12流小方坯中间包示踪剂传输及异钢种混浇结果分析

Analysis on tracer transport process and casting of different steel grades in a 12-strand billet tundish

针对中间包异钢种混浇现象,以某厂12流中间包为研究对象,采用数值模拟方法,以中间包稳态流场为基础,通过脉冲和持续加入示踪剂的方式,模拟中间包流场演变和异钢种混浇过程。采用流出百分比的分析方法,计算各流示踪剂开始流出中间包的时间和流出量;并以新旧钢水浓度差值比例达到20%~80%作为钢种转换的标准。经计算,在脉冲加入和持续加入示踪剂时,边部水口5、6浓度开始变化时间远长于水口1-4,差异显著。1-6流的过渡坯长度分别为52.127 m、68.040 m、66.411 m、72.011 m、87.174 m、88.702 m。水口1-6浓度达到80%时(即达到新钢种成分要求),共累计浇注钢水质量分别为104.152 t、134.244 t、133.925 t、147.715 t、200.698 t、247.135 t,边部5-6两流需要大于一包钢水重量(150 t)才能达到新钢种要求。12流中间包在混浇时各流存在较大差异,在生产时应针对各流采取不同过渡坯判别标准。

In response to the phenomenon of grade transition casting in the tundish,the 12-strand tundish of a certain factory is selected as the research subject.Numerical simulation methods are employed,and based on the steady-state flow field of the tundish,the evolution of the tundish flow field and the grade transition casting process are simulated by pulsing and continuously adding tracers.The time that tracer starting to flow out of tundish and flow out percentge of each outlet were calculated by using the analysis method of outflow percentage.The standard of steel grade transition was based on the proportion of difference between the new and old heat of molten steel concentration reaches 20%-80%.It was calculated that when the tracer was pulsed or continuously added,the starting change time of the concentration of far away strand 5 and 6 was much longer than that of strand 1 to 4,and the difference was significant.The length of transition billet for strand 1 to 6 is 52.127 m,68.040 m,66.411 m,72.011 m,87.174 m and 88.702 m,respectively.When the concentration of strand 1-6 reaches 80%(to meet the composition requirements of new steel grades),the total accumulated weight of molten steel is 104.152 t,134.244 t,133.925 t,147.715 t,200.698 t and 247.135 t,respectively.The far away strand 5 and 6 requires more than the weight of a ladle of molten steel(150 t)to meet the requirements of the new steel grade.There are great differences between the different strands of the 12-strand tundish during grade transition casting,so different criteria of transition billet should be adopted in production.