JP2008030113A - Dissimilar metal joining method - Google Patents

Abstract

For example, when applied to the joining of automobile body structures using a roof panel made of light alloy, these dissimilar metal materials can be bonded to each other without impairing the appearance and the degree of freedom of design by heating from the outside of the body. Provided is a method for joining dissimilar metals which can be joined and can prevent the intrusion of moisture into the joined part by applying a sealing material as required.
A third plate made of a high melting point material of the same type as that of the first plate is further stacked on a second plate made of a low melting point material that is stacked on the first plate made of a high melting point material. The defocused high energy beam Bp is irradiated to soften the second plate material 2, and the softened second plate material 2 is cut by pressing with the pressure roller 8 to be removed from the bonding interface. The plate material 1 and the third plate material 3 are brought into direct contact with each other, and the contact portion is irradiated with a high energy beam Bw to melt-bond the first and third plate materials 1 and 3. If necessary, a sealing material is interposed between these plate materials.
[Selection] Figure 2

Description

  In the present invention, a plate material made of a metal material having a lower melting point than these, for example, an aluminum alloy, and a sealing material are sandwiched between different plate materials such as a high melting point metal material such as steel. The present invention relates to a method for lap-joining a joint.

  Conventionally, in the joining of dissimilar materials using a high energy beam such as an electron beam or a laser beam, a defocused high energy beam is applied to the surface of the high melting point material in order to suppress the formation of brittle intermetallic compounds. A method has been used in which the low melting point material side of the bonding interface is melted and bonded by heat transfer from the side of the high melting point material irradiated and heated by beam irradiation.

  In such a case, the welding conditions are controlled, only the material on one side (low melting point material) is melted at the joining interface, and the growth of the intermetallic compound layer is suppressed by joining using the diffusion of the material. By reducing the thickness, it is considered that the strength per unit area of the joint can be increased as compared to the case where both materials are melted and joined together. In addition, a method is described in which a steel plate is stacked on an aluminum alloy and a laser beam is irradiated from above the steel plate to join different materials with the interface in a solid / liquid phase state.

Non-Patent Document 2 describes a method by mechanical fastening, that is, a method of joining an aluminum alloy panel to a steel body frame structure by driving a rivet or the like from the aluminum alloy side.
“Overview of the National Conference of the Japan Welding Society”, Japan Welding Society, April 2003, Vol. 72, p. 152 Mitsubishi Motors Technical Review 2004, No. 16, p. 82

However, in the method described in Non-Patent Document 1, only the aluminum alloy at the bonding interface is melted by heat transfer from the steel plate, so that the steel plate is inevitably overlapped on the aluminum alloy, and from the outer side on the steel plate side. There was a restriction on the structural design of the joint joint that the laser beam had to be irradiated.
That is, for the purpose of improving fuel efficiency and athletic performance by reducing the weight of the vehicle, a vehicle body structure using a light alloy such as an aluminum alloy for the vehicle body panel is required. For example, in order to enhance the performance improvement effect by lowering the center of gravity When an aluminum alloy is used for the roof panel, the joining structure between the steel member and the aluminum alloy member, which is a vehicle body skeleton structure, is formed by stacking the roof panel made of aluminum alloy on the steel member, and the proximity of the laser head. This is a joint structure in which a laser beam must be irradiated from the outside of the vehicle body skeleton structure, that is, from the side of the aluminum alloy roof panel. Moreover, not only the roof panel, but also when using an aluminum alloy for other vehicle body outer panel, because it becomes a structure in which the aluminum alloy vehicle body panel is overlaid on the steel vehicle body skeleton structure, as described above, A method of irradiating a laser beam from the steel plate side cannot be applied.

Therefore, in practice, the use of the mechanical fastening method described in Non-Patent Document 2 is conceivable. However, this method has a problem in that there may be restrictions on the appearance and the degree of freedom of design. It was.
On the other hand, the above-mentioned dissimilar material joint has a problem that contact corrosion of dissimilar metals may progress when water enters the joint end where the dissimilar metals contact each other.

  The present invention has been made in view of the above problems in the joining technique of dissimilar metal materials. For example, when applied to the joining of a vehicle body structure using a light alloy roof panel, the invention can be applied from the outside of the vehicle body. By heating the metal, these dissimilar metal materials can be joined to each other without impairing the appearance and the degree of freedom of design, and by applying a sealing material as necessary, moisture can be prevented from entering the joint. It is an object of the present invention to provide a bonding method for dissimilar metals.

  In order to achieve the above-mentioned object, the present inventors have made extensive studies, and as a result, a steel plate material is further stacked and joined on a light alloy roof panel stacked on a steel body member. Thus, the inventors have found that the above problems can be solved, and have completed the present invention.

  That is, the present invention is based on the above knowledge, and in the dissimilar metal bonding method of the present invention, the first plate made of a high melting point material and the second plate made of a low melting point material are overlapped and bonded. At this time, a third plate made of the same high melting point material as the first plate is further stacked on the second plate, the third plate is heated, the second plate is softened by the heat transfer, and the third plate The second plate material softened by pressurization from the plate material side is cut to directly contact the first plate material and the third plate material, and the contact portion is further irradiated with a high-energy beam to irradiate the first plate material and the first plate material. 3 plate materials are melt-bonded.

  Further, when a sealing material is interposed between the plate materials in order to ensure the water tightness of the joint portion, the sealing material is cut together with the second plate material by heating and pressurization from the third plate material side. It is characterized by doing.

  According to the present invention, when the first plate made of a high melting point material and the second plate made of a low melting point material are overlapped and joined, the second plate is made of the same high melting point material as the first plate. The third plate member is further stacked, the third plate member is heated, the second plate member is softened by heat transfer from the third plate member, and the softened second plate member is cut by pressurization from the third plate member side. Since the first plate and the third plate are brought into direct contact with each other and then the first and third plates are welded, for example, the skeleton structure as described above is provided to reduce the center of gravity. When assembling the car body, it is possible to overlap and bond dissimilar materials by heating from the outside of the car body, which eliminates the restrictions on the joint structure and enables a structural design with a high degree of freedom. Can be improved.

  In the following, the method for joining dissimilar metals of the present invention will be described in more detail and specifically.

  In the method for joining dissimilar metals of the present invention, as described above, the third plate made of the same material as the first plate is further stacked on the second plate stacked on the first plate, The second plate material underneath is softened by heat transfer from there, and the softened second plate material is cut by pressurization from the third plate material side to be removed from the bonding interface, These first and third plate members are welded in a state where the first plate member and the third plate member are in direct contact with each other, and the cutting of the low melting point material (second plate member) in one process, High melting point materials (first and third plate materials) can be welded together, and the low melting point material is sandwiched between joints having high bonding strength between the high melting point materials, so that the low melting point material is made high. It can be firmly fixed between the melting point materials.

  And since it is set as the joint shape of the state which pinched | interposed the low melting-point material (2nd board | plate material) between high melting-point material (1st and 3rd board | plate material), it heats and pressurizes from any side. For example, in the assembly of an automobile body with a low center-of-gravity skeleton structure, it becomes possible to handle dissimilar material joining by heating and pressurization from the outside of the vehicle body. The restriction will be removed.

  In the present invention, the first plate material and the third plate material are made of the same kind of high melting point material, but in the present invention, “same type” means the same metal structure and component system, In the present invention, not only those belonging to the same standard but also different standards such as carbon steel and alloy steel, mild steel and high-tensile steel, and the like are used in the present invention as long as they have a ferrite structure.

In the present invention, the second plate member is heated through the third plate member, the second plate member is pressed from the third plate member side in order to cut the second plate member, and the first and first members that are in direct contact with each other. No particular limitation is imposed on the means for welding the plate material No. 3. For example, as the heating means, laser beam, resistance heating, heating by a heater, a burner, or the like can be applied. Further, as the pressurizing means, a cylindrical indenter, a pressure roller, or the like can be used, and by incorporating a heater inside these, it is possible to serve as both the heating means and the pressurizing means.
And as a welding means, laser welding, resistance welding, etc. are applicable, for example.

In the dissimilar metal joining method of the present invention, the sealing material is sandwiched between the plate materials, that is, between the first plate material and the second plate material, between the third plate material and the second plate material, or both. However, lap joining can be performed similarly.
That is, the sealing material is cut together with the second plate material by heating and pressurizing the third plate material, and discharged together from the joint portion. As a result, the first plate material and the third plate material are in direct contact with each other. It is possible to weld the first and third plate materials, that is, the high melting point materials. And by the sealing material discharged | emitted from the junction part, the penetration | invasion of the water to the dissimilar metal contact part of a junction part edge part can be prevented, and a rust prevention measure and joint strength improvement can be implement | achieved simultaneously.

  In the present invention, as the sealing material, for example, an epoxy resin-based material, a synthetic rubber-based material, a synthetic rubber / PVC-based material, or the like can be used. It can be applied to a sheet, or a sheet can be sandwiched between both materials.

  FIG. 1 and FIG. 2 are for explaining the joining procedure of dissimilar metals in the present invention. FIG. 1 shows a high energy beam as a heating means, a pressure roller as a pressure means, and a welding means. Side views seen from the direction of movement of the high-energy beam, that is, the direction orthogonal to the bonding line, FIGS.

  As shown in these drawings, a second plate material 2 made of a low melting point material (for example, an aluminum alloy material) is overlaid on a first plate material 1 made of a high melting point material (for example, a steel material). A third plate 3 made of a high melting point material (for example, steel) is overlaid on the second plate 2.

  First, as shown in FIG. 2 (a), a defocused laser beam Bp is moved as a heating means along the bonding line from the side of the third plate 3 which is a high melting point material. The third plate member 3 is heated while being irradiated, and the second plate member 2 having a lower melting point is heated and softened by heat transfer from the third plate member 3 having a high temperature.

  Subsequently, immediately after the irradiation position by the laser beam Bp, the third roller 3 is pressed by the pressure roller 5 in the direction in which the third plate 3 is pressed against the first plate 1, thereby, as shown in FIG. The second plate 2 which is a low melting point material is partially cut and discharged toward both sides in the welding progress direction, and the third plate 3 and the first plate 1 are brought into direct contact with each other.

  And the 2nd which focused on the surface of the 3rd board | plate material 3 to the site | part which contacted the 3rd board | plate material 3 and the 1st board | plate material 1 with the pressure roller 5, as shown in FIG.2 (c). The third plate member 3 and the first plate member 1 are welded by irradiating the laser beam Bw.

  By the above procedure, the second plate 2 that is a low melting point material can be fixed between the first plate 3 and the third plate 3, and the second plate 2 can be cut and cut in one process. Melting | fusing point materials, ie, the 1st and 3rd board | plate materials 1 and 3, are joined.

The laser beam Bp, the pressure roller 5 and the laser beam Bw are configured to be relatively movable with respect to the material to be joined, and the irradiation, pressurization, and relative movement of these laser beams are intermittent. By performing the above, these plate materials 1, 2, and 3 can be joined in an intermittent stitch shape.
Further, the pressure surface 5a (contact surface with the plate material) of the pressure roller 5 is provided with a curvature such that the central portion is convex, thereby giving the pressure portion a pressure distribution that increases the central portion. It is possible to cut the softened low-melting point material more efficiently at the pressurizing part and to easily discharge toward both sides of the welding progress direction, and the high-melting point materials can easily come into contact with each other. The first and third plate members 1 and 3 can be easily joined.

  Furthermore, when the first and third plate members 1 and 3 are continuously melted and bonded by continuously irradiating the laser beams Bp and Bw and pressurizing by the pressure roller 5, in many cases, a low melting point is obtained. Since the material (second plate material) may be completely cut and the second plate material 2 may not be fixed between the first and third plate materials 1 and 3, the above description is made. Thus, it is desirable that the first plate material 1 and the third plate material 3 are melt-bonded in a stitch shape by intermittently irradiating the laser beams Bp and Bw and applying pressure by the pressure roller 5. In addition, when joining the edge part of a board, you may make it perform pressurization and joining continuously.

FIGS. 3A to 3C show a procedure in which the sealing material S is sandwiched between the first plate material 1 and the second plate material 2 and between the third plate material 3 and the second plate material 2, respectively. Similarly, from the side of the third plate 3 that is a high melting point material, similarly, the third plate 3 is heated by irradiating the defocused laser beam Bp, and the heated third plate The second plate 2 is heated and softened by heat transfer from 3 (FIG. 3A).
Subsequently, the third plate 3 is pressed in a direction to be pressed against the first plate 1 by the pressure roller 5, and as shown in FIG. 3B, the second plate 2 which is a low melting point material and the sealing material S. Are partially cut out and discharged to both sides in the traveling direction, the first and third plate members are brought into direct contact with each other, and a laser beam Bp which is a welding means is irradiated on the portions, whereby the third plate member 3 and the third plate member 3 are 1 plate material 1 is welded (FIG. 3C).

  At this time, the sealing material S discharged and extruded from the joining interface by pressurization of the pressure roller 5 ensures water tightness at the joining interface and functions as a rust prevention mechanism.

  In the dissimilar metal joining method of the present invention, as shown in FIGS. 4A to 4C, the third plate 3 has a convex shape that protrudes in advance toward the second plate 2, A convex portion 3a having a plane with a predetermined width at the center and an emboss having an inverted W-shaped cross section having concave portions 3b, 3b on both sides of the convex portion 3a are formed intermittently along the joining line. It is desirable.

That is, since the central portion of the emboss protrudes toward the second plate member 2, a pressure distribution that increases the central portion can be given to the pressurizing portion, and the softened low melting point material (second Low melting point discharged from the central part of the pressurization by making it more efficient to cut the plate material) more efficiently at the pressurization part and discharging it in the lateral direction. Since the material enters the recess 3b, the discharged low-melting-point material is prevented from pushing up the third plate material 3, and the third plate material 3 is V-shaped by the pressure applied by the pressure roller 5. It is possible to prevent inconvenience such as deformation into a cross section.
Further, by providing the convex portion 3a with a width (a plane having a predetermined width), heat transfer from the third plate material 3 to the first plate material 1 is efficiently performed, and melting of the high melting point materials is performed. Joining can be easily performed. In addition, it is desirable that the dimension of the width is such that heat is sufficiently transmitted and the appearance is not deteriorated, and specifically, it is appropriate to be about 2 to 5 mm.

  5A to 5C, the sealing material S is disposed between the first plate material 1 and the second plate material 2, and between the second plate material 2 and the third plate material 3, respectively. 4 shows a procedure for intermittently forming an emboss as shown in FIG. 4 on the third plate 3 along the joining line and welding it in an intermittent stitch shape. The cutting and discharging of the second plate material 2 and the sealing material S by the pressure roller 5 become efficient, so that the deformation of the plate material can be prevented, and the discharged sealing material S is brought into close contact with the joining end portion to dissimilar metals. Intrusion of water into the contact portion between them is prevented, and the rust prevention function is exhibited in the same manner as shown in FIG.

  In the above, an example in which the defocused laser beam Bp is used as the heating unit and the pressing roller 5 is used as the pressing unit has been described. However, in the dissimilar metal bonding method of the present invention, the heating unit and the pressing unit are used. It is also possible to use a hot roller that also serves as the

That is, FIG. 6 shows a joining procedure using a hot roller, and the third plate member 3 is heated together with the first plate member 1 by the hot rollers 6 and 7 having a built-in heater. When the second plate material 2 is softened by heat, the second plate material 2 is cut and discharged from the joint by applying pressure with the hot rollers 6 and 7. After that, as a welding means, a laser beam is used. By irradiating the third plate member 3 with Bw, the first plate member 1 and the third plate member 3 can be welded.
At this time, like the pressure roller 5, the pressure surfaces (contact surfaces with the plate material) of the hot rollers 6 and 7 are desirably formed in a curved shape with a convex central portion, thereby softening. Thus, the low melting point material can be cut more efficiently and discharged from the joint.

Furthermore, instead of laser welding, resistance welding can be employed as the welding means.
For example, as shown in FIG. 7, hot rollers 6 and 7 with heaters can be used as the heating means and pressurizing means, and resistance seam welding can be used as the welding means.

  That is, by heating and pressurizing the joint using the hot rollers 6 and 7, the second plate member 2 is similarly cut and discharged, and then sandwiched by the roller electrodes 10 and 11, and the joint is pressed while pressing the joint. By energizing between the first and third plate members 1 and 3 and rotating the roller electrodes 10 and 11, resistance welding proceeds continuously, and both materials can be joined in a linear form.

Furthermore, in the method for joining dissimilar metals of the present invention, resistance spot welding can also be applied as a welding means.
FIG. 8 shows an example in which cylindrical indenters 14 and 15 are used as heating and pressing means, and a resistance spot welder is used as welding means. The indenters 14 and 15 have a heater incorporated therein, so that the second plate 2 sandwiched between the first and third plates 1 and 3 can be heated by heat transfer. Further, if necessary, a structure in which a weak current is caused to flow between the indenters 14 and 15 while sandwiching the material to be joined to cause resistance heat generation between the materials can be employed.

  The softened second material is cut by heating and pressurization by the indenters 14 and 15, and the first and third plate materials 1 and 3 discharged from the combined portion and directly in contact with the pair of spot welding electrodes 16 and 17 is sandwiched between the two plate members 1 and 3 and the spot welding is completed.

FIG. 9 shows an example in which high-frequency heating is used as the heating means and resistance spot welding is applied as the pressurizing and welding means.
That is, by energizing the high-frequency coils 18 and 19, the second plate 2 is heated via the first and third plates 1 and 3, and the heated portion is then paired with the pair of spot welding electrodes 16, 17 These plate materials are relatively pressurized. As a result, the second plate 2 is cut and discharged from the joining portion, and thereafter, by conducting current between the electrodes 16 and 17, spot welding is performed and the joining is completed.

In the method for joining dissimilar metals of the present invention, as specific metal material combinations, for example, the first and third plate materials (high melting point materials) are steel plates, and the second plate material (low melting point material) is aluminum. An alloy plate can be used, and it can be applied to different types of joining in various machine parts including automobiles.
That is, when the steel plate is heated before joining, only the aluminum alloy plate sandwiched between them can be melted or softened without melting the outer steel plate. Only the plate can be cut at the pressurization site and discharged from the junction site.

  Hereinafter, the present invention will be specifically described based on examples. In addition, this invention is not limited at all by these Examples.

10 and 11 show an example in which the dissimilar metal joining method of the present invention is applied to the roof structure of an automobile body. FIG. 10 is a perspective view showing the joining structure of the car body, and FIG. It is sectional drawing which shows the junction point.
As shown in the figure, the steel rail inner 21 (plate thickness: 1.4 mm), rail outer 22 (plate thickness: 0.8 mm), and side outer 23 (plate thickness: 0.8 mm) are assembled by welding. A roof panel 31 (plate thickness: 1.0 mm) made of a 6000 series aluminum alloy is stacked from above the body member 20 formed.

The side outer 23 (first member) of the vehicle body member 20 is provided with a joint surface 23a, and a joint flange 31a formed at the end of the roof panel 31 (second member) is overlapped on this portion.
Further, a steel retainer 41 (plate thickness: 0.8 mm) is superimposed on the joint flange 31a of the roof panel 31 as a third plate member.

The laser beam Bp and the laser beam Bw are irradiated from the retainer 41 side. The pressure roller 5 is configured to press the joining flange 31a of the retainer 41 and the roof panel 31 in a direction in which the joining flange 31a is pressed against the side outer 23 of the vehicle body member 20 from the retainer 41 side.
The laser beam Bp, the laser beam Bw, and the pressure roller 5 are disposed so as to be movable relative to the vehicle body member 20.

First, while moving the defocused laser beam Bp, the surface is irradiated from the direction of the retainer 41 to heat the retainer 41. And the joining flange 31a of the roof panel 31 is heated by the heat transfer from the heated retainer 41, and the said joining flange 31a is softened by this.
Subsequently, immediately after the position of irradiation with the defocused laser beam Bp, the retainer 41 is pressed against the vehicle body member 20 using the pressure roller 5 having a pressure curved surface as a convex curved surface. As a result, the joint flange 31a of the roof panel 31 is partly cut and discharged toward both sides in the welding progress direction, and the retainer 41 and the side outer 23 of the vehicle body member 20 are brought into direct contact with each other.

  A portion of the retainer 41 and the side outer 23 that are in direct contact with the pressure of the pressure roller 5 is irradiated with a laser beam Bp focused on the surface of the retainer 41, and the side outer 23 of the retainer 41 and the vehicle body member 20. Are intermittently welded at the melt joint W (see FIG. 11).

Note that an Nd: YAG laser is used as the laser beam, and the irradiation condition is that the surface of the retainer 41 is irradiated with the preceding laser beam Bp, and the aluminum alloy roof panel 31 is heated by heat transfer from the heated retainer 41. Each of the joining flanges 31a is softened and cut by the pressure of the subsequent pressure roller 5 and can be discharged to both sides thereof. Further, the retainer 41 and the side outer 23 can be melt-bonded at the contact portion by the following laser beam Bw. The focal positions of the laser beams Bp and Bw, the laser output, the roller pressing force, the feed speed, etc. were set.
Specifically, a laser oscillator with a maximum output of 3 kW and a lens with a focal length of 150 mm are used, and for the preceding laser beam Bd, the laser output is 2.0 kW, and the spot diameter on the surface of the retainer 41 is φ5 mm. For the subsequent laser beam Bw, the laser output is set to 1.0 kW, the focal point is adjusted to be just focused on the surface of the retainer 41, and the pressing force of the pressure roller 5 is set to 2.5 kN. Irradiation was performed at a feed rate of 0.7 to 1.0 m / min. Further, during laser irradiation, argon gas was flowed at a flow rate of 25 L / min to shield the joint.

By joining based on the above-described procedure, the joining flange 31a of the aluminum alloy roof panel 31 is fixed between the side outer 23 and the retainer 41 of the vehicle body member 20 without performing preliminary processing or the like on the roof panel 31. Can do.
In addition, by providing the pressure surface of the pressure roller 5 with a curved surface having a convex central portion, a pressure distribution that increases the central portion can be given to the pressure portion, and the softened roof panel 31 is joined. By applying pressure to the flange 31a effectively, the flange 31a can be cut and discharged from the joined portion more efficiently.

  Here, compared with the rigidity of the joining flange 31a in the retainer 41 and the roof panel 31 made of aluminum alloy, the rigidity of the vehicle body member 20, which is a steel structural member, is sufficiently high. Compared with the case of joining with the rivet R as shown in FIG. 12, since the presser T from the vehicle interior side is not necessary, the joining position and structure of the roof panel 31 and the vehicle body member can be set relatively freely. Since the degree of freedom of design is high and the joint flange width W1 can be narrower than that of the rivet joint, the appearance quality as a vehicle body is also improved.

  When irradiating the subsequent laser beam Bw, welding can be performed while supplying a filler wire as necessary, and even if a gap is generated between the retainer 41 and the vehicle body member 20, welding failure is avoided. Will be able to.

It is a side view which shows the joining procedure when a pressure roller is arrange | positioned between two laser beams as an example of the joining method of the dissimilar metal by this invention. (A)-(c) is each sectional drawing about the cutting lines a, b, and c in FIG. It is sectional drawing explaining the joining process at the time of interposing a sealing material between a low melting-point material and a high melting-point material. It is sectional drawing explaining the joining process when embossing is formed in the 3rd material. It is sectional drawing explaining the joining process at the time of forming an emboss in 3rd material and interposing a sealing material between a low melting-point material and a high melting-point material. It is the schematic which shows the joining point at the time of applying a laser welding as a welding means, using a hot roller as a heating and pressurizing means. It is the schematic which shows the joining point at the time of applying a resistance seam welding as a welding means, using a hot roller as a heating and pressurizing means. It is the schematic which shows the joining point at the time of using the cylindrical indenter with a built-in heater as a heating and pressurizing means, and applying resistance spot welding as a welding means. It is the schematic which shows the joining point at the time of applying high frequency heating as a heating means, pressurization, and resistance spot welding as a welding means. It is a perspective view which shows the joining structure of the steel vehicle body member and aluminum roof panel by the Example of this invention. It is sectional drawing which shows the joining procedure of the steel vehicle body member and aluminum roof panel shown in FIG. It is a schematic sectional drawing which shows the example of a joining structure by the rivet of a steel vehicle body member and an aluminum roof panel.

Explanation of symbols

1, 23 First plate (steel plate: high melting point material)
2, 31 Second plate (aluminum alloy plate: low melting point material)
3, 41 Third plate (steel plate: high melting point material)
3a Convex part (convex shape)
3b Concave part (concave shape)
S sealing material

Claims (6)

  When the first plate made of a high melting point material and the second plate made of a low melting point material are overlapped and joined, a third plate made of the same high melting point material as the first plate is further added to the second plate. The third plate material is heated, and the second plate material is softened by heat transfer, and the first plate material and the third plate material are cut by pressing the softened second plate material from the third plate material side. A method for joining dissimilar metals, wherein the first and third plate materials are welded together.   The method for joining dissimilar metals according to claim 1, wherein a sealing material is interposed between the first and third plate materials and the second plate material, and the sealing material is cut together with the second plate material.   3. The method for joining dissimilar metals according to claim 1, wherein pressure is applied using a roller having a shape in which a central portion of a contact surface with the plate material protrudes.   The method for joining dissimilar metals according to any one of claims 1 to 3, wherein the third plate member is intermittently heated and pressurized and joined in a stitch shape.   Embossing having a cross-sectional shape having a convex shape protruding toward the second plate material along the joining line of the third plate material, a flat surface having a predetermined width at the center portion, and a concave shape on both sides thereof The method for joining dissimilar metals according to any one of claims 1 to 4, characterized in that is formed intermittently.   The dissimilar metal joining method according to any one of claims 1 to 5, wherein the first and third plate members are steel plates, and the second plate member is an aluminum alloy plate.

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