Steel-pouring Ladles Research Articles

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.

TOTAL OXYGEN CONTENT IN LIQUID STEEL AS A CRITERION FOR EVALUATING NONMETALLIC INCLUSIONS IN PIPE STEELS

A statistical analysis of the total oxygen content in samples of pipe steels at the stage of continuous casting at the continuous-casting machines of the casting and rolling complex of JSC “Vyksa Metallurgical Plant” was carried out. The microstructures of rolled samples were studied, and the chemical composition of non-metallic inclusions was determined by X-ray spectral microanalysis. A laboratory analysis of liquid steel samples and hot-rolled steel products of the casting and rolling complex was carried out using the method of reduction melting in an inert gas flow. Relationships have been constructed between the duration of metal presence in a steel-pouring ladle and the magnesium content in non-metallic inclusions, as well as between the average score of non-metallic inclusions in rolled metal and the total oxygen content in liquid steel at the stage of continuous steel casting.

Features of the fracture of refractory linings depending on the size of equipment

Using computer simulation, we studied the influence of the size factor on cracking in refractory linings by the example of steel-pouring ladles of ferrous metallurgy. The stress-strain state of the linings was analyzed at the macroscopic scale without taking into account their discrete structure (individual bricks) and the microstructure of the refractory material. We revealed that the maximum thermally and mechanically induced stresses in the linings are confined to certain regions associated with the design features of the equipment. Due to the distribution of mechanical loads and heat transfer features that regions become macroscopic stress concentrators. However, for small equipment size, these maxima are not sufficiently pronounced, and the stress fields formed by different stress concentrators overlap. Apparently, this is the reason for the relatively chaotic arrangement of cracks in the lining. In large equipment, the stress fields of «construction conditioned» concentrators do not overlap due to the large distance between them. The stresses in these concentrators exceed the background values in the surrounding regions of the lining by an order of magnitude or more. This determines the high probability of the formation of a characteristic fracture pattern with cracking in the vicinity of «construction conditioned» stress concentrators.

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.

Improved Manipulator for Maintenance of the Cassette Gates of Steel-Pouring Ladles

Improved Manipulator for Maintenance of the Cassette Gates of Steel-Pouring Ladles

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.

Simulating Interaction of Liquid Steel with Gate Wall at Harmonic Motion

The problem of determining the forces of interaction of a viscous fluid with the cylindrical pipe wall is considered. It is assumed that near the pipe wall, the fluid motion is completely determined by viscous forces. The pipe moves along the streamline. The annular fluid element motion law is a special case of the Navier–Stokes equation in a cylindrical coordinate system. The equation is solved by the Fourier method in Bessel functions. Considering the orthogonality of the eigenfunctions, an equation for the squared norm is found. As an example, the case is considered when the pipe is subjected to vibration. Equations have been obtained for the velocities and viscous friction forces in the laminar sublayer. It has been found that when the pipe moves harmonically, the velocities and shear stresses at the pipe wall do not reach their maximum synchronously. The distribution of velocities and stresses in the section of the steel-pouring ladle gate channel has been considered for three vibration modes. The solution provided can be, in particular, used to determine the fluid–pipe wall interaction forces when the pipe is technologically affected by vibration, impulse, etc., as well as study moving joints such as piston, plunger, etc.

Дослідження термічної підготовки ковшів

The purpose of the work is to develop a computer model of ladle heating with an open torch on a drying and high-temperature heating installation to control the thermal preparation process. The task of managing ladle drying and high-temperature heating installations (USVR) is to implement their operating modes, which ensure obtaining the specified temperature profile of the lining layers of steel castings with minimal fuel consumption. The task of controlling by drying and high-temperature heating unit (SHHS) is to implement their operating modes that provide a given temperature profile of steel pouring ladle lining layers with minimal fuel consumption. Since modern technical means of control do not allow obtaining relevant information about the temperature field of the lining of the walls and bottom of the ladle, it is necessary to create a predictive model of its heating by an open torch at the SHHS. A 68-ton rammed steel-pouring ladle KС-68 was chosen as the object of study. According to the research data, the shape and dimensions of the open torch were evaluated at OCC PrJSC “Evraz- Dnipro Metallurgical Plant”. A digital camera recorded the torch at the burner outlet at a natural gas flow rate of 50 m3/h, which corresponds to the standard mode of drying and warming up the ladle. For modeling purposes, the resulting torch shape was approximated by two truncated cones. Determination of the parameters of convective-radiant heat transfer in the “torch – cover – wall – ladle bottom” system was carried out taking into account the temperature of the torch, the thermophysical properties of the lining materials, as well as the irradiance coefficients and the emissivity of the surfaces. The calculation of the temperature field in the lining of the wall and bottom of the ladle was carried out by the finite element method implemented in the ANSYS package. Based on the simulation, a change in the temperature field of the ladle lining was obtained during its heating at the SHHS with an open torch for 6 hours, which corresponds to the current technology. An analysis of the dynamics of the temperature field of the ladle lining obtained as a result of modeling indicates that when it is heated by an open torch at a drying and high-temperature heating unit, thermal stresses do not occur, which are dangerous from the point of view of cracking in the layers of refractory materials. The maximum temperature gradient in the wall is 10 °С/mm, and at the bottom – 6 °С/mm. It has been established that the working surface of the lining warms up sufficiently to avoid thermal shock when steel is poured into the ladle. The results of the research can be useful for optimizing the process of thermal preparing steel pouring ladles.

Improvement of the technology for railway wheel steel vacuum processing

The analysis of data on the production of wheel steel grades “2” and “T” according to GOST 10791-2011 in the conditions of the of the electric furnace shop of Ural Steel JSC is presented. The content of hydrogen and nitrogen is significantly less than the regulated ones on most heats, which indicates an irrational vacuum mode. Such modes lead to an increase in energy costs for redistribution. All this testifies to the available reserves for improving the vacuum technology. As a result of research, it has been determined that in order to guarantee the production of hydrogen content less than 1.5 ppm and nitrogen up to 0.007 %, it is necessary to carry out vacuum treatment of steel at a residual pressure in a vacuum chamber of up to 3 mbar, the duration of processing in a high vacuum is at least 20 minutes, and argon consumption is blowdown not less than 0.05 m3/t, metal overheating from 110 to 130 °С. The overheating range of the steel before the start of the vacuum treatment the optimal temperature conditions for casting the steel. The optimum temperature of metal overheating at the beginning of processing on steel degassing installation is ~ 115-125 °C with a duration of vacuum treatment of 50-55 minutes (loss of metal temperature 70-75 °C), with overheating of the metal in a steel-pouring ladle before the start of casting 35-45 °C and at loss of metal temperature during transportation to casting 5 °C (15 min). Regression equations are obtained that allow predicting the results of degassing, as well as selecting the values of the vacuum treatment parameters in order to achieve a given content of dissolved gases – hydrogen ([H], ppm) and nitrogen ([N], %).The research was conducted under financial support of the RF Ministry on Science and Higher Education (PROJECT No. FZRU-2020-0011).

Mathematical statistics for measurement of steel temperature in steel-pouring ladle and tundish at steel continuous casting

The article considers the temperature distribution in steel during its continuous casting. Temperatures were measured sequentially in the steelpouring ladle (one measurement) and in the tundish (two measurements) using a platinum-platinum-rhodium thermocouple with an accuracy of ±4 °C. We have analyzed the results of 170 casts of two steel grades: 5SP and 35GS. The type of temperatures set distribution was verified on the basis of three goodness-of-fit criteria: Pearson’s χ-square criterion, λ Kolmogorov-Smirnov criterion and W Shapiro-Wilk criterion. The results obtained are consistent with the physical picture of steel casting. The metal in steel-pouring ladle is practically in a stable state and is subject only to natural cooling through the lining, top and ladle body. In the variant of analyzing a sample of temperature values in tundish at the first and second measurements, the hypothesis of normal distribution should be rejected. Here, the steel temperature depends on a number of parameters, including the feed rate and casting rate, feed time and composition of slag-forming and heat-insulating mixtures, etc. Attempts to establish the relationship between the steel temperatures of in steel-pouring ladle and tundish were unsuccessful. Considering the temperature measurement in tundish as two sequential data arrays, the first of which is an argument, and the second is a function, a linear relationship between these arrays was established. This relationship between the first and second temperature measurements in the tundish can be used to estimate the steel final temperature at thermocouple readout, including in the event of a failure. The results of the work can be used in development of a mathematical model of steel casting.

Application of the shotcreting method to restore the working layer of the lining of steel-pouring ladles of the oxygen-converter shop of PJSC MMK

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Application of Shotcreting for Restoring the Working Layer of PAO MMK Oxygen-Converter Workshop Steel-Pouring Ladle Lining

A method for shotcreting steel-pouring ladles under PAO MMK oxygen-converter workshop (OCW) conditions is described. Tests are conducted in the period 2018 – 2020. Results of the work performed are identification of operating parameters that affect wear of the working layer of the lining of steel-pouring ladles beneath the shotcrete layer, prospects for maintaining the lining by shotcreting in order to reduce lining working layer wear and as a result increase the life of PAO MMK OCW steel-pouring ladles.

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.

Model Studies and Modernization of a Manipulator for Tapping Spout Replacement in Continuous Steel Casting

We study the operating conditions for the specialized tapping spout used to protect molten steel against secondary oxidation between the steel pouring ladle and the tundish in a continuous billet casting machine. The following are found to be the major factors affecting premature failure of the tapping spout: Localized damage to the tapping spout walls due to installation-related misalignment between the spout and the refractory-lined slide-gate valve, and gradual encrustation of the spout during the pour process, with oxygen lancing subsequently being required to remove the encrustation. The accuracy of spout alignment with the ladle slide gate can be improved by modifying the functional configuration of the manipulator to support self-alignment of the spout to its proper location. The wear on the spout can be reduced by using a pneumatic vibrator to induce vibration, and this has been confirmed by laboratory studies using a model experiment. The proposed modernization of the manipulator will enhance tapping spout operating efficiency by reducing premature tapping spout failures.

Theoretical Bases and Technology of Steel Exhaustive Metal Desulfurization and Direct Microalloying with Boron Beneath Basic Boron-Containing Slags

Results of theoretical and experimental studies of the physicochemical properties of slags of the CaO–SiO2–B2O3 system containing 15% Al2O3 and 8% MgO lie at the basis for the development of technology for exhaustive desulfurization of metal beneath basic boron-containing slags formed in a steelpouring ladle in a ladle-furnace unit (LFU), and steel direct microalloying with boron. Methods of simplex lattice planning of an experiment, a software complex HSC 6.1 Chemistry (Outokumpu), and the method of electro-vibration viscosimetry are used. Results of thermodynamic modeling of the effect of slag basicity and B2O3 content on sulfur and boron equilibrium distribution coefficient between slag of the oxide system under study and low-carbon metal are presented. The quantitative effect of basicity and B2O3 content on slag viscosity containing 15% Al2O3 and 8% MgO at a temperature of 1600°C and the influence of the slag chemical composition of the oxide system under study on the degree of wear of periclase-carbon refractory material are shown. Results of studying physicochemical properties of slags of the CaO–SiO2–B2O3 system containing 15% Al2O3 and 8% MgO are a basis for developing a ladle slag composition with low viscosity and providing exhaustive metal desulfurization, and direct microalloying of boron steel with low corrosive effect on periclase-carbon refractories. Development of this technology provides, depending on the steel grade, a boron content of 0.001–0.008%, low metal sulfur concentration at 0.004–0.014%, a reduction in manganese ferroalloy consumption from 0.5 kg/ton of steel 08KP to 1.4 kg/ton of steel 09G2S, exclusion of ferroboron and fluorspar additives in the ladle, and achievement of good finished metal product mechanical properties.

The effect of the design of the metal receiver slab continuous casting machine on the movement of metal in the intermediate ladle when the metal stream deviates from the desired position. Part I. Formulation of the problem

The article is devoted to assessing the effect of the design of the metal receiver in the intermediate ladle of the large capacity slab continuous casting machine on reducing the turbulence of flows when the metal stream deviates from the required position during casting. The results of computer simulation of industrial variants of displacement of a stream of metal from a steel pouring ladle to an intermediate ladle from the target input point are presented. The distribution of metal flows in the tundish is compared with different designs of metal receivers. Recommendations are given for reducing flow turbulence for the cases considered. Ill. 6. Ref. 5.

The effect of the design of the metal receiver slab CCM on the movement of metal in the intermediate carpet with a deviation of the metal stream from the desired position. Part II Modeling technique

The article is devoted to assessing the influence of the design of a metal receiver in an intermediate ladle of large capacity slab continuous casting machines on reducing turbulence in flows when the metal stream deviates from the required position during casting. The results of computer simulation of industrial variants of displacing a stream of metal from a steel pouring ladle to an intermediate ladle from the target input point are presented. The distribution of metal flows in the tundish is compared with different designs of metal receivers. Recommendations are given for reducing flow turbulence for the cases considered. Ill. 4. Ref. 2.

The effect of the design of the metal receiver slab continuous casting machine on the movement of metal in the intermediate ladle when the metal stream deviates from the desired position. Part III. Research results

The article is devoted to assessing the influence of the design of a metal receiver in an intermediate ladle of large capacity slab continuous casting machines on reducing turbulence in flows when the metal stream deviates from the required position during casting. The results of computer simulation of industrial variants of displacing a stream of metal from a steel pouring ladle to an intermediate ladle from the target input point are presented. The distribution of metal flows in the tundish is compared with different designs of metal receivers. Recommendations are given for reducing flow turbulence for the cases considered. Ill. 5. Ref. 3.

Development of the Metal Temperature Prediction Model for Steel-pouring and Tundish Ladles Used at the Casting and Rolling Complex

A model has been developed for predicting the metal temperature in the specified superheat range above the liquidus temperature inside the tundish of a continuous casting machine (CCM) depending on the last temperature measurement in the steel-pouring ladle (prior to casting), as well as ladle history and secondary steelmaking process under the conditions of the Casting and Rolling Complex (CRC) of the JSC “Vyksa Metallurgical Plant” (VMZ). It is suggested to predict the superheat temperature of steel at the CRC by using statistical models considering the specifics of technological process. During the first stage, the model itself has been developed by integrating the following two approaches: a machinelearning algorithm and probabilistic graphical model (PGM and Bayesian networks). The first approach provides the point estimate of the intermediate and final temperatures of the specific melting, while the second approach allows evaluating the probability distribution. The PGM-approach is very promising in the situations involving missing, incorrect, or undefined input data, which are quite common at the metallurgical plants. During the first stage, the achieved level of accuracy of tundish temperature prediction was 6.0°C. During the second stage, the model was integrated into the shop automated process control system, which allowed increasing the prediction accuracy and ensuring a real-time control of the process parameters. The model is used as a guidance (master) tool for the process personnel operating the ladlefurnace and vacuum degasser equipment.