JPH09155561A - Method for joining different materials such as aluminum-based material and steel-based material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the strength of a joint higher than that of a different material joint bonded by inserting a clad material by adding one or more patch sheets to both sides of an aluminum-based and steel-based materials to be joined and energizing while the materials and the patch sheets are simultaneously pressurized with electrodes. SOLUTION: The method is such that resistance heat is generated on the boundary between a patch sheet 6 and an aluminum based material 1 by adding the patch sheet 6 to the outside of the aluminum based material 1 of a different material joint and energizing them simultaneously with electrodes 3, and that, by the heat thus generated, the aluminum-based material 1 and a steel-based material 2 are bonded through resistance diffusion welding. According to this method, the rigidity of this patch sheet 6 makes the different material joint hard to be deformed even under a high tensile shearing load, and consequently renders high strength of the joint. In addition, with the patch sheet 6 also added to the outside of the steel based material 2, the joined part of the different materials becomes harder to be deformed, enabling such high strength of the joint to be obtained that breaking takes place to the base material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dissimilar material joining technique for joining dissimilar materials between an aluminum-based material made of aluminum or an aluminum alloy and a steel-based material made of carbon steel or stainless steel. Belong to.

[0002]

2. Description of the Related Art When dissimilarly joining an aluminum-based material made of aluminum or an aluminum alloy (hereinafter simply referred to as an aluminum-based material) and a steel-based material such as carbon steel or stainless steel (hereinafter simply referred to as a steel-based material) ,
When aluminum (Al) and steel (Fe) are melt-mixed using a melt-bonding method such as arc welding or lap resistance spot welding, a very brittle intermetallic compound is generated at the interface of the joint, so aluminum and steel are directly joined. It cannot be melt mixed and joined.

Even if melt-mixing and welding can be performed, the produced Al-Fe-based intermetallic compound is extremely brittle, so that a joint having ductile and practical strength cannot be obtained. For this reason, the clad material of the steel-based material and the aluminum-based material is inserted into the joining interface so that the same-type metals face each other, and the aluminum-based material melts the aluminum-based materials and the steel-based material melts the steel-based materials. , A method for completing dissimilar material joining without forming Al-Fe intermetallic compounds is known (for example, Japanese Patent Laid-Open No. 4-55066).

Further, the inventors of the present invention, when joining a thin plate made of an aluminum-based material and a thin plate made of a steel-based material to different materials, use an ordinary thin plate of a steel-based material as a backing plate outside the joint portion (outside of the aluminum-based material). ), Sandwiching a thin plate of aluminum or aluminum alloy based material to be joined with a thin plate of steel based material to be joined and a steel-based backing plate attached to the outside of the joint, and three sheets at the same time. Lap resistance spot welding is performed, and after the aluminum-based material is melted and eliminated in the initial stage of energization, the steel-based material that is the material to be joined and the backing plate made of the steel-based material mounted on the outside of the joint are joined by lap resistance spot welding. We have proposed a method for joining dissimilar materials to join a thin plate of aluminum-based material and a thin plate of steel-based material (Japanese Patent Application No. 6-12
No. 6093).

[0005]

However, FIGS. 9 and 10
As shown in Fig. 2, the method for joining dissimilar materials between the aluminum-based material and the steel-based material, which inserts the clad material at the bonding interface between the steel-based material and the aluminum-based material, inserts the clad material at the bonding interface of the materials to be joined. There was a very troublesome problem in the joining process, which had to be done. Further, since the clad material of the steel-based material and the aluminum-based material to be inserted into the joining interface is very expensive, there is a drawback that the final joining cost becomes high.

Further, when a dissimilar material joint made by inserting a clad material is subjected to a tensile shear test as shown in FIG. 11, since the clad material is inserted between the aluminum-based material and the steel-based material, which are the materials to be joined, The moment corresponding to the plate thickness of the clad material acts, it is easily deformed at the joint as shown in Fig. 12, and fractures at the joint (nugget outer periphery) of the aluminum-based material of the material to be joined, resulting in low strength of dissimilar joints. There was a problem.

The present inventors also proposed (Japanese Patent Application No. 6-126093).
No. 1) was attached to the outside of the aluminum-based material as a backing plate, and after the aluminum-based material was melted and eliminated in the initial stage of energization, it was attached to the outside of the steel-based material and the joint part to be joined. A dissimilar material joining method of joining a thin plate of an aluminum-based material and a thin plate of a steel-based material by joining a backing plate made of a steel-based material by lap resistance spot welding, although high tensile shear strength is exhibited at low cost, There is a problem that the appearance of the dissimilar material joint is not so good because the aluminum-based material is melted and eliminated and the steel-based material and the caulking plate made of the steel-based material are welded, so that the impression of the welding electrode remains.

Further, since the aluminum-based material and the steel-based material, which are the materials to be bonded, are not metallurgically bonded, but are bonded like a rivet by the steel-based material-steel-based material contact plates, the dissimilar material bonding portion is joined. When there is only one point, there is a drawback that the joint rotates around the joint.

The present invention has the problem that the clad material must be inserted into the joining interface of the materials to be joined and that the cost of joining is high due to the use of an expensive clad material of steel-based material and aluminum-based material. In order to solve the above problem, it is possible to join dissimilar materials by using an ordinary aluminum-based material or steel-based material instead of inserting an expensive clad material into the bonding interface.

Further, according to the present invention, a joint strength higher than that of a dissimilar joint joined by inserting the above-mentioned clad material is obtained, the appearance of the joint is good, and the aluminum-based material and the steel-based material to be joined are An object of the present invention is to provide a dissimilar material joining method for joining metallurgically.

[0011]

Means for Solving the Problems When dissimilarly joining an aluminum-based material made of aluminum or an aluminum alloy and a steel-based material made of carbon steel or stainless steel, the aluminum-based material and the steel-based material to be joined By attaching one or more contact plates to both sides of the contact and energizing the material to be bonded and the contact plate while simultaneously applying pressure to the electrodes, the interface between the contact plate and the material to be bonded causes resistance heat generation, and this heat generation causes the material to be bonded. A dissimilar material joining method of an aluminum-based material and a steel-based material, characterized in that a joining portion having high joint strength is obtained by resistance diffusion joining of an aluminum-based material and a steel-based material.

The backing plate is preferably attached to the outside of the aluminum-based material that is the material to be joined, and furthermore, the material to be joined is sandwiched between the aluminum-based material and the steel-based material that are the materials to be joined. It is more preferable to attach one or more plates.

Further, the material of the pad plate is preferably a material which easily generates resistance heat, but it is preferable that the material is equivalent to aluminum or has a lower conductivity than aluminum. The reason for this is that if the current is the same, the amount of resistance heat generated by the contact plate increases.

As described above, it is not possible to directly melt mix aluminum-based materials and steel-based materials to join dissimilar materials, but as a result of intensive research and development by the present inventors, a relatively flat tip shape was obtained. By joining the aluminum-based material and the steel-based material by utilizing the resistance heat generation at the interface between the contact plate and the material to be joined using such electrodes, dissimilar materials can be joined without melting and mixing the aluminum-based material and the steel-based material, Diffusion bonding of aluminum-based materials and steel-based materials by selecting appropriate joining conditions and attachment of the backing plate, and the tensile shear strength is high enough to cause base metal fracture not only in the joints but also in aluminum-based materials. It turns out that

A patch plate 6 is attached to the outer side of the aluminum-based material 1 of the dissimilar material joint portion so that the material to be joined and the patch plate are simultaneously formed by the electrode 3
By applying electric current while applying pressure, the interface between the backing plate 6 and the aluminum-based material 1 that is the material to be joined generates resistance heat,
According to the method of the present invention (FIGS. 1 to 3) in which the aluminum-based material 1 and the steel-based material 2 which are the materials to be bonded are resistance-diffusion bonded by the heat generation, the rigidity of the pad plate 6 causes
Even when a high tensile shear load is applied, the dissimilar material joint portion is less likely to be deformed, and as a result, high joint strength is obtained. Further, as shown in FIG. 2, if the backing plate 6 is attached to the outside of the steel-based material 2 as well, the dissimilar material joint portion becomes more difficult to deform, and in some cases, the dissimilar material joint portion does not break, and the As shown in (1), high joint strength is obtained to the extent that the base material also breaks.

According to the method of the present invention, since an expensive clad material is not used, aluminum-based material and steel-based material can be dissimilarly joined at low cost, and a flat electrode having a relatively tip shape can be obtained. Since it can be bonded even when used, the appearance of the bonded portion is good. Further, since the aluminum-based material and the steel-based material, which are the materials to be bonded, are metallurgically bonded (diffusion bonding), there is no rotation around the bonded portion.

Further, if the joining is carried out under appropriate conditions, the joint strength does not break only at the joint portion, and high joint strength leading to fracture of the base material can be obtained. Therefore, the reliability of the dissimilar joint is very high.
In particular, it is clear that the fatigue strength and impact performance of dissimilar material joints are markedly improved.

On the other hand, the contact plate may be a part of the structure other than the contact plate, and it does not impair the effect of the method of the present invention. In the method of the present invention, aluminum-based material and steel-based material are diffusion-bonded by pressure application by electrodes and resistance heat generation by energization. It is clear that the more the material is polished by the above method, the more it is cleaned with a chemical agent, or the higher the welding pressure is, the more the bondability between the aluminum-based material and the steel-based material is improved.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on examples.

[0020]

【Example】

Example 1 Aluminum material is A5052 plate thickness 1.0 mm
The steel material is SPCC steel plate (cold rolled steel plate) with a thickness of 1.0 mm JI
According to the tensile shear test method of SZ 3136 spot welded joint, a test piece cut into a width of 30 mm and a length of 100 mm was prepared. The backing plate material is an aluminum-based material (A1050 and A505
2), plate thickness with different conductivity such as SPCC steel plate, stainless steel plate
A 1.0 mm material cut into a width of 30 mm and a length of 30 mm was used.

In the example of the present invention, when one patch plate is attached only to the outer side of the aluminum-based material of the dissimilar material joint portion (see FIG. 1), two patch plates are attached only to the outer side of the aluminum-based material of the dissimilar material joint portion. In the case where the backing plate was attached to both sides of the dissimilar material joint portion (see FIG. 2), the comparison example was performed without using the backing plate material or the insert material, and the aluminum-based material was used.
When directly joined to SPCC steel plate (see Fig. 8), when aluminum / steel clad material with aluminum layer 0.5mm, steel layer 0.8mm, and total plate thickness 1.3mm is inserted into the joining interface to join dissimilar materials (see Fig. 9) The case where one or more patch plates are attached only to the steel material side of the dissimilar material joint portion. For these,
Dissimilar materials were joined under the following joining conditions, and the tensile shear loads of the present invention example and the comparative example were compared and examined. FIG. 6 shows the result.

Welding conditions Welding machine: Single-phase AC resistance spot welding machine Electrode: R-type electrode (chromium copper alloy) with 16mmφ and tip curvature radius of 100mm Pressurizing force: 3000N One step constant pressurizing time: 240ms Welding current : 16kA

The present invention example and the comparative example have the same materials to be joined and the joining conditions, but as shown in FIG. 6, the comparative example has a smaller tensile shear load than the inventive example. When the clad material is inserted into the joining interface and joined with dissimilar materials, as described above, when a tensile load is applied, a moment equivalent to the thickness of the clad material acts, so that it is easily deformed at the joint and the aluminum material Fracture (button fracture) at the joint (outer periphery of the nugget).

On the other hand, in the dissimilar material joint of the present invention example, since the dissimilar material joint portion by the contact plate has high rigidity, it is difficult to deform at the joint portion, and the material other than the material to be joined is inserted at the joint interface of the joint. Since the extra moment does not work, even if shear fracture occurs at the dissimilar material joining interface between the aluminum-based material and the steel-based material, higher joint strength can be obtained than in the comparative example in which the clad material is inserted. If a stiffening plate is attached to both sides of the dissimilar material joint to further increase the rigidity, the base material of the aluminum-based material is broken as shown in FIG.

Of course, when the aluminum base material is fractured, it becomes ductile, but even when shear fracture occurs at the dissimilar material joining interface of aluminum material and steel material, it is the same as the ordinary resistance spot welding joint between aluminum materials. It became a ductile fracture. When observing the fracture surface when shear fracture occurs at the dissimilar material joining interface of aluminum material-steel material, no evidence of melting of steel is observed, and there is no evidence of formation of brittle intermetallic compounds, and aluminum solidified and melted at the steel-side interface becomes firm. It was attached. Therefore, it is presumed that the dissimilar material joining method of the aluminum-based material and the steel-based material of the present invention does not directly melt-mix aluminum and steel, but firmly joins metallurgically by metal diffusion of the materials to be joined. .

Example 2 As in Example 1, an aluminum material was used as the material to be joined.
A5052 plate thickness 1.0mm, steel material is SPCC steel plate thickness 1.0mm JI
According to the tensile shear test method of SZ 3136 spot welded joint, a test piece cut into a width of 30 mm and a length of 100 mm was prepared. The backing plate is an aluminum type A5052 plate thickness 1.0 mm
The SPCC steel sheet with a thickness of 1.0 mm was cut into a width of 30 mm and a length of 30 mm.

In the example of the present invention, when one A5052 patch plate is attached only to the outside of the aluminum-based material of the dissimilar material joint,
The A5052 patch plate is attached to the outside of the aluminum-based material of the dissimilar joint, and the SPCC steel plate is attached to the outside of the steel-based material of the dissimilar joint.
This is the case when aluminum / steel clad material with 0.5 mm, steel layer 0.8 mm, and total plate thickness 1.3 mm is inserted into the joining interface and joined with dissimilar materials. About these, the dissimilar materials were joined under the following joining conditions, and the tensile shear loads of the present invention example and the comparative example were compared and examined. FIG. 7 shows the result.

Welding conditions Welding machine: Single-phase AC resistance spot welding machine Electrode: R type electrode (chrome copper alloy) with 16mmφ and 100mm tip radius of curvature Pressurizing force: 3000N One step constant pressurizing time: 140ms to 1040ms Welding current: 8kA ~ 24kA

In dissimilar material joining of aluminum material and SPCC steel sheet, energization time was fixed at 240 ms and set current was 8 kA to 24 kA.
Tensile shear loads were compared between the case of the present invention and the comparative example in which the conventional clad material was inserted when the set current was fixed to 16 kA and the energization time was changed from 140 ms to 1040 ms. As shown in FIG.
In the comparative example, the tensile shear load increases as the set current is increased, but even if a high current of about 24 kA is applied, it is at most 400
It can withstand a tensile shear load of 0 N only.

On the other hand, in the example of the present invention, a joint strength higher than that of the comparative example can be obtained if the set current is the same, and if the set current is increased, the aluminum base material is broken. If the set current is the same, increasing the energization time
After all, the aluminum base material will break.

[0031]

As is apparent from the above description, according to the present invention, it is possible to obtain a dissimilar material joint having a high joint strength at a low cost simply by adding a backing plate without inserting an expensive clad material. In addition, since a relatively flat tip electrode can be used, it is possible to obtain a dissimilar material joint having a good joint appearance.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view illustrating a method of the present invention.

FIG. 2 is a schematic sectional view illustrating the method of the present invention.

FIG. 3 is a schematic sectional view illustrating the method of the present invention.

FIG. 4 is a schematic sectional view illustrating a tensile shear test of a dissimilar material joint according to the method of the present invention.

FIG. 5 is a schematic cross-sectional view illustrating a fracture mode of a dissimilar material joint according to the method of the present invention during a tensile shear test.

FIG. 6 is a diagram showing test results of Example 1.

FIG. 7 is a diagram showing test results of Example 2.

FIG. 8 is a schematic cross-sectional view illustrating the case of directly joining an aluminum-based material and a steel-based material.

FIG. 9 is a schematic sectional view illustrating a conventional dissimilar material joining method in which a clad material is inserted.

FIG. 10 is a schematic cross-sectional view illustrating a dissimilar material bonding joint in which a clad material is inserted.

FIG. 11 is a schematic cross-sectional view illustrating a tensile shear test of a dissimilar material joint joint in which a clad material is inserted.

FIG. 12 is a schematic cross-sectional view illustrating a fracture mode of a dissimilar material joint having a clad material inserted therein during a tensile shear test.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Aluminum-based material, 2 ... Steel-based material, 3 ... Electrode, 4 ... Aluminum layer of clad material, 5 ... Steel layer of clad material, 6
... a patch.

Claims (3)

[Claims] 1. When dissimilarly joining an aluminum-based material made of aluminum or an aluminum alloy and a steel-based material made of carbon steel or stainless steel, the aluminum-based material and the steel-based material, which are materials to be joined, are applied to both sides. An aluminum-based material, characterized in that one or more plates are attached, and current is applied while simultaneously pressing the material to be bonded and the reliance plate to perform resistance diffusion bonding of the aluminum-based material and the steel-based material, which are the materials to be bonded. A method for joining dissimilar materials to steel-based materials. 2. When joining dissimilar materials between an aluminum-based material made of aluminum or an aluminum alloy and a steel-based material made of carbon steel, stainless steel, or the like, one or more pad plates are provided on the side of the aluminum-based material that is the material to be joined. In addition, the material to be welded and the backing plate are simultaneously energized while being pressurized, and the aluminum-based material and the steel-based material are characterized by performing resistance diffusion bonding of the aluminum-based material and the steel-based material that are the materials to be joined. How to join dissimilar materials. 3. The method for joining dissimilar materials between an aluminum-based material and a steel-based material according to claim 1, wherein the material of the patch plate is the same as aluminum or has a lower conductivity than aluminum.