250t钢包底吹氩卷渣和钢液裸露的模拟

Modeling of Slag Entrapment and Molten Steel Exposed to Atmosphere in Refining of 250 t Ladle with Bottom-blown Argon

针对某钢厂250 t钢包底吹氩气过程进行水模型实验和数值模拟,考察了吹气量和渣层厚度对卷渣行为和吹气量、渣层厚度及透气砖透气性能对钢液裸露面的影响,分析了卷渣形成机理.结果表明,吹气量对卷渣形成具有决定性作用,吹气量控制在0.96 m3/h(对应实际流量69 m3/h)以下可避免卷渣;随着吹气量的增加,钢液裸露面积逐渐增大,当吹气量达到0.70 m3/h时,钢液裸露面积百分比约达14%,继续增大吹气量,其增加幅度变缓;随着渣层厚度的增加,临界卷渣吹气量和钢液裸露面积逐渐减小,以37 mm(对应实际渣厚150 mm)厚渣层覆盖,可有效防止钢液二次氧化;透气砖堵塞对钢液裸露面积影响较大,顶部钢液形成两不同大小的裸露亮圈,并加重对包壁耐材的冲刷与侵蚀,降低钢的洁净度.工艺优化后,钢包水口结瘤率降低至0.1%以下,且可降低生产成本.

Experiments in water model and numerical simulation were carried out to study bottom blowing process of argon gas for steel refining in a 250 t ladle in a steel plant. The effects of gas flow rate and slag layer thickness on the slag entrapment, and gas flow rate, slag layer thickness and porous brick permeability on exposed surface area of molten steel were examined. Formation mechanism of slag entrapment was analyzed. The results show that flow rate plays a decisive role on formation of slag entrapment. Slag entrapment can be prevented if the flow rate is controlled below 0.96 m3/h（corresponding to actual flow rate of 69 m3/h）. With the increase of flow rate, the exposed bare area gradually increases, and reaches about 14% at the flow rate of 0.70 m3/h, and its increasing amplitude tends to ease off with the further increase of flow rate. With the increase of slag layer thickness, critical gas flow rate of the slag entrapment and bare area decrease. With 37 mm（corresponding to actual layer thickness of 150 mm） slag layer thickness covering, reoxidation of steel can be prevented effectively. Porous brick clogging has a great impact on the bare area of molten steel, two bare bright circles with different sizes form on the top of molten steel, which increases the erosion from ladle wall refractory and contamination of liquid steel. After process optimization, the ratio of ladle nozzle clogging is reduced to less than 0.1%, and the production cost can be reduced.