JP2006088174A - Method for joining dissimilar materials - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for joining dissimilar materials, which method can join an aluminum based welding material and a ferrous welding material without using a soldering material and a flux, and can easily join the dissimilar materials at a low cost. <P>SOLUTION: The aluminum based welding material (plate 2) made of aluminum or aluminum alloy and the ferrous welding material (steel plate 1) are welded by MIG (metal inert gas) welding. The steel plate 1 is provided with an aluminum based coating layer (soldered layer), composed of aluminum or aluminum alloy, on its surface. The aluminum based plate 2 is laid on the steel plate 1 so as to overlap each other at their end portions. The overlapped portion 3 is welded by AC MIG welding. As a result, the aluminum based plate 2 and the steel plate 1 are joined by melting the aluminum based coating layer and the aluminum based plate 2 at the overlapped portion 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a dissimilar material joining method for obtaining a composite structure of an aluminum-based material and an iron-based material used as various structural materials for automobiles.

Various structural materials for automobiles use some aluminum-based materials to reduce their weight. For this reason, development of a method for joining different materials of iron-based materials and aluminum-based materials is desired. . As a conventional dissimilar material joining method, brazing using an aluminum brazing material is common (Patent Documents 1 and 2, Non-Patent Document 1). When a fusion welding method such as TIG welding or laser welding, which is generally used as a method for joining similar materials, is applied to the dissimilar material joining of an aluminum-based welded material and an iron-based welded material, A brittle Al-Fe intermetallic compound such as FeAl ₃ or Fe ₂ Al ₅ is formed at the interface with the iron-based material, and this significantly reduces the bonding strength between the aluminum-based welded material and the iron-based welded material. It is because it makes it. In addition, as MIG welding, there is a MIG welding example in which pure aluminum and a bare steel plate are used with a DC pulse power source using a flux cored wire having an effect of removing an oxide film as an electrode wire (Non-patent Document 2). For this aluminum, welding is possible by using a special wire, but in order to suppress the above-mentioned brittle intermetallic compound, various construction considerations are necessary, and the construction condition range is narrow.

  There is also a method of joining an aluminum material and an iron material by spot welding instead of brazing. Furthermore, a laser roll method of dissimilar metals has also been proposed (Patent Document 3). In this method, after heating only the first metal plate by laser irradiation, the heated portion of the first metal plate is pressed against the second metal plate by a pressure roller, and both metal plates are subjected to plastic deformation. It is what is joined.

JP 7-148571 A JP 10-314933 A Japanese Patent No. 3535152 Journal of the Japan Welding Society Vol.22, No.2, p315-322 (2004) “Survey Research on Melting Process Aluminum / Steel Dissimilar Material Joining Techniques”, p. 75-93, 2002 Results Report (March 2003), Osaka University Institute of Joining Science, Dissimilar Materials Joining Study Group

  However, the conventional dissimilar material joining method has the following drawbacks. First, the dissimilar material joining method by brazing has a problem that the joining cost increases because it is necessary to insert a brazing material between the aluminum-based welded material and the iron-based welded material.

  Further, when this welding is performed by a conventional welding method, it is extremely difficult to stably weld so as to suppress generation of brittle intermetallic compounds, that is, not to melt the steel.

  Further, in the case of spot welding, since it is not line bonding but point bonding, liquid or gas passes through the portion between the bonding points, so that the materials to be bonded are hermetically or liquid-tightly sealed. I can't. In addition, spot welding has a limitation in joining work because joining work from one side is impossible and electrodes need to be arranged on both sides of the overlapping portion.

  Furthermore, in roll joining, it is necessary to press different materials with a roll, and there exists a difficulty that a large-scale apparatus is required.

  In addition, in DC pulsed MIG welding, since it is necessary to reduce the current, the arc becomes unstable, spatter is likely to occur, and a cleaning action for removing the oxide film cannot be expected. For this reason, in order to assist this, there is a difficulty that it is necessary to use a special or expensive flux cored wire for welding of aluminum.

  The present invention has been made in view of such problems, and can join an aluminum-based welded material and an iron-based welded material without using a brazing material, a flux, or the like, and is easy and low-cost. An object of the present invention is to provide a dissimilar material joining method capable of joining dissimilar materials together.

  The dissimilar material joining method according to the present invention is a dissimilar material joining method in which an aluminum-based welded material made of aluminum or an aluminum alloy and an iron-based welded material are arc-welded, and the iron-based welded material has zinc or zinc on the surface thereof. A material having a zinc-based coating layer made of an alloy is used, and the aluminum-based welded material and the iron-based welded material are arc-welded using aluminum or an aluminum alloy filler metal.

  Moreover, the said arc welding is MIG welding which applies an alternating current or an alternating current pulse current, and it can also comprise so that it may weld on the conditions which do not fuse the base material of an iron-type to-be-welded material.

  As the welding mode, for example, a lap fillet joint can be formed by arc-welding an overlapped portion in which the aluminum-based workpiece is overlapped above the iron-based workpiece.

  Alternatively, the end surface of the iron-based welded material is covered with the zinc-based coating layer in addition to the front and back surfaces, and the aluminum-based welded material and the iron-based welded material are butted against each other for arc welding. Alternatively, a lap fillet joint may be formed by arc welding of an overlapped portion in which the iron-based welded material is stacked above the aluminum-based welded material.

  According to the present invention, an aluminum-based welded material and an iron-based welded material can be joined without using brazing, flux, or the like, so that it is easy and low-cost, and does not use a large-scale apparatus. In addition, different materials can be joined together. And since this invention is not a point joining but a line joining, it can join dissimilar materials so that a junction part may become sealed.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a perspective view showing a dissimilar material joining method according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a joining portion. A steel plate 1 as an iron-based workpiece and an aluminum-based plate 2 as an aluminum-based (aluminum or aluminum alloy) workpiece are overlapped at the end, and the overlapped portion 3 is formed by MIG arc along the end. Weld.

  A surface of the steel plate 1 is covered with a zinc-based coating layer 4. This coating layer 4 can be formed by means such as hot dipping or thermal spraying. This coating may be a partial coating as long as it is applied to a place necessary for joining, and is essential at least on the surface to which the arc hits, and at the portion to which the arc hits, and also on the overlapping portion. It is desirable. This coating layer 4 is pure zinc or a zinc alloy containing, for example, Fe, Al, Ni or the like. As the steel plate 1, various steel materials such as mild steel, high-tensile steel, and stainless steel can be applied. Further, as the iron-based welded material, the shape is not limited to the plate material, and can be applied to a shape steel or the like.

  As the aluminum-based plate 2, pure aluminum and various aluminum alloys can be applied. In addition, the shape of the aluminum-based plate 2 is not limited to the case where the whole is a plate material, but may be a plate shape in the overlapping portion 3, and can be applied to various shapes and castings. it can.

  In this embodiment, the end portion of the aluminum-based plate 2 is overlapped on the end portion of the steel plate 1, and the overlap portion 3 is MIG (Metal Inert Gas) arc welded by the torch 5. In this case, the zinc-based coating layer 4 is formed on the front and back surfaces of the steel plate 1 as described above, but the zinc-based coating layer 4 is not formed on the end surfaces thereof. This is because the steel plate 1 is usually manufactured by, for example, forming a zinc-based coating layer on the surface of the steel plate by plating and then cutting a necessary portion by shearing or the like.

  In this MIG welding, an aluminum plate 2 and a steel plate 1 are welded using an alternating current or an alternating pulse current as a power source.

  Next, the operation of the dissimilar material joining method of this embodiment will be described. First, the aluminum-based plate 2 is disposed on the torch side, that is, above, and its end is overlapped on the end of the steel plate 1, and a lap fillet joint is formed on the overlap portion 3. Then, as shown in FIG. 2, an AC arc is generated between the welding wire fed from the torch 5 to the overlapped portion 3 and the material to be welded, and the arc is cleaned in a cycle in which the electrode wire serves as an anode. The oxide film is removed by the action, and the zinc-based coating layer and the end of the aluminum-based plate 2 are melted by the arc heat. Thus, since the zinc-based coating layer 4 covering the surface of the steel plate 1 is melted by the arc heat after the oxide film is removed by the cleaning action, the surface of the steel plate 1 is sufficiently wetted and spread. As a result, the molten metal formed by melting the end portion of the aluminum-based plate 2 and the molten metal of the aluminum filler material are well blended with the molten metal of the coating layer 4 spread on the surface of the steel plate 1. The base plate 2 and the steel plate 1 are joined well and in a wide area.

In this case, the molten metal formed by melting the end of the aluminum-based plate 2 and the molten metal of the aluminum filler metal are not directly mixed with the steel plate 1 as shown in FIG. For this reason, it is possible to prevent the formation of hard and brittle intermetallic compounds such as Fe ₂ Al ₅ and FeAl ₃ in this joint. If the steel side substrate starts to melt, an intermetallic compound with aluminum is easily generated and the joint strength is lowered. Therefore, the steel side substrate is not melted. There is a need. This is the reason why this AC MIG or AC pulse MIG welding method is actively utilized. In other words, even if the heat input from the primary side is the same as for DC type MIG welding, the base steel is reduced by suppressing the heat input to the base material and increasing the heat input to the electrode wire. While suppressing the penetration into the substrate and suppressing the formation of brittle intermetallic compounds of aluminum and iron, there is a feature that it is possible to secure a sufficient amount of deposited metal that leads to improved joint strength. In addition, if the so-called arc cleaning action in the cycle in which the electrode wire becomes the anode (the base material is the cathode), the zinc or zinc alloy coating layer covering the steel sheet is efficiently removed, In the subsequent melting process due to arc heat, the wettability is also greatly improved, and then the molten metal of the electrode wire dripping can be spread on the surface, so that the so-called leg length is increased and the joint strength is very advantageous. Become. In this way, only the metal coating layer 4 on the surface of the steel plate 1 can be effectively melted, and the steel plate 1 and the aluminum-based plate 2 can be joined. In order to prevent the above effect, that is, the amount of welding (throat thickness, leg length) and to suppress the penetration into the steel material, the polarity ratio (the cathode time ratio (EN ratio) of the electrode wire) is set to 5% to 80%. It is preferable. Furthermore, if pulse current is used, stable droplet transfer can be obtained even at lower current due to the effect of reducing the critical current, so welding can be performed with lower heat input, and penetration into the steel sheet can be further suppressed. At the same time, it is possible to use a large-diameter welding wire with stable feedability, which is more preferable.

  Next, another embodiment of the present invention will be described with reference to FIG. In the present embodiment, the end portion of the steel plate 1 is overlapped on the end portion of the aluminum-based plate 2, and the overlapped portion is arc-welded. In this case, the steel plate 1 is used in which the zinc-based coating layer 4 is also coated on the end surfaces in addition to the front and back surfaces. When the steel plate 1 is overlaid, the molten metal also contacts the end surface of the steel plate 1, but in this embodiment, the zinc-based coating layer 4 is also formed on the end surface of the steel plate 1, As in the case of FIG. 2, the molten metal does not directly contact the surface of the steel plate 1. For this reason, the production | generation of an intermetallic compound can be prevented and the junction part of favorable joint strength can be obtained similarly to the case of FIG.

  FIG. 4 is a view showing still another embodiment of the present invention. In the present embodiment, the steel plate 1 and the aluminum-based plate 2 are butt welded. Also in the present embodiment, since the steel plate 1 whose end face is coated with the zinc-based coating layer 4 is used, it is possible to prevent the formation of an intermetallic compound at the joint, and a joint with good joint strength can be obtained.

Examples of the present invention will be described below. In the test material constituting the lap fillet joint shown in FIG. 1, the aluminum-based plate 2 is a JISA5182P-O material, and the plate thickness is 1 mm. The steel plate 1 is an alloyed hot-dip galvanized steel plate (GA steel plate), a non-alloy hot-dip galvanized steel plate (GI steel plate), etc., and the plate thickness is 1 mm. The plating amount of the galvanized layer was 50 g / m ² on one side. However, in the examples, a coating layer formed by thermal spraying is also shown. Further, an example of a butt joint is also shown with a lapping margin of 0 mm. On the other hand, as a comparative example, a steel plate (plate thickness: 1 mm) not subjected to plating was used. A part of the steel plate 1 was placed on the aluminum plate 2 as shown in FIG.

  As shown in FIG. 1, both ends of the aluminum plate 2 and the steel plate 1 were overlapped, and MIG welding was performed from the aluminum plate 2 side under the condition of a current value of 50A. However, some are TIG welding.

The lap fillet joint thus arc welded was processed into a JIS Z2201 No. 5 test piece and then subjected to a tensile test. The tensile strength at break and the break position are shown in Table 1 below. However, in Table 1, the GA steel plate is an alloyed hot-dip galvanized steel plate, which is plated with 50 g / m ² of Zn on one side. The Gl steel plate is a hot dip galvanized steel plate (non-alloy) and is plated with 50 g / m ² of Zn on one side. The Zn-55% Al-plated steel sheet is a hot-dip galvanized-55% aluminized steel sheet and is plated with 100 g / m ² of Zn on both sides. The Zn-5% Al-plated steel sheet is a hot-dip zinc-5% aluminum alloy-plated steel sheet, plated with 50 g / m ² of Zn on one side. The Zn-Ni plated steel sheet is an electrogalvanized steel sheet, plated with 40 g / m ² of Zn on one side.

  As shown in Table 1, in the case of the example of the present invention, there was no penetration into the steel part, and there was no lack of surplus, and good joint strength was obtained. On the other hand, in Comparative Example 1 using a bare steel plate having no zinc coating layer, penetration on the steel side was observed and bonding could not be performed. In addition, as shown in Comparative Examples 3 and 4, even when the lapping cost is short, the heat capacity is reduced, and as a result, heat is accumulated and the steel side substrate melts, so that it cannot be joined or the joint strength is low. Met.

  In Comparative Examples 6, 7, 8, and 9 in which the steel is arranged on the upper side and the end surface is not coated with zinc, the arc directly hits the steel, and the steel easily melts and cannot be joined. In Examples 8 and 9 in which the steel side end was also coated, the steel side substrate was not melted, and high joint strength was obtained.

  In Example 10, since the current type is a normal alternating current and a thick wire having a wire diameter of 1.2 mm is used, compared to Example 1 using an alternating pulse current, the result of frequent spattering is sufficient for practical use. The joint strength was slightly inferior. In Comparative Example 10, since the current format was DC, the steel side substrate melted, and the joint strength was low. In Comparative Example 11, since TIG welding was performed under a slow speed condition, the steel side substrate began to melt, and the joint strength was low.

  In Examples 7 and 15, which are butt joints and the end surface on the steel side was coated with zinc, the steel material was not melted and high joint strength was obtained. In Comparative Example 5 without the coating, the steel side substrate was Melting was observed, bead cracking was observed, and bonding was not possible.

It is a perspective view which shows the different material joining method which concerns on embodiment of this invention. It is sectional drawing of the junction part similarly. It is sectional drawing which shows the dissimilar material joining method which concerns on other embodiment of this invention. It is sectional drawing which shows the dissimilar material joining method which concerns on further another embodiment of this invention. It is sectional drawing which shows the dissimilar material joining method which concerns on further another embodiment of this invention.

Explanation of symbols

1: Steel plate (iron-based welded material)
2: Aluminum-based plate (aluminum-based welded material)
3: Overlapping part 4: Zinc-based coating layer 5: Torch

Claims (7)

In the dissimilar material joining method of arc welding an aluminum-based welded material made of aluminum or an aluminum alloy and an iron-based welded material, the iron-based welded material has a zinc-based coating layer made of zinc or a zinc alloy on the surface thereof. What is claimed is: 1. A dissimilar material joining method comprising: arc welding an aluminum welded material and an iron welded material using an aluminum or aluminum alloy filler metal. 2. The dissimilar material joining method according to claim 1, wherein the arc welding is performed under a condition in which a base of the iron-based workpiece is not melted. The said arc welding is MIG welding which applies an alternating current or an alternating current pulse current, and welds on the conditions which do not fuse the base material of an iron-type to-be-welded material, The dissimilar material joining method of Claim 1 characterized by the above-mentioned. 4. The lap fillet joint is formed by arc-welding an overlapped portion in which the aluminum-based welded material is overlapped above the iron-based welded material. 5. Dissimilar material joining method. In addition to the front and back surfaces of the iron-based welded material, the end surface is also coated with the zinc-based coating layer, and the aluminum-based welded material and the iron-based welded material are butted together by arc welding. 5. The dissimilar material joining method according to claim 1, wherein a joint is formed. In addition to the front and back surfaces of the iron-based welded material, the end surface is also coated with the zinc-based coating layer, and the overlapped portion in which the iron-based welded material is stacked above the aluminum-based welded material is arc-welded. 4. The dissimilar material joining method according to claim 1, wherein a lap fillet joint is formed. The dissimilar material joining method according to any one of claims 1 to 6, wherein the iron-based workpiece is partially coated with zinc or a zinc alloy at portions necessary for welding of the front surface, back surface, and end surface.

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