| 摘要 |
<p>A process for producing a thick high-strength steel plate which comprises cooling a continuous-casting slab containing, in terms of mass%, 0.05-0.12% carbon, up to 0.3% silicon, 1-2% manganese, up to 0.015% phosphorus, up to 0.005% sulfur, 0.0003-0.003% boron, 0.01-0.15% vanadium, 0.001-0.1% aluminum, 0.005-0.02% titanium, 0.002-0.01% nitrogen, and up to 0.004% oxygen, with the remainder being iron and incidental impurities, to a temperature lower than Ar3 by at least 200°C, subsequently heating the slab again to 950-1,100°C, then roughly rolling the continuous-casting slab at 900°C or higher so as to result in a cumulative draft of 30% or more, subsequently conducting finish rolling at 700°C or higher to a cumulative draft of 50% or more under such conditions that the temperature at which the finish rolling is initiated and the temperature at which the finish rolling is terminated each is not higher than the temperature represented by the expression {-0.5x(slab heating temperature (°C)) + 1,325} (°C) to thereby form a rolled plate, and then rapidly cooling the rolled plate to 500°C or lower to obtain a steel plate. The continuous-casting slab has an amount of boron present in the form of solution in the austenitic raw material before transformation {effective boron amount: Bef (%)} of 0% or smaller in terms of calculated value and has a carbon equivalent (Ceq) in the range of 0.32-0.42%.</p> |
