MANUFACTURE OF NONTEMPER HIGH TENSILE STEEL PLATE SUPERIOR IN WELDABILITY AND LOW TEMPERATURE TOUGHNESS

摘要

PURPOSE:To manufacture the titled steel plate, by rolling and cooling a steel to which a small quantity of Nb is entered into solid solution under specified conditions. CONSTITUTION:Steel ingot contg. by weight 0.005-0.15% C, 0.1-0.5% Si, 0.8-2.0% Mn, 0.005-0.1% Nb, 0.005-0.08% Al, 0.008% S, or further at least one kind among 0.1% V, =0.5% Cu, Cr, Ni, Mo respectively, and at least one kind among 0.010% REM is manufactured. Said ingot is heated to temp. at which at least 0.005% Nb in a steel is entered into solid solution, then hot rolled at Ar3+150 deg.C-Ar3 point range by =50% draft to plate material. Said plate is cooled rapidly to ferrite transformation stopping temp. - 500 deg.C range at 4-30 deg.C/sec rate, further cooled slowly from the temp. to 500-200 deg.C range at 1-3 deg.C/sec rate, thereafter air cooled to room temp.