Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A high-nitrogen austenitic stainless steel, containing 0.005 mass %?C?0.25 mass %; 15.0 mass %?Cr?35.0 mass %; 0.2 mass %<Mn<10.0 mass %; 0.05 mass %?Mo?8.0 mass %; 0.01 mass %?Cu?4.0 mass %; 0.01 mass %?Ni<5.0 mass %; 0.8 mass %<N?1.8 mass %; Si?2.0 mass %; P?0.03 mass %; S?0.05 mass %; Al?0.030 mass %; 0?0.020 mass %, and the balance substantially including Fe and impurities, and having a PRE (=(Cr+3.3Mo+16N)/Mn (mass %)) of not less than 5 and a CRE (=Cr+1.5Mo+2N+Cu (mass %)) of not less than 27.