| 摘要 |
PURPOSE:To obtain a high tension steel plate having high strength and excellent toughness in component-series, which is basically not necessary to add Cr, Mo, etc., by executing the prescribed quenching and tempering after finishing hot- rolling of the steel having the specific composition of rather high C content and adding Ti, etc. CONSTITUTION:The steel consisting of 0.12-0.18wt.% C, 0.05-0.80% Si, 1.20-1.60% Mn, 0.01-0.08% Al, 0.01-0.05% Nb, 0.005-0.025% Ti, 0.0005-0.0025% B and the balance of iron with inevitable impurities, is used. This steel slab is heated at >=1,000 deg.C and after the hot-rolling is finished at >=800 deg.C, immediately cooled rapidly to <=150 deg.C and next, is tempered in the temp. range of >=550 deg.C-<=Ac1 point. In case necessary, one kind or more among 0.10-0.30% Cu, 0.05-0.20% Cr, 0.03-0.10% Mo and 0.02-0.10% V is added to the above steel components.
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