JP7405717B2 - Dissimilar material joining method and joined body - Google Patents

Description

The present invention relates to a dissimilar material joining method and a joined body .

In recent years, in response to global environmental problems caused by exhaust gases, efforts have been made to improve fuel efficiency by reducing the weight of transport vehicles such as automobiles. In order to increase safety in the event of a car body collision without hindering the weight reduction of car bodies as much as possible, we have replaced some of the steel materials traditionally used in car body structures with lighter weight and energy-absorbing materials. Application examples in which light alloy materials such as superior aluminum alloy materials are being used are increasing.

These aluminum alloy materials must be used in combination with steel materials (steel components) such as steel plates or shaped steel that are originally commonly used in the body of ordinary automobiles, unless all parts of the vehicle body are made of aluminum alloy materials. . Therefore, it is inevitably necessary to join dissimilar metals such as aluminum alloy material and steel material (dissimilar metal joining). Such a dissimilar material joining method is disclosed in Patent Document 1

Moreover, an adhesive layer is often provided between the aluminum alloy material and the steel member in order to prevent corrosion (electrolytic corrosion) due to the potential difference between the two and further ensure bonding strength. A bonding method for providing such an adhesive layer is disclosed in Patent Document 2.

Japanese Patent Application Publication No. 2010-207898 JP2015-24436A

However, in the joining method of Patent Document 2, metals do not come into contact with each other in areas where the adhesive is present, so it is necessary to remove the adhesive in advance from the area where the rivet is to be welded. This adhesive removal process is very time-consuming and impractical.
Therefore, it is desirable to apply the so-called weld bond method, in which welding is performed such that the adhesive remains and is removed during spot welding. However, if the weld bond method is applied as is, sparks and dust are likely to be generated from the welded portion, making it difficult to obtain the desired nugget shape, and as a result, the bonding strength decreases. This problem occurs not only when joining dissimilar materials such as aluminum and steel, but also when combining other dissimilar materials.

The present invention has solved the above-mentioned problems, and aims to provide a method for joining dissimilar materials and a joined body that can suppress the generation of dust and perform good spot welding in the weld bonding method using rivets. do.

The present invention consists of the following configuration.
(1) Driving the shaft portion of a rivet having a head and a shaft portion into the first member and penetrating it;
The first member through which the rivet is attached and the second member which can be welded to the rivet are separated by a resin layer between the tip side of the shank of the rivet of the first member and the second member. Place them one on top of the other, sandwiching the
A dissimilar material joining method in which the rivet and the second member are sandwiched between a pair of electrodes, and the resin layer is spot welded while being applied with electricity while being pressurized between the electrodes, while removing the resin layer from between the electrodes,
The rivet includes an annular stepped portion formed along the circumferential direction and protruding in the axial direction at a connection portion with the shaft portion on the back side of the head,
When the rivet is driven into the first member, the annular stepped portion presses the first member, causing the inner peripheral edge of the through hole of the shaft portion in the first member to move toward the second member. forming a protruding annular protrusion;
By applying pressure between the electrodes during the spot welding, a gap is formed between the first member and the second member on the radially outer side of the annular protrusion, and the resin layer is discharged into the gap. spot weld,
Method for joining dissimilar materials.
(2) A first member provided with a pilot hole and an annular protrusion around the periphery of the pilot hole is placed over the second member with a resin layer in between,
Penetrating the shaft portion of the rivet, which has a head and a shaft portion and is weldable to the second member, through the pilot hole of the first member;
A dissimilar material joining method in which the rivet and the second member are sandwiched between a pair of electrodes, and the resin layer is spot welded while being applied with electricity while being pressurized between the electrodes, while removing the resin layer from between the electrodes,
The rivet includes an annular stepped portion formed along the circumferential direction and protruding in the axial direction at a connection portion with the shaft portion on the back side of the head,
By applying pressure between the electrodes during the spot welding, a gap is formed between the first member and the second member on the radially outer side of the annular protrusion, and the resin layer is discharged into the gap. spot weld,
Method for joining dissimilar materials.
(3) A rivet having a head and a shaft,
A first member through which the shaft portion is attached and a second member that can be welded to the rivet are provided with a resin layer between the tip side of the shaft portion of the rivet of the first member and the second member. The rivet and the second member are sandwiched between a pair of electrodes, and the resin layer is spot-welded while being applied with electricity while being pressurized between the electrodes while removing the resin layer from between the electrodes. Used for joining,
The rivet includes an annular stepped part formed along the circumferential direction and protruding in the axial direction at a connection part with the shaft part on the back side of the head part.

According to the present invention, in the weld bonding method using rivets, dissimilar materials can be joined by good spot welding that suppresses the occurrence of dust and the like.

FIGS. 1A and 1B are external perspective views of a rivet used in the method for joining dissimilar materials according to the present invention. FIG. 2 is a process explanatory diagram showing the rivet driving process in steps (A) to (C). FIG. 3(A) is a cross-sectional view of an aluminum material into which rivets are driven, and FIG. 3(B) is a bottom view of FIG. 3(A) seen from below. FIG. 4 is a process explanatory diagram showing how an aluminum material into which rivets have been driven is stacked on a steel material with a resin layer in between. FIG. 5 is a process explanatory diagram showing resistance spot welding of an aluminum material and a steel material using rivets. FIG. 6 is an explanatory diagram showing stepwise (A) to (C) the process from applying pressure between the electrodes to applying electricity. FIG. 7 is a process explanatory diagram showing another method of fixing a rivet to an aluminum material by (A) and (B). FIG. 8 is a sectional view showing another configuration of the dissimilar material joined body shown in FIG. 6. FIG. 9 is a partially enlarged sectional view (A) to (C) showing other shapes of the annular stepped portion of the rivet.

Embodiments of the present invention will be described in detail below with reference to the drawings. In the method for joining dissimilar materials of the present invention, an annular stepped portion protruding in the axial direction is provided on the back side of the head of the rivet used. Here, a dissimilar material joining method is illustrated in which an aluminum material and a steel material are joined using steel rivets, but the combination of materials of each member to be joined is arbitrary.

<Rivet composition>
FIGS. 1A and 1B are perspective views of a rivet used in the method for joining dissimilar materials according to the present invention.
The rivet 11 is made of steel and has a disk-shaped head 13 and a shaft portion 15 coaxially connected to the center of the head 13. The rivet 11 is formed along the circumferential direction so as to surround the shaft part 15 at the connection part with the shaft part 15 on the back side of the head part 13 (inner peripheral part of the annular head back surface 13a), and protrudes in the axial direction. An annular stepped portion 17 is provided. The annular stepped portion 17 has stepped corners, that is, a corner 17a connected to the back surface 13a of the head, a corner 17b connected to the shaft side 15b, and an outer peripheral edge 17c of the protruding tip. The axial section is chamfered into a curved shape.

Although the shaft portion 15 shown in FIGS. 1A and 1B has a cylindrical shape with a constant diameter, it may also have a shape that gradually increases from the base end toward the tip end on the head 13 side. Often, the axial cross section may be elliptical.

The tip surface (shaft tip surface) 15a of the shaft portion 15 is a curved surface that projects in the axial direction. The curved apex 19 of the shank distal end surface 15 a coincides with the central axis L of the shank 15 . Moreover, instead of a curved surface, it may be a conical shape (projection) with the top portion 19 as a protruding tip.

<Steps for joining different materials>
Next, a procedure for joining aluminum and steel to dissimilar materials using the rivet 11 described above will be described.
FIG. 2 is a process explanatory diagram showing the driving process of the rivet 11 in steps (A) to (C).
As shown in FIG. 2A, an aluminum material 23 is placed on a die 21 having a cylindrical upper part, and a rivet 11 is placed above the die 21. An annular recess 21 a is formed on the inner peripheral side of the upper surface of the die 21 . Then, the head 13 of the rivet 11 is driven into the aluminum material 23 using the punch 25.

As the aluminum material 23, 2000 series, 3000 series, 4000 series, 5000 series, 6000 series, 7000 series aluminum alloys, or 1000 series pure aluminum wrought material can be used. From the viewpoint of weldability, aluminum alloys of 5000 series, 6000 series, and 7000 series are particularly preferred. Further, the aluminum material 23 is not limited to a plate material, and may be an extruded member (a pipe material, a hollow, solid, or irregular cross-section shaped material), or a forged material (a plate material, a ribbed material). Further, the surface of the aluminum material 23 may be subjected to various surface treatments such as blasting, etching, and brush polishing as a preliminary treatment. In that case, organic matter on the surface of the aluminum material is removed, improving bonding quality.

As shown in FIG. 2B, when the punch 25 is lowered and the rivet 11 is pushed into the aluminum material 23, the portion of the aluminum material 23 facing the shaft portion 15 is punched out by the shaft portion 15, and this punched portion is punched out by the shaft portion 15. The blank portion 23A falls inside the die 21. Further, the rivet 11 is pressed toward the aluminum material 23 by the punch 25, and the aluminum material 23 is sandwiched between the head 13 and the die 21. As a result, the annular stepped portion 17 of the rivet 11 is pushed into the aluminum material 23, and the aluminum material 23 plastically flows and enters the recess 21a formed on the upper surface of the die 21.

In this way, as shown in FIG. 2C, the shaft portion 15 of the rivet 11 penetrates the aluminum material 23, and the shaft portion tip end surface 15a is exposed on the lower surface of the aluminum material 23. Further, the annular stepped portion 17 formed on the head 13 enters into the aluminum material 23, and the rivet 11 is caulked and fixed to the aluminum material 23. Furthermore, an annular protrusion 26 is formed on the inner peripheral edge of the through hole through which the shaft portion 15 of the aluminum material 23 passes, protruding forward in the insertion direction of the shaft portion 15 .

The driving of the rivet 11 may be performed simultaneously with the press forming process (trimming process) of the aluminum material 23, for example. That is, when press-forming the aluminum material 23, a punch is installed in the press die, or the press die itself is used instead of the punch, and the rivet 11 is punched out at the same time as the press die is lowered. Thereby, the rivet 11 is caulked and fixed to the aluminum material 23. In this state, when the aluminum material 23 is transported to the resistance spot welding line, the rivet 11 is caulked and fixed to the aluminum material 23, so the rivet 11 does not fall during the transportation process. Therefore, the workability of joining can be improved.

3A is a cross-sectional view of the aluminum material 23 into which the rivet 11 is driven, and FIG. 3B is a bottom view seen from below FIG. 3A.
The annular protrusion 26 of the aluminum material 23 shown in FIG. It is formed. That is, the annular protrusion 26 does not protrude from the shaft portion 15. The radially outer side of the annular protrusion 26 of the aluminum material 23 is not affected by the pushing by the annular stepped part 17 of the rivet 11 and the plastic flow into the recess 21a of the die 21 (see FIG. 2), and retains its original shape. This is a flat surface 23a. That is, the flat surface 23a of the aluminum material 23 is recessed by a distance S from the annular protrusion 26.

Therefore, the axial positions of the rivet 11 and the aluminum material 23 in FIG. There is.

FIG. 4 is a process explanatory diagram showing how an aluminum material 23 into which rivets 11 have been driven is stacked on a steel material 29 with a resin layer 27 in between.
A resin layer 27 is formed on one surface of the steel material 29. The resin layer 27 is an adhesive that joins the aluminum material 23 and the steel material 29. Moreover, the resin layer 27 has electrical insulation properties, thereby preventing electrical corrosion due to contact between the aluminum material 23 and the steel material 29, and firmly joining the two.

As the steel material 29, mild steel, high tensile strength steel, etc. can be used. A resin layer 27 is formed on one surface of the steel material 29. The resin layer 27 is an adhesive that joins the aluminum material 23 and the steel material 29. Moreover, the resin layer 27 has electrical insulation properties, thereby preventing electrical corrosion due to contact between the aluminum material 23 and the steel material 29, and firmly joining the two.

The adhesive used for the resin layer 27 may be applied to the steel material 29 in a liquid or viscous state, or may be applied to the aluminum material 23. Further, the resin layer 27 is not limited to being coated with an adhesive, and may be formed by disposing a sheet-like adhesive sheet. When using an adhesive sheet, the adhesive sheet may be adhered to the steel material 29 or the aluminum material 23, or both, in advance, or may be adhered together when the aluminum material 23 and the steel material 29 are stacked. As a result, the resin layer 27 is sandwiched between the surface of the aluminum material 23 on the shank tip end side of the rivet 11 and the surface of the steel material 29.

FIG. 5 is a process explanatory diagram showing how the aluminum material 23 and the steel material 29 are resistance spot welded using the rivet 11.
An aluminum material 23 provided with a rivet 11 and a steel material 29 overlapping the aluminum material 23 are sandwiched between a pair of electrodes 33 and 35 at the position of the rivet 11. Then, while pressurizing one of the electrodes 33 and 35 toward the other by a pressurizing device (not shown), current is applied between the electrodes by a power source device (not shown) (current I). Then, a nugget 37 of a desired size is formed between the shaft end surface 15a of the rivet 11 and the steel material 29.

Here, the process of pressurizing the aluminum material 23 and the steel material 29 between the electrodes and applying current between the electrodes to form the nugget 37 will be described in detail.
FIG. 6 is an explanatory diagram showing stepwise (A) to (C) the process from applying pressure between the electrodes to applying electricity.
As shown in FIG. 6A, the tip surface 15a of the shaft portion of the rivet 11 is pressed against the resin layer 27 by sandwiching the electrodes 33 and 35 shown in FIG. Centered, pushed radially outward. Then, by applying electricity between the electrodes, the resin layer 27 in contact with the tip surface 15a of the shaft portion of the rivet 11 is heated and melted, and either flows radially outward (arrow M) or partially sublimates. . At this time, a slight gap is formed between the annular protrusion 26 and the steel material 29, and the resin layer 27 is smoothly discharged radially outward from this gap. As a result, the resin layer 27 is almost completely discharged from at least the vicinity of the central axis L of the shaft end surface 15a.

As shown in FIG. 6B, in the vicinity of the central axis L, the shaft end surface 15a and the steel material 29 are in close contact with each other without the resin layer 27 intervening between them, and heat generated by energization A nugget 37 is formed by melting both. The nugget 37 grows from the central axis L as a starting point. At this time, the annular protrusion 26 is strongly pressed against the steel material 29 due to the pressure applied between the electrodes (arrow F).

As shown in FIG. 6C, the nugget 37 grows due to the energization, but since the annular protrusion 26 continues to strongly press the steel material 29 on the radially outer side of the shaft portion 15 of the rivet 11, the molten material of the nugget 37 grows. (molten steel) is dammed up and dust generation can be prevented.

In this way, the nugget 37 grows from the central axis L of the shaft portion 15 as a starting point as electricity is applied, and the rivet 11 and the steel material 29 are sufficiently connected while suppressing deviation from the central axis L and generation of dust. can be grown to a size that provides sufficient bonding strength.

As described above, since the rivet 11 is provided with the annular stepped part 17, when the rivet 11 is driven into the aluminum material 23 and attached, the annular stepped part 17 is attached to the inner peripheral edge of the through hole of the shaft part 15 in the aluminum material 23. An annular protrusion 26 is formed on. During spot welding, this annular protrusion 26 forms a gap between the aluminum material 23 and the steel material 29 on the radially outer side of the annular protrusion 26 due to the pressure applied between the electrodes, and the resin layer 27 smoothly flows through this gap. is discharged. Further, by applying electricity between the electrodes, a nugget 37 is generated starting from the central part of the shaft portion 15 where the resin layer 27 is not present, and the annular protrusion 26 acts as a dam on the radially outer side of the shaft portion 15 to generate dust. prevent.

According to this, even when dissimilar materials are joined through the resin layer 27 by resistance spot welding, a nugget of a desired size can be stably formed at the center of the shaft portion 15 without generating sparks or dust. Sufficient bonding strength can be obtained.

Furthermore, since the rivet 11 is caulked with the aluminum material 23 by the annular stepped portion 17, the caulking of the aluminum material 23 and the rivet 11 is applied to the spot welded portion of the steel-to-steel materials of the rivet 11 and the steel material 29. By causing work hardening, it is possible to further apply mutual bonding force (mechanical bonding force). Therefore, due to the synergistic effect of both spot welding and caulking, high joint strength as a joined body of dissimilar materials can be obtained. Furthermore, when the rivet 11 is pushed into the aluminum material 23 and caulked, it is possible to prevent the occurrence of cracks on the aluminum material 23 side.

<Other configuration examples>
In the above example, the rivet 11 is caulked and fixed to the aluminum material 23 by driving the rivet 11 into the aluminum material 23, but the method of fixing the rivet 11 to the aluminum material 23 is not limited to this.
FIG. 7 is a process explanatory diagram showing another method of fixing the rivet 11 to the aluminum material 23, indicated by (A) and (B).

As shown in FIG. 7A, a lower hole 23b with an inner diameter through which the shaft portion 15 of the rivet 11 can pass is previously provided at a portion of the aluminum material 23 where the rivet 11 is to be provided. When forming this pilot hole 23b, for example, using the die 21 shown in FIG. 2 and a punch having the outer shape of the annular stepped portion 17 of the rivet 11, First, an annular protrusion 26 is formed on the periphery of the pilot hole 23b. Then, as shown in FIG. 7(B), the rivet 11 is fixed to the aluminum material 23 by passing the shaft portion 15 of the rivet 11 through the pilot hole 23b using a press or the like.

The annular protrusion 26 of the lower hole 23b may be formed so as to protrude from the aluminum material 23 after the rivet 11 is fixed, and the method of forming the annular protrusion 26 is not limited.

For example, when the aluminum material 23 is a car body structural material, caulking the rivet 11 to the aluminum material 23 by pressing may be performed during the press molding process of the car body. Moreover, separately from such a press forming process, it may be carried out in a process before or after the press forming process, for example, in the process of manufacturing an aluminum plate.

FIG. 8 is a sectional view showing another configuration of the dissimilar material joined body shown in FIG. 6.
Here, another steel material 30 is stacked on the opposite side of the steel material 29 from the aluminum material 23 side. According to this configuration, by overlapping the plurality of steel materials 29 and 30 and spot welding them to the rivet 11, the three materials can be easily joined by one welding. By providing a plurality of steel materials 29 and 30, the strength of the joined body can be improved and the range of application of dissimilar material joining can be expanded. Note that the number of steel plates may be three or more, and the plate thicknesses may be the same or different. Similarly, the number and thickness of the aluminum material 23 are arbitrary as long as the annular protrusion 26 can be formed.

FIG. 9 is a partially enlarged sectional view (A) to (C) showing other shapes of the annular stepped portion of the rivet.
The annular stepped portion 17 of the rivet 11 is not limited to the shape shown in FIG. 1(B). As shown in FIG. 9A, the annular stepped portion 17A may have a shape in which the annular corners 17a, 17b and the annular corner 17c are at right angles in the axial cross section. In this case, the bite of the aluminum material into the rivet 11 is improved, and the caulking joint strength can be improved.

Further, as shown in FIG. 9B, the annular stepped portion 17B extends radially outward from the corner 17b of the shaft side surface 15b on the head back surface 13a side toward the shaft end surface 15a of the rivet 11. The protrusion may be an annular protrusion having an inclined surface 17d that spreads out, and a cylindrical surface 17e extending in the axial direction from the back surface 13a of the head, with a corner 17c formed at the tip. In this case, as shown in FIG. 7B, when the annular stepped portion 17B is pressed against the aluminum material 23, the aluminum material enters between the cylindrical surface 17e and the shaft side surface 15b due to plastic flow. A portion of the protrusion including the corner 17c deforms radially outward and bites into the aluminum material 23. Thereby, the rivet 11 and the aluminum material 23 can be caulked more firmly.

As shown in FIG. 9C, the annular stepped portion 17C extends in the axial direction from the above-mentioned inclined surface 17d and the back surface 13a of the head, and expands radially outward toward the shank tip surface 15a. It may be an annular projection having an inclined surface 17f and a corner 17c formed at the tip. In this case, the angle of the corner portion 17c in the axial cross section is smaller than that of the annular stepped portion 17B, and it bites into the aluminum material 23 better, resulting in a more strongly crimped state.

<Rivet surface treatment>
Next, a process for forming a film on the surface of the rivet 11 will be explained.
It is preferable to provide the surface of the rivet 11 with a zinc-rich eutectic nickel plating film having a nickel eutectic ratio of, for example, 13 to 18%.
The zinc-high eutectic nickel plating film preferably has a thickness of 5 to 10 μm, and can have excellent corrosion resistance and heat resistance. Thereby, electrolytic corrosion can be effectively prevented.

Further, it is preferable to further provide a chemical conversion coating on the zinc highly eutectic nickel plating coating of the rivet 11. This chemical conversion coating may be a chromate coating obtained by subjecting the surface of a rivet plated with zinc and high eutectic nickel to chromate treatment (JIS H 0201).
The chromate film is thinner than paints, etc., and can ensure high corrosion resistance and heat resistance. In addition, the adhesion of the paint is improved in electrodeposition coating after joining dissimilar materials.
Furthermore, instead of the chromate film, a zircon-based chemical conversion film may be formed. Examples of zircon-based chemical conversion treatments include conversion treatment using zirconium phosphate. By using a zircon-based chemical conversion coating, it is possible to achieve a chromium-free treatment.

The present invention is not limited to the embodiments described above, and those skilled in the art may combine the configurations of the embodiments with each other, or make changes and applications based on the description of the specification and well-known techniques. This is the intended purpose of the invention and falls within the scope for which protection is sought.

As mentioned above, the following matters are disclosed in this specification.
(1) Driving the shaft portion of a rivet having a head and a shaft portion into the first member and penetrating it;
The first member through which the rivet is attached and the second member which can be welded to the rivet are separated by a resin layer between the tip side of the shank of the rivet of the first member and the second member. Place them one on top of the other, sandwiching the
A dissimilar material joining method in which the rivet and the second member are sandwiched between a pair of electrodes, and the resin layer is spot welded while being applied with electricity while being pressurized between the electrodes, while removing the resin layer from between the electrodes,
The rivet includes an annular stepped portion formed along the circumferential direction and protruding in the axial direction at a connection portion with the shaft portion on the back side of the head,
When the rivet is driven into the first member, the annular stepped portion presses the first member, causing the inner peripheral edge of the through hole of the shaft portion in the first member to move toward the second member. forming a protruding annular protrusion;
By applying pressure between the electrodes during the spot welding, a gap is formed between the first member and the second member on the radially outer side of the annular protrusion, and the resin layer is discharged into the gap. spot weld,
Method for joining dissimilar materials.
According to this dissimilar material joining method, the resin layer can be reliably removed from the interface between the rivet and the second member, and the rivet and the second member can be satisfactorily spot-welded without causing dust. Further, by driving the rivet into the first member, the rivet can be prevented from falling off, and handling performance and welding performance can be improved.

(2) A first member provided with a pilot hole and an annular protrusion around the periphery of the pilot hole is placed over the second member with a resin layer in between,
Penetrating the shaft portion of the rivet, which has a head and a shaft portion and is weldable to the second member, through the pilot hole of the first member;
A dissimilar material joining method in which the rivet and the second member are sandwiched between a pair of electrodes, and the resin layer is spot welded while being applied with electricity while being pressurized between the electrodes, while removing the resin layer from between the electrodes,
The rivet includes an annular stepped portion formed along the circumferential direction and protruding in the axial direction at a connection portion with the shaft portion on the back side of the head,
By applying pressure between the electrodes during the spot welding, a gap is formed between the first member and the second member on the radially outer side of the annular protrusion, and the resin layer is discharged into the gap. spot weld,
Method for joining dissimilar materials.
According to this dissimilar material joining method, the resin layer can be reliably removed from the interface between the rivet and the second member, and the rivet and the second member can be satisfactorily spot-welded without causing dust. In addition, the process of inserting the rivet into the pilot hole of the first member can be performed at any timing, such as during the press-forming process of the first member, or separately from the press-forming process, or before or after the press-forming process, so there is freedom in the process. You can improve your degree.

(3) The method for joining dissimilar materials according to (1) or (2), in which a member of the same type as the second member is further overlapped and spot welded on the opposite side of the first member in the second member.
According to this dissimilar material joining method, by providing a plurality of steel materials, the strength of the joined body can be improved and the range of application of dissimilar material joining can be expanded.

(4) The method for joining dissimilar materials according to any one of (1) to (3), wherein the rivet is provided with a zinc-rich eutectic nickel plating film.
According to this dissimilar material joining method, the rivet can be made to have excellent corrosion resistance and heat resistance.

(5) The method for joining dissimilar materials according to (4), further comprising a chemical conversion film that covers the zinc-high eutectic nickel plating film of the rivet.
According to this method of joining dissimilar materials, high corrosion resistance and heat resistance can be ensured, and the adhesion of paint becomes good in electrodeposition coating after joining dissimilar materials.

(6) The method for joining dissimilar materials according to (5), wherein the chemical conversion film is a chromate film.
According to this dissimilar material joining method, since it is a widely known process, a good film can be stably obtained even under various conditions.

(7) The method for joining dissimilar materials according to (5), wherein the chemical conversion film is a zirconium-based chemical conversion film.
According to this dissimilar material joining method, the chemical conversion film can be formed by a chromium-free treatment.

(8) A rivet having a head and a shaft,
A first member through which the shaft portion is attached and a second member that can be welded to the rivet are provided with a resin layer between the tip side of the shaft portion of the rivet of the first member and the second member. The rivet and the second member are sandwiched between a pair of electrodes, and the resin layer is spot-welded while being applied with electricity while being pressurized between the electrodes while removing the resin layer from between the electrodes. Used for joining,
A rivet comprising an annular stepped part formed along the circumferential direction and protruding in the axial direction at a connection part with the shaft part on the back side of the head part. According to this rivet, the resin layer is removed from the interface with the second member. It can be reliably removed and spot welded to the second member without causing dust. This makes it possible to improve the joint strength when joining dissimilar materials.

11 Rivet 13 Head 13a Head back surface 15 Shaft 15a Shaft end surface 15b Shaft side surface 17, 17A, 17B, 17C Annular stepped portion 17a Corner 17b Corner 17c Corner 17d Inclined surface 17e Cylindrical surface 17f Inclined surface 19 Top 21 Die 21a Recess 23 Aluminum material (first member)
23a Flat surface 23b Prepared hole 25 Punch 26 Annular protrusion 27 Resin layer 29 Steel material (second member)
30 Steel materials (same type of members)
31 Outer periphery 33, 35 Electrode 37 Nugget

Claims (9)

Driving the shaft portion of the rivet having a head and a shaft portion into the first member to penetrate it;
The first member through which the rivet is attached and the second member which can be welded to the rivet are separated by a resin layer between the tip side of the shank of the rivet of the first member and the second member. Place them one on top of the other, sandwiching the
A dissimilar material joining method in which the rivet and the second member are sandwiched between a pair of electrodes, and the resin layer is spot welded while being applied with electricity while being pressurized between the electrodes, while removing the resin layer from between the electrodes,
The rivet includes an annular stepped portion formed along the circumferential direction and protruding in the axial direction at a connection portion with the shaft portion on the back side of the head,
When the rivet is driven into the first member, the annular stepped portion presses the first member, causing the inner peripheral edge of the through hole of the shaft portion in the first member to move toward the second member. forming a protruding annular protrusion;
By applying pressure between the electrodes during the spot welding, a gap is formed between the first member and the second member on the radially outer side of the annular protrusion, and the resin layer is discharged into the gap. spot weld,
Method for joining dissimilar materials. A first member provided with a pilot hole and an annular protrusion around the peripheral edge of the pilot hole is placed over the second member with a resin layer in between,
Penetrating the shaft portion of the rivet, which has a head and a shaft portion and is weldable to the second member, through the pilot hole of the first member;
A dissimilar material joining method in which the rivet and the second member are sandwiched between a pair of electrodes, and the resin layer is spot welded while being applied with electricity while being pressurized between the electrodes, while removing the resin layer from between the electrodes,
The rivet includes an annular stepped portion formed along the circumferential direction and protruding in the axial direction at a connection portion with the shaft portion on the back side of the head,
By applying pressure between the electrodes during the spot welding, a gap is formed between the first member and the second member on the radially outer side of the annular protrusion, and the resin layer is discharged into the gap. spot weld,
Method for joining dissimilar materials. 3. The method for joining dissimilar materials according to claim 1, wherein a member of the same type as the second member is further overlapped and spot welded on the opposite side of the first member in the second member. The method for joining dissimilar materials according to any one of claims 1 to 3, wherein the rivet is provided with a zinc-high eutectic nickel plating film. 5. The method for joining dissimilar materials according to claim 4, further comprising a chemical conversion film that covers the zinc-high eutectic nickel plating film of the rivet. 6. The method for joining dissimilar materials according to claim 5, wherein the chemical conversion film is a chromate film. 6. The method for joining dissimilar materials according to claim 5, wherein the chemical conversion coating is a zirconium-based chemical conversion coating. The first member is used in the method for joining dissimilar materials according to any one of claims 1 to 7, and is attached to the rivet having a head and a shaft, and the shaft of the rivet passing through the rivet. A conjugate comprising:
The rivet has an annular stepped part formed along the circumferential direction and protrudes in the axial direction at a connection part with the shaft part on the back side of the head,
The first member has an annular protrusion protruding forward in the direction of insertion of the shaft at an inner peripheral edge of a through hole through which the shaft of the first member passes,
The rivet is fixed so as to form a gap between the first member and the second member on the radially outer side of the annular protrusion by pressurization between the electrodes during the spot welding.
zygote. The first member is used in the method for joining dissimilar materials according to any one of claims 1 to 7, and is attached to the rivet having a head and a shaft, and the shaft of the rivet passing through the rivet. A conjugate comprising:
The rivet has an annular stepped part formed along the circumferential direction and protrudes in the axial direction at a connection part with the shaft part on the back side of the head,
The first member has an annular protrusion protruding forward in the direction of insertion of the shaft at an inner peripheral edge of a through hole through which the shaft of the first member passes;
The annular protrusion is formed to be equal to or lower than the outer peripheral edge of the shaft end surface of the shaft,
The radially outer side of the annular protrusion has a recessed surface from the annular protrusion.
zygote.

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