Lining Of Ladles Research Articles

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.

Pragmatism in industrial modelling: An application to ladle lifetime in the steel industry

A methodology for building pragmatic physics-based models is here adapted to predict the erosion of ladle linings in the steel industry, in order to support operators when deciding whether the lining can be used safely for another heat. A defective lining may allow 140 t of molten steel to spill, with disastrous consequences for workers and plant. The adopted work flow for the development, challenges faced, and some model results are presented. One key learning outcome is that model development should allow time for maturing the process understanding, as well as for many iterations by 'questions-responses and actions' at various stages in the model development. Good interaction between the development team and industry case owner is an important success factor. Combining or extending the model with the use of machine learning and cognition-related methods, such as knowledge graphs and self-adaptive algorithms, is discussed.

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.

Effect of the hydrotalcite formation on the fracture behavior and corrosion resistance of HA‐bonded alumina‐spinel castables

AbstractHydratable alumina‐bonded castable is a promising non‐cement bonded refractory for ladle lining. An in situ formation of layered double hydroxides (Mg–Al hydrotalcite, M–A–H) using reactive MgO powders is proposed as a means of enhancing the castables during curing, drying, and after the high‐temperature treatment. The formation of hydrotalcite, spinel transformation, pore structure, mechanical properties, fracture behavior, and slag corrosion resistance have been systematically investigated. The results indicate that the hydrotalcite formation is governed by the hydration reactivity of MgO, which promotes the formation of Mg(OH)2 as an intermediate hydrate, and the ultimate growth of hydrotalcite. The residual MgO and newly formed hydrotalcite are eventually transformed into micron size and submicron size spinel, respectively. This structural evolution contributes to an optimized pore structure and microstructure, enhancing the castables. The ultimate pore structure and enhanced interfaces between aggregate and matrix facilitate the improvement of toughness and slag corrosion/penetration resistance.

Analysis of the Cooling Modes of the Lining of a Ferroalloy-Casting Ladle

Analysis of the Cooling Modes of the Lining of a Ferroalloy-Casting Ladle

Lightweight corundum–spinel ladle wear lining castable with low thermal conductivity

AbstractDesigning a lightweight wear‐lining refractory is of great significance for energy savings and consumption reduction. In this study, an in‐house manufactured porous alumina aggregate was selected to replace the commercial tabular alumina aggregate to prepare lightweight corundum–spinel castable (LCSC) for ladle linings. The effect of the porous alumina aggregate on the properties of the corundum–spinel castable was investigated. Compared to tabular alumina, porous alumina possesses higher closed porosity (12.1%) and a small pore size (4.25 µm). The thermal conductivity of LCSC is 21.5% lower than that of dense castable at 1000°C. Owing to the existence of micropores in the porous alumina, the fabricated corundum–spinel castable showed an improved degree of bonding between the aggregate and matrix. Therefore, the lightweight castable showed higher flexural strength and considerable slag corrosion resistance than the dense castable.

APPLICATION OF GRADIENT DEFORMATION CRITERION FOR ANALYSIS OF THERMOMECHANICAL DESTRUCTION OF REFRACTORIES IN A TEMPERATURE FIELD

An approach to the analysis of refractories thermomechanical destruction in service under the influence ofrapid temperature change, called as thermal shocks, is proposed. The proposed approach, based on sequential calculations of the temperature field in the refractory lining and the fields of elastic thermal deformations of the material, performed by the finite element method. The obtained results processed using the deformation gradient criterion of brittle fracture introduced by the authors.The introduced criterion allows identify zones of onset of crack formation, determine the moment of the onset of destruction and predict the direction of crack growth, using of the dynamic calculation of temperature fields in the lining and the calculation of the corresponding static fields of elastic deformations of materials. In addition, the temperature dependence of the elastic properties of refractory materials taken into account, a feature of which is a change in the nature of destruction from brittle to plastic at operating temperatures close to the phase transition temperature of the refractory material or any of its components.Various options for installing products in linings and the corresponding fields of elastic deformations that arise during a sharp rise in temperature in the unit considered. Sharp one-sided heating of one of the lining surfaces is the most dangerous stage of operation of high-temperature equipment from the point of view of thermomechanical stresses.An assessment of the average speed of crack propagation and the possibility of stopping it during the growth process subsequently carried out by analyzing the energy state of the vicinity of the crack tip by comparing the energy of elastic deformation of the material region with the surface energy of the growing defect. The practical application of the approach and validation of the research results considered using the example of a typical failure of the working lining of a steel-pouring ladle.

Effect of calcium aluminate-based additive on properties of periclase-carbon refractories for steelteeming ladles

Premature decommissioning of steel-teeming ladle lining due to critical localized damage, whichi significantly reduces the functional properties of the lining, is one of the most acute problems in modern metallurgy. The main type of products used for steel-teeming ladle lining is periclase-carbon. In order to improve corrosion resistance and resistance to thermomechanical loads, additional additives, such as spinel, and high alumina CMA cement, are introduced into the periclase-carbon products. In this paper, the effect of calcium aluminate-based additive on the properties of periclasecarbon refractories is investigated. It is assumed that there is a potential for the formation of magnesium aluminate spinel (MA) in periclase-carbon products with calcium-aluminate additives during heat treatment. Fused periclase was used as the raw material, the carbon component was represented by natural flake graphite in an amount of 10 wt% and a combined binder. An additive based on calcium aluminates was introduced, with a fractional size from 0 to 3 mm, while the amount of main fractions of fused periclase was reduced by the corresponding amount of the additive introduced. The compressive strength, apparent porosity, and bending strength values before and after coking firing were analyzed. The thermal coefficient of linear expansion, phase composition and microstructure of the products were also investigated.

The in-situ formation of Mg-Al hydrotalcite and its effect on the properties of MgO-bonded alumina castables

MgO-bonded castables are one of the promising non-cement bonded refractories used for ladle lining. To make crack-free MgO bonded castables, the formation of layered double hydroxides (Mg-Al hydrotalcite) is proposed. In the present work, the influences of Al(OH)3 and hydratable alumina (ρ-Al2O3) and different curing temperatures (40 °C, 60 °C, 80 °C) on the formation of hydrotalcite are investigated. The hydration behavior and corresponding hydrates are examined using electrical conductivity, XRD, SEM, FTIR, and TG-DSC analyses. The results show that the increase in curing temperature is more conducive to the formation of hydrotalcite, where ρ-Al2O3 significantly promotes the formation due to the enhanced reactions between intermediates of Mg(OH)2 and Al(OH)3. After high-temperature treatment, the decomposition of a larger amount of hydrotalcite and Al(OH)3 and thereafter growth of microcrystalline spinel contribute to refined pore size distribution. Consequently, a higher hydration degree of ρ-Al2O3 and the formation of more hydrotalcite provide a higher bonding strength at room temperature, and the optimized microstructure enhances high-temperature strengths.

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)

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.

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

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.

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.

Improved comprehensive properties of Al2O3-MgO-C refractories containing lightweight tabular alumina aggregates

The lightweight of ladle lining refractories is of great significance to energy saving and consumption reduction. In this work, the lightweight alumina aggregates were selected to partially replace traditional tabular alumina aggregates to prepare lightweight Al2O3-MgO-C refractories used for steel ladle linings. And, the influence of lightweight alumina aggregates on the comprehensive properties of Al2O3-MgO-C refractories was investigated in detail. The results illustrated that the introduction of lightweight alumina aggregates can improve the strength of Al2O3-MgO-C refractories, due to the optimized interface bonding between aggregates and matrix. In addition, the thermal shock resistance of Al2O3-MgO-C refractories was also enhanced after adding lightweight alumina aggregates, which should be attributed to that the addition of lightweight alumina aggregates reduced the thermal expansion coefficient of such refractories, and micron-sized pores of lightweight alumina aggregates absorbed partial thermal stresses during thermal shock test. Furthermore, the addition of lightweight alumina aggregates improved the slag corrosion resistance of Al2O3-MgO-C refractories remarkably, which can be ascribed to the formation of continuous CA6 protective layer and densified matrix.

Computer simulation of steel ladle secondary lining layers effect on localisation and direction of thermal cracks propagation

A study of crack formation in refractory lining of steel ladles during molten metal pouring into the ladle has been carried out by means of mathematical modelling.The aim of the work was to find out thermal and mechanical conditions under which cracks might initiate in lining elements and to predict the orientation and characteristic length of such cracks. Numerical investigation has been carried out using finite and discrete elements methods. Local fracture analysis was carried out with the application of criteria effectively taking into account various elementary fracture mechanisms. Typical cases are studied, in which hot layer of the lining is characterised by different mechanical constraint conditions and temperature conditions at the back surface, determined by features of the buffering and heat-insulating layers condition of the equipment lining. General patterns of crack initiation in different areas of the product under thermal shock caused by pouring molten metal into the ladle are specified. It has been identified that the presence of a temperature gradient parallel to the hot face can lead to a deviation of the crack trajectory mainly in the direction of the hot area of products. Ill. 5. Ref. 30. Tab. 1.

Characterisation of mortarless refractory masonry joints under elevated temperatures

Refractory linings are commonly employed in Industrial vessels used in high-temperature processes to protect them against extreme working environments. The working lining of an industrial steel ladle frequently employs mortarless refractory masonry to contain the molten steel and limit heat losses. Such masonry lining undergoes high thermomechanical loads, primarily due to thermal expansion arising from thermal and mechanical boundary conditions. Dry joints, described as a physical break in the continuum, reduce some of these effects. Therefore, understanding dry joints is an essential factor for developing numerical constitutive models that employ a meso or macro modelling approach. This work aims to experimentally investigate the normal compressive behaviour of dry joints in refractory masonry. For this purpose, various refractory specimens of alumina-spinel material are tested from ambient temperature to 1200 °C. The results obtained from these experiments are then used to identify critical joint parameters with different mathematical models for the interface. The outcome describes exponential joint closing behaviour with respect to the force applied. It was observed that the pressure required to close a joint reduces with an increase in temperature. The exponential model was then used to numerically simulate the joint closure of mortarless refractory masonry. Finally, numerical and experimental results were compared.

Multi‐Response Optimization of the Thermal and Thermomechanical Behavior of a Steel Ladle Lining using Grey Relational Analysis and Technique for Order Preference by Similarity to Ideal Solution

The present research attempts to simultaneously optimize the thermal and thermomechanical behavior of a steel ladle lining. The lining configurations are designed with an L32 orthogonal array considering the input parameters of various material properties and lining thicknesses. From the finite‐element (FE) simulations, three responses are evaluated: the end temperature and maximum tensile stress at the steel shell and the maximum compressive stress at the hot face of the working lining. Multi‐response optimization is performed through grey relational analysis (GRA) and the technique for order preference by similarity to ideal solution (TOPSIS) by applying a distinguishing coefficient of 0.5 in GRA and the signal‐to‐noise (S/N) ratio‐based weight in both techniques. Both GRA and TOPSIS results yield the same best solution (the fourth lining configuration) and the same optimal levels for significant factors. Analysis of variance (ANOVA) is used to identify the significance of the factors and their contributions to the overall performance characteristic. The results demonstrate that the top five factors with the analyses of GRA and TOPSIS are the same and their total contribution is similar.

Alumina‐spinel castable for steel ladles: An overview

AbstractAlumina‐spinel castable has excellent refractory properties, including high volume and thermal stability, good hot strength, and excellent resistance against corrosion, erosion, and thermal spalling. Excellent refractory properties have made it a preferred lining for steel ladles, reducing the erosion and corrosion of molten metal and slag and improving the ladle life and efficiency for decades. These castables are also significant for the replacement of chrome‐bearing refractories that cause several health hazards. The current review paper covers preformed and in situ spinel containing alumina castables. It focuses on the importance of these castables in the sidewall and bottom portion of the steel ladle in detail, the effect of spinel and MgO content, and the factors affecting castable properties. The review also covers the final properties of castable and the application areas of alumina‐spinel castable in steel ladle, purging plugs, and RH‐degasser.