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By O. Ryosuke Suzuki

A new metallurgical process via sulfide is proposed: a sulfide is produced at a high temperature from its metallic oxide using gaseous CS2, and this sulfide is electrochemically reduced to its metallic state using molten salt. This combined process via sulfide is effective to obtain high purity of metallic powder, even if the metal in its oxide is strongly combined with oxygen. For example, it is not easy to reduce stable oxide TiO2, and only Ca can remove oxygen to form α-Ti. However, a fairly large amount of oxygen remains as Ti–O solid solution. Because the solubility of S in Ti is very small, this proposal was examined experimentally both on the conversion of TiO2 to TiS2 and on the successive reduction of TiS2 to Ti. TiO2 powder was exposed to CS2 gas flow at 1073 K, and the conversion to TiS2 was confirmed. TiS2 could be reduced to Ti powder either by calciothermic reduction or electrolysis in a CaCl2 melt. By Ca reduction at 1133 K in CaCl2 melt, sulfur concentration decreased to 0.03 mass%S when the amount greater than twice the stoichiometric calcium amount is added. By electrochemical reduction at 1173 K in CaCl2–CaS melt, S concentration significantly decreased to 0.01 mass% S when four times larger amount of electric charge was supplied.

By T. A. George, David J. Sellmyer

"The concept of achieving a useful high-energy-product magnet through appropriate nanostructuring of known hard and soft phases has been tantalizing researchers since the idea was first proposed. The fabrication of exchange-coupled nanocomposite magnets faces several challenges including aligning the easy anisotropy axes of the hard-phase grains. Here we investigate experimentally two-phase nanostructures of hard Lio-ordered FePt and soft iron-rich/cc Fe(Pt). The Fe-Pt thin films were produced by epitaxial cosputtering onto MgO (001) single-crystal substrates which lead to strong (001) texturing. The measured hysteresis loops indicate nearly ideal exchange coupling. Excellent magnetic properties are obtained, with largest values of coercivity (51 kOe), saturation magnetization (1287 emu/ cm3, J, = 16.2 kG), and nominal maximum energy product (58 MGOe).1. IntroductionA key figure of merit for permanent magnets is the maximum energy product (BH)rrw.x. The achievable maximum energy product is determined by a magnet's saturation magnetization M, and its magnetic anisotropy. For example, it is well known that (BH)rrw.x :S 4n2M,2• In the past, record energy products have been the result of discovering new compounds with high values of magnetization and anisotropy. However, finding new compounds with better magnetic properties than the current record-holding magnet Nd2Fe14B has proven to be difficult. A different approach is to exploit the exchange coupling mechanism between known hard and soft magnetic phases to enhance the maximum energy product [1-5]. In such a composite system, high coercivity is achieved due to the anisotropy of the hard phase as well as a nanostructure which prohibits large-scale domain wall reversal mechanisms. Magnetization is enhanced by the soft phase and loop squareness results from texturing of the hard phase easy-axis as well as complete exchange coupling between the coexisting hard and soft grains."

Jan 1, 2012

By Jong-Oh Jo1

Thermodynamics of Ti, N and O in liquid iron was studied in order to establish a data base for the prediction of TiN and TiOx formation in liquid stainless steels containing various alloying elements including Cr, Ni and Si as a function of temperature. The interaction parameters of these elements on Ti and N were determined using the metal-nitride-gas equilibration technique. The TiN stability diagram for a commercial stainless steel grade was constructed from the measured thermodynamic parameters, and its validity was confirmed experimentally. The interaction parameters between Ti and O, and the equilibrium constants for Ti deoxidation reactions for the formation of Ti2O3 and Ti3O5 were also determined by the equilibration of the melts with those oxides identified by the XRD and the EPMA analyses.

Jan 1, 2006

Novel techniques were developed to obtain samples from and make measurements in the shaft of the flash furnace at the Kalgoorlie Nickel Smelter. The data obtained was used to validate mathematical models of the burners and the reaction shaft. Particle, gas and wall temperatures were measured along with the oxygen potential of the molten particles. Collected particles were characterised by sizing, chemical analysis and optical microscopy. The region of the shaft immediately beneath the burner where the rate of change was most rapid received special attention.

Jan 1, 1993

By K. H. Bech, S. T. Johansen

"The mass transfer at fluid-fluid interfaces due to turbulent agitation is investigated theoretically. In particular a theory is derived for interface stresses due to interface energy and surface renewal. This theory indicates that surface renewal may take place if the geometry is sufficiently large and if surface tension is sufficiently low.By using a model for a typical turbulent structure we compute the interface mass transfer for a stressless interface and a fully interface. Results for the general situation is not presently available. The computed results are used to derive analytical expressions for the mass transfer based on turbulent kinetic energy and free stream turbulent length scales.One important application of the theory is the mass transfer at the electrolyte side of the bath-metal interface in the Hall-Heroult process. For this process we show that mass transfer should be expected to be of the rigid surface type."

Jan 1, 1999

By Seshadri Seetharuman

The present paper summarises a series of measurements of the interaction parameter of oxygen in liquid copper with respect to a third element, e(M)o, where M is Mn, Zn, As, Se or Te which are common impurities in the liquid metal. The technique employed was the solid electrolyte galvanic cell method. The cell used may be represented as Pt, W or cermet / Cu-O-M // ZrO2 - CaO // AO, A /PT where AO/A represents a suitable oxide/metal reference. The measurements indicate that Mn and Zn interact very strongly with oxygen in liquid copper while, in the case of arsenic the interaction parameter is nearly zero. The behaviour of the elements Se and Te is unique with respect to oxygen interactions in copper bath. At oxygen levels, xo= 10-4 ? 10-5, the apparent interaction parameters are negative, comparable to that for sulphur. On the other hand, at lower oxygen levels, the results indicate that the interaction parameter values are positive. The results are discussed in the light of some of the theoretical models for solute interactions in liquid metals.

Jan 1, 1993

By J. Alberto Vázquez M.

A sensor employing yttria-stabilized zirconia (YSZ) was used to determine the oxygen activity of molten copper at laboratory scale at temperatures of 1200° and 1300 dc. The reference electrode was a Ni-NiO mixture. The amount of the deoxidizing agent (CU3P) ranged from I to 3% of the mass of copper. Thermodynamic analysis of the Cu-O-P liquid system was carried out to predict the required deoxidizing agent and the final composition of the molten copper. Both results, calculated and experimental, show that the oxygen removal is more efficient at lower temperatures. The kinetics of the deoxidizing reaction is very fast in the first minutes of the treatment. A metalography analysis of rapid cooled samples show the oxygen and phosphorus distribution

Jan 1, 2003

By Kongfang Feng, Fei Ruan, Zhiyu Liu, Jieyu Zhang, Xin Hong, Shaobo Zheng, Jixu Wang, Jinyin Xie

"Mixing phenomena in smelting reduction furnaces with asymmetric side blowing were studied in this paper. Mixing phenomena in a smelting reduction furnace was represented as the mixing time by electrical conductivity measurements. Experiments were performed in a water model under various operating conditions to determine the effects of horizontal angle, radial angle, inserting depth, flow rate of the upper and the lower side nozzle, the included angle between the upper side nozzle, and the lower side nozzle on mixing phenomena in smelting reduction furnace. Comparing mixing time and mixing phenomena, the optimal conditions were obtained for an asymmetric side blowing process.IntroductionIn recent years, many countries have put forward development strategies for saving resources and environment-friendly, the development of various industries had to face its influence for resources and the environment .As we all know, the steel industry is a pillar industry of the global economy, in which ironmaking is an important part of it. In the modern ironmaking process, the blast furnace is regarded as the most important equipment and tool. But with the increasing scarcity of metallurgical coke resources and considering the environmental impact of such processes, metallurgists proposed the concept of smelting reduction. Smelting reduction processes to produce hot metal from iron ore and coal were being developed as a possible alternative to the traditional blast furnace. At present, a number of smelting reduction processes had been developed all over the world, they were mainly included COREX, HISMELT, FINEX, DIOS, etc."

Jan 1, 2012

By Per Anders Eidem, Merete Tangstad, Jens Davidsen

"During excavations of submerged arc furnaces producing silicomanganese, silicon carbide (SiC) has been found. Contributing to the size of the inactive area of the furnace, the active area of the furnace where reactions occur will decrease, thus reducing the potential for pre-reduction in the furnace.This work studied the formation of SiC from the liquid-solid reaction between slag, metal, and metallurgical coke. Slags and metals with different levels of silica (S1O2) and silicon (Si) have been studied. The slag and metal has been heated together with coke, and the samples investigated by microprobe. The results show that SiC was formed on the coke particle through reactions with both slag and metal. For the metal, the carbon most likely diffused through the SiC to react with Si in the alloy. SiC formation with slag is likely to go through the reduction of Si02 to Si.IntroductionToday, Silicomanganese (SiMn) is produced in submerged arc furnaces (SAF) by reduction of S1O2 and manganese oxides, mainly with metallurgical cokes. Typically, the tapped metal has a silicon content of 17 - 20 wt.%. To achieve higher levels of Si, the metal can be refined by adding off-grade silicon metal, yielding low carbon SiMn. [1]. What is believed to be SiC that has been found during dig-outs of SiMn furnaces producing high silicon alloy. It is possible that excess amounts of SiC in the furnace cause operational problems, since SiC will occupy furnace volume. As SiC accumulates, the active volume of the furnace will decrease, increasing the flow of material and gas in the active areas of the furnace. Formation of SiC is inevitable, so it is desired to keep the formation as low as possible. To be able to control the formation of SiC, one has to understand the basic mechanisms."

Jan 1, 2012

By Rafael Padilla

The recovery of copper from chalcopyrite concentrates by leaching is difficult due to the slow dissolution kinetics of this mineral in most leaching media. However, recovery of copper from sulfidized chalcopyrite (a mixture of CuS and FeS2) by leaching is faster and could be selective depending on the leaching media. In this paper, the result of an investigation on the H2SO4-O2 pressure leaching of sulfidized chalcopyrite is presented. The variables considered in the study were stirring speed, concentration of sulfuric acid, temperature, and partial pressure of oxygen. The experimental data indicated that stirring speed over 500 rpm and sulfuric acid concentration over 0.1 M had very little effect on the leaching rate. An increase in temperature from 90 to 100 ºC increased both copper and iron dissolution; however, further increase to 120 ºC affected negatively the copper dissolution. Oxygen partial pressure was found to be the main variable that controls the copper/iron selectivity of the leaching. An increase in oxygen partial pressure increased significantly the rate of copper dissolution but deteriorated the copper/iron selectivity. The analysis for sulfur of the leaching solid residues indicated that most of the copper sulfide sulfur in the sulfidized concentrate oxidized to elemental sulfur.

Jan 1, 2006

By Li. Jiarong, Zuojian Liang, Qingyan Xu, Baicheng Liu, Shizhong Liu, Hailong Yuan

Single crystal solidification of turbine blades is a key technology for the production of reliable and high efficiency gas turbines. The solidification process of single crystal investment castings causes a number of problems that have to be solved such as the increase of casting defects and complexity of production process. Computer modeling and simulation is helpful to predict the defects and improve the process design. In the paper, a mathematical model for three dimensional simulation of solidification and single crystal growth of investment castings was developed based on CA, mechanism of crystal growth and basic transfer equations such as heat, mass transfer equations. Many factors including constitutional undercooling, curvature undercooling and anisotropy, which had vital influences on microstructure evolution, were considered in the model. Temperature, crystal growth interface and structure defects of investment castings of single crystal superalloy were investigated at withdrawal rates of 4.5mm/min and 7mm/min. Simulated results showed that microstructure evolution and structure defects were predicted reasonably and calculated results were coincident with experimental ones. The study indicated that three dimensional solidification simulation technique is a powerful tool for understanding the fundamental of solidification and the formation of structure defects in single crystal investment castings and finally for optimizing process design.

Jan 1, 2004

By Suguru Kohno, Yoshihiro Momose, Masakazu Honma, Tokirou Kamosawa

Copper metal surfaces have been examined by an extremely sensitive surface analysis technique called temperature programmed photoelectron emission (TPPE). The surfaces were ultrasonically cleaned and subsequently abraded by a screw in organic solvents and water. The TPPE apparatus is composed of a Geiger counter with Q gas (He+ iso-C4H10). The curve of photoelectron emission (PE) intensity vs. wavelength from 300 to 170 nm, termed PE spectrum, was repeatedly measured at different temperatures in the temperature- increase process from 25 to 350°C. The number of emitted electrons in a PE spectrum (PE total count) increased, reached a maximum at-250°C, and decreased with increasing temperature. With the surfaces cleaned alone in the liquids the maximum PE total count decreased in the order C3H70H > (CH3) 2CHOH > C2HpH > CHPH > H2O. With the mechanically abraded surfaces in the liquids the maximum PE total count changed as a function of the abrasion period and the maximum tended to appear at higher temperature with increasing abrasion period; the maximum value at 10-min abrasion decreased in the order H2O > CHpH > C2HPH > (CH3) 2CHOH > n-C3HpH. It was suggested that the TPPE behavior can be related to the acid-base interaction between the alcohols and the abraded metal surfaces and the presence of a contaminant over layer on the surface. From the XPS analysis of the 01 s spectra it was suggested that the chemical change of the adsorbed oxygen to oxide oxygen with temperature plays a substantial role in the appearance of the maximum PE total count.

Jan 1, 2000

By Igor Rojkovic

The most important uranium mineralization in the Western Carpathians occurs in the Permian rocks. Low grade stratiform uranium mineralization was formed during the Permian due to adsorbtion and reduction by organic matter, titanium oxides, iron hydroxides, pyrite and clay minerals. During the Alpine orogeny uranium (± molybdenum and copper) remobilized stratabound ores were formed. Dominant ore minerals are uraninite, U-Ti oxides, molybdenite, pyrite and chalcopyrite Two generations of ore minerals are reflected by their textures and chemical composition.

Jan 1, 1995

By Aureo D. V. Machado

An experimental study to obtain zirconia powders (ZrOz) from carboxylate zirconium solutions followed by hydrogen peroxide stripping and precipitation, has been carried out. Zirconium carboxylate was prepared by solvent extraction from a chloride aqueous phase using magnesium carboxylate as organic phase. The variables examined in the precipitation reaction were: Temperature: 25 - 90 ?C ? H202= concentration: 0.3 - 5% wt/wt - pH: 1 ? 9 Organic/Aqueous ratio (1/1) and reaction time (30 minutes) were maintained at constant levels. The optimum results (98% precipitation) were achieved at 25 °C, 5 % wt/wt H202=, and pH = 5. The precipitates were composed of large amorphous aggregates (<I00 micrometers). After calcination for 1 hour at 1000 OC, monoclinic ZrO2 with a large variation in particle size (1 -100 micrometers) was obtained.

Jan 1, 1991

By Takahiko Okura

Japanese non-ferrous industry introduced large-scale smelting plants along seashores for overseas concentrates with increasing demand of metals around 1970s. Although serious environmental pollution became obvious, with economic growth, the industry got rid of pollution by installing new processes and improving operation technologies. At present, over 99.8% of sulfur input to smelters is fixed as stable compounds. Through those decades Japan had steep rises of oil prices, sudden change of exchange rate, and inadequate treating charges, we were faced to consider the closure of smelters. The industry has survived by increasing productivity, saving energy and reducing manpower. Furthermore the industry made great effort to recycle valued metals from scraps and wastes for the resources-recycling society. Academic research also contributes to support these individual technologies. Thus the industry has fostered world-acclaimed technologies in terms of efficiency and energy conservation. This paper presents technology development and environmentally-benign sulfide smelting processes.

By Yongxiang Yang

High temperature processing of raw materials in metals production and recycling often involves complex multi-phase fluid flow and heterogeneous chemical reactions at various scales. Good understanding of the process physics and chemistry is crucial for process operation and process development. The traditional scale-up process through laboratory scale ? pilot scale ? commercial scale route has been more and more complemented and partially replaced by full-scale process simulation. Computational fluid dynamics (CFD) has become a very useful simulation tool in process research and development. At the same time industrial applications challenge the CFD development with its complex transport phenomena, often in large-scale reactors with small-scale physics and chemistry. The current paper discusses the applications of CFD to a number of high temperature metallurgical and materials processing applications. The research was carried out by using commercial CFD codes as the framework, and the emphasis was given to the special efforts for the development and implementations of sub-models with process-dependent physical and chemical characteristics. To illustrate the application of CFD simulation to high temperature metallurgical processes and coupling of sub-models to the general-purpose CFD codes, five examples are given: (1) melting of aluminium scrap in a rotary furnace for recycling, (2) molten hot metal flow in a heterogeneous coke-bed of a blast furnace hearth, (3) gas flow heat and mass transfer in a submerge electric arc furnace for phosphorus production, (4) high temperature incineration of hazardous waste in a rotary kiln, and (5) transient heating of metals in heat treatment furnaces.

Jan 1, 2006

By M. C. Ruiz

The conventional pyrometallurgical methods to treat copper sulfide concentrates include generally, one or more oxidizing steps where the formation of SO2 gas can not be prevented. From the economical point of view and the nature of some of the processes in which SO2 is produced, its complete capture is not feasible; therefore an important fraction is released to the atmosphere as fugitive emissions. In this research, the reduction of chalcocite was studied in the presence of lime as an alternative method, which overcomes the pollution problems related to SO2 emissions. The effect of temperature, time, concentration of carbon and CaO on the reduction rate were studied. Among these variables, temperature affects most the reduction rate. Conversions over 95 % can be obtained in less that 20 minutes at temperatures over 1000 ° C. The measured partial pressures of the gaseous components indicated that the chalcocite reduction proceeded through the gaseous intermediate species CO, C02, and the overall kinetics was controlled by the Boudouard reaction. The kinetic model In(1-X)= kt fits well the experimental data. Apparent activation energy of 3 14 kJ/mol was calculated for the temperature range of 900 0C-1050 °C.

Jan 1, 1999

By Rongshan Qin, Dengfu Chen, Yan Zhao, Mingtu Ma, Yang Li, Xinming Wan

A two dimensional cellular automaton (CA) model coupled with finite element (FE) method has been developed for simulating the formation of solidified microstructure during beam blank continuous casting, which represents columnar and equiaxed dendrites growth in the case of detailed secondary cooling boundary conditions. In this model, a new adaptive mesh division is proposed to couple CA cubic lattice and irregular FE mesh of beam blank. A double-accuracy liner interpolation method is employed to obtain micro CA temperature field via macro FE calculation. The nucleation process and the velocity of dendrite tip are calculated by continuous nucleation model and KGT model, respectively. Moreover, the preferred orientation of dendrite growth is determined using a probabilistic model. The effects of super heat and casting speed on the microstructure characteristics are analyzed. This model can be applied to optimize processing parameters for beam blank continuous casting basing on microstructure evaluation.

Jan 1, 2015

By F. Chabchoub

A mathematical model has been developed to study the influence of process variables on the horizontal Ohno continuous casting process. The model simulates the heat transfer and fluid flow in a wide plate ingot of pure tin. A two dimensional numerical analysis based on a control-volume finite difference approach, the Semi-Implicit Method for Pressure-Linked Equations algorithm (SIMPLER), and an Enthalpy Transforming Model was used. The shape and position of the solid-liquid interface were calculated at different casting speeds, ingot thicknesses, and cooling device characteristics, as well as various mould temperatures. Results of the mathematical model were compared with

Jan 1, 1992

By Hao Deng, Hongmin Zhu, Jichao Li, Kai Huang

"Silicon and silicon carbide mixing micropowders obtained from the saw cutting industry of polycrystalline silicon ingot is separated by a simple sequential sedimentation. The Zeta potentials of the powders in the aqueous suspension are adjusted by varying the pHs with dilute acid or alkaline reagents. The dispersion and aggregation content of the microparticles is significantly influenced by pHs, and so their settlement velocity in the same hydraulic conditions are quite different, and silicon powders tend to suspend in the upper section of the suspension for its finer size and smaller density under the stronger Zeta potential repulsion force. The original content of the cutting powders with 30%wt silicon are separated into the Si-rich and SiC-rich powder respectively, and 62%wt Si-rich powder can be obtained after 4 times of sedimentation under pH = 8.0, showing the great potential for Si and SiC powder separation and recovery in a cost-effective way.IntroductionWith the fast development of photovoltaic (PV) technology these years, the market demand for the solar-grade high pure silicon material significantly increased, making the silicon recycling and recovery from the wire sawing slurry profitable and attractive[1]. Waste silicon slurry was produced in the multi-wire sawing process of a silicon ingot by using an ethylene glycol-based solution and silicon carbide abrasives as the slicing system. During this slicing process, about 30% of the silicon ingot will become the waste as the fine particles suspended in the slurry, which mainly consists of silicon kerf-loss particles, SiC fragmental particles, tiny iron fragments from the worn sawing wire and ethylene glycol-based solution [2]. The separation of above individual component is usually easy except for Si and SiC fine particles for their quite similar properties. So the biggest challenge for the effective recovery and recycling of silicon particles from the wire sawing slurry actually lies in the mutual separation of silicon and silicon carbide particles."

Jan 1, 2012