气幕挡墙中间包数理模拟及实践

根据武汉钢铁股份有限公司炼钢总厂三分厂二流板坯连铸中间包的操作工艺参数,采用数学与物理相结合的模拟方法,对比研究了气幕挡墙技术对中间包内钢液流动特性及夹杂物去除的影响,并根据研究结果进行了工业试验.研究结果表明:采用气幕挡墙技术,可有效地改善钢液的流动状态,延长钢液的平均停留时间,降低死区体积,提高夹杂物去除率,适应超纯净钢中间包冶金的需求.     

气幕挡墙中间包仿真优化及其冶金效果

根据水钢炼钢厂150 mm×150 mm六流连铸32 t中间包的结构操作工艺参数,采用数模仿真法研究了气幕挡墙技术对中间包内钢液流动特性及夹杂物去除的影响,并对HPB235和65钢进行了工业试验。结果表明,气幕挡墙可以有效改善钢液的流动状态,均衡各出口停留时间,有效延长钢液的平均停留时间,降低死区体积,提高夹杂物去除率。该技术适应多流中间包纯净钢冶炼的需求。     

三流中间包内控流装置优化

通过1∶2模型实验和数值模拟,研究了设置弧形挡墙中间包内钢液流动的特性。水模实验结果表明:弧形挡墙中间包各流平均停留时间比原型中间包提高了一倍,弧形挡墙中间包各流之间平均停留时间最大差异比原型中间包降低了5s。数值模拟结果表明:相对于原型中间包,弧形挡墙的中间包内的钢液流经路径较复杂、停留时间更长,夹杂物有足够时间碰撞聚合去除。水模实验与数值模拟研究结果一致。     

气幕挡墙中间包夹杂物去除的水模型研究

以连铸1500mm×250mm板坯的中间包为原型,几何相似比1/3,采用自制多孔透气砖进行中间包底吹气的水模型试验。结果表明,气幕挡墙中间包中,夹杂物通过斯托克斯机理上浮,气泡吸附和钢液上扬流动而上浮去除;当吹气量≥0.08m~3/h,距入口中心533～800mm处形成有效的气幕挡墙,显著改善钢液流动性,夹杂物去除率由不吹气的44.86%增加至72.86%,并改善小颗粒夹杂物的去除。工业试验表明,采用气幕挡墙,使T[O]降低12%以上。     

不同位置气幕挡墙方案对两流连铸中间包内流场的影响

在相似理论的基础上,通过水力学模拟对两流板坯连铸中间包3种不同气幕挡墙形式下的包内流场进行研究。实验结果表明：在同一吹气量（28L/h）时,气幕挡墙置于中间包端部（方案一）,在气幕的两侧形成两个方向相反的回流区域,延长了钢液的平均停留时间,采用该方案时中间包内死区比例为18.5%;气幕挡墙置于中间包墙坝之间（方案二）,也形成了两个较大的回流区,增加了钢液间的混合和夹杂物的去除,中间包内死区最小为17.4%,为三种方案之最优;气幕挡墙置于中间包挡墙之前（方案三）,气幕挡墙并未形成有效的气幕,中间包内部流体未得到充分混匀,出现27.5%的较大的死区。     

板坯连铸中间包气幕挡墙夹杂物去除的研究

分析了中间包不加气幕挡墙和加气幕挡墙吹氩时夹杂物上浮速度与气泡直径、夹杂物直径和密度的关系。气泡尺寸对夹杂物的上浮速度影响比较明显,夹杂物的密度对上浮速度的影响不大。进行了中间包气幕挡墙的工业试验,试验表明:中间包底吹气对钢液中小夹杂物的去除作用不明显,而对大型的夹杂物去除效果显著。     

中间包气幕挡墙水模与工业试验研究

通过水模型实验和工业试验,研究了中间包底吹氩气对中间包流场和去除铸坯大型夹杂物行为的影响。水模型实验结果表明:中间包底吹气可以改善中间包流场,减少死区体积比,增加平均停留时间。不同实验参数对中间包流体流动特征值的改变程度不同。工业试验结果表明:中间包采用气幕挡墙后,中间包长水口处到铸坯的全氧质量分数降幅提高60.62%;每10kg试样夹杂物总含量由3.85mg降至2.88mg,去除大型夹杂物效果明显,尤其是尺寸小于140μm的夹杂物。     

中间包气幕挡墙去除夹杂物的数值模拟

气幕挡墙技术是改善钢液洁净度的重要方法,吹入的气泡不仅可以改善中间包流场,还可以黏附去除夹杂物,大大提高夹杂物的去除率。采用Euler-Lagrange-Lagrange方法来研究钢液、气泡和夹杂物三相交互作用行为,该模型考虑了钢液与气泡、钢液与夹杂物、气泡与夹杂物之间的相互作用。在正常连铸条件下,研究了气泡黏附与吹气量对不同粒径夹杂物去除的影响。模拟结果表明,考虑气泡黏附的夹杂物去除率比不考虑黏附去除提高了19.12%～28.94%,气泡黏附夹杂物是去除夹杂物的重要方式之一,在气幕挡墙的研究中不可忽略。在本研究的吹气范围内,夹杂物的上浮去除率和黏附去除率都随着吹气量的增加而增大。与传统的挡墙挡坝中间包相比,使用气幕挡墙取代传统挡坝更有利于夹杂物的去除。     

气幕挡墙对430铁素体不锈钢中间包流场和钢水纯净度的影响

在430铁素体不锈钢中间包中使用气幕挡墙,利用模拟软件对中间包钢液流动特性进行数值模拟,对比使用气幕挡墙后钢水全氧含量和板坯夹杂物的变化。结果表明,采用气幕挡墙后,改变了钢液的流动方向,有效延长了停留时间,减少了死区;未使用气幕挡墙的430中包全氧含量为43.7ppm,使用气幕挡墙的430中包全氧含量为36.2ppm,降低了7.5ppm;使用气幕挡墙后,板坯中夹杂物数量明显减少,不存在大于30μm的夹杂物。     

六流小方坯中间包气幕挡墙的数学模拟

根据6流200 mm×200 mm方坯30 t中间包的结构操作工艺参数,采用欧拉两流体模型、多孔介质模型、欧拉-拉格朗日随机轨道模型及Monte-Carlo法,并引入气泡吸附模型,用数学模拟法对比研究了采用气幕挡墙技术对6流中间包内钢液流动特性及夹杂物去除的影响。结果表明,采用气幕挡墙技术优化后,可以有效改善钢液的流动状态,均衡各出口停留时间,有效延长钢液的平均停留时间,降低死区体积,提高夹杂物去除率,适应多流中间包超纯净钢冶炼的需求。     

Water Modelling Experiments of Argon Bubbling Curtain in a Slab Continuous Casting Tundish

Fluid flow characteristics in a two‐strand slab tundish with Ar bubbling curtain were studied in water modelling experiments. It was found that the Ar bubbling curtain can greatly improve the flow characteristics in the tundish with a weir, a dam and a turbulence inhibitor. It dramatically increased the peak concentration time and plug volume and greatly decreased the dead volume, but hardly influenced the minimum residence time. Therefore, the fluid flow characteristics in a tundish with Ar bubbling curtain were favourable to the flotation and separation of inclusions from molten steel. The flow characteristics with low gas flow rate and short distance of the Ar bubbling curtain from the tundish outlet were better than those with high gas flow rate and large distance of the curtain from the outlet.     

Study on Process Technology of Gas Bubbling Curtain Substituting Dam in the Tundish of Slab Casting

This paper presents experimental results from physical and mathematical simulation of liquid steel flow in the tundish adopting gas bubbling curtain substituting dam and industrial trials have been investigated based the experimental results. Physical and mathematical simulation results show the gas bubbling curtain can improve pattern of liquid flow in the tundish , accelerate inclusions flotation,and simultaneity metallurgy effect has been further improved when combining weir and turbulence inhibitor. The industrial trial results confirm that content of oxygen , nitrogen and inclusions in continuous casting billets have been reduced when gas bubbling curtain combining weir and turbulence inhibitor.     

气幕挡墙中间包钢水流动的数值模拟

根据二流连铸1500mm×250mm板坯时中间包的操作工艺参数,采用欧拉两流体模型,多孔介 质模型和拉格朗日随机轨道模型,模拟计算了采用湍流控制器和气幕挡墙技术的中间包内钢液流动特性和 夹杂物的运动轨迹,并用Monte-Carlo法统计了夹杂物的总去除率。模拟结果表明,采用中间包气幕挡墙技术 可以有效改善钢液的流动特性,延长钢液停留时间,减小死区体积;当吹气量为0.90m³/h时,夹杂物去除率比 不吹气工艺增加15.6%     

Fluid flow behaviour in slab continuous casting tundish with different configurations of gas bubbling curtain

Abstract

Fluid flow characteristics in a two strand slab continuous casting tundish with different configurations of argon gas bubbling curtain (GBC) were investigated in physical modelling experiments. It was found from this research that the GBC with a small flow rate acted as a gas dam and could greatly improve the flow characteristics in the tundish. It increased dramatically the peak concentration time and plug flow volume, decreased greatly the dead volume, created surface directed flow and eliminated short circuiting. Therefore, the fluid flow characteristics in a tundish with GBC were favourable to the floatation and separation of inclusions from molten steel. The flow characteristics with low gas flow rate and short distance of the bubbling curtain from the tundish outlet were better than those with high gas flow rate and large distance of the curtain to the outlet. The optimal configuration for the improvement in fluid flow characteristics was turbulence inhibitor (TI)–weir–dam–GBC (TI–W–D–GBC), followed by TI–channel weir (CW)–GBC, TI–W–GBC and TI–GBC.     

中间包内钢水控流技术

介绍了中间包冶金技术的发展,分析了中间包内钢水的流动特性及控流装置对钢水流动状态的影响,论述了改进中间包内的控流装置可以明显改变钢水流动状态,中间包内同时应用堰、坝、湍流控制器及多孔挡墙或气幕挡墙,能够延长钢水在中间包内的滞留时间,有效去除钢中夹杂,提高中间包冶金效果。     

Hydraulics and Mathematics Simulation on the Weir and Gas Curtain in Tundish of Ultrathick Slab Continuous Casting

The molten steel flow pattern in continuous casting tundish could be improved if the flow control devices were properly used. With reasonable application of weir and air curtain, the disturbance at injection zone of the tundish was reduced. The flow path of the molten steel was changed, and the short-circuit flow was eliminated. Therefore, the residence time was lengthened. An air curtain with bubbles floating could promote the surface flow and improve inclusions removal. The application of weir and air curtain in an ultrathick slab continuous casting tundish was investigated with hydraulics and mathematics simulation. The residence time and dead volume fraction were studied through orthogonal experiments with different positions of the flow control devices. The efficiency of three factors was analyzed, and the optimum positions of the weir and air curtain were obtained. Besides, the discrete phase model was suitable for simulation of the interaction between gas bubbles and molten steel, and the mathematics results shown the optimum one got larger inclusion flotation rate.     

气幕挡墙对中间包内钢液流场影响的数值模拟

根据实际中间包的操作工艺参数,采用欧拉-欧拉两流体模型,用数值模拟法模拟计算了中间包底吹对钢液流动的影响.结果表明,底吹改变了中间包内钢液的流动状态,在气幕挡墙的两侧分别形成了方向相反的回流区.底吹气体流量对钢液流动状态、气泡分布影响显著,底吹气体流量太大或太小都不利于改善钢液的流动状态.     

连铸中间包气幕挡墙水模拟实验研究

通过水模拟实验,研究了气幕挡墙位置、气体流量及采用双透气砖对中间包流场的影响;认为采用气幕挡墙可有效延长钢水在中包的平均停留时间,降低死区,混匀钢水;并提出工业性试验的可行性建议。     

中间包底吹氩水模型试验及冶金效果

通过水模型试验和工业试验,研究了中间包底吹氩参数对中间包流场的影响。水模型试验结果表明:中间包底吹气可以改善中间包流场,较佳的吹气参数是透气砖距离冲击区765 mm,吹气量在0.06~0.10 m3/h。工业试验结果表明:中间包采用底吹氩后,T[O]降低了26.67%;大型夹杂物总含量由0.430 mg/kg降至0.079 mg/kg,降低了81.82%。