EXPERIMENTAL-STUDY OF DUAL-BEAM LASER-WELDING OF AISI-4140 STEEL

Experiments were conducted to assess the impact of dual-beam laser wel ding on the cooling rates, and thus microstructure and hardness, of we ldments. Temperature measurements were continuously recorded using K-t ype thermocouples. The results indicate that dual-beam laser welding r educes the hardness of a weldment when compared to the case of single- beam laser welding. For example, the hardness of the hot-rolled AISI 4 140 steel used was about 283 HB before laser welding. After laser weld ing with a power of 800 W and a welding speed of 10 mm/s, the hardness became 552 HB; bur with a preheating power of 800 W and an interbeam spacing of 10 mm, the hardness reduced to 477 HB for the same welding speed. The impacts of minor heat source power, welding speed and inter beam spacing on weldment hardness and weld shape for both preheating a nd postheating cases are discussed.