Hardness prediction based on microstructure evolution and residual stress evaluation during high tensile thick plate butt welding

Two High Tensile Strength Steel (EH47) plates with thickness of 70 mm were butt-welded together by multi-pass Submerged Arc Welding (SAW), also the hardness and welding residual stress were investigated experimentally. Based on Thermal-Elastic-Plastic Finite Element (TEP FE) computation, the thermal cycles during entire welding process were obtained, and the HAZ hardness of multi-pass butt welded joint was computed by the hardenability algorithm with considering microstructure evolution. Good agreement of HAZ hardness between the measurement and computational result is observed. The evolution of each phase was drawn to clarify the influence mechanism of thermal cycle on HAZ hardness. Welding residual stress was predicted with considering mechanical response, which was dominantly determined by last cap welds through analyzing its formation process. •Welding procedure and technique for thick plates of EH47 by means of multi-pass submerged arc welding were carried out.•Welding residual stress and microhardness were experimentally measured for welding quality inspection.•Robust TEP FE computation to examine thermal and mechanical responses during entire welding process was achieved.•Microstructure evolution during heating and cooling was demonstrated, predicted HAZ hardness agrees well with measurement.•Residual stress evolution was investigated and its magnitude and distribution after eventual cooling down were discussed.