Intermediate Ladle Research Articles

Thermal chemical erosion behavior of the burning-free Al2O3–C–Si bottom nozzle

Burning-free Al2O3–C–Si bottom nozzle, a key refractory component connecting the intermediate ladle slide to the immersion spout, is always prone to failure under the extreme environment of repeated exposure to chemical attack and thermal shock of the steel. Here, an approach of adding Si powder and the change in Al2O3 aggregate aims to enhance the product's quality and performance of the burning-free Al2O3–C–Si bottom nozzle. And the different composition ratios effects on the chemical erosion behavior of the burning-free Al2O3–C–Si bottom nozzle were investigated based on the measured instantaneous thermal-expansion coefficient and young's modulus of the bottom nozzle materials in the high-temperature range of 300–1473 K. Moreover, the high-temperature folding resistance, thermal-shock resistance test and slag resistance experiments have also been probed. Obtained results reveal that the absence of 6 wt.% Si can promote the formation of SiC phases in the form of flakes and whiskers inside the bottom nozzles, which significantly improves the density, strength, thermal shock resistance and slag erosion resistance of refractory materials. Compared with the bauxite-Al sample, the slab corundum-Si-Al sample reduced the porosity by 7.8% and the erosion index decreased by 4.7% due to the formation of SiC and a thin protective layer of SiO2, as well as the mullite crystals structure. Here, an optimized bottom nozzle with a composite structure has also been proposed. This work can make significant contribution to improve the performance of burning-free refractory materials, bottom nozzles and reducing costs.

Effect of magnesium treatment on microstructure and property of H13 die steel during EAF-LF-VD-CC steelmaking process

Due to the advantages of Mg on inclusions and carbides in H13 steel, Mg wire was added into industrial ladle after VD process to replace traditional Ca treatment in this paper, which is of great significance for industrial production of H13 steel. This paper focuses on the effects of Mg treatment and traditional Ca treatment on the inclusions, carbides, microstructure and mechanical properties in H13 steel. The results show that feeding Mg wire during EAF→ LF→ VD → CC steelmaking process can ensure the submerged nozzle not being blocked under the condition of continuous casting 15 heats of steel ladle, which means feeding Ca wire can be replaced with Mg wire from the aspect of steelmaking production. The primary carbides in Mg treatment steel are mainly precipitated with MgO or MgAl2O4 as the cores and small in size, while the primary carbides in Ca treatment steel are almost large-size carbides without core. The samples taken from the intermediate ladle show that the primary carbide types are all V-rich, Mo-rich and V–Mo-rich composite, and the size of primary carbides in Mg treatment steel is much smaller than that in Ca treatment steel. Adding Mg is helpful to improve the equiaxed crystal rate of continuous casting ingot. The annealed hot rolling samples show that Mg treatment could interrupt the M23C6 (M = Cr, Fe) chain carbides distributed along the grain boundary. The impact test shows that the dimple fracture surface become small and deep after adding Mg, which improves impact toughness significantly.

Interrelation of CCM (Steel Billet Continuous Casting Machine) Tube Steel Casting Parameters and Hot-Rolled Plate Quality

The quality of the hot-rolled plate up to 36 mm thick was estimated by the percentage of rolled products, sorted due to the presence of a surface defect "Non-metallic inclusions", and internal defects, detected by ultrasonic plate control. The analysis of the data on the total sorting of hot-rolled plates demonstrated that the amount of sorting differs significantly on the melting from which each series of tubular metal casting commenced, compared to all the other melting in the series. The sorting of the sheets rolled from the metal of the first in a series of melting proved to be 1.9 times higher than that of the metal of all other melts. The main reason (in 68% of cases) of sorting is the presence of non-metallic inclusions on the surface of the plates. The effect of sorting of hot-rolled plates on non-metallic inclusions of various parameters has been studied: the duration of the intermediate ladle-heating; the length of time from the end of the heating of the intermediate ladle, prior to the beginning of the casting; lining temperatures of the intermediate ladle before the beginning of casting; duration of filling the intermediate ladle; the filling rate of the intermediate ladle with metal; mass of metal in the intermediate ladle before the beginning of casting into the crystallizer; chemical composition of metal; overheating of the metal over the liquidus point at the beginning, middle and end of the casting. On the sorting of flat products for non-metallic inclusions, of all the parameters considered, a statistically significant effect is due only to the overheating of the metal above the liquidus point, which varies in the range from 19 to 35 ° C. In order to obtain an acceptable quality of both the surface of slabs and the surface of hot-rolled plates for non-metallic inclusions, the first in a series of melts recommends overheating of the metal in the intermediate ladle above the liquidus temperature of 30-35 ° C.

Selection of refractory concrete for batching nozzles of an intermediate ladle of continuous casting machine

The paper presents experimental research on selection of refractory concrete for the glass dosing promove in continuous casting of steel. In the experiments we consider three types of refractory concrete determined by their basic thermal properties using standard methods and the selected refractory concrete with the best performance. The batcher glass was manufactured and tested in production conditions, which showed good results in continuous casting of steel.

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.

Increasing efficiency of rail steel refining in CCM tundish based on rational organization of hydrodynamic processes

Quality and operational properties of rails determine duration of their operational service. The main parameters that determine quality of steel are chemical heterogeneity and presence of non-metallic inclusions in metal. Efficiency of homogenization of metal melt and its refining from non-metallic inclusions in tundish is largely determined by organization of hydrodynamic processes, internal geometry of ladle, and presence of additional refractory elements. Using physical and mathematical modeling, study of the influence of additional refractory elements of various configurations of intermediate ladle on processes of melt flow was carried out. Physical modeling of hydrodynamic processes in the tundish taking into account requirements of similarity theory was made on specially created laboratory-experimental complex. Numerical experiments were carried out using computational fluid dynamics methods (finite volumes) on three-dimensional turbulent mathematical model with a singlephase representation of metal melt flow in tundish. To evaluate efficiency of melt homogenization according to results of physical and mathematical modeling, new technique has been developed based on analysis of distribution of time of liquid placement in continuous flow reactor. According to the results of experiments, configuration of the internal volume of tundish of four-strand CCM is proposed. A construction is considered that provides effective homogenization of molten rail steel and its refining from non-metallic inclusions. The design of full-profile compartments was developed and tested under industrial conditions, which ensure rational organization of melt flows, its homogenization and efficient refining of rail steel from non-metallic inclusions in the tundish. Industrial research was carried out under the conditions of four-strand CCM No. 1 of EAF shop at JSC “EVRAZ ZSMK”.

MATHEMATICAL MODELING OF THE DISTRIBUTION OF ARGON IN A TUNDISH WITH A MOLTEN METAL DURING FILLING

The article is devoted to the mathematical description of the process of filling an intermediate ladle (tundish) with argon, which is blown into the melt stream falling from the steel casting ladle, which is common at metallurgical plants. Metallurgical plants use an intermediate ladle to reliably supply a continuous casting machine for the melt. Also important for the tundish is the removal of non-metallic inclusions using argon. The good distribution of argon bubbles in the tundish significantly influences the removal of unwanted melt components such as hydrogen and nitrogen. Given the need for gas to escape, the melt speed in the intermediate ladle should be sufficiently low, especially near outflow holes, where melt needs to be homogeneous and slow for a high–quality casting. Conducting experiments during the operation of a metallurgical plant is undesirable, costly and is accompanied by difficulties associated with high temperature and opacity of the melt. Therefore, the experiments are often carried out in laboratories on the so-called cold models, where the melt is replaced by water, argon – by air, and the tundish – by the transparent container of the rectangular shape under the conditions of similarity. Despite the obvious advantages of such cold modeling, today most experiments are still conducted on mathematical models, which are a much cheaper and low-erroneous way of predicting the development of a given process under different conditions. Mathematical modeling of melt motion helps to select the optimal geometry of the tundish, as well as the required amount of argon and usefulness of barriers on a way of melt streams. The article proposes to use the convection-diffusion equation for the argon field and the Navier-Stokes equations – for the velocity field. The numerical solution using finite volume method is well tested and provides sufficient accuracy. In addition, this method is easily parallelized to speed up computing on modern multi-core processors. A graphical user interface software application allows you to display the status of the system on the screen for further review and adoption decisions.

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 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.

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.

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.

Development and implementation of an innovative metal receiver for the intermediate ladles of caster slab

The features of the working conditions of intermediate ladles of caster slab are considered on the example of the 27-ton units of the oxygen-converter workshop of PJSC «Severstal». The results of mathematical modeling of hydrodynamics in an intermediate ladle with different turbulence dampers of the incoming jet are given. Designed, patented and implemented metal receiver (brand REYNSTREAM / REINSTREAM®) with a wave-like inner surface, designed to improve the quality of continuously cast billets, as well as providing increased stability and processability of the continuous casting process through a special design.. Ill. 6. Ref. 7.

Development of technology for lining steel-tapping hole of steel-teeming ladles with the use of nesting well blocks

At OJSC «BSW – Management Company of Holding «BMC» were tested nesting well blocks for lining of steel-tapping hole of steel-teeming ladles ЭСПЦ-1, 2 with the working lining of piece goods. In the conditions of the enterprise during the full campaign of the working lining of steel ladles, intermediate repair of the slag belt, bottom blowing units and the steel-tapping holes is carried out. The steel-tapping hole is used to release steel from the steel ladle into the intermediate ladle. The purpose of the tests is to replace the «traditional» filling of the steel outlet with refractory concrete manually by molded nesting wellblocks due to the reduced risk of accident due to the lack of probability of metal «penetration» into the concrete, as well as reducing the volume and duration of repair of the working lining of steel ladles.

The combination of the steel teeming process and the refractory outfit design of the billet caster's pouring ladle‒intermediate ladle system

The refractory outft of the steel-teeming ladle (STL)‒ metal jet (MJ)‒intermediate ladle (IL) was regarded in the article for the billet continuous casters (CCM). The metal flow management was investigated for this system. The peculiarities of the CCM element's design were noticed which provided the efcient flow of the teeming metal in the STK‒MJ‒CCM system. This investigation enabled both the successful steel flow formation in the receiving chamber (RC) of the billet CCM and the improvement of the metal quality while the amount of the discarded continuous steel cast billets got down.Ill.4. Ref. 20.

Physical modeling of the processes of metal melt movement during continuous casting

Studies of hydrodynamic processes in the intermediate ladle of a continuous casting machine by methods of physical low-temperature modeling was carried out. A qualitative and quantitative evaluation of efficiency of the use of various hydrodynamic elements is made using the method of studying the distribution of the liquid residence time in the unit.

Improvement of the metal casting process and refractory equipment design in the intermediate ladle ‒ open jet ‒ the continuous billet caster mold's installation

The steel flow and refractory arrangement of the intermediate ladle (IL) ‒ open jet (OJ) ‒ continuous casting machine (CCM) mold's installation are regarded in the article. The specifics of the metal flow controlling are mentioned. The structural features of the continuous billet caster which maintain the effective metal flowing through the IL ‒ OJ ‒ CCM mold installation are presented. The improving of the installation design allows the expedient metal flows and provides the billets' quality upgrading.

Choice of Refractory Filler for Preparing Concrete Partitions of a CBCM Intermediate Ladle

The possibility is considered of preparing intermediate ladle concrete partitions using cheap materials. It is shown that in order to prepare high quality concrete refractory materials capable of slow hydration are considerably important. In addition, it is necessary to use metallurgical production waste considerably cheapening refractory objects.

Mathematical Modeling of the Movement of Moisture in Refractory Concrete and Gunning Bodies During Drying

Amathematical model of the movement of moisture in refractory water-sealed materials of different densities where there is an external temperature field present is constructed. The Fourier thermal conductivity equations, Fick’s diffusion equation, and the method of finite elements are used to solve the problem. The diffusion coefficients of water in the test materials are determined by means of laboratory tests from the loss of mass in the course of drying of the samples. Features typical of the movement of moisture in refractory concrete for the case of deposition on cold and hot surfaces are determined as a result of a subsequent computational experiment, using as examples the casting bottom of a casting ladle and guniting of an intermediate ladle.

THE DESIGN ENGINEERING OF THE REFRACTORY COMPONENTS FOR THE STEEL REFINING UNDER THE CONTINUOUS CASTING

Hydrodynamic processes have been mathematically and physically modeled for the EVRAZ WestSiberian Metallurgical Complex' 4-strand bloom CCM's intermediate ladle. The physical model of the intermediate ladle was used to evaluate qualitatively the melt stirring operation. The metal impurities purification efficiency was quantitatively estimated for the intermediate ladle when using the refractory elements of various shapes. The recommendations were elaborated for the intermediate ladle's refractory partitions parameters. Ill. 9. Ref. 9.

USE OF OWN WASTE METAL IN THE PRODUCTION OF SINGLE-CRYSTAL PERMANENT MAGNETS

The applicability of waste metal formed in the manufacture of single-crystal permanent magnets of UNDKT5AA alloy is studied. Since this waste accumulates detrimental impurities, it cannot be re-used in the production. Additional cleaning of initial melting stock with solid oxidants was applied to prevent alloy contamination with impurities. An example was provided for calculating a required solid oxidant volume. The material of graphite intermediate ladle in contact with melt was replaced with pure alumina. Waste metal formed afterwards featured a reduced content of detrimental impurities. Such waste materials were used as a melting stock component in the production of single-crystal permanent magnets. All magnets met quality requirements, while the cost of production dropped by more than 30 %.