Historical Overview of Improving Cleanliness of Rotor Steels for Electric Utility Applications

Abstract Improved cleanliness is perhaps the only approach that results in simultaneous improvement in strength and ductility at elevated temperatures as well as toughness at low temperatures of steels. In addition, superclean steels in which manganese and silicon have also been reduced, provide greater resistance to stress corrosion cracking than conventional steels. Major projects are underway worldwide to promote the use of clean/superclean steel rotor and disk forgings, both for low temperature and for high temperature applications in steam and combustion turbines. An international workshop sponsored by EPRI was held in 1995 in London, at which turbine manufacturers and steelmakers discussed ongoing activities with respect to clean steels. This paper summarises EPRI sponsored research on rotor steel chemistries and provide an overview of developments over the last 15 years.