Steel Ladle Research Articles

Thermomechanical behavior of alumina–magnesia castables and numerical modeling of the steel ladle thermal process

AbstractBy experimental characterization and numerical modeling, the dependence of thermophysical properties on time and temperature as well as its influence on the thermomechanical behavior of alumina–magnesia castables has been studied in this work. The thermal conductivity, thermal expansion coefficient, and Young's modulus are the most important parameters, which evolve with temperature and piecewise change with the thermal processes of drying, preheating, and service. It is mainly related to the sintering degree and amount of formed calcium aluminate and spinel phases. The sensitivity analysis of parallel simulations for multilayer steel ladle with different numbers of temperature‐dependent thermophysical parameters demonstrates that the thermal conductivity is the most influential parameter, as it dominates the temperature distribution and affects the succeeding thermal expansion as well as deformation. The increase of thermal expansion coefficient and decrease of Young's modulus with temperature counterbalance the deformation of linings under thermal process. Meanwhile, compared with the simulation using temperature‐independent parameters, the model with temperature‐dependent thermophysical parameters exhibits more severe damage in outer surface of both the working lining and the permanent lining. This gives new insight into the adoption of temperature‐dependent parameters for actual thermomechanical behavior evaluation of refractories.

Optimizing the Steel Ladle Thermal Management: Toward a Sustainable and Cost‐Effective Ladle Fleet Logistics

Optimizing the Steel Ladle Thermal Management: Toward a Sustainable and Cost‐Effective Ladle Fleet Logistics

Phase transition heat storage and self-healing mechanism of spinel-calcium aluminate composite aggregate in corundum castable

Corundum-spinel castable is a vital refractory material used in steel ladle linings. Conventional approaches for assessing the thermal shock resistance of corundum-spinel refractory are not entirely representative of the actual application scenarios. This study investigates the influence of spinel-calcium aluminate composite aggregate on the thermal shock resistance of corundum castable using supersonic frequency induction heating technology. The research uncovers how CMA aggregate enhances the thermal shock resistance of corundum castable by cyclic thermal shock tests under varying operational conditions. Results reveal that the incorporation of CMA aggregate led to significant improvements in cold crushing strength and strength retention ratio following thermal shocks. The observed enhancement predominantly stems from the presence of CA/CA2 phase within the CMA aggregate, which undergoes a solid-liquid phase transition at high temperatures, enabling the absorption and retention of substantial heat and aiding in the repair of microcracks within the materials and at the interfacial regions.

Effect of Cr2O3 additive on alumina-spinel and alumina-magnesia castable

Alumina-spinel and alumina-magnesia castables are important for steel ladle applications primarily for the bottom and side wall areas respectively. Presence of spinel in alumina castables enhances the resistances against corrosion and thermal shock and improves the performance and service life of the steel ladles. Development of these type of castables is planned in the present study in presence of Cr2O3 as an additive using high alumina cement as binder. Variation in spinel (10 and 20 wt%) and MgO (2.8 and 5.6 wt%) content was also explored, along with two different particle size distributions (q value 0.21 and 0.29) for different flow consistencies. The castable compositions were processed conventionally and evaluated for various refractory properties after heat treatments at 110, 1000 and 1550 °C. Both the castables showed well developed refractory properties with alumina-magnesia castable having better slag resistance due to greater extent of calcium hexa aluminate phase formation protecting the refractory.

Wettability of non‐metallic inclusions and its impact on bubble‐induced flotation kinetics

AbstractCeramic refractory bubbling devices may be applied in the steel ladle to induce the flotation of non‐metallic inclusions to the slag phase. These inclusions have many origins along the steelmaking process and induce a detrimental effect on the mechanical properties of these metals. Therefore, the design of high‐performance ceramic plugs relies on understanding the fundamentals of non‐metallic inclusions captured by the gas bubbles. This study investigated the flotation dynamics of hydrophobic and hydrophilic hollow glass particles through experimentation using a water model and quantifying the particle concentration via light scattering. Both types of particles exhibited a comparable natural flotation removal rate, whereas a 40% increase for hydrophobic particles was observed when introducing 1.1 mm bubbles (at 25 NL/h) enhancing the efficiency from 43.1% to 65.2%. For hydrophilic particles, the efficiency increased from 59.1% to 86.2% when bubbles were injected into the system, whereas the removal rate decreased by 2.1‐fold. The consequence of the practice of inert gas purging to remove non‐metallic inclusions is also discussed.

Adaptive Neuro‐Fuzzy Inference System‐Long Short‐Term Memory Hybrid Model to Forecast Castability of Al‐Killed Steel Prior to Continuous Casting

Continuous casting of aluminum (Al) deoxidized steels demands careful inspection due to the occurrence of submerged entry nozzle (SEN) clogging, leading to unexpected production stops. Recognizing the castability of a specific “cast” by monitoring the condition of the SEN is essential for uninterrupted casting. With this information prior to casting, operators can take preventive action against possible clogging occurrences, thus reducing unplanned downtimes. In response to the severe implications of SEN clogging, this work introduces a novel way to forecast castability of Al‐killed steels. A hybrid model is proposed that integrates the adaptive neuro‐fuzzy inference system (ANFIS) and long short‐term memory (LSTM) networks. The output of the model helps to anticipate the event of clogging by analyzing both the past condition of the SEN and changes in the steel chemistry during the transport of the steel ladle from refining to the casting process. A comprehensive analysis of 150 casts helped to build the ANFIS algorithm for estimating the castability index (CI) parameter from steel chemistry. LSTM algorithm is used as a subsequent step to forecast castability in the next 20–25 min. Discrepancies between the predictive response and the actual conditions are reported. Although the real‐time implementation of the proposed model is the ultimate goal, the focus of this work was to present the methodology and demonstrate its potential.

Development and experimental characterization of the thermomechanical behavior of a scaled steel ladle

AbstractA steel ladle usually employs mortarless refractory masonry in the innermost layer in direct contact with molten steel. The behavior of such masonry under high thermal loading is complex and essential for designing such installation. A large‐scale experimental campaign was carried out focusing on a simplified, laboratory‐scaled, pilot steel ladle built with multiple refractory linings as in an industrial ladle. Tests were performed under transient thermal loading up to 1400°C with new and used working linings. The results showed that the distribution of temperatures between the refractory linings was similar for all specimens and confirmed the importance of the selection of the refractory materials in the distinct linings of the ladle to limit heat losses. The heterogeneity in the distribution of dry joints and the effect of the dry joint thickness were also measured using strain gauges. The measurements indicate the effect of viscoplasticity in the working lining on the steel shell, which shows a progressive reduction in the strain starting at 1200°C. The tests performed on the working linings show lower strain built‐up due to large viscoplastic deformation and increased joint thickness.

A pragmatical physics-based model for predicting ladle lifetime

In this paper we develop a physics-based model for lining erosion in steel ladles. The model predicts the temperature evolution in the liquid slag, steel, refractory bricks, and outer steel shell of the ladle. The flow of slag and steel is due to forced convection induced by inert gas injection, vacuum treatment (extreme bubble expansion), natural convection, and waves caused by the gas stirring. The lining erosion takes place by dissolution of refractory elements into the steel or slag. The mass and heat transfer coefficients inside the ladle during gas stirring are modelled based on wall functions which take the distribution of wall shear velocities as a critical input. The wall shear velocities are obtained from computational fluid dynamics (CFD) simulations for a sample of scenarios, spanning out the operational space, and a model is developed using curve fitting. The model is capable of reproducing both thermal and erosion evolution well. Deviations between model predictions and industrial data are discussed. The model is fast and has been tested successfully in a 'semi-online' application. The model source code is available to the public at [https://github.com/SINTEF/refractorywear].

Numerical Simulation of Transient Flow and Heat Transfer in a Steel Ladle During Holding Period

Numerical Simulation of Transient Flow and Heat Transfer in a Steel Ladle During Holding Period

High-temperature tensile strength of alumina-spinel refractory by Brazilian test at 1200°C coupled with DIC in-situ monitoring

This study investigated for the first time the corrosion effect of Al2O3-MgAl2O4 refractory by steel ladle slag using a DIC-coupled Brazilian test at 1200 °C. Three types of alumina-spinel materials were used in the test, namely, original non-infiltrated refractory, slag-infiltrated at 1450 °C as well as postmortem refractory after 69 cycles of work in the sidewalls of steel ladle. Lab infiltration was conducted at 1450 °C using CaO-Al2O3-SiO2-based ladle slag and its analog enriched with manganese (10% MnO). The tensile strength of postmortem material at 1200 °C was the highest at 10.7 MPa, and it was 52% and 70% higher than for reference and MnO-enriched slag, respectively, and 80% higher than for original refractory. The significantly raised tensile strength of slag-infiltrated materials vs. original non-infiltrated brick was directly related to the densification of microstructure by corrosion products (mainly CA6, CA2, Fe) which caused the infiltrated materials to be stiffer and with a more brittle nature to fracture.

Corrosion mechanism and microstructure evolution of industrial used Al2O3-ZrO2-C slide plates

Slide plates are one of the most important functional refractories that control the flow of molten steel from the steel ladle to the tundish. In order to improve the service performance of slide plates and accelerate continuous production of the steel industry, a detailed post-mortem analysis was necessary. In this study, the corrosion behaviors of the high-temperature heated Al2O3-ZrO2-C slide plate used one heat for a 200 tons steel ladle in industry were investigated. The results showed that the thermo-mechanical properties' mismatch led the formation of radial cracks, which was the main factor limiting the service life of the slide plates. Besides, corrosion microstructure revealed the dissociation of mullite-zirconia aggregates and the loss of graphite provided a channel for the penetration of molten steel. The penetration of molten steel could react with Al2O3 in the slide plates, which accelerated corrosion in the early stage and formed a composite spinel layer in the later stage to block corrosion. Also, acicular CaAl12O19 was formed behind the composite spinel layer, further blocking the penetration of molten steel. Furthermore, the ZrO2 from mullite-zirconia had an interlocking structure to prevent corrosion. Finally, the content and viscosity of the liquid phase at different positions of the used slide plates were calculated, which indicated that the area near the casting hole had more liquid phase and lower viscosity. This would further optimize the service performance of the slide plates.

Steel Ladle Slag Zone Lining Optimization Considering Irreversible Material Behavior

The optimization of refractory linings is a complex task due to the many factors that influence the thermomechanical behavior. This study applies the multiparameter optimization method technique for order preference by similarity to the ideal solution to a commercially used slag zone lining of a secondary metallurgical steel ladle, considering the influence of different material models in a finite element (FE) simulation. The dataset is acquired by varying the working lining brick shape, initial expansion allowance (IEA), and isolation layer thickness. The maximum irreversible strain, joint opening at the hot face, and steel shell temperature are determined from the FE simulation results and used as the input values for the optimization. A larger circumferential brick dimension combined with low IEA is favorable for the von Mises creep model. The main contribution is from the IEA (98.53%). The optimized lining for the Drucker–Prager criterion has a brick with a small circumferential dimension and larger IEA. The main influencing factor is the brick shape (85.06%). The differences in the optimization results and factor contributions can be explained by the contribution of the constitutive models to the simulation results before and after the thermal shock.

Simulation Analysis of Influence of Argon Gas Injection Hole Position on Flow Field in Steel Ladle

Simulation Analysis of Influence of Argon Gas Injection Hole Position on Flow Field in Steel Ladle

Insight into the formation of slag eyes and the mechanism of slag entrapment in the steel-ladle refining process: Hydraulic modeling and numerical simulations

Slag eyes are the upper exposed areas of molten steel in a refining ladle that are formed due to excessive bottom argon bubbling. This phenomenon frequently occurs in the steel-refining process and can lead to slag entrapment and re-oxidation of molten steel. Taking a 150-t industrial steel ladle as the research object, the effects of a dual-plug gas-blown process on the slag-eye size were studied using hydraulic modeling and large-eddy simulations. The experimental results showed that at higher gas flow rates such as 9.1 and 11.7 normal liters/min (Nl/min), the relative central angle of the two porous plugs had a significant effect on the slag-eye size; conversely, at lower gas flow rates, its influence could be ignored. Due to the tendency of the two small slag eyes to merge, the 0.6R–45° (R being the bottom radius of the ladle) case resulted in a larger total slag-eye area compared to the cases with other angles. The 0.6R–135° case showed the most beneficial results for reducing the slag-eye size. Additionally, the numerical simulations helped us to visualize the bubble-uplifting and slag-eye formation processes, and they allowed an exploration of the slag-entrapment mechanism. The simulation results showed that the symmetric gas-blown mode can reduce slag entrapment when compared with the asymmetric mode for the 135°–11.7 Nl/min case; this will be favorable to control the cleanliness of the molten steel. Additionally, analysis of both liquid-level fluctuations and turbulent-kinetic-energy distributions further confirmed the advantages of the symmetric gas-blown mode for suppressing slag entrapment.

Investigation of the engineering and environmental properties of cement mortars incorporating ladle furnace steel slag

While the use of ladle steel slag in concrete offers several potential advantages, there are significant research gaps that need to be addressed to promote its safe and effective utilization in the construction industry, e.g. the variations in slag properties, such as chemical composition and physical characteristics, can influence concrete performance. Moreover, even there is some research on the mechanical properties of concrete containing ladle steel slag, more in-depth studies are needed to assess the long-term durability of such concrete and the research should focus more on evaluating the environmental impact of using ladle steel slag in concrete. The paper reports the fundamental findings of a research study focused on the treatment of ladle slag to be applied as a cement substitute in the manufacturing of cement products. The research aimed to determine the optimal proportion of admixture based on treated ladle slag and evaluate the environmental properties of the resulting cement composites. The treatment process involved mechanical activation, specifically grinding the ladle slag fraction of 0/8 mm using a vibrating mill (Coarse slag) and a ball mill (Fine slag). The treated ladle slag, as an admixture, was examined in conjunction with four types of cement (CEM I, CEM II, CEM III, and CEM V). The research findings revealed that the incorporation of coarse ladle slag enhanced the workability of fresh cement paste across all tested formulations. Moreover, the utilization of treated ladle slag as an admixture in cement paste (substituting cement) exhibited a retarding effect on the setting time. As the age of the test specimens progressed (90 to180 days), the strength properties of the samples with ladle slag admixture approached those of the cement composites prepared using natural aggregates. The climate change impact of cement mortars per strength unit spanned from 0.82 to 2.75 kg CO2eq/MPa for composites incorporating finely-ground slag, and from 0.9 to 3.1 kg CO2eq/MPa for composites utilizing coarse slag. The grinding of ladle slag, even up to 30 wt% cement replacement, did not significantly impact the overall global warming potential and climate change, considering the average mill energy consumption of 50 kWh per 1 t of material.

Modeling of Motion of Inclusions in Argon‐Stirred Steel Ladles

A 3D discrete phase model (DPM)‐ and volume of fluid–coupled model is developed to investigate the multiphase flow in a 260 ton argon‐stirred ladle. The flow field and interfacial behavior in the argon‐stirred ladle are accurately predicted. Then, the Lagrangian DPM is used to trace the motion of inclusions in the liquid steel. Residence time maps, which provided the residence time required for inclusions travelling from the bulk liquid steel to the steel–slag interface, are proposed and plotted as functions of inclusion diameter and percentage of inclusions. For inclusions smaller than 10 μm, the average residence time is size‐independent but decreases from 175 to 93 s with an increment in the gas flow rate from 50 to 400 NL min−1. With increasing the inclusion size, the average residence time is dependent on both gas flow rate and inclusion diameter. When the inclusion diameter increases to 1000 μm, the average residence time is almost independent of the gas flow rate. The current model overestimates the inclusion removal rate. However, this overestimation indicates that only appropriately considering the behavior of inclusions at the steel–slag interface can accurately predict the removal of inclusions in argon‐stirred ladles.

Increase in Process Mode Stability by Determining Hot Areas of Steel Ladle

Increase in Process Mode Stability by Determining Hot Areas of Steel Ladle

A theta projection model for compressive creep behaviour of refractories at high temperature: application to alumina-spinel

Thermomechanical loads are normally applied to refractory materials throughout their service life whichever is their practical use (e.g. steel ladle, rotary kiln furnaces). Among all the phenomena that the refractories are exposed to, the influence of creep behaviour is essential in determining their performance. Creep of refractories is usually represented by simple creep laws such as Norton-Bailey, which lack the capacity for generalization. The theta projection creep method, on the other hand, was proposed in the twentieth century to predict the creep of metals and alloys across different temperatures and stresses. The model is represented by one exponential equation capable of representing the complete creep curve, and coefficients that are temperature and stress-dependent, thus enabling the representation of complex nonlinear creep behaviour. Since refractories have similar creep responses to metals, the theta projection creep model is validated to characterize the compressive creep behaviour of alumina-spinel refractories at temperatures between 1200 and 1500 °C. Creep data from steady-state and transient temperature creep tests are used to calibrate the model. A regression by the least square method is applied to calculate the model’s parameters. The model shows good flexibility in fitting the test data of the alumina-spinel refractory over the three creep stages. A temperature and stress dependence model is derived for the theta coefficients, reducing the number of material parameters necessary to describe the material's behaviour. The experimental creep curves are presented, as well as the curves resulting from the identified parameters. The implications of the chosen creep data set on the definition of the model and its adequacy for this novel application are discussed.

Investigation of thermal processes in out-of-furnace treatment of steel with the help of mathematical modeling.

The main method of metal finishing in terms of chemical composition and temperature in modern converter production is out-of-furnace treatment of steel. The duration of stay of metal in the ladle increased several times, which led to an increase in heat losses from the metal, in particular, when blowing metal with inert gas, as well as during transportation of the ladle with metal. While the temperature of steel in the ladle decreased. Therefore, to ensure the required temperature at the next technological operation it is necessary to heat the metal, which will lead to an increase in average process duration and as well as to an increase in energy consumption for steel production. To study the regu-larities of thermal processes in ladles, a two-dimensional mathematical model has been developed that differs from the known ones: using a systematic approach in formalizing the physical description, taking into account heat transfer in slag, taking into account the slag solidification process, taking into account the heat transfer between slag and the ladle lid. It is known that the lid is used for metal casting, while during neutral gas blowing and ladle transportation the lid is used very rarely. Regularities of metal cooling in the steel ladle depending on the application of the ladle lid were estab-lished. A comparative analysis of the results of research on the application of the lid during metal curing in the ladle during out-of-furnace processing of steel has been carried out. The analysis and evaluation of changes in the metal cooling rate and absolutevalues of metal heat loss have been carried out. The study showed that the transportation of the ladle from out-of-furnace processing facilities to the casting stand covered with a lid, will reduce all the heat loss from the metal by more than 2 times. The results obtained can be used to predict the reduction of metal temperature and minimize heat losses during out-of-furnace treatment of metal in the steel ladle.

Distribution of Large‐Size Inclusions in Transition Slabs for Automotive Exposed Panel Steel

In order to improve the quality of the transition slabs, the large‐size inclusions in 28 m‐long transition slabs are studied by large sample electrolysis and thermodynamic analysis. The results reveal that the length of transition slabs influenced by ladle exchange is 17 m, which is 4 m before the second steel ladle casting and 13 m after the casting. Large‐size inclusions in transition slabs can be divided into five kinds of Al2O3, Al2O3‐CaO, Al2O3‐CaO‐SiO2, Al2O3‐CaO‐MgO, and entrapment slag. The average contents of total inclusions, the inclusions in the range of 30–100 μm, those of 100–200 μm, and those larger than 200 μm in the transition slabs are 4.8, 19, 2.8, and 4.2 times higher than those in the normal slabs, respectively. For the large inclusions greater than 200 μm, the average contents of the Al2O3, Al2O3‐CaO‐SiO2 inclusions, and entrapment slags significantly increase in the transition slabs, being 9.4, 13.1, and 2.4 times higher than those in the normal slabs, respectively. The sources of Al2O3, Al2O3‐CaO‐SiO2 inclusions, and entrapment slags should be the secondary oxidation in tundish, entrapment of tundish flux, and entrapment of mold powders, respectively.