Arc Furnace Steel Research Articles

Experience of using evaporative cooling of graphitized electrodes to reduce their consumption in ore smelting furnaces

Consumable graphitized electrodes (GE) are widely used for supplying current to AC and DC EAF's, ore-smelting and indirectly heated electric arc furnaces. Due to large current, thermal and mechanical loads, their consumption in the structure of the cost of smelting in some cases, for example, in steel smelting reaches 30 %. Considering this, as well as the unstable global economic situation, when many enterprises use imported electrodes, solving the issue of reducing them is urgent. Foreign-made arc steel furnaces with a capacity of 100 tons and more successfully use evaporative cooling (EC) technology. Its use leads to a reduction in graphite consumption by an average of 10–15 %. However, for ore-thermal furnaces, no data on the experience of using EC GE has been found in the literature. The purpose of the work is to study the possibility of reducing the temperature and consumption of GE in arc ore-smelting furnaces when using EC technology. Experimental studies were carried out at the enterprise PC “AVISMA” (Berezniki), which includes three ore-smelting furnaces with a capacity of 100 tons. For the graphite electrodes used in these furnaces, modeling of their thermal state was performed with and without EC. Rational technological parameters of the cooling process were determined: water flow 1.5 m3/h and system turn-on time 5–15 minutes from the start of the current supply. An experimental design of the EC ring and a system for monitoring water and air flow have been developed. As a result of several heats, a decrease in the surface temperature of the GE was recorded when using EC with water on its side surface and a number of shortcomings were identified. Recommendations for improving technology and improving the design of the AI system are formulated

Застосування графітованих гнотових електродів на дугових сталеплавильних печах постійного струму

Застосування графітованих гнотових електродів на дугових сталеплавильних печах постійного струму

Application of graphitized wick electrodes in DC arc steel furnaces

Application of graphitized wick electrodes in DC arc steel furnaces

Моделирование переменных параметров работы дуговой сталеплавильной печи

Approaches to modeling arc steel furnaces are considered. As a result of the analysis of various approaches, a model with variable parameters R and XL was selected, which allows considering an arc furnace as a variable load with a corresponding effect on the supply networks. The resulting model is intended for inclusion in the general model of the furnace power supply system with a static var compensator and has practical application for setting up the control system of the compensating device.

Study of the Main Reasons for the Consumption of Graphite Electrodes in Electric Arc Steel Furnaces

Graphite electrodes are widely used in various industries, especially metallurgy. Their key features include inertness to most process environments, and electrical conductivity. However, there are a number of problems due to the peculiarities of the operating conditions. Graphite materials have good inertness towards gases, liquids and solids, as well as high electrical conductivity. In metallurgy, graphite electrodes are used in steel-making furnaces to supply electrical energy to the working space of the furnace. The article analyzes the main reasons for the consumption of graphite electrodes, both in normal and emergency situations. In the conclusion of the article, analyzes are made based on the results of graphite electrodes breakdowns.

Thermal and Physical Properties of Methane Family Hydrocarbon and Oxygen Combustion Products in State-of-the-Art Arc Steel Furnace

The work deals with the particular combustion characteristics of methane family hydrocarbons (methane, ethane, propane, butane) and wet natural gas with process oxygen at carbon dioxide and water steam dissociation in a state-of-the-art arc steelmaking furnace. An algorithm is developed to calculate chemistry, the amount and concentration of combustion products at carbon dioxide and hydrogen dissociation, their physical and thermophysical parameters; heating power, balance and actual temperature, heat and pyrometric factors are evaluated considering heat transfer by radiation into unbounded medium. Based on the calculation results the recommendations are given for development of cold charge material heating conditions in order to minimize dusting, carbon oxide and hydrogen and charge material loss.

Heat Exchange in High-Power Arc Steel Furnace when the Height of the Slag Layer Changes

Calculation results and analysis of changes in thermal radiation density of arcs by wall height for hundred-ton arc furnaces at different slag layer height and at equal arc power are presented. It was found that with an increase in the height of the slag layer from 70 to 300 mm, that is, with an increase in the depth of the arcs in the slag, the density of thermal radiation flows of the arcs in the most heat-loaded part of the walls decreases by 2 times. The efficiency of arcs increases with the increase in the depth of arcs in the slag and increases by 1.61 times when fully buried.

Specific Features of Thermal Performance of the Arc Steel Furnace in Unstable Properties Conditions of Burden Materials

In the production of steel in a state-of-the art arc furnace, there are two serious issues, resulting from a decrease in bulk density of burden materials, and an increase in non-ferrous metals concentration. The paper presents the analysis results of changes in the chemical composition of iron-containing materials related with an increase in the content of non-ferrous metals: copper, tin, lead, antimony and unspecified metals in a given steel grade and a decrease in the bulk density of burden materials. A method of reducing impurities by means of using pellets produced from natural raw materials, that are pure in terms of impurities, is presented. A method of setting up charging of burden materials with different bulk density, using the filling coefficient of the furnace operating volume, is proposed. Combined burden materials that include various types of scrap and non-ferrous metals of iron-ore pellets, that are pure in terms of impurities, will ensure high-quality steel production.

Снижение рисков опасных факторов на дуговых сталеплавильных печах

Снижение рисков опасных факторов на дуговых сталеплавильных печах

Arc Steel Furnace Operation at Changing Working Space Aerodynamic Flows

Results of the design analysis carried out using computer software are presented for boundary data complying with the currently operating state-of-the-art arc steel furnace. Flow of natural gas combustion products and oxygen are reviewed for the radial and tangential burner arrangement in the working space between the wall and the electrodes. Location of high temperature fields is determined and the expected heat transfer to the charge materials through the active surface participating in heat exchange is evaluated. Precipitation degree is determined for the dust participating in scull generation on a wall water-cooled surface and significant reduction of dust effect on electrodes.

Analytical study of heat exchange and efficiency of arc in arc steel-melting furnaces of small and large capacity

An analytical study of heat transfer and efficiency of arcs in arc steel furnaces of small and large capacity, 1.5-20 tons and 100-120 tons, respectively. We found out that the reason for the increased specific consumption of electricity for melting the batch in small capacity furnaces is the low efficiency of arcs equal to 0.55-0.57 and the corresponding specific energy consumption for melting 475-500 kWh/t. In furnaces of large capacity the efficiency of arcs is 0.78-0.8 and specific energy consumption is 360-375 kWh/t.

Software Complex for Research of Stability of Discrete Dynamic Systems with Delay

Поведение широкого класса систем с сосредоточенными параметрами может быть описано с помощью обыкновенных дифференциальных уравнений. Во многих процессах, изучаемых в экологии, экономике, физике, технике, медицине и т.д. ключевую роль играют эффекты запаздывания. Для исследования таких процессов приходится применять современные информационные технологии. В статье представлен программный комплекс, написанный на языке C (операционная система Microsoft Windows), позволяющий автоматизировать процесс исследования устойчивости системы с тремя степенями свободы с запаздыванием. Такие системы часто встречаются на практике (либо к ним можно привести системы большей размерности подходящим упрощением модели) и поэтому рассмотренная модель с результатами анализа может быть использована для исследования других практически значимых динамических систем. В качестве примера использования программного комплекса для исследования устойчивости системы с тремя степенями свободы, в которой проявляется эффект запаздывания, рассматривается задача о самовозбуждении колебаний системы электрододержателей (ЭД) дуговой сталеплавильной печи. Эквивалентная механическая модель представляет собой три ЭД, моделируемые твердыми телами, совершающими малые крутильные колебания. Самовозбуждение колебаний возникает за счет взаимного влияния электродинамических сил, действующих между электродами, и упругими силами конструкции. Идеализированная математическая модель колебаний трех ЭД представляет собой систему обыкновенных дифференциальных уравнений 6-го порядка с запаздыванием. С помощью программного комплекса построены кривые Dразбиения и получены области устойчивости при различных значениях параметров модели. Результаты исследования представлены в виде рисунков и таблиц. Так как для системы с тремя степенями свободы математический аппарат остается ещё достаточно простым, то материал, представленный в статье, можно использовать в образовательном процессе при подготовке специалистов по прикладной математике. The article presents a software package written in C (the Microsoft Windows) operating system that enables automation of studying stability of three-degree-of-freedom system stability with delay. Such systems are often found in practice (or systems of higher dimensionality can be brought to them by suitable simplification of the model) and therefore the considered model together with the results of analysis can be used to study other practically significant dynamical systems. As an example of using a software package to study the stability of a three-degree-of-freedom system, in which the delay effect is manifested, we consider the problem of self-excitation of the oscillations of the system of electrode holders (EH) of an arc steel furnace. The equivalent mechanical model is three EHs modeled by solids that perform small torsional vibrations. Self-excitation of vibrations arises due to the mutual influence of electrodynamic forces acting between the electrodes and the elastic forces of the structure. The idealized mathematical model of the oscillations of three EHs is a system of ordinary differential equations of the 6th order with delay. Using the software package, D partition curves were constructed and stability regions were obtained for various values of the model parameters. The results of the study are presented in the form of figures and tables. Since the mathematical apparatus is still quite simple for a three-degree-of-freedom system, the material presented in the article can be used in the educational process when preparing specialists in applied mathematics.

Main indices of steel industry of Russia operation in 2018

Extensive analysis of Russia steel industry state in 2018 presented. Dynamics and structure of main kinds of products production by Russian and world steel industry shown. Russia occupies the sixth position in the world among the biggest steel producers having the yearly volume of production of 71.7 mt (103.0% to 2017). Steel-works of Russia in 2018 produced 51.8 mt of hot metal. The production of finished rolled products equaled to63 mt. In 2018, the share of BOF steel and arc-furnace steel in the total volume of steel smelting reached 97.8% comparing with 97.5%in 2017. In 2018, the summarizedexport value of raw materials, ferroalloys, steel ingots, billets and rolled products increased by 22.4% comparing with 2017 and was equal to USD 25.6 billion. The summarized import value of raw materials,ferroalloys, steel ingots, billets and rolled products increased in 2018 by 6.2% comparing with the value of 2017 and was equal to USD 6.8 billion. Domesticconsumption of ferrous metals rolled products and steel pipesin 2018, due to preliminary estimation, totaled 39 and 10 mt correspondently. Economic indices of Russia steel industry plants operation quoted. The expenses of main steel-works per 1 ruble ofsold products in 2018 reduced by 5.8 kop. or 6.9% comparing with 2017, the products profitability (relation of sale profit to the product cost) increasedby 8.9%, the labor productivity in cost terms increased by 18.3%. The expenses per 1 ruble of sold products in 2018 at pipe-making plants reduced by 1.06% comparing with 2017, the products profitability increased by 1.14%, and the labor productivity increased in cost terms by 17.2%. Data on specific consumption of raw materials, materials and technological fuel for production ofhot metal, steel and rolled products in 2018 quoted, comparing with similar indices of 2017. Information on investment programs of Russian metallurgical and pipe-making plants, realized in 2018, quoted.

Characteristics and problems of exploitation of plated electrode carriers in arc steel furnaces

In this article, the processes of destruction of current-carrying arms made of plated copper-steel materials, leading to substantial reduction of their endurance, are discussed. Measures which may be recommended for ruling out the said negative processes are proposed.

НЕПРЕРЫВНЫЙ КОНТРОЛЬ ТЕМПЕРАТУРЫ ЖИДКОЙ СТАЛИ В ТЕХНОЛОГИЧЕСКИХ АГРЕГАТАХ МЕТАЛЛУРГИЧЕСКОГО ПРОИЗВОДСТВА

The article considers the method of continuous objective control of the temperature of liquid steel in metallurgical aggregates of steelmaking and foundry industries. The method is characterized by a sufficiently high accuracy (±9 °С), simple operation, reliability and service life, exceeding the service life of the refractory masonry of the process unit. The aim of the work is to develop a method for the continuous monitoring of the temperature of liquid steel in technological units of metallurgical production. The basis of the adapted method is the solution of the inverse heat conduction problem (usually incorrect), when, at known temperatures, temperatures on the layers of active thickness of refractory masonry (up to 80 mm) restore the temperature at the “melt – refractory masonry” boundary. The new methodological approach to the elements of novelty in the work is the continuous objective control of the temperature of liquid steel in metallurgical aggregates. The results of the justification and the technical solution, the results of the study of the accuracy of the method on the experimental bench and in real production conditions on the arc steel furnace are presented. The obtained experimental data reflect the sufficiently high accuracy and efficiency of the considered calculation method of continuous monitoring of the temperature of liquid melt. This task is relevant in the conditions of using of steel-furnace aggregates as efficient installations for obtaining the melt heated to a certain temperature. It is advisable to use the method in installations of out-of-furnace finishing of steel “furnace – ladle”. The calculation method is designed for software implementation using domestic low-cost microprocessor controllers both as an autonomous information technical control means and as part of an integrated element in the process automation system of steelmaking.

Allocation of the Environmental Impact in Iron and Steel Industry

Life cycle assessment (LCA) can provide technical support for environmental management in China. However, there is no consensus on allocation method in inventory analysis. According to the World Steel Association (WAS), the environmental impact, life cycle environmental load and environmental benefit of China's iron and steel industry should be considerd when investing scrap iron and steel. The results of this study show that according to the different allocation methods, the environmental impact of China's iron and steel industry will be divided into 3 methods: 1) not considering environmental load and environmental benefit of the environment (Cut-off approach); 2) considering the environmental load or environmental benefits (Waste evaluation method) and 3) considering environmental load and environmental benefits (Recycling benefits method). The environmental impact of Electric Arc Furnace (EAF) steel billet is raising by using the waste evaluation method compared with that of basic oxygen furnace (BOF), which are all decreased by using the cut-off approach. Recycling benefits method compared with Cut-off approach that the BOF hot rolled steel coil (HRC) environmental impact, the environmental impact of EAF steel billet all decreased, and leading the BOF hot rolled steel coil environmental impact to a larger proportion of the environmental impact.

The effect of electrode-holding arms on the electrical parameters of the bus-tube section of current lead in an arc steel furnace

The essence of the electromagnetic effect of metalware located near current-carrying elements has been shown. Aftereffects, such as heating of metalware, additional active losses of power supply, perturbation in the magnetic field, and consequent changes in the active resistance and inductive reactance of the equivalent circuit of a furnace have also been considered. The existing technique of taking into account the influence of metalware located near current-carrying elements on the electrical parameters of the current lead of high-power technological equipment has been examined, with its drawbacks being revealed. A method for increasing the accuracy and range of applicability of the technique has been suggested. To do this, a more universal coefficient of neighboring metalware (CNM) has been introduced. The coefficient allows us to take into account the influence of metallic structures on the resistance and magnetic reactance of the furnace circuit. The results of numerical simulations for a bus-tube section of current lead in a 100-t arc steel furnace (ASF) have been presented. The results of simulations were compared with the experimental data obtained by physical modeling of current lead of a 100-t ASF. A numerical model validated by such a way was used to obtain the dependences of active resistance and inductive reactance and CNM on the geometry of the investigated section and the properties of electrode-holding arms. The obtained dependences are the basis for an engineering technique intended to design current leads for an arc steel furnace.

Results of Modeling Operation of the High-Speed Regulator of Non-Contact Secondary Voltage of Furnace Transformer of the High-Power Arc Steel Furnace in Constant Primary Current Mode

The article describes main methods for regulation of the secondary voltage of furnace transformers (FT) of high-power arc steel furnaces (ASF), their advantages and drawbacks are outlined. Within consideration of the non-contact and high-speed regulation of FT voltage, the emphasis is put on using thyristor voltage regulator deployed in the intermediate circuit. The comparative evaluation of main energy indicators of the FT-ASF complex are given within using thyristor regulator of secondary FT voltage, and of traditional methods for controlling electric modes of ASFs by means of affecting the furnace transformed as the high-speed executive component of the regulation system. Main electric modes that can be obtained through using thyristor regulator of the furnace transformer in case of supporting the constant primary current in the FT, are considered. Results are obtained using a math model of the FT-ASF electrotechnical complex, developed in MATLAB Simulink package.

Research experiences on the reuse of industrial waste for concrete production

The aim of this study was to assess the feasibility of concrete production using different kinds of industrial wastes as “recycled aggregate”. The wastes studied in this work were: fly ashes and slags from Electric Arc Furnace (EAF) steel plant; foundry sands produced from foundry dies; slags from lead processing; Waelz slags; solid residues from municipal solid waste incineration (MSWI) plant (with mass-burning kiln and fluidized bed reactor); sludge from industrial wastewater treatment plants. Good compressive strength (similar to natural concrete) was achieved after 28 days of curing by concrete mixtures obtained with the partial replacement (from 7% to 40% by weight) of natural aggregates with slags from lead processing, foundry sands, Waelz slags and bottom ashes from MSW incineration. The worst mechanical and leaching behaviours were shown by concrete samples containing EAF fly ashes and sludge from industrial wastewater treatment. For the residues with the best performance, concrete products (kerbs and flat tiles) were casted. Their mechanical and leaching characterization has shown that the reuse of these residues for concrete product is feasible.

EFFECT OF MOISTURE DAMAGE ON GAP-GRADED ASPHALT MIXTURE INCORPORATING ELECTRIC ARC FURNACE STEEL SLAG AND COPPER MINE TAILINGS

Water damage is a vital factor affecting the durability of gap-graded asphalt. There is an urgent need for a pragmatic and reasonable test to evaluate this parameter. Previous research has proposed that tensile strength ratio is a promising test for this application. Therefore, the aim of this paper is to evaluate the effect of moisture damage on gap-graded asphalt mixture incorporating electric arc furnace (EAF) steel slag and copper mine tailings (CMT). Four material mixtures of eight mix designs were investigated. Each mix was conditioned in water for 24-hour and 48-hour before testing. The study adopted retained strength index (RSI), durability index (DI) and tensile strength ratio (TSR) to describe the durability of gap-graded asphalt incorporating EAF steel slag and copper mine tailings. The results reveal that all the mixes fulfill the prescribed criteria. Also, there is a strong correlation between the retained strength index and the durability index with a strong coefficient of determination, R2 of 0.9543. The results of the study further showed that gap-graded asphalt mixture incorporating EAF steel slag and copper mine tailings did not seem to pose any problem.