Manufacture of tempered high tensile steel sheet having excellent low temperature toughness

Abstract

Abstract PURPOSE: To manufacture tempered high tensile steel sheet excellent in low temp. toughness, by subjecting a steel material contg. a small quantity of Nb to the combination of controlled rolling and temper treatment under specific conditions. CONSTITUTION: Steel contg. <0.20% C, <1.0% Si, <2.0% Mn, 0.015W0.10% Nb, 0.015W0.10% soluble Al, in addition at least one member among the group <1.0% Cu, <10% Ni, <2% Cr, <1.0% Mo, <0.10% V, <0.10% Ti, <0.01% B is heated to ≥1,200°C where nitride and carbonitride of Nb form soln. sufficiently and is primarily rolled, the rolling being discontinued when intermediate thickness of the plate is attained. After cooled to ≤Ar 3 transformation temp., the steel is heated to 850W950°C and ≥Ac 3 transformation temp., then it is rolled secondarily at ≥65% reduction ratio based on the finish thickness of the plate. In that case, it is subjected to rolling ≥50% reduction ratio at least at ≤800°C, in addition, the secondary rolling is completed of 750W680°C. Finally, after cooled once to a prescribed temp., it is heated to just above the Ac 3 transformation temp. and is hardened and tempered. COPYRIGHT: (C)1981,JPO&Japio

Inventors

• 👤 Tamotsu Hashimoto
• 👤 Yasuo Otani

Bibliographic Details