Steel Ladle Research Articles

Preparation of resin coated alumina aggregate and its effect on the properties of alumina-spinel castables for purging plugs

Secondary refining processes were indispensable for high-quality steel in the modern steelmaking process, and refining processes in ladles were necessarily performed by argon bubbling through purging plugs, therefore properties and service life of purging plugs were directly impacted on the production efficiency and cleanliness of steel products. To date, purging plugs with slots have been widely used in steel ladles because of their higher strength, stable permeability and higher service lifes. However, poor thermal shock resistance limited their application and enhancement of service life, it is of great significance to improve their thermal shock resistance. In this manuscript, coated aggregates were prepared by coating with phenolic resin on tabular alumina aggregates, and effect of coated aggregates on the properties of alumina-spinel castable was studied. The results show that apparent porosity and permanent linear change rate increase, cold strength and hot strength decrease, and residual strength ratio markedly increase with rising of coating layer thickness of the aggregates, indicating that thermal shock resistance of the sample is significantly improved. The improvement mechanism in the thermal shock resistance of the castables was also discussed in details. The alumina-spinel castables containing microspaces with enhanced thermal shock resistance can be utilized to fabricate longeval purging plug materials for steel ladles.

Study on preformed and in situ spinel containing alumina castable for steel ladle: Effect of fume silica content

AbstractIn the present study, the effect of fume silica content on preformed and in situ spinel containing alumina spinel castable was studied by varying fume silica content at 1 and 4 wt.%. Spinel content for preformed alumina spinel castables varied from 10 to 30 wt.% and MgO content for in situ alumina spinel castables varied from 2.8 to 8.4 wt.%, respectively, and the distribution coefficient (q value) was maintained at .21 and .29 as per Dinger and Funk model. Different castable compositions were processed as per conventional processing technique and further evaluated for densification and strength studies after heat treatment at 110, 1000, and 1550°C. Fired samples at 1550°C were further evaluated for the hot modulus of rupture study at 1400°C and phase analysis study of the matrix phase. Also, the fired samples were studied for microstructural evaluation.

Fundamental studies of physicochemical properties of environmentally friendly fluorine-free slags and their use in ladle steel industry

The article describes theoretical and experimental studies of dependence of viscosity, coefficients of sulfur and boron distribution between slag and metal, and wear degree of periclase-carbon refractories on basicity and boron oxide content in slag. It is shown that formed slags have basicity of 2.0 – 5.0 and rather high liquid mobility. These slags are characterized by an equilibrium interfacial distribution coefficient of sulfur increased to 5 – 20, which provides equilibrium sulfur content in the metal reduced to 0.001 – 0.005 %. The results of fundamental studies of the physicochemical properties of refining slags of СаО – SiO2 – В2O3 – Al2O3 – MgO system formed the basis for development of the composition of environmentally friendly fluorine-free ladle slags and technological methods for their formation in ladle-furnace unit. The recommended composition of such slags of low viscosity, which allows deep metal desulfurization, direct steel microalloying with boron and low aggressive effect on periclase-carbon refractories, provides formation of slags with a basicity of 3.0 – 4.0, containing 1 – 4 % B2O3 , 15 % Al2O3 and 8 % MgO. The formation of environmentally friendly ladle slags of the recommended composition was carried out in a ladle-furnace by loading lime, boron-containing material – colemanite (Turkey) containing 39 – 41 % B2O3 , 26 – 28 % CaO, not more than 5 % SiO2 and 3 % MgO, and pyramidal aluminum into the steel-teeming ladle for slag deoxidation and boron recovery. Introduction of the developed technology for the formation of ladle slags of recommended composition ensured the production of economically alloyed low-carbon structural boron-containing steels with a low sulfur content, incl. for large diameter pipes with high strength properties.

Desulphurization Kinetic Prediction into a Steel Ladle by Coupling Thermodynamic Correlations, Fluidynamics and Heat Transfer

Desulphurization Kinetic Prediction into a Steel Ladle by Coupling Thermodynamic Correlations, Fluidynamics and Heat Transfer

Fundamental Studies of Physical-Mechanical Properties of Environmentally Friendly Fluorine-Free Slags and Their Use in Ladle Steel Industry

Fundamental Studies of Physical-Mechanical Properties of Environmentally Friendly Fluorine-Free Slags and Their Use in Ladle Steel Industry

Bubble generation in refractory porous plugs: The role of the ceramic surface composition

AbstractPorous ceramic plugs are refractory devices applied in the steel ladle to inject gas bubbles into the liquid metal, aiming at its chemical and thermal homogenization, and the removal of non‐metallic inclusions. Regarding its wear and corrosion resistance, the plug composition typically exhibits a low wettability by liquid steel to limit its infiltration into the porous structure. However, an additional aspect for the performance of plugs is their ability to control the size of the generated bubble, maximizing the likelihood of capturing inclusions. Based on the importance of this process to attain high‐performance materials, this work studied the injection of gas into liquid media through ceramic capillary structures, focusing on the influence of the pore diameter and the contact angle upon the size of the generated bubble. The available models in the literature were analyzed and compared to the experimental results for a water–air system. As an outcome, a shape‐corrected model for bubbling is proposed highlighting the region where the material dominates over the pore diameter to dictate the bubble size. Extending the model to the steel ladle, the results suggest the composition of the ceramic plug's surface as a key aspect to improve the cleanliness of the molten steel.

Study on the properties of periclase-forsterite lightweight heat-insulating refractories for ladle permanent layer

The heat dissipation of the ladle permanent layer is urgent to be tackled. Periclase has good compressive strength, high fire resistance, and high chemical stability. The thermal conductivity of forsterite is only 1/3–1/4 of periclase, which is low. Thus, the periclase-forsterite lightweight heat-insulating refractories for a permanent layer of steel ladle prepared from low-grade talc powder and light burned magnesia powder made by low-grade magnesite can well satisfy the requirements of the permanent layer. In this study, the effect of raw material ratio on as-prepared refractories was systematically investigated. The results demonstrated that with the increase in talc, the bulk densities of the samples decreased from 1.73 g/cm3 to 1.46 g/cm3, the porosities increased from 42% to 58%, and the compressive strengths decreased from 49 MPa to 28 MPa; besides, the thermal conductivities decreased from 1.062 to 1.22 W m−1 K−1 to 0.496–0.61 W m−1 K−1 with the increase in forsterite. Additionally, talc promoted the formation of intercrystalline pores, and the synthesis of forsterite in the experiment was dominated by the “Template growth” mechanism.

Preparation and characterization of HA bonded Al2O3–MgO based castables with superior slag resistance for the working lining of Si-killed stainless steel ladles

The study prepared Al2O3–MgO based castables bonded by hydratable alumina (HA) instead of calcium aluminate cement (CAC) for the working lining of Si-killed stainless steel ladles. The microstructure, phase composition, mechanical properties, and slag resistance of castables were investigated by SEM, XRD, and thermodynamic software FactSage®. The results indicated that the HA bonded castables showed superior hot flexural strength, thermal shock resistance and slag resistance than the CAC bonded castables, due to the optimized pore characteristics, less liquid content, and higher liquid viscosity of the castable matrix and the formation of a continuous insulating layer.

Large-Scale Test Facility for Modeling Bubble Behavior and Liquid Metal Two-Phase Flows in a Steel Ladle

Abstract A new experimental facility has been designed and constructed which represents a 1:5.25 model of an industrial 185 t steel ladle. This setup is intended for systematic investigations of complex liquid metal multiphase flows created by gas blowing from the bottom. Two tons of a Sn-40 wt pct Bi alloy are employed as working fluid, its thermophysical properties are very similar to those of liquid steel. The relatively low operating temperatures (T ~ 200 °C) compared to the real industrial process allow the use of powerful measuring techniques for characterizing the behavior of the gas phase and resulting flow regimes. Argon gas is injected through diverse plug systems into a cylindrical fluid vessel which is equipped with a pressure tight lid to achieve low-pressure conditions for vacuum processing. This paper presents first measurements of the gas distribution close to the free liquid metal surface for various gas flow rates, plug positions and types. Moreover, the pressure in the vessel has been varied between 1 mbar and ambient pressure. The experiments provide a copious data base about flow regimes, void fraction, liquid and bubble velocities, and bubble properties, which can be used to provide so far unknown boundary conditions for numerical simulations of various metallurgical reactors such as steelmaking converters or steelmaking ladles.

Development of a calcium aluminate cement from steelmaking slag by altering its mineralogical composition

Strict environmental norms and increasing awareness of the need to recycle solid wastes generated during ironmaking and steelmaking processes are the key driving force for the development of various new materials and manufacturing technologies. In this study, a calcium aluminate clinker was prepared from steel ladle slag by modifying its mineral composition. The slag paste, prepared by mixing slag with water, exhibited flash setting behaviour due to the presence of C12A7 and C3A phases. In contrast, the slag clinker, developed by sintering a mixture of a pre-determined quantity of slag and aluminium oxide at 1400°C for 2 h and 4 h, contained CA, CA2, gehlenite and ‘Q’ phases. Hydrated slag clinker contained stable C3AH6, AH3 and stratlingite with preferential growth of calcium aluminate hydrate prisms along the c-axis, which provided a well-defined raceme-like morphology with an interlinked structure. This improved the setting time and crushing strength of the clinkers after 6 h and 24 h of curing at room temperature. Additionally, the presence of the Q phase, with lamellar prismatic crystals, also helped to enhance strength. The developed clinker also exhibited superior crushing strength as compared with commercially available calcium aluminate cement of medium purity. The slag, used as a source of calcium oxide, could replace calcium carbonate completely and thus contribute to reductions in carbon dioxide emissions during the clinker-making process.

Drying behavior of steel-ladle lining refractory castables under continuous heating rate

The current trend to replace shaped refractories for monolithics is related to various technical aspects, i.e., lack of joints, easier installation and free format. However, the main drawback of these non-shaped products is their longer first heat-up demand, otherwise mechanical failures or even explosive spalling may take place due to steam pressurization within the well packed consolidated structure. As a consequence, over-conservative drying schedules are commonly used in industrial equipment lined with such ceramics, which increase the energy consumption and the production down-time. Based on this scenario and considering the recent advances in numerical simulations, this article discusses the implications of applying different heating rates during the drying of a refractory castable lining of a steel ladle. Additionally, a novel methodology based on the correlation of the maximum vapor pressure and the mechanical strength of the ceramic material was also proposed. Using some of the castable properties measured as a function of temperature, simulation results pointed out that higher vapor pressures and a displacement of the maximum pressure peak are attained by applying high heating rates and thicker linings. This behavior is associated with the water migration to the inner regions of the refractory structure. It was observed that these conditions displace the maximum resistance ratio position towards the hot face, where most common spallings are observed. The work also emphasizes the importance of carrying out accurate measurements of physical properties as a function of the temperature, otherwise the outcome can be far from the reality of the working conditions.

Computational Fluid Dynamics Study of Gas Stirred Ladle Used in the Secondary Metallurgy

The computational fluid dynamics study was developed for simulate the behavior of gas stirred ladle. In this paper, the injection of air in water was simulated, in a scale model of 1/7 of an industrial 35 ton steel ladle with a porous plug located eccentric 2/3 of the radius in order to increase the mixing process and eliminating the dead zones. For the analysis the model the multiphase Eulerian three-dimensional was used. The numerical models has been applied and compared with experiments to investigate their differences and theirs potentials of predicting the flow in gas stirred ladle 3D, transient with turbulence using standard k-epsilon in the finite volume method of the commercial program FLUENT™ 6.3.

The Mathematical Models of the Operation Process for Critical Production Facilities Using Advanced Technologies

The paper presents data on the problems of monitoring and diagnosing the technical conditions of critical production facilities, such as torpedo ladle cars, steel ladles. The accidents with critical production facilities, such as torpedo ladle cars, lead to losses and different types of damages in the metallurgical industry. The paper substantiates the need for a mathematical study of the operation process of the noted critical production facilities. A Markovian graph has been built that describes the states of torpedo ladle cars during their operation. A mathematical model is presented that allows determining the optimal frequency of diagnostics of torpedo ladle cars, which, in contrast to the existing approaches, take into account the procedures for preventive diagnostics of torpedo ladle cars, without taking them out of service. Dependence of the utilization coefficient on the period of diagnostics of PM350t torpedo ladle cars was developed. The results (of determining the optimal period of diagnostics for PM350t torpedo ladle cars) are demonstrated. The system for automated monitoring and diagnosing the technical conditions of torpedo ladle cars, without taking them out of service, has been developed and described.

Treatment and utilization of artificial aggregate in the production of cement composites

The aim of the work is to find a suitable way of treatment of steel ladle slag for subsequent use as a partial replacement of the binder component in cement composites. The goal is based on the raw materials policy of the Czech Republic. Within this work is solved the issue of possible use of steel slag as the largest by-product of steel production. The work is focused on a specific ladle slag from ladle furnaces, by which are equipped the modern steel plants. Ladle slag is similar in chemical composition to Portland cement. However, its mineralogical composition should be taken into account in relation to its expansion reactions and lower hydraulic activity. One of the goals is the research of effect of particle size in cement-slag mixtures. The slag was ground for research on two different specific surfaces - coarsely in a vibrating mill and finely in a ball mill. The research within the experimental part of the work verified the positive influence of ladle slag on the properties of fresh and hardened mortar mixtures. Tensile bending strengths and compressive strengths are for some mixtures with ladle slag even higher than the strengths of the reference mixtures.

Physical Experiment and Numerical Simulation on Thermal Effect of Aerogel Material for Steel Ladle Insulation Layer

The selection of lining material for a steel ladle is important to heat preservation of molten steel. Aerogel insulation materials have very low thermal conductivity, however, they are rarely used in steel ladles. In this paper, the application of a new silica aerogel material on the steel ladle insulation layer is tested, and a new calculation method is designed to study its insulation effect. In other words, the ladle wall temperature is obtained by finite element model (FEM) and experiments, then the heat emission from the ladle wall is calculated by the Boltzmann mathematical model according to the ladle wall temperature, and the temperature loss of molten steel is calculated inversely according to the heat emission of ladle wall. Compared with the original steel ladle (comparison ladle), the application effect is analyzed. Due to the stable heat storage of the ladle wall after refining, the validity of the models are verified in ladle furnace (LF) process. The results show that the new calculation method is feasible, and the relevant parameter settings in the FEM and Boltzmann mathematical model are correct. Finally, after using the new aerogel insulation material, the temperature of molten steel is reduced by 16.67 °C, and the production cost is reduced by CNY 5.15/ton of steel.

Experience of thick-walled calcium-containing cored wire application at steel ladle treatment

Metal processing in ladle by calcium-containing cored wires is one of the most spread methods of ladle treatment and modifying. Results of analysis of efficiency induces of existing cored wires application depending on their diameter, wall thickness and filling coefficient presented. It was shown that the basic efficiency index of a cored wire application – recovery coefficient – depending on wire quality (homogeneity of filling by calcium along the wire length), wire grade, conditions of its injection into liquid steel and other parameters can vary within a range from 50 to 95%. Reasons of unsatisfactory calcium recovery at usage of calcium-containing wires of 14–15 mm diameter with steel shell 0.4 mm thick and filling of mechanical mixture of steel shots and metallic calcium in various proportions was considered. Advantages of the modern calcium-containing cored wire with thicker wall were highlighted, including their higher wire rigidity and stability of its supply by a wire feeder into liquid steel. It was established that calcium content in a cored wire at the level of 100 g/m was the most effective composition. It was noted that increase of speed of cored wire feeding into steel will result in an increase of calcium recovery and in a decrease of probability of metal splashing out the steel ladle.

A creep model with different properties under tension and compression — Applications to refractory materials

Refractories are materials designed to work at high temperatures, and are applied in steel making, cement making, aerospace engineering, and other fields where a combination of chemical and mechanical stability is paramount. Due to such high temperature applications, creep strains play an important role in the mechanical performance of refractories, that often present an asymmetric behavior, i.e., different creep strain rates under tension and compression. The aim of this work is to propose an asymmetric creep model that can be used to simulate the time-dependent non-linear primary and secondary creep behavior of refractories at high temperature. The proposed model uses a split of the stress tensor into positive and negative parts and further calculation of the contribution of each stress sign to the overall strain rate using a weighted average over the equivalent stresses. An experimental procedure is proposed in order to identify the tensile and compressive parameters of an alumina-spinel refractory used in steel ladle linings, using a Brazilian test and a subset-based Digital Image Correlation (DIC) technique, for a temperature of 1300 °C.

Possible ecological advantages from use of carbonless magnesia refractory bricks in secondary steelmaking: a framework LCA perspective

In the present paper, two types of magnesia-based refractory bricks for the wear lining of a steel ladle furnace are considered, with the aim of comparing their ecological performances. The adopted methodology is the Life Cycle Assessment (LCA) approach from cradle-to-gate of the two brick product systems, in accordance with the European and International Standard EN ISO 14044:2006, and the chosen methodology for the Life Cycle Impact Assessment (LCIA) is ReCiPe 2016, considering the midpoint impact categories and the hierarchist perspective. The conducted study is part of a European industrial research project aimed at investigating the possibility of cleanliness improvement of the steel produced in secondary steelmaking, by reducing the refractory contamination in the steel ladle furnace. The compared refractory bricks consist of a reference, currently used, MgO-C type and a more innovative "carbonless" one, containing magnesia and MA sintered spinel as principal components, on the basis of recipe data provided by the industrial partners of the project. The results attained so far in industrial practice are preliminary, because of the lack of a full-ladle lining experimentation, even though the application of the conceived innovative bricks in the upper part of the slag line of the ladle presents promising aspects. The results of the LCIA comparison between the two brick product systems highlight better performances for all the impact categories, except for "Human carcinogenic toxicity" and markedly for "Mineral resource scarcity." Besides these results, a general framework for shifting the ecological analysis to the steel production is provided. Calculations, referred to the production of one tonne of steel, are therefore performed, involving scenario assumptions not only regarding the refractory consumption but also the forecast operational features of the steel ladle with the "carbonless" lining. In this second set of results, it is clear how the principal contribution to almost all the impact categories is the electrical energy consumption of the ladle, while the contribution from the brick product systems remains important for the above-mentioned worsened impact categories, whose magnitude is strongly dependent on the refractory consumption.

Modern concepts of refractory materials application in production of steel and cast iron

Refractory lining is an integral part of metallurgical facilities and requires constant perfection. Examples of successful interaction of specialists-steelmakers, companies-manufacturers of refractories and engineering companies on increasing efficiency of refractories application in steel industry presented. The wide application of drying and heating stations of steel ladles, EAFs, BOFs was noted because of using refractory gunned castable at their current repairs. The growth of unmolded refractory share in the BF production was shown. At the stoves repair technology of guniting and shotcreting is widely used. Transfer to application of modern concrete at lining of shoots, ramming mixtures and repairs with application of liquid concrete addition resulted in a decrease of labor­ intensiveness of repair work, accelerated the process of repair and considerably decreased specific consumption of refractory materi­als. Nevertheless, within a predictable period, despite of increase of unmolded refractories application, it is expected that the molded refractories would take the main share of the refractory market in the steelmaking. Creation of partial load conditions in a metallurgical facility is an important factor for increasing lining resistivity. Slag foaming in EAF screens radiation from electrodes in the process of the furnace running. Blowing of the final slag (preliminary enriched by magnesium oxide in case of necessity) forms a scull on the working surface of the BOF lining, thus preventing intensive contact of the refractory lining with steel melt and slag. Modem technologies of instrumental control the lining state of metallurgical facility within the period of its running considered, which allowto accomplish operation of hot repair at particular arears of the lining, avoiding overconsumption of the repair material. It was noted that apart from the task of decreasing specific expenses for refractory materials, the customers most often estimate the indirect costs, cover of loss and obtaining additional profit due to increase of metal production because of increase of overhaul period and decrease of time of lining repair. This is the purpose of cooperation of specialists of refractories manufacturers and metallurgical plants.

Nonparametric control algorithm for metal temperature mode on site BOF – CCM

A two-level control system for the temperature mode of smelting, out-of-furnace processing and preparation for casting of low-carbon steel G/ET is proposed in the conditions of BOF shop-2 of JSC “United West Siberian Metallurgical Combine”. Depending on the technological scheme, it is possible to design various control systems for the steelmaking complex with sequential, parallel and combined inclusion of individual operations and processes. The control system of a sequential group of objects is considered on the example of steel G/ET. The control system includes an external control loop that allows coordinated control of the shop departments by optimizing the mode of technological process conducting at the facility, taking into account the actual operation performed at the previous facility. The implemented nonparametric algorithm of dual control allows the decision-maker to perform joint operational adjustment of control actions for local control loops. The temperature mode of the melts of low-carbon steel G/ET is analyzed and it is revealed that the processing time of the steel ladle at each stage of the BOF – CCM technological route has a significant impact on the steel temperature mode. In accordance with this, the criteria for temperature control quality are formed. The results of computational experiment showed that the introduction of a control unit with a decision-maker contributes to the rational control of metal temperature mode in the BOF – CCM site, and as a result, obtaining a given chemical composition and temperature of steel within narrower limits. It allows one to eliminate deviations from the contact schedule of the main units, and to increase the number of melts in the series and the rate of continuous casting.