Metal plate connecting method

Abstract

To provide a metal plate connecting method which can rigidly and accurately connect even metal plates that are made from different kinds of materials from each other.SOLUTION: A metal plate connecting method of the present invention includes: forming a through-hole at the same locations on a plurality of metal plates vertically stacked on each other; inserting into the through-hole a plug having a cross-sectional shape approximately equal to the cross-sectional shape of the through-hole and having a higher hardness than both of the metal plates; pressurizing the periphery of the plug at least on the surfaces of outermost two metal plates of the stacked metal plates and causing the metal plates to plastically deform in a surface direction of the plug to apply a fastening stress to the plug, thereby connecting the plurality of metal plates to each other through the plug.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for joining metal plates that can firmly join even dissimilar materials. [Background technology]

[0002] Metal plates are used in many fields, and many types of joining methods are known. Representative joining methods include bolts and nuts, mechanical clinching, riveting, etc., as disclosed in Patent Document 1, for example. In the case of bolts and nuts, there is a problem that two types of joining materials are required and joining takes time. On the other hand, in the case of mechanical clinching and riveting, a hard punch or rivet is pressed into a soft material to form an anchor, but the amount of anchor is small, and gaps occur between the soft material and the rivet, and the fastening force between the soft material and the rivet is weak, resulting in low strength.

[0003] Patent Document 2 discloses a joining structure and joining device for metal members that utilizes plastic flow joining. This technology describes a method and device for joining a first metal member having an annular portion to a second metal member having an axial portion using a restraining ring. By utilizing plastic flow joining, metal joining with high strength and high precision can be performed, but this technology cannot be directly applied to joining metal plate members. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-130238 A [Patent Document 2] Republished Patent No. 2011 / 118219 Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above problems, an object of the present invention is to provide a metal plate joining method capable of joining metal plates made of dissimilar materials with high strength and high precision. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the method for joining metal plates according to the present invention is characterized in that a through hole is formed at the same location of multiple metal plates stacked one above the other, a plug having a cross-sectional shape approximately equal to the cross-sectional shape of the through hole and having a hardness greater than any of the metal plates is inserted into the through hole, and pressure is applied around the plug on the surfaces of at least two outermost metal plates of the stacked metal plates to plastically deform each metal plate in the surface direction of the plug, thereby applying a tightening stress to the plug, thereby joining the multiple metal plates through the plug.

[0007] It is preferable to insert the plug into a through hole in the first metal plate, apply pressure to the periphery of the plug on the first metal plate to bond the first metal plate and the plug, and then insert the plug bonded to the first metal plate into the through hole of the second metal plate, and then apply pressure to the periphery of the plug on the second metal plate to bond the second metal plate and the plug, thereby bonding the first and second metal plates. In addition, the multiple metal plates may be first, second, and third metal plates, and the first metal plate and the plug may be joined by inserting the plug into a through hole in the first metal plate and applying pressure to the periphery of the plug on the first metal plate, then fitting the plug coupled to the first metal plate into a through hole in the second metal plate, and then applying pressure to the periphery of the plug on the second metal plate to join the second metal plate and the plug, and further fitting the plug coupled to the first and second metal plates into a through hole in the third metal plate, and then applying pressure to the periphery of the plug on the third metal plate to join the third metal plate and the plug, thereby ultimately joining the first, second, and third metal plates.

[0008] On the other hand, the first and second metal plates can be joined by stacking the first metal plate and the second metal plate to form a laminate, aligning the positions of the through holes of each plate, inserting the plug, and simultaneously applying pressure from both sides around the plug on the surface of the laminate. Also, the first, second, and third metal plates can be joined by stacking the first, second, and third metal plates to form a laminate by aligning the positions of the through holes of each plate, inserting the plug into the through hole, and simultaneously applying pressure from both sides around the plug on the surface of the laminate.

[0009] It is preferable that the through hole has a circular cross-sectional shape and that the plug also has a circular cross-sectional shape, and it is further preferable that a plurality of circumferential grooves are provided around the periphery of the plug. It is also preferable that the grooves are formed near the pressure side surface of each of the metal plates. Effect of the Invention

[0010] In the metal plate joining method according to the present invention, the surface of the soft material is pressed with the tip of the punch and pushed in, so that the soft plate material flows into the groove provided in the plug of the hard material, and the resistance of the shear deformation of the material can be used to firmly join the two plates. In addition, the soft plate material is pressed against the smooth part of the plug with high pressure, and the fastening pressure (residual stress) is maintained even after the pressure of the punch is removed, so the friction resistance of the fastening can also be used. On the other hand, since the spatial volume of the groove that causes the plate material to flow is small, the punch stroke is usually small, about 1 mm or less, and there is no relative movement between the plate material and the plug, so the precision of the joined product is high. Furthermore, since the plastic flow of the joint is a deformation under compressive stress, there is a low possibility of defects such as cracks occurring in the plate material. For this reason, it is possible to use work-hardening materials or tempered materials that have poor ductility as the soft material. It should be noted that, although it is common to mechanical joining methods, joining is possible even if the materials of the laminated plates are different materials. [Brief description of the drawings]

[0011] [Figure 1]1 is a partial cross-sectional view of metal plates bonded by an embodiment of a metal plate bonding method according to the present invention. [Diagram 2] 2A and 2B are process diagrams illustrating an embodiment of the method for joining metal plates shown in Fig. 1. Fig. 2A is a partial cross-sectional view showing a state immediately after joining a first metal plate, and Fig. 2B is a partial cross-sectional view showing a state immediately after joining a second metal plate. [Diagram 3] FIG. 4 is a diagram showing the relationship between the displacement of a punch and the load applied to the punch in the metal plate joining method according to the present invention. [Figure 4] 3 is a diagram showing the load (bonding strength) when a plug is pulled out and returned to the metal plates bonded by the metal plate bonding method according to the present invention shown in FIG. 2. FIG. [Diagram 5] 4 is a cross-sectional view showing the state of a through hole formed by conventional shearing of a first metal plate. FIG. [Figure 6] FIG. 1 is a partial cross-sectional view showing the joining of a plug and a metal plate in a conventional shear hole. [Figure 7] 5A to 5C are process explanatory views relating to a second embodiment of the metal plate bonding method according to the present invention. [Figure 8] 8 is a partial cross-sectional view showing a state of the metal plates joined by the method shown in FIG. 7. [Figure 9] FIG. 1 is a diagram showing the variety of plug shapes. [Figure 10] 5A to 5C are process explanatory views relating to a third embodiment of the metal plate bonding method according to the present invention. [Figure 11] 7A to 7C are process explanatory diagrams relating to a fourth embodiment of the metal plate bonding method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Fig. 1 shows a partial cross-sectional view of metal plates joined by a first embodiment of the metal plate joining method of the present invention. A second metal plate 2 is laminated on a first metal plate 1, and the two metal plates are joined by plugs 3 inserted into through holes 101 and 102 that pass through the respective metal plates.

[0013] The manufacturing process of this embodiment will be described. Fig. 2(a) shows the first step, in which the plug 3 is inserted into the through hole 101 provided in the first metal plate 1, and the surface of the first metal plate 1 around the plug 3 is pressed from above by the punch 4. This action forms a recess as a punch mark 41 on the surface of the first metal plate 1, and the material of the first metal plate 1 flows around the plug groove 31 formed on the surface of the plug 3 to press the plug 3, and the first metal plate 1 is bonded to the plug 3. Fig. 2(a) shows the state immediately after the punch 4 is returned after pressing. In this embodiment, a cylindrical heat-treated steel (HRC30) with a diameter of 10 mm was used as the plug 3, and a steel plate (SPCE) with a plate thickness of 1.4 mm was used as the first metal plate 1.

[0014] 2(b) shows the second step, in which the plug 3 on the first metal plate 1 is inserted into the through hole 201 provided in the second metal plate 2, and the surface of the second metal plate 2 around the plug 3 is pressed again by the punch 4. This action forms a recess as a punch mark 42 on the surface of the second metal plate 2, and the material of the second metal plate 2 flows around the plug groove 32 formed on the surface of the plug 3, pressing the plug 3, and the second metal plate 2 is joined to the plug 3. In this embodiment, an aluminum plate (A5052-O) with a thickness of 2 mm was used as the second metal plate 2. Through this series of actions, the first metal plate 1 and the second metal plate 2 are joined via the plug 3.

[0015] The relationship between punch load (joining load) and punch displacement (stroke) in the above process is shown in Figure 3. The curve labeled "SPCE" shows the relationship between the two when joining a steel plate (SPCE) and a plug, while the curve labeled "A5052 laminated to SPCE" shows the relationship between load and displacement when an aluminum plate (A5052-O) is further laminated and joined. Because the aluminum plate (A5052-O) has low deformation resistance, it can be seen that the joining load is smaller than that of the steel plate (SPCE).

[0016] Figure 4 shows the relationship between the load (bonding strength) and displacement when the plug 3 is removed from the steel plate (SPCE) which is the first metal plate 1 after the first process, and the relationship between the load (bonding strength) and displacement when the plug 3 is removed from the combined body of the first and second metal plates (A5052-O) after the second process. The bond load in the second process was small, but the strength of the combined body was high because an amount equivalent to the bond strength of the A5052-O material was added.

[0017] The feature of the metal plate joining method according to the present invention as shown in the above embodiment is that the soft plate material flows into the plug groove provided in the hard plug by pressing and pushing the soft material surface with the punch blade, and the resistance of the shear deformation of the material is utilized to firmly join the two plates. In addition, the soft plate material is pressed against the smooth part of the plug with high pressure, and the fastening pressure (residual stress) is retained even after the punch pressure is removed, and the frictional resistance of the fastening is added. In addition, since the spatial volume of the plug groove that causes the plate material to flow is small, the punch stroke is usually small, about 1 mm or less, and there is no relative movement between the plate material and the plug, so the precision of the joined product is high. Furthermore, since the plastic flow of the joint is a deformation under compressive stress, there is a low possibility of defects such as cracks occurring in the plate material. For this reason, it is possible to use work-hardening materials or tempered materials that have poor ductility as the soft material. In addition, as is common to mechanical joining methods, joining is possible even if the laminated plate materials are made of different materials.

[0018] Here, we will explain the shape of the through holes in the metal plates used for joining. The holes can be formed by cutting with a drill or by laser processing or electric discharge processing, and the direction of the holes is generally perpendicular to the metal plate surface. However, press processing is often used for mass-produced products. In press processing, the size of the hole entrance is almost equal to the punch diameter, and the size of the hole exit side (die side) is almost equal to the die dimension. On the other hand, the hole in the die is larger than the punch diameter by the amount of clearance. In precision shear processing, the clearance is small, so the hole is almost perpendicular to the plate surface. On the other hand, in the case of conventional shear, the shear surface 11 close to the punch side surface is almost perpendicular to the plate surface, but as it approaches the die side, a fracture surface 12 is generated and the hole surface is inclined, resulting in a conical hole with a hole diameter dimension larger by the clearance, that is, about 10% of the plate thickness. This state is shown in Figure 5.

[0019] FIG. 6 shows a partial cross-sectional view of the case where such conventional shearing is used to form a through hole in the above embodiment. In the plug 3, the plug grooves 31, 32 are formed in the portion close to the upper surface (i.e., the punch side surface) of both the first metal sheet 1 and the second metal sheet 2, and plastic flow occurs mainly in this portion, so that even if the fracture surfaces 12, 22 exist in each metal sheet, each metal sheet and the plug can be reliably joined. Therefore, the joining method according to the present invention is a useful technique for such a through hole formed by conventional shearing. In addition, although the method of joining two kinds of metal sheets is shown in this embodiment, this method makes it possible to join the entire metal sheets by joining them with the plug in sequence, even if there are three or more metal sheets.

[0020] Next, a process diagram of a second embodiment of the present invention is shown in Figure 7. A first metal sheet 1 and a second metal sheet 2, each having through holes 101, 102, are stacked so that the positions of the through holes 101, 102 are aligned, and a plug 3 is inserted into them. In this example, a punch 4a is operated from above and a punch 4b is operated from below at the same time, and both sides of the metal sheet stack are pressed at the same time.

[0021] FIG. 8 shows the state of the combined metal plates in this embodiment. The first metal plate 1 is a steel plate (SPCE), and the second metal plate 2 is an aluminum plate (A5052-O). In this example, the punch is operated from both sides, so punch marks 41 and 42 are formed on both sides of the combined metal plates. When conventional shearing is used to form a through hole, it is preferable to stack the second metal plate 2 upside down, taking into consideration the generation of the fracture surface as described above. Furthermore, it is preferable to form the plug grooves 31 and 32 on the plug 3 near the surface opposite to the stacking surface. In this embodiment, the joining of two metal plates is shown, but for three or more metal plates, the entire stacked multiple metal plates can be joined by joining each of the outermost metal plates on both sides to the plug. In this case, since the intermediate metal plate is not directly joined to the plug, it can be used in fields where high strength is not required.

[0022] The diversity of plug shapes is shown in FIG. 9. In the above-mentioned embodiment, an example in which the plug groove is partially formed is shown, but FIG. 9(a) shows an example in which the groove is formed on the entire side of the plug. When both metal plates to be joined are thin, it is effective to form a groove on the entire side of the plug like this. Also, FIG. 9(b) shows an example in which there is no groove at all. The effect of plastic flow is higher when a groove is formed in the plug, but when high joining strength is not required, a certain joining strength can be obtained by the pressure of the plastic flow even without a groove. According to an experiment, the plastic flow caused by the pressure of the punch fills the minute gap with the plug, and the friction resistance effect caused by the high tightening pressure at the interface can obtain about 50% of the joining strength of the case with a groove. Since the cost of the plug can be kept low, it can be used as it is for products that meet the required strength. In addition, any shape of the groove other than that shown in the figure can be used.

[0023] As for the material of the plug, when the metal plate to be joined is an aluminum plate, a rolled steel plate, or a soft steel plate such as SS400, a tempered steel (HRC30 to 40) is suitable. When a high-tensile steel plate with a tensile strength of 780 MPa or more is used, it is preferable to use a hardened and tempered steel as the plug. Furthermore, it is also possible to use a non-metallic material, such as ceramic, as the plug, so long as its hardness is higher than that of the metal plate.

[0024] An explanatory diagram of a third embodiment of the present invention is shown in Fig. 10. When one or both of the metal plates are thin, the pressing force may cause the plastic deformation area to penetrate in the thickness direction, and some of the pressed material may escape in the radial direction outward without flowing into the joining groove, resulting in insufficient joining force. Therefore, by using a plate holder 5 with protrusions 50 for the plate material around the punch, the deformation in the outer periphery of the plate material is restricted, and the plastic flow of the material into the joining groove is promoted, making it possible to expand the application to thin plate materials.

[0025] An explanatory diagram of a fourth embodiment of the present invention is shown in Fig. 11. In order to restrict the escape of the plate material toward the outer periphery and to increase the amount of flow into the joining groove, it is also effective to provide an angle to the tip 40 of the punch 4 as shown in this figure. [Explanation of symbols]

[0026] 1 First metal plate 2 Second metal plate 3 Plug 4 Punch 4a Upper punch 4b Lower punch 5 Plate holder 11 Shear surface 12 Fracture surface 22 Fracture surface 30 Plug groove 31 Plug groove 32 Plug groove 40 Punch tip 41 Punch mark 42 Punch marks 43 Punch mark 50 protrusions 51 Protrusion marks 101 through hole on first metal plate 201 Through hole on second metal plate

Claims

1. A method for joining metal plates, comprising the steps of: forming a through hole at the same location on multiple metal plates stacked one above the other; inserting a plug into the through hole, the plug having a cross-sectional shape approximately the same as the cross-sectional shape of the through hole and having a hardness greater than any of the metal plates; and applying pressure to the periphery of the plug on the surfaces of at least two outermost metal plates of the stacked metal plates, thereby plastically deforming each metal plate in the direction of the surface of the plug and applying a tightening stress to the plug, thereby joining the multiple metal plates through the plug.

2. 2. The method for joining metal plates according to claim 1, characterized in that the plurality of metal plates are first and second metal plates, the method including inserting the plug into a through hole in the first metal plate, applying pressure to the periphery of the plug on the first metal plate to join the first metal plate and then fitting the plug joined to the first metal plate into the through hole in the second metal plate, and then applying pressure to the periphery of the plug on the second metal plate to join the second metal plate and the plug, thereby ultimately joining the first and second metal plates.

3. 2. The method for joining metal plates according to claim 1, wherein the plurality of metal plates are first, second and third metal plates, the method including the steps of: inserting the plug into a through hole in the first metal plate, and applying pressure to the periphery of the plug on the first metal plate to join the first metal plate and the plug; then fitting the plug joined to the first metal plate into the through hole of the second metal plate, and applying pressure to the periphery of the plug on the second metal plate to join the second metal plate and the plug; and further fitting the plug joined to the first and second metal plates into the through hole of the third metal plate, and applying pressure to the periphery of the plug on the third metal plate to join the third metal plate and the plug, thereby joining the first, second and third metal plates together.

4. 2. The method for joining metal plates according to claim 1, wherein the plurality of metal plates are first and second metal plates, the first metal plate and the second metal plate are stacked to form a laminate, the plugs are inserted by aligning the positions of the respective through holes, and pressure is simultaneously applied from both sides around the plugs on the surface of the laminate to join the first and second metal plates.

5. 2. The method for joining metal plates according to claim 1, wherein the plurality of metal plates are first, second and third metal plates, the through holes of the metal plates are aligned and stacked to form a laminate, the plugs are inserted into the through holes, and pressure is simultaneously applied from both sides to the periphery of the plugs on the surface of the laminate to join the first, second and third metal plates.

6. 6. The method for joining metal plates according to claim 1, wherein the through hole has a circular cross-sectional shape, and the plug also has a circular cross-sectional shape.

7. 7. The method according to claim 1, further comprising providing a plurality of circumferential grooves on the periphery of said plug.

8. 8. The method for joining metal plates according to claim 7, wherein said grooves are formed closer to the pressure side surface of each of said metal plates.

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