Application of Thermodynamic Database to Corrosion of ZrO_(2) Containing Submerged Entry Nozzle in Steel Continuous Casting Process

The CALPHAD thermodynamic databases are very useful to analyze the complex chemical reactions happening in high temperature material process.The FactSage thermodynamic database can be used to calculate complex phase diagrams and equilibrium phases involving refractories in industrial process.In this study,the FactSage thermodynamic database relevant to ZrO_(2)-based refractories was reviewed and the application of the database to understanding the corrosion of continuous casting nozzle refractories in steelmaking was presented.

Clogging behavior of submerged entry nozzles for Ti-bearing IF steel

The nozzle clogging behavior of Ti-bearing IF steel was studied by metallographic analysis,scanning electron microscopy（SEM）, energy dispersive spectroscopy（EDS）,and X-ray diffraction（XRD）.According to the experimental results,nozzle clogging primarily appears three layers.There are a lot of large-sized iron particles in the inner layer and mainly slag phase in the middle and outer layers.The principal clog constituents of the inner layer are loose alumina cluster inclusions and granular shaped alumina inclusions,containing iron particles. The clog constituents of the middle layer are mainly dendrite alumina inclusions.The primary phases existing in nozzle clogging are FeO·TiO2 and FeO·Al2O3 besidesα-Al2O3 and a-Fe.The FeO·TiO2 phases among the deposits adhere the deposits together firmly enough to lead to the inferior castability of Ti-bearing ultra low carbon steel compared with that of Ti-free low carbon Al-killed steel.

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 electromagnetic stirring on flow field in mold under submerged entry nozzle clogging

A physical model with mercury as analog was developed to investigate the influences of electromagnetic stirring（EMS） on flow field in slab continuous casting when the submerged entry nozzle（SEN） was clogged with different clogging rates（0,10% ,25% ,and 50% ）. The flow field in mold under different EMS currents（0, 40 A, and 60 A） was measured by an ultrasonic Doppler velocimeter. The results proved that the flow field in the mold was a typical double roll structure under non-clogging SEN. As the SEN clogging rate increased, the flow field structure was transformed from a double roll to asymmetry flow. When the clogging rate reached 50%, the up circulation disappeared on the clogged side. The zone under the meniscus near the narrow face was a non-flowing area. EMS could correct bias flow caused by SEN clogging and improve the symmetry of the flow field during SEN clogging.

Research Progress on Anti-clogging Technology of Submerged Entry Nozzles for Continuous Casting

The causes, the formation process, and the prevention of submerged entry nozzle(SEN) clogging were introduced. The influence of electric field on the SEN clogging was focused on, including the basic theory and measurement of SEN charging,the preliminary research on SEN charging, the influence of molten steel on the wetting behavior of refractory materials in electric field, and the influence of electric field on the oxide inclusions in molten steel. Based on the influence of the hydrodynamics, chemistry and other factors on refractory materials, structure, inclusion particle transfer and adhesion, many anti-clogging researches have been carried out, such as optimizing process conditions, compositing anti-clogging inner lining materials, innovating SEN structure and applying physical fields, which solve the problem of SEN clogging to a certain extent.However, the problems of weak adaptability and superficial study on clogging mechanism are still prominent. The electric field control is a new technology to prevent clogging. Although it has achieved certain results in on-site continuous casting trials,some problems such as the method of applying electric field, the electric field parameters and the equipment still need to be gradually improved, and the surface characteristics of inclusions and SEN materials at high temperatures need to be further studied. It was pointed out that the combination of materials and applied electric field will become an important direction for SEN anti-clogging technology.

An Innovative Submerged Entry Nozzle Design for Billet and Bloom Casting

Fluid flow in the mold has a significant impact on the quality of continuously cast steel products.Since it is strongly influenced by the SEN design,attention has to be paid on its geometry.In this paper the main principles of a novel SEN type will be described.Water modeling and Computational Fluid Dynamics(CFD)are applied to characterize the flow pattern under different conditions.Furthermore,the interaction with electromagnetic stirring(M-EMS)is analyzed by means of a liquid melt model.Finally,actual steel plant performance data and observations are discussed.

Velocity Monitoring of Molten Steel in a Continuous Casting Mold Using Three Submerged Entry Nozzle Designs

The horizontal and vertical velocity components of molten steel in a slab continuous casting mold produced by three different two-port Submerged Entry Nozzle (SEN) designs are monitored and compared using Computational Fluid Dynamics (CFD) simulations. These two ports designs correspond to a conventional cylindrical SEN, a plate SEN and an anchor-shaped SEN. Four monitoring points at the molten steel in the centered vertical plane were selected to track the horizontal and the vertical component of the velocity vector. Two of them are located near the free surface and the remaining two are located in the vicinity of the SEN discharge nozzles. Some statistical values of the time series of above the velocity components are analyzed and correlated with the Kelvin-Helmholtz instability and the Karman vortex streets, which cause mold powder entrapment in the molten steel.

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.

Structure Optimization of SENs and Upper Nozzles

The structure of SEN and upper nozzles was optimized and simulated. Relevant trials were conducted on site during thecasting of Al-killed steel. These optimizations effectively solve the nozzle clogging and reduce the defects of the casting slab.

Development of a New Subermerged Entry Nozzle in Thin Slab Caster

The fluid flow in the mould of the thin slab continuous caster has a large intluence on the quality of slabs and its productivity.The fluid flow pattern can be controlled by the SEN (Submerged Entry Nozzle) structure. Traditional SEN can not decrease the surface turbulence and penetration depth at the same time, especially at high casting speed. In order to improve the fluid flow in the mould, a new structure SEN-Dissipation SEN have been invented. The water modeling experiments proved that the dissipation SEN could satisfy, the needs of fluid flow condition in the mould at high casting speed.

连铸浸入式水口(SEN)的发展

随着连铸技术的发展,连铸用功能耐火材料之一的浸入式水口也取得了很大的发展。介绍浸入式水口的作用和结构及其材质的发展。

连铸用浸入式水口(SEN)的发展

浸入式水口是连铸用关键功能耐火材料之一,其使用效果直接影响连铸效率和铸坯质量。随着连铸技术的发展,浸入式水口也经历了不同的发展阶段。本文介绍了浸入式水口在连铸中的位置及其作用,着重介绍了不同时期不同材质浸入式水口的优缺点和几种具有防堵功能的浸入式水口,并对浸入式水口的发展趋势进行了分析。

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.

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.

Structure Design of SEN for High Efficiency Thin Slab Continuous Casting

Four-hole submerged entry nozzles （SEN） with dif- ferent structures were researched using the water simula- tion test by particle image velocimetry （PIV） and DJSO0 hydraulic measurement system to get suitable SEN for high efficiency continuous casting. The influences of the exit area ratio （2： 1：2, 3：2： 3, 1： 1：1 and 1：2： 1）, upper guide island angle θ （20°, 40°, 60° and 80°） , and lower guide island angle α （60°, 80°, 100° and 120°） on the vortex position in the mold and fluctuations were researched. The results show that the exit area ratio and the upper and low guide island angles have ob- vious influence on the flow field; the flow field in the mold is suitable at 1：2：1 of the exit area ratio, 80° of upper guide island angle, and 100° of lower guide island angle.

Effect of SEN structure on the mold level fluctuation and heat transfer for a medium thin slab caster

It is important to select suitable parameters of a submerged entry nozzle （SEN） for optimizing the flow and temperature patterns in a mold. The effect of SEN design on the mould level stability, meniscus steel flow velocity, and heat transfer of the mold of a medium thin slab caster was studied by means of 1：1 water modeling and industrial testing. The advantages of a 2-port SEN compared with a 3-port SEN are the following： more optimal flow patterns with a lower mold level fluctuation and a lower meniscus steel flow velocity; proper powder consumption without slag bears due to a reasonable liquid powder thickness. The argon flow rate can be reduced and the mold average heat flux and temperature near the edges of the copper plate are reduced. At a casting speed of 2.5 m·min^-1, the mold level fluctuation lies within ＋5 mm. In addition, soft cooling of the steel shell in the mold is realized, which is suitable for casting crack susceptible steel grades.

Finite Element Analysis on Thermal Stress of SEN

Thermal stress of SEN was studied by using finit element analysis（ FEA）. The results disclose：（ 1） fo the tapered zone of SEN,the thermal stress reaches it peak after casting for about 30 s,at this moment,th axial stress is the largest,the circumferential stress come the second and the radial stress is the smallest;（ 2）when SEN suffers the thermal stress,the inner wall suf fers the pressure stress,and the shorter the distance from the inner wall is,the larger the pressure stress is; th outer wall suffers the tensile stress and the shorter the dis tance from the outer wall is,the larger the tensile stres is; the axial stress holds a dominant position in the ta pered zone,while the circumferential stress takes the lead in the cylindrical zone;（ 3） as angle α of SEN’s taper ed zone increases, the thermal stress grows obviousl when α is larger than 110°; while the thermal stress re duces obviously,when α is larger than 140°; thus,fo SEN design,it is essential to avoid the interval of α =110°- 140°.

Al_(2)O_(3)夹杂物在浸入式水口内衬材料上的成核与反应性研究

浸入式水口复合无硅无碳内衬材料是减缓结瘤堵塞的重要措施。为深化研究Al_(2)O_(3)夹杂物在浸入式水口内衬表面的结瘤现象,采用晶格失配计算及高温模拟试验验证的方法研究了钢液中Al_(2)O_(3)夹杂物在氧化锆质、尖晶石质、刚玉质、莫来石质内衬材料上的成核趋势及反应;基于显微结构观察分析了异质形核机理和沉积过程。结果表明:Al_(2)O_(3)夹杂物与刚玉质、氧化锆质、尖晶石质、莫来石质内衬材料的二维失配度分别为0%,30.97%、8.43%、11.14%,表明Al_(2)O_(3)夹杂物易于在刚玉质内衬上成核,难以在氧化锆质内衬上成核,氧化锆基材料适宜作为浸入式水口防堵内衬材质。高温模拟试验结果与二维失配计算结果相一致,氧化锆基内衬不易与钢液发生反应且表面Al_(2)O_(3)结瘤程度较轻,仅为刚玉质、尖晶石质、莫来石质内衬上Al_(2)O_(3)结瘤厚度的1/2。本工作基于晶格失配理论提出了一种抗Al_(2)O_(3)结瘤内衬材料优选策略,可为开发高性能功能耐火材料提供科学指导。

浸入式水口结瘤机制及优化措施

在钢铁实际生产过程中,浸入式水口结瘤会对结晶器流场的稳定性产生严重影响。这种现象不仅影响了连铸过程的顺利进行,还可能导致结瘤物剥落,从而降低铸坯质量。阐述了浸入式水口结瘤机制的研究现状,从优化水口结构、优化水口材质、提高钢液洁净度以及施加外部电场共4个方面总结了防止浸入式水口结瘤的措施,并对浸入式水口防结瘤未来的研究方向进行了展望。

Formation of Dense Inclusion Buildup on Submerged Entry Nozzle by Electric Current Pulse

In this work, low-density electric current pulse （ECP） has been applied to submerged entry nozzle （SEN） and its effect on the morphology of the inclusion buildup and the distribution of the inclusions in slab has been explored. The results reveal that under the unique effects of ECP, part of small inclusions less than 10 μm is expelled through the boundary layer along the current direction to form dense inclusion buildup. This method is of great potential to prolong the service life of SEN and improve the quality of the steel product.