HIGH TENSILE STRENGTH, REFRACTORY STEEL HAVING EXCELLENT WELDABILITY AND GAS CUTTABILITY AND METHOD FOR PRODUCING SAME

摘要

Accordingly to an exemplary embodiment of the present invention, a high tensile strength, refractory steel can be provided which comprises, in mass %, approximately C: 0.04 to 0.14%, Si: 0.50% or less, Mn: 0.50 to 2.00%, P: 0.020% or less, S: 0.010% or less, Nb: 0.01 to 0.05%, Mo: 0.30% or more and less than 0.70%, Al: 0.060% or less, N: 0.0010 to 0.0060%, and the balance consisting of iron and unavoidable impurities. For example, a weld crack sensitive composition P_CM can be defined by the following equation may be about 0.25% or less:; P_CM=C+Si/30+Mn/20+Cu/20+Ni/60+Cr/20+Mo/15+V/10+5B.;An area fraction of polygonal ferrite or pseudo polygonal ferrite in a ¼ thick position in the plate thickness direction of the steel plate of the final rolling product is about 10% or less.