Flow and Temperature Fields in Slab Continuous Casting Molds

In order to develop super-board and super-thick slabs, the flow and temperatur fields were studied in slab continuous casting molds under different practical conditions, such as slab dimensions, with-drawing slab speed, design of nozzles, and superheat tempera-ture. The results showed that it is preferred to incline nozzle bores downwards and the submerged depth of the nozzles is best kept be-tween 250-300 mm. In addition, the solidified shell is thicker at the wide face than that at the narrow face, while the thin points alongthe wide face ekist both in the center and in the some area toward each respective end.

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.

INFLUENCES OF CASTING SPEED AND SEN DEPTH ON FLUID FLOW IN THE FUNNEL TYPE MOLD OF A THIN SLAB CASTER

In recent years, thin slab continuous casting technology has been widely used to improve the quality of the product and to reduce the cost. One of the challenges faced by this technology is to design reasonable flow patterns, which strongly affect the surface and inner properties of the final slab in the mold. With the fixed scales and complex geometrical structures of nozzle and funnel type mold, a series of numerical simulations are made to analyze the flow patterns in melt steel using finite volume method based on structured body fitted coordinate grids. The CFD （computational fluid dynamics） package is validated first using one typical case described in previously published studies, and then it is developed to study the effect of operational parameters on fluid flow in thin slab caster. Two operational parameters, casting speed and SEN （submerged entry nozzle） depth, are mainly considered for numerical analysis. On the basis of present simulations, the reasonable SEN submergence depths corresponding to different casting speeds are suggested according to fluid flow characteristics like, flow jet impingement on the narrow side of the mold, flow speed of the melt steel beneath the meniscus and the recirculation region. This is the first stage of study on the numerical analysis of the whole thin slab casting process with electromagnetic brake.

Behavior of Liquid Steel in Mold for Thin Slab Caster

The comparison of different submerged entry nozzles(SEN)was made by numerical simulation regarding the influence of liquid steel flow field,heat transfer and mold fluxes,as well as solidification shell stress and surface quality of thin slabs.The optimum internal shape of mold and the SEN were obtained.The foundation for choice of internal shape and casting parameters of mold was built.

Study on Flow in Mold With EMBr in Slab Continuous Casting

A mercury model has been developed to investigate the influences of Electromagnetic Mold Brake Ruler(EMBr-Ruler) and Flow Control Mold(FC Mold) on metal flow in slab continuous casting mold with the practical casting speed 1.0,1.3 and 2.0 m/min respectively.FC-Mold can efficiently repress the surface flow and its fluctuation.The expanding space of the jets is compressed by EMBr-Ruler and FC-Mold respectively,then the 'flow passage' where the vertical velocity of flow increases sharply is developed near the narrow wall with EMBr-Ruler and FC-Mold.It is bad for the development of the plug like flow.Only the nozzle ports are placed in the braking magnetic field region and the casting speed is suitable,EMBr can be beneficial to the formation of the plug like flow.The flow regime is improved with FC Mold when the casting speed is high(2.0 m/min),but EMBr can improve the flow field with medium casting speed(1.3 m/min),but when the casting speed is low(1.0 m/min),the effects of two types of EMBr are both unsatisfactory.

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.

高建钢Q420GJZ35大型夹杂物行为

对河钢集团唐山中厚板材有限公司生产的高建钢Q420GJZ35大型夹杂物的种类、数量、尺寸等进行了试验研究,并在钢包渣、中间包覆盖剂、中间包打结料中分别加入Ba、La、Ce示踪元素追踪夹杂物来源。研究结果显示:稳态坯中大型夹杂物总体含量为16.8 mg/10kg;非稳态铸坯中含量最高36.2 mg/10 kg,根据示踪检测结果,部分夹杂黏附有钢包渣、结晶器保护渣和保护渣,其中结晶器卷渣是夹杂物的一个重要来源。通过优化改进浸入式水口,将水口由单侧口改为双侧口,侧孔长度由105 mm改为100 mm,水口出口为带圆角的方孔,并进行数值模拟分析。结果显示,改进型水口计算结晶器流场分布合理,表面波动较小,符合设计要求,有利于表面钢液的合金化和杂质的上浮。

Fundamental Study on Continuous Casting Process With Swirling Flow by Electromagnetic Force

Swirling flow in a submerged entry nozzle is effective on improving quality of casting block and casting speed in continuous casting of steel.A new method for swirling flow generation in the nozzle has been proposed by the authors,that is a rotating electromagnetic field is set up around a submerged entry nozzle(SEN)to induce swirling flow in it by Lorentz force.In this study,the magnetic field in molten steel in the submerged entry nozzle,the flow and temperature field in the SEN and mold in round,square billet and slab continuous casting process of steel are numerically studied.The model experiment of electromagnetic swirling continuous casting is also conducted with low melting point alloy.The commercial test for slab is undergoing.Results by numerical simulation and experiment show that the swirling flow by the optimum designed electromagnetic swirling generator can not only improve the distribution of flow and temperature in mold but also achieve the same effects generated by the swirling blade process. And,more effects on continuous casting process can be expected after this electromagnetic swirling process is optimized.

浸入式水口结构影响板坯连铸结晶器钢液流动行为的研究进展

浸入式水口(SEN)是板坯连铸结晶器钢液流动的引导装置.优化浸入式水口结构、改善钢液流动行为,对生产优质铸坯具有重要意义.首先,对板坯连铸工艺中广泛应用的浸入式水口结构进行总结.其次,梳理了浸入式水口结构影响钢液流动行为的国内外研究:明确了水口的内孔、侧孔、底孔/底部等结构参数及其浸入深度对钢液流速、液面波动及流动模式等的影响规律;讨论了近几年伴随新的工艺要求出现的创新型浸入式水口结构及其应用限制.最后指出:一方面,浸入式水口结构优化应随着板坯连铸结晶器最佳钢液流场的确定而进一步发展;另一方面,考虑水口结瘤的实际情况,应开展浸入式水口结构动态变化的相关研究,从而精准控制钢液流动,促进连铸坯质量提升.

薄板坯连铸结晶器内钢液流场电磁制动的模拟研究

采用模型实验结合数值模拟的方法分析了薄板坯连铸结晶器的电磁制动过程．在模型实验中，测量了磁感应强度和工质锡液速度场．在数学模型中，使用低Reynolds数湍流模型封闭动量方程结果表明：电磁制动能够有效地控制结晶器内流场．随着磁感应强度的增加，射流强度逐渐减弱直至在中途被堵截转向同时，包括液面在内的整个结晶器内流场速度逐渐降低．在采用带形磁场制动的情况下，结晶器内液态金属的感应电流呈现为大范围的涡流分布．

攀钢板坯连铸结晶器内流场的水力学模拟研究

采用水力学模拟方法研究攀钢板坯连铸结晶器内流场，分析浸入式水口结构尺寸、塞棒吹Ａｒ量和拉速等工艺参数对连铸结晶器内钢液流动状况的影响，在此基础上优选出适合攀钢板坯连铸工艺的浸入式水口结构尺寸及相关参数。

超宽板坯结晶器内流场和温度场的耦合数值模拟

以南钢3250超宽板坯结晶器为研究对象,基于商业软件FLUENT,建立了超宽板坯结晶器三维有限体积模型,对结晶器内钢液流动状况和传热行为进行了耦合数值模拟,研究了超宽板坯结晶器流场和温度场特征,考察了水口结构参数和结晶器宽度尺寸、水口倾角、水口插入深度、拉速、过热度及冷却强度对超宽板坯结晶器流场和温度场的影响,多组对比模拟计算结果表明,当浸入式水口出口倾角为15o,插入深度为120~150mm,拉速为1.2~1.4m/min时,结晶器自由液面速度和湍动能分布以及注流冲击点深度均较为适宜,流场较为合理;同时结晶器内钢液的温度分布相对均匀,有利于坯壳的均匀形成.数值模拟结果可为优化南钢超宽板坯结晶器浸入式水口结构以及确定合理工艺参数提供理论依据.

高拉速厚板坯连铸结晶器流场影响因素的模拟研究

运用数值模拟研究方法,研究高拉速厚板坯连铸结晶器流场的影响因素;研究浸入式水口结构、水口控流方式、水口出口角度、水口浸入深度、结晶器宽度、结晶器厚度、吹氩等因素对结晶器流场、液面流速以及初生坯壳的影响。结果表明在高拉速下,结晶器的流场不稳定因素增多,工艺参数对结晶器流场的影响因数增加。在高拉速下结晶器流场流速高,液面波动大,液钢流束冲击深度大,势必造成产品质量的下降趋势,因此高拉速厚板坯连铸过程必须采用电磁制动或流场控制技术,降低高流速带来的不利影响;水口结构与结晶器规格最优化与匹配能得到适宜的结晶器流场;同时发现高拉速钢液流束对结晶器初生坯壳的影响严重,是高拉速漏钢率高的直接原因之一。

PIV用于板坯连铸结晶器流场的实验研究

将粒子图像测速技术应用于板坯连铸结晶器内流场研究.结合1550mm×160mm板坯结晶器内腔尺寸,采用1:0.5水模型进行实验,研究了拉速、浸入深度、水口倾角等参数对结晶器流场的影响.结果表明,结晶器液面波动、流股对结晶器窄面的冲击及回流区涡心位置与以上3种参数直接相关.随着拉速增加,结晶器内的流速随之增大,液面波动明显,上下部回流区延伸范围增加,涡心位置下移;采用较大的水口浸入深度和水口倾角,射流在结晶器窄面的冲击位置下移,可以有效稳定液面,避免卷渣.

宽规格板坯连铸结晶器浸入式水口的数值模拟

利用Fluent计算软件建立三维数学模型对马钢板坯连铸结晶器内钢液的流场和温度场进行数值模拟研究,并进行正交试验,分析了水口浸入深度(150～190 mm)、水口侧孔倾角(-10°～-16°)、水口侧孔与中孔的截面积比值(2,2～3.2)对拉速0.9 m/s,230 mm×1800 mm结晶器内钢液流动的影响。研究结果表明,水口浸入深度和倾角对结晶器液面波动F数和凝固坯壳厚度的影响较为显著。对于浇铸断面230 mm×1800 mm的结晶器浸入式水口的最佳工艺参数为:浸入深度170 mm、水口侧孔倾角13°、侧孔出口与中孔面积比2.7。

板坯连铸结晶器浸入式水口结构研究

在实验室条件下,基于某厂实际水口结构及生产状况重新设计了4种不同结构的浸入式水口,然后采用1∶1的水模型对该厂600 mm×170 mm断面板坯连铸结晶器的流场特征进行试验,通过对比分析不同拉速下采用不同结构浸入式水口时结晶器内钢液的流场特征的变化情况,从而优选出适合该厂的浸入式水口结构。研究表明,在拉速≤1.6 m/min时,采用底部形状为凸底、出口倾角18°、侧出孔尺寸为40 mm×60 mm的椭圆形水口,结晶器内流场最为理想,即为最优水口结构。

220 mm×1600 mm板坯连铸浸入式水口倾角优化的数值模拟和应用

使用数值模拟方法研究了拉速0.9m/min时,水口倾角-7°^-11°对220 mm×1600 mm板坯结晶器内坯壳厚度、坯壳温度和自由液面流动的影响。模拟和应用结果得出,以拉速0.8 m/min,水口倾角-15°工艺下钢液流动为标准,通过对比计算结果与标准工艺曲线,确定在0.9 m/min拉速时,水口倾角为-11°为最佳工艺方案。生产应用结果表明,采用优化工艺后结晶器窄面报警频率由原15次/月降至0次/月,铸坯表面质量也有一定改善。

气体流量及水口底部形状对板坯结晶器内流场影响的水模型试验

采用1:1水模型研究了气体流量(0~10 L/min)和水口底部形状(凹底和尖底)对结晶器内流场的影响。在结晶器断面为230mm×1 200 mm,浇铸速度为1.6 m/min的模拟工况条件下,凹底水口其流体形态优于尖底水口;在结晶器液面波动稳定性方面凹底水口亦优于尖底水口;气体流量在0~8 L/min,使用尖底水口的流体其表面流速明显高于使用凹底水口的流体;对凹底水口而言,气体流量超过8 L/min,其流体表面流速低于0.2 m/s;120炉IF钢生产结果表明,使用优化的凹底水口和吹氩流量7 L/min,浇铸过程结晶器液面波动在±3 mm以内,铸坯夹杂物比优化前降低24%。

水口浸入深度对结晶器内钢液流场与温度场的影响

采用软件CFX4.3和新的结晶器入口速度赋值方法,数值模拟了水口浸入深度150～450 mm时板坯结晶器内钢液的速度和温度分布。结果表明,随着水口浸入深度的增加,结晶器内钢液流场和温度场的基本特征保持不变,但上部回流区范围增大,下回流区的涡心下移;窄面所受的向上和向下的最大剪切力的值变大,峰值出现位置下移;窄面热流密度峰值的位置下移,浸入深度为300 mm时,热流密度的峰值最小;射流对窄面撞击点的位置也随之下移;弯液面处钢液的水平速度呈逐渐减小的趋势,反映自由表面波动的F数逐渐变小。对于侧孔倾角为向下15°、结晶器截面为1 200 mm×250 mm、拉坯速度为1.0 m/min的工况,最佳的浸入深度为300 mm。

薄板坯连铸结晶器流场模拟和验证

针对薄板坯连铸结晶器内钢液的流动特征,利用有限差分方法对薄板坯结晶器内钢液的流动进行了模拟,建立了结晶器内三维流动的数学模型,模拟了复杂水口结构对结晶器中钢液流动的影响。通过水力学模拟对流场模拟进行了验证。结果表明:流场模拟能够准确反映具有复杂水口结构特点的结晶器中的流动现象。