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By S. Seetharaman

The present paper presents. the concept of micro-models and illustrates the application of the same in the simulations metallurgical processes. Development of micromodels requires access to accurate thermodynamic, thermophysicaland kinetic information for the relevant systems with suitable models to extrapolate the data as functions of temperature and composition. Experimental measurements and modelling of the thermodynamic properties, sulphide capacities and viscosities of oxide melts carried out in the department are presented. The incorporation of these models in process models, with special reference to ladle refining of steel is illustrated. Typical example of micro-modelling of solid-gas reactions is also presented.

Jan 1, 1999

By Z. M. Zheng

Cyclic voltammetry, potential step, and ac impedance techniques were applied to study the electrochemical reaction of arsenopyrite in chloride solutions. The relationship between anodic current density and time in potential step measurements indicates that the oxidation of arsenopyrite is irreversible. The results of the constant potential coulometry show that the stoichiometric factor of the total electron involved in the overall reaction is 14. It is proposed that the dissolution of arsenopyrite is retarded by coverage of sulfur produced in the reaction as an intermediate product. The measured results of ac impedance strongly support the proposition. The proposed reaction mechanism also explains satisfactorily the charging current density and Tafel slopes measured in potential step measurements.

Jan 1, 1995

By P Ridgeway, D Xie, M A. Somerville, S Jahanshahi, H Rogers, J G. Mathieson, Y Pan, N Haque, P Zulli, T E. Norgate, L Lu, A Deev

In 2006 the Australian steel industry and CSIRO initiated an R&D program to reduce the industry’s net greenhouse emission by at least 50%. Given that most of the CO2 emissions in steel production occur during the reduction of iron ore to hot metal through use of coal and coke, a key focus of this program has been to substitute these with renewable carbon (charcoal) sourced from sustainable sources such as plantations of biomass species. Another key component of the program has been to recover the waste heat from molten slags and produce a by-product that could be substituted for Portland cement. This paper provides an overview of the low-emission Integrated Steelmaking Process, progress made over the past seven years and the program’s future direction which includes proposed demonstrations of the technologies developed including large scale piloting and full scale plant trials.

Jan 1, 2014

By R. Luo, R. V. Kumar

"The co-deposition of cobalt and nickel as a binary alloy has been studied by both cyclic voltammetry and long-period controlled-potential electrolysis. Cyclic voltammetry experiments showed that the cathodic current density for the mixed Co-Ni (Co-Ni=1:3) electrolyte is noticeably higher than that obtained on electrolyte containing single CO2+ or Ni2+ (II) salt of the same ionic strength. The onset potential observed for the mixed salts electrolyte was also less cathodic (negative) than that for the single metal salts, respectively. The effects of a number of operational and compositional parameters on the co-deposition of cobalt and nickel were studied. The parameters under investigation include cathode (deposition) potential, temperature, CI-/Sol ratio in the electrolyte, the amount of additives such as H3B03, and acidity of the electrolyte.Optimum operational conditions were established for the deposition of cobalt and nickel binary alloy. These results are discussed with respect to feasibility of reclaiming cobalt, nickel and chromium from mixed superalloy scraps by melt-refining (under nitrogen and/or ammonia), followed by electrorerining of cast anode for co-depositing Co/Ni and thermal decomposition of chromium nitride for recovering chromium metal."

Jan 1, 1997

By Hong Ouyang

A unified computational model has been developed for the Bridgman growth processes of B-NiAI and CdTe crystals. To handle the geometrical and physical complexities, a two-level approach has been developed. At the gtobatlevel, conjugate heat transfer, phase change dynamics, and variable material properties along with the realistic geometries and thermal boundary conditions are accounted for inside the entire crystal growth system. Refined calculations are then made within the ampoule, with the boundary conditions supplied by the global simulations. This model can optimize the use of computational source, help understand solidification behaviors, and improve designs of crystal growth system.

Jan 1, 1996

By Jackson Jenkins

The second survey of world copper SXEW plants has been completed. Solvent extraction and electrowinning data published in 1996 has been updated and leach data from seventeen plants is now included. The following pages list the results of the thirty- two plants that responded to the survey. Selected information is summarized in graphical form.

Jan 1, 1999

By Batric Pesic

Reactions of metallic iron were studied in several different aqueous solution systems: water, medium salt solution used for the growth of T ferrooxidans, ferric iron solution and solution containing T ferrooxidans. Each system was studied under abiotic and biotic conditions in the presence of T ferrooxidans and as a function of pH, particle size of iron powder, temperature, ferrous and ferric iron concentrations. It was found that metallic iron reacts with water differently than does with ferric iron in water. Surprisingly, T ferrooxidans were non-functional in the dissolution of metallic iron. Also, the reactions of metallic iron with pure water were indistinguishable from the reactions with water containing medium salts for bacterial growth. The reactions with ferric iron were also independent of medium culture compounds. The mechanisms of metallic iron reactions with ferric ions are different from the mechanisms of metallic iron reactions with water.

Jan 1, 2001

By Viktor. P. Popov, Oleksandr. V. Derev'yanko, Oleksandr. I. Raychenko

"This paper is devoted to scrutiny problem of obtaining electro-contacts by electro-discharge sintering technology. A new unconventional method of electro contacts production (on Aggraphite base) can yield essential optimization resource.Review of three electro-technological methods of processing contacts materials is presented:- using graphite powder cladded by Ag;- mixture of graphite powder(which is a non-cladded powder) with Ag powder and addition of Fe powder particles;- method of infiltration of melted Ag into graphite piece without deformation and rupture of object.This technological approach can give the possibility to increase of compression strength of electro-contacts materials up to 340 MPa and more under conditions of additional reinforcing components (for example, by Fe).IntroductionThe electric current can be an active ""participator"" of the powder metallurgy technology [l]. At the passage of electric current through powders or some powder mixtures the phenomena including phase transformations arise. Here such effects, which are observed in the Ag-graphite and Ag-Fe-graphite powder mixtures and in the pair Ag-porous graphite, are described.The Ag-graphite composition materials (CM) are used, for example, as electric contacts [2, 3]. Since a material being produced is destined for the contacts it is necessary to take into account the following aspects: commutating current, its character and voltage, active or reactive character of working load, geometrical dimensions of contacts, quantity and frequency of switching on and switching off, pressure on contacts, distance between contacts, method of arc control, surrounding medium, its content, pressure and temperature. Thus, these and, maybe, choice of some other circumstances influence design, materials and production technology of contacts. The range of problems concerned dictates such steps as alloying of contact materials, optimization of structure, selection of kind of graphite, its connection with metal [4-10]. It is expedient to recall the main procedures of the first stage of the conventional technology: dosage of the initial graphite powder and binder-phenolic resin plastic varnish (for example, Bakelite), mixing, densification, thermal treatment, crushing, grinding, sieving, drying, dosage of grained graphite, dosage of the initial silver powder, obtaining of the silver salt solution, settling of salt, filtration, washing, drying of the cladded graphite powder, thermal treatment, obtaining of the graphite powder of particles cladded by silver. The second stage of the convectional technology starts by obtaining of the cladded graphite powder and finishes by annealing of the pressed blanks (Fig. 1)."

Jan 1, 2004

By Katsunori Yamaguchi

The zinc, lead and alumina contents in copper smelting slag are increasing with the increase in waste recycling. The recovery of base metals such as lead and zinc from copper converter slag is important from both an economical and environmental perspective. As a fundamental study of the metal recovery by reduction process, activity coefficients of ZnO and PbO in the CaO-SiO2-FeOx-5mass%AlO1.5 slag under iron saturation at 1573K are derived from the data of slag-metal equilibrium experiments. On the basis of the obtained data, the activity coefficients of ZnO and PbO in the CaO-SiO2-FeOx-5mass%AlO1.5 slag were compared with those of the CaO-SiO2-FeOx ternary system. Addition of alumina increases activities coefficient of ZnO and PbO in SiO2 rich side of the slag, and decreases them in CaO rich side.

Jan 1, 2006

By K. Krishnapisharody, G. A. Irons

"The modeling of gas-liquid plumes in steelmaking ladles has been the subject of many investigations. In most studies, the “modified” Froude number, based on the momentum of the injected gas, has been employed to characterize two-phase plumes. This approach has several shortcomings and is critically reviewed in the present work. Based on an extensive review of previous work and theoretical considerations, it is demonstrated that the injected momentum and consequently, the modified Froude number has no significance to gas blowing operations in Ladle Metallurgy. Instead, an approach based on the “plume” Froude number, previously shown by the authors as the proper form for Froude similarity, is extended as a simpler alternative.IntroductionGas injection is central to most Ladle Metallurgy operations. During ladle processing, the steel melt is usually stirred by an inert gas like Argon through porous plug(s) fitted in the bottom of the ladle or a lance inserted deep into the melt. The purging serves several purposes viz., homogenizing the melt, flotation of inclusions, enhancing the rates both of refining reactions and dissolution of alloying elements and promoting inter-phase interactions in the ladle.The topic of gas injection into liquid baths has been the subject of several investigations in the past. A great deal of this work, both experimental and computational, was devoted to describing the structure and properties of two-phase plumes as reviewed recently [1]. Generally, the ascending two-phase mixture is sub-divided into three distinct regions [2]: the jet core, transition and the bubble plume, respectively. The jet region, where the momentum of the injected gas is transferred to the bulk liquid, is also called the ‘momentum region’. In a similar manner, the plume is called the ‘buoyancy region’ where the motion of liquid is caused by the buoyancy force exerted by the bubbles. The proper characterization of these regions is important for the analysis and modeling of stirring operations in Ladle Metallurgy. Although many mathematical correlations exist for this purpose, some issues of theoretical and practical interest to the modeling of gas-liquid plumes need further attention."

Jan 1, 2012

By Fan Jiang, Haigang Wang, Shi Liu

"This paper describes several applications of Electrical Capacitance Tomography (ECT) in gassolid two phase flows. A new image reconstruction algorithm was evaluated by both simulation and experiments. It is then applied to the online measurement of solids distributions in square circulating fluidized beds (CFBs) and good results were obtained. From the measurement of solids distributions in the bottom zone of a CFB, a bubbly fluidization pattern is identified. A cross-correlation technique was combined with the solids concentration measurements to obtain the flow rate through the dip leg of the cyclone, i.e. the circulating rate of a test CFB. The same· technique was applied in a dense phase pneumatic transport pipe provides the solids concentration, and the flow rate of a wavy gas-solids flow.IntroductionElectrical capacitance tomography (ECT) has been developed for imaging multiphase distributions in the 90's of the ·last century. It is a non-intrusive method. The principle of ECT can be firefly described as follows:Firstly ECT uses a number of electrodes to surround the measuring zone, depicted by Fig. I. The capacitances between the electrodes are measured in turn and an array C is obtained that contains a total number of m independently measured capacitances. Meanwhile the measuring zone is virtually divided into a grid of n pixels, represented by an array G, named the image vector, the gray level of each pixel represents the local value of the concentration of the material. As the material distribution will be reflected by the capacitances between each pair of electrodes, such distributions can be reconstructed according to the measured capacitance, a process called image reconstruction. A common image reconstruction method is called linear-backprojection (LBP). It linearize the relationship between the dielectric distributions in the measuring zone and the capacitances between the electrodes as the following:"

Jan 1, 2004

By G. A. Brooks

Increasing interfacial area through gas injection is one of the main methods for accelerating reaction between slag, metals, and gases in modern pyrometallurgical reactors. In slag-metal reactors, the generation of a large number of metal droplets into the slag phase through high gas velocity has a much larger effect on the overall kinetics compared to the enhanced mass transfer through mixing. Top blowing technology generates large interfacial areas (>300 m2/tonne) through high impingement gas velocity at short distances between the exit of the injection lance and the metal-slag interface. Phase separation may become a limit at the case of very high interfacial areas, though there is still only limited understanding of the trajectories of metal droplets in slag-metal-gas emulsions.

Jan 1, 2003

By Avijit Moitra

The behavior of the solidifying shell in the early stages of solidification has an important influence on the final quality of continuously-cast steel slabs. In order to understand the thermal and mechanical behavior of the shell, a two-dimensional transient piecewise-coupled finite-element model has been developed. The model simulates a transverse section of the slab as it moves down through the mold and incorporates the effects of heat conduction, solidification, shrinkage, turbulent fluid flow, thermal distortion of the mold and the visco-plastic behavior of the steel. Coupling between the thermal and the mechanical model is based on the mutual dependence of heat transfer across the interface between the shell and the mold and the size of the gap. The effects of mold distortion and taper on the gap size are also included. The effect of fluid flow has been incorporated via a heat flux imposed at the solid-liquid interface, which is obtained from a separate fluid flow model. The high temperature creep and plasticity of the steel is incorporated through a unified constitutive law defining the inelastic strain rates as a function of temperature, time and stress state. The model can be applied to various problems in continuous casting, such as the formation of surface defects and the design of mold taper.

Jan 1, 1992

By Erik Olsson, Gunilla Hyllander, Stefan Schuster, Lena Sundqvist Ökvist, Maria Lundgren, Michael Hensmann, Olavi Antila

"Residual materials from the integrated steel plant itself or other sources often contain valuable compounds of e.g. C and Fe. Dust and sludge have to be agglomerated to be able to recycle to the blast furnace (BF) via top-charging. By injection of the materials, preparation methods in terms of e.g. drying and/or screening only, can be used. Alternative carbon materials (ACM) in terms of BF dust and sludge have been successfully injected up to levels of 60 kg/tHM in the LK.AB Experimental Blast Furnace (LKAB EBF®). Efficiency in recovery of valuable compounds as well as the behavior of undesired elements have been evaluated and are discussed.IntroductionTraditionally, recycling of steel in-plant fines is made via the sinter plant and blast furnace route. Steel plants operating with 100% pellet as ferrous burden and have no sinter plant. There are limited areas for land fill and costs are caused for preparation of landfills and deposit fees. Very fine paniculate dusts or sludges cause decreased productivity and increased coke rate in the sinter plant, and therefore other ways for recycling must be considered. Injecting them into the BF could be an economically and technically feasible alternative. Additionally, as the materials contain valuable compounds of e.g. C and Fe."

Jan 1, 2012

By N. S. Raghavendran

Based on the weld pool length and width calculations due to an empirical model (1) for submerged arc weld metal, an elegant quantitative definition of tandem submerged arc welding is established. On the basis of this theoretical consideration optimum welding parameters for joining 25 mm thick low carbon steel plate in two passes by tandem wire submerged arc welding have been experimentally found out. An assessment of the metallurgical quality of weld metal and the dependence of mechanical propenies on pool overlap has been made. Also the solution of Rosenthal (2) etc. for a moving point source of welding, which was used as a guide line in formulating the empirical model for the calculations of weld pool dimensions, is compared with the solution of empirical model for submerged arc weld pool dimensions.

Jan 1, 1990

By Michael D. Odekirk

The U.S. Bureau of Mines investigated solvent extraction methods for recovering scandium from water leach filtrates of sulfated tantalum tailings. These complex solutions typically contained 20 or more metals in significant quantities. Two commercially available organics, DEHPA and PC-88A, were identified as effective scandium extractants. The two organics were tested in continuous solvent extraction circuits to compare loading and stripping kinetics, recyclability, and general processibility. Results showed that 95 pct of the scandium, greater than 80 pct of the zirconium, and only small amounts of other solubilized metals were extracted. Scandium was stripped directly as a 3.6 pct Sc precipitate when a 3n NaOH liquor was used as the stripping agent. This precipitate was subsequently upgraded to 94 pct ScE3 via a selective HE leach.

Jan 1, 1993

By Ian Baker, Xavier Pierron

"Iron aluminides hold great promise for intermediate temperature applications (to ~ 600°C) because of their excellent oxidation and sulphidation resistance and good strength. However, they have poor low temperature ductility, a feature which is exacerbated by water-containing environments. This paper presents an overview of the effects of environment on the ductility of iron aluminides, including the effects of iron aluminum ratio; ternary alloying additions, particularly boron; strain rate; and temperature. The mechanisms involved in water-induced embrittlement are discussed.IntroductionOver the last few years, it has became increasingly evident that the ductility and fracture toughness of many intermetallic compounds, particularly aluminides, are reduced dramatically if they are mechanically tested in either air or in hydrogen-containing atmospheres (1-5). For FeAI and Fe3AI, it has been shown that water vapor, for example in air at room temperature, can form atomic hydrogen by reacting with the Al atoms (1, 2). As a result in iron aluminides, the environmental embrittlement process is quite similar to traditional hydrogen embrittlement. This can be easily demonstrated by either testing an iron aluminide in an environment free of the deleterious species or by testing at high strain rates, both of which result in greater ductility. The purpose of this paper is to review recent progress in understanding environmental embrittlement in FeAI and Fe3AI, and to consider possible environmental embrittlement mechanisms. Greater understanding of this phenomenon will lead ultimately to remedies to this problem which is a major reason for preventing the practical application of these materials. First, some background on the iron-rich aluminides."

Jan 1, 1996

By Tong Zhilin

The reasons why the pits were formed on the cathode in the process of Ni electrowinning and the methods how to prevent these pits from forming are described. Some examples are presented. It has 'been proven that P507 and P204 present in the electrolyte can effectively prevent pits from forming on the cathode.

Jan 1, 1993

By Kikuo Okuyama, I. Wuled Lenggoro, Manabu Shimada

"Aerosol processing of materials such as (i) gas-to-particle conversion process (e.g., Chemical Vapor Deposition (CVD) method) and (ii) liquid (or droplet)-to-particle conversion process (e.g., spray pyrolysis) has become of major interest to produce novel submicron- or nanometer-sized particulate material used in electronic and chemical industries. After reviewing recent theoretical and experimental researches on the evaluation of properties and morphology of fine particles by the CVD and spray pyrolysis methods, the importance of the process engineering approach· for aerosol processing of materials and the use of advanced aerosol measurement technology have been pointed out.IntroductionMaterial synthesis via aerosol processing offers a route to producing nanometer-sized and submicrometer-sized particles of high purity with specifically tailored chemical and physical properties. Especially, single nanometer-sized particles (nanoparticle materials) are considered to play an important role in the synthesis of nanostructured materials as well as in nanotechnology in 21st century due to their quantum effect and so on.However, the transformation of gaseous or liquid precursors to the final functional particulate matters consists of various complex chemical and physical processes. In order to control the size distribution and morphology of produced particles, it is important to analyze and model various phenomena, such as gas-phase or liquid-phase chemical reaction, nucleation, condensation, agglomeration and sintering that occur simultaneously in aerosol material processing. By introducing the Aerosol Science and Materials Science, the authors have been trying to model the changes in particle properties and morphology by gas-to-particle conversion and droplet-to-particle conversion processes. The authors have also been trying to obtain the experimental data on the particles properties as accurate as possible."

Jan 1, 2000

By H. Jiang, S. Yang

"The main processes for nickel metallurgy in China consist of electric arc furnace smelting to produce low grade nickel matte and converter to high grade nickel matte, grinding and flotation to separate nickel sulfide from copper sulfide and direct electrolysis of nickel matte. Systematic studies on the properties of electric furnace slag, smelting process for nickel matte, anodic process of nickel matte, cathodic process of nickel electrolysis have been done in our labs. In addition, an approach to a new hydrometallurgy process for nickel matte has been done. The feature of the new process is one stage acidic leaching of high grade nickel matte. The leaching solution could be purified by deposition way or by solvent extraction way. There are two leaching rate-determing steps, chemistry reaction-determing one at temperatures below 600C and diffusion-determing one at temperatures higher than 600 c. The acidic leaching fraction reacted dvaties with leaching time t according to the equation 1-(1- a ) 1/3=kt. The experimental data also show that the leaching reaction rate varies with concentrations of H+, Cl-, and it is also effected by copper sulfide and Cu++. The Cu++ ion can retard the leaching reaction due to forming a copper sulfide layer on the matte surface and the equation 1- 2/3 a. - (1- a: ) 2/3 akt can be used for the case. However the copper sulfide added into nickel matte can facilitate the leaching process. The research work for nickel metallurgy done by others in China has also been mentioned in this paper.Large scale production of nickel in China started in 1960s.The main processes consist of electric arc furnace smelting to produce low grade nickel matte and converter to high grade nickel matte grinding and floatation to separate copper sulfide from nickel sulfide and direct electrolysis of nickel matte.To reduce nickel loss in slag a reseaech group organized by Jinchuan Company and Central South Institute of Mining and Metallurgy (now the Central South University of Technology) measured the viscosity surface tention density conductance melting point and structure of the slag(I).lt has been found that the physico-chemical properties of the slag depend on the components SiO2 ,MgO and FeO but FeO in the slag is too high and the statistic analysis of data from industry gave an equation to correlate the content of Ni in slag with the content of Ni in matte and the composition of slag again it was pointed out that the content of FeO in slag effected the loss of Ni in slag very much (2). The ratio (FeO+MgO) to SiO2shouid be less than 1.13 and the content of Fe3O4should be as low as possible but the reaction"

Jan 1, 1988