Development of high strength 12% Cr ferritic steel for turbine rotor operating above 600 degrees C

An advanced 12% chromium ferritic steel has been developed for the high-temperature rotors in improved fossil-fired power plants. The development of this steel is based on the experimental studies of various 12% chromium heat resistant steels. Effects of alloy elements on the creep rupture strength have been investigated and the 10Cr-1.8W-0.7Mo-V-3Co-Nb-B steel was selected to be a hopeful candidate. This revealed the creep rupture strength was higher than that of 10Cr-1Mo-1W-V-Nb rotor steel being used at 593 degrees C. The producibility and properties of the new steel have been verified with the medium size trial forging manufactured from a 20 ton ingot. Although a few technical subjects are remaining, these are expected to be solved with the modification of the manufacturing process. This newly developed high strength 12% chromium ferritic steel is expected to be applicable to high-temperature rotors operating at 630 degrees C or above, and the significant improvement of thermal efficiencies would be obtained in fossil-fired power plants.