Continuous Billet Casting Machine Research Articles

Hot-Slab Charging for Energy Conservation in Continuous Furnaces

We considered the thermal operating balance of a continuous furnace being charged with 250 mm-thick cold steel slabs, and perform experimental measurements of the heat loss to the environment. The required heating time and peak productivity of a hot-charged furnace were determined under the assumption that the slabs were fed into the furnace at 700–1250°С. The calculations revealed that the amount of time required to heat the slabs is much shorter, productivity is higher, the amount of heat required per metric ton of metal is smaller, the amount of heat lost to the environment is lower, and the fuel (natural gas) consumption of the furnace per metric ton of metal is much lower. We also obtained a theoretical curve for fuel consumption as a function of charging temperature; according to this curve, as the charge temperature increases from 700 to 1000°C, the specific natural-gas consumption per metric ton of metal decreases from 27.7 m3 /metric ton to 10.3 m3 /metric ton, compared with 62 m3 /metric ton for cold feedstock. We find that the energy savings in heating furnaces is maximized by feeding the slabs in immediately after they come out of the continuous billet casting machine.

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.

Improvement of continuous billet casting machines

Abstract The paper describes disadvantages of known designs of machines and their components, represents new more advanced designs of continuous billet casting machines improving their quality, operational reliability and ease of operation.

Improvement of the Process of Metal Casting and the Design of Refractory Equipment of the “Tundish Ladle – Open Jet – Mold” System of a Continuous Billet-Casting Machine

We consider the process of motion of steel flows and the refractory equipment of the “tundish ladle (TL) – open jet (OJ) –mold” system of a continuous billet-casting machine (CBCM). We indicate the specific features of control over the metal flows in the analyzed system and analyze the specific features of the design of elements of the CBCM guaranteeing the possibility of rational transportation of the cast metal in the TL – OJ – mold system. The improvement of the design guarantees the rational motion of the flows of liquid metal in the mold and creates conditions for the improvement of the quality of billets.

Mathematical Modeling of Cooling of a Continuously Cast Ingot for Reducing Heat Losses

We consider thermal processes running in the course of cooling of a continuously cast ingot in a continuous billet casting machine with regard for the heat of phase transformations. For the solution of the problem of rational utilization of the heat of melts, we propose to improve the technology of continuous casting of steel, which would make it possible to use the heat of the liquid core of an ingot for leveling the temperature field over its cross section and guarantee the minimum losses of the heat at the exit of the continuous billet-casting machine. We develop a mathematical model of cooling of continuously cast ingots in a two-dimensional space representation with regard for the release of the heat of crystallization in the two-phase zone. The numerical realization of the model is performed with the help of the implicit difference scheme of coordinate-wise splitting. The adequacy of the model is checked by analyzing the convergence of the experimental and numerical data according to the Fisher, Student, and Mann–Whitney criteria. In modeling, we simulated the control action in the zone of secondary cooling. It is established that, in the case of application of the control action in this zone, the surface temperature increases by 160°C, while the average mass temperature increases by 100–160°C. We choose criteria for the rational modes of cooling of continuously cast ingots. To preserve the heat content of an ingot, it is proposed to use heat insulation after the zone of water–air cooling. We determine relationships between the parameters affecting the surface temperature of the ingot and represent them in the form of nomograms. It is shown that, before the machine of gas cutting, as a result of heat insulation in the zone of air cooling, the ingot is thermostatted as a result of which the temperature of its most vulnerable zones (corners and surfaces) increases. It is established that, for the rational modes of casting of steels, the ratio of the length of the zone of heat insulation to the total length of the continuous billet casting machine varies within the range 0.3–0.6. To determine the heat losses in the process of subsequent cooling of the ingot in air after leaving the zone of machine gas cutting, according to the existing technology of transportation of slabs to compression, the time of modeling was set equal to 90–105 min. To preserve the heat content of the ingot and level temperatures over its cross section, it is also necessary either to use a thermally insulated transmission roller conveyer or to hold ingots in a thermostat.

Analysis of the Process of Metal Casting and the Structure of Refractory Equipment of the “Tundish Ladle – Submerged Nozzle – Crystallizer” System of a Section CBCM

We consider the refractory equipment of section continuous billet-casting machines (CBCM) of the following system: tundish ladle (TL)–submerged nozzle (SN)–crystallizer, and analyze the processes of control over the metal flows in this system. We indicate the specific features of the structure of elements of section CBCM responsible for the rational transportation of the poured metal in the TL–SN–crystallizer system and the efficient formation of steel flows in the crystallizer and creating conditions for the enhancement of the quality of metal.

Development of a New Horizontal Continuous Casting Machine Construction for Nonferrous and Precious Metal Billets

The work is devoted to development of a new design of horizontal continuous billet casting machine (HCBCM) for non-ferrous and precious metals. The possibility of calculation and design of horizontal casting machine elements by means of computer simulation using the software created is demonstrated. Based on the proposed methods of calculation and design as well as analysis of mathematical modeling results, new designs of HCBCM elements are created that enhance the efficiency of the machine. Appraisal trials of HCBCM structural elements created are performed successfully to measure the effectiveness of this work and introduction into production.

Improving Refractory Constructions in the System “Steel-Pouring Ladle – Pouring Basket” of CBCM

The refractory equipment of the system “steel-pouring ladle – pouring basket” of continuous billet casting machines (CBCM) is considered. Designs of elements of the unit intended for protecting streams of metal in the course of pouring steel are developed. Designs of the unit with the use of inserts made of plastic refractories to prevent passage of air into the metal stream as it is being poured and assure rational parameters of the delivery of argon into the annular groove of the refractory tube are considered. Stability of the pouring process and an increase in the quality of the poured metal are achieved as a result.

Scale levels of damage to the raceway of a spherical roller bearing

The study determines the parameters of defects generated in a roller bearing used in the link of a mould oscillating mechanism that makes part of a continuous billet-casting machine. The evolution of such defects is described from the perspective of scale levels of deformation and fracture. The studied wear behaviour in the bearing corresponds to false brinelling; the raceways suffer the formation of grooves having the bottom with folded morphology. The mechanisms of deformation and wear of the bearing were analysed using multi-level approach, i.e. at macro-level, from the perspective of the mechanics of a deformable rigid body, at meso-level II, implementing tribological approaches, and at meso-level I, using the methods of indentation, three-dimensional profilometry and fractography.

Improvement of Steel Pouring in a Section CBCM

Questions are considered for pouring steel in section continuous billet casting machines (CBCM). Structural elements are developed of a unit for protecting the metal stream during steel pouring in a section CBCM that facilitates a reduction in reaction of air with molten steel during pouring and provides rational argon supply parameters into a refractory pipe annular groove. This makes it possible to increase pouring stability and provide high quality poured metal.

Failure analysis of the hinge-lever mould oscillator bearings of the continuous casting machine

The results are considered of the investigations into the reasons and mechanisms of wear of the hinge-lever tilting mechanism bearings of the continuous billet casting machine mold operating in the rolling motion mode. The types of defects of the outer and inner rings of the bearing are determined, as well as their shape and relative position. The optical and electron- microscopic analysis of the surface of the defect is performed. It is established that the static and dynamic loading parameters have a significant effect on the mechanisms of friction and wear, as well as on the formation of dents in the bearing races. The results obtained allow assessing the reasons for wear of the hinge-lever tilting mechanism bearings, and laying the ground for the development of the technique for their elimination or minimization.

FAILURE ANALYSIS OF CONTINUOUS CASTING ROLLS MATERIAL AND PHYSICAL SIMULATION OF THERMAL FATIGUE LOADING

The experimental method for physical modeling of operating conditions of a continuous billet casting machine (CCM) rolls is developed to estimation the temperature field and especially the temperature at the surface of the roll by measuring the temperature with the thermocouples (fully embedded) at multiple point inside the roll. The physical model allows for the automated recording of the quasi-stationary temperature field in the rolls surface layers and at various distances from its working surface. The main mechanisms of impact failure in the service exposed CCM roll material are investigated at the maximum temperature of the thermal cycle.DOI: http://dx.doi.org/10.5755/j01.mech.19.4.5046

Ingot solidification in a continuous billet casting machine with dynamic pouring regimes

A calculation method is developed for ingot solidification in a continuous billet casting machine (CBCM) with dynamic pouring regimes when there is a change in pouring rate, meniscus level and parameters of liquid metal fed to the mold. The method makes it possible to calculate precisely billet shell thickness and liquid phase length with efficient slab cooling, when the cooling intensity for the ingot surface depends on dwell time of an ingot element in the CBCM, and approximately with cooling used in contemporary CBCM when in the rest of the CBCM zones the cooling intensity is approximately constant over the length.

Computer analysis of surface cracks in structural elements

We propose a method of computer processing of images of cracks. To discern cracks on an image, a segmentation method which includes an analysis of the brightness density function and binary transformation is used. To determine orientations of a crack, we calculate the locus of points of its skeleton with their subsequent approximation by the method of least squares. As a measure of damage, the area of cracks within the boundaries of the analyzed region was used. We investigate images on the surface of a roll of a continuous billet casting machine. By the moment the roll was removed from service, it had been operated in 4500 heats (the weight of which was 350 t). The cause of its removal from service was the cracking of its working surface.

Hydrostatic compaction of refractory articles for continuous billet casting machines

Development of technology and equipment for compaction of refractory articles for a continuous billet casting machine (CBCM) in the Soviet Union and in Russia from the 1960s up to the present day is considered. The main production schemes for compaction and design layouts for compaction equipment (hydrostats) used in the country are given and there is also comparative analysis of compaction processes for refractory components for CBCM used in Russia and abroad.

Determination of efficient conicity of the working walls of the crystallizer of a continuous billet casting machine

A procedure of calculation of efficient conicity of the crystallizer of a continuous billet casting machine is developed. At efficient conicity, close contact of the ingot with the working wall is ensured and heat exchange is intensified over the entire height of the crystallizer. The choice of conicity should be carried out taking into account ingot shrinkage during solidification. In the suggested mathematical model, processes of shrinkage, solidification, and heat exchange are interrelated.

Application of DIAMOLD high-speed casting technology at ISPAT Unimétal

During 1999 and 2000, the six lines of the continuous billet casting machine of ISPAT Unimetal at Gandrange (France) have been equipped with the DIAMOLD moulds developed by VOEST- ALPINE Industrieanlagenbau (VAI). This transformation required no constructional change of the machine and represented only a minimum investment. The new mould technology allows to cast at very high speeds (above 3 m/min) and to comply with all quality requirements for a wide range of steel grades.

Pony ladle nonswirl nozzles for billet continuous casting machines with a small mold cross section

Domestic nonswirl nozzles for pony ladles for pouring of steel without the use of stoppers on continuous billet casting machines with a small mold diameter were developed and introduced for the first time. The domestic nonswirl nozzles are not inferior to the imported ones in life and differ from them in an improved design.

An analysis of the temperature field in the refractory feeder of a horizontal continuous billet casting machine

A mathematical model of the process of formation of the front of solidification of the billet skin in the refractory feeder of a horizontal continuous casting machine taking into consideration possible changes in the geometric and thermophysical parameters of the refractory has been developed.

Rational selection of the refractories for slide gate plates

During teeming in operation of the gate the temperature field changes, but for a long time the temperature gradient changes but exceeds the limiting value. The greatest variations in temperature occur in the supporting portion in relation to the metal of the lower movable plate, which is responsible for reliable shutting off of the stream. The more shut-offs during teeming, the more intense the thermal action of the molten metal on the contact layer of the refractory. Corundum refractories are 1.5-2 times more heat resistant than periclase. Therefore, for gates for teeming on a continuous billet casting machine it is desirable to use periclase refractories, and in top teeming into molds corundum refractories. The essence of the corrosive action of molten steel on the gate plate material consists of spontaneous liberation on the contact surface of endogenic oxides of the primary oxide phase of the molten metal and subsequent development of the chemisorption process. The composition of the primary oxide phase is determined by the type of steel melted and the method of deoxidation of it. Depending upon the composition of the primary oxide phase the oxides precipitated may be in the liquid or solid state [2]. Steels containing flowable components of the primary oxide phase of the FeO-MnO-Si02 system, which are characteristic of rimmed and semikilled steels, are the most aggressive toward the refractory. Corundum refractories possess a lower resistance toward the corrosive action of such steels than periclase. Therefore, for teeming of them it is desirable to use periclase refractories. Since with an increase in temperature and contact time the corrosive action increases, for teeming on a continuous billet casting machine and teeming of large heats it is also desirable to use periclase refractories. Killed carbon steels are deoxidized with a somewhat larger quantity of silicon and sometimes aluminum is used. The oxide components of such molten steels are most frequently solid phases. In these cases there is not capillary penetration causing significant development of the depth of the reaction layer, and corrosion of the refractory is practically absent. In teeming of such steels the selection of the refractory is not signficant. Steels with an increased manganese content are distinguished by a significant quantity of its oxide in the primary oxide phase. In contrast to a periclase refractory, at the teeming temperatures a corundum refractory forms with this oxide a broad area of l~-melting compositions of secondary phases. Therefore in teeming of such steels it is desirable to use periclase refractory. An effective measure preventing penetration of the components of the primary oxide phase into the refractory is the introduction of carbon into the pores such as by impregnation by a coking hydrocarbon with subsequent heat treatment. It is desirable to use refractories with such a treatment for teeming of steels with fluid components of the primary oxide phase. Since corundum refractories are corroded more by these steels, treatment of them is more effective.