PRODUCTION OF THERMALLY REFINED HIGH TENSILE STRENGTH STEEL PLATE BY CONTINUOUS CASTING EXCELLENT IN TOUGHNESS

摘要

PROBLEM TO BE SOLVED: To stably obtain a thermally refined high tensile strength steel plate having excellent toughness by subjecting a continuously cost slab of a low alloy steel having a specified compsn. to heating and hot rolling into a steel plate, thereafter executing cooling, furthermore subjecting it to reheating and quenching under specified temp. conditions and subsequently executing tempering treatment. ;SOLUTION: A continuously cast slab of a low alloy steel contg., by weight, 0.07 to 0.16% C, ≤0.20% Si, 0.60 to 1.20% Mn, ≤0.50% Cu, 1 to 3% Ni, 0.30 to 1.20% Cr, 0.30 to 0.80% Mo, 0.01 to 0.1% V, 0.005 to 0.03% Nb or the like is heated to ≥1,050°C to allow the carbonitrides of V and Nb to enter into solid solutions, and thereafter, hot rolling is executed so as to regulate the draft to ≥20% and the rolling finishing temp. to ≥940°C. This plate is cooled to an ordinary temp., and treatment of executing reheating to the temp. range of the AC₃ point to 1,050°C and subsequently executing quenching is repeated for ≥ two times. Successively, it is quenched at the AC₁ point or below and is thereafter water-cooled to stably produce the high tensile strength steel plate excellent in yield strength and tensile strength.;COPYRIGHT: (C)1998,JPO