TEMPALOY A-3 tubes with high corrosion resistance for high temperature use

Coal fired thermal power plants are recently under study in Japan and foreign countries. The use of ultra super critical steam condition (USC) has promoted severe high temperature corrosion. For this reason, in the conventional 18-8 stainless steels, the Cr content is raised so as to obtain heat resistant steel with improved hot corrosion resistance. The development of high strength boiler tubes having excellent corrosion resistance dominates an important position in USC project. The development has also been taken up by EPRI (Electric power research center in the U.S.) Project Task 13 of the U.S. NKK has also carried out research to modify and improve Alloy 800H (21Cr-32 Ni-Al-Ti). Since it has successfully developed a steel highly resistant to high temperature corrosion and excelling in creep rupture strength, this paper describes the details.