge becomes too large. For this reason, in the present disclosure, the upper limit value of the total inclination angle difference ΔCT is set to 40.

[0036] In the first embodiment, the smaller angle formed by the first inclined surface and the first surface 22 is set as the inclination angle C1 [degrees]. Also, the smaller angle formed by the second inclined surface and the third surface 32 is set as the inclination angle C2 [degrees]. Then, the first inclination angle difference ΔCA [degrees] is calculated by subtracting the inclination angle C2 from the inclination angle C1 (ΔCA = C1 - C2). In the first embodiment, the first inclination angle difference ΔCA [degrees] is (0.15×α 2 +0.05×α + 1) < ΔCA ≤ 40 ··· Equation (3) The shape of the first ridge portion 26 and the shape of the second ridge portion 36 are configured so as to satisfy this. That is, in the first embodiment, the total inclination angle difference ΔCT is composed only of the first inclination angle difference ΔCA, and ΔCT = ΔCA. The above Equation (3) of the first embodiment is Equation (2) of the present disclosure.

[0037] The above Equation (2) means the conditions represented by the shaded area in FIG. 5. That is, in the shearing method using the shearing device 10 according to the first embodiment, the conditions of the shear angle α and the first inclination angle difference ΔCA included in the shaded area are used.

[0038] The solid line locus L1 in FIG. 5 is a part of the curve: ΔCA = 0.15×α 2 +0.05×α + 1. The curve: ΔCA is obtained by performing shearing with the conditions of the shear angle α and the first inclination angle difference ΔCA changed in a plurality of patterns and then measuring the tensile residual stress on the end face of the product of each steel plate 12 by X-ray. In addition, at the time of X-ray measurement, the spot diameter was 500 μm, and the tensile residual stress in the plate thickness direction was measured at the center position in the plate thickness direction.

[0039] Specifically, for example, as shown in Table 1 below, nine values of the shear angle α, namely 0 degrees, 1 degree, 2 degrees, 3 degrees, 4 degrees, 5 degrees, 6 degrees, 8 degrees, and 10 degrees, are set. And for each value of the shear angle α, five values of the first inclination angle difference ΔCA, namely 0 degrees, 10 degrees, 20 degrees, 30 degrees, and 40 degrees, are set. Then, in each of the patterns combining the shear angle α and the first inclination angle difference ΔCA, the tensile residual stress on the end face of the product of the steel plate 12 after shearing is measured. Also, the tensile residual stress in the case where the first inclination angle difference ΔCA = 0 degrees is set as the reference value for each of the nine shear angles α. And by comparing each of the tensile residual stresses measured when the first inclination angle difference ΔCA is 10 degrees, 20 degrees, 30 degrees, and 40 degrees with the respective reference values at the corresponding shear angles α, the end face of the product is evaluated, and Equation (3) can be derived according to the evaluation results.

[0040]

Table 1

[0041]

Table 2

[0042]

Table 3

[0043] Table 1 shows the evaluation results of the tensile residual stress of the obtained steel plate when shearing is carried out by changing the inclination angle difference of the cutting edge and the shear angle in the shearing device. Table 2 and Table 3 are both tables explaining the specific parameters of each of the 36 examples in Table 1. Specifically, Table 2 is an example in the case where the first inclination angle difference ΔCA is formed only by the value of the inclination angle C1. Also, Table 3 is an example in the case where the first inclination angle difference ΔCA is formed by the difference between the inclination angle C1 and the inclination angle C2.

[0044] In addition, in Tables 2 and 3, the notation with "-" attached to the values of the radius of curvature R1 and the radius of curvature R2 means that the cutting edge is intentionally not provided with a radius of curvature, that is, the cutting edge is a straight edge. Also, in Tables 2 and 3, the notation with "-" attached to the values of the chamfering angle C1 and the chamfering angle C2 means that chamfering is intentionally not provided, that is, the cutting edge is a straight edge.

[0045] In addition, the third "lower limit formula" from the right in the uppermost row of Tables 2 and 3 is the formula of (0.15×α2 + 0.05×α + 1) on the left side in the above formulas (2) and (3). Therefore, when the value of "ΔCT / lower limit formula" in the second column from the right in the uppermost row of Tables 2 and 3 exceeds 1, it means that the total inclination angle difference ΔCT satisfies the lower limit condition defined by the left side in the above formula (2).

[0046] In Table 1, "A" in the "Evaluation Result" on the far right means that the tensile residual stress has decreased by 20% or more compared to the reference value. Also, "B" means that the tensile residual stress has decreased by 10% or more and less than 20% compared to the reference value. Also, "C" means that the tensile residual stress has decreased by 5% or more and less than 10% compared to the reference value. Also, "D" means that the tensile residual stress has decreased by less than 5% compared to the reference value.

[0047] For example, when the shear angle α is 0 degrees, regardless of the magnitude of the first inclination angle difference ΔCA, in all the measured steel plates 12, the tensile residual stress has decreased by 10% or more. On the other hand, when the shear angle α is 10 degrees, it can be seen that the magnitude of the decreased tensile residual stress varies depending on the magnitude of the first inclination angle difference ΔCA. When the shear angle α is 10 degrees, the decreased tensile residual stress is greater when the first inclination angle difference ΔCA is 20 degrees than when the first inclination angle difference ΔCA is 10 degrees. Also, the decreased tensile residual stress is greater when the first inclination angle difference ΔCA is 40 degrees than when the first inclination angle difference ΔCA is 20 degrees.

[0048] In addition, when the shear angle α is between 3 degrees and 5 degrees, in all cases where the first inclination angle difference ΔCA is 10 degrees, 20 degrees, 30 degrees, and 40 degrees, it was found that the respective tensile residual stresses were reduced by 20% or more with respect to the reference value, obtaining an excellent effect. Also, even when the shear angle α is 6 degrees, when the first inclination angle difference ΔCA is 40 degrees, similarly, it was found that an excellent effect of reducing the tensile residual stress by 20% or more with respect to the reference value can be obtained. Further, as shown in Tables 2 and 3, it was found that the same effect can be obtained if the first inclination angle difference ΔCA between the inclination angle C1 and the inclination angle C2 is the same regardless of the presence or absence of the inclination angle C2.

[0049] In addition, the dashed trajectory L2 in FIG. 5 is part of the curve: ΔCA = (0.3×α 2 +0.1×α + 2). The curve of the trajectory L2 is also derived according to the measurement results of the tensile residual stress on the end face of the product of the steel plate 12, similar to the case of the trajectory L1. By performing the shearing process method so that the first inclination angle difference ΔCA satisfies (0.3×α 2 +0.1×α + 2) < ΔCA ≤ 40, the magnitude of each tensile residual stress on the end face of the product of the steel plate 12 can be further reduced.

[0050] According to the shear angle α during shearing, the shape of the first ridge portion 26 and the shape of the second ridge portion 36 are configured so that the first inclination angle difference ΔCA satisfies the formula (3). Therefore, during shearing, it becomes possible to promote the progress of cracks from the surface of the steel plate 12 on the punch 30 side. By promoting the progress of cracks from the surface of the steel plate 12 on the punch 30 side, the tensile residual stress on the end face of the steel plate 12 as a product remaining on the die 20 after shearing can be suppressed.

[0051] <Shearing process method> Next, the shearing method according to the first embodiment will be described. First, prepare the shearing device 10 described with reference to FIGS. 1 to 4. Next, as shown in FIG. 3, place the steel plate 12 on the first surface 22 of the die 20 of the prepared shearing device 10. As the steel plate 12, for example, a high-strength steel plate with a tensile strength of about 980 MPa or more can be adopted. In the first embodiment, as the workpiece, a steel plate 12 with a thickness of 1.6 mm and a tensile strength of 1180 MPa grade was used. The definition of the tensile strength of the steel plate 12 follows, for example, "ISO 6892-1:2009".

[0052] Next, support the placed steel plate 12 with the holder 50. Next, lower the punch 30 along the thickness direction of the steel plate 12 by the moving device 40 so that the first ridge line portion 26 and the second ridge line portion 36 are close to each other. In the first embodiment, the punching clearance between the die 20 and the punch 30 was set to a value of 10% of the plate thickness (clearance / plate thickness = 0.1). Also, the shear angle α was set to 5 degrees, and the first inclination angle difference ΔCA was set to 20 degrees. In the case of the first embodiment, as a result of observing the cross section of the end portion of the steel plate 12 during cutting, the generation and progress of cracks from the punch 30 side were confirmed.

[0053] Then, as shown in FIG. 6, when the punch 30 is further lowered along the thickness direction of the steel plate 12 by the moving device 40, the progress of cracks from the surface of the steel plate 12 on the punch 30 side is promoted. Then, the steel plate 12 is sheared by the advanced cracks and cut into the product 12A and the scrap 12B. By the above respective steps, the shearing method according to the first embodiment is realized.

[0054] In FIG. 7, the results of X-ray measurement (experiment) of the tensile residual stress measured along the direction Y (thickness direction) of relative movement at the respective end faces of the product 12A and the scrap 12B after shearing are illustrated. The conditions during the X-ray measurement are the same as those used for the evaluation results of the end faces described in Table 1.

[0055] As shown in FIG. 7, in the direction Y of relative movement, the tensile residual stress of the scrap 12B was about 1200 MPa, while the tensile residual stress of the product 12A was suppressed low at about 200 MPa.

[0056] <Comparative Example> On the other hand, as a comparative example, shearing was performed using a shearing device in which the shape of the first ridge line portion 26 and the shape of the second ridge line portion 36 were configured so that the first inclination angle difference ΔCA did not satisfy the formula (3). Specifically, for example, the inclination angle C1 = inclination angle C2 was set, and the shearing device according to the comparative example was configured so that the first inclination angle difference ΔCA = 0. In the shearing device according to the comparative example, for conditions other than the first inclination angle difference ΔCA, including the magnitude of the shear angle α, the same settings were made as in the case of the first embodiment.

[0057] In the case of the comparative example, as a result of observing the cross section of the end portion of the steel plate 12 during cutting, the generation of cracks from both sides of the punch and the die and the progress of the cracks were confirmed. Also, in the direction Y of relative movement, the tensile residual stress of the product 12A was about 700 MPa, which was about 3.5 times larger than the corresponding value of about 200 MPa in the case of the first embodiment.

[0058] (Function and Effect) In the shearing device 10 according to the first embodiment, the first inclination angle difference ΔCA is calculated by subtracting the inclination angle C2 of the second inclined surface in the second ridge line portion 36 of the punch 30 from the inclination angle C1 of the first inclined surface in the first ridge line portion 26 of the die 20. The calculated first inclination angle difference ΔCA satisfies (0.15×α 2 +0.05×α + 1) < ΔCA ≦ 40, and the shape of the first ridge line portion 26 and the shape of the second ridge line portion 36 are configured.

[0059] Therefore, during shearing, the biting of the blade on the die 20 side into the steel plate 12 can be suppressed. Further, the progress of cracks from the surface of the steel plate 12 on the punch 30 side is promoted, while the progress of cracks from the surface of the steel plate 12 on the die 20 side is suppressed, and the progress distance of cracks from the die 20 side can be shortened or made zero. Thus, even when the steel plate 12 is subjected to a shearing process with a shear angle provided, it is possible to prevent a large tensile residual stress from occurring in the end face of the steel plate 12 remaining on the die 20, and a shearing device 10 capable of suppressing a decrease in fatigue characteristics and hydrogen embrittlement resistance characteristics can be provided.

[0060] Further, according to the shearing method using the shearing device 10 according to the first embodiment, even in a state where the shear angle α is provided, it is possible to prevent a large tensile residual stress from occurring in the end face of the steel plate 12 remaining on the die 20, and to suppress a decrease in fatigue characteristics and hydrogen embrittlement resistance characteristics. In particular, since a decrease in hydrogen embrittlement resistance characteristics is likely to occur in high-strength steel plates having a tensile strength of about 980 MPa or more, the present embodiment is advantageous in shearing high-strength steel plates.

[0061] In addition, there is a method of eliminating work hardening of the end face and preventing the generation of tensile residual stress by performing additional shearing processes such as so-called shaving on the end face after the original shearing process. However, according to the first embodiment, since it is possible to prevent a large tensile residual stress from occurring in the end face of the steel plate 12 when the original shearing process is completed, an additional shearing operation is unnecessary. For this reason, the burden of the entire processing operation can be reduced.

[0062] Further, as a result of research by the present inventors, it has been found that the larger the tensile strength of the steel plate 12, the easier it is for cracks to progress from the surface on the die 20 side when cutting in a state where the shear angle α is provided. For this reason, the shearing device 10 according to the first embodiment is effective for high-strength steel plates having a large tensile strength. In particular, as a result of investigations by the present inventors, for high-strength steel plates having a tensile strength of about 980 MPa or more, the tensile residual stress has decreased significantly.

[0063] When cutting a high-strength steel sheet having a tensile strength of 980 MPa or more, in order to suppress the damage of the cutting edge that progresses with the number of cuts, it is desirable that the hardness of the material of the cutting edge as a tool is 58 Rockwell hardness (HRC) or more. Further, from the viewpoint of suppressing the damage of the cutting edge, it is desirable to apply a coating to the cutting edge separately from the setting of the hardness of the material, or together with the setting of the hardness of the material. When the coating is applied, in particular, it is more desirable that a PVD (Physical Vapor Deposition) coating is applied because it is easy to prevent deformation and transformation of the base metal material. Note that in the present disclosure, the steel sheet 12 is not limited to a high-strength steel sheet, and the present disclosure can be applied to the shearing of steel sheets with a wide range of strengths.

[0064] -Second Embodiment- <Structure of Shearing Device> Next, the shearing device 10A according to the second embodiment will be described with reference to FIGS. 8 and 9 and Table 4. As shown in FIG. 8, the shearing device 10A includes a die 20A, a punch 30A, a moving device 40, and a holder 50.

[0065] FIG. 8 is a cross-sectional view seen from a direction orthogonal to both the relative movement direction Y and the direction Z in which the fourth surface 34 and the holder 50 face each other, that is, a cross-sectional view seen along the shearing direction X (see FIG. 1). Here, in the first embodiment, the first ridge line portion 26 of the die 20 and the second ridge line portion 36 of the punch 30 each had an inclined surface. However, in the second embodiment, the difference from the first embodiment is that the first ridge line portion 26A of the die 20A and the second ridge line portion 36A of the punch 30A each have a curved surface.

[0066] Therefore, in the following description of the second embodiment, the first ridge line portion 26A and the second ridge line portion 36A will be mainly described. Further, regarding other configurations of the shearing device 10A according to the second embodiment other than the first ridge line portion 26A and the second ridge line portion 36A, since they are equivalent to the members with the same names in the shearing device 10 according to the first embodiment, duplicate descriptions will be omitted.

[0067] In the second embodiment, as shown in FIG. 8, the first ridge line portion 26A is formed of a first curved surface, and the second ridge line portion 36A is formed of a second curved surface. That is, in the second embodiment, the total inclination angle difference ΔCT in the formula (2) of the present disclosure is composed only of the second inclination angle difference ΔCB, and ΔCT = ΔCB. Here, the radius of curvature of the first curved surface is set as R1 [mm]. Also, the radius of curvature of the second curved surface is set as R2 [mm]. Then, the radius of curvature difference ΔR [mm] is calculated by subtracting the radius of curvature R2 from the radius of curvature R1 (ΔR = R1 - R2). In the second embodiment, the calculated radius of curvature difference ΔR [mm] is (0.001875×α 2 +0.000625×α+0.0125)<ΔR≦0.5 ··· Formula (4) The shape of the first ridge line portion 26A and the shape of the second ridge line portion 36A are configured so as to satisfy

[0068] Here, when formula (4) is multiplied by 80, (0.15×α 2 +0.05×α+1)<80×ΔR≦40 ··· Formula (5) is obtained. Then, from formula (1) and formula (5), the following formula (6) is obtained. (0.15×α 2 +0.05×α+1)<ΔCB≦40 ··· Formula (6) That is, the above formula (6) of the second embodiment is the formula (2) of the present disclosure.

[0069] Formula (4) means the condition represented by the shaded area in FIG. 9. That is, in the shearing method using the shearing device 10A according to the second embodiment, the conditions of the shear angle α and the radius of curvature difference ΔR included in the shaded area are used.

[0070] The solid line locus M1 in FIG. 9 is a curve: ΔR = 0.001875×α 2It is part of +0.000625×α + 0.0125. Curve: ΔR is obtained by measuring the tensile residual stress on the end face of each product of the steel plate 12 by X-ray after performing shearing processing while changing the conditions of the shear angle α and the radius of curvature difference ΔR into a plurality of patterns.

[0071] Specifically, for example, as shown in Table 4 below, nine values of 0 degrees, 1 degree, 2 degrees, 3 degrees, 4 degrees, 5 degrees, 6 degrees, 8 degrees, and 10 degrees are set for the shear angle α. Also, in the case of each value of the shear angle α, six values of 0 mm, 0.1 mm, 0.125 mm, 0.25 mm, 0.375 mm, and 0.5 mm are set for the radius of curvature difference ΔR. Then, for each pattern combining the shear angle α and the radius of curvature difference ΔR, the tensile residual stress on the end face of the product of the steel plate 12 after shearing processing is measured.

[0072] Also, the tensile residual stress in the case of the radius of curvature difference ΔR = 0 mm is set as the reference value for each of the nine shear angles α. Then, by comparing each of the tensile residual stresses measured in the cases where the radius of curvature difference ΔR is 0.1 mm, 0.125 mm, 0.25 mm, 0.375 mm, and 0.5 mm with the corresponding reference values for each shear angle α, the end face of the product is evaluated, and Equation (2) can be derived according to the evaluation result.

[0073]

Table 4

[0074]

Table 5

[0075]

Table 6

[0076] Table 4 shows the evaluation results of the tensile residual stress of the obtained steel plate when shearing is performed by changing the difference in the radius of curvature of the cutting edge and the shear angle in the shearing device. Tables 5 and 6 are both tables explaining the specific parameters of each of the 45 examples in Table 4. Specifically, Table 5 is an example in the case where the radius of curvature difference ΔR is formed only by the value of the radius of curvature R1. Table 6 is an example in the case where the radius of curvature difference ΔR is formed by the difference between the radius of curvature R1 and the radius of curvature R2.

[0077] Also, in Tables 5 and 6, the meanings of the notations with "-" attached as the values of the radius of curvature R1 and the radius of curvature R2, and the notations with "-" attached as the values of the inclination angle C1 and the inclination angle C2 are the same as those in Tables 2 and 3. Also, the meanings of "lower limit formula" and "ΔCT / lower limit formula" in Tables 5 and 6 are the same as those in Tables 2 and 3.

[0078] In Table 4, "Evaluation result" "A" on the far right means that the tensile residual stress has decreased by 20% or more with respect to the reference value, in the same manner as described in Table 1. Also, "B" means that the tensile residual stress has decreased by 10% or more and less than 20% with respect to the reference value. Also, "C" means that the tensile residual stress has decreased by 5% or more and less than 10% with respect to the reference value. Also, "D" means that the tensile residual stress has decreased by less than 5% with respect to the reference value.

[0079] For example, when the shear angle α is 0 degrees, regardless of the magnitude of the radius of curvature difference ΔR, in all the measured steel plates 12, the tensile residual stress has decreased by 10% or more. On the other hand, when the shear angle α is 10 degrees, it can be seen that the magnitude of the decreased tensile residual stress differs depending on the magnitude of the radius of curvature difference ΔR. If the shear angle α is 10 degrees, the decreased tensile residual stress was greater when the radius of curvature difference ΔR was 0.25 mm than when the radius of curvature differences ΔR were 0.1 mm and 0.125 mm. Also, when the radius of curvature difference ΔR was 0.5 mm, the decreased tensile residual stress was greater than when the radius of curvature difference ΔR was 0.375 mm.

[0080] Also, when the shear angle α is between 3 degrees and 5 degrees, in all cases where the radius of curvature difference ΔR is 0.1 mm, 0.125 mm, 0.25 mm, 0.375 mm, and 0.5 mm, it was found that the respective tensile residual stresses were reduced by 20% or more compared to the reference value, obtaining an excellent effect. Also, even when the shear angle α is 6 degrees and the radius of curvature difference ΔR is 0.5 mm, it was found that an excellent effect of the tensile residual stress being reduced by 20% or more compared to the reference value was obtained. Further, as shown in Tables 5 and 6, it was found that regardless of the presence or absence of the radius of curvature R2, the same effect can be obtained if the radius of curvature difference ΔR between the radius of curvature R1 and the radius of curvature R2 is the same.

[0081] Also, the dashed trajectory M2 in FIG. 9 is part of the curve: ΔR = 0.00375×α 2 +0.00125×α + 0.025. The curve of the trajectory M2 is also derived according to the measurement results of the tensile residual stress on the end face of the product of the steel plate 12, similar to the case of the trajectory M1. By performing the shearing process method so that the radius of curvature difference ΔR satisfies (0.00375×α 2 +0.00125×α + 0.025) < ΔR ≦ 0.5, the magnitude of each residual stress on the end face of the product of the steel plate 12 can be further reduced.

[0082] According to the shear angle α during shearing, the shapes of the first ridge portion 26A and the second ridge portion 36A are configured so that the radius of curvature difference ΔR satisfies Equation (4). Therefore, during shearing, it becomes possible to promote the progress of cracks from the surface of the steel plate 12 on the punch 30A side. By promoting the progress of cracks from the surface of the steel plate 12 on the punch 30A side, the residual stress on the end face of the steel plate 12 as a product remaining on the die 20A after shearing can be suppressed. Note that the shearing process method using the shearing process device 10A according to the second embodiment is the same as the case of the shearing process method using the shearing process device 10 according to the first embodiment, so duplicate explanations are omitted.

[0083] (Function and effect) In the shearing device 10A according to the second embodiment, the radius of curvature difference ΔR is calculated by subtracting the radius of curvature R2 of the second curved surface in the second ridge line portion 36A from the radius of curvature R1 of the first curved surface in the first ridge line portion 26A. When the calculated radius of curvature difference ΔR satisfies (0.001875×α 2 +0.000625×α + 0.0125) < ΔR ≦ 0.5, the shapes of the first ridge line portion 26A and the second ridge line portion 36A are configured so that the formula (2) of the present disclosure holds. Therefore, also in the second embodiment, during shearing, the biting of the blade on the die 20A side into the steel plate 12 can be suppressed. In addition, the progress of cracks from the surface of the steel plate 12 on the punch 30A side is promoted, the progress of cracks from the surface of the steel plate 12 on the die 20A side is suppressed, and the progress distance of cracks from the die 20A side can be shortened or made zero.

[0084] Therefore, similar to the case of the first embodiment, even when the steel plate 12 is sheared with the shear angle α applied, it is possible to prevent a large residual stress from occurring in the end face of the steel plate 12 remaining on the die 20A, and to suppress a decrease in fatigue characteristics and hydrogen embrittlement resistance characteristics. Other effects of the shearing device 10A according to the second embodiment are the same as those in the case of the first embodiment.

[0085] - Third Embodiment - <Structure of Shearing Device> Next, the shearing device 10B according to the third embodiment will be described with reference to FIG. 10. As shown in FIG. 10, the shearing device 10B includes a die 20B, a punch 30B, a moving device 40, and a holder 50. FIG. 10 is a cross-sectional view seen from a direction orthogonal to both the relative movement direction Y and the direction Z in which the fourth surface 34 and the holder 50 face each other, that is, a cross-sectional view seen along the shearing direction X (see FIG. 1).

[0086] Here, in the first embodiment, the entire first ridge line portion 26 of the die 20 and the entire second ridge line portion 36 of the punch 30 were both inclined surfaces. Also, in the second embodiment, the entire first ridge line portion 26A of the die 20A and the entire second ridge line portion 36A of the punch 30A were both curved surfaces. However, in the third embodiment, the first ridge line portion 26B of the die 20B is different from the first and second embodiments in that it partially combines an inclined surface and a curved surface. Also, the second ridge line portion 36B of the punch 30B is different from the first and second embodiments in that it partially combines inclined surfaces and curved surfaces corresponding to the inclined surface and the curved surface of the first ridge line portion 26B, respectively. That is, in the third embodiment, the total inclination angle difference ΔCT of the formula (2) of the present disclosure is composed of the sum of the first inclination angle difference ΔCA and the second inclination angle difference ΔCB, and ΔCT = ΔCA + ΔCB.

[0087] In the following description of the third embodiment, the first ridge line portion 26B and the second ridge line portion 36B will be mainly described. Also, regarding other configurations of the shearing device 10B according to the third embodiment other than the first ridge line portion 26B and the second ridge line portion 36B, since they are respectively equivalent to the members with the same names in the shearing devices 10 and 10A according to the first and second embodiments, duplicate descriptions will be omitted.

[0088] In the third embodiment, as shown in FIG. 10, the first ridge line portion 26B is composed of a first inclined surface 26B1 inclined with respect to the first surface 22 and a first curved surface 26B2. Also, the second ridge line portion 36B is composed of a second inclined surface 36B1 inclined with respect to the third surface 32 and a second curved surface 36B2. The first surface 22 and the third surface 32 are parallel to the direction Z in which the fourth surface 34 and the holder 50 face each other.

[0089] Here, the smaller angle formed by the first inclined surface 26B1 and the first surface 22 is set as the inclination angle C1A [degrees]. Also, the smaller angle formed by the second inclined surface 36B1 and the third surface 32 is set as the inclination angle C2A [degrees]. Then, the first inclination angle difference ΔCA [degrees] is calculated by subtracting the inclination angle C2A from the inclination angle C1A (ΔCA = C1A - C2A).

[0090] On one hand, set the radius of curvature of the first curved surface 26B2 as R1 [mm]. Also, set the radius of curvature of the second curved surface 36B2 as R2 [mm]. Then, subtract the radius of curvature R2 from the radius of curvature R1 to calculate the radius of curvature difference ΔR [mm] (ΔR = R1 - R2). Further, use the radius of curvature difference ΔR to calculate the second inclination angle difference ΔCB [degrees] from the above formula (1).

[0091] Then, set the sum of the calculated first inclination angle difference ΔCA [degrees] and the calculated second inclination angle difference ΔCB [degrees] as the total inclination angle difference ΔCT [degrees]. In the third embodiment, the shape of the first ridge line portion 26B and the shape of the second ridge line portion 36B are configured such that the total inclination angle difference ΔCT [degrees] satisfies the formula (2) of the present disclosure.

[0092] For this reason, during shearing, it becomes possible to promote the progress of cracks from the surface of the steel plate 12 on the punch 30B side. By promoting the progress of cracks from the surface of the steel plate 12 on the punch 30B side, it is possible to suppress the tensile residual stress on the end face of the steel plate 12 as a product remaining on the die 20B after shearing.

[0093] Note that since each step included in the shearing method using the shearing device 10B according to the third embodiment is the same as in the first and second embodiments, duplicate explanations are omitted.

[0094] Also in the third embodiment, similar to the first and second embodiments, shearing was performed by changing the shear angle α in the shearing device to obtain the evaluation result of the tensile residual stress of the steel plate. In the third embodiment, nine values of 0 degrees, 1 degree, 2 degrees, 3 degrees, 4 degrees, 5 degrees, 6 degrees, 8 degrees, and 10 degrees were set as the shear angle α. Also, the radius of curvature difference ΔR was set to 0.1 mm and the first inclination angle difference ΔCA was set to 18 degrees. Then, in each pattern of the nine shear angles α, the tensile residual stress on the end face of the product of the steel plate 12 after shearing was measured.

[0095] In the shearing process of the third embodiment, three types of steel plates were used as the steel plate 12: a high-strength steel plate with a tensile strength of 1180 MPa, a high-strength steel plate with a tensile strength of 980 MPa, and a steel plate with a tensile strength of 590 MPa. The evaluation results obtained when the high-strength steel plate with a tensile strength of 1180 MPa was used are shown in Table 7, the evaluation results obtained when the high-strength steel plate with a tensile strength of 980 MPa was used are shown in Table 8, and the evaluation results obtained when the steel plate with a tensile strength of 590 MPa was used are shown in Table 9, together with the specific parameters of nine examples each. Other measurement methods and evaluation methods in the third embodiment are the same as those in the first and second embodiments.

[0096] In Tables 7 to 9, "A" in the "Evaluation Results" column on the far right means that the tensile residual stress has decreased by 20% or more with respect to the reference value, as in the case explained in Table 1. Also, "B" means that the tensile residual stress has decreased by more than 10% and less than 20% with respect to the reference value. "C" means that the tensile residual stress has decreased by more than 5% and less than 10% with respect to the reference value. "D" means that the tensile residual stress has decreased by less than 5% with respect to the reference value.

[0097] Note that in Tables 7 to 9, the meaning of the notation with "-" attached as the value of the inclination angle C2 is the same as in the cases of Tables 2 and 3. Also, the meanings of "Lower Limit Formula" and "ΔCT / Lower Limit Formula" in Tables 7 to 9 are the same as in the cases of Tables 2 and 3.

[0098]

Table 7

[0099]

Table 8

[0100]

Table 9

[0101] As shown in Tables 7 to 9, when the shear angle α was 5 degrees and when the shear angle α was 6 degrees, the evaluation results for the 590 MPa steel plate were both "B", while for the 980 MPa high-strength steel plate and the 1180 MPa high-strength steel plate, the evaluation results were both "A". In this embodiment, it was found that particularly when the shear angle α was 5 degrees and when the shear angle α was 6 degrees, the high-strength steel plate of 980 MPa or more had a greater effect of suppressing the deterioration of fatigue characteristics and hydrogen embrittlement resistance than the 590 MPa steel plate.

[0102] (Function and effect) According to the shearing device 10B according to the third embodiment, the first inclination angle difference ΔCA is calculated by subtracting the inclination angle C2A of the second inclined surface 36B1 in the second ridge line portion 36B of the punch 30B from the inclination angle C1A of the first inclined surface 26B1 in the first ridge line portion 26B of the die 20B. Further, the radius of curvature difference ΔR is calculated by subtracting the radius of curvature R2 of the second curved surface 36B2 in the second ridge line portion 36B of the punch 30B from the radius of curvature R1 of the first curved surface 26B2 in the first ridge line portion 26B of the die 20B. Further, according to the formula (1) of ΔCB = 80×ΔR, the radius of curvature difference ΔR is converted as the second inclination angle difference ΔCB. Further, the total inclination angle difference ΔCT is calculated as the sum of the first inclination angle difference ΔCA and the second inclination angle difference ΔCB.

[0103] And the shapes of the first ridge line portion 26B and the second ridge line portion 36B are configured such that the total inclination angle difference ΔCT satisfies (0.15×α 2 +0.05×α + 1) < ΔCT ≦ 40. For this reason, even when both an inclined surface and a curved surface are included in the ridge line portion, during shearing, the biting of the blade on the die 20B side into the steel plate 12 can be suppressed. Further, the progress of cracks from the surface of the steel plate 12 on the punch 30B side is promoted, the progress of cracks from the surface of the steel plate 12 on the die 20B side is suppressed, and the progress distance of cracks from the die 20B side can be shortened or made zero.

[0104] Therefore, similar to the cases of the first and second embodiments, even when the steel plate 12 is subjected to shearing with the shear angle α applied, it is possible to prevent large tensile residual stress from occurring on the end face of the steel plate 12 remaining on the die 20B, and it is possible to suppress deterioration of fatigue characteristics and hydrogen embrittlement resistance characteristics. Other effects of the shearing device 10B according to the third embodiment are the same as those in the cases of the first and second embodiments.

[0105] <Modification example> In the first to third embodiments, a shearing device and a shearing method for cutting the end of the steel plate 12 have been illustratively described, but the present disclosure is not limited thereto. For example, as shown in FIGS. 11 and 12, the present disclosure can also be applied to a shearing device and a shearing method used for press working such as punching or blanking.

[0106] The shearing device 10C illustrated in FIG. 11 includes a die 20C, a punch 30C, a moving device 40, and a holder (not shown). The die 20C is a lower die of the shearing device 10C and has a first surface 22C that contacts one surface (the upper surface in FIG. 11) of the steel plate 12. Further, the shearing device 10C has a second surface 24C continuous with the first surface 22C and a first ridge line portion 26C located between the first surface 22C and the second surface 24C.

[0107] A recess is provided at the center of the first surface 22C, and the second surface 24C forms the inner wall surface of the recess. That is, the first ridge line portion 26C appears as the outer edge of the recess. The lower part of the punch 30C is inserted into the recess, and the steel plate 12 is punched according to the shape of the outer edge of the recess. The outer edge of the portion of the steel plate 12 to be punched on the upper surface of the steel plate 12 in FIG. 11 is illustrated by a region V surrounded by a dashed-dotted line. Although not shown in FIG. 11, a holder can be provided with a gap around the region V on the upper surface of the steel plate 12. The outer edge of the recess of the die 20C and the region V illustrated in FIG. 11 are rectangular with curved corners in plan view, but the present disclosure is not limited thereto and can be appropriately changed to other geometric shapes such as a circle.

[0108] The punch 30C is the upper blade of the shearing device 10C and has a third surface 32C (the lower surface in FIG. 11) that contacts the other surface of the steel plate 12. The shearing device 10C also has a fourth surface 34C (side surface) that is continuous with the third surface 32C, and a second ridge line portion 36C that is located between the third surface 32C and the fourth surface 34C.

[0109] In the modified example, the die 20C and the punch 30C are arranged to face each other in the vertical direction such that the third surface 32C of the punch 30C is inclined with respect to the first surface 22C of the die 20C. For this reason, a certain shear angle α is formed between the first ridge line portion 26C of the die 20C and the second ridge line portion 36C of the punch 30C.

[0110] In the case of punching using the shearing device 10C according to the modified example, when the punch 30C descends along the relative movement direction Y, first, the second ridge line portion 36C located at the lower end of the leftmost punch 30C in FIG. 11 contacts the steel plate 12. Then, the contact position (shearing position) between the second ridge line portion 36C and the steel plate 12 moves to the right side in FIG. 11 along the shearing direction X.

[0111] In the case of the modified example, the outer edge shapes of the first ridge line portion 26C and the second ridge line portion 36C, which are the cutting edges, circulate so that a closed space is formed inside, and they are not linear. For this reason, as the direction Z in which the fourth surface 34C and the holder face each other, it is not specified in one direction as in the case of the first to third embodiments. Regarding an arbitrary position on the outer edge of the region V on the upper surface of the steel plate 12, the direction Z in which the fourth surface 34C and the holder face each other is the normal direction at this arbitrary position.

[0112] For example, in FIG. 11, the four sides of the rectangle of the outer edge of the region V include a set of long sides that are parallel up and down and a set of short sides that are parallel left and right. When the first ridge line portion 26C and the second ridge line portion 36C are located on the long sides of the four sides of the rectangle of the region V, the direction Z in which the fourth surface 34C and the holder face each other can be set to a direction perpendicular to the shearing direction X on the upper surface of the steel plate 12.

[0113] In addition, when the first ridge line portion 26C and the second ridge line portion 36C are located on the short side of the four sides of the rectangle in the region V, the direction Z in which the fourth surface 34C and the holder face each other can be set in the same direction as the shearing direction X. That is, the direction Z in which the fourth surface 34C and the holder face each other changes according to an arbitrary position for setting the direction Z on the upper surface of the steel plate 12.

[0114] Also in the modified example, when viewed from a direction orthogonal to both the relative movement direction Y and the direction Z in which the fourth surface 34 and the holder 50 face each other, the first ridge line portion 26C has a first inclined surface inclined with respect to the first surface 22C. Further, the second ridge line portion 36C has a second inclined surface inclined with respect to the third surface 32C.

[0115] Also in the modified example, similar to the case of the first embodiment, the smaller angle formed by the first inclined surface and the direction Z in which the fourth surface 34C and the holder 50 face each other is set as the inclination angle C1. Further, the smaller angle formed by the second inclined surface and the direction Z in which the fourth surface 34C and the holder 50 face each other is set as the inclination angle C2. Then, the inclination angle C2 is subtracted from the inclination angle C1 to calculate a first inclination angle difference ΔCA (ΔCA = C1 - C2). Also, the shape of the first ridge line portion 26C and the shape of the second ridge line portion 36C are configured such that the first inclination angle difference ΔCA satisfies the formula (2) of the present disclosure.

[0116] Regarding other configurations of the shearing device 10C according to the modified example, since they are equivalent to the members with the same names in the shearing devices 10, 10A, and 10B according to the first to third embodiments, duplicate explanations are omitted. Also, each step included in the shearing method using the shearing device 10C according to the modified example is the same as in the case of the first to third embodiments.

[0117] Also in the modified example, similar to the case of the first to third embodiments, even when the steel plate 12 is sheared with the shear angle α imparted, it is possible to prevent a large tensile residual stress from occurring on the end face of the steel plate 12 remaining on the die 20C, and it is possible to suppress a decrease in fatigue characteristics and hydrogen embrittlement resistance characteristics. Regarding other effects of the shearing device 10C according to the modified example, they are the same as in the case of the first embodiment.

[0118] Note that the shear angle α is not constant and may be partially different within the range where the first ridge line portion and the second ridge line portion exist. For example, in FIG. 12, the first ridge line portion 26C1 that circulates so that a closed space is formed inside as in the modification example is illustrated.

[0119] The overall shape of the outer edge of the first ridge line portion 26C1 is elliptical in plan view, and the central portion on the upper side in FIG. 12 is recessed downward. Here, in FIG. 12, an interval between a dividing point 60 on the left side of the depression and a dividing point 62 on the right side of the depression in the first ridge line portion 26C1 is set as A1. Also, in the first ridge line portion 26C1, a left interval in FIG. 12 is set as A2 between the dividing point 60 and a dividing point 64 located on the side opposite to the interval A1. Further, in the first ridge line portion 26C1, a right interval in FIG. 12 is set as A3 between the dividing point 62 and the dividing point 64.

[0120] In the case of the die 20C illustrated in FIG. 12, for example, the shear angle α in the interval A1 can be set to about 3 degrees, the shear angle α in the interval A2 can be set to 0 degrees, and the shear angle α in the interval A3 can be set to about 10 degrees. By making the shear angle α partially different in the first ridge line portion and the second ridge line portion, it becomes possible to make the magnitude of the allowable tensile residual stress on the end face of the steel plate product after punching partially different according to the position.

[0121] Note that the method of configuring the respective shapes of the first ridge line portion and the second ridge line portion so that the shear angle α is partially different is not limited to the case of punching, and can also be adopted even when the first ridge line portion and the second ridge line portion extend linearly as in the first to third embodiments.

[0122] (Method for confirming the shear angle) Also, as a method for objectively confirming the magnitude of the shear angle α on the first ridge line portion or the second ridge line portion, for example, a region having a certain width in plan view can be set on the ridge line portion, and a plurality of measured values extracted within the set region can also be used. Specifically, for example, as shown in FIG. 12, in plan view, on the outer edge of the first ridge line portion 26C1, with a specific center point B as the center, a region having a certain width D on the left and right along the extending direction of the tangent line at the center point B is set. The width D can be set to about 3 mm, for example.

[0123] Then, at several locations, the shear angle α between the first ridge line portion 26C1 and the second ridge line portion is measured in the portion included in the set region. And, for example, when the shear angle α is defined as 3 degrees, in the portion included in the set region, the average value of the plurality of measured shear angles α is calculated, and if the calculated average value is within a range where it can be regarded as 3 degrees, the shear angle α can be determined to be 3 degrees. The specified range can be set, for example, as 3 degrees ± 0.5 degrees.

[0124] <Other Embodiments> Although the present disclosure has been described by the above-described disclosed embodiments, this description does not limit the present disclosure. It should be considered that various alternative embodiments, examples, and operation techniques will be apparent to those skilled in the art from the present disclosure.

[0125] For example, in the first to third embodiments, the case where the holder 50 is provided has been exemplarily described as the basic configuration, but in the present disclosure, even when the holder 50 is not present, the progress of cracks from the surface on the die side of the steel plate 12 can be promoted. Also, for example, it is not essential that the actual pressing force applied to the steel plate 12 by the holder 50 always achieves the specification value set for the holder 50. Even if the actual pressing force of the holder 50 is a value lower than the specification value, the same effects as in the case of the first to third embodiments can be obtained.

[0126] In addition, the shearing device according to the present disclosure can also realize a pattern in which not only the portion of the steel plate 12 remaining on the die but also the portion of the steel plate extruded by the punch is the product. Specifically, if the die and the punch described in the first to third embodiments are interchanged with each other, the surface of the steel plate 12 for which the progress of cracks is to be promoted can be reversed.

[0127] That is, in the shearing device described with reference to FIGS. 1 to 12, the respective definitions of the die and the punch and the direction of gravity are merely illustrative and may be read with each other reversed. In the present disclosure, the respective definitions of the die and the punch and the direction of gravity are merely illustrative, and even when these are reversed with each other, they may be included in the technical idea equivalent to that in the case of the first to third embodiments.

[0128] In addition, the present disclosure can also be configured by partially combining the structures of the shearing devices shown in FIGS. 1 to 12. The present disclosure includes various embodiments not described above, and the technical scope of the present disclosure is defined only by the invention specifying matters in the scope of claims appropriate from the above description.

Explanation of Reference Numerals

[0129] 10, 10A, 10B, 10C Shearing device 20, 20A, 20B, 20C Die 22, 22C First surface 24, 24C Second surface 26, 26A, 26B, 26C, 26C1 First ridge line portion 26B1 First inclined surface 26B2 First curved surface 30, 30A, 30B, 30C Punch 32, 32C Third surface 34, 34C Fourth surface 36, 36A, 36B, 36C Second ridge line portion 36B1 Second inclined surface 36B2 Second curved surface 40 Moving device 50 Holder C1, C1A, C2, C2A Inclination angle Radius of curvature of R1 and R2 X shear direction Y direction of relative movement Z direction in which the fourth surface and the holder face each other α shear angle ΔCA first tilt angle difference ΔCB second tilt angle difference ΔCT total tilt angle difference ΔR radius of curvature difference

Claims

1. A die having a first surface that contacts one surface of a steel plate, and a second surface that is continuous with the first surface via a first ridge line portion serving as a cutting edge; A punch having a third surface that contacts the other surface of the steel plate, and a fourth surface that is continuous with the third surface via a second ridge line portion serving as a cutting edge that forms a shear angle α with the first ridge line portion; A holder that sandwiches the steel plate between the first surface of the die; A moving device that relatively moves the die or the punch along the thickness direction of the steel plate between a position where the fourth surface of the punch faces the holder and a position where the fourth surface faces the second surface of the die; and The first ridge line portion includes at least one of a first inclined surface and a first curved surface inclined with respect to the first surface, and the second ridge line portion includes at least one of a second inclined surface and a second curved surface inclined with respect to the third surface, As viewed from a direction orthogonal to both the direction of the relative movement and the direction in which the fourth surface faces the holder, A first inclination angle difference ΔCA [degrees] obtained by subtracting an inclination angle [degrees] that is the smaller angle formed by the first inclined surface and the first surface from an inclination angle [degrees] that is the smaller angle formed by the second inclined surface and the third surface; A radius of curvature difference ΔR [mm] obtained by subtracting the radius of curvature [mm] of the second curved surface from the radius of curvature [mm] of the first curved surface; Using the formula of ΔCB [degrees]=80×ΔR, the second inclination angle difference ΔCB is calculated, When the sum of the first inclination angle difference ΔCA and the second inclination angle difference ΔCB is defined as a total inclination angle difference ΔCT, the total inclination angle difference ΔCT is (0.15×α +0.05×α + 1) < ΔCT ≦ 40 ２ is satisfied, and The first ridge line portion consists of the first inclined surface, and the second ridge line portion consists of the second inclined surface, A shearing device. Claim 2: A die having a first surface that contacts one surface of a steel plate, and a second surface that is continuous with the first surface via a first ridge portion serving as a cutting edge, a punch having a third surface that contacts the other surface of the steel plate, and a fourth surface that is continuous with the third surface via a second ridge portion serving as a cutting edge that forms a shear angle α with the first ridge portion, a holder that sandwiches the steel plate between the first surface of the die, a moving device that relatively moves the die or the punch along the thickness direction of the steel plate between a position where the fourth surface of the punch faces the holder and a position where the fourth surface faces the second surface of the die, the first ridge portion includes at least one of a first inclined surface and a first curved surface inclined with respect to the first surface, and the second ridge portion includes at least one of a second inclined surface and a second curved surface inclined with respect to the third surface, as viewed from a direction orthogonal to both the direction of the relative movement and the direction in which the fourth surface faces the holder, a first inclination angle difference ΔCA [degrees] obtained by subtracting the inclination angle [degrees], which is the smaller angle formed by the first inclined surface and the first surface, from the inclination angle [degrees], which is the smaller angle formed by the second inclined surface and the third surface, a radius of curvature difference ΔR [mm] obtained by subtracting the radius of curvature [mm] of the second curved surface from the radius of curvature [mm] of the first curved surface, Using the formula of ΔCB [degrees]=80×ΔR, calculate the second inclination angle difference ΔCB, When the sum of the first inclination angle difference ΔCA and the second inclination angle difference ΔCB is defined as a total inclination angle difference ΔCT, the total inclination angle difference ΔCT satisfies (0.15×α 2 +0.05×α +1)<ΔCT≤40 and the first ridge portion consists of the first curved surface, and the second ridge portion consists of the second curved surface, a shearing device.

3. A die having a first surface that contacts one surface of a steel plate and a second surface that is continuous with the first surface via a first ridge line portion serving as a cutting edge, a punch having a third surface that contacts the other surface of the steel plate and a fourth surface that is continuous with the third surface via a second ridge line portion that is a cutting edge forming a shear angle α with the first ridge line portion, a holder that sandwiches the steel plate between the first surface of the die, a moving device that relatively moves the die or the punch along the thickness direction of the steel plate between a position where the fourth surface of the punch faces the holder and a position where the fourth surface faces the second surface of the die, the first ridge line portion includes at least one of a first inclined surface and a first curved surface inclined with respect to the first surface, and the second ridge line portion includes at least one of a second inclined surface and a second curved surface inclined with respect to the third surface, as viewed from a direction orthogonal to both the direction of the relative movement and the direction in which the fourth surface faces the holder, a first inclination angle difference ΔCA [degrees] obtained by subtracting the inclination angle [degrees], which is the smaller angle formed by the first inclined surface and the first surface, from the inclination angle [degrees], which is the smaller angle formed by the second inclined surface and the third surface, a radius of curvature difference ΔR [mm] obtained by subtracting the radius of curvature [mm] of the second curved surface from the radius of curvature [mm] of the first curved surface, Using the formula of ΔCB [degrees]=80×ΔR, calculate the second inclination angle difference ΔCB, When the sum of the first inclination angle difference ΔCA and the second inclination angle difference ΔCB is defined as the total inclination angle difference ΔCT, the total inclination angle difference ΔCT is, (0.15×α 2 +0.05×α +1)<ΔCT≦40 satisfies, the first ridge line portion is composed of the first inclined surface and the first curved surface, and the second ridge line portion is composed of the second inclined surface and the second curved surface, a shearing device.

4. A die having a first surface that contacts one surface of the steel plate and a second surface that is continuous with the first surface via a first ridge line portion serving as a cutting edge, a punch having a third surface that contacts the other surface of the steel plate and a fourth surface that is continuous with the third surface via a second ridge line portion that is a cutting edge forming a shear angle α with the first ridge line portion, a holder that sandwiches the steel plate between the first surface of the die, a moving device that relatively moves the die or the punch along the thickness direction of the steel plate between a position where the fourth surface of the punch faces the holder and a position where the fourth surface faces the second surface of the die, the first ridge line portion includes at least one of a first inclined surface and a first curved surface inclined with respect to the first surface, and the second ridge line portion includes at least one of a second inclined surface and a second curved surface inclined with respect to the third surface, as viewed from a direction orthogonal to both the direction of the relative movement and the direction in which the fourth surface faces the holder, a first inclination angle difference ΔCA [degrees] obtained by subtracting the inclination angle [degrees], which is the smaller angle formed by the first inclined surface and the first surface, from the inclination angle [degrees], which is the smaller angle formed by the second inclined surface and the third surface, a radius of curvature difference ΔR [mm] obtained by subtracting the radius of curvature [mm] of the second curved surface from the radius of curvature [mm] of the first curved surface, ΔCB [degrees] = 80 × ΔR is used in the formula to calculate a second inclination angle difference ΔCB, when the sum of the first inclination angle difference ΔCA and the second inclination angle difference ΔCB is defined as a total inclination angle difference ΔCT, the total inclination angle difference ΔCT is, (0.15 × α2 + 0.05 × α + 1) < ΔCT ≤ 40 is satisfied, the shear angle α is 0.5 degrees or more and 10 degrees or less, a shearing device.

5. A die having a first surface that contacts one surface of the steel plate and a second surface that is continuous with the first surface via a first ridge line portion serving as a cutting edge, A punch having a third surface that contacts the other surface of the steel plate and a fourth surface that is continuous with the third surface via a second ridge line portion that is a cutting edge forming a shear angle α with the first ridge line portion. A holder that sandwiches the steel plate between the first surface of the die. A moving device that relatively moves the die or the punch along the thickness direction of the steel plate between a position where the fourth surface of the punch faces the holder and a position where the fourth surface faces the second surface of the die. The first ridge line portion includes at least one of a first inclined surface and a first curved surface inclined with respect to the first surface, and the second ridge line portion includes at least one of a second inclined surface and a second curved surface inclined with respect to the third surface. As viewed from a direction orthogonal to both the direction of the relative movement and the direction in which the fourth surface faces the holder. A first inclination angle difference ΔCA [degrees] obtained by subtracting the inclination angle [degrees], which is the smaller angle formed by the first inclined surface and the first surface, from the inclination angle [degrees], which is the smaller angle formed by the second inclined surface and the third surface. A radius of curvature difference ΔR [mm] obtained by subtracting the radius of curvature [mm] of the second curved surface from the radius of curvature [mm] of the first curved surface. ΔCB [degrees] = 80 × ΔR Using the formula, a second inclination angle difference ΔCB is calculated. When the sum of the first inclination angle difference ΔCA and the second inclination angle difference ΔCB is defined as a total inclination angle difference ΔCT, the total inclination angle difference ΔCT is (0.15 × α2 + 0.05 × α + 1) < ΔCT ≦ 40 Satisfies The shear angle α is 0.5 degrees or more and 10 degrees or less. The shearing device according to any one of claims 1 to 3.

6. The clearance between the die and the punch is 5% or more and 25% or less of the thickness of the steel plate. The shearing device according to any one of claims 1 to 5.

7. The step of preparing the shearing device according to any one of claims 1 to 6, The step of placing a steel plate on the first surface of the die of the prepared shearing device and, The step of supporting the placed steel plate by the holder, The step of using the moving device to relatively move the die or the punch along the thickness direction of the steel plate so that the first ridge line portion and the second ridge line portion are close to each other to cut the steel plate, A shearing method comprising:

8. The tensile strength of the steel plate is 980 MPa or more, The shearing method according to claim 7.

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