〔83〕フェライト鋼の高温強度と靱性

抄録

This paper describes the elevated temperature strength, toughness and alloy design of ferritic steels (dual-phase). For the development of ferritic steels which show excellent characteristics in creep rupture strength, toughness, weldability, resistance to oxidation and corrosion resistance to steam at the service temperature of 550-650°C, extensive studies have been carried out. The effects of Cr, Mo, V, Nb, C and Si on the creep rupture properties and Charpy impact properties of ferritic steels were investigated. The steel obtained from this work, 9Cr-1.5Mo-0.15V-0.05Nb steel, exhibits at least three times as much 10⁵h creep rupture strength at 600°C as compared with 2% Cr-1 Mo steel and conventional 9Cr-IMo steel, and is superior to HT-9 by approximately 50%. This steel also shows higher resistance to embrittlement during service. Moreover, the effect of W on creep rupture properties was investigated, and TB12 steel containing W (12Cr-0.5Mo-1.8 W-0.2V-0.05Nb) was developed. This steel exhibits twice as much 10⁵h creep rupture strength at 650°C as compared with modified 9Cr-1Mo steel and is superior to SUS 316 stainless steel. These new-steels would be useful for boiler tubes, steam generator tubes of fast breeder reactors and first wall of nuclear fusion reactors.