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通过热膨胀法及金相分析法,研究Ti含量为0.015%~0.10%的低碳钢连续冷却条件下组织演变行为,探讨了Ti含量及冷却速率对低碳钢相变行为的影响规律。结果表明,Ti微合金元素具有细化铁素体晶粒尺寸,抑制铁素体相变,促进贝氏体和马氏体相变的作用。当Ti含量由0.015%增加至0.10%时,0.5℃/s下获得的铁素体平均晶粒尺寸可由24.5μm细化至13μm,铁素体相变的冷却速率范围由≤5℃/s缩小至<1℃/s,马氏体临界冷却速率由40℃/s降低至20℃/s。冷却速率及Ti含量共同决定Ti微合金低碳钢的组织演变行为,特别是对扩散型的相变开始温度具有显著的影响。
The microstructure evolution behavior of low carbon steel with Ti content of 0.015% ~ 0.10% was investigated by thermal expansion and metallographic analysis. The influence of Ti content and cooling rate on the transformation behavior of low carbon steel was discussed. The results show that the Ti microalloy has the effect of refining the ferrite grain size, inhibiting the ferrite transformation and promoting the transformation of bainite and martensite. When Ti content increases from 0.015% to 0.10%, the average ferrite grain size obtained at 0.5 ° C / s can be refined from 24.5μm to 13μm and the cooling rate of ferrite transformation decreases from ≦ 5 ℃ / s To <1 ° C / s, the martensite critical cooling rate is reduced from 40 ° C / s to 20 ° C / s. The cooling rate and Ti content jointly determine the microstructure evolution behavior of Ti microalloyed mild steel, especially the diffusion onset temperature.