MANUFACTURE OF NONTEMPER HIGH TENSILE STEEL PLATE HAVING HIGH YIELD STRENGTH AND SUPERIOR WELDABILITY AND LOW TEMPERATURE TOUGHNESS

摘要

PURPOSE:To manufacture the titled steel plate, by hot rolling a steel slab having a specified compsn. to plate material, then cooling acceleratedly at the first step, successively cooling acceleratedly at the second step, then air cooling said plate. CONSTITUTION:The steel contg. by weight, 0.005-0.20% C, 0.05-0.50% Si, 0.5-2.0% Mn, 0.005-0.08% Al, 0.01% S, 0.008% N, or further at least one kind among 0.04% Ti, 0.10% V, 0.5% Cu, 1.0% Ni, 0.5% Cr, 0.5% Mo, and one kind among 0.010% Ca, 0.01% REM is manufactured. The steel slab is hot rolled at Ar3+70 deg.C-Ar3 point range at =30% draft to plate material. Immediately thereafter, the plate is cooled to ferrite transformation stopping temp. - 500 deg.C range by 4-30 deg.C/sec rate, further cooled from the temp. to 500-200 deg.C at 1-3 deg.C/sec rate, then air cooled to room temp.