Weld microstructure characteristics of dual laser beam multi-layer welded high strength steel with filler wire

In present work, the 16 mm thick 11CrNi3MnMoV low alloy high strength steel plates are well joined by dual laser beams welding with hot filler wire, and the strength of joint is higher than parent metal. The microstructure characteristics of primary laser weld, the secondary remelting weld, heat treatment weld, and the effect of microstructure transformation on performances of weld are investigated. The results indicate that, in dual laser beams welding with filler wire, the microstructure of weld is mainly bainite and acicular ferrite, which should be refined by remelting and heat treatment. It's distinct that the microstructure in reheated zone is similar to that of heat affected zone, and consists of normalized and tempered bainite. Moreover, the acicular ferrite in inner layer weld is much more than that in last layer weld. Meanwhile, a large number of parallel and compact ferrite exist in weld, which improve the tough of weld joint.