Journal of Materials Science

, Volume 24, Issue 4, pp 1357–1362 | Cite as

Development of mechanical properties of structural high-carbon low-alloy steels through modified heat treatment

  • Yoshiyuki Tomita


The modified heat treatment, which produces a mixed structure of martensite and lower bainite through short-term isothermal transformation at just above the martensitic transformation temperature,M s temperature, followed by oil quenching (after conventional austenitization), has been applied to three high-carbon low-alloy steels with different levels of nickel and chromium contents at similar molybdenum levels, in which carbon was allowed to replace relatively expensive additions of nickel and chromium, for their ultra-high strength application. The significant conclusions are as follows: an ultra-high strength steel of 1900 M Pa yieldstress grade with a high toughness level can be obtained when about 60 vol % lower bainite is associated with 473 K tempered martensite of 0.60% C-1.80% Ni-0.80% Cr-0.25% Mo steel. If approximately 25 vol % lower bainite appears in 673 K tempered martensite of the steel, a 1700 M Pa yield-stress grade steel with high toughness and moderate ductility levels can be attained. However, alloying nickel is essential to some extent for development of the mechanical properties with the modified heat treatment suggested in the present work.


Martensite Bainite Martensitic Transformation High Toughness Isothermal Transformation 
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Copyright information

© Chapman and Hall Ltd. 1989

Authors and Affiliations

  • Yoshiyuki Tomita
    • 1
  1. 1.Department of Metallurgical Engineering, College of EngineeringUniversity of Osaka PrefectureOsakaJapan

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