Electric Furnace Steelmaking Research Articles

TECHNOLOGY FOR ELECTROSLAG REMELTING WITH ROTATION OF THE CONSUMABLE ELECTRODE

It is known that metal which is produced by the method of electroslag remelting (ESR) has service properties superior to those of metal made by open refining and casting. This can be attributed to the better conditions which exist for refi ning in the specially chosen slag and for the crystallization of the metal in the case of ESR. However, the need for a two-stage metallurgical conversion (essentially requiring repeat refining) makes ESR metal more expensive than metal made by electric-arc refining. By resorting to out-of-furnace treatments, the content of harmful impurities in the latter product can be reduced to nearly the same level as in ESR metal. In addition, the consumption of electric power in the production of ESR ingots is more than three times greater than the level characteristic of steelmaking in electric furnaces. It is this circumst ance that is presently impeding the wider use of ESR [1]. The costs of producing ESR ingots could be reduced significantly by using an electroslag remelting technology that involves rotation of the consumable electrode around its axis. The General Metallurgy Department of South-Ural State University has already had many years of experience in developing and studying an ESR process that takes place in a centrifugal force field [2‐8]. Such a technology has several important advantages. Most significantly, it makes it possible to appreciably increase the productivity of the process (more than 25% in some cases) without increasing the amount of power that must be supplied to the slag bath. This is accomplished through a change in the hydrodynamic situation in the bath, a reduction in the height of the bath, and the forced removal of liquid metal from the electrode. The hydrodynamic pattern which exists during the melting of a rotating electrode is different from the pattern characteristic of an electrode that moves only vertically. An ascending slag flow is created in the zone near the consumable electrode as it rotates. While rising, the slag is heated and reaches its highest temperature in the immediate vicinity of the elec trode end that is being melted (Fig. 1 b). In the standard technology, slag washes over the melting conical portion of the electrode after it gives up heat to the water-cooled wall of the mold. Moving through the near-electrode region, the slag reaches its highest temperature at the boundary with the liquid metal bath (Fig. 1 a). The removal of liquid metal from the electrode as the latter rotates occurs mainly under the influence of centrifugal forces rather than gravitational forces, which is typical of the given (standard) remelting technology. When the electrode is melted in a centrifugal force field, the liquid phase (drops) are more shielded from the melting surface than when the electrode is not rotated. The melting end of the consumable electrode is flat when it is rotated. The slag level in the mold is thus lower than in the standard technology. In the latter, the slag bath is higher because slag is displaced by the conical end immersed in it. The decrease in the area of contact between the slag and the water-cooled wall of the mold also reduces heat losses by 9‐13%, the exact reduction depending on the parameters of the remelting process. The presence of a flat end makes it possible to ensure that the required distance is maintained between the electrode and the liquid bath with a 10‐15% decrease in the amount of flux which is used. In addition, rotation of the consumable electrode significantly improves the refining ability of the remelting process. This is due to the fact that the thickness of the layer of liquid metal (film) on the end of the electrode is uniform and mini

A Mathematical Model for the Reduction Kinetics of Iron Oxide in Electric Furnace Slags by Graphite Injection.

A three-phase, solid-gas-liquid, reactive jet is mathematically modeled in time domain for the injecting operation of graphite particles in complex electric furnace steelmaking slags to reduce the iron oxide contents. The model takes into account the jet penetration in the liquid, the physical changes that the slag suffers due to chemical composition variations, the surface active effects of silica in molten slags and the coupling-uncoupling flow characteristics between the carrier gas and the solid particles in the molten phase. The mathematical simulations indicate that at small particle sizes (100-150 μm) the reaction kinetics is controlled by the gas-melt interface, under this regime acid slags show higher reduction rates than basic ones. At larger sizes this reaction is controlled by the mass transfer of iron oxide from the bulk phase to the gas-melt interface and basic slags show higher reduction rates than acid ones. To obtain a given reduction rate of iron oxide there is an optimum particle size at which the consumption rate of the reducing agent is minimum. Below this size the particle is consumed by the reaction without reaching high efficiencies. Above this minimum the particle size is so large that it exits the molten bath only partially reached decreasing also the efficiency of the reaction. Just at this minimum the particle is totally consumed by the reaction with a minimum consumption rate of the reducing agent.

金属のリサイクリング

Almost of all metallic materials are generally finite underground resources and because of huge energy consumption and generation of environment pollution materials based on their production, the recycling of metals has a various profitable effects.The technology of recycling of metallic materials consists basically of the applications of their each extraction technology, but in some cases, unique treatment processes had been developed.In this paper, recent developments on recycling of various metals had been introduced and then as practical examples, recycling of waste cars and treatment of electric furnace steelmaking dusts are explained.

Schwermetall- und chloridhaltige Filterst�ube. I. Phasenanalysen und Modellversuche zum Recycling

Flue Dusts Containing Heavy Metal Ions and Chloride.I. Phase Analysis, Model Experiments for Recycling Four flue dusts from a cement factory, an electric-furnace steelmaking plant and a municipal waste plant were analyzed by powder diffraction methods. Chloride combines above all with alkali ions or heavy metal ions, especially yielding PbCl2 and KPb2Cl5. The controlled sublimation of these chloride compounds in open crucibles was developed and optimized in our laboratory. Between 850°C and 1150°C and at reaction times from 30 min up to 12 h, the chloride content decreases to below 0.1 wt-%. The sublimed phase mainly consists of alkali and lead chloride. Zinc is found in the flue dust as oxide and is enriched during this process. Recent investigations with a small waelz kiln give analogous results. With our procedure, the manufacturer by himself is able to exploit flue dusts containing a large amount of heavy metal elements and chloride which cannot be deposited. The remaining product contains mainly zinc oxide which can be recycled in the zinc industry or returned to the production process. The sublimed chloride compounds may be recycled in the potash industry.

Fugitive particulate emissions of three major industries

Abstract The physical and chemical characterizations of the fugitive particulate emissions from the electric furance steelmaking operations, cement productions, and asphaltic concrete plant were evaluated in this investigation. Kimoto high volume samplers were used for the determinations of total suspended particulate concentrations as well as the particle size distributions were measured by six-stage Anderson high volume cascade impactors. Moreover, the chemical compositions (Al, Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Cu, Zn, and Pb) of the fugitive particles smaller than 2.5 μm and in the 2.5–10 μm size range were analyzed by an X-Ray energy spectrometer. For electric furnace steelmaking operations, most of the fugitive particles occurred in the 2.7-3.6 μm size range. In addition, Fe and Cr were found to be in the coarse fraction as well as Mn, Cu, and Zn were the dominant elements in the fine fraction. For the different processes of the cement operations, there were large variances on the mass concentrations and size distributions of the fugitive particles. More than ninety percents of Ca was found to be in 2.5–10 μm size range. In the asphaltic concrete plant, the mass concentrations of the particulate fugitive emissions were much lower than those observed at the other two occupational environments, because of the good performance of the ventilation system. In summary, the chemical compositions (source profile) of the fugitive particle emissions obtained from this investigation could be used as a tracer in the receptor modeling for evaluating the contributions of the fugitive emissions to the total particle emissions from these three industries.

最近の製鋼用アーク炉設備と溶解技術の動向

最近の製鋼用アーク炉設備と溶解技術の動向

Mathematical model for computer simulation and control of steelmaking

A dynamic model for computer simulation and control of steelmaking has been developed. It is essentially based on multicomponent mixed transport control theory with the incorporation of energy balance calculations. The model is applicable to both steelmaking in electric furnaces as well as in oxygen steelmaking converters. The adjustable parameters of the model for simulation of oxygen steelmaking are gas evolution rate (Gco). oxygen flux factor (Fo) and emulsification factor (EM). These simulation parameters, when combined with on‐line measurement of off‐gas composition and temperature, enable complete dynamic control of the process. The model developed is applied, as an example, to an industrially produced heat in a top blown oxygen steelmaking converter and the results of simulation are discussed.

Cost efficiency of flame-guniting the lining of open-hearth and electric steelmaking furnaces

The use of flame-guniting for lining repair to the open-hearth and electric steelmaking furnaces of a number of Soviet plants is reviewed. Equipment and technology for flame-guniting the lining of furnaces, which provide for both local and general repairs to the walls, roofs, and bottoms of furnaces, are discussed. Methods are given for calculating expenditures for repair work and determining the cost efficiency of flame guniting relative to the increased number of heats per lining life. Results are given from calculations of the projected cost-efficiency of using flame-guniting for furnace lining repair at the metallurgical plants of the Ukranian Ministry of Ferrous Metallurgy.

Cleaning gases from electric steelmaking furnaces in slit-type Venturi tubes

Cleaning gases from electric steelmaking furnaces in slit-type Venturi tubes

Mechanization of labor-intensive operations in the fettling of electric steelmaking furnaces

Mechanization of labor-intensive operations in the fettling of electric steelmaking furnaces

Effect of recycling on residuals, processing, and properties of carbon and low-alloy steels

Because of the continuing increase in electric furnace steelmaking, which is a scrap-intensive process, and also in view of future new sources of scrap, such as municipal solid wastes, it is important to develop more knowledge about: (a) the effects of residual elements on steel, (b) processing strategies for producing high-residual steels, and (c) products in which residuals could be used to advantage. This review will first identify the important residual elements and the trends in their use and levels in steels. The effect of these elements on the processing phenomena and product properties of carbon and low-alloy steels will be discussed in detail. These phenomena and properties include hot shortness, scale adherence, room temperature tensile properties, impact resistance, and hardenability. Also discussed are examples of specific problems that residual elements present, both now and with emerging trends, for steel processing and applications, and the ways of using residuals to advantage.

An Overview of Contemporary Steelmaking Processes

Modern steelmaking processes are described. Recent evolution and development of pneumatic, open hearth, and electric furnace steelmaking processes are briefly reviewed, and their current status is outlined in terms of production of various types of steel, flexibility in raw materials consumed, variations in operating practices, energy conservation, and process control. Recent developments and innovations in steel production are described including bottom injection of gases and gas-solid mixtures. Improvements in control of pneumatic steelmaking are considered. Electric furnace steelmaking improvements via increased power input and productivity are described, along with recently developed water cooling systems for shell, walls, and roofs.

Increasing lining life in a high-capacity electric steelmaking furnace

Increasing lining life in a high-capacity electric steelmaking furnace

Dry cleaning of flue gases from low-tonnage electric steelmaking furnaces in bag filters

Dry cleaning of flue gases from low-tonnage electric steelmaking furnaces in bag filters

Direct Reduction of Iron Ore

In the search for a pure, available iron source, steelmakers are focusing their attention on Directly Reduced Iron (DRI). This material is produced by the reaction of a low gangue iron ore with a hydrocarbonaceous substance. Commercially, DRI is generated in four different reactors: shaft (moving-bed), rotary kiln, fluidized bed, and retort (fixed-bed). Annual worldwide production capacity approaches 33 million metric tons. Detailed assessments have been made of the uses of DRI, especially as a substitute for scrap in electric furnace (EF) steelmaking. DRI is generally of a quality superior to current grades of scrap, with steels produced more efficiently in the EF and containing lower levels of impurities. However, present economics favor EF steel production with scrap. But this situation could change within this decade because of a developing scarcity of good quality scrap.

Recovery of Zinc and Lead from Electric-Furnace Steelmaking Dust at Berzelius

The Waelz unit at the Berzelius Metallhutten GmbH plant in Duisburg, West Germany, was originally built to recover zinc and lead values in zinc retort residues and slags from lead shaft furnaces. The process has also proved suitable for recovering zinc and lead from steelmaking dusts. The metallurgical characteristics and information on operating costs encountered in the three decades over which this Waelz plant has been in operation at Berzelius are described and discussed.

Removing low-melting nonferrous metal impurities in electric-furnace steelmaking

Removing low-melting nonferrous metal impurities in electric-furnace steelmaking

Recovery of metals from a variety of industrial wastes

Bureau of Mines research on the development of practical processes for recovering metals and other materials from various industrial wastes is described. The work had a dual purpose: pollution abatement and conservation of scarce, costly materials. Electrochemical machining sludges were filtered to recover the electrolyte and smelted to produce valuable nickel-base alloys. Salable alloys were also produced by smelting stainless steel mill wastes. Shredded paper was used to reduce the hexavalent chromium in chromium etching wastes, after which copper, zinc, and chromium oxide were recovered as separate products. Electric furnace steelmaking dusts were pelletized with a reducing agent and heated to reduce zinc oxide and volatilize 98 percent or more of the zinc as metal.

Thirty years in the service of metallurgy

This has been the path followed by the institute in its 30 years of work: from the first cable-driven car dumpers, from the first design for a Soviet steam-driven railroad crane, from the MPZ-I small loader for the mines in the Nikopol' manganese basin, to unfied rotary and side-discharging fixed and mobile car dumpers, high-capacity machines for chipping out ladle and converter linings, machines for charging and patching open-hearth and electric steelmaking furnaces, machines for abrasive conditioning of metal, units for baling, finishing, and thermal hardening of rolled sections, and units for applying anticorrosion coating to rolled strip and sections.

Electric furnace steelmaking in the next decade

Electric furnace steelmaking in the next decade