Low-temperature forge welding method and low-temperature forge welding equipment

Abstract

To provide a pressure welding method and pressure welding device capable of improving the joining strength of two overlapping workpieces to be joined. [Solution] One aspect of the present disclosure is a pressing method in which a first workpiece (11) and a second workpiece (12) are overlapped and pressed from the first workpiece (11) side with a punch (24) to press the first workpiece (11) and the second workpiece (12) together, wherein the punch (24) has a convex portion (30) and a step portion (40) formed on the base portion (31) of the convex portion (30) and protruding outward beyond the convex portion (30) in a direction intersecting the movement direction of the punch (24), and when the first workpiece (11) and the second workpiece (12) are pressed together, the first workpiece (11) is pressed by the convex portion (30) and at the same time by the step portion (40), so that the portion of the first workpiece (11) that is pressed by the convex portion (30) and attempts to flow in a direction different from the second workpiece (12) is pressed by the step portion (40) in the direction toward the second workpiece (12) and caused to flow.

Description

[Technical Field]

[0001] The present disclosure relates to a method for pressing a first workpiece to be joined and a second workpiece to be joined together. low temperature forge welding Law, and low temperature forge welding Regarding the device. [Background technology]

[0002] Patent Documents 1 and 2 disclose a pressure welding method in which two workpieces are superimposed on one another and pressed from one of the workpieces with a punch. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-150416 [Patent Document 2] JP 2013-99776 A Summary of the Invention [Problem to be solved by the invention]

[0004] The two materials to be welded are overlapped and pressed together with a punch low temperature forge welding In this method, one of the materials to be welded is pressed with a punch, and as shown in Figure 30, oxide films and other materials adhering to the weld surfaces of the materials are crushed due to the increased surface area of ​​the weld surfaces, and the newly exposed surfaces then come into close contact, joining the two materials together.

[0005] However, when pressing from the side of one of the workpieces with a punch, a portion of the workpiece will occur that flows in a direction different from the direction toward the other workpiece (for example, upward or radially (left and right) when the punch is moved downward). When such a flowing portion occurs, even if the surface area of ​​the joining surfaces of the workpieces to be joined increases, the material of one workpiece will flow in a direction different from the direction toward the other workpiece, which will reduce the adhesion of the newly exposed surfaces at the joining surfaces, weakening the joining force at the joining surfaces of the two workpieces and potentially reducing the joining strength of the two workpieces to be joined.

[0006] In Patent Document 2, the area around the portion pressed by the punch's convex portion is pressed by the punch's shoulder, but this shoulder only contacts the workpieces to the extent that it does not hinder the flow of the materials. Furthermore, the punch completes its pressing operation while leaving a gap around the punch's convex portion. Therefore, the shoulder does not cause a portion of one workpiece that flows in a direction different from the other workpiece to flow toward the other workpiece. This reduces the adhesion of the newly exposed surfaces at the joining surfaces of the workpieces, weakening the joining force at the joining surfaces of the two workpieces and potentially reducing the joining strength between the two workpieces.

[0007] Therefore, the present disclosure has been made to solve the above-mentioned problems, and is capable of improving the joining strength of two overlapping workpieces to be joined. low temperature forge welding Law, and low temperature forge welding The present invention aims to provide a device. [Means for solving the problem]

[0008] In order to solve the above problems, one embodiment of the present disclosure provides a welding method for welding a first workpiece and a second workpiece together. Place it on the die A punch is used to press the first material to be joined together with the second material to be joined. low temperature forge welding In law, a portion of the die where the first workpiece to be joined and the second workpiece to be joined are placed one on top of the other is a flat surface;The punch has a convex portion and a step portion formed on the base side of the convex portion and projecting outward beyond the convex portion in a direction intersecting the moving direction of the punch, and when the first workpiece to be welded and the second workpiece to be welded are pressed together, the first workpiece to be welded is pressed by the convex portion and the step portion at the same time, so that a portion of the first workpiece to be welded that is pressed by the convex portion and tends to flow in a direction different from that of the second workpiece to be welded is pressed by the step portion in a direction toward the second workpiece to be welded, causing it to flow. Increasing the surface area of ​​the joining surface of the first material to be joined and the joining surface of the second material to be joined, thereby increasing the adhesion between the newly formed surfaces exposed on the joining surfaces; It is characterized by:

[0009] According to this aspect, the step portion can cause not only the portion of the first workpiece pressed by the convex portion of the punch to flow toward the second workpiece, but also the portion pressed by the convex portion of the punch to flow in a direction different from the direction toward the second workpiece. Therefore, the entire portion of the first workpiece pressed by the convex portion of the punch can be caused to flow toward the second workpiece. This increases the surface area of ​​the joining surfaces of the first workpiece and the second workpiece, improving the adhesion of the newly formed surfaces exposed at the joining surfaces. This increases the joining force between the joining surfaces of the first workpiece and the second workpiece, thereby improving the joining strength between the first workpiece and the second workpiece (i.e., the two workpieces).

[0010] In the above aspect, it is preferable that, when the punch is viewed from the tip end side, the outer shape of the convex portion is formed in a circular shape, and the outer shape of the stepped portion is also formed in a circular shape.

[0011] According to this aspect, the step portion can press the first material to be joined evenly in the circumferential direction around the protrusion, thereby more effectively improving the joining strength between the first material to be joined and the second material to be joined.

[0012] In the above aspect, it is preferable that, when the punch is viewed from the tip side, the outer shape of the convex portion is formed to be circular, and the outer shape of the stepped portion is formed to be quadrangular.

[0013] According to this aspect, the area of ​​the step portion changes in the circumferential direction around the protrusion, so that the step portion can press the first workpiece while causing the material of the first workpiece pressed against the step portion to flow, thereby more effectively improving the joining strength between the first workpiece and the second workpiece.

[0014] In the above aspect, it is preferable that the step portion is formed in a tapered shape that is inclined on the opposite side to the convex portion with respect to the moving direction of the punch.

[0015] According to this aspect, when the portion of the first material that is pressed by the convex portion and attempts to flow in a direction different from the second material is pressed by the step portion in the direction toward the second material to cause it to flow, the component force generated by the tapered step portion increases the surface pressure at the joining surfaces of the first material and the second material, thereby increasing the joining force at the joining surfaces of the first material and the second material, and improving the joining strength between the first material and the second material.

[0016] In the above aspect, it is preferable that the step portion is formed so as to be perpendicular to the moving direction of the punch.

[0017] According to this aspect, the force that presses the first material to be joined toward the second material to be joined by the step portion can be increased, thereby more effectively improving the joining strength between the first material to be joined and the second material to be joined.

[0018] In the above aspect, it is preferable that the surface of the convex portion is formed by a planar tip surface perpendicular to the moving direction of the punch, and a side surface formed from the edge of the tip surface toward the base side of the convex portion along the moving direction of the punch.

[0019] According to this aspect, the first and second workpieces are pressed together by applying pressure with the flat tip surface, and the surface pressure acting between the joining surfaces of the first and second workpieces can be increased, thereby more effectively improving the joining strength between the first and second workpieces.

[0020] In the above aspect, it is preferable that the surface of the convex portion is formed in a spherical shape or in a curved shape as a whole.

[0021] According to this aspect, when pressing with a punch from the first workpiece side, the joining surfaces of the first workpiece and the second workpiece are each changed from flat to spherical, thereby increasing their surface areas. This promotes the exposure of new surfaces (for example, by splitting an oxide film adhering to the joining surfaces) at the joining surfaces of the first workpiece and the second workpiece. This more effectively improves the joining strength between the first workpiece and the second workpiece.

[0022] In the above aspect, it is preferable that a plurality of the step portions are formed side by side in the moving direction of the punch.

[0023] According to this aspect, the portion that is pressed by the convex portion of the punch and attempts to flow in a direction different from the direction toward the second workpiece can be made to flow in multiple stages toward the second workpiece, thereby more effectively improving the joining strength between the first workpiece and the second workpiece.

[0024] Another aspect of the present disclosure that has been made to solve the above problem is a welding method in which a first workpiece and a second workpiece are overlapped with each other. Place it on the die A punch is used to press the first material to be joined together with the second material to be joined. low temperature forge welding In the apparatus, a portion of the die where the first workpiece to be joined and the second workpiece to be joined are placed one on top of the other is a flat surface;The punch has a convex portion and a step portion formed on the base side of the convex portion and projecting outward beyond the convex portion in a direction intersecting the moving direction of the punch, and when the first workpiece to be welded and the second workpiece to be welded are pressed together, the first workpiece to be welded is pressed by the convex portion and the step portion at the same time, so that a portion of the first workpiece to be welded that is pressed by the convex portion and tends to flow in a direction different from that of the second workpiece to be welded is pressed by the step portion in a direction toward the second workpiece to be welded, causing it to flow. Increasing the surface area of ​​the joining surface of the first material to be joined and the joining surface of the second material to be joined, thereby increasing the adhesion between the newly formed surfaces exposed on the joining surfaces; It is characterized by: [Effects of the Invention]

[0025] The present disclosure low temperature forge welding Law, and low temperature forge welding The device can improve the joining strength of two overlapping workpieces. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a schematic diagram showing a low-temperature forge welding apparatus according to an embodiment of the present invention; [Figure 2] FIG. 2 is a perspective view of the tip of the punch of the first embodiment. [Figure 3] FIG. 2 is a side view of the tip of the punch of the first embodiment. [Figure 4] FIG. 2 is a view of the punch of the first embodiment as seen from the tip. [Figure 5] FIG. 3 is a cross-sectional view showing the state where pressure is applied by the punch of the first embodiment. [Figure 6] FIG. 10 is a diagram summarizing the evaluation results of bonding strength. [Figure 7] FIG. 10 is a diagram showing evaluation results of conduction resistance. [Figure 8] FIG. 10 is a diagram showing evaluation results of peel strength. [Figure 9] FIG. 10 is a perspective view of the tip of a punch according to a first modified example of the first embodiment. [Figure 10] FIG. 10 is a side view of the tip of the punch of the first modified example of the first embodiment. [Figure 11] FIG. 10 is a side view of the tip of the punch of a second modified example of the first embodiment (more specifically, the modified example of FIG. 3). [Figure 12] 11 is a side view of the tip of the punch of a second modified example of the first embodiment (more specifically, the modified example of FIG. 10). FIG. [Figure 13] 10 is a cross-sectional view showing a state where a first workpiece to be joined and a second workpiece to be joined have concave and convex portions formed in advance and are pressed together by the punch of the first embodiment. FIG. [Figure 14] FIG. 10 is a perspective view of the tip of a punch according to a second embodiment. [Figure 15] FIG. 10 is a side view of the tip of the punch of the second embodiment. [Figure 16] FIG. 10 is a view of the punch of the second embodiment as seen from the tip. [Figure 17] FIG. 10 is a cross-sectional view showing the state where pressure is applied by the punch of the second embodiment. [Figure 18] FIG. 10 is a perspective view of the tip of a punch according to a first modified example of the second embodiment. [Figure 19] FIG. 10 is a side view of the tip of the punch of the first modified example of the second embodiment. [Figure 20] 16 is a side view of the tip of the punch of a second modified example of the second embodiment (more specifically, the modified example of FIG. 15). FIG. [Figure 21] FIG. 20 is a side view of the tip of the punch of a second modified example of the second embodiment (more specifically, the modified example of FIG. 19). [Figure 22] FIG. 10 is a perspective view of the tip of a punch according to a third embodiment. [Figure 23] FIG. 10 is a view of the punch of the third embodiment as seen from the tip. [Figure 24] FIG. 11 is a perspective view of the tip of a punch according to a first modified example of the third embodiment. [Figure 25] FIG. 10 is a view of a punch according to a second modified example of the third embodiment (more specifically, when the outer shape of the first stepped portion is circular), as viewed from the tip end. [Figure 26] FIG. 10 is a view of a punch according to a second modified example of the third embodiment (more specifically, when the outer shape of the first stepped portion is rectangular), as viewed from the tip end. [Figure 27] FIG. 10 is a cross-sectional view showing the state in which a first workpiece to be welded and a second workpiece to be welded are rods and are pressure-welded by the punches of the first to third embodiments. [Figure 28] FIG. 1 is a perspective view of a tip of a conventional punch. [Figure 29] FIG. 10 is a cross-sectional view showing pressure welding by a conventional punch. [Figure 30] FIG. 1 is an explanatory diagram illustrating low-temperature forge welding in which two workpieces are overlapped and pressed together with a punch. DETAILED DESCRIPTION OF THE INVENTION

[0027] The present disclosure low temperature forge welding Law, and low temperature forge welding This is an example of an embodiment of the device. low temperature forge welding Device 1 and this low temperature forge welding Device 1 was used low temperature forge welding Explain the law.

[0028] < low temperature forge welding Overview of the device> In this embodiment low temperature forge welding The apparatus 1 presses two workpieces (i.e., a first workpiece 11 and a second workpiece 12) together at room temperature. Low Warm forging Connection This is a device that low temperature forge welding As shown in FIG. 1, the device 1 has an elevator 21, a die mounting base 22, a die 23, a punch 24, a material pressing plate 25, and a spring 26.

[0029] A punch 24 is attached to the lifting section 21, which is raised and lowered by a drive device (not shown). A die 23 that receives a compressive load from the punch 24 is provided on the die mounting base 22. The first workpiece 11 and the second workpiece 12 are placed one on top of the other on the die 23.

[0030] The first material to be joined 11 is, for example, a copper plate (copper alloy plate), and the second material to be joined 12 is, for example, an aluminum plate (aluminum alloy plate).

[0031] The punch 24 is attached to the lifting unit 21 and moves up and down together with the lifting unit 21. The punch 24 is made of, for example, tool steel or cemented carbide. Details of the punch 24 will be described later.

[0032] The material pressing plate 25 is used to press the overlapping first and second workpieces 11 and 12 with the biasing force of the spring 26 before pressure welding, and to separate (peel off) the punch 24 from the bonded body of the first and second workpieces 11 and 12 after pressure welding.

[0033] Such a configuration low temperature forge welding The apparatus 1 pressure-welds a first workpiece 11 and a second workpiece 12 to be joined together as will be described below.

[0034] First, the first material to be joined 11 is placed on top of the second material to be joined 12 on the die 23. The joining surfaces of the first material to be joined 11 and the second material to be joined 12 are previously subjected to an oxide film removal treatment. Next, the first material to be joined 11 and the second material to be joined 12 thus overlapped are pressed down by a material pressing plate 25 using the biasing force of a spring 26.

[0035] Next, the punch 24 is lowered by the lifting section 21, and the punch 24 is pressed from the side of the first material to be joined 11, thereby pressing the first material to be joined 11 and the second material to be joined 12 together, thereby forming a pressed body of the first material to be joined 11 and the second material to be joined 12.

[0036] After the pressure welding, the punch 24 is raised by the lifting section 21 while the material pressing plate 25 is holding down the joined body of the first material to be joined 11 and the second material to be joined 12, so that the punch 24 is moved away from the joined body of the first material to be joined 11 and the second material to be joined 12.

[0037] <Punch Description> A conventional punch 124 is formed in a straight cylindrical shape with a generally constant outer diameter at the tip, as shown in Fig. 28. When such a conventional punch 124 is used to overlap a first material to be welded 11 and a second material to be welded 12 and press the first material to be welded 11 from the side of the first material to be welded 11, a portion of the first material to be welded 11 is generated that flows in a direction different from the direction toward the second material to be welded 12 (for example, upward or radially (left and right) when the punch 124 is moved downward), as shown by the arrow in Fig. 29.

[0038] In this case, even if the surface area of ​​the joining surfaces of the first material to be joined 11 and the second material to be joined 12 is increased by the pressing force of the punch 124, the adhesion of the newly exposed surfaces at the joining surfaces will decrease, weakening the joining force at the joining surfaces and potentially reducing the joining strength between the first material to be joined 11 and the second material to be joined 12. If the joining strength between the first material to be joined 11 and the second material to be joined 12 is reduced, the conduction resistance of the joined body of the first material to be joined 11 and the second material to be joined 12 will increase and the peel strength will decrease.

[0039] Therefore, in this embodiment, the shape of the punch 24 is devised to improve the joining strength between the first workpiece 11 and the second workpiece 12 to be joined.

[0040] (First Example) First, a first embodiment will be described. In this embodiment, as shown in Figures 2 and 3, the punch 24 includes a protrusion 30, a step portion 40, and a main portion 50 in this order from its tip end.

[0041] As shown in Fig. 2, the surface of the protrusion 30 is formed by a planar tip surface 32 perpendicular to the moving direction of the punch 24, a curved (R-shaped) edge 33 provided on the edge of the tip surface 32, and a side surface 34 formed from the edge 33 toward the base 31 along the moving direction of the punch 24. In this way, when the tip of the punch 24 is viewed from its side, the outer shape of the protrusion 30 is formed into a substantially U-shape that opens upward, as shown in Fig. 3. Note that the edge 33 may be a right-angled shape instead of a curved (R-shaped) shape.

[0042] As shown in Fig. 3, the step portion 40 is formed on the base portion 31 side of the protrusion 30, and is formed to protrude outward beyond the protrusion 30 in a direction intersecting the moving direction of the punch 24 (the left-right direction in Fig. 3). When the tip of the punch 24 is viewed from its side, the step portion 40 is formed in a tapered shape that is inclined toward the opposite side of the protrusion 30 with respect to the moving direction of the punch 24. The angle θ (i.e., the angle between the outer periphery of the trunk portion 50 and the step portion 40) is preferably as large as possible within 90°.

[0043] Also, as shown in Figure 4, when the punch 24 is viewed from its tip side, the outer shape of the convex portion 30 (i.e., the edge 33 of the tip surface 32) is formed in a circular shape, and the outer shape of the stepped portion 40 (i.e., the boundary portion 41 between the stepped portion 40 and the main portion 50) is also formed in a circular shape.

[0044] When the first material to be joined 11 and the second material to be joined 12 are pressure-welded using the punch 24 having such a shape, the first material to be joined 11 is pressed by the convex portion 30 and further pressed by the step portion 40, as shown in Fig. 5. As a result, the portion of the first material to be joined 11 that is pressed by the convex portion 30 as shown by arrow A and that attempts to flow in a direction different from the second material to be joined 12 (for example, upward or radially) is pressed by the step portion 40 in the direction toward the second material to be joined 12 as shown by arrow B, causing it to flow.

[0045] More specifically, in the first workpiece 11, there is a portion that is pressed by the tip surface 32 of the protrusion 30 of the punch 24 in a direction toward the second workpiece 12 and flows, while there is also a portion that is pressed by the edge 33 of the protrusion 30 and tries to flow in a direction different from the second workpiece 12, as shown by arrow A. Therefore, in order to prevent this portion that tries to flow in a direction different from the second workpiece 12 from continuing to flow in a direction different from the second workpiece 12, a step 40 is used to press it in a direction toward the second workpiece 12, as shown by arrow B, and make it flow.

[0046] Thus, according to this embodiment, the punch 24 is provided with a convex portion 30 and a step portion 40 that protrudes outward from the convex portion 30. When the first material to be joined 11 and the second material to be joined 12 are pressure-welded together, the first material to be joined 11 is pressed by the convex portion 30 and at the same time pressed by the step portion 40, so that the portion of the first material to be joined 11 that is pressed by the convex portion 30 and attempts to flow in a direction different from the second material to be joined 12 is pressed by the step portion 40 in the direction toward the second material to be joined 12, causing it to flow.

[0047] As a result, not only the portion of the first workpiece 11 that is pressed by the convex portion 30 of the punch 24 and flows in the direction toward the second workpiece 12, but also the portion that is pressed by the convex portion 30 of the punch 24 and tries to flow in a direction different from the direction toward the second workpiece 12 can be made to flow in the direction toward the second workpiece 12 by the step portion 40. low temperature forge welding Even if the liquidity is improved.

[0048] As a result, the entire portion of the first workpiece 11 pressed by the protrusion 30 of the punch 24 can be caused to flow in the direction toward the second workpiece 12. Therefore, the pressing of the punch 24 increases the surface area of ​​the joining surfaces of the first workpiece 11 and the second workpiece 12, thereby improving the adhesion of the newly formed surfaces exposed at the joining surfaces. This increases the joining force between the joining surfaces of the first workpiece 11 and the second workpiece 12, improving the joining strength between the first workpiece 11 and the second workpiece 12.

[0049] Here, the applicant conducted an evaluation to verify the bonding strength between the first material to be bonded 11 and the second material to be bonded 12. As a result of the evaluation, the results shown in Figures 6 to 8 were obtained. As shown in Figures 6 to 8, the punch 24 of the first embodiment had a lower electrical resistance and a higher peel strength than the conventional punch 124.

[0050] Specifically, the conduction resistance greatly exceeded the target value (0.030 mΩ) with the conventional punch 124, while the conduction resistance with the punch 24 of the first embodiment was reduced to the target value of about 0.030 mΩ. Also, the peel strength between the first and second materials 11 and 12 when pressed together with the punch 24 of the first embodiment was approximately three to five times greater than the peel strength between the first and second materials 11 and 12 when pressed together with the conventional punch 124.

[0051] Furthermore, according to this embodiment, when the punch 24 is viewed from its tip side (i.e., the tip surface 32 side), the outer shape of the convex portion 30 is formed in a circular shape, and the outer shape of the step portion 40 is also formed in a circular shape.

[0052] This allows the step portion 40 to press the first workpiece 11 evenly in the circumferential direction around the protrusion 30 of the punch 24. This more effectively improves the joining strength between the first workpiece 11 and the second workpiece 12.

[0053] Furthermore, according to this embodiment, the step portion 40 is formed in a tapered shape that is inclined toward the opposite side of the protrusion 30 with respect to the moving direction of the punch 24 when viewed from the side of the punch 24 .

[0054] As a result, when the portion of the first workpiece 11 that is pressed by the convex portion 30 of the punch 24 and attempts to flow in a direction different from the second workpiece 12 is pressed by the step portion 40 in the direction toward the second workpiece 12 to cause it to flow, the component force generated by the tapered step portion 40 spreads and acts on the first workpiece 11, thereby increasing the surface pressure at the joining surfaces of the first workpiece 11 and the second workpiece 12. Therefore, the joining force at the joining surfaces of the first workpiece 11 and the second workpiece 12 increases, and the joining strength between the first workpiece 11 and the second workpiece 12 improves.

[0055] Furthermore, according to this embodiment, the surface of the convex portion 30 is formed by a planar tip surface 32 perpendicular to the movement direction of the punch 24, and a side surface 34 formed from the edge 33 of the tip surface 32 toward the base 31 of the convex portion 30 along the movement direction of the punch 24.

[0056] As a result, by pressing the first material to be joined 11 with the flat tip surface 32 of the protrusion 30 of the punch 24, the first material to be joined 11 and the second material to be joined 12 are pressed together, and it is possible to increase the surface pressure acting between the joining surfaces of the first material to be joined 11 and the second material to be joined 12. Therefore, the joining strength between the first material to be joined 11 and the second material to be joined 12 is improved more effectively.

[0057] As a first modification, the surface of the protrusion 30 of the punch 24 may be formed in a spherical shape, as shown in Fig. 9. That is, when the tip of the punch 24 is viewed from its side, the outer shape of the protrusion 30 may be formed in an arc shape, as shown in Fig. 10. Note that the surface of the protrusion 30 does not have to be spherical, and may be formed in a curved shape as a whole.

[0058] As a result, when pressing with punch 24 from the first workpiece 11 side, the joining surfaces of first workpiece 11 and second workpiece 12 can be changed from flat to spherical or curved, thereby increasing their surface areas. This can promote the exposure of new surfaces (for example, by splitting an oxide film attached to the joining surfaces) at the joining surfaces of first workpiece 11 and second workpiece 12. This therefore more effectively improves the joining strength between first workpiece 11 and second workpiece 12.

[0059] Furthermore, as a second variant, as shown in Figures 11 and 12, when the tip of the punch 24 is viewed from its side, multiple (i.e., two) step portions 40 (i.e., a first step portion 40A and a second step portion 40B) may be formed side by side in the movement direction of the punch 24, with an intermediate portion 60 sandwiched between them.

[0060] In this case, the angle θ1 of the first step portion 40A and the angle θ2 of the second step portion 40B are preferably as large as possible within 90°. Note that the angles θ1 and θ2 may be different from each other. Furthermore, three or more step portions 40 may be formed side by side in the moving direction of the punch 24.

[0061] This allows the portion that is pressed by the convex portion 30 of the punch 24 and attempts to flow in a direction different from the direction toward the second workpiece 12 to flow in multiple stages in the direction toward the second workpiece 12. Therefore, the joining strength between the first workpiece 11 and the second workpiece 12 is improved more effectively.

[0062] 13, a concave-convex portion 70 may be formed in advance on the first material to be joined 11 and the second material to be joined 12. As a result, when pressing with a punch 24 from the first material to be joined 11 side, the second material to be joined 12 is constrained to the first material to be joined 11 by the concave-convex portion 70, so that the pressure on the joining surfaces of the first material to be joined 11 and the second material to be joined 12 increases, and the joining strength between the first material to be joined 11 and the second material to be joined 12 improves.

[0063] (Second Example) Next, a second embodiment will be described, focusing on the differences from the first embodiment, and omitting a description of the commonalities with the first embodiment.

[0064] In this embodiment, as shown in Fig. 14, the step portion 40 of the punch 24 is formed so as to be perpendicular to the moving direction of the punch 24. That is, as shown in Fig. 15, when the tip of the punch 24 is viewed from its side, the step portion 40 is formed linearly in a direction perpendicular to the moving direction of the punch 24 (the left-right direction in the figure).

[0065] Also, as shown in Figure 16, when the punch 24 is viewed from its tip side, the outer shape of the convex portion 30 (i.e., the shape of the base portion 31) is formed in a circular shape, and the outer shape of the step portion 40 (i.e., the shape of the boundary portion 41 between the step portion 40 and the main portion 50) is also formed in a circular shape.

[0066] When the first material to be joined 11 and the second material to be joined 12 are pressed together using the punch 24 having such a shape, the first material to be joined 11 is pressed by the protrusion 30 and at the same time by the step portion 40, as shown in Fig. 17. Then, in Fig. 17, the portion that is pressed by the protrusion 30 and tries to flow in a direction different from the second material to be joined 12 (for example, upward or radially), as shown by arrow C, can be pressed by the step portion 40 in the direction toward the second material to be joined 12, as shown by arrow D, and can be made to flow.

[0067] More specifically, in the first workpiece 11, there is a portion that is pressed by the tip surface 32 of the protrusion 30 of the punch 24 in a direction toward the second workpiece 12 and flows, while there is also a portion that is pressed by the protrusion 30 and tries to flow in a direction different from the second workpiece 12, as shown by arrow C. Therefore, the step portion 40 can press this portion that tries to flow in a direction different from the second workpiece 12 in a direction toward the second workpiece 12, as shown by arrow D, and cause it to flow.

[0068] In this embodiment, the step portion 40 of the punch 24 is formed so as to be perpendicular to the moving direction of the punch 24. Therefore, it is possible to increase the force with which the step portion 40 presses the first material 11 toward the second material 12, thereby more effectively improving the joining strength between the first material 11 and the second material 12.

[0069] Furthermore, as shown in FIGS. 6 to 8, the punch 24 of the second embodiment also has a smaller electrical resistance and a greater peel strength than the conventional punch 124.

[0070] 18 and 19, as a first modification, the surface of the protrusion 30 of the punch 24 may be formed into a spherical shape. Note that the surface of the protrusion 30 does not have to be spherical, and may be formed into a curved shape as a whole.

[0071] Furthermore, as a second variant, as shown in Figures 20 and 21, when the tip of the punch 24 is viewed from its side, two step portions 40 (i.e., a first step portion 40A and a second step portion 40B) may be formed side by side in the movement direction of the punch 24 (the up and down direction in the figure), sandwiching an intermediate portion 60 therebetween.

[0072] (Third Example) Next, a third embodiment will be described, but differences from the first and second embodiments will be described, and descriptions of commonalities with the first and second embodiments will be omitted.

[0073] In this embodiment, as shown in Fig. 22, the main part 50 of the punch 24 is formed in the shape of a rectangular parallelepiped, and the outer shape of a cross section perpendicular to the direction of movement of the punch 24 is formed in a quadrangle. In this way, when the punch 24 is viewed from its tip side, as shown in Fig. 23, the outer shape of the protrusion 30 is formed in a circular shape, while the outer shape of the step portion 40 is formed in a quadrangle. Note that the outer shape of the step portion 40 may be formed in a polygonal shape other than a quadrangle.

[0074] When a punch 24 having such a shape is used to press the first workpiece 11 and the second workpiece 12 together, as shown in Figure 17 above, the part that is pressed by the convex portion 30 as shown by arrow C and attempts to flow in a direction different from the second workpiece 12 is pressed by the step portion 40 in the direction toward the second workpiece 12 as shown by arrow D, causing it to flow.

[0075] At this time, the portion of the first workpiece 11 pressed by the punch 24 flows as shown by the arrows in Fig. 23. That is, the material of the first workpiece 11 flows from the larger-area portion of the step portion 40 to the smaller-area portion, while the first workpiece 11 is pressed by the step portion 40. This provides fluidity to the material of the first workpiece 11, so that the portion of the first workpiece 11 that is pressed by the protrusion 30 and attempts to flow in a direction different from that of the second workpiece 12 can be smoothly pressed by the step portion 40 in the direction toward the second workpiece 12 and made to flow. This more effectively improves the joining strength between the first workpiece 11 and the second workpiece 12.

[0076] Furthermore, as shown in FIGS. 6 to 8, the punch 24 of the third embodiment also has a smaller electrical resistance and a greater peel strength than the conventional punch 124.

[0077] As a first modification, the surface of the protrusion 30 of the punch 24 may be formed into a spherical shape, as shown in Fig. 24. Note that the surface of the protrusion 30 does not have to be spherical, and may be formed into a curved shape as a whole.

[0078] 20 and 21, when the tip of the punch 24 is viewed from its side, two step portions 40 (i.e., a first step portion 40A and a second step portion 40B) may be formed side by side in the movement direction of the punch 24 (the up and down direction in the figure), sandwiching an intermediate portion 60 therebetween.

[0079] 25, the first step portion 40A, which is the first step counting from the protrusion 30 side, may have a circular outer shape, while the second step portion 40B, which is the second step counting from the protrusion 30 side, may have a rectangular outer shape. Alternatively, as shown in FIG. 26, the first step portion 40A may have a rectangular outer shape, and the second step portion 40B may also have a rectangular outer shape.

[0080] It should be noted that the above-described embodiments are merely examples and do not limit the present disclosure in any way. It goes without saying that various improvements and modifications are possible within the scope of the gist of the present disclosure.

[0081] For example, as shown in FIG. 27, the first material to be joined 11 and the second material to be joined 12 may be rod-shaped joining materials, and a portion of the first material to be joined 11 that is pressed by the convex portion 30 and tends to flow in a direction different from the second material to be joined 12 can be pressed by the step portion 40 in a direction toward the second material to be joined 12, causing it to flow.

[0082] In the third embodiment, the step portion 40 may be formed in a tapered shape that is inclined toward the opposite side of the protrusion 30 with respect to the moving direction of the punch 24 when viewed from the side of the punch 24 .

[0083] Furthermore, the pressure-welded body obtained by pressure-welding the first material to be joined 11 and the second material to be joined 12 can be used for various purposes, such as a battery terminal (for example, a negative terminal of a secondary battery).

[0084] Furthermore, there are no particular limitations on the materials of first material to be joined 11 and second material to be joined 12. For example, the materials of first material to be joined 11 and second material to be joined 12 may be pure aluminum (A1000 series), aluminum alloys (e.g., A2000 series, A5000 series, 6000 series), pure iron, iron alloys (e.g., S10C to 45C, SUS304, SUS316, SUS430), pure titanium (e.g., TB340C), titanium alloys, pure copper (e.g., oxygen-free copper), copper alloys, or other metals.

[0085] The combination of materials for the first and second workpieces 11 and 12 may be a combination of the same metals, such as aluminum alloys or iron alloys, or a combination of different metals, such as pure iron and an iron alloy (e.g., SUS304, SU316, SUS430, etc.), iron-based metals (pure iron or iron alloys) and aluminum-based metals (pure aluminum or aluminum alloys), titanium-based metals (pure titanium or titanium alloys) and iron-based metals (pure iron or iron alloys), titanium-based metals (pure titanium or titanium alloys) and aluminum-based metals (pure aluminum or aluminum alloys), copper-based metals (pure copper or copper alloys) and iron-based metals (pure iron or iron alloys), or copper-based metals (pure copper or copper alloys) and aluminum-based metals (pure aluminum or aluminum alloys). [Explanation of symbols]

[0086] 1 low temperature forge welding Device 11 First material to be joined 12 Second material to be joined 21 Lifting section 22 Die mounting base 23 Die 24 Punch 25 Material holding plate 26 Spring 30 Convex part 31 Base 32 Tip surface 33 Edge 34 Side 40 Step 40A First step 40B Second step 41 Boundary 50 Core Staff 60 Middle 70 Uneven part 124 Punch θ angle θ1 angle θ2 angle A arrow B arrow C arrow D arrow

Claims

1. A low-temperature forge welding method in which a first workpiece and a second workpiece are placed on a die in an overlapping relationship, and pressed from the first workpiece side with a punch to pressure-weld the first workpiece and the second workpiece together, a portion of the die where the first workpiece to be joined and the second workpiece to be joined are placed one on top of the other is a flat surface, the punch includes a protrusion and a step portion formed on a base side of the protrusion and projecting outward beyond the protrusion in a direction intersecting with a moving direction of the punch, When the first workpiece and the second workpiece are pressure-welded together, The first workpiece is pressed by the protrusion and the stepped portion at the same time, a portion of the first workpiece that is pressed by the convex portion and tends to flow in a direction different from that of the second workpiece is pressed by the step portion in a direction toward the second workpiece, causing the first workpiece to flow; Enlarging the surface areas of the joining surfaces of the first and second workpieces to increase the adhesion between the newly formed surfaces exposed at the joining surfaces; A low-temperature forge welding method characterized by:

2. The low-temperature forge welding method of claim 1, When the punch is viewed from its tip side, The outer shape of the convex portion is formed in a circular shape, and the stepped portion has a circular outer shape. A low-temperature forge welding method characterized by:

3. The low-temperature forge welding method of claim 1, When the punch is viewed from its tip side, The outer shape of the convex portion is formed in a circular shape, and the stepped portion has a rectangular outer shape. A low-temperature forge welding method characterized by:

4. 4. The low-temperature forge welding method according to claim 1, the step portion is formed in a tapered shape inclined toward the opposite side of the protrusion with respect to the moving direction of the punch; A low-temperature forge welding method characterized by:

5. 4. The low-temperature forge welding method according to claim 1, the step portion is formed perpendicular to the moving direction of the punch; A low-temperature forge welding method characterized by:

6. 4. The low-temperature forge welding method according to claim 1, The surface of the convex portion is a flat tip surface perpendicular to the moving direction of the punch; a side surface formed from an edge of the tip surface toward a base side of the protrusion along the moving direction of the punch; It is formed by A low-temperature forge welding method characterized by:

7. 4. The low-temperature forge welding method according to claim 1, The surface of the convex portion is formed in a spherical shape or a curved shape as a whole; A low-temperature forge welding method characterized by:

8. 4. The low-temperature forge welding method according to claim 1, a plurality of the step portions are formed side by side in the moving direction of the punch; A low-temperature forge welding method characterized by:

9. 1. A low-temperature forge welding apparatus in which a first workpiece to be welded and a second workpiece to be welded are placed one on top of the other on a die, and a punch is used to press the first workpiece to be welded together, a portion of the die where the first workpiece to be joined and the second workpiece to be joined are placed one on top of the other is a flat surface, the punch includes a protrusion and a step portion formed on a base side of the protrusion and projecting outward beyond the protrusion in a direction intersecting with a moving direction of the punch, When the first workpiece and the second workpiece are pressure-welded together, The first workpiece is pressed by the protrusion and the stepped portion at the same time, a portion of the first workpiece that is pressed by the convex portion and tends to flow in a direction different from that of the second workpiece is pressed by the step portion in a direction toward the second workpiece, causing the first workpiece to flow; Enlarging the surface areas of the joining surfaces of the first and second workpieces to increase the adhesion between the newly formed surfaces exposed at the joining surfaces; Low temperature forge welding equipment characterized by:

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