HIGH TENSION STEEL FOR MARINE STRUCTURE HAVING SUPERIOR TOUGHNESS AT WELD HEAT-AFFECTED ZONE AFTER STRESS RELIEF ANNEALING

摘要

PURPOSE:To obtain a high tension steel for a marine structure having superior toughness at its weld heat-affected zone after stress relief annealing by restricing the range of components and the equiv. amt. of carbon in a steel eliminating practically V and Nb. CONSTITUTION:The composition of a high tension steel for a marine structure is composed of, by weight, 0.08-0.14% C, 0.1-0.4% Si, 0.5-1.3% Mn, 0.2-0.7% Cr, 1-3% Ni, 0.15-0.5% Mo, 0.0005-0.0015% B, 0.04-0.1% Al, 0.008% P, 0.007% S and the balance Fe with inevitable impurities. The steel is eliminated practically from V and Nb. The carbon equiv. value (Ceq.) represented by the equation is regulated to =0.51%.