Method of manufacturing a rotor without increasing the strength steam turbine rotor, as well as stress corrosion cracking

摘要

PROBLEM TO BE SOLVED: To provide a heat treatment method for manufacturing a monoblock, low alloy steel rotor for a low pressure steam turbine.;SOLUTION: In this heat treatment method, the rotor is austenitized at a substantially uniform treatment temperature of about 840°C, the rotor is hardened, and differentially tempered at different locations in the axial direction of the rotor. The rotor is tempered in a furnace divided into a plurality of regions by refractory boards so as to maintain different temperatures in respective regions. By lowering the tempering temperature at one or more locations in the axial direction, a condition higher than normal strength is achieved. The one or more axial locations tempered at lower temperature is close to a location less susceptible to stress corrosion cracking, and the strength of the rotor can be increased without increasing net susceptibility to stress corrosion cracking.;COPYRIGHT: (C)2002,JPO