Mixing and Residence Time Distribution in an Inert Gas-Shrouded Tundish

Tracer dispersion experiments were carried out in a multi-strand tundish by injecting 1 (N) NaCl solution into water. The variation of dimensionless concentration–time curves known as C-curves and mixing times with different gas flow rates were studied. The proportions of dead, mixed, and dispersed plug volumes were calculated using the ‘modified mixed model.’ The observations were explained by analyzing the behavior of the bubble plume, incoming jet velocity, and turbulent kinetic energy within the tundish.     

Investigation of Eccentric Open Eye Formation in a Slab Caster Tundish

Metallurgical and Materials Transactions B - Inert gas shrouding in tundish can result in the formation of a tundish open eye (TOE) due to the presence of reversed flows on the upper surface of the...     

Modeling of Liquid Steel/Slag/Argon Gas Multiphase Flow During Tundish Open Eye Formation in a Two-Strand Tundish

Metallurgical and Materials Transactions B - Multiphase flows are frequently encountered in metallurgical operations. One of the most effective ways to understand these processes is by flow...     

Physical and Mathematical Modeling of Inert Gas-Shrouded Ladle Nozzles and Their Role on Slag Behavior and Fluid Flow Patterns in a Delta-Shaped, Four-Strand Tundish

Inert gas shrouding practices were simulated using a full-scale, four-strand water model of a 12-tone, delta-shaped tundish. Compressed air was aspirated into the ladle shroud to model volumetric flow rates that range between 2 and 10 pct of steel entry flows. Bubble trajectories, slag layer movements, and flow fields, were visualized. Flow fields were visualized using particle image velocimetry (PIV). A numerical model also was developed using discrete phase modeling (DPM) along with the standard k-ε turbulence model with two-way turbulence coupling. Predicted flow fields and bubble trajectories corresponded with the water model experiments.     

Study of Open Eye Formation in an Argon Stirred Ladle

Two cold models were employed to simulate the formation of open‐eyes in a gas stirred ladle. In the first model, water and silicon oils were employed to simulate liquid steel and slag respectively. In the second one, liquid Ga‐In‐Sn alloy was used to simulate liquid steel, while 12% hydrochloric acid simulated the top slag. The experimental results indicated that the gas flow rate, height of the lower liquid and height of the top liquid had a strong impact on the open‐eye size. On the other hand, the viscosity of the top liquid and the interfacial tension between the two liquids had only little effect on the open‐eye size. A semi‐empirical model was developed to describe the size of open‐eye as a function of the heights of the two liquids and the gas flow rate. The two sets of parameters obtained for the water and Ga‐In‐Sn models were very different. Industrial trials were also conducted to examine the applicability of the models. The model developed based on the Ga‐In‐Sn model could well predict the formation of an open‐eye during ladle treatment. The model could be adopted by the industry to estimate the real gas flow rate by measuring the size of the open‐eye online. On the other hand, the mathematical model based on water model experiments was unsatisfactory when applied to the industrial ladle process.     

Fluid Dynamics of Vortex Formation in Tundish Operations: Mathematical Modelling

A mathematical model was developed to study the significance of the fluid dynamics of vortex formation in tundish operations. The aim is to contribute to the fundamental understanding of vortex formation and related phenomena. For this purpose a typical slab tundish was employed; the mathematical model was solved using FLUENT® commercial software capable to simulate highly turbulent flows. The well known k‐? turbulence model was applied to compute this effect in the process. The mathematical simulations confirmed the results from a water analogue model. The vortex formation is directly related to the highly turbulent flows present in the reactor. Great changes in velocity fields during short times and large distances between the upper edge of the dam and the free surface of the bath enhance the formation of vortex flows.     

Fluid Dynamics of Vortex Formation in Tundish Operations: Physical Modelling

The present study focuses on the fluid dynamics of vortex formation in tundish operations using a physical water analogue model and Particle Image Velocimetry (PIV) measurements. The aim is to get fundamental knowledge of the nature of vortex formation that clearly represents this flow phenomenon. The results indicate that vortex formation is directly related to the highly turbulent flows present in the tundish. Great changes of velocity fields during short times and large distances between the upper edge of the dam and the free surface of the bath enhance the formation of vortex flows. Therefore, increasing tundish capacity does not guarantee steel cleanliness through long residence times if the dam height is not adjusted to the new level of liquid in the tundish.     

A Compensation Model of Continuous Temperature Measurement for Molten Steel in Tundish

 A compensation model has been proposed to reduce errors caused by the immersion depth of the sensor and the time lag of continuous temperature measurement for molten steel in tundish, which is based on the limited data fitting method and data fusion technology. According to the heat transfer analysis of sensor, the thermal model has been bulit to determine the temperature variation function.The parameters of the compensation model are recognized by generic algorithm, which combines the determine function, the molten steel mass in the ladle and pouring time. The processing of error compensation is divided into three stages: tracking, holding and compensation. When the processing is stable, the measured temperature error is small, and the measured temperature is regarded as accurate value and tracked. For the end of pouring stage of the ladle, the temperature error is caused by the immersion depth of the sensor, and the measured temperature before sharp decreasing is considered as real temperature and held. For the temperature increasing stage after ladle changed, the measured temperature is compensated online.The application results show that the error between the compensation temperatures and the actual ones have been decreased to ±2 ℃, and the time lag could be shortened from 3-5 min to 40 s by applying this model.     

Ni-Cr-Fe-Mo-Co-Cu-W合金宏观"黑斑"和"白斑"缺陷的形成

研究了Ｎｉ－Ｃｒ－Ｆｅ－Ｍｏ－Ｃｏ－Ｃｕ－Ｗ合金宏观“黑斑”和“白斑”缺陷的形成机制。“黑斑”区富集元素主要以数量较多,尺寸较大的富含钼,钨的Ｍ６Ｃ和ＡＢ３Ｃ等相和数量较多的粒状Ｍ６Ｃ的形式存在于晶界上,因界面效应使晶界相对易受侵蚀;“白斑”区晶界主要富含钼,钨的μ相,比富含铬的Ｍ６Ｃ基底区耐晶界腐蚀。     

Influence of Hydrogenation on Electronic and Magnetic Properties of PrNi: A First Principles Study

Electronic and magnetic properties of PrNi and PrNi–H have been investigated by using first principles approach. Calculations are performed using full potential linearized augmented plane wave plus local orbitals method including spin-polarization within the frame work of density functional theory. The electronic exchange–correlation energy is described by generalized gradient approximation. The ground state of both the compounds is base-centered orthorhombic CrB structure. The hydrogen stored in PrNi, i.e., PrNi–H has been studied to analyze the effective changes in magnetic moments and electronic structures in comparison with PrNi. The total cell energy of the hydrogenated PrNi compound has been found to be lower than in PrNi compound. The decrease in the cell energy shows more stability of the hydrogenated PrNi at ambient conditions. The values for total and local magnetic moments decrease on hydrogen insertion in PrNi. A comparative study of the projected density of states in both the compounds has also been presented. Both the compounds are found metallic in nature.     

A Reaction Model for Prediction of Inclusion Evolution During Reoxidation of Ca-Treated Al-Killed Steels in Tundish

A reaction model was developed to investigate evolutions of steel chemistry and inclusion compositions during reoxidation of Ca-treated Al-killed steels in a tundish. The evolutions of Al₂O₃, CaO, MgO, and CaO in inclusions were accurately predicted using the current reaction model. The reaction model can widely predict the evolution of inclusions during tundish reoxidation of Ca-treated Al-killed steels with varying concentrations of Al, Ca, and absorbed oxygen.     

A Conversional Model for Austenite Formation in Hypereutectoid Steels

An on-heating conversional model has been proposed to calculate the volume fraction of austenite in hypereutectoid steels from dilation strain. The transformation strain equation for austenite formation from ferrite and cementite was developed with lattice parameters modified to include alloying element effects. The conversional model was verified by comparing calculations with experimentally measured transformation temperatures and constituent volume fractions in the transformation temperature range for various heating rates. A continuous heating transformation (CHT) diagram was produced from model results.     

板坯连铸双流73 t中间包控流装置优化的水模型研究

根据相似原理采用1:3水模型研究了238 mm×1 500 mm板坯双流连铸73 t中间包不同控流装置对流场的影响,以便得出最佳控流组合及优化的挡墙位置和高度。结果表明,采用双层湍流抑制器和下挡墙配合使用是双流中间包控流的较优组合,当下挡墙位置在模型中距长水口685 mm,高度为152 mm时,平均停留时间相对原型中间包延长了53.5 s,死区比例由27.9%减小到13.1%,较好地改善了中间包内流体的流动形态,有利于均匀钢液温度和夹杂物上浮去除。     

Similarity Criteria for the Study of Removal of Spherical Non-metallic Inclusions in Physical Models of Continuous Casting Tundishes: A More Fundamental Approach

Metallurgical and Materials Transactions B - Physical modeling is widely used for studying steelmaking processes. The accuracy of this technique depends on the use of appropriate similarity...     

A Mechanism Model for Raceway Formation and Variation in a Blast Furnace

In this article, a previous mechanical model is extended to predict raceway penetration in a blast furnace (BF) and to dynamically illustrate how raceway penetration varies over time after the blast velocity varies based on Newton’s second law. The model is validated by industrial measurements, and more precise predictions have been obtained using the present model. Moreover, the effects of combustion reactions on the raceway shape and size are taken into account in the present model. The mechanism for raceway formation and variation revealed by the present model is as follows: Fast movements of packed bed above a raceway roof due to blast blowing rate variation make raceway size vary rapidly and form its prototype; combustion reactions modify raceway size and shape, and they maintain its stability.     

A Model for Predicting the Melt Temperature in the Ladle and in the Tundish as a Function of Operating Parameters during Continuous Casting

A mathematical model for predicting the melt temperatures in the ladle and in the tundish during continuous casting has been developed. First of all, a chain of models was created for the following stages of the ladle cycle; the preheating of the empty ladle, filling of the ladle, period in the ladle furnace, waiting period prior to casting, the casting period, and, finally, the free cooling period of the empty ladle. Models, written in CFD code, were used in sequence so that each simulation continued from the results of the simulation of the previous stage. An intermediate model was constructed to estimate the outlet temperature of melt drained from the ladle. Then the work was continued by performing simulations in the tundish, using as input the temperature of the simulated melt feed from the ladle and, as an initial condition, the temperature field of the remaining melt in the tundish. The final model “TEMPARV3” was created and tested by means of measured tundish data received from a steel plant. By means of statistical analysis the coefficients of correlation between the test data and model data at the start, in the middle period, and at the end of casting were calculated to be 0.9, 0.92 and 0.87, respectively. So, the most effective predictive power of the model in the tundish by means of a sequential casting schedule is realized during the middle period of the casting process. The model is applied interactively by a user interface, which expresses the predicted melt temperatures numerically and with graphical curves. The predictive model can be used off‐line as a tool for scheduling the stage operations in advance. The program may be utilized on‐line to estimate the superheat needed and to control periods of the operation. In extreme cases, when the model alerts the operator about the danger of superheat loss having a critical effect on casting, the operator has a chance to take adjustment measures. In addition to production work, the model could be of benefit for studying changes in operating parameters, for training operators, and for use as a “low‐cost computational pilot plant” in process development in general.