PURPOSE: To obtain a titled nickel-base alloy which has various strength, ductility and toughness and is highly resistant to stress corrosion cracking and hydrogen cracking by specifying the selection of the component system for the Ni- base alloy and respective conditions for hot working, heat treatment and aging treatment.
CONSTITUTION: An Ni-base alloy consisting of ≤0.050% C, ≤0.50% Si, ≤2.0% Mn, 45W60% Ni, 18W27% Cr, ≤0.40% Ti and ≥1 kind of 2.5W5.5% Mo and ≤11% W, ≤0.30% Al, ≤0.15% P, ≥1 kind of 2.5W5.0% Nb and ≤2.0% Ta, ≤0.0050% S, ≤0.030% N and the balance inevitable impurities and Fe is treated in the following way: The Ni-base alloy is subjected to hot working of ≥50% reduction in area at 1,200W800°C. The Ni-base alloy is then cooled at a cooling rate above air cooling after holding for 10minW5.0hr at 1,000W1,200°C and is thereafter subjected to 1W2 times of an aging treatment for 1W200hr at 500W 750°C, by which the titled Ni-base alloy having excellent resistance to stress corrosion cracking, etc. in environment contg. ≥1 kind among H2S, CO2 and Cl- is obtd.
OKADA YASUTAKA
YOSHIKAWA KUNIHIKO
KUDOU TAKEO
