STP1523: A New Method to Study the Effect of Cooling Rate on the Decomposition of Austenite in Advanced High Strength Sheet Steels

    Cho, K.
    Researcher, Univ. of Pittsburgh, Pittsburgh, PA

    Garcia, C. I.
    Research Professor, Univ. of Pittsburgh, Pittsburgh, PA

    Hua, M.
    Research Assistant Professor, Univ. of Pittsburgh, Pittsburgh, PA

    Lee, J.
    Assistant Manager, POSCO, Pohang,

    Ahn, Y. S.
    Senior Researcher, POSCO, Gwangyang-si,

    DeArdo, A. J.
    Finland Distinguished Professor, Oulu Univ.Univ. of Pittsburgh, OuluPittsburgh, PA

    Pages: 16    Published: Jan 2010


    Abstract

    A new modified Jominy holder and specimen were developed to study the effect of chemical composition, intercritical annealing temperature, and cooling rates on the transformation behavior of a series of dual-phase sheet steels. Correlations between temperature, time, and the distance from the water quenched end were developed using a laboratory view data acquisition program. In addition, the hardness and microstructure along the length of the sheet steel sample were determined as a function of cooling rate from the intercritical annealing temperature. Special chemical regents were used to reveal new ferrite, bainite, and other microstructural components, which were also evaluated by optical, scanning, and transmission electron microscopy. Critical cooling rate equations, based on steel composition, volume fraction of austenite and intercritical annealing temperatures, were developed to avoid or minimize the formation of new ferrite and bainite. The results of this work show that the modified Jominy test is an effective and efficient way to evaluate the hardenability of sheet steels.

    Keywords:

    austenite, bainite, critical cooling rate and equation, dual-phase steel, hardenability, martensite, modified Jominy holder and specimen, new ferrite


    Paper ID: STP49187S

    Committee/Subcommittee: D02.11

    DOI: 10.1520/STP49187S


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