JP2006198679A - Different kind of metal joining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To a method for joining different metals, in which an oxide film is removed without applying much calorie even when the oxide film is deposited on a surface of either material when overlapping and joining two different metals, and as a result, generation of intermetallic compounds on a joint interface is suppressed to be small, thereby improving the joint strength. <P>SOLUTION: When overlapping and joining a galvanized steel sheet 1 and an aluminum alloy 2 of the kind different from the galvanized steel sheet 1 with each other, eutectic melting is made to cause on an interface between the aluminum alloy 2 and a zinc layer 6 of the galvanized steel sheet 1 by the resistance spot welding, and newly generated faces of the galvanized steel sheet 1 and the aluminum alloy 2 are joined with each other while removing an oxide film without applying much calorie, and suppressing generation of intermetallic compounds on the joint interface. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a bonding method for different kinds of materials used for overlapping and bonding two different kinds of materials.

In general, when joining an aluminum alloy and steel, high hardness and brittle intermetallic compounds such as Fe ₂ Al ₅ and FeAl ₃ are generated at the joint interface, so control is necessary to ensure sufficient joint strength. is required. However, a dense and strong oxide film is formed on the surface of the aluminum alloy. To remove the oxide film, it is effective to input a large amount of heat at the time of bonding. There has been a problem that the intermetallic compound grows at the interface and the bonding strength decreases.

  Therefore, mechanical joining using bolts, rivets, etc. has been performed for joining aluminum alloys and steel. However, in this case, there is a disadvantage that the weight and cost increase. There are also joining methods such as hot rolling, but friction welding is suitable for joining rotating bodies with good symmetry, and its use is limited. Explosive welding and hot rolling are equipment It was not preferable in terms of manufacturing efficiency.

  Conventionally, in order to solve the above-mentioned problem in joining different kinds of materials, as described in Japanese Patent Laid-Open No. 4-127773, it is made of the same two kinds of materials as one and the other. Prepare a clad material, and perform resistance welding by interposing the clad material so that the same kind of materials are in contact with each other between the one and the other materials. At this time, control the energization time to be 10 ms or less. Some have joined one and the other.

Further, as described in JP-A-6-039558, in joining an aluminum alloy and steel, an aluminum alloy or pure aluminum having an aluminum content of 20% by weight or more is formed on the surface of the steel to a thickness of 2 μm or more. By plating and resistance welding with the aluminum alloy and steel overlapped so that the plating layer is in contact with the aluminum alloy, the plating layer is preferentially melted, and the two are joined together with almost no melting of the steel base material. There was something to do.
JP-A-4-127773 Japanese Patent Laid-Open No. 6-039558

  However, in the conventional joining of different kinds of materials as described above, in the method using the clad material made of the same two kinds of materials as the dissimilar materials, the joining of the two members becomes the joining of the three members, and the clad material Since it itself is manufactured by joining different materials, the manufacturing conditions are severe, and it is difficult to obtain a low-cost and stable performance clad material.

  Also, in the method using steel plated with aluminum, a brittle intermetallic compound is generated at the interface between the plating layer and the steel due to heat input when joining the plating layer and the aluminum alloy, and the portion is destroyed. There was a problem that could occur.

  The present invention has been made paying attention to the above-described conventional problems, and when two different types of materials are stacked and joined, even if an oxide film is formed on the surface of any of the materials, The oxide film can be removed without applying a large amount of heat. As a result, the formation of intermetallic compounds at the joint interface is suppressed, and the new surfaces of both materials are firmly joined together, resulting in improved joint strength. It is an object of the present invention to provide a method for joining different kinds of materials.

  In the method for joining different materials of the present invention, when a first material and a second material of a different type from the first material are overlapped and joined, the first material and the second material are joined. In addition, a third material different from these two kinds of materials is interposed. Then, by resistance spot welding performed by sandwiching the first material and the second material from both sides, between at least one of the first material and the second material and the third material The first material and the second material are joined by causing eutectic melting using resistance spot welding at the interface, and the above structure is a means for solving the conventional problems.

  According to the bonding method of different materials of the present invention, when two different kinds of materials are overlapped and bonded, even if an oxide film is formed on the surface of any material, utilizing resistance spot welding, Both materials can be joined while removing the oxide film at a low temperature. Therefore, it is possible to control the bonding interface temperature and suppress the formation of intermetallic compounds, and it is possible to obtain a strong bonding state between the new surfaces of both materials, thereby realizing improved joint strength. A very good effect is possible.

  In the bonding method of different materials of the present invention, a configuration in which the material covered by at least one of the first material and the second material is the third material can be adopted. As a preferred embodiment of the material, a configuration in which the third material is a material plated on at least one of the first material and the second material can be adopted. In this case, since the step of sandwiching the third material between the first material and the second material is omitted, the number of processing steps is reduced and the working efficiency is improved.

  At this time, in the bonding method of different materials of the present invention, at least one of the first material and the second material is a galvanized steel sheet, and zinc of the galvanized steel sheet is a third material. In this case, a normal rust-proof steel sheet can be used as it is without performing a new plating process.

  Furthermore, in the method for joining dissimilar materials according to the present invention, the zinc of the galvanized steel sheet, more specifically, the zinc on the joint surface of the galvanized steel sheet with at least the mating material is non-alloyed zinc that is not alloyed with iron. In this case, both materials can be bonded while suppressing the formation of intermetallic compounds at the bonding interface between the two materials, and a high bonding strength can be obtained.

  Furthermore, in the joining method of different materials of the present invention, the surface opposite to the joining surface of the galvanized steel sheet can be formed of alloyed zinc alloyed with iron, in this case, When resistance spot welding is performed with the electrode abutting against the joint surface of the galvanized steel sheet, the amount of zinc deposited on the electrode tip can be reduced, thereby improving the life of the electrode. it can.

  Furthermore, in the joining method of different materials of the present invention, the opposite surface of the joining surface of the galvanized steel sheet can be a non-plated surface that has not been plated. When resistance spot welding is performed with the electrode brought into contact with the non-plated surface, zinc does not adhere to the tip of the electrode, thereby further improving the life of the electrode.

  Moreover, in the joining method of the dissimilar materials of this invention, when the 1st material is steel and the 2nd material is an aluminum alloy, the material which forms a low melting point eutectic with an aluminum alloy is used as a 3rd material. be able to. In this case, examples of the material that forms the low melting point eutectic with the aluminum alloy include zinc (Zn), copper (Cu), tin (Sn), silver (Ag), and nickel (Ni). Furthermore, in the present invention, the third material need not be limited to the pure metal as described above, and eutectic metal includes both binary alloys and ternary alloys, and therefore, at least one of these metals. An alloy containing may be used.

  A resistance spot is formed by interposing a material (third material) that forms a low-melting point eutectic with the aluminum alloy as described above between the steel (first material) and the aluminum alloy (second material). By welding, both materials are joined while removing the oxide film on the surface of the aluminum alloy at a low temperature, and at this time, the formation of intermetallic compounds is suppressed and a new joined surface of both materials is obtained. be able to.

  Furthermore, in the method for joining dissimilar materials of the present invention, joining can be performed using a resistance spot welding apparatus in which the tip of at least one of the pair of electrodes forms a curved surface including a spherical shape. . In this case, for example, when the steel as the first material and the aluminum alloy as the second material are joined, the oxide film on the surface of the aluminum alloy is pressed by pressurizing the tip portion with a curved electrode shape. Is effectively destroyed and the eutectic melt generated between the aluminum alloy and the third material is effectively discharged to the periphery of the joint to obtain a strong joined state between the new surfaces of the steel and the aluminum alloy. Can do.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to a following example.

  In this example, when the galvanized steel sheet as the first material and the aluminum alloy as the second material are joined by resistance spot welding, a galvanized steel sheet as a third material interposed between the two is used. Using the zinc layer, the eutectic reaction between the aluminum alloy and zinc was caused by utilizing the eutectic point P in the Al—Zn binary phase diagram of FIG. 3 to join the galvanized steel sheet and the aluminum alloy.

  That is, as shown in FIG. 1, a galvanized steel sheet 1 having a thickness of 0.55 mm and a 6000 series aluminum alloy 2 having a thickness of 1.0 mm are used, and a zinc layer (third material) 3 of the galvanized steel sheet 1 is used. The thickness of the galvanized steel sheet was about 5 μm, and the galvanized steel sheet 1 and the aluminum alloy 2 were stacked one above the other.

  Then, in the AC power source type resistance spot welding apparatus, the galvanized steel sheet 1 and the aluminum alloy 2 are sandwiched from above and below by a pair of electrodes 11, 12 connected to the power source 10. Resistance spot welding was performed at 120 kgf.

  At this time, in the joining method, in the resistance spot welding apparatus, as shown in FIG. 4 (b), the electrode 11 in contact with the galvanized steel sheet 1 has its tip portion cut away horizontally from the conical head. This was used as a cone electrode so as to have a shape, and the electrode 12 in contact with the aluminum alloy 2 was used as a dome electrode so that the tip portion thereof was a spherical surface which is one of curved surfaces.

  Next, a change in the state of the bonding interface in the bonding process will be described in detail with reference to FIG.

  As shown in FIG. 2A, in the galvanized steel sheet 1 as the first material, the zinc layer 3 is a third material. Moreover, the oxide film 4 is formed in the surface in the aluminum alloy 2 which is a 2nd material. And as shown in FIG.2 (b), the galvanized steel plate 1 and the aluminum alloy 2 are piled up and down, and both are closely_contact | adhered.

  Next, when the galvanized steel sheet 1 and the aluminum alloy 2 are sandwiched from above and below by the pair of electrodes 11 and 12 having the tip shape described above and resistance spot welding is performed in this state, as shown in FIG. In addition, a fracture portion 4a is formed in the oxide film 4 on the surface of the aluminum alloy 2 due to the pressure applied by the electrodes 11 and 12 and the relative displacement of the material due to thermal expansion, whereby the zinc layer 3 of the galvanized steel sheet 1 and the aluminum alloy 2 And eutectic melting of both occurs according to the temperature at the time of joining.

  Then, as shown in FIG. 2 (d), as the eutectic melting occurs, the oxide film 4 together with the eutectic liquid phase 5 of the aluminum alloy and zinc is discharged around the joint, and as a result, As shown in FIG. 2 (e), the galvanized steel sheet 1 and the aluminum alloy 2 are joined to each other at their new surfaces.

  As described above, in the above-described joining method of different materials, resistance spot welding is performed on the overlapped galvanized steel sheet 1 and the aluminum alloy 2, thereby applying the pressure applied by both the electrodes 11 and 12 and the relative displacement of the material due to thermal expansion. The destruction of the oxide film 4 occurs, the eutectic reaction is promoted, and the oxide film 4 is removed at a low temperature without applying a large amount of heat.

  That is, since the bonding interface temperature can be controlled, the formation of intermetallic compounds can be suppressed, and the galvanized steel sheet 1 and the aluminum alloy 2 can be firmly bonded.

  Moreover, in the joining method of different materials mentioned above, since the zinc layer 3 plated on the galvanized steel sheet 1 is the third material, for example, a step of sandwiching the third material between the steel sheet and the aluminum alloy. As a result, the number of processing steps is reduced and the working efficiency is improved, and a normal rust-proof steel sheet can be used as it is without performing a new plating process.

  Further, in the above-described bonding method of different materials, the electrode 12 in contact with the aluminum alloy 2 is a dome electrode (an electrode having a spherical tip), so that the pressure at the time of bonding can be obtained by applying pressure using the electrode shape. By effectively destroying the oxide film 4 of the aluminum alloy, the eutectic melt generated between the aluminum alloy and the zinc layer 3 can be effectively discharged around the joint, and the galvanized steel sheet 1 and the aluminum alloy This can contribute to stronger joining of the two new surfaces.

  Here, as a comparative example, as shown in FIG. 4 (a), using a resistance spot welding apparatus in which a pair of electrodes 21 and 22 are both cone electrodes, Aluminum alloy 2 was joined. Table 1 shows the bonding conditions (electrode shape) and the results of the strength test of the comparative example and the example.

  In both the comparative example and the example, eutectic melting occurred between the zinc layer 3 and the aluminum alloy 2, but as shown in Table 1, in the comparative example in which the pair of electrodes are both cone electrodes, It was found that the eutectic liquid phase 5 and the oxide film 4 were not discharged well to the surroundings, resulting in the eutectic liquid phase and zinc remaining at the bonding interface, and the bonding strength was not sufficient.

  On the other hand, in the embodiment in which one electrode 11 is a cone electrode and the other electrode 12 is a dome electrode, the eutectic liquid phase 5 and the oxide film 4 are discharged very well around the joint. As a result, it was confirmed that sufficient bonding strength was obtained. Note that it is naturally effective to use both electrodes as dome electrodes in order to discharge the eutectic liquid phase 5 and the oxide film 4 satisfactorily.

  FIG. 5 is a diagram for explaining another embodiment of the bonding method of different materials of the present invention. In this embodiment, a galvanized steel sheet 6 that is a first material in which different surfaces are coated on the joining surface and the opposite surface, and an aluminum alloy 2 that is a second material are joined.

  The galvanized steel sheet 6 forms a non-alloyed galvanized layer 7 that is not alloyed with iron, for example, by hot dip galvanizing or electrogalvanizing on the joint surface (lower surface in the figure) with the aluminum alloy 2. The zinc of the non-alloyed zinc plating layer 7 is used as the third material, and the alloyed zinc plating layer 8 alloyed with iron is formed on the opposite surface of the joining surface by, for example, alloying hot dip galvanizing. Is.

  In the resistance spot welding apparatus, the galvanized steel sheet 6 and the aluminum alloy 2 are polymerized so that the joint surface of the galvanized steel sheet 6, that is, the surface formed by the non-alloyed galvanized layer 7 and the aluminum alloy 2 are in contact with each other. These were sandwiched between a pair of upper and lower electrodes 11 and 12, and resistance spot welding was performed.

  In this embodiment, eutectic melting occurs at the bonding interface between the aluminum alloy 2 and the non-alloyed zinc plating layer 7, and the non-alloyed zinc (7) that is not alloyed with iron is Compared with alloyed zinc (8) alloyed with iron, the eutectic reaction is surely promoted at a lower temperature, so that it is possible to perform the joining while suppressing the formation of intermetallic compounds at the joining interface, As a result, the joint strength can be improved.

  Further, when the resistance spot welding is performed by forming the alloyed galvanized layer 8 alloyed with iron on the surface opposite to the joint surface of the galvanized steel sheet 6, that is, the surface where the electrode 11 abuts, Compared with the case where non-alloyed zinc plating (7) that is not alloyed with iron is applied to the surface, the amount of zinc or the like attached to the electrode 11 can be reduced, and thereby the life of the electrode can be improved. .

  FIG. 6 is a view for explaining still another embodiment of the method for joining different materials of the present invention. In this embodiment, the galvanized steel sheet 9 which is the first material plated only on the joining surface and the aluminum alloy 2 which is the second material are joined.

  The galvanized steel sheet 9 forms a non-alloyed galvanized layer 7 that is not alloyed with iron, for example, by hot dip galvanizing or electrogalvanizing on the joint surface (lower surface in the figure) with the aluminum alloy 2. The zinc of the non-alloyed zinc plating layer 7 is the third material, and the opposite surface of the joint surface is a non-plated surface that is not plated.

  In this embodiment, as in the previous embodiment, eutectic melting occurs at the bonding interface between the aluminum alloy 2 and the non-alloyed galvanized layer 7 and is not alloyed with iron. In the non-alloyed zinc (7), the eutectic reaction is surely promoted at a low temperature, so that the joining can be performed while suppressing the formation of intermetallic compounds at the joining interface, and as a result, the joint strength is improved. Can do.

  In addition, since the surface opposite to the joint surface of the galvanized steel sheet 6, that is, the surface with which the electrode 11 abuts is a non-plated surface, adhesion of zinc or the like to the electrode 11 is eliminated when resistance spot welding is performed. Further improvement of the service life can be achieved.

It is side explanatory drawing which shows one Example in the joining method of the dissimilar material of this invention. FIG. 2 is a cross-sectional view (a) to (e) for sequentially explaining a change in state of a bonding interface in a bonding process of different materials shown in FIG. 1. It is a binary system phase diagram of Al-Zn. It is the side view (a) explaining the electrode shape of a comparative example, and the side view (b) explaining the electrode shape of an Example. It is side explanatory drawing which shows the other Example in the joining method of the dissimilar material of this invention. It is side explanatory drawing which shows other Example in the joining method of the dissimilar material of this invention.

Explanation of symbols

1 Galvanized steel sheet (first material)
2 Aluminum alloy (second material)
3 Zinc layer (third material)
6 Galvanized steel sheet (first material)
7 Non-alloyed galvanized layer (third material)
8 Alloyed galvanized layer 9 Galvanized steel sheet (first material)
11 Electrode: Cone electrode 12 Electrode: Dome electrode

Claims (9)

  When the first material and a second material of a different type from the first material are overlapped and joined, the two materials are different between the first material and the second material. A third material is interposed, and eutectic melting is caused at the interface between at least one of the first material and the second material and the third material by resistance spot welding. A method for joining different materials, comprising joining the first material and the second material.   The method for joining different kinds of materials according to claim 1, wherein the material covered with at least one of the first material and the second material is the third material.   The method for joining different types of materials according to claim 2, wherein the third material is a material plated on at least one of the first material and the second material.   The material of at least one of the first material and the second material is a galvanized steel sheet, and zinc of the galvanized steel sheet is a third material. Of joining different types of materials.   The method for joining different materials according to claim 4, wherein zinc of the galvanized steel sheet is non-alloyed zinc that is not alloyed with iron.   6. The method for joining dissimilar materials according to claim 4 or 5, wherein a surface opposite to the joining surface of the galvanized steel sheet is formed of alloyed zinc alloyed with iron.   6. The method for joining dissimilar materials according to claim 4 or 5, wherein a surface opposite to the joining surface of the galvanized steel sheet is a non-plating surface.   The first material is steel, the second material is an aluminum alloy, and the third material is a material that forms a low-melting eutectic with the aluminum alloy. The joining method of the dissimilar material in any one.   The dissimilar metal according to any one of claims 1 to 8, wherein joining is performed using a resistance spot welding device in which a tip portion of at least one of the pair of electrodes forms a curved surface. Joining method.

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