Slag-forming Mixture Research Articles

Interaction of zirconium dioxide with slag-forming mixture of the crystallizer

The corrosive effect of the slag-forming mixture (SFM) of the crystallizer on monoclinic zirconium dioxide, partially stabilized by calcium oxide or yttrium oxide is studied. It was experimentally stated that zirconium dioxide stabilized with yttrium oxide has better corrosion resistance due to the low decomposition rate of the stable phase ZrO2‒Y2O3 when exposed to SFM of the same composition. Ill. 4. Ref. 10. Tab. 4.

On cooling rate of metal melt in steel-pouring ladle and tundish during steel continuous casting

Correlation analysis methods were used to study the thermal state of liquid metal at the stage of steel continuous casting under the assumption that measurable objects are random variables. Thermal state of the metal melt is characterized by the values ​​of the metal temperature Tn at this stage and duration of the stages τn and it is described by an integral indicator – cooling rate Wn . Cooling rate is the ratio of temperature difference of the liquid metal at the beginning and end of the stage to the duration of this stage. The metal cooling rates were calculated at various stages of steel continuous casting. The first stage includes the period from the completion of metal processing at a unit of complex steel processing to the start of vacuum treatment. The second stage includes the period from the start of vacuum treatment to its completion. The third stage includes the period from the end of vacuum treatment to the first temperature measurement in the tundish. And further, there are periods of successive temperature measurements in the tundish. It has been established that the metal cooling rates vary considerably depending on the technological stages. Absolute values ​​of the cooling rate differ by more than an order of magnitude. The minimum metal cooling rate is fixed in the tundish. Its value is 0.09 °С/min. The maximum cooling rate of the metal was revealed when the metal was tapped from the steel-pouring ladle into the tundish, while the cooling rate was 1.43 °C/min. The main factors influencing the metal cooling rate were revealed. These factors include the presence of a layer of liquid slag on the metal melt surface in the steel-pouring ladle after out-of-furnace processing. These factors include initial temperature of the liquid metal after completion of treatment at the unit of complex steel processing, the liquid metal temperature after completion of vacuum treatment, presence of oxide solution formed by slag-forming mixtures on the liquid metal surface, presence and effectiveness of heat-insulating mixtures, as well as the heat-insulating characteristics of refractory linings. During vacuum treatment, the metal cooling rate was essentially determined by convective energy losses and energy losses for heating the inert gas. After the stage of vacuum treatment, the cooling rate is significantly reduced due to the use of heat-insulating mixtures. The highest metal cooling rate is set when it passes through the steel outlet channel and the metal protection pipe when filling the tundish. The lowest metal cooling rate is typical when it is in the tundish, due to the presence of a porous plastic refractory layer with low thermal conductivity.

Implementation of systems for the automated feeding of slag-forming mixtures to the molds of the continuous casting machines of PJSC MMK

The data on the use of installations for the automated feeding of slag-forming mixtures to the molds of the continuous casting machines at PJSC MMK produced by TECHNOAP Engineering Ltd. are presented with an indication of the technical characteristics of the equipment. These installations provide a stable and trouble-free process of continuous casting of steel, high quality of cast billets and finished rolled products. There is a positive conclusion of the scientific and technical center of PJSC Magnitogorsk Iron and Steel Works for testing installations for the automated feeding of slag-forming mixtures. The use of this equipment makes it possible to improve working conditions and ensure the production of high-quality, competitive metal products.

Вибір базових компонентів шлакоутворюючої суміші для одностадійного видалення домішок із чавуну

The article is devoted to research on the development of a variant of the component composition of the slag-forming mixture during complex processing of cast iron for the detection of such impurities as silicon, sulfur and phosphorus. The purpose of the work is to study the composition of soda-containing slag on its physical and chemical properties and to identify the optimal ratio of refining slag components. Using the structure of the model of the process of processing cast iron by injecting reagents into the melt volume through the immersion nozzle, the thermodynamic probability of reactions occurring in the primary zone (at the outlet of the reagents from the nozzle of the nozzle) and the secondary reaction zone formed when the reaction products flowing in primary reaction zone. The value of the equilibrium constants of the corresponding reactions was calculated to assess the priority of the course of reactions of the interaction of system components in the primary reaction zone. The conducted thermodynamic analysis of the simultaneous removal of sulfur and silicon from cast iron by blowing powdered lime in a stream of oxygen and introducing additional reduction into the melt made it possible to state that during the oxidation of silicon with gaseous oxygen for desulfurization of cast iron with the resulting slag, it is advisable to additionally introduce a reducing agent into the melt. The technological parameters and main results of the experimental study of the process of out-of-furnace desiliconization and desulfurization of cast iron by blowing slag-forming materials into 350 kg buckets at the experimental plant are presented. Based on the results, data were obtained on the influence of the basicity of soda-containing slag on its viscosity and temperature. Using the theory of directional chemical bonding, the influence of the basicity of soda-containing slag on its physical and chemical properties was studied, and the optimal ratios of refining slag components were found.

Сучасний досвід десульфурації сталі

Modern technological schemes of steel production do not allow to achieve low (< 0.01 % S) and ultra-low (<0.005 % S) sulfur content on the production of in the metal directly. That is why out-of-furnace steel treatment is often used to remove sulfur. Desulfurization process of steel depends on the chemical composition of the slag, the time of its formation in the ladle, metal oxidation, conditions of mixing of steel in a ladle, additional technological operations and ladle metal processing. Methods are widely used for desulfurization of steel treatment of steel with solid slag-forming mixtures, synthetic slag, lime-aluminous slag, silico-calcium and other powdered materials. Modern approaches to the process of steel desulfurization in conditions steel production are analyzed in the Study. In particular, the Ukrainian (on the example of PJSC ‘Azovstal Iron & Steel Works’ and PJSC ‘Dneprovsky Integrated Iron & Steel Works named after Dzershinsky’) and foreign (on the example of PJSC ‘Severstal’ and PJSC ‘Magnitogorsk Iron & Steel Works’) experience of desulfurization under oxygen converter production. The use of technological complexes ‘Installation of pig iron desulfurization steel making unit’ and ‘Cast iron desulfurization installation steel making unit is ‘oven-bucket’ installation’ provides a deeper desulfurization of steel, the possibility of optimizing the cost of steel production, expands range of scarce products and eliminates a number of restrictive conditions that complicate current production. The analysis of steel C80D desulfurization process is given in the conditions of JSC ‘Moldova Steel Works’, in which partial sulfur removal occurs in an arc steel making furnace, and the ultra-low content is achieved by creating a highly basic refining slag in the process out-of-furnace processing of steel. The study of the kinetics of the desulfurization process of 20GL steel in the conditions of JSC ‘Tashkent Mechanical Plant’ with the use of solid slag-forming mixtures and modification of steel with rare-earth metals is analyzed. The issue of desulfurization of electric steel in the conditions of OJSC ‘Byelorussian Steel Works’ with injection of powdered materials through the installation ‘Velko’ during out-of-furnace processing of steel is considered. Keywords: steel desulfurization, desulfurizer reagent, degree of desulfurization, cast iron desulfurization installation, out-of-furnace processing of steel, ‘‘oven-bucket’’ installation.

An automated system development to control the device for supplying slag-forming mixture into mould of CCM

The mechanism of feeding slag-forming mixture (SFM) with a pneumatic drive has a number of disadvantages associated, in particular, with the uneven supply of the mixture into mould. To eliminate the drawbacks, mixture feeding device with an electric drive was designed to eliminate them. In order to ensure control of the SFM feeding process, an automated system has been developed that provides real-time information on the technological process of feeding the mixture into the mould of continuous casting machine, including speed of rotation of screw drive motors and movement of carriage, the level of the mixture in the bunkers and its consumption, temperature of the metal and slag. A software and hardware complex (SCADA-system) has been developed, which makes it possible to analyze the components of the mixture in the “online” mode and take into account the effect of changes in the supply of each of them on its composition. The dependence of the mixture consumption rate on the casting rate has been established, which can be displayed on the screen in the current mode. Application of the SCADA-system made it possible to control the developed SFM feeder both in manual and automatic modes. It was shown that the implementation of the developed automated SFM feeding device in the steelmaking production of Ural Steel, JSC will secure decreasing the SFM consumption by 2.8% and decreasing downtime by 5% due to increasing efficiency of fault detection with a total implementation cost of 200 thous. rubles.

Sensorless electric drive of the mixture supply system in the mold of the continuous steel casting installation

The system of automatic feeding of the slag-forming mixture into the mold of the continuous casting machine was investigated in this article. The necessity of using a slag-forming mixture in the process of steel production has been substantiated. The proofs are given that the consumption of the slag-forming mixture significantly affects the cost of the final product. The quality level of the final product depends on the uniformity and consistency of the mixture supply to the crystallizer. Therefore, the actual direction is the automation of the process of feeding the slag-forming mixture into the mold of the continuous casting machine. The description of the developed automatic installation, which implements the supply of slag-forming mixture, is presented. The necessity of using a sensorless electric drive for moving the trolley has been substantiated. A simulation model of a bogie electric drive with a vector control system based on sensorless determination of the angular speed of the engine has been developed. The description of the method for determining the angular speed of the motor based on the known values of phase voltages is given. The simulation of the developed electric drive system in the Matlab Simulink program, confirming the adequacy of the developed system. The introduction of a sensorless electric drive into the system for feeding the mixture into the mold of the continuous casting machine will increase the reliability of the entire system and reduce its weight and dimensions.

In-House Produced Slag-Forming Mixtures in the Continuous-Casting Machine in the Oxygen-Converter Plant and the Electric Arc Furnace Shop: Development and Usage

In-House Produced Slag-Forming Mixtures in the Continuous-Casting Machine in the Oxygen-Converter Plant and the Electric Arc Furnace Shop: Development and Usage

An experience of elaboration and implementation of systems of slag-forming mixtures mechanized feeding into CCM moulds

Effective application of slag-forming mixtures (SFM), being fed into continuous castingg machine (CCM) moulds, depends on their even distribution on the melt surface. Manual feeding of the SFM which is widely usedd does not provide this condition, resulting in the necessity to actualize the work to elaborate systems of SFM mechanized feedingg into moulds of various types CCM. A concept of the designing of a system of SFM feeding into CCM moulds presented with the ratte strictly correspondent to the casting speed and providing formation of an even layer of fine material of given thickness on the whoole surface of liquid steel. The proposed methods of designing of the SFM mechanized feeding systems based on three-dimensional computer simulation with the subsequent verification of the correctness of the adopted technical solutions on field samples. Informattion is presented on the design features of the adjusted facilities intended for continuous supply of finely granulated and powder mixtuures on metal mirror in moulds at the production of high-quality billets, blooms and slabs. Variants of mechanical and pneumo-mechaanical SFM supply elaborated. At the mechanical supply the fine material from the feeding hopper is moved at a adjusted distance bby a rigid horizontally located screw. At the pneumo-mechanical supply the metered doze of the granular mixture is delivered by a sshort vertical screw, the lower part of which is located in the mixing chamber attached from below to the hopper and equipped with ann ejector serving for pneumatic supply of the SFM in a stream of transporting gas. It was proposed to use flexible spiral screws in the ffuture facilities of mechanical SFM feeding. It will enable to eliminate the restrictions stipulated by the lack of free surface for locatiion of the facility in the working zone of the tundish, as well as to decrease significantly the mass of its movable part and to decreaase the necessary power of the carriage moving mechanism driver. The novelty of the proposed technical solutions is protected by thhree patents. The reduction of 10–15% in the consumption of slag-forming mixtures during the transition from manual to mechanizeed feeding confirmed. The resulting economic effect from the implementation of technical development enables to recoup the costs inncurred within 8–10 months.

About some criteria of efficiency of complex heat-insulating and slagforming mixtures

The total thermal conductivity of the complex heatinsulating and slag-forming mixture is calculated taking into account the convective component of the thermal conductivity and thermal conductivity of the liquid oxide solution formed by melting the ingredients of the complex mixture. It was shown that the thermal conductivity of the complex mixture at an application temperature of 1823 K remains at a rather low level of about 18,8 W/(m·K). criteria for the effectiveness of the complex mixture at various stages of its application are formulated, including feeding the mixture into the steel casting ladle, joint feeding into the steel casting ladle and tundish and molds. Direct measurements found that the use of a complex mixture in a steel pouring ladle reduces the rate of metal cooling by one and a half times. The criterion for the effectiveness of the use of the complex mixture in the intermediate ladle as a heat insulator is the level of negative temperature deviation from the average value of a series of consecutive measurements of 4 ° C. The criteria for the effectiveness of the complex mixture as a slag former in the tundish are an increase in the concentration of aluminum oxide in the oxide solution with an increase in the number of melts in the series and a decrease in the concentration of iron oxide in the oxide solution to equilibrium values of about 0,5 % by weight. In the presence of a sufficient amount of a liquid oxide solution formed by the components of the complex mixture, carbonization of the liquid metal with free carbon contained in the mixture does not occur.

Selected Performance Criteria of Complex Heat-Insulating and Slag-Forming Mixtures

A total thermal conductivity of a complex heat-insulating and slag-forming mixture has been calculated by accounting for the convective heat transfer component and thermal conductivity of the liquid oxide solution formed by melting the ingredients of the complex mixture. It was shown that the thermal conductivity of the complex mixture at an application temperature of 1,823 K remains at a rather low level of about 18.8 W/(m(K). Performance criteria of the complex mixture were formulated for various stages of its application, including supplying the mixture into a steel-pouring ladle, both a steel-pouring ladle and a tundish, and molds. It was established that by utilizing the complex mixture in a steel-pouring ladle, it becomes possible to reduce the metal cooling rate by 1.5 times. A performance criterion of the complex mixture used as a heat insulator in the tundish is associated with the level of negative deviation from the average temperature value obtained in a series of consecutive measurements (4°C). Performance criteria of the complex mixture used as a slag former in the tundish are related to an increase in the Al2O3 concentration of the oxide solution with an increase in the number of melts in the series, and a decrease in the FeO concentration to equilibrium values (about 0.5 wt.%). Provided there is a sufficient amount of the liquid oxide solution formed by the components of the complex mixture, no carburization of the molten metal with free carbon from the mixture takes place.

Features of ladle desulfuration of pipe steel with low sulfur content

At the present time the sulfur content in pipe steel is strictly regulated. Under conditions of PJSC “Magnitogorsk Iron and Steel Works” the metal is smelted in BOF shop with preliminary desulfurization of molten iron, treatment of tapping steel by a solid slag-forming mixture and final desulfurization in the “Ladle-Furnace” unit (LP-unit). In order to increase the efficiency of the sulfur removal process, the influence of the covering slag composition on metal desulfurization is considered. Statistical processing of production data array consisting of 14 melts of steel grade 10Г2ФБЮ with K60 strength class was performed. The dependences of the sulfur content in the metal after desulfurization in the LP-unit on the oxidizing ability, covering slag basicity and the content of magnesium oxide was established: it is shown that the amount of sulfur removed during the ladle treatment process increases with the increase of the covering slag basicity and with the decrease of the magnesium oxide content in slag. For describing this dependence, a new parameter was proposed – the ratio of slag basicity to MgO content in it, %–1. A high content of magnesium oxide in the “white” slag was revealed. This fact indicates a significant amount of converter slag getting into the ladle due to its poor cut-off in the process of metal tapping from the unit. The study of the influence of the coating “white” slag composition on the metal desulfurization process in the LP-unit showed, that for the effective sulfur removal, it is necessary to provide not only welldeoxidized slag with a total content of iron and manganese oxides of less than 1%, but also to ensure the ratio of its basicity to the magnesium content in this slag not less than 0.60–0.65%–1.

REGULATION OF THE TEMPERATURE REGIME FOR CASTING CARBON AND HIGH-MANGANESE STEEL

The possibility of using insulating slag-forming mixtures based on highly dispersed carbon-containing material (VUM), which is a waste product of primary aluminum production, to reduce heat loss was considered.

Application of “flat’ closed-bottom submerged nuzzles for decreasing rejections of slabs because of longitudinal cracks

In the process of steel continuous casting it was discovered, that due to relatively small distance between a submerged nuzzle and a mold walls, formation of “scull crust” takes place in the area of small and big radius of the billet. It resulted in deterioration of heat-away in mold, conditions are formed for origination of longitudinal cracks following its further opening in the CCM secondary cooling zone. To decrease the number of rejections continuously casted slab billets due to existence of longitudinal cracks, it was proposed to use “flat” closed-bottom submerged nuzzles. It was shown, that in contrast to cylindrical form of a series closed-bottom submerged nuzzle, the proposed one has rectangular section with chamfered butt facet in the are of nuzzle submerging into the mold melt, which enables to ensure better fluidity of slag-forming mixture between the nuzzle and the mold walls. This effect results in onsiderable improving evenness of heat-away. To confirm the effectiveness of the pilot submerged nuzzles application, in 2019 their pilot-industrial tests were accomplished in the campaign of casting of carbon and peritectic steels to produce 200 mm thick slabs at CCM No. 4. In the process of the tests when casting various steels, the same slag-forming mixtures were used. As a result of the tests the decrease of rejections of continuously casted slabs due to longitudinal cracks formation was confirmed.

Experience of Design and Industrial Application of Systems for the Driven Feed of Slag-Forming Mixtures into the Crystallizers of Slab CCM

We consider the structural schemes and the results of industrial application of the systems of driven feed of slag-forming mixtures in the crystallizers of slab CCM of the oxygen-converter shops of two integrated iron-and-steel works of the Donetsk region. We also discuss the prospects of introduction of jointly developed systems of new generation at the enterprises of Russian Federation.

Development and Implementation of the System for Determining the Actual Level of Metal and Thickness of Slag Mixture in the Bloom CCM Mold at JSC “OEMK”

Achieving a higher quality of continuously-cast billets is possible by using a nuclear-type electromagnetic sensor instead of the traditional sensor to measure the level of metal in the mold. A combined use of two types of sensors makes it possible to control the thickness of the slag-forming mixture on the metal surface. The paper describes the experience of implementing a metal level measurement system with electromagnetic sensor at the bloom CCM of the Oskol Electrometallurgical Plant.

MOLECULAR DYNAMIC SIMULATION OF THE MELT OF OXIDE-FLUORIDE INDUSTRIAL SLAG-FORMING MIXTURE

The paper discusses the results of molecular dynamic simulation of a melt of the multicomponent oxide-fluoride system CaO – SiO2 – – Al2O3 – MgO – Na2O – K2O – CaF2 – FeO, corresponding to composition of industrial slag-forming mixture (SFM) used in steel casting for slag targeting in the mold of a continuous casting machine (in wt %: 35.35 % SiO2 , 30.79 % CaO, 8.58 % Al2O3 , 1.26 % MgO, 13.73 % CaF2 , 7.57 % Na2O, 0.88 % K2O, and 1.82 % FeO). These concentrations were converted to mole fractions, and the number of ions was calculated for each of the components in the model. An eightcomponent oxide-fluoride melt containing 2003 ions in the main cube with a side length of 31.01 Å was simulated under periodic boundary conditions at an experimentally determined solidification onset temperature of 1257 K at constant volume. Coulomb interaction was taken into account by the Ewald–Hansen method. The time step was 0.05t0, where t0 = 7,608·10–14 s is the internal unit of time. The melt density was taken to be 3.04 g/cm3 based on our experimental data. The interparticle interaction potentials were chosen in the Born–Mayer form. Based on the simulation results, the structure of subcrystalline groups of atoms present in the melt at the temperature of solidification onset was determined. A discussion of the simulation results and their comparison with the literature data was held. It is shown that the computer model allows one to obtain a fairly realistic picture of atomic structure of the slag melt, indicating that the main structural component of all silicate systems is silicon-oxygen tetrahedron. Tetrahedra in silicates are either in the form of structural units isolated from each other, or, connecting together through peaks, they form complex anions. It is consistent with the theory of slag melts. Molecular-dynamic simulation allows one to obtain adequate information on structure of the melt of a certain chemical composition.

Refining of manganese alloys with high content of phosphorus obtained in electrometallurgical dephosphoration of manganese ores

The expediency of carrying out the process of dephosphorization of the alloy in one stage using a briquetted mixture, which includes iron scale, lime, bauxite and sodium orthosilicate in their following ratio, wt.%: Iron scale - 52.0… 57.4; lime - 6.2… 8.6; bauxite - 4.5… 6.2; sodium orthosilicate - 30.5… 30.4. The achieved degree of dephosphorization of the accompanying manganese alloy is about 70%, the manganese content in the alloy - 64.6%. The implementation of dephosphorization according to the developed method allowed to increase the rate of throughput of manganese from the raw material. Exclusion from the composition of materials for dephosphorization of fluoride compounds increases the environmental friendliness of the refining process. In the real conditions of production in the process of depho-?phorization of the associated alloy may use different processing schemes and conditions of its implementation. In the formation of a concomitant alloy with a temperature of ~ 1300oC in the production of low-phosphorus slag, in order to minimize the cost of dephosphorization of the alloy using existing shop equipment, the refining process can be implemented according to the following scheme and purging the bath with argon, the dephosphorization process scheme may include the following operations: adding 100% pre-briquetted SHUS, to the bottom of the bucket, trans-?orting the bucket to the installation of the oven-bucket, where the optimum temperature will be maintained during refining. This will increase the refining time and, consequently, greater completeness of the refining process .: Key words: highly phosphorous concomitant alloy, slag-forming mixture, ladle furnace, completeness of depho-?phorization.

Features Determining the Melting Temperature of Slag-Forming Mixtures for Steel Continuous Casting

A method for determining the melting temperature of a slag-forming mixture in a high-temperature microscope is described and indices of its accuracy are provided. The main parameters affecting results of determining the melting temperature of slag mixtures using the DSC method, and rational conditions for conducting experiments aimed at determining the liquefaction, melting, and slag spreading temperature are given.

Physical simulation of liquid steel motion in a thin-slab continuous caster mold

Industrial experience of steel casting at the thin-slab continuous caster (CC) revealed processes, having negative effect on the quality of internal structure and surface of CC thin slab. The main problems are as follows: flat streams of liquid steel, flowing through submerged snorkel into restricted dead volume, form circulating flows of extremely high velocity in both liquid core and on the slab surface. This circumstance makes specific requirements to the design and parameters of the submerged snorkel to supply the metal into the thin-slab CC mold. Despite the more than 25 years’ experience of the snorkel form and geometric parameters development, there is no single opinion on its optimal design. Results of physical simulation of the liquid motion processes in a thinslab Caster mold presented (for slab maximum width 1800 mm, thickness – 90 mm) of JSC “Vyksa Steel-works” casting and rolling complex. Description of the physical model facility quoted, as well as description of the experiment methodology and its results. The speed was measured and structure of liquid steel flows revealed in depth and sub-surface layers, as well as in slag-forming mixture at the mold surface. The comparison of two principally different variants of liquid steel feeding into the mold made. The two variants were as follows: by a flat down-directed stream with a narrow central divider (direct-flow submerged snorkel) and by four streams , two of them directed down under an angle relating the vertical axe, and the other (about 20% of total liquid consumption) – directed upward to the bath mirror (the snorkel of “hammer” type). It was determined, that steel casting with technological speed through the direct-flow snorkel was most effective into the slab of 1400 mm width and less, since in this case the sub-surface flows speed did not resulted in the intensive waves formation, constant whirls formation and slag particles dragging into deep layers of the slab. For steel casting into slab of width more than 1400 mm, it is reasonable to use a snorkel of the “hammer” type, which enables to create a favorable stable structure of circulation and decrease the tendency of slag particles dragging in the deep layers of the slab.