| 摘要 |
PURPOSE:To produce a high toughness high tensile steel plate with excellent weldability and less separation by rolling a steel ingot. contg. limited compsn. of C, Si, Mn, Nb, B, N, Ti, Al, S, etc. thoroughly at high and middle temps. after heat treatments. CONSTITUTION:The steel slab contg. 0.04-0.12wt% C, 0.05-0.3% Si, 1.2-2.5% Mn, 0.03-0.10% Nb, 0.0005-0.003% B, <=0.008% N, 0.005-0.04% Ti, 0.005- 0.08% Al, <=0.008% S, if necessary, added with >=1 kind among <=1.0% Ni, <=0.5% Mo, <=0.5% Cu, <=0.5% Cr, <=0.1% V, 0.002-0.01% Ca, 0.002-0.01% rare earth elements, and consisting of the balance Fe and unavoidable impurities is heated to the temp. at which at least 0.03% Nb solutionizes, and the slab is subjected to high temp. rolling to >=50% cumulative draft at temp. higher than (Ar3 transformation point +150 deg.C), and further the same is subjected to finish rolling to >=60% comulative draft at temp. lower than said temp. and higher than the Ar3 transformation point; thereafter the rolled steel plate is air cooled. |
