PRODUCTION OF FIRE RESISTANT STEEL FOR STRUCTURAL USE EXCELLENT IN HIGH TEMPERATURE STRENGTH PROPERTY AFTER REHEATING AND HAVING =600KG STRENGTH

摘要

PURPOSE:To obtain a steel for structural use excellent in strength, weldability and ductility and toughness by subjecting a steel in which C, Si, Mn, P, S, Mo, Ti, V, Al and N are specified to hot rolling under prescribed conditions and thereafter executing heat treatment such as hardening. CONSTITUTION:A steel having a compsn. constituted of, by weight, 0.05 to 0.2% C, 0.1 to 2% Si, 0.3 to 2% Mn, %h0.03% P, =0.03% S, 0.1 to 0.4% Mo, 0.003 to 0.1% Ti, 0.01 to 0.1% V, 0.002 to 0.2% SolAl, 0.001 to 0.02% N and the balance Fe is melted. This steel is heated to 1000 to 1350 deg.C and is subjected to hot rolling at =900 deg.C at =30% draft. Next, its finishing temp. is regulated to the Ar3 to the Ar3+150 deg.C, and the steel is thereafter immediately hardened. Or, the steel is air-cooled, is reheated to =880 deg.C, is thereafter hardened, is subsequently reheated to =700 deg.C and is air-cooled.