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By F. Ajersch, P: Tsantrizos, K: Shanker

"TiN films have been deposited on various substrates by a novel reactive plasma technology. In this process, a nitrogen source (NH3 or N2) and TiCl4 are reacted in the jet of a plasma torch, and are deposited onto a substrate forming TiN films at a high growth rate ( > 2µm/min). It was found that the process parameters strongly affect the microstructure, thickness, density, and growth rate of the TiN films. These parameters include source of nitrogen (NH3 or N2, N/Ti ratio, temperature of substrate, and spray distance. In general, it was found that thick and dense coatings were deposited when the N:Ti ratio was kept low, and the substrate temperature was high. Also, for the series of conditions investigated, NH3 was found to give much better results than N2•. The limitations and advantages of this technique are also discussed in this paper.IntroductionTiN is an extremely hard material and is used in many wear applications, particularly as a protective coating on cutting tools to extend their Iife(1.2). Owing to its excellent chemical stability, TiN is also frequently used as a diffusion barrier in the electronics industry for sub-micron Al/TiN/Si ohmic contact systems (3) or as a coating on high-temperature resistant alloys in gas turbine applications (4), based on its good resistance to oxidation. Other applications include decorative coatings in the jewelry industry, and specialized applications such as solar energy absorbers and transparent heat mirrors(5).TiN films can be deposited/formed using various techniques. The main techniques of deposition are CVD (Chemical Vapour Deposition) and PVD (Physical Vapour Deposition). Each of these techniques can have many variations in equipment characteristics, reactants as well as a range of process parameters (pressure and temperature). In the CVD process, TiN is generally deposited onto a heated substrate where a chemical reaction takes place. The reaction can be one of reduction(6) (e.g.: TiCI4 + 0.5N2 + 2H2 --> TiN + 4HCI), of thermal decomposition(7) (e.g. decomposition of titanium dialkylamide), or of displacement (e.g. TiCI4 + NH3 --> TiN + 3HCI + 0.5CI2)' The displacement and reduction reactions are the most common."

Jan 1, 1994

By P. A. Manohar

This paper describes an implementation of the Potts model for simulation of grain growth in 2D on a distributed-memory parallel architecture. The simulation scheme utilizes a continuous-time, asynchronous parallel version of the n-fold way algorithm. Each Processing Element (PE) carries a piece of the global simulation domain while the virtual topology of the PEs is in the form of a square grid in 2D and Torus in 3D. Different PEs have different local simulated times. Inter-processor communication is carried by the Message Passing Interface (MPI) routines. Sample results for grain growth simulation in 2D are presented for a 840 x 840 global domain size distributed over 16 PEs. The grain growth kinetics obtained in the simulation of pure, isotropic systems is in good agreement with the theory. Grain size distributions obtained in the parallel simulation are well described by the lognormal distribution, thus validating the simulation procedure. Keywords: Metropolis algorithm. n-fold way algorithm, asynchronous parallelization, grain growth

Jan 1, 2003

By Lv Guozhi, Niu Liping, Liu Yan, Zhang Zhiqi, He Jicheng, Zhang Ting’an, Dou Zhihe

"CuCr alloy can be extensively used as contact materials in integrated circuit, electrodes, electric contact and high strength conductor. We proposed thermit reduction-electroslag remelting method of preparing the large scale CuCr alloy. But there are pores and oxide inclusions in CuCr alloy prepared by thermit reduction process. This paper studied mainly the effects of ratio of reactant and additive on the inclusion type and their occurrences in CuCr alloy. The slags and CuCr alloy were characterized respectively by XRD and SEM. The results show that when the additive is Na3AlF6, the slag consist of Al2O3 and Cr. When the additive is CaF2, the slag consist of Al2O3, Cr, CaF2 and CaAl4O7. The inclusions in CuCr alloy are mainly Al2O3 and pores which disperse in Cu-rich zone and Cu-Cr phase interface. When 5% CaF2 and 5% KClO3 are added, there are fewer pores and inclusions, and the more better microstructure.1 IntroduceCuCr alloy is the contact terminal material with an eximious properties[1,2], which gradually replaces CuBi alloy becoming the first choice for contact terminal material in the medium and high power vacuum switch after the 1970s. The traditional preparation methods of CuCr alloy mainly contain powder metallurgy, infiltration process and vacuum electric arc melting methods. But the above methods exist some shortcomings, such as poor product quality, high cost of production, processes complex ect[3-9]. CuCr alloy is made by the thermit reduction self-propagating method, which uses CuO, Cr2O3 and Al as raw material to get the high-temperature melt, and then casts to manufacture CuCr alloy ingot, which response equation follows as:"

Jan 1, 2012

By M. Wu, A. Kharicha, A. Ludwig

"The droplet formation during melting of a 400 mm diameter electrode is simulated with a multiphase-MHD approach. The computational model includes a layer of slag and a layer of liquid steel. A VOF approach is used for the interface tracking and a potential formulation is used for the electric and the magnetic field. The Lorentz force and the Joule heating are recalculated at each time step in function of the phase distribution. The first results provided by this model are presented.IntroductionThe Electro-Slag-Remelting (ESR) process is an advanced technology for the production of components of e.g. high quality steels [ 1-9]. An alternating current (Figure 1) is passed from a conventionally melted and cast solid electrode through a layer of molten slag to the baseplate. Because of the electrical resistivity of the slag, Joule heating is generated and the slag transfers this energy to ingot and mould surfaces and to the melting electrode tip. The molten metal produced in the form of droplets passes through the slag and feeds a liquid pool from where directional solidification takes place. The slag and the ingot are contained in a water cooled copper mould. As also the baseplate is water cooled, a heat flow regime is imposed that gives controlled solidification, and this results in improved structure characteristics of ESR ingots.This process involves two liquids, a liquid metal and a liquid slag. Each liquid is subject to a phase change due to melting and/or solidification. From a fluid dynamic point of view, the ESR process is clearly a multiphase process, with free interfaces (slag/pool, gas/slag), and with a mixed area (slag and falling steel droplets) [ 10-15].Physically, the development of the heat and mass transfer at the slag/droplet interface is important for the final ingot quality, composition and cleanliness. Visual observations of the droplet formation just under the electrode being melted is almost impossible. Due to the presence of high temperatures, opacity of the materials, and the presence of the mould it is not possible to directly observe the behaviour the slag/pool interface. Although usually assumed flat [1-9], a previous work [10] using a Volume of fluid (VOF) model has shown that the interface shape between a layer of slag and steel layer in a cylindrical cavity is highly coupled with the distribution of the electric current. A full scale simulation of the ESR process using a VOF model has shown that the shape of the pool interface is likely to be non flat."

Jan 1, 2011

By E. J. Peuraniemi

Primary copper production using suspension smelting techniques like Outokumpu Flash Smelting always causes some dust formation. Flue dust particles are formed when sulphide feed material reacts violently with oxygen inducing particle disintegration and total desulphurisation of fragments. In the process, flue dust follows the off-gases to the heat recovery boiler (HRB) where its sulphation takes place because of prevailing conditions. Sulphation releases heat and causes also a drop in particle melting temperature and, further, particle sticking to the walls and heat exchange tube banks. Sulphation of synthetic CU20 particles were examined using a laboratory scale fluid-bed reactor. This study aims to a better understanding of flue dust behaviour in a HRB and, thus, to a better operational practise and design of a HRB. The effect of PSO/PO2 -ratio and temperature on the sulphation kinetics were tested. Standard chemical analysis, light optical and scanning electron microscopy with energy dispersive spectroscopy were used to examine the samples.

Jan 1, 2001

By Bogdan Petkovic, Boban Todorovic

In the early 90's a completely unknown problem was encountered at the converter Department: it was a chronic shortage of the cold copper charge needed for the second operating period. A high temperature operating regime was caused which further provoked a chain of consequences such as a drastic drop of the number of operations in campaigns. The consumption of repair bricks reached the quantity of 8.3955 kg / tonne of anode Cu. In 1994, we won the process of cold material smelting during the "copper" blowing [2]. The number of operations per campaign reached 180-200 again. Also in 1994 we won the process of smelting cold materials to obtain "tin" blowing with the purpose of completing their processing cycle [2]. During the period 1994 – 2007 a total of 107,845 tonnes of cold material were remelted to make copper and 56,794 tonnes were re-smelted to obtain "tin". Upon synthesizing these two processes, a completely new model was achieved in 2005, by Bogdan Petkovic, which entirely utilized all available energy of the Peirce-Smith (PS) converters of the Bor Copper Smelter and now represents the basis of the time cycle. The cold material now enters the converter plant, copper recovery is increased and the method itself is environmentally friendly. 167

Jan 1, 2009

By Kexin Jiao, Zhijia Zhang, Jianliang Zhang, Zhengjian Liu

Carburization behavior of molten iron in blast furnace is an essential part of BF long campaign technology. Maintaining carbon content stable is an important prerequisite to ensure the high production of the blast furnace. In this paper, the important aspects of the research progress which mainly including the study of iron carburization at the upper and the lower parts of the blast furnace was reviewed. Indirect carburizing is the main way at the top of the blast furnace. The content of carbon in metallic iron increases with the reducibility of iron ore improved. The thermodynamics and kinetics conditions are good for carburization reaction to take place at the bottom of the blast furnace. Carbon content of molten iron increased by coke carburizing. Meanwhile, the drawbacks of the existing literature on iron carburization behavior were analyzed and new research directions of iron carburization were proposed in the future.

Jan 1, 2015

By N. Voennann

Stillwater Mining Company operates an electric furnace at its smelter in Columbus, Montana to treat a Ni-Cu-platinum group metal concentrate along with secondary PGM bearing materials. Hatch Associates has designed several improvements to this furnace, which was originally built by others. Implementation of these relatively low cost improvements has resulted in substantial increases in furnace availability and capacity, along with reduced unit costs. ? The improvements included: ? Installation of water-cooled copper cooling elements to stabilize refractory wear and increase furnace life.- ? Improved furnace 'bindings, to enhance the furnace's structural integrity by improving the contact between the refractory and cooling elements, and by promoting tight brick joints resistant to matte or slag leaks. ? Adjustment of the electrode regulator to allow higher furnace power levels. ? Installation of an automated air-slide (aeration conveyor) feed system to evenly distribute the furnace feed in an insulating layer on the bath surface. This "black-top" practice reduces unit energy costs and makes available additional smelting capacity.- ? Electrode seals to reduce ingress of air that absorbs heat before exiting the furnace in the off-gas stream. The saved energy can be used to smelt additional concentrate. This paper describes the above furnace modifications, and the benefits derived from their implementation.

Jan 1, 1998

By John A. Herbst, William T. Pate

"Plantwide control of mineral processing operations has long been sought for its potential benefits. These benefits include minute-to-minute optimization, reacting to disturbances in ore characteristics and equipment status as they happen, and the coordination of all unit operations in pursuit of the highest performance level. However, several difficult challenges have kept us from fully realizing those benefits. One of these challenges has been to provide fairly complete quantitative descriptions of unit operations to account for critical interactions within and between unit operations. In some cases we understand the physics and chemistry very well and can incorporate that knowledge into phenomenological models. In other cases our knowledge is incomplete, so we must rely on other forms of knowledge such as fuzzy logic or neural nets. Another challenge to be met has been to simultaneously compute a large number of manipulated variables. In the past this challenge was met by optimizing only unit-by-unit, rather than on a global basis to significaritly reduce the number of variables. In this paper, a procedure that globally optimizes one or two important variables is outlined. This procedure comes much closer to true plantwide optimizing control while remaining computationally feasible. Finally, another major challenge is to choose a meaningful global objective that can be calculated with the models and can be effectively optimized. Financial goals seems to be the objectives of choice.This paper discusses recent progress in overcoming the challenges and illustrates a promising approach which is being pursued at Mexicana de Cobre's La Caridad copper ore concentrator. At M de C, advanced control strategies have been installed one at a time in the crushing, grinding and flotation sections. During this period, the throughput of La Caridad, Mexico's largest copper concentrator, increased from 76,000 tpd to 90,000 tpd. Plantwide integration is expected to gain an additional 3% improvement in profitability."

Jan 1, 1996

By Fathi Habashi

Nitric Acid has been used for over 50 years in the uranium industry and in phosphate fertilizer manufacture. Its application in the treatment of sulfide concentrates is relatively recent. A review of recent developments is given.

Jan 1, 1999

By T. Shoji

"The human history is characterized by social development based on mineral and energy resources, and many conflicts to take the resources by power. This is shown by not only world wars but also many local conflicts as well as international supremacy.IntroductionThe world population after B. C. 10000, which is summarized in several papers, is approximated by four straight lines on a semilogarithmic diagram as shown in Figure 1 [l]. The annual rates of increasing are 0.0041, 0.071, 0.53, and 1.85 % from the old and young periods. The boundaries among four periods are approximately B. C. 4600, AD. 1670, and 1930. The start of the second period seems to correspond to the beginning of agriculture and cattle breeding. Precisely speaking, the usage of natural energy resources such as woods and domestic animals already began, but is inferred to have become common after the age. The third and fourth periods are characterized by the common usage of coal and oil, respectivety. Not only energy resources but also mineral resources including gold, copper, iron and others are also important for the human history.Mineral and energy resources have supported the development of the .human civilization, and have caused many conflicts because of this reason. Every day newspapers report conflicts, such as Chechnya, East Timor and Ache. We can easily point out the facts that the conflicts closely relate to mineral and energy resources. Groznyj, Capital of Chechnya, is located on the western margin of Caspian oil field. Many mineral deposits occur in Kavkaz Mountains running south of Chechnya. Subsea oil fields occur in Timor Gap located between East Timor and Australia. Ache is also one of oil fields in Indonesia. It is very difficult to state present conflicts independently of a political view of point. For this reason let us try to historically review the relation between mineral and energy resources and international domination and conflicts [2] based on many papers [3]."

Jan 1, 2000

By Abbas H. Mirza

Arsenic and selenium are found in low quantities together with other metals in several nonferrous metallurgical process streams such as scrubber blowdown solution, acid plant wastewater, gas cleaning plant water, etc. Normally, the other metals in these streams are present as cations and can be precipitated by conventional lime treatment and sulfide polishing. However, arsenic and selenium are invariably present as anions, AsO33-and AsO43 in the case of arsenic and SeO32 and SeO42 for selenium. Conventional lime treatment removes most of the arsenic, but it does not remove selenium. The present paper reviews the processes and technologies developed to date on the removal of arsenic and selenium from metallurgical process streams.

Jan 1, 1996

By J. K. Brimacombe

Plant trials have been conducted at the Tacoma Smelter of ASARCO to assess the effect on tuyere blockage and refractory erosion at the tuyere line, of increasing the injection pressure of air into a Peirce-Smith con¬verter. Four tuyeres each having an ID of 19.1 mm (3/4 in) were installed toward one end of the tuyere line of the No. 4 Converter. Air and oxygen-enriched air were injected at 414 kPag (60 psig) through these tuyeres and at the usual 83 kPag (12 psig) through the remainder of the tuyeres in an otherwise normal converter campaign. The test campaign consisted of 88 charges and lasted for 89 days. During this period, punching of the high-pressure tuyeres was found to-be unnecessary; and when, as a precaution, the tuyeres were cleaned by hand at the end of a charge, they were always open. Also it was observed that the flow of high-pressure air remained constant. Accretion formation around the tip of the high-pressure tuyeres varied from charge to charge and was influenced by the matte grade and the level of oxygen enrichment.

Jan 1, 1983

By R. Schuhmann

The thermodynamic data and calculations which underlie the design of the Q-S process for coppermaking are summarized. The efficient production of crude copper and slag of low copper content in a single con¬tinuous converter requires the establishment and control of gradients in oxygen activity and other physico-chemical variables throughout the reactor. These gradients are established by stagewise introduction of oxygen and solid feed materials to provide: (a) flash oxidation of sulfides above the bath, utilizing the great bulk of the oxygen, (b) conversion of high grade matte or white metal to crude copper by bottom blowing with restricted bath turbulence, (c) close approach to equilibrium staging of converting and deconverting reactions along the length of the slag layer, from a maximum oxygen activity near the metal discharge end to a minimum at the slag discharge end, and (d) completion of slag cleansing by deconverting. In terms of the Phase Rule, the Q-S process involves a system with a minimum of 5 components (Cu, Fe, S, O, and SiO2) and several liquid, solid, and gaseous phases. Accordingly, basic data from previously reported studies on simpler systems are utilized to prepare an equilibrium diagram for the 5-component system and to generate a quantitative thermodynamic model for the Q-S process. This model shows in particular the ranges of oxygen activities (measured by equivalent CO2/CO ratios) involved in the Q-S process and the relations of oxygen activity to temperature and other important physico-chemical variables of coppermaking.

Jan 1, 1976

By Thomas F. Nederpel

The production of zinc and zinc-aluminum coated strip can be reasonably accomplished on a single operating unit. However, if the hot dip coating line is equip d with only one mo 7 ten metal holding furnace, it is necessary to transfer liquid metal of different chemistries and reintroduce virgin material to obtain the 18" necessary balance of elements in the bath. Dofasco produces Galvanize and Galvalume on a coating line with a sin le liquid metal furnace and has developed not only an efficient liquid metal trans& system but also an effective means of reutilizing the zinc-aluminum mixtures without detrimental quality affects.

Jan 1, 1992

By C. Beckennann, C. Y. Wang

"Computer simulations of structural and compositional development in equiaxed dendritic alloy solidification are performed using a recently developed multi phase model. The model not only accounts for the transport phenomena occurring on the macroscopic (system) scale, but includes also the grain nucleation and growth mechanisms taking place at various microscopic length scales. In this paper, a numerical technique consisting of a fully implicit control-volume based finite difference method and a multiple time step scheme is developed for accurate and efficient simulations of both micro- and macro-phenomena. Sample numerical results are presented to reveal the effects of liquid now and crystal sedimentation on segregation and the final grain size distribution. In particular, the importance of the interplay between the dendrite microstructure and multiphase now patterns is shown.IntroductionIn recent years, modeling of equiaxed dendritic solidification without convection has experienced considerable progress (1,2]. Nucleation and growth kinetic laws have been coupled with transient heat conduction calculations to determine the solidification microstructure. However, modeling of equiaxed dendritic solidification with melt convection and solid movement has not been attempted so far, largely because of the complications associated with the transport of free equiaxed crystals in the melt. The gravity-induced transport of free crystals is fundamental to the development and extent of the equiaxed zone and also greatly affects the columnar to equiaxed transition. Another possible effect of crystal sedimentation or floatation is to cause severe macrosegregation as well as structural inhomogeneities. The only study available in the literature that accounts for both liquid convection and solid transport is by Ni and Beckermann (3], but deals with globulitic structures (as opposed to dendritic)"

Jan 1, 1994

By Lv Guozhi, Niu Liping, Shi Guanyong, Liu Yan, He Jicheng, Du Yanjun, Dou Zhihe

"We proposed thermit reduction-electroslag remelting method of preparing the large scale CuCr alloy. But there are pores and oxide inclusions in CuCr alloy prepared by thermit reduction process. This paper studied mainly the effects of ratio of reactant and additive on the inclusion type and their occurrences in CuCr alloy. The alloy prepared in different process conditions was characterized via XRD, SEM, OM and TEM and metallographic microscope, in which the existing state and micro-structural defects of inclusions are analyzed. The results show that there are three distinct regions: copper-rich regions, chromium-rich regions and the inclusion regions. Inclusions are mainly in the form of stomata and Alz03 phase, mainly locating in the copper-rich phase and the interface area of chromium-rich phase and the copper-rich phase. Adding Na3AlF6 and heating agent can effectively reduce the inclusion content in the alloy.1 IntroductionIn recent years, with the development ofhigh power vacuum and high-pressure technology ,the CuCr alloy contact material which has many advantages gradually replaced the traditional W-Cu and Cu-Bi series alloy contact material, and become the first choice of material in high-voltage and high-power vacuum switch contacts['-3l. The traditional powder metallurgy method, infiltration method and vacuum arc melting method[4-SJ are using metal Cu powder and Cr powder as raw material by casting molding, and have disadvantages such as high production costs, complicated process, poor product density and low yield, especially in the large size alloy ingots[9-12l. At present, the world regards CuCr alloy new preparation technologies as the first place, and how to achieve a large size the CuCr alloy ingot preparation has become a hot research of CuCr alloy[3l. Zhang Ting-an and Dou Zhihe[l-3l who are supported by national natural science fundation of china successfully successful developed new technologies and core equipment to prepare large-size copper-chromium alloy through aluminum thermal reduction-secondary refining method, and obtained two national invention patents. The method includes two key steps: one is get CuCr alloy consumable ingot by Thermit-SHS with electromagnetic stirring, the other is to refme the CuCr alloy ingot to remove the pores, inclusions and other defects by electroslag remelting technology to get dense and uniform CuCr contact material. The preliminary study results show that means of electromagnetic stirring evidently inhibit effect of alloy ingot macrosegregation during the electromagnetic casting stage, but there are still microstructure defects such as alumina inclusions and pores in the alloy ingots. Therefore, Zhang Ting-an et al refer new ideas of using the electroslag remelting to refine Cu Cr alloy ingots and effectively remove the defects of the ingots such as pores and inclusions [3l _ At present, there is no report of study on the electroslag remelting refining processes of CuCr alloy (the refining slag, remelting current). This article will research mode of occurrence and distribution law of inclusions in the large-size CuCr alloy ingots by Al Thermit-SHS under magnetic field stirring action and provide a theoretical basis for chosing refining slag to remove inclusions by electroslag refining. Meanwhile the article analyses the effect of reduction conditions of Thermit-SHS on the types of inclusions, mode of occurrence and distribution of regular inclusions in alloy ingot, and refer theory for inclusions regulation in the large-size alloy ingots."

Jan 1, 2013

By Alicia Esther Ares

This study was conducted to investigate the directional solidification of Zn-20%A1 and Zn20% A1-1O%Si-3o/oCu alloys under different conditions of heat transfer at the metal/mould interface. The type of structure obtained in both cases was analyzed and related to the solidification thermal parameters such as cooling rate, growth rate, thermal gradient and recalescence which were determined from the temperature versus time curves. These parameters were correlated with the structure-like length of columnar grains and size of equiaxed grains. The metallographic analyses were done performing quantitative metallography and composition analysis of the different alloying elements along the cast samples by SEM (Scanning Electron Microscopy) and EDXA (Energy Dispersive X-Ray Analysis). Correlations between properties, structures and thermal parameters were found.

Jan 1, 2008

By John L. Sundstrom

Complete systems were designed -and are in operation to recycle the effluent streams and to remove impurities from tankhouse. electrolyte, Heavy em¬phasis was placed on making usable products from as many streams as poss¬ible at minimum capital and operating costs. Almost complete recycling: and reuse of water and sulfuric acid were paramount. Techniques used in-clude solvent extraction - electrowinning, evaporation - crystallization and filtration.

Jan 1, 1992

By I. M. Ritchie

Cyanide owes its great success as a lixivant for gold to the great strength of the Au-CN bond. A replacement for cyanide must similarly be a strong complexant for gold (I) or gold (III). The various alternatives are briefly considered and it is concluded that only thiosulfate has a reasonable chance of replacing cyanide as a relatively non-toxic lixivant at the present time. However, there are considerable technical problems to be overcome before thiosulfate can be considered to be a realistic alternative to cyanide. Firstly, the leaching of gold using aerated ammoniacal thiosulfate with copper as a catalyst is a complex process which needs to be understood and controlled carefully in order to achieve maximum recoveries with minimum reagent losses. Secondly, there needs to be an option similar to the CIP process for recovering and concentrating the dissolved gold thiosulfate complex from pulps produced in the processing of low grade gold ores. The prospects for overcoming these technical' challenges are evaluated and discussed.

Jan 1, 1998