| 摘要 |
PURPOSE:To improve strength and corrosion resistance in a severe corrosive environment, by subjecting an austenitic Ni-Cr steel with a specific composition to solution heat treatment under specific conditions and then to aging treatment in two stages. CONSTITUTION:As a steel material to be used under highly corrosive environment such as sour-gas environment, an austenitic Ni-Cr steel containing, by weight, <0.03% C, <1.0% Si, 0.01-2.0% Mn, 13.5-16% Cr, 24-27% Ni, 1.0-1.5% Mo, 1.9-2.35% Ti, 0.0005-0.01% B, and <0.35% Al is used and the product made of this steel stock is subjected, once or more, to solution treatment in which heating is applied at 900-1,050 deg.C for 3min-10hr. Subsequently, as a first aging treatment, the above-mentioned product is heat-treated at 720-780 deg.C for 30min-10hr and cooled down to 600-700 deg.C, and then, as a second aging treatment, maintained at 600-700 deg.C for 5-20hr to undergo two- stage aging treatment. In this way, an Fe-base precipitation hardening-type alloy steel excellent in strength and corrosion resistance can be obtained. |
