通过热膨胀实验测得了含铌低碳钢在不同连续冷却条件下的先共析铁素体相变温度（Ar3)，建立了一种基于铁素体形核和长大模型的新模型，模型中考虑了铌的溶质拖曳作用，用来预测含铌低碳钢的Ar3。研究结果表明，先共析铁素体相变形核长大的临界碳浓度随着温度、奥氏体晶粒尺寸和冷却速率的变化几乎不变，随着钢中铌含量的增加而呈线性增大；在连续冷却过程中钢中铌含量的增加会降低先共析铁素体形核温度，当铌含量大于0.023％之后形核温度并不会继续降低；固溶铌会抑制铁素体相变的发生；本模型适合于含铌低于0.04％的低碳钢，使用该模型预测的Ar3与实测的Ar3吻合。
Proeutectoid ferrite transformation start temperatures (Ar3) with variant continuous cooling rates were measured by dilatometer experiments. A new model, based on ferrite nucleation and growth model, on account of solute drag-like effect of Nb, used to predict Ar3 of Nb-containing low carbon steels, was proposed. It is shown that a limiting carbon concentration in the vicinity of the growing ferrite nuclei is invariable with the variation of temperature, austenite grain size and cooling rate etc, while increases linearly with the Nb content of low carbon steel increasing. Nb content in steels increasing, during the continuous cooling process, results in nuclei temperature of proeutectoid ferrite decreased, while not continue to be decreased when Nb content is more than 0.023 wt pct. Nb solutionized in austenite inhabits the proeutectoid ferrite transformation start. This model is used to predict Ar3 of low carbon steels with Nb content lower than 0.04 wt pct, and the calculated Ar3 is in good agreement with the measured value.
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