Thermal simulation of a net-like microstructure in weld joint of high-strength steel thick plate by Double-Sided Arc Welding

摘要

In Double-Sided Arc Welding (DSAW) of high-strengthsteel thick plate, a net-like microstructure is observed along the grain boundaries of heat affected zone. In this paper, the effects of the net-like microstructure on the mechanical properties of the weld joint were studied through thermal simulation. The results indicated that there were two necessities for the net-like microstructure's coming into being and the microstructure was predominately consisted of blocky martensite-austenite constituents with high carbon and alloy elements content. A great amount of low carbon lath martensite and a few ferrites were reserved from the initial Coarse Grained Heat Affected Zone (CGHAZ). Meanwhile, Intercritically Reheated Coarse Grained Heat Affected Zone (ICCGHAZ) contained more and larger net-like microstructure, when compared with the CGHAZ and the base metal, resulting a higher tensile strength but 19.9% and 11.6% toughness loss respectively. The impact toughness of ICCGHAZ can be increased by 10.26% through high-temperature additional tempering.