Influence of Severe Accumulative Rolling in a Low Carbon Microalloyed Steel

Abstract:

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Effect of the severe deformation by multi-pass rolling on microstructure and tensile properties was analyzed in terms of rolling temperature, plate thickness, and cooling rate for a modified API X65 steel containing B. The plates, 80 and 50 mm thickness, were rolled six times by 20%/pass (total 75%) to 20 and 12 mm, at 1023 K of unrecrystallized γ region or 973 K of intercritical (α+γ) region, and then quenched in water or oil. All specimens except one oil-quenched condition showed relatively high UTS 700-830 MPa and the continuous yielding(YR~0.6), typical mode of the (ferrite + martensite (bainite)) dual phase microstructure. In contrast, one oil-quenched specimen with the 973 K-20 mm condition, exhibited the discontinuous yielding (YR~0.8), indicating that the microstructure basically consists of ferrite plus pearlite, as well as a relatively low UTS 660 MPa. The degree of deformation really occurring within materials, i.e., strain hardening seems to be enhanced with a decrease in deformation temperature. As the degree of deformation increases, the remaining austenite, not dynamically transformed to fine ferrite, becomes increasingly unstable. A lower hardenability of this remaining austenite thus would lead to a higher possibility to transform into the (ferrite + pearlite) structure of lower strength rather than the (ferrite + martensite (bainite)) of higher strength.

Info:

Periodical:

Materials Science Forum (Volumes 500-501)

Edited by:

J.M. Rodriguez-Ibabe, I. Gutiérrez, B. López and A. Iza-Mendia

Pages:

581-588

DOI:

10.4028/www.scientific.net/MSF.500-501.581

Citation:

H. S. Sim et al., "Influence of Severe Accumulative Rolling in a Low Carbon Microalloyed Steel", Materials Science Forum, Vols. 500-501, pp. 581-588, 2005

Online since:

November 2005

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Price:

$35.00

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