成果報告書詳細
管理番号20110000000529
タイトル*平成22年度中間年報 省エネルギー革新技術開発事業 挑戦研究 耐用温度800℃級蒸気タービン用新鍛造材料の開発
公開日2011/5/10
報告書年度2010 - 2010
委託先名株式会社日立製作所
プロジェクト番号P09015
部署名エネルギー対策推進部
和文要約和文要約等以下本編抜粋:1. 研究開発の内容及び成果等
石炭は貯蔵量が豊富であり、世界的に分散されていることからエネルギー資源の中では今後も比較的安定した価格で入手できることが期待される。しかし、従来の石炭火力ではCO2 排出量が多いため、環境問題の面からより一層の高効率化技術が望まれており、現在、700℃超級超々臨界圧発電(Advanced Ultra Super Critical; 以下A-USC と記載)の技術開発が欧米や日本で行われている。蒸気温度を上昇させることで効率の向上が可能となることから、従来、ボイラおよびタービンの高温部材に使用されていた鉄鋼材料を、A-USC では高温強度に優れたNi 基超合金を用いることで、蒸気温度を大幅に向上させ、効率を大幅に向上させている。現在、耐用温度が700~750℃級のNi基超合金について研究開発が行われているが、蒸気温度を750℃~800℃に向上させ、さらなる高効率化を図るためには、800℃級の蒸気に耐える材料の開発が必要となる。しかし、鍛造材料の高温強度と大型部材の製造性は相反する要素であるため、既存材料の改良材では耐用温度は750℃程度が限界である。本研究では状態図を駆使した合金設計により高温強度と大型部材製造性を両立する革新鍛造材料を開発し、A-USC のさらなる高効率化に寄与することを目的として以下の研究を行った。
英文要約Title:Energy Conservation Innovetive Technology Development Project/Challenge Phase/Development of New Wrought Material for over 800°C Class Steam Turbine (FY2010-FY2011)FY2010 Annual Report
It is recognized that the CO2 emission is large in the conventional coal fired power generation although coal can be supplied by stable price since the reserve is bountiful and is not localized. Therefore, the high efficiency technology is required and currently US, Europe and Japan are developing Ni-based superalloys for 700°C-class advanced ultra super critical (A-USC) plants. For further improvement of energy efficiency, it is necessary to develop materials to be applied at 800°C, however, it is not easy to satisfy both the high-temperature strength and manufacturability in one material. This project is aimed at 800°C-class wrought superalloys newly designed based on phase diagram. /1. Development of 800°C-class Large Scale Wrought Alloy (Alloy A)/ a) Alloy design: Candidate compositions for large scale wrought alloy were determined to achieve excellent high temperature strength and manufacturability. b) Trial making of Large Forgings: 3ton billet was successfully manufactured by VIM (Vacuum Induction Melting) and VAR (Vacuum Arc Re-melting) process. The VAR ingot with 800mm diameter was forged into round bar shape. The 10^5h creep strength at 800°C of the billet is estimated to be 90MPa. c) Trial making of model parts of steam power plants: Small test pieces with boiler tube shape were taken from the billet and welding tests were carried out to evaluate weldability and high temperature properties of welded joints. Filler metal is also developed in this project in view of strength, weldability and cold workability into the wire. Creep strength of the welded joint is comparable to the base metal. Harmful phases such as sigma phase are not confirmed within the welded area. Boiler tubes, bolts and blades are also planned to make from the billet in FY2011.
/3. Evaluation of New Material/ a) Microstructural stability: Microstructure of the creep test pieces and welded joint were observed by optical and electron microscopes. The developed alloy exhibits the very good phase stability and microstructural change were not remarkable durign the creep tests. b) High temperature strength: High temperature properties of the large forging and welded joint were evaluated by tensile and creep tests. As mentioned above, creep strength reaches the development target (10^5h creep strength at 800°C > 80MPa).
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