Narrow Overlap Welding of 780DP Steel and DC04 Plain Carbon Steel

780DP steel and DC04 plain carbon steel were joined by narrow overlap welding with different welding parameters.The effects of welding parameters on welding quality of 780DP steel and DC04 plain carbon steel were studied.The results show that excessive and insufficient heat inputs may result in welding beading and lack of penetration,respectively,which are two typical welding defects.Furthermore,cracks of cupping test were both parallel to the welding seam.The welding quality was the most sensitive to the change of pressure of electrode wheel and weakened sensitive to the welding current and the welding rate in turn.Due to the function of the welding thermal cycle,the microstructure of heat affected zone and weld seam zone had large changes.The hardness of weld seam zone and heat affected zone increased relative to the base metal.When the amount of overlap was 1.7 mm,the welding compensation on the transmission side was 0.4 mm and the rolling force was 40 kN,the optimal welding parameters were as follows: welding current of 18 kA,welding speed of 7 m·min-1and electrode pressure of 15 kN.