Methods for joining dissimilar materials

Abstract

To provide a dissimilar material joining method that ensures a sufficient strength while suppressing an increase in cost of manufacture even if a metal plate with a through hole is joined.SOLUTION: A rivet 30 comprising a shade part 31 and a shank 33, an aluminum plate 40 having a through hole 40a with a diameter larger than the shaft 33 and iron plates 50, 60, an upper electrode 3 and a lower electrode 5 are prepared. The method includes: a process in which the rivet 30 of which the shank 33 is inserted in the through hole 40a, and the aluminum plate 40 and the iron plates 50, 60 are pinched between the upper electrode 3 and the lower electrode 5 so that the shade part 31, the aluminum plate 40 and the iron plate 50 are arranged in this order; and a pressurization and electric conduction process in which the rivet 30, and the aluminum plate 40 and iron plates 50, 60 are pressurized and electrically conducted. In the pressurization and electric conduction process, electric conduction is conducted at a high current value and in a short time so that a nugget 71 is generated between the shank 33 and the iron plate 50, and a clearance C between the shank 33 and the through hole 40a is filled.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for joining dissimilar materials, and more particularly to a method for joining a plurality of metal plates by resistance welding using rivets. [Background technology]

[0002] Conventionally, there has been known a method for joining dissimilar metal members by resistance welding using a metal rivet having a cap and a shaft. In this method, for example, the rivet, aluminum plate, and iron plate are sandwiched between two electrodes in the order of cap, shaft, aluminum plate, and iron plate, and these are pressurized and electrified to generate a nugget between the shaft that penetrates the aluminum plate and the iron plate, and the aluminum plate is sandwiched between the cap and iron plate to join the aluminum plate and the iron plate, which are difficult to weld.

[0003] Incidentally, when an aluminum sheet and a steel sheet are separated due to an incomplete joining, it is known to repair (re-weld) them by removing the old rivet and inserting a new rivet into the hole formed by the rivet penetrating during the initial joining. Since a through hole has already been formed in the aluminum sheet during such re-welding, it is common to apply normal steel spot welding conditions (relatively low current value) since it is only necessary to form a nugget between the rivet and the steel sheet.

[0004] However, when rewelding using such normal iron spot welding conditions, there is a problem in that a gap exists between the aluminum plate (more precisely, the wall surface defining the through hole) and the inserted rivet, making it difficult to ensure sufficient strength.

[0005] Although this is not related to rewelding, for example, Patent Document 1 discloses a technique for unremovably fixing a part having a hole formed therein to a base part with a bolt, in which the tip face of the bolt inserted into the hole is electrically welded to the surface of the base part and the shank of the bolt, which has been heated and softened, is crushed (plastically deformed so as to expand perpendicular to the axis) to fill the gap with the hole. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2008-538232 A Summary of the Invention [Problem to be solved by the invention]

[0007] If the technique of Patent Document 1 is applied to rewelding, the crushed shaft portion will fill the gap between the aluminum plate and the rivet (bolt), making it possible to ensure strength.

[0008] However, the method of Patent Document 1 has the problem that the shaft portion undergoes plastic deformation, and therefore a reinforcing rivet must be prepared separately to fill the gap between the aluminum plate and the rivet, resulting in increased manufacturing costs.

[0010] The present invention has been made in consideration of these points, and its object is to provide a method for joining dissimilar materials that can ensure sufficient strength while suppressing increases in manufacturing costs, even when joining metal plates having through holes. [Means for solving the problem]

[0011] In order to achieve the above-mentioned objective, the dissimilar material joining method of the present invention does not require the use of a separate reinforcing rivet, but instead involves passing a high current through a short period of time to generate a nugget and fill the gap between the rivet and the through hole.

[0012] Specifically, the present invention relates to a first metal plate and a second metal plate arranged in the order of a cap of an iron rivet, a shank of the iron rivet, a first metal plate made of an aluminum plate, and a second metal plate made of an iron plate, the rivet, the first metal plate and the second metal plate are sandwiched between a first electrode and a second electrode, and a current is applied thereto to cause the shank of the rivet to penetrate the first metal plate and a nugget is formed between the shank and the second metal plate, and the first metal plate is sandwiched between the cap and the second metal plate to form an object by joining the first metal plate and the second metal plate together, when the joined state of the metal plates is released by removing the rivet, a shank of a new iron rivet different from the removed rivet is inserted into a through hole having an inner diameter larger than the outer diameter of the shank, which is formed in the first metal plate by removing the rivet, Multiple metal plates are resistance welded together By rewelding The present invention relates to a method for joining dissimilar materials.

[0013] And this dissimilar material joining method is Above the new rivet Kikasabe, the above A first metal plate; the above The second metal plate is arranged in this order. The new rivets The shaft portion is inserted into the through hole. The a step of sandwiching the rivet and the stacked metal plates between the first electrode and the second electrode; and New and a pressurizing and current-passing step of pressurizing and current-passing the rivet and the plurality of metal plates, in which a nugget is generated between the shank and the second metal plate, and a current is passed for a short time at a current value approximately equal to a current value required to penetrate the shank through the first metal plate so that the gap between the shank and the through hole is filled by melting the first metal plate. the current value equivalent to the current value required to penetrate the shank into the first metal plate is the current value required to penetrate the iron shank into the aluminum plate, and the short period of time is set as a time during which the force generated by the volume expansion of the molten aluminum accompanying the melting of the first metal plate does not exceed the force applied by the cap of the rivet. It is characterized by the above.

[0014] With this configuration, when welding the shank of the rivet inserted into the through hole to the second metal plate, a current is passed through the rivet at a value approximately equal to the current required to penetrate the shank into the first metal plate, in other words, at a higher current than in the case of a normal iron spot.This not only produces a nugget between the shank and the second metal plate, but also melts the first metal plate to fill the gap between the shank and the through hole.

[0015] In this way, by passing a high current through the shaft, the gap between the shaft and the through hole can be filled without the need for a separate reinforcing rivet, thereby preventing an increase in manufacturing costs while ensuring sufficient strength.

[0016] In addition, since the high current flow is limited to a short period of time, the volumetric expansion of the molten first metal can be suppressed by the cap of the rivet, thereby preventing the molten first metal from being released and causing burrs. Effect of the Invention

[0017] As described above, according to the dissimilar material joining method of the present invention, even when joining metal plates having through holes, it is possible to ensure sufficient strength while suppressing increases in manufacturing costs. [Brief description of the drawings]

[0018] [Figure 1] 1A to 1C are diagrams for illustrating an outline of a dissimilar material joining method according to an embodiment of the present invention. [Diagram 2] FIG. 2(a) is a diagram showing a schematic view of a main part of a resistance welding device, and FIG. 2(b) is a diagram showing a schematic view of a current pattern in a method for joining dissimilar materials. [Diagram 3] FIG. 3(a) is a diagram showing a typical current pattern, and FIG. 3(b) is a diagram showing a typical case where a high current is applied for a long period of time. [Figure 4] FIG. 1 is a graph showing the test results of shear strength. [Diagram 5] 1A and 1B are diagrams for explaining a conventional method for dealing with a joint failure; [Figure 6] 1A to 1C are diagrams for explaining a schematic diagram of an example of a conventional method for joining dissimilar materials. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In order to make the drawings easier to understand, in Fig. 1 to Fig. 6, a rivet 30, an aluminum plate 40, and iron plates 50, 60, etc. are shown in cross section.

[0020] -Device configuration- Fig. 1 is a diagram for explaining the outline of the dissimilar material joining method according to the present embodiment. Fig. 2(a) is a diagram showing a schematic view of a main part of a resistance welding apparatus 1, and Fig. 2(b) is a diagram showing a schematic view of a current pattern in the dissimilar material joining method. As shown in Fig. 1(b), the dissimilar material joining method uses a resistance welding apparatus 1 and a rivet 30 to join a plurality of metal plates 40, 50, 60, including metal plates made of different metal materials, by resistance welding. 。

[0021] As shown in FIG. 2(a), the resistance welding device 1 includes an upper electrode 3 and a lower electrode 5. The upper electrode (first electrode) 3 is formed in a cylindrical shape and configured as a flat electrode with a flat tip surface. This upper electrode 3 presses the rivet 30 downward against the stacked aluminum plate 40 and iron plates 50, 60. The lower electrode (second electrode) 5 is formed in a substantially cylindrical shape and configured as a radius electrode with a spherical tip surface. This lower electrode 5 is disposed so as to face the upper electrode 3 across the vertically stacked aluminum plate 40 and iron plates 50, 60, and presses the aluminum plate 40 and iron plates 50, 60 upward.

[0022] 2(a), the rivet 30 used in this embodiment is made of iron and has a substantially disk-shaped cap portion 31, a shaft portion 33 extending downward from the center of the cap portion 31, and an outer peripheral wall portion 35 extending from the periphery of the cap portion 31 in the same direction as the shaft portion 33 and forming a groove 37 between the shaft portion 33 and the outer peripheral wall portion 35. The rivet 30 is set in the resistance welding device 1 so that the cap portion 31 is perpendicular to the lamination direction.

[0023] When using the resistance welding apparatus 1 and rivet 30 configured as described above to join an aluminum plate 40 and iron plates 50, 60, which are different metal materials, the rivet 30, aluminum plate 40, iron plate 50 and iron plate 60 are typically sandwiched between the upper electrode 3 and the lower electrode 5 so that the cap portion 31, shaft portion 33, aluminum plate 40, iron plate 50 and iron plate 60 are arranged from top to bottom in that order, and then a current is applied to the rivet 30, aluminum plate 40, iron plate 50 and iron plate 60 while applying pressure with the upper electrode 3 and lower electrode 5.

[0024] Typically, at this time, as shown in Fig. 3(a), a relatively high current is applied for a short period of time in the early stages of current flow, causing the shank 33 of the rivet 30 to penetrate the aluminum plate 40. Then, from the middle stage of current flow onwards, the shank 33 of the rivet 30 has penetrated the aluminum plate 40, and spot welding is performed between iron plates (the rivet 30 and the iron plates 50, 60), so a relatively low current is applied for a long period of time to form a nugget 70 as shown in Fig. 2(a) between the shank 33 that has penetrated the aluminum plate 40 and the iron plates 50, 60.

[0025] This is a common method of joining dissimilar materials, in which the shaft 33 of the iron rivet 30 is welded to the iron plates 50, 60, and the aluminum plate 40 is sandwiched between the cap 31 of the rivet 30 and the iron plate 50, thereby joining the aluminum plate 40 and the iron plate 50, which are difficult to weld.

[0026] However, in this embodiment, as shown in Figures 1(a) and 2(a), the aluminum plate 40 already has a through hole 40a prior to resistance welding, and therefore, as described below, the joining of dissimilar materials is performed using a method different from the general dissimilar material joining method described above.

[0027] - Conventional measures for poor joints - Here, in order to facilitate understanding of this embodiment, a conventional response (repair) to a joint failure will be described. Fig. 5 is a diagram for explaining a conventional response to a joint failure. Note that the conventional response shown in Fig. 5 also uses the same resistance welding device 1 and rivet 30 as in this embodiment.

[0028] As shown in Figure 5(a), it is assumed that a poor bond occurred between the rivet 30' and the steel plate 50 (for example, a nugget 70 was formed between the iron plates 50 and 60, but the rivet 30' and the nugget 70 were not bonded), causing separation between the aluminum plate 40 and the steel plate 50.

[0029] In this case, the old rivet 30' is removed and repair is performed using a new rivet 30, but since a certain amount of the aluminum base material is also removed when the old rivet 30' is removed, at the time of repair, as shown in Fig. 5(b), a through hole 40a having an inner diameter larger than the outer diameter of the shank 33 of the new rivet 30 is formed in the aluminum plate 40. Therefore, at the time of repair, a gap C is generated between the shank 33 of the new rivet 30 inserted into the through hole 40a and the through hole 40a.

[0030] 5(c), current is applied while applying pressure with the upper electrode 3 and the lower electrode 5, but in this case, because spot welding is performed between iron (the rivet 30 and the iron plates 50, 60), a relatively low current is applied for a relatively long time to weld the nugget 70 formed between the iron plates 50, 60 and the shank 33. In this way, because a relatively low current is applied, the aluminum plate 40 is not affected by the current flow, and a gap C remains between the shank 33 of the rivet 30 and the through hole 40a.

[0031] In this manner, the repair is completed by rewelding the shank 33 of the rivet 30 and the nugget 70 formed between the steel plates 50, 60, but in the repaired dissimilar material joint member 110, a gap C remains between the shank 33 of the rivet 30 and the through hole 40a, as shown in Fig. 5(d). For this reason, in the conventional method, a fracture occurs between the aluminum plate 40 and the rivet 30, which causes a problem that the joint strength (shear strength) of the dissimilar material joint member 110 decreases.

[0032] Here, although it is not related to rewelding, it is possible to adopt a dissimilar material joining method as shown in Fig. 6. The conventional dissimilar material joining method shown in Fig. 6 is a method for fixing a part 140 having a hole 140a formed therein to a basic part 150 with a bolt 130 so that it cannot be removed, and the tip surface of the bolt 130 inserted into the hole 140a is electrically welded to the surface of the basic part 150, and the shaft portion 133 of the bolt 130 which has been heated and softened is crushed (plastically deformed so as to expand in the direction perpendicular to the axis) to fill the gap with the hole 140a. If this conventional dissimilar material joining method is applied to rewelding, the crushed shaft portion fills the gap C between the aluminum plate 40 and the rivet, and it seems possible to ensure strength.

[0033] However, with this conventional method of joining dissimilar materials, the shaft portion undergoes plastic deformation, and a reinforcing rivet must be prepared separately to fill the gap between the aluminum plate 40 and the rivet, resulting in an increase in manufacturing costs.

[0034] -Dissimilar materials joining method- Therefore, in the dissimilar material joining method according to this embodiment, a nugget 71 is generated and the gap C between the rivet 30 and the through hole 40a is filled by passing a high current for a short period of time without preparing a separate reinforcing rivet.

[0035] Specifically, the dissimilar material joining method of this embodiment includes a process of sandwiching a new rivet 30, with its shaft portion 33 inserted into the through hole 40a, and the stacked aluminum plates 40 and iron plates 50, 60, between the upper electrode 3 and the lower electrode 5 so that the cap portion 31, the aluminum plate (first metal plate) 40, and the iron plate (second metal plate) 50 are arranged in that order, as shown in Figure 1(a), and a pressurizing and current-passing process of pressurizing the rivet 30, the aluminum plate 40, and the iron plates 50, 60 using the upper electrode 3 and the lower electrode 5.

[0036] Then, in the pressurized current application process, as shown in FIG. 1(b), a nugget 71 is generated between the shaft portion 33 and the iron plate 50, and current is applied for a short period of time at a relatively high value so that the vicinity of the through hole 40a in the aluminum plate 40 is melted and the gap C between the shaft portion 33 and the through hole 40a is filled with molten aluminum 41.

[0037] Here, when a relatively low current is applied to form a nugget 70 as shown in Figure 3(a) in order to form a nugget 71 between the shank 33 and the steel plate 50, as described above, the aluminum plate 40 is not affected by the current flow and a gap C remains between the shank 33 of the rivet 30 and the through hole 40a.

[0038] Therefore, the "relatively high current value" in this embodiment refers to a high current value equivalent to the current value required to penetrate the shank 33 into the aluminum plate 40. In this manner, in the dissimilar material joining method of this embodiment, current is passed at a current value equivalent to the current value required to penetrate the shank 33 into the aluminum plate 40, so that the aluminum plate 40 is melted and the gap C between the shank 33 and the through hole 40a can be filled as shown in FIG. 1(b). As a result, as shown in FIG. 1(c), a nugget 71 is generated between the iron plate 50, in which the nugget 70 has already been generated between the iron plate 60, and the shank 33 of the rivet 30 inserted into the through hole 40a of the aluminum plate 40, and it is possible to manufacture a dissimilar material joining member 10 in which the gap C between the shank 33 and the through hole 40a is filled.

[0039] Furthermore, when applying current for a relatively long time to produce a nugget 70 as shown in Figure 3(a), if a relatively high current value (a current value similar to the current value required to penetrate the aluminum plate 40 with the shank 33) is used, the "volume expansion of the molten aluminum 41" will exceed the "pressing force by the cap portion 31 of the rivet 30", and as shown by the thick arrow in Figure 3(b), the molten aluminum 41 will be released outside the cap portion 31 of the rivet 30, which may result in a burr.

[0040] In this regard, in the dissimilar material joining method of the present embodiment, a relatively high current is passed for a short time, and the aluminum base material is also removed to a certain extent when the old rivet 30' is removed, so that the volume of the expanding aluminum can be reduced even when a relatively high current is passed. Therefore, the "volume expansion of the molten aluminum 41" does not exceed the "pressing force of the cap portion 31 of the rivet 30", and the occurrence of burrs can be suppressed.

[0041] -Test Results- Next, a test performed to confirm the effect of the dissimilar material joining method of the present embodiment will be described. In the test, a dissimilar material joined member without joining defects, a dissimilar material joined member 110 (conventional example) repaired by the conventional method shown in Fig. 5, and a dissimilar material joined member 10 (example) repaired by the dissimilar material joining method of the present embodiment were processed into test pieces as specified in JIS standard Z2201-5 and then subjected to a tensile test.

[0042] Fig. 4 is a graph diagram showing the shear strength test results. As shown in Fig. 4, in the conventional example in which the gap C between the shaft portion 33 and the through hole 40a remains, the tensile shear strength is reduced by about 25% compared to the dissimilar material joint member without joint defects, whereas in the embodiment, it was confirmed that the tensile shear strength was equivalent to that of the dissimilar material joint member without joint defects.

[0043] As described above, according to the method for joining dissimilar materials according to this embodiment, even when joining metal plates having a through hole 40a, it is possible to ensure sufficient strength while suppressing an increase in manufacturing costs.

[0044] (Other embodiments) The present invention is not limited to the embodiments, and can be embodied in various other forms without departing from the spirit or main characteristics thereof.

[0045] In the above embodiment, three metal plates (the aluminum plate 40 and the iron plates 50, 60) are joined together, but the present invention is not limited to this, and for example, four or more metal plates may be joined together.

[0047] Furthermore, in the above embodiment, the stacking direction and pressing direction of the metal plates are aligned with the vertical direction, but this is not limited to the above, and the stacking direction and pressing direction may be aligned with, for example, a direction inclined from the vertical direction or with the horizontal direction.

[0048] As such, the above-described embodiment is merely illustrative in all respects and should not be construed as limiting. Furthermore, all modifications and variations within the scope of the claims are within the scope of the present invention. [Industrial Applicability]

[0049] According to the present invention, even when joining metal plates having through holes, it is possible to ensure sufficient strength while suppressing increases in manufacturing costs, making it extremely useful to apply the present invention to a dissimilar material joining method in which multiple metal plates are joined by resistance welding using rivets. [Explanation of symbols]

[0050] 3 Upper electrode (first electrode) 5 Lower electrode (second electrode) 30 Rivet 31 Kasabe 33 Shaft 40 Aluminum plate (first metal plate) 40a through hole 50 Iron Plate (Second Metal Plate) 71 Nugget C Gap

Claims

[Claim 1] a first metal plate and a second metal plate are arranged in the following order: a cap of an iron rivet, a shank of the iron rivet, a first metal plate made of an aluminum plate, and a second metal plate made of an iron plate, and the cap and electric current are applied thereto to cause the shank of the rivet to penetrate the first metal plate, forming a nugget between the shank and the second metal plate, and the first metal plate is sandwiched between the cap and the second metal plate to form an object by joining the first metal plate and the second metal plate; when the joined state of the metal plates is released by removing the rivet, a shank of a new iron rivet different from the removed rivet is inserted into a through hole having an inner diameter larger than an outer diameter of the shank, which is formed in the first metal plate by removing the rivet, and the multiple metal plates are joined by re-welding using resistance welding; a step of sandwiching the rivet and the stacked metal plates, with the shank of the new rivet inserted into the through hole, between the first electrode and the second electrode such that the cap of the new rivet, the first metal plate, and the second metal plate are arranged in this order; a pressurizing and current-passing step of pressurizing and current-passing the new rivet and the plurality of metal plates by the first and second electrodes, In the pressurizing and current passing step, a nugget is generated between the shaft portion and the second metal plate, and current is passed for a short time at a current value approximately equal to a current value required to pass the shaft portion through the first metal plate so that the gap between the shaft portion and the through hole is filled by melting the first metal plate, a current value equivalent to the current value required to penetrate the shaft portion through the first metal plate is a current value required to penetrate the iron shaft portion through the aluminum plate, A method for joining dissimilar materials, characterized in that the short period of time is set as a time during which the force generated by the volumetric expansion of molten aluminum accompanying the melting of the first metal plate does not exceed the pressing force exerted by the cap portion of the rivet.

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