【作者】 韩春鹏；

【导师】 张捷宇；

【作者基本信息】 内蒙古科技大学 ， 钢铁冶金， 2008， 硕士

【摘要】 深入了解和控制结晶器内钢液的流动行为是保证高效连铸工艺顺行和提高铸坯质量的关键。因此,人们十分重视钢液在结晶器内流动特征的研究,最普遍的方法就是物理模拟和数值模拟。针对某钢厂板坯连铸结晶器,本文采用物理模拟和数值模拟的方法,研究了不同浸入式水口及连铸参数对结晶器内钢液流动行为的影响。本文运用商业软件FLUENT,依据计算流体动力学理论建立了三维数学模型,计算了不同工艺参数条件下结晶器内的流场和温度场,研究了浸入式水口的浸入深度、浸入式水口的侧孔倾角和拉速对结晶器内钢液的流场和温度场的影响,讨论了不同参数对结晶器内夹杂物去除情况的影响。结晶器物理模拟的主要方法是水力学模拟,本文利用相似原理建立1:1的水模型,采用浪高仪测量结晶器自由液面的波动情况,分析了不同工艺参数对结晶器自由液面波动的影响;采用“刺激——响应”实验技术,测量自由液面不同位置处的电导率值随时间变化的数据,计算出钢液在自由液面不同位置处的平均停留时间,通过加入染色示踪剂观察结晶器内的流场和冲击点的位置,分析了各因素对结晶器流场的影响。通过对结晶器进行物理模拟和数值模拟研究结果表明:随着拉速的增大,结晶器液面波动增大,流股对窄面的冲击强度增大,结晶器自由液面的温度升高,这有利于保护渣的熔化,但也容易使结晶器出口处的坯壳厚度变薄,不利于坯壳的凝固;随着浸入式水口浸入深度和水口侧孔倾角增大,液面波动减小,但上回流区的高温面积减小,容易产生表面质量问题。拉速对结晶器内夹杂物的去除率影响较大,在拉速小于1.6m/min,夹杂物颗粒直径大于350μm时,夹杂物的去除效果较好;对于直径小于100μm的夹杂物颗粒,去除率都小于20%,说明直径较小的夹杂物颗粒在结晶器中很难被去除;当夹杂物颗粒直径大于400μm时,各种情况的去除率都可以达到80%以上,说明结晶器对颗粒直径较大的夹杂物去除效果较好。板坯为1250×230mm~2,建议采用的最优工艺参数为:浸入式水口的倾角为向下15°,拉速为1.6-1.8m/min,浸入式水口的浸入深度为180~250mm,吹气量为10-20L/min。更多还原

【Abstract】 It is necessary to know and control the flow pattern of the molten steel in the mould, which is the key point to guarantee higher and more efficiency continuous casting technology and improve the quality of the products. Therefore, the flow pattern of molten steel in the mould was highly valued, the physical simulation and the numerical simulation were the most universal method. In view of the slab continuous casting mould, the flow pattern of molten steel in mould of various SEN parameter was studied by adopting the physical simulation and the numerical simulation.Utilizing the commercial software Fluent, the three dimensional mathematical model were set up according to the theory of computational fluid dynamics. The flow field and the temperature field in the mould under the conditions of different technological parameter were calculated. With the influence of immersion depth, angle of the nozzle port, the casting speed, the effect on the flow field and temperature field of the molten steel in the mould were studied. The influence on the inclusion elimination under different parameter was also discussed.The main method of physical simulation was the hydraulics simulation.1:1 scale model was established according to the similarity theory. The level fluctuation in the mould was measured by the wave probe. The influence of different technological parameters on the level fluctuation was analyzed. Using the experimental technology that was“stimulate-response”, the electrical conductivity on the different position of the free surface along with the time’s variation was surveyed, and the average residence time on the different position of the free surface was calculated. The flow field and the impact position in the mould were observed through adding the dyeing tracer material, and the influence of various factors on the flow field was analyzed.From the present physical and numerical simulation research, the following conclusions can be drawn: While the casting speed increasing, the level fluctuation and the jet impingement strength to the narrow wall increase, the temperature at the free surface also increases. These are benefit for the melting slag, but these are bad for the solidification of slab at narrow wall of the mould. While the submerged depth of the SEN and the outlet angle of the SEN increase, this can improve the level fluctuation and reduce slag entrapment, but this will also form the lower temperature distribution at the upper recirculation in the mould, leading to surface quality problems. The inclusion elimination rate in the mould was more influenced by the casting speed. When the casting speed was less than 1.6m/min and the inclusion diameter was larger than 350μm, the inclusion elimination effect is good. When the inclusion diameter was smaller than 100μm, the elimination rate was lower than 20% under different casting parameters. It is proved that the smaller the diameter inclusion is the more difficult to remove in the mould. When the inclusion diameter was larger than 400μm, the elimination rate may achieve above 80% under different casting parameters. These explain that mould was good to eliminate the inclusion with larger diameter. For the 1250×230mm~2 slab caster, the chosen optimal technological parameters are: the downward 15 deg port angel of the SEN,1.6-1.8m/min of the casting speed, 180-250mm of the submerged depth of the SEN and 10-20L/min of flow rate blowing.更多还原