STEEL FOR WELDED-STRUCTURE AND MANUFACTURING METHOD THEREOF, POST WELD HEAT TREATED WELDED-STRUCTURE AND MANUFACTURING METHOD THEREOF

摘要

The present invention provides a post weld heat treated structure and a manufacturing method thereof. The post weld heat treated structure includes 0.03-0.07 wt% of C, 0.1-0.5 wt% of Si, 0.5-1.8 wt% of Mn, 0.01-0.06 wt% of Al, 0.02~0.10 wt% of Nb, 0.005-0.05 wt% of Ti, 0.05 wt% or less of V, 0.001-0.007 wt% or less of N, 0.020 wt% or less of P, 0.003 wt% or less of S, the remainder being Fe and other inevitable impurities. A microstructure of the post weld heat treated structure comprises: ferrite having the average area percentage of carbide of 0.50m or less; and cementite as a remainder. According to the present invention, the present invention can provide steel for a welded structure, the welded structure and the manufacturing method thereof whereby strength is increased rather than decreased even after PWHT.