Modeling the formation of longitudinal facial cracks during continuous casting of hypoperitectic steel
Modeling the formation of longitudinal facial cracks during continuous casting of hypoperitectic steel
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DOI：
10.1007/s11663-002-0053-y
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发表时间：
2002-06
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影响因子：
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通讯作者：
J. Konishi;M. Militzer;I. Samarasekera;J. K. Brimacombe
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文献类型：
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作者：
J. Konishi;M. Militzer;I. Samarasekera;J. K. Brimacombe
采用过程模拟方法研究了包钢连铸过程中纵向面裂纹的形成机理。首先，假设碳扩散控制，对δ-到-γ变换进行建模。采用一维有限差分法解决了移动边界（delta/gamma界面）的问题。其次，建立了钢的连铸传热模型，并与相变模型相结合。三种热通量条件（即，低、中和高），并假定为热边界条件。δ-到-γ转化率作为热通量条件的函数进行评价。最后，采用耦合模型的计算结果，应用商业有限元程序，ABAQUS的实体壳的应力计算。结果表明，由于碳在该温度范围内的高扩散率，从δ到γ的转变相对较快。弯月面处热流密度的变化导致弯月面区域相变速率发生较大变化。根据应力计算的结果，可以得出结论，为了在固体壳体表面上产生纵向裂纹，不仅由快速转变引起的拉应力（即，快速冷却），但也需要存在热点。获得了约16%的阈值为所需的壳生长产生纵向裂纹的阻滞。
The mechanism of formation of longitudinal facial cracks during continuous casting of peritectic steels has been studied using a process modeling approach. First, the delta-to-gamma transformation was modeled, assuming carbon diffusion control. The problem of the moving boundary (delta/gamma interface) was solved by employing a one-dimensional finite-difference method. Second, a heat-transfer model for continuous casting of steel was developed and combined with the phase transformation model. Three heat-flux conditions (i.e., low, medium, and high) were obtained from literature data and assumed as the thermal boundary condition. The delta-to-gamma transformation rate was evaluated as a function of the heat-flux conditions. Finally, the results of the coupled model were adopted to calculate the stresses in the solid shell applying the commercial finite-element program, ABAQUS. The results showed that the transformation from delta to gamma is comparatively rapid due to the high diffusivity of carbon in this temperature range. The variation of the heat flux at the meniscus results in large changes of the transformation rate in the meniscus region. Based on the results of the stress calculations, it was concluded that, in order to generate a longitudinal crack on the solid shell surface, not only the tensile stress caused by rapid transformation (i.e., rapid cooling) but also the presence of hot spots is required. A threshold value of approximately 16 pct was obtained for the retardation of shell growth required to generate longitudinal cracks.