Materials Science Forum Vol. 946

Abstract: In the report the scheme and features of thermal work of the chamber furnace of drum type for heating of metal products under hardening are presented. The technical characteristics of the furnace, some results of thermal calculation are shown. Computer simulation of gas motion and heat exchange processes in the furnace are presented. The study was performed using CAE-system (CAE, Computer aided Engineering) – software module ANSYS Fluent. Boundary conditions of flow flow flow were set in this module. To verify the convergence of the calculations, the control of the current values and calculated temperature residuals was used. The simulation results are presented graphically and contain a visualization of the temperature and velocity distribution fields, as well as a vector distribution of gas flow velocities. The obtained results of computer simulation allowed to estimate the efficiency of thermal and gas-dynamic work of the developed design of the chamber drum-type furnace with a constant temperature of the working space. The developed design of the furnace for heating metal billets with the movement of billets in the furnace on the drum allows to solve some problems of resource and energy saving, can also be used for heat treatment of bars, pipes, strips, and rolled bars of various shapes.

Abstract: High productivity of rolling and pipe rolling mills, good quality of finished metal products is possible to provide in the presence of powerful heating furnaces, well heating the metal with minimal oxidation and decarburization. Such conditions are provided by ring furnaces which are widely used for heating the preparations at rolling of pipes, wheels and bands of the railway rolling stock. The purpose of the heat – receiving structure of the metal, providing a set of physical and working properties, or impart to these materials the ductility required for subsequent machining. The article deals with the design and thermal performance of the ring furnace operating at ChelPipe’s Pipe Rolling Plant No.2. The problems arising during the operation of the thermal unit are analyzed. The paper describes the calculation of heating of metal and heat balance of the ring furnace. In the course of the analysis of the results of design studies, the shortcomings of the existing heat recovery system are revealed and measures for the reconstruction of the furnace to reduce fuel consumption and increase productivity (replacement of the existing brick lining with fibrous, the use of regenerative burners, the use of non-water-cooled partitions, etc.) are proposed. The paper analyzes the design and thermal performance of the ring furnace for heating of pipe billets before rolling. It shows a heat balance of the ring heating furnace and provides measures for furnace reconstruction aimed at reduction in fuel consumption and increase in efficiency: replacement of the existing lining with fiber lining, use of regenerative burners, application of non-water cooled walls.

Abstract: When re-melting scrap in electric arc furnaces (EAF), dust is formed. This dust is a rich zinc-containing raw material. The composition of the EAF-dust from JSC “Pervouralsk New Pipe Plant” was investigated. Dust contains 18 wt.% of zinc, more than 1/3 of zinc is a part of the slightly soluble in acids and alkalis of zinc ferrite ZnFe₂O₄. The aim of the work is to study the effect of roasting temperatures of 700, 850 and 1000 °C and the effect of CaO and Na₂CO₃ additives on the decomposition of zinc ferrite. Thermodynamic analysis of chemical transformations in dust during roasting showed that the additions of CaO and Na₂CO₃ provide destruction of zinc ferrite and promote the transfer of zinc into the acid-soluble form of ZnO. The effect of the roasting temperature, the duration of roasting and the amount of calcium oxide and sodium carbonate additions on the degree of zinc transition into acid-soluble form was studied experimentally. The best results were obtained at 1000 oС. The increase in the roasting time in the interval from 1 to 3 hours promotes an increase in the concentration of acid-soluble zinc in the cinder. The combined additions of 36 wt.% of Na₂CO₃ and 19 wt.% of CaO above the dust mass are optimal. The proportion of acid-soluble zinc in the cinder increased to 97–99 %, as a result of roasting under optimal conditions.

Abstract: Major unit for mineral melt production in industry is a shaft (cupola) furnace. Such type units are noted for the ease of fabrication and maintenance, high melting rate (up to 100-150 t/m² per day), as well as high heat utilization efficiency (up to 60-80 % of the total supply). Design disadvantages may include inefficient workspace side-view, poor thermal and gas dynamic performance, lack of practical methods to impact the melting process. Another pressing problem is related to melt production in the amount of no more than 3 t/h, with the average coke consumption of up to 24-270 kg/t, and the overheating temperature level of no more than 1350-1400 °С. Thermal and gas dynamic performance analysis of mineral wool cupola furnace, based on evaluation of zone balance model demonstrated that mineral melt is produced under conditions of essential nonuniformity of the bed temperature, gas phase composition and heat exchange conditions, both throughout the bed height and the unit cross section.

Abstract: Lump solid fuel is one of the most important charge material components in layered cupola units. It determines layer gas permeability, conditions development for heat exchange with gasses in it, heat generation process rate and intensity. In present-day conditions of material shaft melting charge materials of boosted fractional makeup are used, as well as oxygen, carbon and hydrogen enriched air. In the circumstances the issue of ensuring the best gas dynamic conditions become particularly vital, both for the furnace low and high temperature zones, at the charge component oxidation and recovery processes development. Under conditions of continuous charge component movement in the layered unit workspace they are subjected to abrasive action of charge components with the result, which may be described by mechanical properties based on mass yield of certain fractions after disruption in a closed drum М10 and М40. Coke lump behavior at relatively high temperature (below 1100°С) in the presence of complete fuel combustion products СО₂ and Н₂О may be implicitly evaluated by coke strength after reaction (CSR) and coke reactivity index (CRI). When studying, particular combustion features of coal coke in conditions close to shaft cupola unit operation data of the total differential scanning calorimetry (DSC) curve were used. Temperature ranges of intensive heat generation were determined from the beginning of active coke sample oxidation to completion of the burnout period, as well as apparent heating capacity and coke combustion thermal effect.

Abstract: Theoretical and experimental studies including a study of slag viscosity of the CaO-SiO₂-B₂O₃ system containing 25% Al₂O₃ and 8% MgO and equilibrium interphase distribution of sulfur and boron between slag and a low-carbon metal were carried out using a simplex-lattice experiment design and HSC 6.1 Chemistry software (Outokumpu). Fundamental research has contributed to the development of technology of basic boron-containing slags formation in ladle at ladle-furnace. These slags have a low viscosity, retaining high refining properties and providing direct microalloying of steel by boron. This technology has no analogues in domestic and foreign practice. The development of technology in the converter plant AO "ArcelorMittal Temirtau" (Kazakhstan) provided low-carbon steel production in wide grade composition, containing 0.001-0.008% boron and 0.004-0.014% sulfur, decreased consumption of manganese, high mechanical properties of rolled metal and improved environmental conditions.

Abstract: A series of industrial experiments was carried out on the sinter machine No. 1 of the sinter department of JSC "Ural Steel". The dynamics of the sinter mix temperature during the technological stages of its preparation from pelleting to loading on pallets was studied, depending on a water temperature change during pelletizing. It was defined that for the winter working of the sinter department of JSC "Ural Steel" the water temperature increases, which supplied the pelletizer to moistening, for every 10 ° C, facilitates an increase in the temperature of the sinter mix on the pallets by 1.5-2.0 °C. Therefore, for stable sinter mix production with a temperature of more than 55 ° C, it is necessary to use water supplied to the pelletizer for moistening, with a temperature of at least 85°C. To implement the proposed technology, it is necessary to equip the sinter machines with water-heating recuperative heater, installed above the sintering machine behind the ignition hood and using heat, radiated from the surface of the sinter.

Abstract: This work studied a decomposition and reduction of complex carbonate (sideroplesite) siderite lump ore from the Bakal’s deposit. The decomposition caused formation of complex oxides (Fe,Mg,Mn)O and (Fe,Mg,Mn)O·Fe₂O₃, and it preceded the Fe reduction; the weight loss during the decomposition process reached about 32%, being followed by the formation of a large number of pores. As the pores and micro-pores provide deep penetration of the carbon monoxide in the bulk of the ore lumps, it seemed that the pores would allow reduction of this ore without difficulties. However, during reduction experiments it was discovered that the distribution of the reduction process and formation of the metal phase were not connected with the pores’ distribution. The reduction process developed via an electrochemical mechanism, and the channels of the distribution of the reduction process were oxides of metals which were difficult to reduce under the presented experimental conditions; these oxides were mostly represented by the magnesia and silica compounds. The high rate of the iron reduction from the complex iron-manganese-magnesium oxides was explained by the high rate of distribution of the negatively charged anion vacancies forming on the surface of the oxide, due to reaction with a reducing agent.

Abstract: In this work the solid-phase reduction of iron from the Suroyam titanomagnetite ore was studied during metallization in a rotary kiln. The technique of preparation of the ore and reducing agent for metallization and the process of continuous processing of materials in a rotary kiln were described in detail. For metallization the temperature was chosen 1150°C, due to low melting point of apatite from one of the components. The results of the electron microscope analysis of the initial ore and samples subjected to metallization for 1-hour reduction time were presented. The reduction of iron occurred despite absence of pores and contact with a reducing agent in the grains of titanomagnetite. Iron in the grains of titanomagnetite surrounded by apatite was reduced to wustite; whereas, iron surrounded by clinopyroxene was reduced to metallic iron. This indicated the effect of composition of the gangue materials on the reduction process.

Abstract: The mathematical description of the electron mechanism of reduction of metals from complex polymetallic types of ore has been suggested. The description of the mechanism was based on diffusion and thermal processes occurring in the phases of a reducing agent and an oxide, and chemical reactions on the surface of a phase boundary. The effect of the major physics-chemical parameters on the rate of formation and movement of the reducing vacancies was considered. The obtained model allows calculation of the process of metal reduction from the bulk of a complex oxide by using the approach of the electron mechanism, which considers the process of reduction not as the interaction of the reducing agent with molecule of the metal oxide, but as the interaction with the oxygen anion of a crystal lattice.