The Ni basic hammering alloy, the hammering part for the steam turbine plant and the boiler tube for the steam turbine plant, volt/bolt and steam turbine rotor null for the steam turbine plant

摘要

The invention relates to a nickel (Ni) based alloy for forging includes: 0.001 to 0.1 wt. % of carbon (C); 12 to 23 wt. % of chromium (Cr); 3.5 to 5.0 wt. % of aluminum (Al); 5 to 12 combined wt. % of tungsten (W) and molybdenum (Mo) in which the Mo content is 5 wt. % or less; a negligible small amount of titanium (Ti), tantalum (Ta) and niobium (Nb), the balance being Ni and inevitable impurities. As shown in the Figure, in the conventional alloys, the higher the temperature of the solid solution limit line of the ³' phase is, the larger is the amount of ³' phase precipitation at 700°C and therefore the greater the strength of the alloy. Since such presence of the ³' phase in an alloy seriously disserves the hot workability, the alloy needs to be hot worked at temperatures higher than the temperature of the solid solution limit line of the ³' phase. However, alloys having a temperature of the solid solution limit line of the ³' phase of higher than 1050 °C are practically difficult to hot work. Therefore, conventional alloys having a higher strength are more difficult to hot work and can be used only for precision casting. Since it is difficult to cast large-size products because of casting defects, such large-size products need to be forged. However, in conventional forging alloys, the area percentage of the ³' phase which can be precipitated at 700 °C is limited to less than about 25 %. In the alloys of the invention (Examples A to D), the ³' phase can be precipitated in an area percentage of 32 % or more at 700 °C even when the temperature of the solid solution limit line of the ³' phase is as low as about 1000 °C or less. Thus, the Ni based alloy for forging of the present invention has potential for greatly increasing the high temperature strength compared to conventional ones.