Forging punches and dies

Abstract

To provide a forging punch in which a die is difficult to be destroyed.SOLUTION: A punch (20) is a forging punch used for thickening the center of a metal steel plate (30) by pressing the metal steel plate (30) disposed in a recess (13) formed in a die (10). The punch (20) is point-symmetrically shaped in section perpendicular to a pressing direction, and has a hollow part (40) that penetrates the punch (20) from an upper surface (22) to a lower surface (21).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a forging punch used to increase the thickness of a central portion of a metal steel plate. [Background technology]

[0002] There is known a technique for increasing the thickness of a desired region of an object by pressing the object placed in a die with a punch. For example, Patent Document 1 discloses a technique for increasing the thickness of a side wall portion of a press-molded cup-shaped product by pressing the side wall portion with a punch. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-317565 Summary of the Invention [Problem to be solved by the invention]

[0004] When a punch is used to press an object, a reaction stress is applied to the punch. This stress causes the punch to shrink in the pressing direction and expand in a direction perpendicular to the pressing direction. When the punch expands in a direction perpendicular to the pressing direction, the outer periphery of the punch comes into contact with the die and presses against the die. This results in the problem of the die being destroyed.

[0005] An object of one aspect of the present invention is to provide a forging punch in which the die is less likely to be broken. [Means for solving the problem]

[0006] In order to solve the above problems, a forging punch according to one embodiment of the present invention is a forging punch used to increase the thickness of a central portion of a metal steel plate by pressing the metal steel plate placed in a recess formed in a die, the forging punch having a point-symmetrical cross section perpendicular to the pressing direction, and a hollow portion extending along the pressing direction on a second surface opposite to a first surface that presses the metal steel plate.

[0007] In order to solve the above problems, a forging die according to one embodiment of the present invention comprises a die having a recess formed therein into which a metal steel plate is placed, and a forging punch used to increase the thickness of the central portion of the metal steel plate by pressing the metal steel plate placed in the recess, the forging punch having a hollow portion extending along the pressing direction on a second surface opposite to a first surface that presses the metal steel plate. [Effects of the Invention]

[0008] According to one aspect of the present invention, the die can be made less susceptible to breakage. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a die according to a first embodiment of the present invention, taken along a plane including the central axis of a punch. [Figure 2] FIG. [Figure 3] FIG. 3 is a perspective view showing a state in which the punch is partially cut away. [Figure 4] FIG. 5 is a cross-sectional view of a die according to a second embodiment of the present invention, cut along a plane including the central axis of the punch. [Figure 5] FIG. 10 is a top view of a punch as a modified example of the punch. [Figure 6] FIG. 10 is a diagram showing the amount of displacement of each region in shades of color in a simulation in which thickness-increasing processing is performed under predetermined conditions. [Figure 7] FIG. 10 is a diagram showing the amount of displacement of each region in shades of color in a simulation in which thickness-increasing processing is performed under predetermined conditions. [Figure 8] FIG. 10 is a diagram showing the magnitude of stress applied to each region by using different shades of color in a simulation assuming that thickness-increasing processing is performed under predetermined conditions. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Embodiment 1] An embodiment of the present invention will be described in detail below. Fig. 1 is a cross-sectional view of a die 1 in this embodiment, cut along a plane including the central axis of a punch 20. Fig. 2 is a perspective view of the punch 20. Fig. 3 is a perspective view showing a state in which a part of the punch 20 is cut away.

[0011] As shown in Fig. 1, the mold 1 includes a die 10 and a punch 20 (forging punch). The mold 1 is a mold for increasing the thickness of the central portion of a disk-shaped metal steel plate 30 placed on the die 10 by pressing the metal steel plate 30 with the punch 20.

[0012] 1, the die 10 has a side wall 11 and a support portion 12. The side wall 11 forms the outer periphery of the die 10 in a circular shape.

[0013] The support portion 12 supports the lower surface of the metal steel sheet 30 when the metal steel sheet 30 is placed on the die 10. The support portion 12 is provided so as to protrude inward from the lower end portion of the side wall 11. The inner surface 11A of the side wall 11 and the upper surface 12A of the support portion 12 are connected by a smooth curve such as an arc in a cross section when the die 10 is cut along a plane parallel to the pressing direction.

[0014] With the above-described configuration, the die 10 has a recess 13 formed by the inner surface 11A of the side wall 11 and the upper surface 12A of the support portion 12. The metal steel plate 30 is placed in the recess 13 when the metal steel plate 30 is subjected to thickness increasing processing.

[0015] The punch 20 is a member for pressing the metal steel sheet 30 placed in the recess 13 formed in the die 10 using a press machine (not shown). As shown in Figures 2 and 3, the punch 20 has a generally cylindrical shape that is long in the pressing direction (the vertical direction in Figures 1 to 3). The shape of the outer edge of the punch 20, when cut along a plane perpendicular to the pressing direction (in other words, a plane parallel to an upper surface 22 described below), is a point-symmetric shape with respect to a central axis 23 as the reference point of point symmetry.

[0016] The punch 20 has a lower surface 21 (first surface) that is the surface that presses the metal steel plate, and an upper surface 22 (second surface) that is the surface opposite to the lower surface 21 in the pressing direction.

[0017] The lower surface 21 has a contact portion 21A on the outer periphery, which is a region that comes into contact with the metal steel plate 30, and a central portion 21B located inside the contact portion 21A is recessed toward the inside of the punch 20. The contact portion 21A is formed so as to be parallel to a plane perpendicular to the pressing direction.

[0018] The punch 20 has a hollow portion 40 formed therein, penetrating the punch 20 from the upper surface 22 to the lower surface 21. The hollow portion 40 is located at a position where the central axis 23 of the cylindrical punch 20 is formed. In other words, the hollow portion 40 is located at the center of a cross section (point-symmetric shape) of the punch 20 when cut along a plane perpendicular to the pressing direction. The hollow portion 40 has a circular shape in a cross section perpendicular to the pressing direction, and the central axis 23 passes through the center of the circle. As shown in FIG. 1 , the hollow portion 40 is composed of a first region 41, a second region 42, and a third region 43. In the following description, the regions of the punch 20 where the first region 41, the second region 42, and the third region 43 are formed will be referred to as region A1, region A2, and region A3, respectively, as shown in FIG. 1 .

[0019] The first region 41 is a region extending to a position a predetermined distance away from the upper surface 22 in the pressing direction. The first region 41 may be formed so that its lower end is located at a position 50 to 70% of the total length of the punch 20 (i.e., the length in the pressing direction) from the upper surface 22 in the pressing direction.

[0020] The first region 41 has a constant diameter L1 in a cross section perpendicular to the pressing direction. The diameter L1 is preferably smaller than 0.15 times the punch diameter L0 (i.e., the diameter of the lower surface 21 of the punch 20). This is because if the diameter L1 is 0.15 times or more the punch diameter L0, the cross-sectional area of ​​the punch 20 that supports the load will decrease, which could result in damage to the punch 20. In other words, by making the diameter L1 of the first region 41 smaller than 0.15 times the punch diameter L0, the punch 20 can be made less susceptible to damage.

[0021] The second region 42 is a region that extends from a position slightly downward from the lower end of the first region 41 to the lower surface 21. The diameter L2 of the second region 42 is smaller than the diameter L1 of the first region 41. In other words, the diameter L1 of the first region 41 is larger than the diameter L2 of the second region 42.

[0022] The third region 43 is a region that connects the first region 41 and the second region 42. The third region 43 is formed so that its diameter gradually decreases in the pressing direction (downward). The angle θ shown in FIG. 1 is the angle between the surface that forms the first region 41 and the surface that forms the third region 43. The angle θ needs to be greater than or equal to 90° and less than 180° to connect the first region 41 and the second region 42. However, if the angle θ is too small, the surface that forms the third region 43 becomes nearly parallel to the contact portion 21A, and the load applied to that surface in the pressing direction during thickening processing becomes large. Therefore, the angle θ is preferably greater than or equal to 100°.

[0023] Next, the effects obtained when the die 1 has the above-described configuration and the die 1 is used to increase the thickness of the metal steel plate 30 will be described.

[0024] When the die 1 is used to increase the thickness of the central portion of the metal steel sheet 30, the lower surface 21 (more specifically, the contact portion 21A) of the punch 20 is used to press against the metal steel sheet 30 placed in the recess 13 of the die 10. As a result, material present in the area of ​​the metal steel sheet 30 pressed by the contact portion 21A attempts to move in a direction perpendicular to the pressing direction. At this time, because the outer periphery of the metal steel sheet 30 abuts against the side wall 11 of the die 10, material present in the area of ​​the metal steel sheet 30 pressed by the contact portion 21A cannot move in the outer periphery direction, but moves toward the center of the metal steel sheet 30. As a result, the central portion of the metal steel sheet 30 is increased in thickness.

[0025] When pressing the metal steel plate 30, a reaction stress is applied to the punch 20. This stress causes the punch 20 to contract in the pressing direction and expand in a direction perpendicular to the pressing direction. Hereinafter, the phenomenon of expansion in the direction perpendicular to the pressing direction will be referred to as diameter expansion. When diameter expansion occurs in the punch 20, the outer periphery of the region near the bottom surface 21 of the punch 20 comes into contact with the die 10 and presses against the die 10. As a result, a rotational moment is applied to the corner where the side wall 11 and the support portion 12 of the die 10 are connected, causing the corner to break.

[0026] To solve this problem, the punch 20 in this embodiment has a hollow portion 40. As described above, the hollow portion 40 has a cross section perpendicular to the pressing direction that is point-symmetric, penetrates from the upper surface 22 to the lower surface 21, and the diameter L1 of the first region 41 is larger than the diameters of the other regions (i.e., the diameter L2 of the second region 42 and the diameter of the third region 43).

[0027] The above configuration makes it easier for the diameter to expand in region A1, where first region 41 having a diameter L1 larger than the other regions is formed. Therefore, compared to a punch without hollow portion 40, the punch 20 of this embodiment can reduce the amount of diameter expansion in region A2, which is a region close to the lower surface 21. As a result, the stress applied to the die 10 by the diameter expansion of the punch 20 is reduced, and the rotational moment applied to the corners where the side wall 11 and support portion 12 of the die 10 are connected can be reduced. This makes it possible to make the die 10 less likely to break.

[0028] Since the larger the diameter of the hollow portion, the more likely it is that the diameter will expand, if the diameter L2 of the second region 42 and the diameter L1 of the first region 41 are not significantly different, the amount of diameter expansion in region A1 and the amount of diameter expansion in region A2 will not be significantly different. Therefore, in order to increase the amount of diameter expansion in region A1 and decrease the amount of diameter expansion in region A2, it is preferable that the diameter L2 of the second region 42 be smaller than 0.5 times the diameter L1 of the first region 41.

[0029] Furthermore, as described above, in the punch 20 of this embodiment, the lower end of the first region 41 is located at a position that is 50% or more of the total length of the punch 20 from the upper surface 22 in the pressing direction. This makes it easier for the stress that the punch 20 receives when pressing the metal steel sheet 30 to be transmitted to the region A1, making it easier to expand the diameter in the region A1.

[0030] Furthermore, if the first region 41 in the hollow portion 40 were formed up to a position close to the lower surface 21, the diameter would increase in the region close to the lower surface 21. In contrast, in this embodiment, as described above, the lower end of the first region 41 is located at a position that is 70% or less of the total length of the punch 20 from the upper surface 22 in the pressing direction (i.e., the length in the pressing direction). This makes it difficult for the diameter to increase in the region close to the lower surface 21.

[0031] Furthermore, when the central portion of the metal steel sheet 30 is thickened, if the thickening occurs on the punch 20 side, there is a risk that part of the thickened portion will intrude into the hollow portion 40 of the punch 20. For this reason, in the punch 20 of this embodiment, as described above, the contact portion 21A of the lower surface 21 is formed to be a plane perpendicular to the pressing direction. This makes it possible, when the punch 20 presses the metal steel sheet 30 and thickens part of the central portion of the metal steel sheet 30, to thicken the die 10 side and prevent thickening on the punch 20 side. As a result, the thickened portion of the hollow portion 40 does not intrude into the hollow portion 40.

[0032] [Embodiment 2] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0033] 4 is a cross-sectional view of the mold 1A of this embodiment taken along a plane including the central axis of the punch 20A. As shown in FIG. 4, the mold 1A has a hollow portion 40A instead of the hollow portion 40 of the mold 1 of the first embodiment.

[0034] The hollow portion 40A is formed on the upper surface 22 side of the punch 20A so as to extend along the pressing direction. The hollow portion 40A is formed so as to reach a position that is a predetermined distance from the upper surface 22 in the pressing direction. As described in the first embodiment, the predetermined distance position is preferably a position that is 50 to 70% of the total length of the punch 20A from the upper surface 22 in the pressing direction. The hollow portion 40A is provided at a position where the central axis 23 of the cylindrical punch 20A is formed.

[0035] The hollow portion 40A has a constant diameter L3 in a cross section perpendicular to the pressing direction. For the same reasons as those described in embodiment 1, the diameter L3 is preferably smaller than 0.15 times the punch diameter L0. In the following description, as shown in FIG. 4, the region of the punch 20A where the hollow portion 40A is formed will be referred to as region A4, and the other region will be referred to as region A5.

[0036] By providing the punch 20A having the above configuration, when stress is applied to the punch 20A as a reaction to the pressing force against the metal steel sheet 30, expansion of the diameter is more likely to occur in the region A4 where the hollow portion 40A is formed. Therefore, compared to a punch without the hollow portion 40A, the punch 20A of this embodiment can reduce the amount of expansion of the diameter in the region A5, which is a region close to the lower surface 21. As a result, the stress applied to the die 10 by the expansion of the diameter of the punch 20A is reduced, and the rotational moment applied to the corners where the side wall 11 and the support portion 12 of the die 10 are connected can be reduced. This makes it possible to make the die 10 less prone to breakage.

[0037] <Modification> Fig. 5 is a top view of a punch 20B as a modified example 50 of the punch 20A in the second embodiment. As shown in Fig. 5, the punch 20B in this modified example has a plurality of hollow portions 40A, as described in the second embodiment, formed therein. The plurality of hollow portions 40A are formed at equal intervals on the circumference of a circle centered on the central axis 23 of the punch 20B. By having the above configuration, similar to the punch 20A in the second embodiment, when stress is applied to the punch 20A as a reaction to the pressing force against the metal steel sheet 30, the punch 20B can easily expand in diameter in the region where the hollow portions 40A are formed.

[0038] The plurality of hollow portions 40A do not necessarily need to be formed at equal intervals on a circumference centered on the central axis 23 of the punch 20B. However, by forming the plurality of hollow portions 40A at equal intervals on a circumference centered on the central axis 23 of the punch 20B, the diameter of the punch 20B, which has the point-symmetric shape, can be expanded substantially uniformly around the outer periphery, thereby reducing the stress applied to the die 10 due to the expansion of the diameter of the punch 20B. In addition, in one aspect of the present invention, instead of the plurality of hollow portions 40A, a plurality of hollow portions 40 described in the first embodiment may be provided. In addition, although an example in which four hollow portions 40A are formed has been described in this modification, the number of hollow portions 40A is not limited to four and may be two, three, five or more.

[0039] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Example]

[0040] In this example, we will explain the results of simulating the thickening process of a metal steel plate using a die using the punch of Example 1 described in Embodiment 1 as an example, and a die using a punch of Comparative Example 1 in which no hollow portion is formed.

[0041] The simulation was performed assuming that the punch of Example 1 and the punch and die of Comparative Example 1 were made of SKH51 specified in JIS G 4403:2015, and that the metal steel plate to be thickened was made of ferritic stainless steel. The simulation was performed assuming that the punch of Example 1 had a shape similar to the punch 20 described in Embodiment 1. Specifically, the simulation was performed assuming that the punch of Example 1 and the punch, die, and metal steel plate of Comparative Example 1 had the following shapes.

[0042] (Shape of punch in Example 1) Punch diameter L0: 65 mm Area A1: Range from the upper surface 22 to a position 53% in the pressing direction Diameter L1 of the cross section perpendicular to the pressing direction of the first region 41 of the hollow portion 40: 0.06 times the punch diameter L0 Diameter L2 of the cross section perpendicular to the pressing direction of the second region 42 of the hollow portion 40: 0.3 times the diameter L1 Angle θ between the surface forming the first region 41 and the surface forming the third region 43: 135° (Punch shape of Comparative Example 1) The punch of Example 1 is a solid body with no hollow portion formed therein.

[0043] (Die shape) Inner diameter of side wall 11: 65.1 mm In a cross section of the die 10 cut along a plane parallel to the pressing direction, the connecting portion between the inner surface 11A of the side wall 11 and the upper surface 12A of the support portion 12 forms an arc shape with a radius of 1.5 mm.

[0044] (Shape of metal steel plate) Disk-shaped, 65mm diameter and 5mm thick.

[0045] The thickness-increasing process was simulated under the conditions that the shear friction coefficient between the punch and the metal steel plate, the shear friction coefficient between the die and the metal steel plate, and the shear friction coefficient between the punch and the die were set to 0.05, and the punch movement speed in the pressing direction was set to 1 mm / min.

[0046] (Simulation results) Figures 6 and 7 show the amount of displacement of each region in different shades of color when thickening processing is performed under the above conditions. Figure 8 shows the magnitude of stress applied to each region in different shades of color when thickening processing under the above conditions is simulated.

[0047] As shown in Figures 6 and 7, when the punch of Example 1 was used, the outward displacement of the region near the upper surface where the large-diameter hollow portion was formed was larger, and the outward displacement of the region near the lower surface where the small-diameter hollow portion was formed was smaller, compared to when the punch of Comparative Example 1 was used.

[0048] 8, when the punch of Example 1 was used, the stress applied to the corners of the die was smaller than when the punch of Comparative Example 1 was used. Specifically, when the punch of Comparative Example 1 was used, the stress applied to the corners of the die was 2500 MPa, whereas when the punch of Example 1 was used, the stress applied to the corners of the die was 2200 MPa. [Explanation of symbols]

[0049] 1. 1A mold 10 Die 13 Recess 20, 20A, 20B punches (forging punches) 21 Bottom surface (2nd surface) 22 Top surface (first surface) 30 Metal steel plate 40, 40A hollow part

Claims

1. A forging punch used to increase the thickness of a central portion of a metal steel plate by pressing the metal steel plate placed in a recess formed in a die, The cross section perpendicular to the pressing direction has a point-symmetric shape, a hollow portion extending along the pressing direction on a second surface opposite to a first surface that presses the metal steel plate; The hollow portion extends from the second surface to a position that is 50 to 70% of the total length of the forging punch in the pressing direction.

2. A forging punch used to increase the thickness of a central portion of a metal steel plate by pressing the metal steel plate placed in a recess formed in a die, The cross section perpendicular to the pressing direction has a point-symmetric shape, a hollow portion extending along the pressing direction on a second surface opposite to a first surface that presses the metal steel plate; The hollow portion is The forging punch is penetrated, a forging punch, wherein the diameter from the second surface to a predetermined position is larger than the diameter from the predetermined position to the first surface.

3. 3. The forging punch according to claim 1, wherein the hollow portion is provided at the center of the point-symmetric shape.

4. a die having a recess formed therein into which a metal steel plate is placed; a forging punch used to increase the thickness of a central portion of the metal steel plate by pressing the metal steel plate placed in the recess, the forging punch having a hollow portion extending along a pressing direction on a second surface that is a surface opposite to a first surface that is a surface that presses the metal steel plate, The hollow portion extends from the second surface to a position that is 50 to 70% of the total length of the forging punch in the pressing direction.

5. A die having a recess formed therein into which a metal steel plate is placed; a forging punch used to increase the thickness of a central portion of the metal steel plate by pressing the metal steel plate placed in the recess, the forging punch having a hollow portion extending along a pressing direction on a second surface that is a surface opposite to a first surface that is a surface that presses the metal steel plate, The hollow portion is The forging punch is penetrated, A mold in which the diameter from the second surface to a predetermined position is larger than the diameter from the predetermined position to the first surface.

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