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Study of the isothermal transformation of ductile iron with 0.5% Cu by electrical resistance measurement

  • B. Y. Lin
  • E. T. Chen
  • T. S. Lei
Materials Characterization

Abstract

A computer-controlled system for measuring electrical resistance has been developed and used to study the isothermal transformation of austenite in a ductile iron (3.31 % C, 3.12 % Si, 0.22 % Mn, 0.55 % Cu). The ability of the technique to follow the isothermal decomposition of austenite was established by measurements on an AISI4340 steel. The times at which the austenite decomposed to primary ferrite, pearlite, and bainite were accurately detected. In the ductile iron, the formation of pearlite and of bainite was easily detected, and an isothermal transformation diagram was constructed from the results. The temperature range for the formation of bainite is especially important in producing austempered ductile iron (ADI) and was mapped. An initial stage of decomposition of austenite to ferrite and high-carbon austenite is followed by a time delay; then the high-carbon austenite decomposes to bainite. The formation of ADI requires austempering to a structure of ferrite and high-carbon austenite, then quenching to retain this structure, thus avoiding the formation of bainite. This is achieved by isothermal transformation into the time-delay region. For the ductile iron studied here, this time region was about 2.6 h at 400 °C and increased to 277 h at 300 °C.

Keywords

computer-controlled ductile iron electrical resistance isothermal transformation 

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References

  1. 1.
    W.C. Johnson and B.V. Kovacs, The Effect of Additives on Eutectoid Transformation of Ductile Iron,Metall. Trans. A, Vol 9A, 1978, p 219–229CrossRefGoogle Scholar
  2. 2.
    E.M. Pan, M.S. Lou, and C.R. Loper, Jr., Effects of Copper, Tin, and Manganese on the Eutectoid Transformation of Graphite Cast Irons,AFS Trans., Vol 95, 1987, p 819–840Google Scholar
  3. 3.
    P.A. Blackmore and R.A. Harding, The Effect of Metallurgical Process Variables on the Properties of Austempered Ductile Iron,J. Heal Treat., Vol 3 (No. 4), 1984, p 310–325CrossRefGoogle Scholar
  4. 4.
    J.F. Janowak and R.B. Gundlach, Development of A Ductile Iron for Commercial Austempering,AFS Trans., Vol 91, 1983, p 377–388Google Scholar
  5. 5.
    R.C. Voigt, Microstructural Analysis of Austempered Ductile Cast Iron Using the Scanning Electron Microscope,AFS Trans., Vol 91, 1983, p 253–262Google Scholar
  6. 6.
    M. Johansson, Austenitic-Bainitic Ductile Iron,AFS Trans., Vol 85, 1977, p. 117–122Google Scholar
  7. 7.
    D.J. Moore, T.N. Rounds, and K.B. Rundman, The Effect of Heat Treatment, Mechanical Deformation and Alloying Element Additions on the Rate of Bainite Formation in Austempered Ductile Iron,J. Heat Treat., Vol 4 (No. 1), 1985, p 7–24CrossRefGoogle Scholar
  8. 8.
    D.J. Moore, T.N. Rounds, and K.B. Rundman, Structure and Mechanical Properties of Austempering Ductile Iron,AFS Trans., Vol 93, 1985, p 705–718Google Scholar
  9. 9.
    D.J. Moore, B.S. Shugart, K.L. Hayryne, and K.B. Rundman, A Microstructure Determination of Isothermal Transformation Diagram in a Low-Alloy Ductile Iron,AFS Trans., Vol 98, 1990, p519–526Google Scholar
  10. 10.
    D.J. Moore, G.P. Faubert, E.D. McCarty, D.J. Ellerbrock, and K.B. Rundman, Isothermal Transformation Diagram in a Heavy-Section, High-Alloy Ductile Cast Iron,AFS Trans., Vol 98,1990, p 449–457Google Scholar
  11. 11.
    K. Yasue, T. Nisio, Y. Yamada, and Y. Obata, Effects of Alloying Elements and Austenitizing Conditions on the Isothermal Transformation Diagram of Ductile Cast Iron,Imono (J. Jpn. Foundrymen’s Soc), Vol 63, Dec 1991, p 595–600Google Scholar
  12. 12.
    J.P. Chobaut, P. Brenot, and J.M. Schissler, Secondary Martensite Formation during the Tempering of Bainite S. G. Cast Iron,AFS Trans., Vol 96, 1988, p 475–480Google Scholar
  13. 13.
    B.Y. Lin, “A Study on Austemperability of Ductile Iron,” Master’s thesis, National Taiwan Institute of Technology, 1987Google Scholar
  14. 14.
    Y.J. Park, R.B. Gundlach, and J.F. Janowark, Monitoring the Bainite Reaction during Austempering of Ductile Steel by Resistivity Measurement,AFS Trans., Vol 95, 1987, p 411–416Google Scholar
  15. 15.
    B.Y. Lin, E.T. Chen, and T.S. Lei, “The Use of Electrical Conductivity on the Study of the Austemperability of Ductile Irons,” NSC 80-0405-E011-08, National Science Council, Taipei, Taiwan, Republic of China, 1991Google Scholar
  16. 16.
    B.Y. Lin, E.T. Chen, and T.S. Lei, The Use of Electrical Conductivity on the Study of the Austemperability of Ductile Irons,Proc. 1992 Ann. Conf. Chinese Society for Materials Science, H.K. Wu, Ed., Chinese Society for Materials Science, Taipei, Taiwan, Republic of China, 1992, p 44Google Scholar
  17. 17.
    G.T. Eldis, A Critical Review of Data Source for Isothermal Transformation and Continuous Cooling Transformation Diagram,Hardenability Concepts with Application to Steel, D.V. Doane and J.S. Kirkaldy, Ed., Metallurgical Society of AIME, 1978, p 126–148Google Scholar
  18. 18.
    P.M. Unterweiser. H.E. Boyer, and J.J. Kubbs,Heat Treater’s Guide: Standard Practices and Procedures for Steel, American Society for Metals, 1982, p 161Google Scholar
  19. 19.
    G. Krauss,Principles of Heat Treatment of Steel, American Society for Metals, 1980, p 172Google Scholar
  20. 20.
    K. Röhrig and W. Fairhust,Die Wärmebehandlung des Gusseisens mit Kugelgraphit und die Umwandlungsschaubilder, No.6, Deutscher Giesserei Verband, Dusseldorf, 1979Google Scholar

Copyright information

© ASM International 1995

Authors and Affiliations

  • B. Y. Lin
    • 1
  • E. T. Chen
    • 1
  • T. S. Lei
    • 1
  1. 1.Department of Mechanical Engineering and TechnologyNational Taiwan Institute of TechnologyTaipeiTaiwan

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