基于数值模拟的结晶器卷渣在线预测方法

 结晶器保护渣卷入到钢液中后容易被生长的凝固坯壳捕获,最终在冷轧板上形成由卷渣引起的表面缺陷,会严重恶化钢产品的质量。结晶器液面卷渣现象受到钢液成分、温度、流动方式和吹氩流量的影响。结晶器表面钢液流速大小是反映钢渣界面是否发生卷渣的重要参数,但在实际浇铸过程中,不能在线预测不同拉速、吹氩流量和水口浸入深度下结晶器表面钢液的最大速度。提出一种基于板坯连铸结晶器内多相流动数值模拟的结晶器卷渣在线预测方法。首先,建立结晶器内三维多相流动数学模型,模拟不同拉速、吹氩流量和水口浸入深度下的钢液流动行为;其次,对计算得到的表面钢液流速的最大值进行拟合,得到固定浇铸断面下结晶器表面最大流速的预测公式;最后,通过某钢厂的插钉板工业试验验证了所提方法的准确性。研究发现,不同浇铸参数下表面钢液流速沿结晶器宽度方向呈现先增加再减小的变化趋势,在结晶器宽度1/4位置具有最大值。钢液流速在较小和较大拉速下分别在窄面和水口附近具有较大值;在较小和较大吹氩流量下分别在水口和窄面附近具有较大值;随着水口浸入深度增加,钢液流速在水口和窄面附近变化较小。基于拟合的钢液流速公式,通过比较最大钢液流速与钢渣界面发生卷渣的临界流速,实现了结晶器卷渣的在线预报。

Online prediction method of slag entrainment in mold based on numerical simulation

When the mold flux is entrained in the molten steel, it is easy to be captured by the growing solidified shell. Finally, the surface defects caused by the mold slag entrainment will be formed on the cold rolling sheet,which seriously deteriorate the quality of steel products. The phenomenon of slag entrainment in the mold is effected by the molten steel composition,temperature,flow pattern,and argon flow rate. The velocity of molten steel at the top surface of mold is an important parameter that reflects whether slag entrainment occurs at the steel-slag interface. However,the maximum velocity of molten steel at the top surface under different casting speeds, argon flow rates,and submergence depths of SEN cannot be predicted online in the actual casting process. An online prediction method of slag entrainment in the mold based on the numerical simulation of multiphase flow in the slab continuous casting mold was proposed. First,a 3D mathematical model of the multiphase flow was built and the behavior of molten steel flow with different casting speeds,argon flow rates, and submergence depths of SEN was simulated. Then,the calculated maximum velocity of molten steel at the top surface was fitted and the prediction equation of the maximum velocity under the fixed mold section was obtained. Finally,the accuracy of the method was verified by nail board measurements in a steel plant. The results shown that the speed of molten steel on the top surface had a trend of increasing first and then decreasing along the mold width and had a maximum value at the 1/4 mold width under different casting parameters. The speed had a larger value near the narrow face and the SEN under the smaller and larger casting speed,respectively. It had a larger value near the SEN and the narrow face under the smaller and larger argon flow rate,respectively. With the increasing of submergence depth of SEN,the speed varied small near the SEN and the narrow face. Based on the fitted equation of the molten steel velocity,the online prediction of slag entrainment in the mold was realized through comparing the maximum speed of the molten steel with the critical speed of slag entrainment at the steel-slag interface.