著者

角屋 好邦 馬越 龍太郎 河合 久孝 守中 康治 三上 真人 添田 暉平

出版者

社団法人日本鉄鋼協会

雑誌

鐵と鋼 : 日本鐡鋼協會々誌 (ISSN:00211575)

巻号頁・発行日

vol.87, no.8, pp.564-569, 2001-08

被引用文献数

1

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The 2.25CrMoV steel is applied to conventional combined high-pressure (HP) and low-pressure (LP) rotor forging, and it has excellent creep properties and toughness at 538℃ conventional steam temperature. However, at 566℃ steam temperature, it is required to improved the properties of the rotor forgings. The effects of chemistry on toughness and creep rupture strength have been investigated on the 9CrMoV base materials for the purpose of developing a new HP-LP rotor material for 566℃ steam temperature. Thus 9.8Cr1.4Mo1.0NiVNbN steel, named HLP9F, with higher toughness and creep rupture strength compared with conventional 2.25CrMoV steel, has been developed. A trail HP-LP rotor forging with the diameter of LP section of 1800mm and that of HP section of 1200mm has successfully been manufactured through the VCD process from 68t ingot. In spite of a large ingot, neither chemical composition change nor eutectic Nb(C, N) formation could be recognized. The rotor, furthermore, exhibited satisfactory quality in toughness and creep rupture strength. This rotor material is suitable to the HP-LP rotor material for advanced combined cycle steam turbine.

著者

倉田 征児 植田 茂紀 野田 俊治 山本 隆一 角屋 好邦 中野 隆 田中 良典 馬越 龍太郎

出版者

大同特殊鋼株式会社

雑誌

電気製鋼 (ISSN:00118389)

巻号頁・発行日

vol.79, no.3, pp.239-244, 2008-08-25 (Released:2008-12-26)

参考文献数

7

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Advanced 700 ℃ class steam turbines require using Ni-based superalloys instead of conventional ferritic 12Cr steel which is insufficient in creep strength and oxidation resistance above 650 ℃. The superalloys, however, possess quite higher coefficient of thermal expansion (CTE) than the 12Cr steel. So far authors examined the influence of alloying elements on CTE and the high temperature strength of the Ni-based superalloys. Consequently “LTES700R” was developed for steam turbine, which has low CTE and sufficient creep strength. LTES700R is corrected Mo amount to inhibit the Laves phase and added W to reduce CTE instead of Mo within the range that alfa-tungsten does not precipitate. In addition, Al and Ti, which form gamma-prime, were increased to make up for deteriorating of the strength by Laves phase free. The creep rapture strength of LTES700R manufactured by laboratory forging is higher than that of advanced 12Cr steel owing to be strengthened by gamma-prime [Ni3(Al, Ti)] phase precipitates. The CTE of LTES700R is lower than that of Refractaloy 26®, and slightly higher than that of 12Cr steel. The phase of LTES700R is stable until 5000 hr heating from 550 ℃ to 750 ℃.