【作者】 彭辉；

【导师】 姜周华； 刘福斌；

【作者基本信息】 东北大学 ， 冶金工程， 2017， 硕士

【摘要】 LF钢包精炼技术是一种重要的二次精炼方法,可以提高钢液纯净度、调整钢液成分和温度、优化转炉与连铸之间工艺,具有操作简单、功能强大、投资少等优点,受到了国内外广泛关注。钢包精炼过程通常利用电弧进行温度补偿,相比三相交流钢包炉,直流钢包精炼炉(DCLF)能显著降低电极和耐火材料消耗、提高电弧稳定性、强化冶金效果,近年来越来越受到关注。但是目前人们对直流吹氩钢包精炼过程传输现象缺乏深入的了解。本课题以某厂3t底阳极侧导电直流LF钢包精炼炉为依托,以计算流体力学、电磁流体力学、传热学为基础,利用数值模拟手段,探究不同工艺参数下直流钢包内流场、电磁场以及温度场的分布情况,分析钢液搅拌效果和温度变化规律,为直流钢包炉的操作工艺优化提供依据。本文首先以单孔偏心底吹氩气条件下熔池为研究对象,建立三维湍流模型,考察气泡浮力驱动下不同吹氩位置及不同吹氩流量对搅拌效果的影响规律,根据计算结果得到较佳的操作工艺。其次对直流电流在熔池中形成的电场、磁场、电磁力及电磁力产生的流场进行分析。结果表明:熔池中电流密度、磁通量和洛伦兹力主要集中在上部电极附近。直流电流在熔池中产生的电磁力对钢液具有较强搅拌效果,使得熔池形成沿中心向下,四周壁面向上的循环涡流,电极下方熔池速度最大。在上述研究基础上,综合考虑气泡浮力和电磁力对熔池的搅拌作用,对氩气作用下流场和电磁力作用下流场进行耦合求解,探究综合作用下钢液流场分布。结果表明:相比单独吹氩搅拌或单独直流电磁搅拌,熔池内部流动有较大的变化,在壁面、喷嘴、石墨电极之间形成多个循环涡流,熔池内流动弱流区相对比例减少,有利于强化精炼效果。最后,对实际钢包加热和软吹状态下钢水温度场进行非稳态求解,模拟10 min内钢水温度变化及温度分布规律。结果表明:通电加热时由于直流电弧的加热,电极下方钢水温度最高,同时存在较大温度梯度,高温钢水在电磁及吹氩搅拌作用下向低温区流动,加快了钢水的热交换,加热10 min后钢水升温速率为2.2 K·min-1,与现场测量数据较符合;钢包软吹时,内部温度分布较均匀,温差很小。更多还原

【Abstract】 As an important secondary refining method,LF refining technology can improve the purity of molten steel,adjust the composition and temperature,optimize the process between converter and continuous casting,it has been widely used all over the world with the advantages of simple operation,powerful functions and less investment,etc.The ladle furnace usually use the arc for temperature compensation,compared with three-phase alternating current,direct current ladle furnace(DCLF)can reduce the consumption of electrode and refractory material greatly,improving arc stability,strengthening the metallurgical effect,so more and more people pay attention to it in recent years.However,the underlying physical mechanism of current-coupled argon-blowing process in DCLF was not understood until now.Based on the 3t ladle furnace,the flow field,the electromagnetic field,temperature field in different conditions was numerically simulates with the help of the computational fluid dynamics,electromagnetism,thermodynamics,and the complete mixing time of the molten steel was calculated.The simulated results presented a theory support for the optimal design and controlling.A numerical study was performed at first for the three-dimensional turbulent fluid and mixing characteristics in gas-stirred ladles with off-center single injection.The effect of gas flow rate,positions of nozzle on the flow pattern and mixing were investigated.According to the calculated results,the optimum operation process is obtained.The electric field,magnetic field,the Lorentz force and the flow field in the molten steel formed by the DC current were analyzed later.The results show that the current density,Lorentz force and magnetic flux in the molten pool were mainly concentrated in the upper electrode.The electromagnetic field had strong stirring effect on the molten steel,and created a circulating vortex which flow down in the center and upward in the wall,the maximum speed appeared in the below of the electrode.Moreover,the numerical simulation coupled the flow field and the electromagnetic field.The results show that the flows changed significantly,three circulating vortices are formed between the wall,the nozzle,and the electrode.compared to bottom blowing or DC electromagnetic stirring,the average turbulent kinetic energy increased,the weak flow region and mixing time reduced,which means the stirring and refining were strengthened.At last,the temperature field of the molten steel under heating and soft blowing conditions is simulated.The results show that there is a large temperature gradient under the electrode when the ladle is heated,the high-temperature molten steel flow to the low-temperature zone due to the electromagnetic and argon blowing and the heat exchange become faster.The heating rate of molten steel is 2.2 K·min-1,which is correspond to the experimental data.The temperature distribution of molten steel during soft blowing is more uniform and the temperature difference is very small.更多还原