Tempering of Mn and Mn-Si-V dual-phase steels |
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Authors: | G R Speich A J Schwoeble G P Huffman |
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Affiliation: | (1) U. S. Steel Research Laboratory, 15146 Monroeville, PA |
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Abstract: | Changes in the yield behavior, strength, and ductility of a Mn and a Mn-Si-V d11Al-phase (ferrite-martensite) steel were investigated
after tempering one hour at 200 to 600 °C. The change in yield behavior was complex in both steels with the yield strength
first increasing and then decreasing as the tempering temperature was increased. This complex behavior is attributed to a
combination of factors including carbon segregation to dislocations, a return of discontinuous yielding, and the relief of
resid11Al stresses. In contrast, the tensile strength decreased continuously as the tempering temperature was increased in
a manner that could be predicted from the change in hardness of the martensite phase using a simple composite strengthening
model. The initial tensile ductility (total elongation) of the Mn-Si-V steel was much greater than that of the Mn steel. However,
upon tempering up to 400 °C, the ductility of the Mn-Si-V decreased whereas that of the Mn steel increased. As a result, both
steels had similar ductilities after tempering at 400 °C or higher temperatures. These results are attributed to the larger
amounts of retained austenite in the Mn-Si-V steel (9 pct) compared to the Mn steel (3 pct) and its contribution to tensile
ductility by transforming to martensite during plastic straining. Upon tempering at 400 °C, the retained austenite decomposes
to bainite and its contribution to tensile ductility is eliminated.
This paper is based on a presentation made at the “pcter G. Winchell Symposium on Tempering of Steel” held at the Louisville
Meeting of The Metallurgical Society of AIME, October 12-13, 1981, under the sponsorship of the TMS-AIME Ferrous Metallurgy
and Heat Treatment Committees. |
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