Application of laser welding technology in dissimilar metal welding

Many industries require joining disparate metallic materials for structural, application or economic reasons. Combining different metals can better exploit the best properties of each metal. Therefore, before starting any welding operation, the welder must determine the properties of each material, including the melting point of the metal, thermal expansion, etc., and then choose a welding process that suits him based on the characteristics of the material.

Dissimilar metal welding refers to the process of welding two or more different materials (with different chemical compositions, metallographic structures or properties) under certain process conditions. Among the welding of dissimilar metals, the most common one is the welding of dissimilar steel, followed by the welding of dissimilar non-ferrous metals. When dissimilar metals are welded, a transition layer with different properties from the base metal will be produced. Since dissimilar metals have significant differences in elemental properties, physical properties, chemical properties, etc., the welding operation technology of dissimilar materials is much more complicated than the welding of the same material.

Laser welding machines can overcome these obstacles and truly achieve perfect welding of dissimilar metals.

1. Laser welding of copper and steel

Copper-steel welding is a typical welding of dissimilar materials. There are great differences in the melting points, thermal conductivity coefficients, linear expansion coefficients, and mechanical properties of copper and steel, which are not conducive to direct welding of copper and steel. Based on the advantages of laser welding such as high thermal energy density, less molten metal, narrow heat-affected zone, high joint quality, and high production efficiency, laser welding of copper and steel has become the current development trend. However, in most industrial applications, copper's laser absorption rate is relatively low, and copper is prone to defects such as oxidation, pores, and cracks during the welding process. The laser welding process of copper and steel dissimilar metals based on multi-mode lasers needs further development.

2. Laser welding of aluminum and steel

The melting points of aluminum and steel are very different, and it is easy to form metallic compounds of dissimilar materials. In addition, aluminum and steel alloys have the characteristics of high reflectivity and high thermal conductivity, so it is difficult to form keyholes during welding, and high energy density is required during welding. Experiments have found that by controlling the laser energy and the action time of the material, the thickness of the interface reaction layer can be reduced and the formation of the intermediate phase can be effectively controlled.

3. Laser welding of magnesium aluminum and magnesium aluminum alloys

Aluminum and its alloys have the advantages of good corrosion resistance, high specific strength, and good electrical and thermal conductivity. Magnesium is a non-ferrous metal that is lighter than aluminum, has higher specific strength and specific stiffness, and has good impact resistance. The main problem of magnesium-aluminum welding is that the base metal itself is easily oxidized, has a large thermal conductivity, and easily produces welding defects such as cracks and pores. It also easily produces intermetallic compounds, which significantly reduces the mechanical properties of the solder joints.

The above is the welding application of laser welding machine in dissimilar metal materials. Laser welding of dissimilar metal materials has expanded from dissimilar steel to non-ferrous metals and their alloys, especially magnesium-aluminum alloys and titanium-aluminum alloys. Laser welding has made progress, and welded joints with certain penetration depth and strength have been obtained.