| 摘要 |
PURPOSE:To prepare low temp. steel for a welding joint part excellent in toughness, by subjecting a slab having a specific composition containing C, Si, Mn, Si, acid soluble Al and Cr or Mo and comprising the remainder Fe to hot rolling and heat treatment under a specific condition. CONSTITUTION:A slab containing 0.01-0.08% C, 0.05-0.50% Si, 0.05-0.90% Mn, 8.00-10,00% Ni, 0.01-0.10% acid soluble Al and, further, 0.10-1.00% Cr and/or 0.05-0.50% Mo and comprising the remainder Fe and inevitable impurities is subjected to hot rolling under a condition for imparting a cumalative draft of 60% or more at 50 deg.C or less and, directly after rooling, the rolled slab is tempered and succeedingly annealed at a temp. of a Ac1 transformation point or less. By this method, the toughness in both fine grain region and (alpha+gamma) two- phase region among welding heat parts can be especially improved and low temp. 9% Ni steel excellent in the toughness of a welding joint part can be obtained. |
