Heat-resisting alloy for 700-DEG C ultra-supercritical steam turbine rotor and preparation method thereof

The invention relates to heat-resisting alloy for a 700-DEG C ultra-supercritical steam turbine rotor and a preparation method thereof, and belongs to the technical field of heat-resisting alloy. The alloy comprises the following ingredients by weight percent: 0.04 to 0.06 percent of C, 19 to 21 percent of Cr, 8.6 to 9.0 percent of Mo, 11 to 13 percent of Co, 0.40 to 0.80 percent of W, 1.10 to 1.30 percent of Al, 1.20 to 1.40 percent of Ti, 0.20 to 0.50 percent of Nb, less than or equal to 0.15 percent of Fe, 30 to 50ppm of B, 0.01 percent of Zr, 0.002 percent of Mg and the balance of Ni and impurities; wherein, the content of Al and Ti needs to satisfy the following condition: (Al+Ti) is more than or equal to 2.5 percent and less than or equal to 2.6 percent, and Ti/Al is more than or equal to 1.0 or less than or equal to 1.1. A VIM, VAR and ESR triplet process is used for smelting the alloy, soft-sheath forging is adopted, and the heat-resisting alloy has advantages that the comprehensive performance is excellent and the alloy is suitable for manufacturing the 700-DEG C ultra-supercritical steam turbine rotor.