Continuous Casting Machine Research Articles

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.

Defect “steel-melting captivity and swelling” on the inner surface of seamless hot-rolled pipes. Characteristic genetic features, the causes of formation and measures of prevention.

In a market economy, increasing the competitiveness of steel products is an urgent trend in science and practice. Development of production of new pipe steels in terms of pipe-rolling plant open joint-stock company «BSW – management company of holding «Belarusian metallurgical company» casted on continuous casting machine, was complicated by the emergence of low-alloy pipe steel grades of internal defects, which negatively affects the quality of the pipes. Visual evaluation of samples on the inner surface revealed rolled defects significant clusters, close to each other, having a longitudinal orientation. The edges of the defects are tortuous, torn. Defects found on the inner surface of the pipes are characterized as steel melting captivity and swelling. The reason for the formation of internal defects of hot rolled pipes «steel-melting captivity and swelling» was the rolling of defects in the macrostructure of the central zone (central porosity and axial liquation) of a continuously cast workpiece with a diameter of 200 mm.

Assessment of units’ performance of CCM technological line

To assess operational reliability of technological units of continuous casting machine (CCM), quantitative indicator of efficiency has been applied. This indicator of efficiency describes ability of technical product to perform work assigned to it with a certain probability, or expectancy that this amount of work will be performed. This indicator is interesting for its optimal value, which being surpassed decreases machine ability to perform the necessary amount of work. Thus, the optimum point of machine operating time limits rational time portion of its use without repair with maximum efficiency. Workability of CCM as technological line as well as operability of its units was evaluated using statistical material obtained during the 15 years of operation of billet CCM. So, all units were divided into three essentially different groups according to conditions of their appointment, i.e. a group of units working with liquid metal, a group of units working with solidifying metal and a group of units working with solidified metal. Performance of each group of units is estimated in absolute and relative values. When assessing performance of CCM units in absolute values, units operating with liquid metal have the greatest performance. Its rational service life from repair to repair is 270 hours with reliability of 0.51. The smallest efficiency was manifested in units working with solidified metal. Its performance lasts 150 hours with reliability of 0.6. Average efficiency in relative units of all groups of aggregates is almost the same, which makes it possible to use this indicator at an early stage of assessing efficiency of both machine units and CCM as a whole.

Digital twin-driven 3D visualization monitoring and traceability system for general parts in continuous casting machine

There are lots of general parts with frequent maintenance and high interchangeability for continuous casting machine during its operation and maintenance. To acquire the service information of each general part under the environment of high temperature and serious oil pollution for predicting remaining life and preventative maintenance, a digital twin-driven monitoring and traceability system for general parts in continuous casting machine is proposed. First, the systematic architecture of proposed approach is given in detail, where a typical five-layer model for digital twin-driven monitoring and traceability is established. Second, the Web-based 3D visualization monitoring for continuous casting machine is achieved by using lightweight 3D twin model. After that, an assembly model based on polychromatic sets is built for expressing and describing the assembly relationships and assembly process of general parts. Meanwhile, an encoding rule for part and position is put forward by considering assembly position information. On the basis of that, the general parts with total process information are traced in the service life cycle. Finally, digital twin-based 3D visualization monitoring and traceability prototype system is developed and implemented, where the experiment cases verify the effectiveness and feasibility of the proposed approach.

Computational experiment on determination of load on the rollers of continuous casting machine

The article is devoted to calculations of load on rollers of a curvilinear continuous casting machine during bending of the ingot in the levelling section. The calculation takes into account the elastic and plastic characteristics of metal and the flexibility of the roller apparatus. Determination of load on rollers together with meeting other requirements such as reducing the cooling water consumption, minimizing the energy consumption enables optimizing the technology of slab cooling in the secondary cooling zone (SCZ) and obtaining metal of the required quality.

Investigation of internal defects formation reasons in copper billet obtained at rotary continuous casting machine (CCM)

A physical model has been created that simulates the cross section of a continuous casted trapezoidal copper billet. The results of physical modeling of continuously cast copper billets solidification process are presented. The features of the trapezoidal continuously casted copper billet crystal structure formation during the casting of metal on a rotary caster are shown. During physical modeling, it was found that the solidification mechanism of the model substance in the study of the formation of the crystalline structure of the copper trapezoidal billet has significant differences from the "classical" crystallization mechanism, in which the crystals grow parallel to each other. The main feature of the copper billet crystal structure formation is that in most cases dendrites growth direction is chaotic relative to the surface of the heat flow, and the growth rates of individual crystals differ by 25–35 %. In this case, the development of nearby crystals ceases due to a collision with the secondary branches of more intensively developing dendrites. It was also established during the modeling process that during crystallization of the melt according to the described above mechanism, a collision of the most intensively developing crystals growing on neighboring faces is possible, in which the closing main axes of the dendrites separate part of the liquid phase from the total volume. This isolated volume of the liquid phase cannot be feed by the melt from the axial part of the billet. The shrinkage of such areas during solidification is the reason for the formation of pores inside the billet. The disordered arrangement of internal pores in the cross section of a trapezoidal copper billet is explained by the randomness of the dendritic crystals growth directions and of the difference in their growth rates.

Исследование на физической модели влияния величины угла раскрытия выпускных отверстий погружных стаканов на характер истечения стали в кристаллизаторе машины непрерывного литья заготовок (МНЛЗ)

Исследование на физической модели влияния величины угла раскрытия выпускных отверстий погружных стаканов на характер истечения стали в кристаллизаторе машины непрерывного литья заготовок (МНЛЗ)

Calculation of temperature balance of aluminum strip obtained at casting and rolling unit

The calculation of the temperature balance of obtaining the aluminum strip at the casting and rolling unit in the area from mould of the continuous casting machine to the pendulum rolling mill.

Mold-level prediction based on long short-term memory model and multi-mode decomposition with mutual information entropy

The mold is referred to as the heart of the continuous casting machine. Mold-level control is one of the keys to ensuring the quality of a high-efficiency continuous casting slab. This article addresses the failure of the mold-level prediction model in the actual production process to overcome the impact of noise. To improve the accuracy of mold-level prediction, a novel method for mold-level prediction based on the multi-mode decomposition method and the long short-term memory model is proposed. First, empirical mode decomposition of the mold-level data is performed. The actual eigenmode component number K is obtained through the calculation of the mutual information entropy of the eigenmode components. Then, we perform a K-based variational mode decomposition on the mold-level data. The noise dominant component is denoised by the calculation of the mutual information entropy of the eigenmode components. Moreover, the long short-term memory model is used to predict the noise dominant component and the information dominant component after denoising. Finally, the predicted result is subjected to variational mode decomposition reconstruction to obtain the predicted mold-level data. The experimental results show that compared with the other methods tested, the model has better prediction efficiency, prediction accuracy, and generalization ability. It provides a new idea for mold-liquid-level prediction and continuous casting blank quality assurance.

Improvement in Castability of Al-Killed Steel in Billet Casters by Process Optimization

Sticking of alumina as well as spinel inclusions inside the sub-entry nozzles as well as tundish nozzle is a perennial problem during continuous casting of aluminum-killed steel through billet casters. This results in restriction or complete blockage of flow of liquid steel through the nozzles eventually leading to abortion of sequence in billet casters and stopping of continuous casting machine. Nozzle clogging not only restricts the productivity by restraining the casting sequence, intermittent extrication of clogged alumina particles or dislodged refractory materials which are a significant source of non-metallic macro-inclusions in the cast sections of billet casters. If these inclusions are not removed completely during secondary refining of steel, they cause excessive clogging mainly in low-carbon Al-killed steels. In other grades of Al-killed steel, clogging is also very prominent if the deoxidation and secondary refining is not carried out properly. IISCO Steel Plant (ISP), Burnpur, a new, modernized unit of Steel Authority of India Limited, was facing problems of nozzle clogging in low-carbon, low-Si, Al-killed grade (EWNR—electrode quality grade) resulting in premature abortion of casting sequence leading to huge productivity loss. To solve the problem of nozzle clogging in low-carbon Al-killed grades and other grades at ISP, optimization of various steelmaking parameters, viz., amount of Al addition and its sequence, purging regime in ladle furnace, optimization of Ca treatment process, etc. has been carried out which has resulted in improvement in castability of Al-killed steel in billet caster of ISP.

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.

Optimization of the Gap Parameters of Supporting Rollers of Curvilinear Continuous Casting Machine

A study was performed to determine the influence of technological and design parameters of continuous casting of steel on reducing the thickness of the billet along the technological line of a curvilinear continuous casting machine (CCM) designed by Uralmashzavod OJSC. The effect of carbon content and casting speed on linear shrinkage through the billet’s thickness was investigated. It was established that in all cases there was a discrepancy between the thickness of the billet and the settings used for CCM rollers. This discrepancy can lead to defects in the billet caused by the distortion of its shape (owing to the blow-up under the action of ferrostatic pressure) and to an increase in friction and, accordingly, pulling forces. On the basis of the obtained results, new settings for the rollers on the hard and hydraulic sections were proposed. The use of recommended parameters considerably reduces the discrepancy between the thickness of the billet and the gap of the rollers, which will improve product quality.

Design and calculation methods for refractory equipment varietal CCM tundish

The article discusses the equipment, installed in the casting chamber tundish of continuous casting machines (CCM). Improving the equipment provides an effective formation of the metal flows and creates conditions for the improvement of its quality. In work are considered the questions connected to an estimation of serviceability of partitions and thresholds of intermediate ladles of the CCM. As criteria of serviceability of these devices were accepted: durability, absence cavitations, and condition on which the speed of steel on border undressed metal -slag should be less admitted. Dependences for account of forces, working on the device, and speeds of movement of steel on border undressed metal - slag were received analytically on the basis of known expressions of the mechanics of a liquid both gas. Ill. 5 Ref. 18.

Industrial mastering the technology of surfacing of continuous casting machine rolls

It has been established that differentiated approach to the choice of surface layer design, materials, technology, and equipment for surfacing makes it possible to increase the efficiency of the continuous casting machine rolls (CCMR) reconditioning. This involves the selection of the materials for surfacing of the rolls depending on their position in the secondary cooling zone, the intensity of wear, and thermomechanical fatigue cracking of surface layer. It has been shown that the breaks in the continuity of the surface layer formed from separated weld beads with gaps between adjacent welds results in the increase of the cracking resistance of the rolls without changing the chemical composition of the surface layer. Developing the continuous casting machine rolls surfacing technology, one should take into account that the optimum ratio of weld bead width to the diameter of the roll depends on the angle of inclination of the weld bead to the generatrix of the cylinder. The recommended limits of the angle of inclination changes have been identified and it has been shown that for each value of the angle there is a certain ratio of the weld bead width to the diameter of the roll; the ratio being independent of the diameter. The schemes of surfacing of the continuous casting machine rolls proposed and mastered in industrial conditions provide a differentiated approach to the choice of the weld bead width, the gap between them, and the angle of bead inclination in multiple directions from the middle of the barrel to the edges. To implement the proposed schemes of surfacing, a functional control system of surfacing installation has been developed. Fitting the control system with limit switches provides the given angle of the weld deposition pass to the generatrix

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.

Development of a Steel Temperature Prediction Model in a Steel Ladle and Tundish in a Casting and Rolling Complex

The paper presents a prediction model for steel temperature in a specified time interval during its overheating over a liquidus point in the tundish of a continuous casting machine (CCM). This depends on the last temperature measurement in a ladle prior to casting with consideration to the ladle’s history and treatment during secondary metallurgical processes in an casting and rolling complex (CRC). The prediction of steel superheat temperature at CRC is based on two modeling stages: the first stage integrates two approaches—a machine-learning algorithm and a probabilistic-graphical model (PGM and Bayesian networks); and the second stage uses a method for evaluating probability distributions. The first approach gives a point estimate of the intermediate and final temperatures of specific heat. The PGM-approach is useful for scenarios with uncertain input data, which is often the case for metallurgical enterprises. The accuracy level in predicting the temperature of the metal in the tundish at the first stage reached 6.0°C. At the second stage, the model integration into the process control system improved prediction accuracy, as well as provided technological parameter control in real time. The model is used as an advisor (master) for the technical team of the ladle furnace and vacuum degasser.

Numerical Simulation of Metal Filling into a CCM Mold Equipped with a Deflector

The study of molten metal flow to the mold of a continuous casting machine (CCM) is still considered to be a complex and imperfect process. This paper is one of the author’s publication series that focuses on the theoretical possibility on the motion kinetics of a liquid metal and heat fluxes in a mold under traditional casting based on: hydrodynamic theory, mathematical physics equations, and an approved numerical approach. This well-known calculation methodology makes it possible to calculate the fluxes of liquid metal motions and their temperature in the mold for the proposed method and for other methods of supplying the metal, as well as to compare the results between each other. The formulation and solution of a three-dimensional problem for determining the velocity and temperature fields in a metal supplied to a CCM mold from a submerged nozzle to a round deflector is discussed. This calculation methodology is based on a system of constitutive equations, a numerical method, a numerical scheme, and an algorithm for solving the problem. According to calculations, the hardened metal crust growing on the faces of the mold has been neglected. If traditional and proposed methods are used to objectively analyze the results and solve the problem, the same theoretical (the velocity of drawing from the mold) and the geometric parameters of a rectangular mold are taken. A patent for describing this alternative method of liquid metal supplying to a rectangular mold has been registered (No. 2018108974/02 (013808)). Some results of the numerical solution of the problem are presented, namely, schemes of liquid metal flows and the temperature thereof in various sections of the mold.

A Hybrid MIP–CP Approach to Multistage Scheduling Problem in Continuous Casting and Hot-Rolling Processes

This paper studies a new scheduling problem in a steel plant, referring to continuous casting (CC), reheating furnace, and hot rolling (HR) processes, which is meaningful and important to the production efficiency and energy saving. First, the problem is modeled as a combination of two coupled subproblems: one assigns casts to continuous casting (CC) machines, decides sequence and start time for casts and rolling units; and another assigns furnaces and decides start time for rolling slabs in a reheating furnace. The objectives are to maximize the number of slabs processed in a mode of hot charge rolling or direct hot charge rolling so as to reduce the energy requirement and the temperature drop of slabs and minimize the residence time of slabs in a reheating furnace to save energy. Then, based on a Benders decomposition strategy, a hybrid algorithm that combines mixed-integer programming and constraint programming is designed to solve each subproblem. An effective cut-generation scheme based on a priority relationship is developed for resolving resource conflicts and unsatisfied setup time constraints. Finally, extensive experiments are conducted to verify the effectiveness of the proposed approach. Note to Practitioners —This paper deals with a scheduling problem arising from CC to HR process in steel manufacturing. It decomposes the original problem into a CC–HR scheduling problem and a reheating furnace scheduling problem. Previously, such a problem is handled, respectively, which always cause energy waste and mismatching plan. This paper takes complex technology constraints into full account to minimize energy waste and energy requirement and establishes nonlinear mathematical models for studied problems. Then, it designs a hybrid algorithm combined mixed-integer programming and constraint programming. The results demonstrate that the proposed approach can solve them effectively. The obtained solution gives decision makers some desired reference to determine a right schedule when actual production tasks are executed.