STEEL MATERIAL FOR MULTI-LAYER BUILDUP WELDING EMPLOYING HIGH INTERPASS TEMPERATURE, ITS MANUFACTURING METHOD AND MULTI-LAYER BUILDUP WELDING METHOD EMPLOYING HIGH INTERPASS TEMPERATURE

摘要

PROBLEM TO BE SOLVED: To provide a steel material for high interpass temperature welding which has sufficient HAZ toughness even in the case where interpass temperature reaches ≥350°C, its manufacturing method and a welding method using it.;SOLUTION: The following steps are successively performed: a step where ferromanganese or silicomanganese is added to molten steel tapped from a converter to carry out pre-deoxidation in such a way that dissolved oxygen content becomes 0.0030 to 0.0120% (by mass, the same applied to the following); a step where REM is added to regulate the dissolved oxygen content to 0.0010 to 0.0050% and also the residual content of REM in the steel to 0.0010 to 0.03%; and a step where the composition is regulated to a final steel composition consisting of 0.03 to 0.15% C, 0.05 to 0.50% Si, 0.5 to 2.0% Mn, ≤0.03% P, 0.0005 to 0.0080% S, 0.0010 to 0.03% REM and the balance Fe with inevitable impurities. The resultant molten steel is cast into a slab, and the slab is heated, hot rolled into final product shape and then cooled to ≤500°C at a rate of ≥1 °C/s and also recuperation temperature after cooling stoppage is made to ≤100°C to manufacture the steel material.;COPYRIGHT: (C)2004,JPO