Effects of Alloying Elements on the Hardenability, Toughness and the Resistance of Stress Corrosion Cracking in 1∼3 mass%Cr Low Alloy Steel

Abstract

The effects of alloying elements on the hardenability, toughness and the resistance of stress corrosion cracking have been evaluated in the 1∼3mass%Cr low alloy steels for 1600mmφ level large-sized turbine rotor forging for geothermal power generation. The chemical composition suitable for the rotor forging which was satisfied with the required material properties and which reduced the C-segregation in the center portion of the ingot was chosen under the restrictive condition on the upper limit of Ni and Cr contents in turbine rotor under the geothermal corrosive environment. The 8 ton sand mold ingot was manufactured and the reduction of the C-segregation was verified in the selected chemical composition. Finally selected 2.25Cr-0.9Ni-0.6Mo-0.25V-0.15Si-1.0Mn-0.25C steel (mass%) is hopeful as the chemical composition for the large-sized turbine rotor forging for geothermal power generation.