| 摘要 |
<p>PURPOSE: Fire-resistant steel for construction having a low yield ratio and a method of manufacturing the same are provided to ensure cost effectiveness since steel is obtained, whose yield strength at 600°C is over 70% at room temperature. CONSTITUTION: A method of manufacturing fire-resistant steel for construction having a low yield ratio comprises the following steps. Steel is prepared, which consists of C of 0.05-0.15%, Si of 0.6% or less, Mn of 0.8-1.8%, P of 0.03% or less, S of 0.005% or less, Mo of 0.35-0.8%, Ti of 0.005-0.025%, Al of 0.06% or less, and N of 0.006% or less, in mass%. The steel is first quenched to form a micro austenite structure. The first quenched steel is second quenched to form a final structure. The final structure of the fire-resistant steel is a complex structure which comprises ferrite, martensite, and bainite.</p> |
