Method of producing Ni-based superalloy

1. A method of producing a Ni-based superalloy, comprising:

using a hot working material which has a composition consisting of, in mass %, 0.001 to 0.050% of C, 1.0% to 4.0% of Al, 3.0% to 7.0% of Ti, 12% to 18% of Cr, 12% to 30% of Co, 1.5% to 5.5% of Mo, 0.5% to 2.5% of W, 0.001% to 0.050% of B, 0.001% to 0.100% of Zr, 0% to 0.01% of Mg, 0% to 5% of Fe, 0% to 3% of Ta, 0% to 3% of Nb, and the remainder of Ni and inevitable impurities, and in which a solvus temperature of a γ′ phase is equal to or higher than 1050° C.,

a preliminary heating step of performing heating in a temperature range that is 980° C. to 1050° C. and has an upper limit set to be −30° C. from the solvus temperature of the γ′ phase, for 10 hours or longer; and

a hot working step of performing hot working on the hot working material after the preliminary heating step, at a working speed having a strain rate of 2.0/second or more in a temperature range that is 980° C. to 1050° C. and has an upper limit set to be −30° C. from the solvus temperature of the γ′ phase.

2. The method of producing a Ni-based superalloy according to claim 1 , wherein in the hot working step, the strain rate of the hot working is 8.0/second or more.

3. The method of producing a Ni-based superalloy according to claim 1 , wherein the hot working material has a metal structure in which a grain size of a matrix is equal to or more than 8 in ASTM grain size number.

4. The method of producing a Ni-based superalloy according to claim 1 , wherein a γ′ precipitated amount of the Ni-based superalloy is more than 45%.