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Number of results: 27
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Abstract

The article presents the results of tests of the application of magnetic fuel activators, which improve the efficiency of metallurgical furnaces and positively affect the ecological aspects of their work. Energy indicators for metallurgical furnaces during operation before and after installation of magnetic fuel activators as well as the results of composition and concentration of emitted pollutants are included in the paper. The magnetic activation of liquid and gaseous fuels modifies their structure. As a result of the activation, the fuel mixture is selectively saturated with oxygen in the zone of free fuel flow. The combustion conditions were close to optimal, which is confirmed by the reduction of pollutants in the exhaust gases. Fuel saving in the combustion process is also a measurable economic effect. The tests included ovens of several types: pusher furnace, one and two chamber furnaces and a furnace with a rotary shaft. Several-month measurement cycles were carried out on each of them. The experiments consisted in the analysis of gas and heat consumption per month in individual furnaces before and after the use of magnetic fuel activators. The effectiveness of using activators was determined on the basis of the results of the tests carried out. As a result of a twelve-month test cycle on the pusher type furnace, a 36% reduction in gas consumption and a 22% reduction in heat consumption were achieved. After a seventeen-month measurement cycle on chamber furnaces, a 35% reduction in gas consumption and 6% in heat consumption were achieved. The tests on furnaces with a rotary shaft lasted fourteen months and showed a reduction in gas consumption by 8%. An improvement in the composition of fumes in the furnace atmosphere was achieved in all units with magnetic activators installed, as well as a reduction in the emission of harmful pollutants into the atmosphere from the installation.
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Abstract

The article discusses the process of copper production in a slurry furnace and in a converter, with the indication of corrosion effects of the extractor. The furnace shaft and settling furnace of the flash furnace were analyzed. The basic factors determining the choice of singlestage technology of copper smelting in relation to the exploitation of refractory materials were indicated. The effects of dissolving the furnace lining material through slag have been presented. Structural analysis results using a scanning microscope are also included. The kinetics of destruction of ceramic materials under the influence of copper slag were evaluated. It has been shown that detailed analyzes are necessary in order to extend the time of furnace extensibility of furnaces in copper processes. The surface layer of the crucible softens due to saturation with slag reagents and is then washed out and moves in the solid form to the slag. The research in the article indicate not only the possibility of dissolution of the ceramic material in the molten slag, but also possibility of erosive activity of the slag on that material.
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Abstract

Discusses an attempt to optimize the operation of an electric furnace slag to be decopperisation suspension of the internal recycling process for the production of copper. The paper presents a new method to recover copper from metallurgical slags in arc-resistance electric furnace. It involves the use of alternating current for a first period reduction, constant or pulsed DC in the final stage of processing. Even distribution of the electric field density in the final phase of melting caused to achieve an extremely low content of metallic copper in the slag phase. They achieved by including the economic effects by reducing the time reduction.
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Abstract

Compacted graphite iron, also known as vermicular cast iron or semiductile cast iron is a modern material, the production of which is increasing globaly. Recently this material has been very often used in automotive industry. This paper reviews some findigs gained during the development of the manufacturing technology of compacted graphite iron under the conditions in Slévárna Heunisch Brno, Ltd. The new technology assumes usage of cupola furnace for melting and is beeing developed for production of castings weighing up to 300 kilograms poured into bentonite sand moulds.
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Abstract

The research involved coal from 11 coal mines in the USCB in Poland, intended for combustion in power plants and for home furnaces. It has been stated that the content of As, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sb and Zn in the ash of coal fines from the USCB with a density of <1.30 × 103 kg/m3 is the largest, and in the ash fraction with a density >2.00 × 103 kg/m3 is the smallest The fraction ash of coal fine with a density> 2.00 × 103 kg/m3 has the greatest impact on the content of As, Cd, Co, Cr, Mo, Pb and Zn in whole coal fines from the USCB. In turn, the largest impact on the content of Cu, Ni and Sb in whole fine coal ash has the fraction of coal fine having a density of 1.60–2.00 × 103 kg/m3 (for Cu) and fraction with a density <1.35 × 103 kg/m3 (Ni and Sb). The main carriers of elements in fine coal ash, thus in future furnace waste, are the grains of aluminosilicates and iron oxides resulting from the combustion of probably fusinite and semifusinite and the combustion of adhesions of these macerals with dolomite, ankerite and pyrite. The purification of fine coal from the matter with a density >2.00 × 103 kg/m3 may reduce the sulfur content (by 40%), the content of main element oxides (from 33% to 85%) and the content of ecotoxic elements (from 7% to 59%) in fine coal ash, i.e. in potential furnace wastes. Due to the small content of mineral matter, ash and sulfur in coal, small content of Al, Fe, Ca, Mg, Na, K, P oxides and high content of SiO2 in coal ash, low value of the Rogi sinterability index, small inclination of coal fine to slag the furnaces and boiler fouling by sludge, the investigated coal was favorable for technological reasons, fuel in power plants and for home furnaces
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Abstract

Blast furnace and cupola furnace are furnace aggregates used for pig iron and cast iron production. Both furnace aggregates work on very similar principles: they use coke as the fuel, charge goes from the top to down, the gases flow against it, etc. Their construction is very similar (cupola furnace is usually much smaller) and the structures of pig iron and cast iron are very similar too. Small differences between cast iron and pig iron are only in carbon and silicon content. The slags from blast furnace and cupola furnace are very similar in chemical composition, but blast furnace slag has a very widespread use in civil engineering, primarily in road construction, concrete and cement production, and in other industries, but the cupola furnace slag utilization is minimal. The contribution analyzes identical and different properties of both kinds of slags, and attempts to explain the differences in their uses. They are compared by the contribution of the blast furnace slag cooled in water and on air, and cupola furnace slag cooled on air and granulated in water. Their chemical composition, basicity, hydraulicity, melting temperature and surface were compared to explain the differences in their utilization.
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Abstract

Dust generated at an electric arc furnace during steel production industry is still not a solved problem. Electric arc furnace dust (EAF) is a hazardous solid waste. Sintering of well-prepared briquetted mixtures in a shaft furnace is one of possible methods of EAFD utilisation. Simultaneously some metal oxides from exhaust gases can be separated. In this way, various metals are obtained, particularly zinc is recovered. As a result, zinc-free briquettes are received with high iron content which can be used in the steelmaking process. The purpose of the research was selecting the appropriate chemical composition of briquettes of the required strength and coke content necessary for the reduction of zinc oxide in a shaft furnace. Based on the results of the research the composition of the briquettes was selected. The best binder hydrated lime and sugar molasses and the range of proper moisture of mixture to receive briquettes of high mechanical strength were also chosen and tested. Additionally, in order to determine the thermal stability for the selected mixtures for briquetting thermal analysis was performed. A technological line of briquetting was developed to apply in a steelworks.
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Abstract

Any complete CFD model of pulverised coal-fired boiler needs to consider ash deposition phenomena. Wall boundary conditions (temperature and emissivity) should be temporally corrected to account for the effects of deposit growth on the combustion conditions. At present voluminous publications concerning ash related problems are available. The current paper presents development of an engineering tool integrating deposit formation models with the CFD code. It was then applied to two tangentially-fired boilers. The developed numerical tool was validated by comparing it with boiler evaporator power variation based on the on-line diagnostic system with the results from the full CFD simulation.
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Abstract

The most important and the most frequently used plastics are polyethylene (PE) and polypropylene (PP). They are characterised with high heating values (approximately 40 MJ/kg). Moreover, their chemical composition, based mainly on carbon and hydrogen, allows to use them in industrial processes. One of the methods of utilisation of plastic waste can be its use in the metallurgical industry. This paper presents results of thermal decomposition of waste PE/PP. Chemical and thermal analysis (TG) of studied wastes was carried out. Evolved gaseous products from the decomposition of wastes were indentified using mass spectrometry (TG-MS). This paper also presents an application of plastic wastes as supplemental fuel in blast furnace processes (as a substitute for coke) and as an addition in processes of coking coal.
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Abstract

Foundry dust from blasting and grinding of castings contain a high amount of iron, ergo it is possible its recycling in foundry process. Dust was compacted by briquetting, two kinds of briquettes were prepared (A contained 95% magnetic part of dust from casting blasting +5% bentonite and B contained 95% mixture of dust from casting grinding and magnetic part of dust from casting blasting + 5% bentonite) and used as a part of charge into the electric induction furnace. It was found that addition of briquettes has had an influence of a chemical composition of cast iron above all on content of sulphur, phosphorus and silicon. It was not reflected in decrease in tensile strength and in microstructure. Yield of metal from briquettes was not lower then 70%.
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Abstract

The gas porosity is one of the most serious problems in the casting of aluminum. There are several degassing methods that have been studied. During smelting of aluminum, the intermetallic compound (IMC) may be formed at the interface between molten aluminum and solid steel of crucible furnace lining. In this study, the effect of degassing treatment on the formations of IMC has been investigated. The rectangular substrate specimens were immersed in a molten aluminum bath. The holding times of the substrate immersions were in the range from 300 s to 1500 s. Two degassing treatments, argon degassing and hexachloroethane tablet degassing, were conducted to investigate their effect on the IMC formation. The IMC was examined under scanning electron microscope with EDX attachment. The thickness of the IMC layer increased with increasing immersion time for all treatments. Due to the high content of hydrogen, substrate specimens immersed in molten aluminum without degasser had IMC layer which was thicker than others. Argon degassing treatment was more effective than tablet degassing to reduce the IMC growth. Furthermore, the hard and brittle phase of IMC, FeAl3, was formed dominantly in specimens immersed for 900 s without degasser while in argon and tablet degasser specimens, it was formed partially.
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Abstract

It is demonstrated that during secondary refining at the ladle furnace the carbon content of steel and the residence time of the metal in the ladle exert a significant impact on the residual content of non-metallic inclusions (NMI) in steel. Mathematical calculations showed that the dynamic forces have minor effect on the motion of small sized NMI, making it difficult to penetrate deep into the slag.
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Abstract

In this study, solidification/stabilization (S/S) of electric arc furnace dust (EAFD) which is generated during the production of steel from scrap metals and classified as hazardous waste were investigated by using different ratios of cement and low grade MgO (LG MgO) as binding agents. Type I PC 42.5 R portland cement and LG MgO which contains 70–80% MgO were used. S/S blocks that contain different ratios of binding agents which have 1/0.5 – 1/1 – 1/2 – 1/3 – 1/4 – 1/5 cement/LG MgO ratio and S/S blocks which contain only cement and no LG MgO agents were prepared. These blocks, which contain 3 different waste ratios according to weight, 20%, 30% and 40% respectively, were produced and exposed to 28-day water purification. At the end of the purification process, S/S blocks were extracted using TCLP (Toxicity Characteristic Leaching Procedure) tests in order to determine the leaching behavior of Zn, Pb, and Cd in S/S blocks. By the end of this study, it was concluded that the recovery of EAFD is possible and applicable by immobilization. The findings of the study concluded that environmental performances or structural properties of blocks contain 30% waste by weight are suitable. This method is a proper one for recovering and treatment of EAFD with mixture of cement and LG MgO.
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Abstract

The aim of this work was to determine the influence of various variants of bioleaching on effectivity of releasing chosen critical metals: rhodium, cadmium, indium, niobium and chromium from ashes which are a byproduct of municipal waste and sewage sludge thermal processing. The research was conducted in 3 variants that considered different process factors such as temperature (24ºC and 37ºC), mixing intensity and aeration. After 5 days of the process the analyses were made of metals content, sulfate concentration, pH, general number of bacteria number, index of sulfur oxidizing bacteria. The best results of bioleaching were achieved by running the process at the temperature of 24ºC with aeration. The efficiency of rhodium and cadmium release from the byproduct of municipal waste thermal processing was above 90%. The efficiency of indium and chromium release reached 50–60%. Only niobium leached better in mixing conditions. The byproduct of sewage sludge thermal processing was far less susceptible to bioleaching. The highest effectivity (on a level of 50%) was reached for indium in temperature of 24°C with aeration. The efficiency of bioleaching depended on waste’s physiochemical properties and type of metal which will be released. Aeration with compressed air had a positive influence on the increase of sulfur oxidizing bacteria what corresponded with almost double increase of sulfate concentration in leaching culture. Such conditions had a positive influence on the increase of the efficiency of bioleaching process. Heightening the temperature to 37°C and slowly mixing did not impact bioleaching in a positive way.
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Abstract

Higher active power of a submerged arc furnace is commonly believed to increase its capacity in the process of ferrosilicon smelting. This is a true statement but only to a limited extent. For a given electrode diameter d, there is a certain limit value of the submerged arc furnace active power. When this value is exceeded, the furnace capacity in the process of ferrosilicon smelting does not increase but the energy loss is higher and the technical and economic indicators become worse. Maximum output regarding the reaction zone volumes is one of parameters that characterize similarities of furnaces with various geometrical parameters. It is proportional to d3 and does not depend on the furnace size. The results of statistical analysis of the ferrosilicon smelting process in the 20 MVA furnace have been presented. In addition to basic electrical parameters, such as active power and electrical load of the electrodes, factors contributing to higher resistance of the furnace bath and resulting lower reactive power Px demonstrate the most significant effect on the electrothermal process of ferrosilicon smelting. These parameters reflect metallurgical conditions of ferrosilicon smelting, such as the reducer fraction, position of the electrodes and temperature conditions of the reaction zones.
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Abstract

To minimize oxides of nitrogen (NOx) emission, maximize boiler combustion efficiency, achieve safe and reliable burner combustion, it is crucial to master global boiler and at-the-burner control of fuel and air flows. Non-uniform pulverized fuel (PF) and air flows to burners reduce flame stability and pose risk to boiler safety by risk of reverse flue gas and fuel flow into burners. This paper presents integrated techniques implemented at pilot ESKOM power plants for the determination of global boiler air/flue gas distribution, wind-box air distribution and measures for making uniform the flow being delivered to burners within a wind-box system. This is achieved by Process Flow Modelling, at-the-burner static pressure measurements and CFD characterization. Global boiler mass and energy balances combined with validated site measurements are used in an integrated approach to calculate the total (stoichiometric + excess) air mass flow rate required to burn the coal quality being fired, determine the actual quantity of air that flows through the burners and the furnace ingress air. CFD analysis and use of at-the-burner static, total pressure and temperature measurements are utilized in a 2-pronged approach to determine root-causes for burner fires and to evaluate secondary air distribution between burners.
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Abstract

The purpose of this work is to find a correlation for heat transfer to walls in a 1296 t/h supercritical circulating fluidised bed (CFB) boiler. The effect of bed-to-wall heat transfer coefficient in a long active heat transfer surface was discussed, excluding the radiation component. Experiments for four different unit loads (i.e. 100% MCR, 80% MCR, 60% MCR and 40% MCR) were conducted at a constant excess air ratio and high level of bed pressure (ca. 6 kPa) in each test run. The empirical correlation of the heat transfer coefficient in a large-scale CFB boiler was mainly determined by two key operating parameters, suspension density and bed temperature. Furthermore, data processing was used in order to develop empirical correlation ranges between 3.05 to 5.35 m·s-1 for gas superficial velocity, 0.25 to 0.51 for the ratio of the secondary to the primary air, 1028 to 1137K for bed temperature inside the furnace chamber of a commercial CFB boiler, and 1.20 to 553 kg·m-3 for suspension density. The suspension density was specified on the base of pressure measurements inside the boiler’s combustion chamber using pressure sensors. Pressure measurements were collected at the measuring ports situated on the front wall of the combustion chamber. The obtained correlation of the heat transfer coefficient is in agreement with the data obtained from typical industrial CFB boilers.
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Abstract

The principle of work of many metallurgical shaft furnaces is based on the flow of reaction gas through the descending packed bed composed of metallurgical materials. Hot gases flow up the shaft furnace through the column of materials, give their heat to the descending charge materials. At the same time due to their reducing nature they interact chemically, causing the reduction of oxides inside the charge. In real conditions, during the course of the process, the powder is generated, the source of which is the batch materials or it is introduced into the as part of the process procedure. The powder in the form of thin slurry is carried by the stream of flowing gas. Such multiphase flow might considerably affect the permeability of the charge due to the local holdup of powder. The holdup of solid phase in packed beds of metallurgical shaft furnaces leads to radial changes in bed porosity. Radial changes in bed porosity uneven gas flow along the radius of the reactor and negatively affect the course and efficiency of the process. The article describes the model studies on radial distribution of carbon powder holdup in the packed bed composed of metallurgical materials. The powder was divided into fractions – “static” and “dynamic”. Large diversity of carbon powder distribution was observed in the function of the radius of reactor in relation to the bed type, apparent velocity of gas carrying powder and the level of bed height.
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Abstract

An economical alternative for the steel industry which uses a separate ferrosilicon and aluminum for the deoxidization of steel is a complex deoxidizer in the form of FeSiAl alloys. The effectiveness of complex deoxidizers is higher and they have a positive effect on quality improvement and also for mechanical properties of the finished steel. It is associated with a smaller number of non-metallic inclusions and a more favorable its distribution in the structure of steel. Noteworthy are the waste from the mining industry simultaneously contains SiO2 and Al2O3 oxides with a few of dopants in the form of CaO, MgO, FeO, TiO2 oxides. These wastes are present in large quantities and can be a cheap raw material for obtaining complex FeSiAl ferroalloys by an electrothermal method. “Poor” hard coal grades which so far did not apply as a reducing agent in the ferroalloy industry because of the high ash content can also be a raw material for the electrothermal FeSiAl process. The electrothermal FeSiAl melting process is similar to the ferrosilicon process in the submerged arc furnace. For this reason, a model based on Gibbs’ free enthalpy minimization algorithm was used to analyze the simultaneous reduction of SiO2 and Al2O3 oxides, which was originally elaborated for the ferrosilicon smelting process. This is a system of two closed reactors: the upper one with the lower temperature and the lower one with the higher temperature. Between the reaction system and the environment, and between the reactors inside the system, there is a cyclical mass transfer in moments when the state of equilibrium is reached in the reactors. Based on the model, the basic parameters of the electrothermal reduction process of SiO2 and Al2O3 oxides were determined and a comparative analysis was made towards the ferrosilicon process.
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Abstract

The post-processing slags containing about 0.8 wt.% of copper were subjected to the treatment of a complex reagent. The chemical composition of the complex reagent has been elaborated and patented in frame of the Grant No. PBS3/A5/45/2015. The slags had an industrial origin and were delivered by the Smelter and Refinery Plant, Głogów, as a product of the direct-to-blister technology performed in the flash furnace assisted by the arc furnace. An agglomeration of copper droplets suspended in the liquid slag, their coagulation, and deposition on the bottom of furnace were observed after the treatment this post-processing slag by the mentioned reagent. The treatment of the post-processing slags by the complex reagent was performed in the arc furnace equipped with some additional electrodes situated at the furnace bottom (additional, in comparison with the arc furnace usually applied in the Smelter and Refinery Plant, Głogów). The behaviour of the copper droplets in the liquid slag within the competition between buoyancy force and gravity was studied from the viewpoint of the required deposition of coagulated copper droplets. The applied complex reagent improves sufficiently the surface free energy of the copper droplets. In the result, the mechanical equilibrium between coagulated copper droplets and surrounding liquid slag is properly modified. Eventually, sufficiently large copper droplets are subjected to a settlement on the furnace bottom according to the requirements. The agglomeration and coagulation of the copper droplets were significantly improved by an optimized tilting of the upper electrodes and even by their rotation. Moreover, the settlement was substantially facilitated and improved by the employment of both upper and lower system of electrodes with the simultaneous substitution of the variable current by the direct current.
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Abstract

This study explores the influence of alkali activators on the initiation of polymerization reaction of alumino-silicate minerals present in class-F fly ash material. Different types of fly ash aggregates were produced with silicate rich binders (bentonite and metakaolin) and the effect of alkali activators on the strength gain properties were analyzed. A comprehensive examination on its physical and mechanical properties of the various artificial fly ash aggregates has been carried out systematically. A pelletizer machine was fabricated in this study to produce aggregate pellets from fly ash. The efficiency and strength of pellets was improved by mixing fly ash with different binder materials such as ground granulated blast furnace slag (GGBS), metakaolin and bentonite. Further, the activation of fly ash binders was done using sodium hydroxide for improving its binding properties. Concrete mixes were designed and prepared with the different fly ash based aggregates containing different ingredients. Hardened concrete specimens after sufficient curing was tested for assessing the mechanical properties of different types concrete mixes. Test results indicated that fly ash -GGBS aggregates (30S2‒100) with alkali activator at 10M exhibited highest crushing strength containing of 22.81 MPa. Similarly, the concrete mix with 20% fly ash-GGBS based aggregate reported a highest compressive strength of 31.98 MPa. The fly ash based aggregates containing different binders was found to possess adequate engineering properties which can be suggested for moderate construction works.
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Abstract

Zinc is present in electric arc furnace dust (EAFD) mainly in two basic minerals, namely as franklinite ZnFe2O4 and/or zincite ZnO. While zincite is relatively reactive and easily treatable, franklinite is considerably refractory, which causes problems during EAFD processing. In this work EAFD containing 18.53% Zn was leached in water solution of ammonium carbonate. This leaching solution selectively leaches zincite, while franklinite is refractory and stable against leaching in this case. The temperature dependence of zinc leaching from EAFD was studied and the activation energy EA was determined by two methods: 1.) classically based on zinc chemical analyses from the leaching solution and 2.) by using of X-Ray diffraction qualitative phase analyses of leaching residues. The determined values of activation energies 37.41 and 38.55 kJmol–1 match perfectly, which show the excellent possibility of using X-Ray diffraction toward the study of leaching kinetics at properly chosen experimental conditions. The important result is the determination of the amount zincite and franklinite in EAFD, which is not possible by using of classical chemical methods.
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Abstract

The aim of research was creation of a furnace for aluminum alloys smelting “in a liquid bath” in order to reduce metal loss. In the paper, the author demonstrates the results of research on smelting of aluminum alloys in a shaft-reverberatory furnace designed by the author. It has been shown that smelting aluminum alloy in a liquid bath was able to significantly reduce aluminum loss and that shaft-reverberatory design provided high efficiency and productivity along with lower energy costs. Ensuring continuous operation of the liquid bath and superheating chamber, which tapped alloy with the required texture, was achieved by means of the optimal design of partition between them. The optimum section of the connecting channels between the liquid bath of smelting and the superheating chamber has been theoretically substantiated and experimentally confirmed. The author proposed a workable shaft-reverberatory furnace for aluminum alloys smelting, providing solid charge melting in a liquid bath.
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Abstract

Deoxidation of steel with carbon under reduced pressure is often used for increasing the steel purity. Suitable units for this purpose in foundries are vacuum induction furnaces. Possibilities of increasing the steel purity by deoxidation with carbon in the vacuum induction furnace were studied for the steel for the petrochemistry of specific composition 25Cr/35Ni. The charge composed of the return material only was melted in the air. During melting the charge oxidized and the oxidizing slag formed. Chemical composition of steel, morphology, chemical composition of inclusions in the steel and chemical composition of slag after vacuuming were studied on the basis of samples taken before and after vacuuming. Temperature and oxygen activity were measured before and after vacuuming. Globular inclusions with dominant content of silicon and manganese were observed in steel before and after vacuuming. Contents of total oxygen in steel didn’t change significantly during vacuuming. On the basis of composition of inclusions and measured oxygen activity the activity of Cr2O3 in inclusions was calculated. A slag sample was taken after vacuuming and equilibrium oxygen activity in steel with regard to the Cr2O3 content in the slag was estimated from the slag composition. Equilibrium oxygen activity in relation to the Cr2O3 content in the slag was higher than equilibrium activity measured in the steel. For this reason it is not possible, under the studied conditions, to decrease oxygen content in steel during vacuuming.
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