| 摘要 |
PURPOSE:To obtain high tensile steel having high strength and weldability by melting specific low alloy steel consisting basically of C, Si, Mn, solAl to ingot, and hot rolling and acceleratively cooling the same under specific conditions. CONSTITUTION:The steel consisting 0.03-0.18% C, <=0.6% Si, 0.5-2.0% Mn, 0.01-0.08% solAl, and if necessary, 0.01-0.1% Nb, 0.01-0.15% V, 0.01-0.15% Ti, <=1.0% Cu, <=1.0% Mo, <=1.0% Ni (except copresence of Cu, Cr and copresence of Ni, Mo, Nb, V, Ti) and the balance iron and satisfying <=0.20% low- temp. cracking sensitive compsn. and >=(25.8-0.18Vc)/78 carbon equiv. of accelerative cooling material is melted to ingot. The molten metal is hot rolled at >=20% cumulative draft below the Ar3 point and 650-(Ar3-30) deg.C finishing temp. and is cooled acceleratively at 4-25 deg.C/sec for at least 80 deg.C temp. width down to >=500 deg.C; thereafter the steel is allowed to cool. Thus the high tensile steel having excellent weldability and >=50kg/mm.<2> strength is obtained. |
