FIRE-RESISTANT STEEL MATERIAL EXCELLENT IN HIGH-TEMPERATURE STRENGTH AND IN LOW-TEMPERATURE TOUGHNESS AND REHEAT EMBRITTLEMENT RESISTANCE IN WELD HEAT-AFFECTED ZONE, AND METHOD FOR MANUFACTURING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a fire-resistant steel material which has a high yield strength at 600°C, at the same time, suppresses reheat embrittlement in a weld heat-affected zone at the time of fire, and further is excellent in the toughness of a base metal and a weld joint.;SOLUTION: The fire-resistant steel material excellent in high-temperature strength and in low-temperature toughness and reheat embrittlement resistance in the weld heat-affected zone includes 0.005-0.050% C, 0.01-0.50% Si, 0.50-2.00% Mn, 0.50-2.00% Cr, 0.001-0.006% N, 0.001-0.030% Ti and 0.005-0.10% Al, and less than 0.01% Mo, less than 0.0003% B, less than 0.02% P, less than 0.01% S and less than 0.01% O which are limited, and the balance Fe with unavoidable impurities; has a tensile strength of 400-610 MPa at room temperature; has a yield stress of 157 MPa or more at 600°C when a tensile strength at room temperature is 400-489 MPa and has a yield stress of 217 MPa or more at 600°C when a tensile strength at room temperature is 490-610 MPa; and has a fracture reduction value of 20% or more at 600°C in the weld heat-affected zone.;COPYRIGHT: (C)2011,JPO&INPIT