| 摘要 |
PROBLEM TO BE SOLVED: To extremely improve tensile characteristic and shock characteristic which are necessary for a steam turbine moving blade, as well as a forging material by applying hot static water pressure treatment after cast molding out of stainless steel or heat resistant steel. SOLUTION: A moving blade casting for a steam turbine is cast-molded with stainless steel or heat resistant steel of a martensite base. In the case of a casting material, there may be cases where entrainment of gas, micro- porosity, micro-shrinkage exist in a casting, and frequently the casting material can be broken by comparatively low stress. In the moving blade casting for the steam turbine which is casting-molded, hot static water pressure treatment is applied. In the hot static water pressure treatment, the stress is loaded on a material which is softened in a high temperature, since inner defect is easily broken with low pressure. Load pressure is set as static water pressure, and deformation of casting is suppressed to a minimum. In a medium used for pressure load, an inert gas such as Ar is used for suppressing high temperature oxidized corrosion of a material. After that, heat treatment such as quenching and tempering is carried out, as necessary.
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