METHOD FOR PRODUCING NI-BASED SUPERALLOY MATERIAL

The present invention relates to a method for producing a precipitation strengthened Ni-based superalloy material having a predetermined composition, containing a blooming forging step of performing a forging at a temperature range of from Ts to Tm and performing an air cooling to form a billet having an average crystal grain size of #1 or more, an overaging thermal treatment step of heating and holding the billet at a temperature range of from Ts to Ts+50°C and slowly cooling it to a temperature of Ts or lower, and a crystal grain fining forging step of performing another forging at a temperature range of from Ts-150°C to Ts and performing another air cooling, in which Ts is from 1,030°C to 1,100°C, and an overall average crystal grain size is #8 or more after the crystal grain fining forging step.