Effect of Welding Method on the Hardness of Joint of 600MPa Grade New Generation Steel

Laser-MAG hybrid, GMAW and SAW welding experiment were carried out for the new low CE 600MPa grade steel, and hardness survey on the welded joints was performed. Laser-MAG hybrid welding has the highest speed with the least filling weld metal, and its joint exhibits almost no softening with higher harness in weld than base metal. SAW welding has high efficiency but most significant softening effect on the HAZ. For SAW, on the HAZ 4 ~ 5 mm apart from the fusion line peak hardness exists. For GMAW, on the HAZ about 2mm away from the fusion line a softened zone appears, but the softening degree is lower than for SAW. The results showed that the hardness of the welded joint of this type of steel seems much subjected to the welding heat input.