析出強化型 15Cr-26Ni-1.25Mo Fe 基耐熱合金の高温特性に及ぼす時効処理の影響(<特集>新しい耐熱鋼)

概要

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Optimum aging condition suitable to large parts made of low carbone low titanium 15Cr-26Ni-1.25Mo iron-base alloys was examined. The alloys are beneficial to making rotors for ultra-super critical steam turbine for gegerator. After solution treatment, the alloys were aged at 740℃ for 1 through 64h, or 700 to 780℃ for 16h. The experimental results are summarized as follows. 1) Aging at a range of 720 to 780℃ for 16h yielded spheroidal γ′ particles. But, after aging at 780℃ for 16h coarsened γ′ particles precipitated on the grain boundary. 2) Superior tensile properties were resulted after aging at 740℃ for 16-32h or 740-760℃ for 16h. 3) Creep properties at 650℃ were affected by aging temperature. The long-term creep strength was hardly affected by the aging temperature in the range of 710 to 760℃ for 16h. Creep ductility was significantly improved with elevating aging temperature up to 760℃. 4) Low cycle fatigue strength at 650℃ was not affected by the aging conditions when tested under constant total strain amplitude in this work. 5) A drum with a weight of 4.5t was produced and solutionized and aged at 740℃ for 32h. The test pieces were cut from typical four locations of the drum, and creep tested at 650℃. It was confirmed that dispersion of creep strength with respect to the location was negligible.
社団法人日本鉄鋼協会の論文
1990-07-01