To provide a manufacturing method of a nozzle diaphragm of an axial flow turbine that can prevent deformation of and degradation in surface roughness of a nozzle blade by eliminating welding deformation and residual stress.
The manufacturing method of a nozzle diaphragm of an axial flow turbine has a slit forming step of arraying a plurality of radially extending slits 4 in an annular passage part ring 3 at intervals along the circumference of the passage part ring, a welding step of fixedly welding an outer diaphragm ring 1 and an inner diaphragm ring 2 to the respective outer side and inner side of the passage part ring after the slit forming step, a heat treatment step of relaxing residual stress or strain caused in the welding step, and a nozzle passage forming step of forming nozzle passages by applying electric discharge machining or electrochemical machining to slit surfaces after the heat treatment step.
TAKAYASU SUSUMU
ASHIBA TAKASHI
MINAMI KATSUNORI
