Steel Ladle Research Articles

Effect of MgO on Evolution of Interface Structure between Low‐Basicity Refining Slag and MgO–C Refractory

MgO–C bricks are widely used as a refractory lining in the slag line part of the ladle of a cord steel refining. The dissolution of their main component MgO into the refining slag is one of the main reasons for their shortened service durability. Laboratory experiments are carried out using low‐alkalinity refining slag and unaltered MgO–C bricks by static crucible method. Physicochemical analysis, FactSage thermodynamic calculations, etc., are performed on the specimens, and the dissolution mechanism of magnesia is investigated. When the low‐melting‐point‐phase CaMgSiO4 (CMS) decomposes at high temperatures, the concentration and activity of (MgO) at the local interface between slag and MgO‐C brick increase rapidly, inhibiting the dissolution of magnesia into slag at the CMS in situ. The rapid weakening of the dissolution drive of the slag to the magnesia corrosion occurs when the MgO content in the refining slag approaches saturation. To verify the feasibility of extending the service life of MgO–C bricks at the refining ladle slag line, the study involves controlling the MgO content in the refining slag.

Modernization of ladle refining area in order to expand the steel grades. Methods of ladle refining of steel, peculiarities of low-carbon alloyed steel grades production. Message 1. Implementation of the project for modernization of steel ladle refining area

Внепечная обработка стали – ключевое звено в современных технологических процессах получения качественной стали. Недостаток мощностей на проведение технологических операций на участке внепечной обработки стали в ОАО «БМЗ – управляющая компания холдинга «БМК» образован по причине модернизации дуговых сталеплавильных печей (ДСП) и, как следствие, их высокой производительности, а также необходимостью расширения сортамента. Поэтому одним из стратегических направлений развития металлургической отрасли в ОАО «БМЗ – управляющая компания холдинга «БМК» явилось внедрение инвестиционного проекта «Увеличение производительности внепечной обработки стали» в сталеплавильном производстве. ОАО «БМЗ» с компанией‑производителем оборудования был заключен контракт на разработку проекта, строительства и ввода в эксплуатацию двух установок типа «печь‑ковш» и одного циркуляционного вакууматора типа «RH‑SCOB» с возможностью форсированного обезуглероживания, что позволяет производить новые группы марок стали: особонизкоуглеродистые, низкоуглеродистые легированные стали. Горячие испытания оборудования и отработка технологии производства осуществлялись на протяжении 2019 г., ввод в эксплуатацию данного комплекса произведен 17 марта 2020 г. В ходе горячих испытаний и в процессе ввода в эксплуатацию достигнуты результаты по обезуглероживанию стали до значений C ≤ 0,002 %.

Computer Simulation of the Effect of Steel Ladle Secondary Lining Layers on Localization and Direction of Thermal Crack Propagation

Computer Simulation of the Effect of Steel Ladle Secondary Lining Layers on Localization and Direction of Thermal Crack Propagation

Impact of fast heating and cooling on the mechanical behaviour of alumina-magnesia refractory castables

The alumina-magnesia castables is one kind of monolithic refractories for steel ladle, whose thermo-mechanical properties vary with temperature during the lining pre-heating process and metallurgical service. The understanding of their variation tendency and sensibility to temperature fluctuation is important for the improvement of high-efficiency pre-heating strategy and real-time service performance. In this study, the influence of heat treatment temperature and heating/cooling rate on the thermo-mechanical properties and fracture behaviour of alumina-magnesia castables is investigated using uniaxial compressive tests equipped with an induction heating system and Brazilian test combined with digital image correlation and acoustic emission. The brittleness and mechanical strength of alumina-magnesia castables increase with heat treatment temperature due to the better sintering and formation of calcium hexaluminate and spinel phases. Without full relaxation of residual stresses, the stiffness increases while the strength decreases after fast heating of 200 °C/min. Meanwhile. the same castables after different thermal treatments show disparate mechanical responses to cooling rates.

Prediction of Temperature of Liquid Steel in Ladle Using Machine Learning Techniques

Maintaining the temperature of liquid steel in the ladle in the required range affects the quality of casted billets, reduces energy consumption, and guarantees smooth control of the melting sequence. Measuring its temperature is a challenging task in industrial settings, often hindered by safety concerns and the expensive nature of equipment. This paper presents models which enable the prediction of the cooling rate of liquid steel for variable production parameters, i.e., steel grade and weight of melt. The models were based on the FEM solution of the Fourier equation, and machine learning approaches such as decision trees, linear regression, and artificial neural networks are utilized. The parameters of the model were identified using data from the monitoring system and inverse analysis. The results of simulations were verified with measurements performed in the production line.

Strength-Gain Characteristics and Swelling Response of Steel Slag and Steel Slag–Fly Ash Mixtures

The shear strength and stiffness characteristics of steel slag indicate that it can potentially be utilized as a competent base/subbase material of bound and unbound pavement layers. However, concerns with respect to the utilization of steel slag remain due to its long-term swelling, corrosivity, and leaching characteristics. In this study, long-term swelling and corrosivity tests were performed on basic-oxygen-furnace steel slag (BOFSS) and electric-arc-furnace ladle steel slag [EAF(L)SS] generated in Indiana, USA. In order to reduce the 1D swelling strains of these slags, 5%, 10%, and 20% Class C fly ash (CCFA) and 10% ground rubber replacement ratios were used to prepare steel slag mixtures for testing. The improvement due to CCFA replacement was evaluated by performing unconfined compression and long-term swelling tests on selected steel slag–CCFA mixtures. The seven-day unconfined compression strengths of 90% EAF(L)SS + 10% CCFA and 90% BOFSS + 10% CCFA mixtures were 2,387 and 3,768 kPa, respectively. After nine months of monitoring, the maximum 1D swelling strains of soaked samples of BOFSS and EAF(L)SS mixtures prepared with 10% CCFA replacement were 0.1% or less. The unconfined compression and swelling test results for the steel slag–CCFA mixtures indicated superior strength gain characteristics and negligible swelling strains with time than for steel slags.

Thermodynamic investigations of steel deoxidation process with calcium and barium

The use of alloys with alkaline earth metals (AEM) it possible to optimize the processes of deoxidation and refining of steel from non-metallic inclusions. The technologies of ladle treatment of the melt with the use of AEM complexes to obtain high-quality metal products even if it is impossible to use expensive equipment (vacuumers, tribe apparatus, etc.), which is often typical for small steel foundries. At the same time, a number of issues related to the mechanisms implemented during the refining of liquid steel with calcium and barium require further study. In the course of this work, the authors constructed state diagrams of double (CaO–BaO) and ternary (FeO–CaO–BaO) oxide systems and carried out thermodynamic modeling of equilibria in the Fe–Ca–Ba–C–O system. It is noted that in this system there is an extensive equilibrium region of the oxide melt with solid solutions of CaO-based oxides. The solubility surfaces of components for the temperatures of steel ladle treatment (1550–1600 °С) and for different carbon contents (0; 0,1; 0,4 % С) are constructed for the studied system. A comparative analysis of the constructed diagrams suggests that a change in the carbon content within the indicated limits does not significantly affect the type of the diagrams. It follows that the revealed patterns will be maintained in the production of a wide range of economically alloyed low-carbon steels. It is shown that during the deoxidation of steel without aluminum, and with a calcium content typical for real production processes (about 30 ppm), the expected active oxygen content is about 30 ppm (log[O] = –2.5), which does not meet modern requirements for purity become. At the same time, a change of the barium content has practically no effect on the degree of deoxidation of the metal. Thus, it is shown that the main role of calcium and, especially, barium in the processing of liquid steel is modification and removal of non-metallic inclusions from the melt

Improving the Durability of Steel Ladle Linings in Converter Shop of Nizhniy Tagil Iron and Steel Works (to the 60th Anniversary of the Development of Converter Steelmaking in Russia)

Improving the Durability of Steel Ladle Linings in Converter Shop of Nizhniy Tagil Iron and Steel Works (to the 60th Anniversary of the Development of Converter Steelmaking in Russia)

Application of refractory materials for steel ladles

The article analyzes the service life of refractories and various options for combined lining of steel ladles used in steelmaking shops with out-of-furnace steel processing departments, and identifies the main trends in its development. The use of various types of lining is analyzed based on the experience of Japan, Germany, Austria, and France. The technological conditions of operation of steel ladles with the main lining are considered. Under operating conditions, the lining areas near the slag belt and the place where the jet hits the bottom of the ladle are subject to the greatest destruction, so it is advisable to install high-quality refractories in these areas. In addition, the reasons for the insufficient stability of refractories are identified, including decarburization, corrosion, ladle slag formed during out-of-furnace metal processing, the use of synthetic additives to slag, high thermal conductivity of refractory materials during operation, and others. Ways to increase the service life of steel ladles are identified. It is shown that the world practice is characterized by the use and intensive improvement of the main lining of steel ladles through the use of new materials with increased refractory and operational characteristics. The experience of refractory improvement by Shinagawa Refractories, TYK Corp, Plibrico, Nippon Steel, Krosaki Harima, and IPSCO Steel, including practical testing at production, is presented. It is established that the high cost of consumables and increased requirements for manufacturing technology hinder the massive introduction of the developed technologies at metallurgical enterprises

COMPUTER ANALYSIS OF INFLUENCE OF MELT BLOWING MODES ON LADLE LINING MECHANICAL EROSION

In the process of blowing, turbulent melt flows erode the ladle lining and its thickness de-creases due to mechanical erosion. The thickness of the steel ladle lining gradually becomes thinner with each casting. The degree of erosion depends on the tangential melt speed. In steel production, they try to slow down this wear, because each lining repair costs considerable time and resources. Scientists paid attention to this problem in publications, in particular, on mathematical modeling of lining wear. A large number of conditions of this process are subject to research, in particular, the number and location of blowing tuyeres, as well as blowing power. Firstly, it is necessary to quickly mix the impurity in the melt, and secondly, to preserve the lining of the ladle. Computer visualization and analysis of this process involves its course and results in the form of calculated fields, in particular, wear. The result fields are stored in a database. Also they are added and processed through a specially designed website. It allows researchers to register and fill in the experiment form, as well as add literature sources of data. The list of literature is used in almost all experiments to compare results. Simulation of the process at blowout rates of 40, 60 and 90 l/min and the number of blowout plugs (tuyeres) from one to three showed that the greatest scouring is predicted at the bottom, near the blowout plugs, and the transition to each higher blowout rate increases the scouring intensity by about 15%. Turning off the tuyeres after 1 minute of blowing significantly reduces erosion by at least 35%. If we consider the ladle wall, without disconnecting the tuyere, the flow rate of 90 l/min is the most destructive.

Using calcium-containing injection wire filled with electrolytic calcium in steel ladle treatment

Aluminum is one of the most common deoxidizers; when it is used in the melt, refractory inclusions of alumina are formed. The presence of these non-metallic inclusions negatively affects the purity of liquid steel, mechanical properties, makes casting difficult due to tightening of the steel-pouring fittings. The modification of alumina inclusions with calcium promotes the formation of liquid calcium aluminates, which leads to an acceleration of their removal from the metal due to a higher ascent rate. Having a high affinity for sulfur, calcium reduces its harmful effect by binding it with the formation of calcium sulfides, reducing the anisotropy of steel properties during further rolling. For steel treatment with calcium, injection wires with a calcium-containing filler are used. As a filler can be used: electrolytic calcium, silicocalcium, aluminum-tremic calcium, or ferrocalcium. The paper describes results of the tests carried out on a calcium-containing wire filled with electrolytic calcium and silicocalcium. It is shown that the consumption of calcium when using silicocalcium wire is on average 35 % higher in comparison with calcium injection wire filled with electrolytic calcium. The calcium recovery rate for different steel grades was evaluated using calcium-containing wires of different designs and filler. In this work, the steel pourability was analyzed. As a determining parameter, dependence of change in position of the tundish stopper rod on calcium content in the metal was considered in the sample from CCM. It was established that a wire filled with electrolytic calcium shows a more effective result in comparison with a silicocalcium wire.

Structure Control and Evaluation of Effective Fracture Energy on Alumina-Magnesia Monolithic Refractories Prepared with CaO·6Al<sub>2</sub>O<sub>3</sub> Aggregate

Alumina-magnesium castable refractories are used for the inner walls of molten steel ladles. The main cause of damage to these refractories is thermal shock caused by rapid temperature changes during the loading and unloading of molten steel. Therefore, the thermal shock damage resistance coefficient R'''' is a parameter that expresses the resistance of refractories to thermal shock, and the evaluation of effective fracture energy is important for improving R''''. In this refractory, CaO·6Al2O3 (CA6) is formed from the raw materials alumina and alumina cement; CA6 has the advantage of inhibiting crack propagation and improving mechanical properties. On the other hand, CA6 has the disadvantage of volumetric expansion during formation. Therefore, microstructural changes caused by the formation of CA6 significantly affect the mechanical properties of refractories. In this study, CA6 was used as raw material and replaced with CA6 generated in-situ. The amount of coarse-grained alumina added was adjusted to control the microstructure. The effect of the microstructure change on the effective fracture energy was then evaluated. As a result, the effective fracture energy was improved in the sample with more coarse-grained alumina added, due to the replacement of CA6 aggregate.

Is the in-situ ZnAl2O4 formation an alternative for magnesia-alumina spinel zero-carbon shaped refractories?

The ever-increasing demand for cleaner steels is the driving force for developing zero-carbon bricks. These refractories have some advantages such as lower thermal conductivity and no direct CO2 emissions, reducing thermal losses and environmental impacts related to their use. Aiming at enhancing some properties of these refractories, the addition of spinel-like inducers (MgO or ZnO) was compared. These oxides react with alumina forming MgAl2O4 and ZnAl2O4, respectively. The spinel formation of the former phase is well-known to be a counter-diffusional solid-state reaction, in which the Kirkendall effect leads to residual porosity. This work assessed the diffusion mechanisms in the Al2O3–MgO and Al2O3–ZnO systems, addressing the role played by the Kirkendall effect on the physical and thermomechanical properties of shaped refractory. Supported by XRD analyses, the early gahnite formation, which starts close to 800 °C and is fully completed at 1200 °C, was attested. This fast spinelization, the thermal expansion mismatch between ZnAl2O4 and Al2O3, and the residual porosity due to the Kirkendall effect led to a higher thermal shock damage resistance. Further analysis of the microstructural features highlighted that a homogeneous sintering reaction was carried out between the MgO and Al2O3 oxides. However, for the ZnO-containing composition, substantial voids were present between the matrix and aggregates due to the Kirkendall effect, inhibiting the sample densification. Additionally, a coating was formed at the alumina-coarse boundaries, indicating a high ZnO diffusion from the matrix to the aggregates. This resulted in higher porosity, and thus diminishing the mechanical strength, which could not be suitable for the working linings of steel ladles. However, controlled generation of residual porosity enhanced the thermal shock damage resistance. Moreover, the addition of ZnO can help to anticipate the in-situ spinalization for applications in the aluminum industry or to produce pre-reacted spinel-like ZnAl2O4 raw materials.

Large‐scale fabrication of TiC@C powders and its effect on the properties of Al2O3‐MgO‐C castables

AbstractHigh performance carbon containing castables have always been pursued by researchers and steelmaking producers, unfortunately, poor water‐wettability of graphite flakes was greatly limited their application in castables. To respond this, we proposed a large‐scale and low‐cost modified molten salt shielding synthesis technique for fabricating TiC coated graphite in air atmosphere using graphite flake and Ti powder as raw materials. Microstructure, wettability and oxidation resistance of TiC@C powders, and effect of TiC@C powders on the properties of Al2O3‐MgO‐C castables were investigated. The results demonstrate that TiC coated graphite was synthesized via modified molten salt shielding synthesis route in air atmosphere. A uniform and continuous TiC layer was formed on the surface of graphite, thereby significantly improving the water‐wettability and oxidation resistance of graphite flakes. The castables with 5% TiC@C powders possessed lower apparent porosity, higher cold strength, good oxidation resistance, and slag resistance in comparison with the castables with graphite flakes, and slag resistance were also better than Al2O3‐MgO castables. The as‐fabricated TiC@C powders have good water‐wettability and oxidation resistance, making them as a prime carbon source for producing carbon containing castables for steel ladle linings.

Determination of cohesion and friction angle of a MgO-C refractory at room and elevated temperatures

The use of constitutive models in thermomechanical finite element modelling of refractory linings requires knowing the temperature-dependent material parameters. The mechanical testing of carbon-containing refractory materials at elevated temperatures necessitates the protection of samples from oxidation. Therefore, the test concept of the modified shear test (MST) was further developed and a setup was designed to protect the carbon-containing materials from oxidation. A carbon-containing magnesia refractory (MgO–C), which is usually applied in secondary metallurgy for steel ladle refractory linings, was selected as the material of interest. The setup allows the determination of cohesion and friction angle of MgO–C refractories under reducing conditions at temperatures up to 1500 °C. The procedure allows a material parameters determination from uniaxial loading. While coked and as-delivered samples showed different behaviours, a significantly higher cohesion was noted in the as-delivered material. The results showed that the cohesion is highly temperature-dependent, whereas the friction angle remains nearly unaffected.

Anisotropy of fracture mechanical properties of carbon-containing refractories and its impact on cracking in a steel ladle lining

Cracks are occasionally observed in bricks installed in steel ladle sidewalls. Three magnesia-carbon refractories used in steel ladles were investigated in terms of the anisotropy of the mechanical properties and their possible contribution to crack formation. The main differences between these bricks were the direction of the moulding force and the type of press used (spindle or hydraulic press). This study aimed to clarify the reasons for the inferior performance of one refractory material compared to other materials from a thermomechanical point of view. The results showed clear anisotropy in the elastic and fracture mechanical data. Brittleness was the lowest and crack propagation resistance was the highest when the crack extended parallel to the moulding force. Therefore, the lowest cracking vulnerability was observed in the case of a moulding force perpendicular to the longest brick edge and this was verified via field observations.

A mathematical model for the thermal state of a steel ladle

ABSTRACT A dynamic one-dimensional mathematical model was developed for predicting the thermal state of a steelmaking ladle. The model is intended to be used in process control applications, in which fast computational times are desirable alongside model accuracy. The calculation domain was discretized using the finite difference method, and time integration was performed using both the implicit Euler and Crank–Nicolson methods, the performances of which were compared. The model was implemented in Python programming language and validated using data from our own measurements and other studies available in the literature. The results indicate that the model can reproduce the measured temperature evolution of the ladles within 5°C at best. The worst performance was observed during cooling, where the model underestimates the temperature at the innermost measurement point by up to 200°C. With computation times of around 16–23 s for one hour of simulation, the model is computationally sufficiently fast for online applications.

Information Processing Algorithms in the Steel-Teeming Ladles Tracking System in Steelmaking

Purpose of research. The purpose of research is to increase the efficiency of control over the movement of steel ladles in steelmaking, through the development of mathematical and software.Methods. The control of the movement of steel-pouring ladles can be divided into 2 parts: the first is the object detection in the image from a camera located on a certain section of the route, followed by determining the position of the object in the frame, and the second part is identification based on an array of data from different systems. Methods used in research are: mathematical modeling, neural networks, the basics of the theory of algorithms construction, as well as software and hardware of modern computer technologies. The article describes a model for the routes generation for the movement of steel ladles, on the basis of which the control of the movement of steel ladles is carried out. Algorithmic support is a combination of such algorithms as: an algorithm for generating possible routes for moving steel ladles, an algorithm for determining the position of a steel ladle on a route for moving steel ladles, an algorithm for identifying a steel ladle and a generalized algorithm for processing information. The structuralfunctional organization of the tracking system for steel-pouring ladles in steel-smelting production is given.Results. Experimental verification of algorithmic support was carried out on a test data set, which was formed from real technological data. Adaptation and tuning of the algorithms and software will make it possible to apply this software system in steelmaking plants with a different composition of plant units.Conclusion. Control over the movement of steel ladles allows build the process so that the movement of liquid steel will cause minimal heat loss. The need to heat steel in secondary processing units is correlates with energy costs. Thus, reducing heat loss and downtime of steel ladles will reduce energy costs for the entire process.

Analysis of the Effect of Gas Injection System on the Heating Rate of a Gas Stirred Steel Ladle Assisted by Physical Modeling and PIV-PLIF Measurements

In this work, the Planar Laser-Induced Fluorescence (PLIF) technique is applied to study the effect of the number of nozzles, their radial position and the gas flow rate on the thermal mixing during the secondary steel refining under non-isothermal conditions in a water model. In the physical model, three burners have been used to simulate the arc heating during the liquid metal processing.The results suggest that an increase in the gas flow rate and injection nozzles located at the bottom of the model, in the same radial and angular positions as the heat sources affecting the liquid surface, improve the system’s heating efficiency.The use of PLIF proved to be a relevant tool to analyze the heat transfer phenomena and increase the thermal performance of the ladle, opening the possibility of carrying out experiments in non-isothermal physical models of steelmaking reactors, which are currently scarce.

Impact of barium and strontium on calcium recovery level in ladle treatment of steel by complex modifiers with alkaline-earth metals

Increasingly rigid requirements in terms of the steel products quality are forcing the technical experts of metallurgical production to look for new solutions to stabilize the steel quality. Much attention is paid to ladle treatment technologies and selection well-minded composition of modifiers, which makes it possible to reduce steel contamination by non-metallic inclusions. To solve this problem, complex modifiers containing both calcium and other alkaline-earth metals (barium and strontium) are used. The paper presents the results of the pilot scale tests of steel ladle treatment by complex modifiers with alkaline-earth metals (Si, Ca, Ba) in steel production with increased requirements to non-metallic inclusions in conditions of electric furnace steelmaking shop of JSC “Ural Steel”. During experimental work it was possible to reduce the maximum contamination score profile rolled steel from pipe steel grades for brittle silicates (GOST 1778) from 4.0 to 1.5 – 2.5, for non-deforming silicates from 4.0 to 3.0 – 3.5. The substitution of SK40 grade silicocalcium for experimental modifiers led to an improvement in the strength properties of rolled products, both in tensile tests and in impact bending tests at low temperatures. The indicated impact was observed in all variants of consumption the experimental master alloys. It is noted that with an increasing in the consumption of master alloys, the positive effect on the steel mechanical properties enhanced. It was established that the replacement of silicocalcium with experimental variants of master alloys made it possible to increase the calcium recovery by an average of 1.6 times when using Si – Ca – Ba, and by an average of 2.4 times when using Si – Ca – Ba – Sr. The use of complex modifiers made it possible to obtain the target value of residual calcium in the sample at significantly lower calcium consumption.