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　　The welding of heterogeneous metals refers to the operation of welding two or more different kinds of metals. Due to the progressiveness of laser welding technology, laser welding of heterogeneous metals has become more common in production and life.

　　Heterogeneous metal laser welding requires welding two completely different metal materials together, and a transition layer with different properties, structures, and base materials will occur in between. Due to the differences in elemental characteristics, physical and chemical properties of heterogeneous metals, compared with similar metal welding, the process is very complex in both welding principles and operation techniques.

　　Heterogeneous metal laser welding, the technical secrets are here

　　The main problems in heterogeneous metal laser welding are:

　　1. The greater the difference in the coefficient of linear expansion of heterogeneous metal materials, the greater the difficulty of welding

　　When laser welding heterogeneous metals, the larger the coefficient of linear expansion of the material, the higher the thermal expansion rate, and the greater the shrinkage that occurs during cooling. This will result in significant welding stress during the crystallization of the molten pool. And this kind of stress is not easy to eliminate, which will cause welding deformation hazards.

　　2. The inherent melting point of heterogeneous metal materials is positively correlated with welding difficulty

　　In the process of heterogeneous metal laser welding, when a metal material with a low melting point reaches its melting point and enters a molten state, another material with a high melting point still remains in a solid state. In this case, the melted material liquid can easily penetrate the grain boundaries of the overheating zone, causing the loss of the low melting point material, burning or gasification of alloy elements, and making it difficult to complete the welding. The welding of iron and lead materials is very difficult, as these two materials not only cannot dissolve in each other in the solid state, but also cannot dissolve in each other even in the liquid state.

　　Heterogeneous metal laser welding, the technical secrets are here

　　3. The greater the difference in thermal conductivity and specific heat capacity between heterogeneous metals, the more difficult it is to weld

　　The crystallization of metals is influenced by the thermal conductivity and specific heat capacity of the metal material, as well as the wetting properties of refractory metals, which in turn affects the quality of the weld seam. Therefore, when laser welding heterogeneous metals, a strong heat source should be selected for welding, and the position of the heat source during welding should be biased towards materials with good thermal conductivity.

　　4. When welding heterogeneous metals, it is difficult to achieve equal strength between the weld seam and the two base metals

　　During laser welding of heterogeneous metals, metal elements with low melting points are more prone to high temperatures and evaporation, resulting in changes in the chemical composition of the weld and a decrease in mechanical properties, especially when welding different non-ferrous metals.

　　5. Heterogeneous metals with greater electromagnetic differences are more difficult to weld

　　The greater the difference in electromagnetic properties of heterogeneous metal laser welding materials, the more unstable the welding is, which affects the quality of the weld seam.