| 摘要 |
A process for producing a high toughness, high strength steel having excellent resistance to stress corrosion cracking including the steps of: preparing a steel slab including 0.02 to 0.10 wt % of C, 0.50 wt % or less Si, 0.4 to 1.5 wt % Mn, 1.0 to 7.5 wt % Ni, more than 1.0 wt % up to 1.5 wt % Mo, 0.80 wt % or less Cr, 0.01 to 0.08 wt % sol. Al, and the balance of Fe and unavoidable impurities; heating the steel slab to a temperature of from 1000 DEG C. to 1250 DEG C.; hot rolling the heated steel slab at a finishing nip temperature of from 700 DEG C. to 880 DEG C., at a total reduction rate of 40% or more effected at the finishing nip temperature or lower, and at a finishing temperature of 650 DEG C. or higher, to provide a steel plate; then quenching the steel plate by initiating water cooling at a temperature of the Ar3 point thereof or higher and by terminating the water cooling at a temperature of 150 DEG C. or lower; and tempering the quenched steel plate at a temperature of the Ac1 point thereof or lower.
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