600 A Method of 600MPa Grade Tensile Strength Steel for Pressure Vessel Having Superior Toughness

摘要

PURPOSE: A manufacturing method of steel for pressure container having superior strength and impact toughness by simultaneously adding B and Ti to steel to lower carbon content and applying forcible cooling to normalizing heat treatment is provided. CONSTITUTION: The manufacturing method of steel for tensile strength 600 MPa class pressure container having superior toughness comprises the processes of normalizing a steel comprising 0.08 to 0.16 wt.% of C, 0.1 to 0.4 wt.% of Si, 0.8 to 1.8 wt.% of Mn, 0.2 to 0.8 wt.% of Mo, 0.3 to 0.8 wt.% of Ni, 0.0005 to 0.003 wt.% of B, 0.005 to 0.025 wt.% of Ti, 0.01 to 0.08 wt.% of Al, 0.010 wt.% or less of P, 0.010 wt.% or less of S, 0.010 wt.% or less of N and a balance of Fe and other inevitable impurities in the temperature range of Ac3 to 930 deg.C; and forcibly air cooling a central part of the normalized steel to an ordinary temperature at a cooling rate of 0.5 to 5 deg.C/sec.