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采用热膨胀仪测试研究了Q450NQR1钢连铸坯5℃·min-1及20℃·min-1冷却速率下的线性热膨胀(ΔL/L0)和热膨胀系数随温度的变化规律.在此基础上,建立了一种基于平均原子体积的相体积计算模型,量化研究了奥氏体相变过程中各相体积分数的变化规律,并在将计算结果与显微组织观察结果对比分析基础上,讨论了连铸冷却速率对铸坯奥氏体相变过程的影响.结果表明:该计算模型可以较为准确地描述铸坯的奥氏体相变过程,适用于多相连续析出相变;随着冷却速率的增大,铸坯热膨胀曲线中对应于铁素体和珠光体析出的两个变化峰向低温区移动,峰值明显增大;冷却速率由5℃·min-1上升至20℃·min-1时,铁素体及珠光体起始析出温度分别降低约32℃和37℃,最终体积分数分别由0.894和0.106变为0.945和0.055.
The thermal expansion coefficient (ΔL / L0) and thermal expansion coefficient with temperature of 5 ℃ · min-1 and 20 ℃ · min-1 cooling rate of Q450NQR1 steel continuous casting billet were investigated by means of thermal dilatometer. On this basis, A phase volume calculation model based on average atomic volume was used to quantitatively study the variation law of the volume fraction of each phase during the austenite transformation. Based on the comparison between the calculation results and the microstructure observation results, Effect of casting cooling rate on austenite transformation during slab casting. The results show that the calculation model can describe the austenite transformation process of slab more accurately, and is suitable for the continuous precipitation of multiphase. With the cooling rate , The two peaks corresponding to the precipitation of ferrite and pearlite in the thermal expansion curve of slab move to the low temperature region and the peak value increases obviously. When the cooling rate rises from 5 ℃ · min-1 to 20 ℃ · min-1 , Ferrite and pearlite initial precipitation temperature decreased by about 32 ℃ and 37 ℃, the final volume fraction from 0.894 and 0.106 to 0.945 and 0.055 respectively.