In quenching and tempering heat treatment of 9% Ni steel, one of the most important factors affecting the notch toughness at low temperatures is the tempering temperature, fundamentally based on the true Ac sub 1 transformation temperature. Another is the cooling rate dependence after tempering: the faster the cooling rate becomes, the higher the notch toughness is. From the above factors, this investigation has experimentally clarified the following phenomena: 1. A tempering temperature lower than the true Ac sub 1 transformation temperature provides high notch toughness. This effect is considered to be due to the formation of stable ferrite in the matrix. It is concluded that the austenite precipitating at a tempering temperature does not contribute to the notch toughness. 2. Even when the notch toughness is lowered by a slow cooling rate, it can easily be regained by a rapid cooling rate after the subsequent tempering heat treatment. This effect is considered to be related to carbide behavior in the matrix.

  • Corporate Authors:

    Japan Association for Technical Information

    4-7-107, Yamazaki-cho, Machida City
    Tokyo 194-01,   Japan 
  • Authors:
    • Saiga, Y
    • Fukagawa, M
    • Ito, S
  • Publication Date: 1973

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Filing Info

  • Accession Number: 00054394
  • Record Type: Publication
  • Source Agency: Department of Transportation
  • Files: TRIS, USDOT
  • Created Date: Jun 18 1974 12:00AM