Effects of Tempering on the Strengthening and Toughening of Hybrid Laser-Arc Welded Joints
F-D. Liu, L-F He, S-F. Du, M-Y. Chen, B. Yao, H. Zhang and S-Y. Liu
Hybrid laser-arc welding of a high strength steel has been conducted. These welds were then subjected to tempering across a range of temperatures. Joints obtained at a low tempering temperature have a higher hardness but a lower toughness. The hardness of the joints after tempering at a medium temperature is lower than without any heat treatment, but the hardness distribution is uniform. When the tempering temperature increases to 450oC, the hardness of the joints and the toughness of the heat affected zone (HAZ) increase. After tempering at a high temperature, the hardness does not significantly change and is uniformly distributed. The hardness of the base metal (BM) decreases drastically when the temperature is higher than 600oC. When the tempering temperature is 550oC, the strength and the toughness of the joint are optimal.
Keywords: Nd:YAG laser, arc welder, high strength steel, hybrid laser-arc welding, tempering, microstructure, heat affected zone (HAZ), strengthening, toughening