| 摘要 |
PURPOSE:To obtain a steam turbine rotor material which has raised strength and toughness of the bore inner surface by quenching and tempering a bore- worked rotor material, and thereafter, executing the quenching and tempering of a high frequency heating to only the bore inner surface, and refining it. CONSTITUTION:The whole of a stem turbine rotor material 1 which has formed a bore 2 passing through a shaft center is quenched and tempered, and thereafter,a high frequency induction coil 3 is inserted into the bore 2. This coil 3 is constituted of double spiral coils 31, 32, both of them have a hollow section, and a cooling medium blowing nozzle is provided on the periphery of the coil 31. The bore 2 inner surface is held for a prescribed time at about 920-950 deg.C by a high frequency induction heating, and thereafter, the overall length of the bore 2 inner surface is brought to a forced cooling uniformly by blowing air from a nozzle hole. Subsequently, the bore 2 inner surface is held for a prescribed time at about 670-730 deg.C again by a high frequency heating, and thereafter, air-cooling is executed. In this way, the bore 2 inner surface organization becomes bainite, and the strength and toughness of the same degree as the outside peripheral part of the rotor material 1 is obtained.
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