Dissimilar metals joints of the galvanized steel (GI steel) and the pure aluminum (A1050) were produced using the laser pressure welding method. In this method, dissimilar metals sheets were set between the twin rolls. These sheets were opened to make up the wedge-shaped-gap. A 2 kW YAG laser beam was irradiated into a wedge-shaped-gap by a f:θ lens and scanned at various frequencies and patterns using two dimensional scanning mirrors. Then the sheets were pressed by the pressure rolls to be joined.
The welding of the GI steel and A1050 were carried out. In order to investigate the effect of a zinc plated layer thickness on the weldability, the GI steel of plated layer thickness of two types were used, and plated layer thickness were about 1.7 µm and 2.6 µm.
The laser pressure welding experiments conducted by changing the laser power and the roller pressure indicated that welding is possible under except some conditions. The intermetallic compounds were observed by optical microscope, and the layer thicknesses were measured. The intermetallic compound layer thicknesses increased according to the increase in the laser power and the roller pressure, and the thicknesses of the compound layers were about 3 µm to 18 µm. The tensile shear strength and the peel strength of the welded joints were evaluated. In the tensile test, the strengths of the joints yielded in most welded conditions were so high that the fracture occurred in the aluminum base metal. In the peel test, the roller pressure of more than 1.96 kN, the specimen fracture occurred in the aluminum base metal. In order to investigate the joining mechanism of the welded joints of GI steel and A1050, the TEM observation of the compound layer was carried out to examine the reason why the high joint strength was obtained even if the compound layer was thick. From TEM observed results, the joints consisted of the intermetallic compounds mainly, and the Zn phases were formed between the intermetallic compounds. In this research, even if the mainly constitution phases were the intermetallic compounds, the high joint strengths were obtained because the Zn phases formed in the grain boundary of intermetallic compounds.