Effect of Martensitizing Temperature on Creep Strength of Modified 9Cr Steel

  • Tamura Manabu
    Department of Materials Science and Engineering, National Defense Academy
  • Kumagai Takuya
    Department of Materials Science and Engineering, National Defense Academy
  • Miura Nobuhiro
    Department of Mechanical Systems Engineering, National Defense Academy
  • Kondo Yoshihiro
    Department of Mechanical Systems Engineering, National Defense Academy
  • Shinozuka Kei
    Department of Materials Science and Engineering, National Defense Academy
  • Esaka Hisao
    Department of Materials Science and Engineering, National Defense Academy

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Abstract

A modified 9Cr-1Mo steel was cooled to a temperature between the Ms point and room temperature from the normalizing temperature and then directly heated to the tempering temperature. It was found that the time to rupture at 650 and 700°C of the steel heat-treated by the new heat treatment increased 2–3 times longer than that of the steel conventionally normalized and tempered. The microstructure of the improved steel was tempered martensite and the size of martensite blocks was larger than for the conventional heat treatment. The hardness of the improved steel was fully recovered after tempering. This strengthening is not caused by fresh martensite, but caused by the refining of M23C6 and V(C,N) particles in addition to the increase in the martesite block size, where M denotes metallic elements.

Journal

  • MATERIALS TRANSACTIONS

    MATERIALS TRANSACTIONS 52 (4), 691-698, 2011

    The Japan Institute of Metals and Materials

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