蒸気タービン部品のウォータジェット切断加工技術の開発

Abstract

Electrical discharge machines (EDM) have conventionally been used for cutting the nozzle blade holes in steam turbine diaphragm spacer rings due to high precision requrements. Problems assosiated with this method are slow cutting speed and a potential for fire resulting from the usage of oil. The abrasive water jet (AWJ) machine avoids these problems makes it possible to cut three-dimensional curved work pieces in the horizontal position. This is performed by utilizing two heads with each head featuring simultaneous control in five axes. AWJ technology makes relatively high speed cutting possible while maintaining high precision requirements. The results obtained are summarized as follows;(1) Abrasive water jet cutting technology and equipment have been established to perform precision cutting of three-dimensional curved surfaces while obtaining higher productivity than the conventional EDM method. The use of two cutting heads with individual simultaneous cotrol in five axes makes this technology possible.(2) A significant man hour reduction has been achieved as a result of increased productivity by utilizing high speed cutting (10 to 50 mm/min) along the nozzle blade profiles.(3) AWJ cut surfaces exhibit approximately 1/5 the surface roughness of conventional EDM cut surfaces. The accuracy of the cut hole geometry satisfies specification requirements for maximum allowable gap between the nozzle and hole profile.(4) Because no oil is used with AWJ cutting, the danger of fire has been eliminated and environmental compatability is improved.