Numerical Simulation of Fluid Flow and Heat Transfer in Funnel Shaped Mold of Thin Slab Continuous Caster

Thin slab casting is used widely in the world. The control of molten steel flow and solidification in the mold is difficult due to the high casting speed and complicated configuration of the mold. Numerical simulation was carried out to study the fluid flow and heat transfer in the funnel shaped mold. The influence of nozzle design, casting speed and nozzle submersion depth on the flow and temperature fields in the mold was investigated, and guidance for selecting configurations of submerged nozzle was obtained.

Numerical Simulation of the Electromagnetic Continuous Casting for Clad Slab

In this paper,a new electromagnetic continuous casting process to prepare clad slab is presented.The influence of level direct current electromagnetic field on temperature and flow fields of the melt during the fabrication of clad slab were numerically studied by the engineering software ANSYS and FLUENT.The results indicated that when the magnetic flux density(B)was 0.15 T,the impact velocity and distance of the flow to the narrow face and underside of the dividing plate decreased remarkably.So the flow impact to the liquid pool was reduced.At the same time,the high temperature zone of the melt moved away from the narrow face and the dividing plate,and distributed more uniformly. The wider semi-solid area next to the dividing plate was useful for 3003 and 4004 aluminum alloys to bond.

Numerical Simulation of Electromagnetic Field and Flow Pattern in a Continuous Slab Caster with In-roll Type Strand Electromagnetic Stirring

The electromagnetic field and flow analysis model were developed to simulate the electromagnetic field and the flow pattern in a vertical curved continuous slab caster with the in-roll type strand electromagnetic stirring. The transient electromagnetic field distribution and the induced electromagnetic force were numerically described. The effects of stirring current, stirring frequency, and different stirrer configurations on the electromagnetically driven flow field in the strand were investigated and the optimization of the stirring parameters was discussed by performing a relative comparison of numerical results. Results show that the in-roller type strand electromagnetic stirrer （S- EMS） pair generates the fluctuating magnetic fields, penetrating through the cast slab and periodically parallel shift- ing along the slab wide face w!th time evolution. The transient induced electromagnetic forces travels toward the magnetic flux shifting direction, Different stirring parameters （i. e. current and frequency） and stirrer configurations affect the stirring strength and the flow rbcirculation pattern in the strand, which are closely related to metallurgical performances of the stirrers. There is an optimum frequency to obtain the maximum stirring. The present model pro vides a relatively theoretical insight into the in-roll type strand electromagnetic stirring system for best operating.

Numerical Simulation on Inclusion and Bubble Entrapment in Solidified Shell in Model Experiment and in Mold of Continuous Caster With DC Magnetic Field

A model experiment investigating entrapment of inclusions and bubbles on the solidified shell was performed using molten steel,and the conditions for inclusion and bubble entrapment and mechanism of entrapment were studied. The results were applied to the flow behavior in the casting mold of a continuous caster.At the solid-liquid interface, entrapment of inclusions is greatly reduced by the existence of a low velocity flow,e.g.,0.05m/s.The above-mentioned interfacial flow velocity dependency of inclusion entrapment is considered to be largely influenced by changes in the thickness of the concentration boundary layer,which depend on the interfacial flow velocity.Specifically,bubbles and inclusions which enter the concentration boundary layer are drawn to the solid-liquid interface by a suction force which is several orders larger than the Saffman's force.In addition to the above-mentioned suction force,the so-called cleaning effect is determined by fluid-dynamic forces such as drag force,etc.which act on particles,and furthermore,by resident time of particles at the solid-liquid interface,which depends on the solidification rate.In a FC mold with a 2-stage electromagnetic brake,flotation of bubbles entrained in the jet flow from the nozzle is accelerated with the large DC magnetic field.This is attributed to the braking effect of the DC field on the nozzle jet and the upward flow by the buoyancy of the bubbles.As a result,the interfacial flow velocity can be normalized by increasing the strength of the magnetic field,and entrapment of large bubbles and inclusions can be reduced.

Research on the trajectory of non-metal inclusions with the flow in the mold during the solidification of continuous casting slabs

By means of the numerical simulation method,the mathematical model of inclusions movement in the mold is established under the condition of austenitic and fen-itic stainless steel slab production. According to the simulation results, the main zones for inclusion particles accumulation were found and many factors that affected floating-up probability of inclusion particles were identified. These factors include the inclusion particle size, the casting speed and the slab width, etc. It is believed that the inclusion particle size is the key one among these factors.

Influence of submerged entry nozzle clogging on the behavior of molten steel in continuously cast slab molds

The influence of submerged entry nozzle clogging on the behavior of molten steel in continuously cast slab molds was studied using commercial code CFX4.3. The results indicate that clogging at the top part of the nozzle port not only increases the velocity of molten steel, but also enhances the wall shear stress, F number and heat flux. This clogging has the greatest effect on the behavior of molten steel. However, clogging at the top 1/3 of the nozzle only increases the velocity of molten steel and has little influence. Clogging at the bottom of the nozzle almost has no influence.

EFFECT OF SEN DESIGN ON SURFACE FLUCTUATION AND SOLIDIFYING SHELL IN SLAB MOLD AND ITS OPTIMIZATION

Turbulent flow and heat transfer coupled with solidification in slab continuous casting mold was studied by numerical simulation method. Volume of fluid （VOF） model is used to solve steel-air two-phase flow problem and enthalpy-porosity scheme is introduced to solve the fluid flow problem involving solidification. Contributions of various nozzle port angles and port widths and heights on the free surface fluctuation and the thickness of solidifying shell in slab mold were particularly investigated, based on which the structure of submerged entry nozzle was optimized. Flow inside the common nozzle port cannot fill the entire outlet area, having a recirculation in the upper portion of the port, which is enlarged for the nozzle port with both larger height and width. Results show that the flow in mold cavity is mainly controlled by the nozzle port angle. The increase of the angle of upper face of the port to shape a roughly streamlined inner-wall improves the effective area fraction of the nozzle, resulting in less jet impingement, weaker free surface turbulence and thicker solidifying steel shell.

Anchor-Shaped Design of a Submerged Entry Nozzle for the Continuous Casting of Steel

An anchor-shaped geometrical design for a Submerged Entry Nozzle for the slab continuous casting of steel is presented in this work. To evaluate its performance, transient 3D multiphase numerical simulations were carried out using the Computational Fluid Dynamics technique. The performance of the proposed nozzle is numerically compared with that of a conventional cylindrical nozzle. Computer results show that the chance of formation of Karman’s vortexes and powder entrapment becomes small for the anchor-shaped SEN.

复合磁场作用下板坯结晶器内钢液流动、传热与凝固的数值模拟

为利用板坯连铸过程中电磁搅拌技术和电磁制动技术各自的优点克服自身缺点,本文应用了结合电磁搅拌和电磁制动的分体式复合磁场并提出电磁制动的结构为单条型电磁制动,对板坯连铸结晶器流场和温度场进行控制.建立了该磁场下结晶器内钢液流动、传热、凝固耦合的三维数值模拟模型.对复合磁场给予结晶器内钢液流动及传热与凝固的影响进行了分析.结果表明:施加复合磁场后,结晶器内上、下返流流速明显减小,钢液主流股对窄面的冲击深度变小,上返流整体下移,弯月面钢液形成顺时针循环流;结晶器内整体温度分布更均匀,弯月面处温度较无磁场时基本不变;结晶器出口处凝固坯壳更为均匀,其厚度较无磁场下有所增加,钢液射流对窄面附近初生坯壳冲刷程度减小.

基于ABAQUS的X70管线钢连铸板坯空冷的热力耦合分析

随着管线钢连铸板坯热送热装占比的升高,切割后的连铸板坯在相变、热应力以及温度的耦合作用下易形成质量缺陷,造成巨大的经济损失。以X70管线钢为研究对象,通过综合考虑材料热物性参数随温度的非线性变化及边界条件的设定,利用ABAQUS有限元分析软件对X70管线钢4 500 mm×2 300 mm×300 mm连铸板坯的单坯冷却过程进行热力耦合数值模拟分析。结果表明,铸坯重心平均散热速率为0.076℃/s,表面中心为0.084℃/s,表面与心部温差区间为100~210℃,并随着时间逐步减小。铸坯边部应力值为25 MPa,边部300 mm以内热应力大致相同,在200 MPa以内。结合温度场变化情况应尽量缩短切割到加热炉的时间,或增加保温措施以防止因热应力过大形成质量缺陷。

Structural Optimization of Electromagnetic Swirling Flow in Nozzle of Slab Continuous Casting

During the slab continuous casting process, the flow field of molten steel in the mold plays a decisive role in the quality ofthe slab. In this paper, electromagnetic swirling flow in nozzle technology is proposed to control the flow field in mold.This technology can drive molten steel to rotate inside the submerged entry nozzle by electromagnetic force, therebycontrolling the flow field. This research shows that it can reduce the impact of molten steel on the bottom of nozzle andpartly reduce the negative pressure at the upper part of nozzle outlet which is even eliminated by optimizing the structureand angle of nozzle. The area of heat flux of the mold wall becomes larger, and the crest value of heat flux gets lower thanthat without swirling in nozzle and any nozzle optimization. The meniscus fluctuates smoothly, and the flow velocity at thetop surface is within a reasonable range. The temperature field distribution in the mold is uniform which was beneficial tothe growth of equiaxed crystal and decreased element segregation.

连铸板坯结晶器水口优化及现场应用

新天钢联合特钢有限公司炼钢厂(简称联合特钢)1#机180 mm×550 mm小板坯结晶器卷渣现象,以实际生产条件为背景,研究了不同板坯浸入式水口对结晶器内钢液流场的影响因素。采用Fluent软件建立了三维数学模型进行数值计算,探明了水口结构参数对结晶器内钢液流场分布的影响。结果表明:与原水口相比,优化水口上循环流股区面积更大,且其自由液面附近流体速度合理,钢渣界面波动较为稳定。工业试验方面,优化水口后结晶器液面波动幅度基本控制在±3 mm,异常波动概率大幅度降低。本研究结果可为该厂板坯结晶器水口设计提供理论指导。

475 mm特厚板坯连铸结晶器浸入式水口优化数值模拟研究

特厚板坯连铸技术主要应用于特种装备制造领域,市场需求量较大。浸入式水口的结构是决定结晶器中流场流动行为的关键因素。本研究通过建立三维数值模型,研究浸入式水口侧孔倾角对475 mm特厚板坯结晶器内流场流动行为、温度场和凝固坯壳分布的影响。结果表明,水口侧孔倾角对钢液流动行为影响显著:当侧孔倾角由-20°调整至-10°时,射流冲击深度由660 mm减小至545 mm,结晶器自由液面平均温度升高4 K;此外,侧孔倾角的减小使凝固坯壳尤其是窄面坯壳厚度增加6 mm。综合考虑,当水口侧孔倾角为-10°时,结晶器性能最佳,此时的液面流动较活跃,结晶器保护渣和液面之间的传热性良好,出口处的壳体厚度均匀,足以满足生产需要,可有效避免漏钢现象发生。

攀钢弧形板坯连铸机铸坯凝固层厚度的研究

研究工作运用“射钉法”,准确地标定了攀钢弧形板坯连铸机二冷区凝固坯壳厚度及凝固系数 ,为评价现有二冷系统的冷却能力、制定合理的二冷配水制度和高拉速条件下的工艺参数提供了重要依据。

板坯连铸结晶器内流场的数值模拟

针对某钢厂板坯连铸机结晶器的结构和工艺参数,建立了描述结晶器内钢液流动的三维数学模型,用商用软件FLUENT,运用湍流动能k方程和湍流动能散耗率ε方程的k-ε双方程模型在给定的数值计算条件下,对板坯连铸结晶器内钢液的流场进行了模拟.通过模拟浇注初期钢液的流动状态,分析了结晶器内流场的基本特征.同时模拟计算了浸入式水口的出口倾角、插入深度以及拉速对钢液流动的影响.得出了满足断面要求的合理工艺参数:水口倾角为向下15°,插入深度为200mm,拉坯速度为1.3m/min.

316不锈钢板坯连铸结晶器内坯壳厚度模拟

为研究连铸过程中高温区δ铁素体含量对凝固传热的影响,采用商业有限元软件ANSYS,利用单元生死技术,对316不锈钢板坯的浇注过程进行了模拟。采用2-D模型,分别计算了δ铁素体含量为0、25%、50%、75%及100%时坯壳出口温度、坯壳厚度及表面温度的变化,探讨了坯壳生长及厚度变化规律。结果表明,随着δ铁素体含量升高,坯壳出口温度升高,表面温度变化剧烈,坯壳的出口厚度减薄。

基于连续模型的板坯连铸凝固过程的数值模拟

结合实际测量数据,建立了基于连续模型的板坯连铸过程流场、温度场和凝固的三维耦合数学模型。计算结果表明:该模型可用于描述连铸板坯结晶器和整个二冷喷水区的凝固进程;凝固坯壳的生长限制了流体流动的空间,加快了水口出口钢流的动量衰减;流体流动加快了铸坯内部传热机制由对流向热传导传热的转变进程,控制了两相区的发展。

圆坯连铸结晶器温度场模拟与坯壳厚度预测

基于连铸圆坯结晶器温度与热流实测数据,建立了连铸圆坯凝固的三维传热模型,计算出结晶器和铸坯的温度场,并得到铸坯的固相率与坯壳厚度分布情况.温度计算结果与实测数据符合较好,表明此数学模型能够较为准确地反映实际情况.讨论了拉速、浇注温度等因素对坯壳厚度的影响,并对利用模型计算与经验公式计算得到的坯壳厚度进行了对比.

板坯连铸结晶器中三维凝固壳厚度分布的数值模拟及实验验证

建立了连铸结晶器中三维凝固壳厚度分布的计算模型和计算方法。提出了非耦合计算时流动计算域与凝固传热计算域的衔接问题，以及铸坯表面换热系数确定的方法。针对２５０ｍｍ×１３００ｍｍ板坯连铸的实际工况，用所建立的模型和处理方法数值模拟了其结晶器中的三维温度场和三维凝固壳厚度分布。同时用实测的凝固壳厚度分布数据验证了本文计算中的模型、边界条件和计算方法。本文采用的方法可满足工程精度，并较简便实用。

基于射钉法的小方坯凝固过程数值模拟

结合方坯连铸机二冷各段的实际情况,在二冷各段末对铸坯进行射钉取样,利用硫印法测定方坯二冷区内目标点凝固壳的厚度,建立了方坯传热数学模型,并利用射钉结果修正数学模型中的各段的传热系数,提高数学模型的准确性。将射钉法确定的坯壳厚度与数学模型计算结果相比较,结果表明,利用修正过的数学模型可以模拟整个铸机的传热凝固过程。