Study on processing parameters' influence to the quality and microstructure of spot-welded joint for the Al-Zn alloy coated steel

By the spot welding experiments of Al-Zn alloy coated steel,the metallographic analysis and the shear experiment have been carried out to the spot welding joints achieved by twelve group processing parameters.The result indicates that the joint is lack of fusion in lower welding current or shorter welding time;and too higher current can cause more splashing in welding,the overproof depth of indentation on spot weld,and the stronger directional rough columnar crystals;and enhancing welding force properly can make the columnar crystals leaning or directional weakly.It is defined that the more appropriate processing parameters for 0.8 mm Al-Zn alloy coated steel spot welding is I=8.5～9.0 kA,T=14 cyc,FW=2 400 N,by the group processing parameter in welding,both the spot-welded joint's resisting shear and the nugget size are above A-level requirement in the standard of ″Method of Inspection for Spot Weld″,and the penetration rate and the depth of indentation on spot weld meet the quality requirements.