FIRE-RESISTANT HIGH-STRENGTH ROLLED STEEL MATERIAL AND METHOD FOR PRODUCTION THEREOF

摘要

Disclosed is a fire-resistant high-strength rolled steel material which has excellent fire resistance and toughness and can be used as a structural member for a building structure. The material comprises the following components (by mass): C: not less than 0.005% and less than 0.04%; Mn: 0.8-1.7%; Si: not less than 0.05% and less than 0.4%; Nb: 0.02-1%; Ti: 0.005-0.02%; N: not less than 0.005%; B: 0.0003-0.003%; and Al: 0.005-0.03%, and has the Ti/N ratio of 2 to 8 (mass%) and the C-Nb/7.74 value of 0.02% or less, wherein the remainder is Fe and unavoidable impurities. The material has the ratio of the 0.2% proof stress at 600°C to the yield strength at room temperature of 0.50 or greater.