JP7541235B2 - Scrap coining method and shearing device - Google Patents

Description

This disclosure relates to a scrap coining method and a shearing device.

Conventionally, a scrap coining method has been known in which scrap generated during shearing, in which a workpiece (steel plate) is sheared to obtain a processed material (product), is used as a coining punch rather than being discarded, by partially punching out the steel plate or cutting off the ends.

For example, Patent Document 1 describes a scrap coining method in which the end face of a cut material punched out from a workpiece using a shearing device is brought into contact with and rubbed against the end face of the sheared surface of the workpiece (product) on a die. Hereinafter, processes including the scrap coining method will also be referred to simply as "coining." Patent Document 1 claims that coining can produce steel plates with sheared surfaces that have excellent resistance to hydrogen embrittlement and fatigue strength.

International Publication No. 2016/136909

Here, when scrap is rubbed against a product made from a relatively high-strength steel plate, the load generated between the product and scrap during coining becomes large. When the load during coining becomes large, additional capital investment is required to reduce the burden on the shearing device that bears the load, for example by increasing the capacity of a shock mitigation device such as a gas cushion, which increases the cost of the shearing device.

In view of the above problems, the present disclosure aims to provide a scrap coining method and a shearing device that can suppress increases in the cost of shearing devices used in scrap coining.

The scrap coining method according to the first aspect of the present disclosure uses a shearing device equipped with a die, a holder that holds the workpiece between the die and the holder, a punch that is arranged with a clearance between the die and the holder, and a counter punch that is arranged opposite the punch, and shears the workpiece with the die and punch to form a product. The product is supported between the die and the holder, and a portion that has been separated from the workpiece by shearing is placed as scrap on the tip of the counter punch. With the scrap placed on the upper side, the counter punch is moved toward the product, and the outer edge of the scrap is brought into contact with the end face of the supported product, thereby bending and deforming the outer edge of the scrap, and coining is performed.

In the first embodiment, when the counter punch is moved toward the product after shearing, the outer edge of the scrap is bent and deformed during coining when the scrap comes into contact with the end face of the product. The bending deformation absorbs the load that occurs between the product and the scrap during coining, reducing the burden on the shearing device that receives the load. This eliminates the need to increase the capacity of a shock mitigation device such as a gas cushion.

The shearing device according to the second aspect of the present disclosure includes a die, a holder for clamping the workpiece between the die and the punch, a punch arranged with a clearance between the punch and the die, and a counter punch arranged opposite the punch and having a base and a tip end that is provided on the workpiece side of the base and has a smaller diameter than the base.

In the second embodiment, as in the first embodiment, the load generated between the product and the scrap during coining is absorbed by the bending deformation of the outer edge of the scrap, thereby reducing the burden on the shearing device that receives the load. This eliminates the need to increase the capacity of a shock mitigation device such as a gas cushion. In addition, the counter punch has a tip portion that is smaller in diameter than the base portion, and the scrap is placed above the tip portion. Therefore, compared to coining, which uses a counter punch whose tip portion has the same diameter as the base portion and whose upper surface is flat, the outer edge of the scrap can be smoothly bent and deformed to conform to the shape of the narrowed tip portion during coining.

The present disclosure provides a scrap coining method and a shearing device that can suppress increases in the cost of shearing devices used in scrap coining.

FIG. 2 is a cross-sectional view illustrating a configuration of a shearing device according to an embodiment of the present disclosure. 2A to 2F are perspective views for explaining various patterns that can be applied as the upper structure of the counter punch of the shearing device according to this embodiment. FIG. 11 is a cross-sectional view (part 1) illustrating a shearing method using the shearing device according to this embodiment when the outer edge of the scrap protrudes outside the base of the counter punch. FIG. 2 is a cross-sectional view (part 2) illustrating a shearing method using the shearing device according to this embodiment when the outer edge of the scrap protrudes outside the base of the counter punch. FIG. 11 is a cross-sectional view (part 1) illustrating a shearing method using the shearing device according to the present embodiment when the outer edge of the scrap is located inside the base of the counter punch. FIG. 2 is a cross-sectional view (part 2) illustrating a shearing method using the shearing device according to this embodiment when the outer edge of the scrap is located inside the base of the counter punch. 1A to 1C are cross-sectional views illustrating a shear processing method using a shear processing device according to a comparative example (part 1). 13 is a cross-sectional view illustrating a shear processing method using a shear processing device according to a comparative example (part 2). FIG. FIG. 11 is a cross-sectional view illustrating a configuration of a shearing device according to a modified example of the present embodiment. 13A to 13C are cross-sectional views illustrating other patterns that can be applied as the upper structure of the counter punch of the shear processing device according to the modified example. FIG. 11(A) is a graph illustrating the relationship between the protrusion ratio D/L and the maximum load P during coining in Example 1, and FIG. 11(B) is a graph illustrating the relationship between the protrusion ratio D/L and the amount of reduction in residual stress Δσ in Example 1. FIG. 12(A) is a graph illustrating the relationship between the protrusion ratio D/L and the maximum load P during coining in Example 2, and FIG. 12(B) is a graph illustrating the relationship between the protrusion ratio D/L and the amount of reduction in residual stress Δσ in Example 2. FIG. 13(A) is a graph illustrating the relationship between the protrusion ratio D/L and the maximum load P during coining in Example 3, and FIG. 13(B) is a graph illustrating the relationship between the protrusion ratio D/L and the reduction amount Δσ of residual stress in Example 3. FIG. 14(A) is a graph illustrating the relationship between the protrusion ratio D/L and the maximum load P during coining in Example 4, and FIG. 14(B) is a graph illustrating the relationship between the protrusion ratio D/L and the amount of reduction in residual stress Δσ in Example 4. FIG. 15(A) is a graph illustrating the relationship between the protrusion ratio D/L and the maximum load P during coining in Example 5, and FIG. 15(B) is a graph illustrating the relationship between the protrusion ratio D/L and the amount of reduction in residual stress Δσ in Example 5. FIG. 16(A) is a graph illustrating the relationship between the protrusion ratio D/L and the maximum load P during coining in Example 6, and FIG. 16(B) is a graph illustrating the relationship between the protrusion ratio D/L and the amount of reduction in residual stress Δσ in Example 6. FIG. 17(A) is a graph illustrating the relationship between the protrusion ratio D/L and the maximum load P during coining in Example 7, and FIG. 17(B) is a graph illustrating the relationship between the protrusion ratio D/L and the amount of reduction in residual stress Δσ in Example 7. FIG. 18(A) is a graph illustrating the relationship between the protrusion ratio D/L and the maximum load P during coining in Example 8, and FIG. 18(B) is a graph illustrating the relationship between the protrusion ratio D/L and the amount of reduction in residual stress Δσ in Example 8. FIG. 11 is a graph illustrating the relationship between the diameter-to-thickness ratio W/T and the residual stress reduction amount Δσ in Examples 9 to 11 when D<0.

The present embodiment will be described below. In the following description of the drawings, identical or similar parts are given the same or similar symbols. However, the relationship between thickness and planar dimensions in the drawings, and the ratio of thickness of each device and each component, etc., differ from the actual ones. Therefore, specific thicknesses and dimensions should be determined with reference to the following description. In addition, there are parts in which the dimensional relationships and ratios differ between the drawings.

<Structure of shear processing device>
1, a shearing device 10 according to this embodiment is, for example, a hydraulic press that is arranged in a steelworks and is capable of performing piercing to form a circular hole by punching a workpiece 20. The shearing device 10 includes a die 12, a holder 14, a punch 16, and a counter punch 18.

The shearing device 10 has a clearance 15 between the inner surface of the die 12 and the outer surface of the punch 16 and the outer surface of the counter punch 18. Figure 1 illustrates a state in which a clearance 15 having a certain width L is formed between position A1 of the inner surface of the die 12 and position A2 of the outer surface of the counter punch 18. The clearance 15 is determined by the product of the thickness T of the workpiece 20 and a clearance ratio that is preset according to the desired processing quality.

The punch 16 and the counter punch 18 are each connected to a moving device (not shown). The moving device can be realized, for example, by an electric motor or a hydraulic mechanism. The moving device allows the die 12 and the punch 16 to move independently relative to each other in a direction perpendicular to the horizontal plate surface of the workpiece 20 (the up-down direction in FIG. 1).

In this embodiment, the workpiece 20 is a steel plate, which is a metallic material. In this disclosure, the workpiece 20 is not limited to a metallic material, and any material, such as wood or a resin material, can be used. The workpiece 20 has a certain thickness T, and is sandwiched horizontally between the die 12 and the holder 14 before punching. In this embodiment, "high strength" means that the tensile strength of the steel plate is about 980 MPa or more. The definition of the tensile strength of the steel plate follows, for example, "ISO 6892-1:2009".

Figure 1 illustrates a state in which the workpiece 20 is separated into a product 22 and scrap 24 immediately after being punched and before coining. In this embodiment, the die hole is approximately circular in plan view, and the diameter W of the punched hole, which is the diameter of the die hole (the distance between the dies in the left-right direction in Figure 1), is the same as the diameter (diameter) of the scrap 24. Therefore, the radius RS of the scrap 24 before coining is half the diameter W of the punched hole (diameter W of the scrap 24 before coining).

The holder 14 is placed on top of the die 12 and sandwiches the workpiece 20 between the die 12 and the holder 14. The punch 16 is a cylindrical punching member, and is placed above the workpiece 20 in FIG. 1 before punching. The punch 16 descends from above onto the portion of the workpiece 20 that is not sandwiched between the die 12 and the holder 14, punching the workpiece 20 into a circular shape.

(Counter punch)
The counter punch 18 is a cylindrical pushing member, and before punching, is disposed below the workpiece 20 in Fig. 1, in the same straight line along the direction of movement of the punch 16, and facing the punch 16. The counter punch 18 has a base 18A and a tip 18B provided on the workpiece 20 side of the base 18A. During punching, scrap 24 is formed by punching with the punch 16, and the formed scrap 24 is placed on the tip 18B of the counter punch 18 located below. After punching, the counter punch 18 pushes the scrap 24 toward the upper side in Fig. 1, thereby performing coining.

(base)
In this embodiment, the diameter of the base 18A of the counter punch 18 is the same as the diameter of the punch 16. Therefore, the radius RCP of the base 18A is also the same as the radius of the punch 16. Note that in FIG. 1, the cylindrical upper part of the base 18A is partially illustrated, and the shape of the lower part is omitted. The shape of the lower part of the base 18A may be cylindrical like the upper part, or may be wider or narrower than the upper part. The shape of the lower part of the base 18A is arbitrary as long as it functions as the counter punch 18.

(Tip)
The tip 18B is a spherical (dome-shaped) region provided at the top of the counter punch 18, and is curved in an arc so as to gradually reduce in diameter from the base 18A side (lower side in FIG. 1) toward the workpiece 20 side (upper side in FIG. 1). The reduced diameter portion of the tip 18B promotes bending of the outer edge of the scrap 24 during coining.

The apex B of the tip 18B in FIG. 1 is the top of the counter punch 18 and is in contact with the underside of the scrap 24. In this embodiment, a line passing through the apex B and perpendicular to the horizontal plate surface of the workpiece 20 is defined as the reference line C. In this embodiment, the reference line C is the central axis passing through the center of the cylindrical bottom circle of the counter punch 18. In this embodiment, the shape of the upper part including the base 18A and the tip 18B of the counter punch 18 is rotationally symmetrical about the reference line C. In this embodiment, the distance between the contact point with the scrap 24 (apex B) and the outer surface of the counter punch 18 is the same as the radius RCP of the base 18A.

In this disclosure, the hole (punch hole) of the product is not limited to a perfect circle in plan view, but may be a distorted circle such as an ellipse or a bean shape. Even if the hole (punch hole) of the product is a distorted circle, it is sufficient that the tip 18B has a height H so that the area between the contact point between the tip 18B and the scrap 24 and the outer surface of the base 18A is reduced in diameter and a certain distance is formed in cross section.

The tip 18B has a certain height H. Although the tip 18B in FIG. 1 has a relatively flat shape, the shape of the tip 18B of the counter punch 18 of the present disclosure is not limited to this and can be modified as appropriate as long as it is possible to fold the outer edge of the scrap 24.

As another shape of the tip of the present disclosure, for example, as shown in FIG. 2(A), the tip 18B may be spherical in shape with the radius RS of the scrap 24 and the height H being equal. In other words, the shape of the tip 18B in FIG. 2(A) is spherical, and the radius of curvature of the tip 18B is smaller than the radius of curvature of the tapered portion of the tip 18B in FIG. 1.

Also, as shown in FIG. 2(B), the tip 18B may have a flat upper surface. In other words, the shape of the tip 18B in FIG. 2(B) is a spherical shape with the top part cut out to form a flat upper surface. The surface of the area between the upper surface and the base 18A is curved and has a smaller diameter than the base 18A.

Also, as shown in FIG. 2(C), the tip 18B may be conical and pointed upward. That is, the surface of the tip 18B is not an arc-shaped curved surface in cross section, but a linear inclined surface. Note that in the present disclosure, the shape of the tip 1 that points upward is not limited to a cone shape, and may be another geometric shape, such as a pyramid shape.

Alternatively, as shown in FIG. 2(D), the tip 18B may be a truncated cone shape having a flat upper surface including an apex B. The surface of the region between the upper surface and the base 18A is tapered, and the diameter gradually decreases from the base 18A. Alternatively, as shown in FIG. 2(E), the tip 18B may be cylindrical with a smaller diameter than the cylindrical base 18A.

Also, as shown in FIG. 2(F), the tip 18B may be formed by overlapping a number of cylindrical sections. The cylindrical sections are arranged so that the diameter becomes smaller toward the top. The number of overlapping cylindrical sections can be set as desired. Even in the case of tip 18B in FIG. 2(F), where a number of cylindrical sections are overlapped to form a stepped shape, the diameter gradually decreases toward the top, and the outer edge of the scrap 24 can be folded during coining.

<Scrap coining method>
Next, a scrap coining method using the shearing device 10 according to this embodiment will be described with reference to Figures 3 to 6. First, before punching, the workpiece 20 is sandwiched and supported by the die 12 and the holder 14. Furthermore, the counter punch 18 is in contact with the workpiece 20, and a predetermined pressure (back pressure) is applied to the workpiece 20.

In the scrap coining method of the present embodiment described below, the coining action is exemplified as a case where the scrap 24 is pressed against the product 22 until it penetrates the upper side of the product 22. However, in the coining disclosed herein, the action of pressing the scrap against the product until it penetrates the upper side is not essential. For example, the scrap may be pressed into a certain area where a partial height is formed on the end face of the workpiece, such as the area from the surface (lower surface) on the die side of the workpiece to the height of the boundary between the shear surface and the fracture surface.

Even in coining, where the scrap is pushed partially into the product without penetrating the top of the product, the effect of reducing residual stress can be obtained. When the scrap is not penetrating, it may not be strictly necessary to align the position of the scrap placed on the counter punch with the position of the punching hole, as compared to when the scrap is penetrating. In this case, there is no need to apply a certain pressure to the workpiece by bringing the counter punch into contact with the workpiece before punching.

Next, the moving device is operated to lower the punch 16, and the die 12 and punch 16 punch out the workpiece 20 to form a product 22. The formed product 22 is supported between the die 12 and the holder 14. Meanwhile, the portion separated from the workpiece 20 becomes scrap 24. As shown in FIG. 1, the scrap 24 is supported by being sandwiched between the punch 16 and the counter punch 18, and is placed on the tip 18B of the counter punch 18 with a predetermined pressure (back pressure) applied.

Next, as shown in FIG. 3, while supporting the scrap 24 placed on the tip 18B, the punch 16 and the counter punch 18 are raised together toward the product 22.

By the upward movement of the punch 16 and the counter punch 18, the outer edge of the scrap 24 comes into contact with the end face of the hole of the product 22 supported by the die 12 and the holder 14. Then, by further raising the punch 16 and the counter punch 18 together, the outer edge of the scrap 24 is pressed against the end face of the hole of the product 22, and the outer edge of the scrap 24 is bent and deformed toward the lower side in FIG. 3. During the upward movement, the outer edge of the scrap 24 first comes into contact with the end face of the product 22 and applies a load to the shear processing device 10, thereby performing coining. The bending deformation is plastic deformation. Then, after the bending deformation, the punch 16 and the counter punch 18 are further raised together to pull the scrap 24 above the product 22.

Here, it is possible to consider two cases: when the scrap 24 is pulled up above the product 22, the outer edge of the scrap 24 protrudes outside the base 18A of the counter punch 18, and when it is located inside the base 18A. The inventors have found that in each case, it is possible to obtain a load reduction effect or a residual stress reduction effect in the product 22.

Specifically, first, as shown in Figures 4 and 6, the protruding width D is set as the width by which the outer edge of the scrap 24 protrudes outward from the base 18A of the counter punch 18, measured along the width L direction of the clearance 15. The protruding width D can be set under virtual conditions in which the shape of the tip 18B and the shape of the center of the deformed scrap 24 are in close contact with each other, with their central axes aligned, as shown in Figures 4 and 6. The protruding width D can be set, for example, by numerical analysis such as the finite element method.

In other words, when the scrap coining method disclosed herein is applied to actual shear processing, it is not essential that the scrap be in complete contact with the tip of the counter punch after coining or when the scrap is pulled above the product. In reality, the scrap may be partially raised from the tip.

As shown in FIG. 4, when the outer edge of the scrap 24 protrudes outside the base 18A of the counter punch 18, the protruding width D is defined as a positive value (D>0). Also, as shown in FIG. 6, when the outer edge of the scrap 24 is located inside the base 18A of the counter punch 18, the protruding width D is defined as a negative value (D<0). Below, the cases of D>0 and D<0 will be explained separately. Note that the case where the protruding width D is zero (D=0) is included in the case of D<0. That is, in this embodiment, when D=0, the behavior is considered to be the same as when D<0, in which the outer edge of the scrap 24 does not contact the product 22.

(When D>0)
As shown in Fig. 4, when the scrap 24 is pulled up above the product 22 and the outer edge of the scrap 24 protrudes outward from the base 18A of the counter punch 18, the shape of the tip 18B closely matches the shape of the center of the deformed scrap 24. Also, the outer edge of the scrap 24 protrudes outward from the base 18A of the counter punch 18. In Fig. 4, the position A3 of the outer edge of the protruding scrap 24 is illustrated as being inside the clearance 15. Also, the radius RS of the scrap 24 after bending deformation in Fig. 4 is shorter than the radius RS of the scrap 24 before bending deformation in Fig. 1.

Therefore, when the punch 16 and the counter punch 18 are raised after the scrap 24 is bent, the scrap 24 rises while the protruding outer edge remains in contact with the product 22. Therefore, when D>0, coining by the scrap 24 continues even after the bending deformation.

When D>0, the load reduction effect is obtained by setting the protrusion ratio D/L of the protrusion width D to the width of the clearance 15 within a certain range. In this embodiment, the protrusion ratio D/L is set to less than 0.8 so as to enhance the load reduction effect, as will be explained later using Examples 1 to 8. Furthermore, in this embodiment, it is more preferable to set the protrusion ratio D/L to less than 0.6, as this further enhances the load reduction effect.

(When D<0)
On the other hand, as shown in Fig. 5, when the outer edge of the scrap 24 first comes into contact with the end surface of the product 22 and is bent and deformed after punching, the entire lower surface of the scrap 24 may not be in close contact with the surface of the tip portion 18B. Note that in Fig. 5, the position of the outer edge of the protruding scrap 24 and the radius of the scrap 24 are omitted for ease of viewing. Then, as shown in Fig. 6, the diameter of the scrap 24 becomes smaller than the diameter W of the punched hole due to deformation caused by coining.

Therefore, when the scrap 24 is pulled above the product 22, if the outer edge of the scrap 24 is located inside the base 18A of the counter punch 18, the outer edge of the scrap 24 does not protrude outside the base 18A of the counter punch 18.

When D<0, the rigidity of the scrap 24 has a large effect on the residual stress reduction effect. Therefore, in this embodiment, when D<0, the residual stress reduction effect is obtained by setting the diameter-thickness ratio W/T of the diameter W of the punched hole (diameter W of the scrap 24 before coining) to the thickness T of the workpiece 20 within a certain range. In this embodiment, the diameter-thickness ratio W/T is set to less than 500 so as to enhance the residual stress reduction effect, as will be explained using Examples 9 to 11 that will be presented later. Furthermore, in this embodiment, it is more preferable to set the diameter-thickness ratio W/T to less than 60, since this can further enhance the residual stress reduction effect.

Comparative Example
7, in the case of the shearing device 10Z according to the comparative example, the tip 18B of the counter punch 18 does not have a portion with a smaller diameter than the base 18A. The upper part of the counter punch 18 in the comparative example is cylindrical and has the base 18A and the tip 18B with the same diameter as the base 18A. Therefore, after punching, when the counter punch 18 rises and the outer edge of the scrap 24 and the end face of the product 22 first come into contact with each other, the load generated by the contact is larger than that in the present embodiment.

The scrap 24 is supported from above and below by the punch 16 and counter punch 18, which are of the same diameter. Therefore, as shown in FIG. 8, when the punch 16 and counter punch 18 rise and the scrap 24 is pulled up to the top of the product 22, it is practically difficult to bend and deform the outer edge of the scrap 24 as in this embodiment.

<Modification>
The shearing apparatus 10 according to the present embodiment shown in FIGS. 1 to 6 is a shearing apparatus 10 that performs a piercing process to form a hole by punching the center of the workpiece 20, but the present disclosure is not limited to this and can be applied to other shearing processes. The shearing apparatus 10A according to a modified example shown in FIG. 9 is a shearing apparatus that can perform a trimming process to cut the outer periphery of the workpiece 20. The shearing apparatus 10A according to the modified example can be used, for example, in the process of processing or manufacturing steel parts. In addition, it may be disposed in a hot rolling line of a steelworks. The shearing apparatus 10A can be applied to a crop shear that cuts the end of a steel plate as the workpiece 20 into a straight or curved shape.

The shearing device 10A according to the modified example includes a die 12, a holder 14, a punch 16, and a counter punch 18, similar to the shearing device 10 according to the present embodiment. In the case of the shearing device 10A illustrated in FIG. 9, unlike the case of piercing, the end face of the product 22 to be coined is present only on one side (the left side in FIG. 9).

For this reason, the tip 18B of the counter punch 18 has a reduced diameter portion only to the left of the boundary position B1 in FIG. 9. Although not shown, the reduced diameter portion extends linearly in a direction penetrating the paper surface of FIG. 9. A flat upper surface is formed in the portion of the tip 18B to the right of the boundary position B1 in FIG. 9. The surface of the area between the upper surface and the base 18A is tapered.

In FIG. 9, the reference line C is a line perpendicular to the horizontal plate surface of the workpiece 20, passing through the boundary position B1 at the left end of the upper surface where the tip 18B of the counter punch 18 and the scrap 24 come into contact. In the modified example, the distance RCP of the area of the reduced diameter portion between the contact point (boundary position B1) between the tip 18B and the scrap 24 and the outer surface of the base 18A is defined between the reference line C and the outer surface of the base 18A. The other components of the shear processing device 10A according to the modified example are equivalent to the components of the same name in the shear processing device 10 according to the present embodiment, so a duplicated description will be omitted.

The scrap coining method using the shearing device 10A according to the modified example is the same as that of the present embodiment. However, in the case of the shearing device 10A capable of performing trimming, an open space may exist in which no member is provided to hinder the movement of the scrap 24 in the horizontal direction of the scrap 24, as in the area to the right of the scrap 24 in FIG. 9. For this reason, unless the scrap 24 is securely sandwiched and supported by the punch 16 and the counter punch 18, the scrap 24 may not be completely held during coining. As a result, during coining, the scrap 24 may move horizontally due to the reaction force from the product 22, and the position of the scrap 24 above the counter punch 18 may be shifted.

For this reason, in the case of the modified example, it is preferable to set the area of the flat upper surface of the tip portion 18B, which is the area that comes into contact with the scrap 24, to, for example, at least half the radius RCP of the counter punch 18 so that it has a certain area necessary to support the scrap 24. However, the area of the upper surface is not limited to this and can be changed as appropriate.

As shown in FIG. 10, the shear processing device 10B capable of performing trimming may be configured so that the tip 18B of the counter punch 18 has a tapered portion that is linearly symmetrical with respect to the reference line C. That is, the shape of the tip 18B in FIG. 10 is the same as the shape of the tip 18B in FIG. 1, and curved portions that are tapered from the base 18A are formed on both sides of the reference line C that passes through the apex B. The shape of the tip of the counter punch of the shear processing device capable of performing trimming may be tapered or curved, or may be stepped, etc., with the same cross section as in FIG. 9 and FIG. 10.

9 and 10 exemplarily illustrate the case of trimming with a straight cut, but the present disclosure may also provide trimming with a curved cut. Specifically, for example, the curved portion of the cut line may be subdivided into a plurality of straight portions, and shearing may be performed in each of the subdivided straight portions so that coining is performed using a counter punch having a reduced diameter tip, as in the case of FIG. 9 and FIG. 10.

Next, the relationship between the protrusion ratio D/L and the maximum load applied to the shear processing device 10 will be explained using the following Examples 1 to 8.

Example 1
In Example 1, a 980 MPa-class steel plate was prepared as the workpiece 20, and piercing was performed using a shearing device 10 equipped with a counter punch 18 having a spherical head-shaped tip 18B as shown in FIG. 2(A). The thickness T of the steel plate was set to 0.5 mm, the clearance ratio was set to 10% of the thickness T, and the width L of the clearance 15 was set to 0.05 mm. The diameter W of the punched hole was set to 30 mm. The diameter-thickness ratio W/T was 60. The radius RCP of the counter punch 18 was set to 15 mm. The height H of the tip 18B was changed to vary the radius RS of the scrap 24 after coining in a plurality of patterns.

Then, the protrusion width D, protrusion ratio D/L, maximum load P during coining, and reduction amount ΔP of maximum load P were measured for each of the different radii RS. In addition, the residual stress in the thickness direction (vertical direction in FIG. 1) and the residual stress in the width direction (horizontal direction in FIG. 1) were measured at the end face of the product 22 after coining. Note that the residual stress can be measured by a known method such as an X-ray method or a hole drilling method. In this embodiment, the residual stress was measured by irradiating the center of the end face in the thickness direction and the width direction with an X-ray beam diameter of 500 μm. Note that the residual stress may be measured together with the load by analysis using simulation software or the like.

In addition, piercing was performed using a shearing device 10Z according to a comparative example that includes a counter punch 18 that does not have a tapered portion and whose tip has the same shape as its base. Other conditions in the comparative example are the same as those in Example 1. The difference between the maximum load P in Example 1 and the maximum load P in the comparative example was calculated as the reduction amount ΔP of the maximum load P.

In addition, the residual stress of the product 22 obtained when the shearing process was completed by performing only punching without performing coining in the shearing process device 10Z according to the comparative example was measured as a reference standard value. The processing conditions other than coining in the shearing process in which only punching was performed were the same as those in Example 1. The difference between the residual stress in Example 1 and the residual stress of the reference standard value was calculated as the residual stress reduction amount Δσ. The measurement results are shown in Table 1 below and FIG. 11.

In the following Figures 11 to 18, in the protrusion ratio D/L on the horizontal axis, D/L = 1 corresponds to the comparative example. Also, the smaller the value of D/L, the larger the value of the tip height H in each example. Also, when the value of the residual stress σ shown in the table is positive, it means that the residual stress is a tensile residual stress, and when the value of the residual stress σ is negative, it means that the residual stress is a compressive residual stress. In this embodiment, it is preferable from the viewpoint of ensuring the quality of the product 22 that the residual stress tends to be compressive, that is, that the value of the residual stress σ is small.

As shown in FIG. 11(A), in Example 1, the smaller the protrusion ratio D/L, the smaller the maximum load P. Also, as shown in FIG. 11(B), in Example 1, the effect of reducing residual stress is also obtained. For example, when the protrusion ratio D/L is 0.4 mm, the reduction amount Δσ of residual stress in the plate thickness direction is 552.29 MPa or more, and the reduction amount Δσ of residual stress in the plate width direction is 1000.37 MPa or more. The effect of reducing residual stress in Example 1 is comparable to that of the comparative example, and is effective in actual shear processing.

Example 2
In Example 2, a 980 MPa-class steel plate was prepared as the workpiece 20, and piercing was performed using a shearing device 10 equipped with a counter punch 18 having a spherical head-shaped tip 18B as shown in FIG. 2(A). The thickness T of the steel plate was set to 1.6 mm, the clearance ratio was set to 10% of the thickness T, and the width L of the clearance 15 was set to 0.16 mm. The diameter W of the punched hole was set to 30 mm. The diameter-thickness ratio W/T was 18.75. The radius RCP of the counter punch 18 was set to 10 mm. The height H of the tip 18B was changed to vary the radius RS of the scrap 24 after coining.

Then, the protrusion width D, protrusion ratio D/L, maximum load P during coining, and reduction amount ΔP of maximum load P were measured for each case. In addition, the residual stress on the end surface of the product 22 after coining was measured in both the plate thickness direction and plate width direction. The other measurement conditions were the same as in Example 1. The measurement results are shown in Table 2 below and Figure 12.

As shown in Figure 12 (A), in Example 2 as well, the smaller the protrusion ratio D/L, the smaller the maximum load P. Also, as shown in Figure 12 (B), in Example 2, the effect of reducing residual stress is also obtained. For example, when the protrusion ratio D/L is 0.3 mm, the reduction amount Δσ of residual stress in the plate thickness direction is 539.13 MPa or more, and the reduction amount Δσ of residual stress in the plate width direction is 980.31 MPa or more. The effect of reducing residual stress in Example 2 is effective in actual shear processing, just like in Example 1.

Example 3
In Example 3, a 980 MPa-class steel plate was prepared as the workpiece 20, and piercing was performed using the shearing device 10 equipped with a counter punch 18 having a spherical head-shaped tip 18B as shown in FIG. 2(A). The thickness T of the steel plate was set to 1.6 mm, the clearance ratio was set to 10% of the thickness T, and the width L of the clearance 15 was set to 0.16 mm. The diameter W of the punched hole was set to 30 mm. The diameter-thickness ratio W/T was 18.75. The radius RCP of the counter punch 18 was set to 15 mm. The height H of the tip 18B was changed to vary the radius RS of the scrap 24 after coining.

Then, the protrusion width D, protrusion ratio D/L, maximum load P during coining, and reduction amount ΔP of maximum load P were measured for each case. In addition, the residual stress on the end face of the product 22 after coining was measured in both the plate thickness direction and plate width direction. The other measurement conditions were the same as in Example 1. Example 3 differs from Example 2 only in the value of the radius RCP of the counter punch 18. The measurement results are shown in Table 3 below and Figure 13.

As shown in FIG. 13(A), in Example 3 as well, the smaller the protrusion ratio D/L, the smaller the maximum load P. Also, as shown in FIG. 13(B), in Example 3, the effect of reducing residual stress is also obtained. For example, when the protrusion ratio D/L is 0.3 mm, the reduction amount Δσ of residual stress in the plate thickness direction is 540.74 MPa or more, and the reduction amount Δσ of residual stress in the plate width direction is 980.09 MPa or more. The effect of reducing residual stress in Example 3 is effective in actual shear processing, as in Examples 1 and 2.

Example 4
In Example 4, a 980 MPa-class steel plate was prepared as the workpiece 20, and piercing was performed using the shearing device 10 equipped with a counter punch 18 having a spherical head-shaped tip 18B as shown in FIG. 2(A). The thickness T of the steel plate was set to 4 mm, the clearance ratio was set to 10% of the thickness T, and the width L of the clearance 15 was set to 0.4 mm. The diameter W of the punched hole was set to 30 mm. The diameter-thickness ratio W/T was 7.5. The radius RCP of the counter punch 18 was set to 15 mm. The height H of the tip 18B was changed to vary the radius RS of the scrap 24 after coining.

Then, the protrusion width D, protrusion ratio D/L, maximum load P during coining, and reduction amount ΔP of maximum load P were measured for each case. In addition, the residual stress on the end surface of the product 22 after coining was measured in both the plate thickness direction and plate width direction. The other measurement conditions were the same as in Example 1. The measurement results are shown in Table 4 below and Figure 14.

As shown in FIG. 14(A), in Example 4 as well, the smaller the protrusion ratio D/L, the smaller the maximum load P. Also, as shown in FIG. 14(B), in Example 4, the effect of reducing residual stress is also obtained. For example, when the protrusion ratio D/L is 0.1 mm, the reduction amount Δσ of residual stress in the plate thickness direction is 489.29 MPa or more, and the reduction amount Δσ of residual stress in the plate width direction is 977.37 MPa or more. The effect of reducing residual stress in Example 4 is effective in actual shear processing, as in Examples 1 to 3.

Example 5
In Example 5, a 980 MPa-class steel plate was prepared as the workpiece 20, and piercing was performed using a shearing device 10 equipped with a counter punch 18 having a spherical tip 18B with a flat upper surface as shown in FIG. 2(B). The thickness T of the steel plate was set to 1.6 mm, the clearance ratio was set to 10% of the thickness T, and the width L of the clearance 15 was set to 0.16 mm. The diameter W of the punched hole was set to 30 mm. The diameter-thickness ratio W/T was 18.75. The radius RCP of the counter punch 18 was set to 15 mm. The height H of the tip 18B was changed to vary the radius RS of the scrap 24 after coining.

Then, the protrusion width D, protrusion ratio D/L, maximum load P during coining, and reduction amount ΔP of maximum load P were measured for each case. In addition, the residual stress of the end surface of the product 22 after coining was measured in both the plate thickness direction and plate width direction. The other measurement conditions were the same as in Example 1. The measurement results are shown in Table 5 below and Figure 15.

As shown in Figure 15 (A), in Example 5 as well, the smaller the protrusion ratio D/L, the smaller the maximum load P. Also, as shown in Figure 15 (B), in Example 5, the effect of reducing residual stress is also obtained. For example, when the protrusion ratio D/L is 0.3 mm, the reduction amount Δσ of residual stress in the plate thickness direction is 563.59 MPa or more, and the reduction amount Δσ of residual stress in the plate width direction is 982.28 MPa or more. The residual stress reduction effect of Example 5 is effective in actual shear processing, as in Examples 1 to 4.

Example 6
In Example 6, a 980 MPa-class steel plate was prepared as the workpiece 20, and piercing was performed using the shearing device 10 equipped with a counter punch 18 having a conical tip 18B as shown in FIG. 2C. The thickness T of the steel plate was set to 1.6 mm, the clearance ratio was set to 10% of the thickness T, and the width L of the clearance 15 was set to 0.16 mm. The diameter W of the punched hole was set to 30 mm. The diameter-thickness ratio W/T was 18.75. The radius RCP of the counter punch 18 was set to 15 mm. The height H of the tip 18B was changed to vary the radius RS of the scrap 24 after coining.

Then, the protrusion width D, protrusion ratio D/L, maximum load P during coining, and reduction amount ΔP of maximum load P were measured for each case. In addition, the residual stress of the end surface of the product 22 after coining was measured in both the plate thickness direction and plate width direction. The other measurement conditions were the same as in Example 1. The measurement results are shown in Table 6 below and Figure 16.

As shown in Figure 16 (A), in Example 6 as well, the smaller the protrusion ratio D/L, the smaller the maximum load P. Also, as shown in Figure 16 (B), in Example 6, the effect of reducing residual stress is also obtained. For example, when the protrusion ratio D/L is 0.3 mm, the reduction amount Δσ of residual stress in the plate thickness direction is 563.59 MPa or more, and the reduction amount Δσ of residual stress in the plate width direction is 993.28 MPa or more. The residual stress reduction effect of Example 6 is effective in actual shear processing, as in Examples 1 to 5.

(Example 7)
In Example 7, a 980 MPa-class steel plate was prepared as the workpiece 20, and trimming was performed using the shearing device 10 equipped with a counter punch 18 having a tapered tip 18B as shown in FIG. 9. The thickness T of the steel plate was set to 1.6 mm, the clearance ratio was set to 10% of the thickness T, and the width L of the clearance 15 was set to 0.16 mm. The diameter W of the punched hole was set to 30 mm. The diameter-thickness ratio W/T was 18.75. The radius RCP of the counter punch 18 was set to 15 mm. The height H of the tip 18B was changed to vary the radius RS of the scrap 24 after coining.

Then, the protrusion width D, protrusion ratio D/L, maximum load P during coining, and reduction amount ΔP of maximum load P were measured for each case. In addition, the residual stress on the end surface of the product 22 after coining was measured in both the plate thickness direction and plate width direction. The other measurement conditions were the same as in Example 1. The measurement results are shown in Table 7 below and Figure 17.

As shown in Figure 17 (A), in Example 7 as well, the smaller the protrusion ratio D/L, the smaller the maximum load P. Also, as shown in Figure 17 (B), in Example 7, the effect of reducing residual stress is also obtained. For example, when the protrusion ratio D/L is 0.3 mm, the reduction amount Δσ of residual stress in the plate thickness direction is 520.59 MPa or more, and the reduction amount Δσ of residual stress in the plate width direction is 1016.28 MPa or more. The residual stress reduction effect of Example 7 is effective in actual shear processing, as in Examples 1 to 6.

(Example 8)
In Example 8, a 300 MPa-class aluminum plate was prepared as the workpiece 20, and piercing was performed using a shearing device 10 equipped with a counter punch 18 having a spherical head-shaped tip 18B as shown in FIG. 2(A). The thickness T of the steel plate was set to 1.6 mm, the clearance ratio was set to 10% of the thickness T, and the width L of the clearance 15 was set to 0.16 mm. The diameter W of the punched hole was set to 30 mm. The diameter-thickness ratio W/T was 18.75. The radius RCP of the counter punch 18 was set to 15 mm. The height H of the tip 18B was changed to vary the radius RS of the scrap 24 after coining.

Then, the protrusion width D, protrusion ratio D/L, maximum load P during coining, and reduction amount ΔP of maximum load P were measured for each case. In addition, the residual stress on the end surface of the product 22 after coining was measured in both the plate thickness direction and plate width direction. The other measurement conditions were the same as in Example 1. The measurement results are shown in Table 8 below and Figure 18.

As shown in FIG. 18(A), in Example 8, the smaller the protrusion ratio D/L, the smaller the maximum load P. Also, as shown in FIG. 18(B), in Example 8, the effect of reducing residual stress is also obtained. For example, when the protrusion ratio D/L is 0.3 mm, the reduction amount Δσ of residual stress in the plate thickness direction is 210.24 MPa or more, and the reduction amount Δσ of residual stress in the plate width direction is 405.11 MPa or more. The effect of reducing residual stress in Example 8 is effective in actual shear processing, as in Examples 1 to 7. Also, it is understood that the present disclosure can be applied even if the workpiece material 20 is a metal material other than a high-strength steel plate, such as the aluminum plate in Example 8.

In this embodiment, as in Examples 1 to 8, it can be seen that the smaller the protrusion ratio D/L is, the more the maximum load generated in the shear processing device 10 can be reduced. In particular, it can be seen that when the protrusion ratio D/L is less than 0.8, the effect of reducing the load is enhanced. It can also be seen that by setting the protrusion ratio D/L to less than 0.6, the effect of reducing the load is further enhanced. It can also be seen that the residual stress on the end face of the product 22 is reduced.

However, as shown in Figures 11 to 18, when the protrusion ratio D/L is negative, i.e., when D<0, the effect of the protrusion ratio D/L on the load reduction effect becomes relatively small. Then, in order to control the amount of residual stress reduction Δσ, the diameter-thickness ratio W/T is adjusted. Next, using the following Examples 9 to 11, the relationship between the diameter-thickness ratio W/T and the amount of residual stress reduction Δσ, particularly when D<0, will be explained. Note that, although explanation will be omitted, it goes without saying that the load reduction effect is also obtained in Examples 9 to 11.

Example 9
In Example 9, a 980 MPa class steel plate was prepared as the workpiece 20, and piercing was performed using a shearing device 10 equipped with a counter punch 18 having a spherical head tip 18B as shown in Fig. 2(A). The clearance ratio was 10% of the thickness T of the steel plate. The thickness T of the workpiece 20 was set to 2 mm, and the diameter W of the punched hole was set to 30 mm so that the diameter-thickness ratio W/T = 15. The radius RCP of the counter punch 18 was set to 15 mm. Then, the residual stress in the thickness direction and the residual stress in the width direction were measured at the end face of the product 22 after coining.

Piercing was performed using a shearing device 10Z according to a comparative example that includes a counter punch 18 that does not have a tapered portion and whose tip has the same shape as its base. In the comparative example, coining was not performed and cutting was completed without punching. Other conditions in the comparative example were the same as those in Example 9. The difference between the residual stress in Example 9 and the residual stress in the comparative example was calculated as the residual stress reduction amount Δσ.

The measurement results are shown in Table 9 below. The reduction in residual stress Δσ in the thickness direction for Example 9 is represented by the data point marked with a white circle (○) on the far left in Figure 19. The reduction in residual stress Δσ in the width direction for Example 9 is represented by the data point marked with a black circle (●) on the far left in Figure 19.

Example 10
In Example 10, the thickness T of the workpiece 20 was set to 1 mm, and the diameter W of the punched hole was set to 60 mm so that the diameter-thickness ratio W/T was 60. The radius RCP of the counter punch 18 was set to 30 mm. The other conditions were the same as in Example 9. Then, the residual stress on the end face of the product 22 after coining was measured in both the thickness direction and the width direction.

The measurement results are shown in Table 10 below. The reduction in residual stress Δσ in the thickness direction for Example 10 is represented by the data point marked with a circle, second from the left in Figure 19. The reduction in residual stress Δσ in the width direction for Example 10 is represented by the data point marked with a ●, second from the left in Figure 19.

(Example 11)
In Example 11, the thickness T of the workpiece 20 was set to 0.5 mm, and the diameter W of the punched hole was set to 250 mm so that the diameter/thickness ratio W/T was 500. The radius RCP of the counter punch 18 was set to 125 mm. The other conditions were the same as in Example 9. Then, the residual stress on the end face of the product 22 after coining was measured in both the thickness direction and the width direction.

The measurement results are shown in Table 11 below. The reduction in residual stress Δσ in the thickness direction for Example 11 is represented by the data point marked with a circle on the far right in Figure 19. The reduction in residual stress Δσ in the width direction for Example 11 is represented by the data point marked with a ● on the far right in Figure 19, which partially overlaps with the data point marked with a circle.

As shown in Examples 9 to 11, in this embodiment, when D<0, the smaller the diameter-thickness ratio W/T, the greater the residual stress reduction amount Δσ that can be obtained. In particular, it can be seen that the effect of reducing residual stress is enhanced by having a diameter-thickness ratio W/T of less than 500. It can also be seen that the effect of reducing residual stress is further enhanced by having a diameter-thickness ratio W/T of less than 60.

(Action and Effect)
In this embodiment, when the counter punch 18 is moved toward the product 22 after shearing, the outer edge of the scrap 24 is bent and deformed during coining when the scrap 24 comes into contact with the end face of the product 22. The bending deformation absorbs the load generated between the product 22 and the scrap 24 during coining, reducing the burden on the shearing device 10 that receives the load. Therefore, there is no need to increase the capacity of a shock absorbing device such as a gas cushion.

In addition, in this embodiment, the counter punch 18 has a tip portion 18B that is smaller in diameter than the base portion 18A, and the scrap 24 is placed above the tip portion 18B. Therefore, compared to coining, in which a counter punch 18 is used in which the tip portion 18B has the same diameter as the base portion 18A and the upper surface of the tip portion 18B is flat, the outer edge of the scrap 24 can be smoothly folded and deformed to follow the shape of the reduced diameter tip portion 18B during coining.

In addition, in this embodiment, the tip portion 18B gradually reduces in diameter from the base portion 18A toward the workpiece 20, so the outer edge of the scrap 24 can be bent and deformed more smoothly. This further reduces the burden on the shear processing device 10.

In addition, in this embodiment, as shown in Figures 2(B), 2(D), 2(E), and 2(F), when the tip portion 18B has a flat upper surface, the flat upper surface increases the area of contact between the counter punch 18 and the punch 16, so that the scrap 24 can be more stably supported while the counter punch 18 is moving.

In addition, in this embodiment, as shown in FIG. 2(C), when the tip 18B is cone-shaped, the entire tip 18B is pointed upwards, so there is almost no area that cannot be used for bending deformation during coining, and bending can be performed reliably.

In addition, in this embodiment, a shearing device 10 capable of performing piercing is realized. This makes it possible to enhance the effect of reducing the coining load during piercing.

In addition, in this embodiment, after the outer edge of the scrap 24 is bent and deformed, the scrap 24 may remain in contact with the product 22. Even after the bending and deformation, coining continues while the protruding outer edge of the scrap 24 remains in contact with the product 22, which lengthens the coining time and enhances the effect of reducing residual stress caused by coining.

In addition, in this embodiment, if the contact state between the outer edge of the scrap 24 and the product 22 is maintained after bending deformation, the protrusion ratio D/L is set to less than 0.8, thereby enhancing the load reduction effect.

In addition, in this embodiment, if the contact state between the outer edge of the scrap 24 and the product 22 is maintained after bending deformation, the protrusion ratio D/L is set to less than 0.6, thereby further enhancing the load reduction effect.

In addition, in this embodiment, after the outer edge of the scrap 24 is bent and deformed to perform coining, the outer edge of the scrap 24 may be located inside the base 18A of the counter punch 18, and contact between the outer edge of the scrap 24 and the product 22 may be avoided. After bending and deformation, the counter punch 18 moves while maintaining a state in which the outer edge of the scrap 24 and the product 22 are not in contact with each other, so no further load is borne by the shearing device 10.

In addition, in this embodiment, if contact between the outer edge of the scrap 24 and the product 22 is avoided after bending deformation, the diameter-thickness ratio W/T is less than 500, thereby enhancing the effect of reducing residual stress.

In addition, in this embodiment, if contact between the outer edge of the scrap 24 and the product 22 is avoided after bending deformation, the diameter-thickness ratio W/T is less than 60, which further enhances the effect of reducing residual stress.

In addition, in this embodiment, since the workpiece 20 is a metal material, the effect of reducing the coining load during coining using a metal material can be enhanced.

In the modified example shown in Figures 9 and 10, similar to the present embodiment, when the counter punch 18 is moved toward the product 22 after shearing, the outer edge of the scrap 24 is bent and deformed during coining when the scrap 24 comes into contact with the end face of the product 22. The bending deformation absorbs the load generated between the product 22 and the scrap 24 during coining, reducing the burden on the shearing device 10 that receives the load. Therefore, there is no need to increase the capacity of a shock mitigation device such as a gas cushion.

In addition, in the modified example, a shearing device 10 capable of performing trimming is realized. This makes it possible to enhance the effect of reducing the coining load during trimming. Other effects of the shearing device 10 according to the modified example are the same as those of the present embodiment.

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

For example, the present disclosure can be achieved by partially combining the structures of the shearing devices shown in Figures 1 to 19. The present disclosure includes various embodiments not described above, and the technical scope of the present disclosure is determined only by the invention-specific matters of the claims that are appropriate from the above description.

10 Shearing device 12 Die 14 Holder 15 Clearance 16 Punch 18 Counter punch 18A Base 18B Tip 20 Workpiece 22 Product 24 Scrap A1 Position of inner surface of die A2 Position of outer surface of counter punch A3 Position of outer edge of scrap B Vertex B1 Boundary position C Reference line (central axis)
D: protruding width H: height L: clearance width RCP: counter punch radius (distance of the area of the reduced diameter portion)
RS: Radius of scrap T: Thickness W: Diameter of punched hole (diameter of scrap before bending deformation)

Claims (14)

Die and
A holder for clamping a workpiece between the holder and the die;
A punch disposed with a clearance between the punch and the die;
A counter punch disposed opposite the punch;
Using a shear processing device equipped with
the counter punch has a base and a tip portion provided on the base side of the workpiece and having a smaller diameter than the base portion, and the shapes of the base and the tip portion are rotationally symmetrical about a central axis of the counter punch,
The workpiece is sheared by the die and the punch to form a product, the product is supported between the die and the holder, and a portion separated from the workpiece by the shearing is placed on the tip of the counter punch as scrap;
With the scrap placed on the upper side, the counter punch is moved toward the product side, and the outer edge of the scrap is brought into contact with the end face of the supported product, thereby folding and deforming the outer edge of the scrap while coining.
Scrap coining methods. The diameter of the reduced portion of the tip portion is gradually reduced from the base side toward the workpiece side.
2. The scrap coining method of claim 1 . The tip has a flat upper surface and a region between the upper surface and the base that is tapered.
3. The scrap coining method of claim 2 . The tip is pointed upward.
3. The scrap coining method of claim 2 . The shearing is a piercing process.
The scrap coining method according to any one of claims 1 to 4 . The shearing is a trimming process.
The scrap coining method according to any one of claims 1 to 3 . After the outer edge of the scrap is bent and deformed,
The shape of the tip portion is made to match the shape of the center of the scrap that contacts the tip portion;
and continuing the coining after the folding deformation by moving the counter punch while maintaining an outer edge of the scrap protruding outside the base of the counter punch and in contact with the product.
The scrap coining method according to any one of claims 1 to 6 . The width of the clearance is L,
When the width of the outer edge of the scrap protruding outward from the base of the counter punch measured along the width direction of the clearance is D,
A protrusion ratio D/L of the protrusion width to the width of the clearance is less than 0.8;
8. The scrap coining method of claim 7 . The protrusion ratio D/L is less than 0.6;
9. The scrap coining method of claim 8 . After the outer edge of the scrap is bent and deformed,
moving the counter punch while maintaining an outer edge of the scrap inside a base of the counter punch and out of contact with the product;
The scrap coining method according to any one of claims 1 to 6 . The diameter of the scrap before coining is W,
When the thickness of the workpiece is T,
The diameter/thickness ratio W/T of the scrap to the thickness of the workpiece is less than 500;
11. The scrap coining method of claim 10 . The diameter/thickness ratio W/T is less than 60;
12. The scrap coining method of claim 11 . The workpiece is a metal material.
A scrap coining method according to any one of claims 1 to 12 . Die and
A holder for clamping a workpiece between the holder and the die;
A punch disposed with a clearance between the punch and the die;
a counter punch disposed opposite the punch and having a base and a tip provided on the workpiece side of the base and having a smaller diameter than the base;
Equipped with
The shapes of the base and the tip of the counter punch are rotationally symmetrical about the central axis of the counter punch.
Shear processing equipment.