History of power plants and progress in heat resistant steels

During the last fifty years steam pressure and temperature in fossil-fired power plants have been continuously raised to improve thermal efficiency. Recent efforts for raising steam conditions are in response to the social demand for environmental protection as well as energy conservation concerns. Today the steam temperature of 600 degreesC for modern power plants equipped with swing load or sliding pressure demand functions has already been realized, and a goal for the future is the 630 degreesC to 650 degreesC class with ferritic steels. However the 600 degreesC to 630 degreesC class is possible for current construction, based on already developed materials that include ferritic steels for pipework and rotors. Numerous studies on heat resistant steels actively conducted since the early 1970s have allowed great progress in both 9-12 % Cr steels and austenitic steels. This paper presents a historical view of developments in steam pressure and temperature of fossil-fired power plants and allay design for heat resistant steels in the 20th century, particularly over the last several decades, as well as a survey of the current status of steel development for power plants, mainly with regard to creep strengthening and enhancement of corrosion resistance.