Production method for ring-rolled material of Fe—Ni-based superalloy

A method for producing a ring-rolled material of an Fe—Ni based superalloy having a composition including, by mass %, up to 0.08% of C, 50.0 to 55.0% of Ni, 17.0 to 21.0% of Cr, 2.8 to 3.3% of Mo, 0.20 to 0.80% of Al, 0.65 to 1.15% of Ti, 4.75 to 5.50% of Nb+Ta, up to 0.006% of B, and the balance of Fe with inevitable impurities, using ring rolling, the method comprising:

• a finishing ring rolling step, as a final step of the ring rolling, of heating a ring-shaped material for ring rolling to a temperature range of 900 to 970° C. and then maintaining the ring-shaped material for ring rolling in a temperature range of 900 to 970° C., while expanding a diameter of the ring-shaped material for ring rolling and also pressing the ring-shaped material for ring rolling in an axial direction thereof, by using a ring rolling mill having a pair of rolling rolls including a main roll and a mandrel roll, and a pair of axial rolls to inhibit recrystallization in the material for ring rolling and to obtain a ring-shaped ring-rolled material having an unrecrystallized or partially recrystallized structure and storing sufficient strain for avoiding an occurrence of abnormal grain growth (AGG) therein during a circularity correcting step described below;
• a circularity correcting step of improving a circularity of the ring-shaped ring-rolled material by expanding a diameter of the ring-shaped ring-rolled material by using a ring expander including a pipe-expanding cone and a pipe-expanding die to press the pipe-expanding die against an inner diameter side of the ring-shaped ring-rolled material, the circularity being determined by (DMAX−DMIN)/2 [mm], wherein DMAX is a maximum value of outer diameters of the ring-shaped ring-rolled material after the circularity correcting step, and DMIN is a minimum value of the outer diameter of the ring-shaped ring-rolled material after the circularity correcting step;
• and
• an intermediate ring rolling step, as a pre-step of the finishing ring rolling step, of heating the material for ring rolling to a temperature range of higher than 980° C. and up to 1010° C., and expanding a diameter of the material for ring rolling that has been heated at the temperature range and also pressing the material for ring rolling in an axial direction thereof by using a ring rolling mill having a pair of rolling rolls including a main roll and a mandrel roll, and a pair of axial rolls to have a fine-grained structure in the material for ring rolling by promoting recrystallization,
• wherein the ring-shaped ring-rolled material that has been rolled in the finishing ring rolling step is subjected to the circularity correcting step after being reheated in a temperature range of up to 960° C. excluding a temperature range of 600 to 760° C.