| The high strength and high ductility characteristics of Q&P steel used in theautomotive body and structural steel, Which have being a new generation of steelmaterials direction. The research department for low-carbon Si-Mn steels, Study theregularity on microstructure and properties during partitioning by traditional Q&P heattreatment process; On this basis, study the diffusion behavior on Mn in the intercritical;Design a new type of Q&P steel heat treatment process by Mn diffusion behavior andtraditional Q&P heat treatment process to obtain the microstructure of martensite andcarbon-rich manganese-rich retained austenite austenite at room temperature, And in-depth study the regularity on microstructure and properties between new process and thetraditional Q&P process. Specific conclusions are as follows:Partition temperature above450℃and the partition time above200s will makemartensite and retained austenite decomposition of the experimental steel0.20C-1.28Mn-0.37Si, The content of retained austenite depended on partition temperatureand partition time, When partitioning temperature at400℃, strong plastic productreaches the maximum22610MPa%.With the annealing time the content of Mn element partitions from ferrite toaustenite is increasing after holding300s~2000s at intercritical720℃of experime-nttal steel, The time are1300s and1500s that the volume fraction of martensitesaturated and chemical potential equilibrium(le, saturation) of ferrite and austenite.The elongation increased by4%and strong plastic product increased by20%byI&Q&P heat processes contrast the traditional Q&P heat treatment process. With theextension of the holding time in the austenitic, the austenitic keep the growing trending.After insulation60s in the austenitic region, the tissue was martensite and C-rich and Mn-rich residual austenite, the strong plastic is the best. And with the prolong of the holdingtime, tensile strength and elongation keep the similar trend with Q&P heat treatment. |
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