Thermal processes, microstructure, and mechanical properties near weld toe in double-sided double gas tungsten arc backing welding joint of 10CrNi3MoV steel

This study focused on heat-affected zone thermal processes, microstructural evolution, and impact toughness near weld toe of backing passes in double-sided double arc welding where there is stress concentration. The results show that as the arc distance increases, the second peak temperature near weld toe will accordingly decrease and the intercritically reheated coarse-grained heat-affected zone will appear. The formation of martensite-austenite constituents distributed both along the prior austenite grain boundaries and inside prior austenite grains leads to the poor toughness of intercritically reheated heat-affected zone. When short arc distance is adopted, supercritically reheated coarse-grained heat-affected zone will appear near weld toe which possesses high toughness due to the good toughness of lath bainite and the fine bainite/martensite packets. During double-sided double arc backing welding, short arc distance should be used to obtain excellent impact toughness.