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By S. Peng, Vaughan R. Voller

"Free boundary problems are a common occurrence in materials processing operations. An important example is the filling of material into molds. This paper looks at filling problems associated with polymer processing, in particular Resin Transfer Molding (RTM) and Compression Molding. A general, single governing equation is developed which on numerical solution provides predictions for the position of the polymer front in the mold during filling. Both fixed and deforming finite element solutions are developed. Application to polymer filling test problems reveal that the fixed and deforming grid scheme are accurate and compare closely with each other.IntroductionProblems arising from the analysis of material processing operations often involve the tracking of a moving boundary, on which a balance conditions needs to be met, or the locating of a free surface that defines the solution domain. Material processing examples of so called ""free and moving boundary problems"" include; the tracking of solidification/melting fronts[l], the tracking of the metal/gas interface during the filling of a mold[2] and location and shape of a skull (freeze line) in a melting furnace[3].Computational solution of free and moving boundary problems usually fit into one of two classes, viz.1. Fixed grid scheme: In which the spatial domain is covered by a fixed grid (mesh) of node points and the solution uses an auxiliary variable (e.g. a local liquid fraction) to track the moving boundary or locate the free surface.2. Deforming grid scheme: In which the grid in the spatial domain is continuously deformed (or adapted in a steady state problem) such that a specified set of grid points lie on the moving boundary or the free surface.Details on the basic underlying features in these two classes of solution can be found in the excellent monograph by Crank [4]."

Jan 1, 1994

By Patrick R. Taylor

Coatings of TiCIFe have been produced by Reactive Plasma Spraying using ilmenite ore concentrate as the feedstock powder and methane as the reactive gas. A free energy minimization analysis of the ilmenite-methane system is presented. The coatings have been characterized by x-ray diffraction and SEM. The microstructure of the coatings indicates good interparticle cohesion. The composition of the coating is deficient in iron compared to the initial Fe to Ti ratio found in ilmenite.

Jan 1, 1998

By L. Lü, M. O. Lai

"Mechanical alloying is a dry, high energy ball milling process which has been used to synthesize metallic powders in the solid state. The present study use this technique to synthesize Cu-base shape memory alloy powder from commercial Cu70Zn30, Cu86Zn14 and element AI powders. The evolution and formation of shape memory alloy powder were monitored using X-ray diffraction and microscopy. It was observed that shape memory alloy powder started to form after 1.8 ks of mechanical alloying. ? phase was clearly detected after 3.6 ks of mechanical alloying. The intensity of X-ray diffraction of the y phase increased when mechanical alloying duration was prolonged indicating an increase in the amount of y phase. Microstructure observation showed different stages of formation of alloyed powders: welding between powders and formation of layered structure, deformation and fracturing of layered structure, and finally the formation of alloyed powders.IntroductionMechanical alloying (MA) is a process used for producing powders with controlled and extremely fine microstructure. It was original developed in 1966 (1) to produce aNi-based superalloy combining oxide dispersion strengthening with gamma prime precipitation hardening. In recent years this technique has been used in producing a wide range of materials including intermetallic compounds (2, 3), amorphous materials (4-6) and other materials (7-9). In MA, a blend of powders is subjected to highly energetic compressive collision. The powder panicles are welded and fractured during ball milling. Therefore, it is essential that at least one of powders should be ductile to act as combiner. It has however been found that brittle components without soft element can also be mechanically alloyed (10), even ceramic powders (11).The present work aims to study the mechanism of formation of shape memory alloy powder during MA."

Jan 1, 1994

By Drew Sinha

Success of the environmentally benign semiconductor manufacturing depends on the cost-effective integration of the principles of reduce, recover, reuse and recycle from source material to final product disposal. Increasing demand combined with current shortage of polysilicon provided unique opportunities to recover the silicon waste, caused by various defects, in wafer manufacturing process. Current practices relating to recovery and reuse of waste silicon produced, from crystal growth process to finally polished and epitaxially deposited silicon wafer, at Mitsubishi Silicon America is presented. Future plan to recycle the process generated silicon fines produced during the intermediate steps of the wafer manufacturing process such as grinding, slicing, lapping and polishing is also discussed.

Jan 1, 1998

By A. M. Strachan

The application of submerged electric arc furnace smelting techniques to tin concentrates at the Capper Pass tin smelter in England is discussed. Some experimental data from earlier small scale 50 KVA electric smelting testwork on various low and medium grade tin concentrates is presented. Design considerations for the construction of a 3 MVA electric furnace to treat tin concentrates from the East Kemptville mine in Canada are considered, together with necessary precautions peculiar to the construction of a high grade smelter in close proximity to an existing low grade, complex non-ferrous metal smelting operation<. Slag composition modifications to optimise operational smelting conditions for various concentrates treated are discussed, together with refractory selection. The effect of concentrate impurity levels on the permissible degree of recycle to produce a satisfactory metal product is highlighted.

Jan 1, 1990

By Milorad Cirkovic

Kinetics of copper concentrate oxidation in roasting processes in a fluidized bed reactor has been studied at temperatures between 600°C and 720°C using particles of 0.038 to 2.5 mm in average size. The analysis of composition of samples has been done by chemical methods. Phase composition has been determined by Siemens X-ray equipment with Cu anticathode and Ni filters at a voltage of 40 kV and a current of 18 mA. The content of sulphur has decreased from 33.23 to 19.02 mass percent with the increase of temperature, but the content of Fe304 has increased from 0.15 to 17.14 mass percent. The new mechanism of copper concentrate oxidation in a fluidized bed reactor is proposed in this study. It has been shown from the mathematical model that the velocity of oxidation of copper concentrate between 600°C and 720°C is virtually controlled by the rate of diffusion of 02 through the layer of reaction product.

Jan 1, 1999

By J. H. Ahn, J. K. Yoon, Jung-Eui Lee

"A concentration change during grade transition operation in steel thin slab casting is predicted with computer simulation, water model and plant trial. Fluid flow and mixing patterns in various tundish levels and flow rates were analyzed through three-dimensional mathematical modeling. Comparing with water model experiments, a simple, efficient and accurate computational model has been suggested to predict the concentration profile at outlet of tundish. Based on the model, mixing in/below the mold was analyzed considering EMBR. The predicted concentration profiles show good agreements with the measured values. It is found that the lower vortices in the mold are suppressed by the electromagnetic field and the plug-like flow region develops which decreases the intermixing of two different grades of steel and shortens the length of transition region.1. IntroductionContinuous casting is the primary mode of production of semifinished steel products as it offers tremendous advantages in terms of energy savings, increased yield and higher productivity over the traditional ingot casting process. Efforts have to be made constantly to improve the quality of the cast product, reduce costs and thus increase the competitiveness of the steel manufacturer. One way of reducing costs is to reduce the amount of intermixed steel during the grade transition operation.Several different procedures exist to handle the casting of dissimilar grades for the conventional slab casting. Each procedure has its own merits and demerits. In order to choose the best method for a particular operation, there are a lot of researches. In the case of present continuous thin slab casting of POSCO mini mill, the only possible method is to change ladle during the grade transition. Due to the high casting speed (3.8m/min-4.4m/min) it is impossible to change the tundish and due to the thin thickness of slab it is also impossible to insert grade separator."

Jan 1, 2000

By R. L. Player

"The Copper Isasmelt process has been developed over the past 15 years by Mount Isa Mines Limited (MIM) and the Commonwealth Scientific and Industrial Research Organisation (CSIRO). The first two commercial plants were commissioned in mid 1992.The results of four heat balances on the Mount Isa plant are presented. At a smelting rate of 98 t/hr of chalcopyrite concentrate plus 14 t/hr reverts, the total heat generated was -91MW. Approximately 39% of this energy came from coal, while 50% of the energy reported to the process waste gas. To a first approximation the furnace is near chemical equilibrium.The impurity distribution in the Mount Isa plant was presented. Approximately 91 % As, 85% Cd, 75% Bi, 68% Zn, 60% Sb and Tl, 45% Pb and 30% Te in concentrate was eliminated from the matte.The ""bubble"" frequency of the gas cavity below the foot of the lance was measured at -2. 1Hz. Side bands displaced by -l.lHz modulated the bubble frequency. This was consistent with radial gravity wave motion in the slag bath. The two processes, gas bubbling and wave motion appeared to be coupled together; the bubble frequency was twice the slop wave frequency. IntroductionCopper Isasmelt has been developed over the past 15 years by Mount Isa Mines Limited and the Commonwealth Scientific and Industrial Research Organisation. The process is based on the Sirosmelt lance, invented by researchers at the then Division of Mineral"" and ProcessEngineering ofCSIRO in 1973.The first two commercial scale copper furnaces were commissioned at Mount Isa and the Cyprus Miami Mining Corporation smelter at Miami, Arizona in August and June 1992 respectively.The process concept, the history of the development, and the Mount Isa plant have been described (1, 2, 3).This paper sununarises heat balances obtained on the furnace, the impurity distribution among the output streams and lance injection characteristics."

Jan 1, 1996

By Hector Carreon

This paper presents experimental data for the magnetic field produced by thermoelectric currents around uncracked hard-alpha inclusions in a Ti?6Al?4V specimen under external thermal excitation for different nitrogen content ranging from 1.6% to 5.9%. According to our preliminary results, the magnetic flux density measurements were found to be rather sensitive to changes in nitrogen content with the exception of the intrinsic material background magnetic signal that affected deeply the detectability of inclusions and imperfections in non-contacting thermoelectric measurements. Hopefully, these preliminary results can help identify a non-destructive test method that can detect material inclusions with a level of nitrogen that could be detrimental to Ti?6Al?4V alloy components.

Jan 1, 2009

By Jaroslav Horskoý, Miroslav Raudenský, Bogdan Filipic, Božidar Sader

This paper describes main elements and practical use of the computational system for automated setting of optimized casting conditions in the continuous casting of steel. The system consists of the heat transfer model of the process, empirical metallurgical criteria, and optimization algorithm. The physical model of the, strand temperature distribution relies on the classical Bennon-Incropera mixture continuum formulation for the convective-diffusive heat transport. Fluid flow effects are considered through enhanced thermal conductivity of the liquid phase. The model is solved by the operator-splitting Crank-Nicolson finite volume version of the Voller-Swaminathan scheme. The solution procedure is coupled with the IDS solidification analysis package. Boundary conditions for the strand cooling rely on combination of the generic and plant-specific mold, spray, and roll heat transfer coefficients ' by coping the effects of the casting speed, casting temperature, casting powder, mold oscillation mode, steel grade, water or air-mist spray type, running water, trapped water on the rolls, and radiation. The caster safety and productivity and the quality of the strand are related to nine empirical metallurgical criteria. The criteria ensure the caster safety and economy as well limit the internal, longitudinal, and transversal surface cracking possibility. The problem of finding optimum casting parameter values is stated as a minimization problem based on the analytical form of the cooling criteria evaluated from the steady-state temperature distribution of the strand. To solve the optimization problem, a genetic algorithm is employed. The algorithm explores process parameters settings heuristically by applying the principles of biological evolution. It starts with a random set of solutions and iteratively improves them through selection and variation. Solutions are evaluated by running the heat transfer model of the process and extracting the values of the empirical metallurgical criteria.

Jan 1, 2000

By Liu Wei-feng

In this paper, the practice of separating precious metals from base metals in gold-antimony alloy by selective chlorination leaching under controlling potential in China has been introduced in detail. The precious metals and the base metals can be separated completely when the complex gold-antimony alloy is treated by this process. The impurity metals were removed effectively since the leaching efficiencies of copper, nickel and antimony are over 99%, with direct recovery of gold being 99.83% that is about 20% higher than that of the original process and silver, antimony, copper and nickel are also recovered effectively. The gold grade of the resulting crude gold powder can reach to 94%.The new process has been applied in the treatment of gold-antimony alloy for two years, and many former procedures have been cancelled, such as electrolysis, Anode slime leaching by nitric acid, smelting in crucible and blowing in muffle. The new process is more shorten, lower cost and friendly to the circumstance comparing to the original process.

Jan 1, 2008

By Baozhong Zhao

Laboratory experiments have been conducted on the removal of As, Sb and Bi from molten copper by SF 6 injection. The results showed that the impurities can be removed by SF6 injection in the? sequence of Sb >As >,Bi and the rate of Bi removal is affected significantly by the concentration levels of As and Sb in the copper melt. Analysis of the experimental data indicates that the impurity removal process is under chemical reaction control rather than by mass transfer of impurity through the molten copper phase. On the basis of experimental results, a kinetic model was developed and the order of chemical reaction and the volumetric chemical reaction rate coefficients of impurity removal were determined.

Jan 1, 1996

By Boxun Lu, Juan Wei, Kun Chen, Wanlin Wang, Lejun Zhou

"Slag system is an indispensable part during the continuous casting process, and playing various important roles like absorbing inclusions, modifying heat transfer rate, preventing oxidation of molten steel, etc. to ensure the smooth process and excellent slab quality. However most slags contains more than 8% fluorides which tend to introduce a series of environmental and health problems. This study involves the research of the removal of fluorine through the chemical composition optimization. Through the studies of CCT, DHTT, XRD and SEM, it has been successfully founded that the crystalline phase of Ca11Si4B2O22 discovered in this study shows very similar crystallization property as Cuspidine (Ca4Si2O7F2), which is the most important crystalline phase in the current fluorine bearing slags. Moreover, the optimized free/low fluorine slag shows the opportunity to replace conventional high-fluorine mold slag for casting medium carbon steels that is regarded as the bottleneck of green slag development for continuous casting.IntroductionMold flux has been widely used in continuous casting to control heat transfer, lubricate the strand, absorb inclusions, provide insulation and prevent oxidation of the molten steel[1-3]. It usually contains fluorides, like CaF2, NaF etc., which are used to control the viscosity and solidification temperature of mold fluxes [4-5]. However, the presence of fluoride leads to corrosion of equipment, serious environmental pollution (toxic volatiles and water pollution), and high processing cost of cooling water[6-7]. Therefore, the study of low or free fluorine mold flux is of interest and attracts worldwide attention.S. Y. Choi et al. [4] used B2O3 as a substitute for cuspidine in steel B2PB2) however, B2O3 content was extremely high (up to 30 w%). Other studies have investigated F-free mold flux by adding or optimizing components as MgO, Li2O, B2O3 et al[8-11]. However, most of these focused on the melting and viscosity issues or for low or ultra-low carbon steels, where crystallization tendency is not significantly strong. Very few studies regarding to the development of low/free Fluorine mold flux for casting medium carbon (MC) steels have been conducted, due to the difficulty of the crystallization and heat transfer control without the formation of cuspidine."

Jan 1, 2014

By Tianzu Yang, Weifeng Liu, Lin Chen, Qingkai Xiao, DUCHAO ZHANG

To solve the problem of low leaching ratio of direct gold cyanide leaching from arsenical refractory gold concentrate, this paper proposed a matte smelting process for gold enrichment in low grade copper matte. The effects of copper content in the mixed material, ratio change in slag type, smelting temperature and reaction time on recovery rate of gold and copper were investigated. The experimental results indicated that the recovery rate of gold increased with the increase of copper content in the mixed materials, temperature and reaction time. It was also noted that the recovery rate of gold and copper were respectively 98.16% and 96.39% when the addition of copper content in the mixed material was 3%, slag type of CaO/SiO2 and FeO/SiO2 were 0.6 and 0.9 in 1250°C and the time of reaction was 40min. Most of the arsenic was oxidized into As2O3 existed in the dust. The results showed that the matte smelting method can achieve efficient recovery of gold from arsenical refractory gold concentrate.

Jan 1, 2016

By William Petruk

The concentrator of the Iron Ore Company of Canada consists of spiral circuits, a cone plant and a magnetics plant with regrind. The proportions of liberated and unliberated grains of iron oxides at each point throughout the concentrator were measured by image analysis, and recoveries were calculated for each particle type by the MATBAL materials balancing program. The results show that spirals and cones recover more than 92% of the liberated iron oxide grains in the size range of 848 to 150 um,, but the recovery drops off rapidly for finer grained particles. The tailings from the spirals and cones are reground and low intensity magnetic separators are used to recover liberated magnetite in the -37.5 um size range. The concentrator does not have a unit that efficiently recovers iron oxide grains in the size range of 150 to 37.5 um Consequently about 25% of the iron oxides in the ore are lost to tailings as liberated. grains in the size range of 150 to 37.5 um

Jan 1, 1989

By M. Y. Mohassab-Ahmed

In an effort to develop a novel flash ironmaking process, the chemistry of selected slags was investigated. In different ironmaking processes, the molten bath (iron-slag bath) is expected to be in contact with gas atmospheres of H2/H2O, CO/CO2/H2/H2O, and CO/CO2. The latter was investigated to allow comparison with the blast-furnace conditions. The slag composition was selected to resemble that of the blast furnace with CaO/SiO2 in the range 0.8 to 1.4. The temperature range was 1550 to 1650°C. The oxygen partial pressure was maintained in the range 10-10 to10-9 atm. The effect of water vapor on the chemistry of the slag as well as the equilibrium reactions involving the slag has been studied for the first time. H2O dramatically affects the chemistry of the slag and strongly affect the phase equilibria in the slag as well as the equilibrium distribution of elements between slag and molten metal.

Jan 1, 2014

By José D. T. Capocchi

Viscosity of liquid lead, tin, and Pb-Sn alloys has been measured by the rotational viscometer method in the temperature range from 50 K above their respective liquidus temperature to 823 K. The results are accurate to within ±1.0 %. The variation of viscosity with temperature followed the Arrhenius-type equation µ = µo.exp(Q/RT). The composition dependence of the isothermal viscosity and the activation energy for viscous flow have not shown anomalous changes at the eutectic composition of the Pb-Sn system.

Jan 1, 2000

By Jonkion M. Font, Ramana G. Reddy

A thermodynamic model for a priori predictions of arsenic and antimony impurity capacity in Ni-Cu mattes and slags was developed based on the Reddy-Blander (RB) capacity model. The As and Sb capacities were calculated a-priori considering the RB capacity model in Ni-Cu mattes and FeO-FeO1.5-MgO-CuO0.5-NiO-SiO2 slag at 1573 K and 0.1 to 1 atm partial pressure of SO2. The results showed an excellent agreement between the model calculated and experimental data of arsenic and antimony capacities between the mattes and slag. The impurity capacity model developed here, can be extended for prediction of impurity capacities in multi-component base metal slags and base metal mattes. Such a priori predictions of impurity capacities can lead to develop or improve the efficiency of impurity removal from the base metal smelting, converting and refining processes.

Jan 1, 2014

By B. C. Jena

Activities of carbon, cobalt and nickel were evaluated in the ternary systems iron-carbon-cobalt and iron-carbon-nickel for the temperature range 1300-1600°C for cobalt and 1300-1700°C for nickel. The carbon activities were determined from the knowledge of activities (1) in the binary system iron-carbon, (2) in the dilute ternary systems and (3) from the knowledge of carbon saturation data. The activities were mathematically expressed with the Taylor series expansion of Wagner&apos;s interaction parameter formalism modified to suit concentrated solutions. The cobalt and nickel activities were determined from the knowledge of carbon activities by applying the Gibbs-Schuhmann integration and from cobalt and nickel activities in the binary systems iron-cobalt and iron-nickel. Partial molar enthalpies of mixing were determined based on the temperature behaviour of the activity coefficients.

Jan 1, 1992

By E. Allain

Extraction of basic metals from sulfides by conventional pyrometallurgical processing leads to the emission of SO2. To avoid this inconvenient, low temperature selective chlorination of sulfide concentrates could be an alternative. However, such process generates hazardous chlorides SxCly. A part of sulfur chlorides such as SCI2 can be recycled as a chlorinating agent of metal sulfides. Hydrolysis of sulfur chlorides, using a solution containing Na2S.9H2O, led to the recovery of more than 90 pct of elemental sulfur. Reduction of SxCly by hydrogen was investigated between 300 °C and 800 °C. About 70 and 90 pct of elemental sulfur were recovered from SC12 and S2C12, respectively. A flow sheet for the chlorination of metal sulfides and the treatment of sulfur chlorides was suggested.

Jan 1, 1998