Abstract: 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.degree. C. to 1250.degree. C.; hot rolling the heated steel slab at a finishing nip temperature of from 700.degree. C. to 880.degree. 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.degree. C. or higher, to provide a steel plate; then quenching the steel plate by initiating water cooling at a temperature of the A.sub.r3 point thereof or higher and by terminating the water cooling at a temperature of 150.degree. C.

Abstract: A low temperature high strength tough steel is provided by effecting a series of heat treatments at predetermined temperatures.The steel comprises C, Si, Mn, Ni, Mo, Nb, N, Al, and if necessary, V, Ti, Cr, Ca or Ce in predetermined amounts with the rest iron and unavoidable impurities.