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基于体积平均的两相数学模型,耦合求解温度场、流场和浓度场,模拟计算过热度对12Cr2Mo1R大扁锭凝固过程碳元素宏观偏析的影响。本模型将钢液密度设为依赖于温度和溶质浓度的函数。因而,可以综合考虑温度梯度、浓度梯度以及体积收缩等因素对钢液流动的作用,能够更加精确地预测凝固过程溶质元素分布。本次实验研究了过热度对凝固前沿温度梯度、凝固速率和钢液流动速率影响规律,以及最终碳元素宏观偏析情况。模拟结果表明:过热度的增加导致铸件表面区域凝固前沿温度梯度升高,而对中心线区域凝固前沿温度梯度的影响不显著;过热度对铸锭凝固速率的影响很小。此外,过热度的增加使得钢液流动速度相应增加,并使得固液两相区宽度相应的减小。铸锭凝固过程中碳元素宏观中心偏析总体表现为:当过热度<40℃时,增加过热度对加剧铸锭中心偏析不显著;然而,当过热度>40℃时,提高过热度使得铸锭中心偏析急剧恶化。
Based on the two-phase mathematical model of volume average, the temperature field, the flow field and the concentration field are coupled to simulate the influence of superheat on the carbon segregation in 12Cr2Mo1R large-slab solidification process. The model sets the molten steel density as a function of temperature and solute concentration. Therefore, the effects of temperature gradient, concentration gradient and volume shrinkage on the flow of molten steel can be comprehensively considered, and the distribution of solute elements in the solidification process can be more accurately predicted. The experimental study of superheat on the solidification front temperature gradient, solidification rate and flow rate of molten steel, as well as the final carbon macro-segregation situation. The simulation results show that the increase of superheat results in the increase of the temperature gradient ahead of the solidification in the casting surface area, while the influence on the temperature gradient in the front of the solidification zone is insignificant. The superheat has little effect on the solidification rate of the ingot. In addition, the increase of superheat makes the flow rate of molten steel increase correspondingly, and make the width of solid-liquid two-phase zone decrease correspondingly. When the superheat degree is lower than 40 ℃, increasing the degree of superheat is not significant to aggravating the center segregation of the ingot. However, when the superheat degree is higher than 40 ℃, the degree of superheat increases to make ingot Center segregation sharply worsened.