Abstract：Low carbon Si-Mn steel was processed through the processes of intercritical annealing, quenching(I&Q), or the intercritical annealing, subsequent austenitizing, then quenching partition(I&Q&P) and the austenitizing, quenching partition(Q&P). The C, Mn partitioning behavior and their comprehensive effect on retained austenite were studied by means of electron microprobe analysis(EMPA), field emission scanning electron microscopy(SEM) and X-ray diffraction(XRD). The results show that the microstructure of low carbon Si-Mn steel is composed of martensite, ferrite and some retained austenite after treated by I&Q process. C, Mn in martensite of low carbon Si-Mn steel is enriched, and C enrichment level is higher than Mn level. After treated by I&Q&P process, C, Mn of steel exhibits nonuniform distribution in lath martensite, and the local enrichment of C is more obvious. The martensite can be divided into three forms of "high C high Mn", "high C low Mn" and "low C low Mn" according to the different C and Mn contents. The content of retained austenite of the steel treated by I&Q&P process is higher under the comprehensive effect of C, Mn partitioning than that of Q&P process which is stabilized only by C partitioning.
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