High-strength steel material excellent in brittle crack propagation resistance and brittle crack initiation resistance of welds and method for producing the same

摘要

A high-strength steel material excellent in brittle crack propagation resistance and brittle crack initiation resistance of a welded portion and a method for producing the same are provided. According to one aspect of the present invention, by weight, C: 0.05 to 0.09%, Mn: 1.5 to 2.2%, Ni: 0.3 to 1.2%, Nb: 0.005 -0.04%, Ti: 0.005-0.04%, Cu: 0.1-0.8%, Si: 0.05-0.3%, Al: 0.005-0.05%, P: 100 ppm or less, S: 40 ppm or less, remaining Fe and other inevitable impurities, the microstructure of the central part is a mixed phase of acicular ferrite and granular bainite, upper bainite, and the remaining ferrite, pearlite, island martens It consists of one or more selected from the group consisting of sites (MA), and the microstructure of the surface portion in the region of 2 mm or less immediately below the surface consists of one or more of ferrite, the remaining bainite, martensite, and Shape when welding Provided is a high-strength steel material excellent in brittle crack propagation resistance including 5% or less of island-shaped martensite and weld brittle crack initiation resistance, and a method for producing the same. . According to the present invention, it is possible to obtain a high-strength steel material having high yield strength and excellent in brittle crack propagation resistance and brittle crack initiation resistance in welds.