Mitsuo Kawai

Development of Integral High-Pressure—Low-Pressure Combination Rotor Forgings

Integral high pressure (HP)-low pressure (LP) combination rotor forgings for single-cylinder turbines used under the steam condition over 773 K require good toughness and elevated temperature strength. Conventional Ni-Cr-Mo-V or Cr-Mo-V steel forgings are undesirable from the viewpoint of material properties. We developed integral HP-LP combination rotor forgings by alloy modifications (niobium and nickel addition) based upon Cr-Mo-V steel and the application of differential heat treatment. An actual dimensional prototype sample forging (1650 mm in diameter) was manufactured and evaluated. The forging exhibited high quality, and superior creep rupture strength at the HP zone and excellent toughness at the LP zone were obtained simultaneously. These developed rotor forgings have been applied for several turbine units of about the 100-MW class.

Oxidation Resistance of Sintered SUS 304 Stainless Steel

Oxidation resistance of sintered SUS304 stainless steel and the effect of calorizing were studied.The results obtained are summarized as follow:1) Oxidation resistance of sintered compacts at 500°C and 700°C increases with increasing of relative density.2) Oxidation resistance at 900°C of sintered compacts with relative density of 96-98% is superior to that of other sintered compacts and of the specimens from molten metal.3) Oxidation resistance of sintered compacts is improved by calorizing.4) Bending strength of sintered compacts decreases very slightly after being oxidized.