STEEL MATERIAL FOR HIGH-HEAT-INPUT WELDING

摘要

Provided is a steel material appropriate for high-heat-input welding with a welding heat input of over 300kJ/cm, and suitable for shipbuilding, building construction, public works and a variety of other structures. Specifically, the steel material has a chemical composition containing, in mass percentages, C: 0.03-0.08%, Si: 0.01-0.15%, Mn: 1.8-2.6%, P: 0.008% or less, S: 0.0005-0.0040%, Al: 0.005% or less, Nb: 0.003-0.03%, Ti: 0.005-0.030%, N: 0.0050-0.0080%, B: 0.0003-0.0025%, and, as necessary, 0.33-0.45 of V, Cu, Ni, Cr, Mo, Ca, Mg, Zr, one or more types of REM, and Ceq (IIW), with the remainder being Fe and inevitable impurities. Furthermore, the structure in the heat-affected section near the bond when performing high-heat-input welding with a welding heat input of over 300kJ/cm has a prior austenite grain size of 200mum or less, and an area ratio of island martensite of 1.0% or less.