连铸坯凝固过程平面枝晶微观偏析模拟研究

Simulation of platelike dendritic microsegregation during solidification process of continuous casting slab

为解决连铸钢坯偏析问题,基于菲克第二定律和质量守恒定律,建立了一维平面枝晶生长凝固偏析数值模型。应用有限容积法离散传质方程,离散后的方程用VB编程求解,研究X70管线钢凝固过程中在二次枝晶间距范围内的C,Si,Mn,S,P各元素质量分数分布随凝固进程和冷却速率的变化规律。结果表明:固相率的变化对合金元素在二次枝晶间偏析影响较大,冷却速率对其影响较小;随着固相率的增加,各合金元素的固相成分增加较少,液相成分质量分数快速增加;S和P元素在固相中的分布较均匀,S凝固终了的偏析指数最高,C偏析指数最小。在实际生产中应适当控制S和P元素的含量。

In order to solve the microsegregation problem of continuous casting slab, one-dimensional platelike dendritic model is established based on Fick second law and mass conservation law. Mass transfer equation is discreted by finite volume method, and the discrete equations are solved by VB program. The element C, Si, Mn, S, P of X70 pipeline steel concentration distribution changing with solid fraction and cooling rate changing are calculated individually with the established numerical model in the range of secondary dendrite distance. The main conclusions are as follows： the solidification fraction has more influence on alloying element microsegregation, cooling rate has minor influences. With the solidification fraction increasing, all alloying element concentrations in solid-phase have less changes, hut all alloy element concentrations in liquid-phase increase quickly. The element of S and P have more uniform distribution in solid-phase, however, in the final solidification, there are more S microsegregation and less C microsegregation, therefore, the amount of S, P should be controlled in practical production.