The Procedure For CMT Method MIG Brazing Of Aluminium And Galvanized Steel

Aim to application of aluminium alloy and galvanized steel for automobile industry, the dissimilar joint between aluminium alloy and galvanized steel sheet during cold metal transfer brazing was analyzed. The features of the dissimilar joint and the effect of the weld parameters on mechanical properties were discussed.The results of dissimilar joints welding between 1mm thick aluminium alloy 6061 and galvanized steel show that a good lap joint was formed, which was divided into welded metal, middle interface, transitional interface and zinc-rich zone. Welded metal is composed ofα-Al and Al-Si eutectic; The thickness of middle interface is 7 to 8μm, composed of FeAl₃ intermetallics; The thickness of transitional interface is 4 to 5μm, composed ofαsolid solution and FeAl₃ intermetallics; Zinc-rich zone is composed of Al-Znαsolid solution, Al-Zn eutectoid and Al-Zn eutectic.By means of microstructure and mechanical properties analysis of the joints between 1mm thick aluminium 1060 and galvanized steel, the parameters of CMT brazing process were optimized. When heat input is increased, the thickness of interface layer increases, the composition of the middle interface also changes from Fe2Al5 to FeAl2 and FeAl3 intermetallics. When the torch in middle, wire feed rate 3.9 m/min, welding speed 13.9 mm/s, welding current 66 A , welding voltage 11.8 V, continuous, uniform and best shape joint was formed, the shearing strength was up to 82.6 MPa.By the analysis of the effect of different zinc layer thickness on the joint, zinc element effectively promotes molten aluminium wetting the steel sheet, it is good to dissimilar joints between aluminium alloy and galvanized steel when the zinc layer is enough thick. More heat input is needed to promotes molten aluminium wetting the steel sheet when the zinc layer is thin.