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By I. C. Howard, E. J. Palmiere

"Heat transfer and friction in hot flat rolling have traditionally been characterised by an average heat transfer coefficient (h) and an average friction coefficient (p.). However, the presence of oxide scales and asperities at the interface question the use of such averages. The apparent irregularity and lack of pattern of interactions at the interface has prompted this present investigation to move away from averaged h and 11 values, and to study their local evolution based on probabilistic rules. The approach is based on the probability of finding the workpiece surface in a specific configuration at a particular instance of time in the roll gap. These rules are based on observations of surface phenomena such as scale behaviour during hot rolling. The model is implemented using user-subroutines integrated with the commercially available finite element program ABAQUS™. The results show the strong dependence of h and u on the local scale interactions. In particular, the effect of scale thickness, material behaviour and processing conditions on the evolution of hand 11 are discussed. Finally, the development of a Cellular Automata based Finite Element (CAFE) model is proposed to model the combined interfacial phenomenon of friction and heat transfer at the tool-work piece interface.IntroductionIntricate interactions between process variables in hot rolling of steels make it a challenge to the modelling community. For a given material and geometry combination, reducing interfacial power losses can increase the efficiency of the rolling process. The roll-strip interface, therefore, forms the critical zone and is currently the domain of intense investigation, especially to characterize interfacial frictionl • 2 and heat transfer3 • 4 . These interfacial phenomena are inter-related and cannot be studied in isolation. However, very few mathematical models4 • 5 combine an analysis of friction and heat transfer and deformation of the strip-roll interface taking into account the role of asperities and oxide scales."

Jan 1, 2001

By José R. Parga

In some parts of the Comarca Lagunera with population of about 2.5 million people, situated in the central part of northern México, chronic arsenic poisoning is endemic and severe adverse effects attributed to As exposure have been reported. Lifetime exposure to arsenic will develop classical symptoms of arsenic poisoning such as skin pigmentation changes, gastrointestinal disturbances and neurological changes. There are several methods available for removal of arsenic from well water in large conventional treatment plants, however a very promising electrochemical treatment technique that does not require the addition of chemicals or regeneration is Electrocoagulation (EC). The EC operating conditions are highly dependent on the chemistry of the aqueous medium, especially conductivity and pH. In this study, Powder X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Transmission Mössbauer Spectroscopy (TMS) were used to characterize the solid products formed at iron electrodes during the EC process. This study will provide an introduction to the fundamental concepts of the EC method. Finally the results of this study suggest that the presence of maghemite and magnetite particles can be used to remove arsenic (III) and arsenic (V). In the field pilot plant scale study more than 99% removal of As species from groundwater is achieved.

Jan 1, 2005

By Elias Rigopoulos

In the present study the reductive behavior of dust from the rotary kilns (RK), in ferronickel production from nickeliferous Greek laterites, is investigated. The study concerns dust of various origins (washing towers, electrostatic filters, polycyclones) and pellets made from the dust. Reducibility was studied in the temperature range of 700 °C to 850 °C in a laboratory tube furnace. Experimental results showed that reduction degree increases with temperature up to about 800 °C. The rate of reduction is great during the first minutes, giving a reduction degree R% equal to about 25%, in only a few minutes. After this, the rate is decreasing until it diminishes to zero after about 10-20 minutes of reaction. Maximum reduction degree achieved is 26 to 28%. Rates and reduction degrees at various temperatures are higher for the dust samples than those of the respective pellet samples. Keywords: Ferronickel, metallurgy, laterites, pellets, reduction

Jan 1, 2004

By R. Altman

A Brookfield viscometer fitted with a stainless steel bob was used to measure the viscosity of industrial lead blast furnace slags between 1126 and 1298°c. Slag oxidation state was characterized by first annealing the? slag samples at 750°c in sealed copper tubes in order to precipitate magnetite crystals. The magnetite concentration was then measured on an Outokumpu Saturated Magnetic Analyzer. Using an Arrhenius-type equation, a viscosity model was developed by regression. The equation below accounted for 75% of the variability in the data used to generate the regression coefficients and, on average, could predict viscosity within ± 12% of the measured value. The greatest difficulty encountered in measuring viscosity was due to the occasional presence of solids in the slag which caused, at times, erroneously high viscosity measurements. Precautions to minimize this problem are outlined in the text.

Jan 1, 1985

By W. S. Kirk

World cobalt production in 1987 was estimated to be about 26,600 metric tons (MT) of which Market Economy Country (MEC) production was estimated to be about 22,000 MT. Zaire and Zambia produce about 80 percent of the primary cobalt produced among Market Economy Countries (MEC). Production cutbacks. lowering cobalt grades and mining curtailments in Finland and Zambia in 1987, resulted in lower production than that of 1986. The trend is expected to continue through 1988. Cobalt production from Canadian ores and from Botswana is expected to increase significantly in 1988 as a result of increased nickel production. MEC production in 1988 is estimated to be 22,100 MT, only slightly higher than that of 1987. There are currently no primary cobalt mines. Virtually all cobalt is recovered as a byproduct of copper and/or nickel mining. Zaire, which produces cobalt as a byproduct of copper, is the worlds largest cobalt producer, with over 50 percent of total estimated world cobalt production and nearly 65 percent of MEC production. Zambia follows with about 14 percent and 17 percent, respectively. Zambia's cobalt production also results from copper production.

Jan 1, 1988

By A. Rios

ENAMl's Paipote Smelter commenced operations in 1951. At present, it processes 230,000 tonnes/year of green feed in a conventional smelter, which comprises one reverberatory furnace, two Hoboken, one Peirce-Smith converters and one rotary anode furnace. The feed is composed of 83% copper concentrate and 17% metallic copper precipitates, which results in a feed average grade of 32% of copper content. The final products are 75,000 tonnes/year of copper anodes and 48,000 tonnes/year of sulphuric acid. At present, the plant is undergoing a modernization to expand the smelter capacity to 300,000 tonnes/year of green feed and increase the sulphuric acid production to 100,000 tonnes/year. This will be achieved with the installation of an El Teniente Converter and an expansion in the acid plant. The work began in November 1991 and is scheduled to be in operaton by March 1993. The paper provides an overview of the modernization plans and results achieved to-date.

Jan 1, 1993

By Thomas Prietl

The use of gas stirring systems through the furnace bottom is common for anode and holding furnaces in the copper industry The first implementation of a gas stirring COP KIN® system in a Peirce-Smith converter was performed at the New Boliden smelter, Rönnskar, Sweden. In addition to other benefits, a decrease in process time and a decrease of the oxygen content in the blister copper were observed. To determine the effects of the gas stirring system and the process endpoint, an optical production control ?Semtech OPC system? was used. The light emission of the converter flame as an optical process parameter provides qualitative on-line process information, and is also used for endpoint determination of the slag making process, on-line control of iron content in white metal, quality control of slag etc. The results, benefits and risks of using the COP KIN® and OPC system for a Peirce-Smith converter are reported.

Jan 1, 2005

By A. S. Usrnani

Due to both turbulence and the highly variable geometry of castings, a realistic numerical simulation of the metal flow is prohibitvely expensive with current technology. However, when the chief purpose is to achieve realistic thermal fields a precise How simulation is not necessarily required. In this paper we assume a laminar flow regime and obtain the flow field by solving the incompressible Navier-Stokes Equations using a velocity-pressure segregated semi-implicit finite element method. The free metal surface is predicted by advecting a pseudo-concentration function via the computed How field. This involves an explicit finite element solution of a pure advection equation. The thermal field is calculated by solving the convective-diffusive energy equation by an explicit finite element method using the computed flow field and the location of the free surface. All the advection terms are discretized using a Taylor-Galerkin method. The interface between the metal and mould is modelled using special interface elements. The model is demonstrated by solving practical example problems. The results show that a sharp thermal front is maintained during the course of filling without excessive diffusion. The heat diffusion in the mould can be controlled by varying the metal mould heat transfer coefficient.

Jan 1, 1994

By Mehdi Asadi, Heinz Palkowski

"In recent years, the increased demand for advanced high-strength steels (AHSS) mainly had been driven by the need of the automotive industry to reduce weight and to improve safety. Beside good ductility and high strength, those steels have a high bake hardening (BH) effect, giving additional contribution to the strength of structural parts, subjected to the paint baking process. In this paper we concentrate results gained for hot rolled dual phase (DP) steels.For the simulation of changing process conditions within the final hot rolling the specimens were hot deformed using different schedules of temperatures and reductions, selected according to the non-recrystallization temperature (TnRX). It was possible to refine the DP steel structure by control-ling the deformation temperature and the amount of strain below TnRX during the thermo-mechanical controlled processing (TMCP). This structure refinement resulted in an improvement of the strength and BH behaviour. A wide spectrum of mechanical properties could be obtained depending on the different hot deformation schedules. The best strength and BH levels were recorded for the deformation below TnRX at the highest amount of strain.IntroductionDP steels are characterized by a good formability, high strength and a good compromise between strength and ductility [1]. Moreover, the DP steels exhibit a continuous yielding behaviour, low yield point and a high strain-hardening coefficient [2]. Furthermore, the DP steels often show a large potential for bake hardening (BH). BH refers to the increase in yield strength as a result of the paint baking treatment of the shaped auto-body parts. The primary mechanism that causes the additional strengthening is the immobilization of dislocations by the segregation of interstitial atoms, known as classical static strain aging [3]. The increase of strength thus achieved allows a further reduction of sheet thickness and improves the crash safety and the dent resistance. The BH of special steel qualities is technically used in DP, where e.g. the increase in strength is realized in the final heat treatment [4]. Previous own investigations [5-6] stated that the BH effect of DP is much stronger than that one for conventional BH steels."

Jan 1, 2012

By P. Halsall

Smelters of medium or low grade tin concentrates must recover a high proportion of tin from iron-bearing slags or concentrates; the volatility of tin sulphide makes possible the production of iron-free tin fume. Laboratory work defined conditions which would promote the sulphidisation of tin slags and concentrates melted with them, to result in tin recovery as fume, and a residue of less than 0.5% Sn content, which could be controlled to vary with the value of tin. Subsequently pilot-plant work on 6-tonne and 15-tonne scale led to a commercial plant of 45 tonne. capacity (1962), for melting and fuming primary and secondary low-grade tin materials by submerged combustion. Some factors contributing to the rate of Working expressed in terms of the 'half-life and the amount of work done, the 'half-life-tonne' are studied, leading to the design and operation (1972) of the 100-tonne water-jacketed unit, presently in use, treating a wide range of slags and low tin-content ores and residues.

Jan 1, 1983

By Geysen. Daneel

Better slag valorization is part of improving the sustainability of steel, stainless steel and non- ferrous metal production processes. Besides, it can improve the sustainability of other products and production processes as well. A sound and well established slag valorization is beneficial for the overall economics, marketing and appreciation of the metallurgical process and its products. On 6-7 April 2009, the First International Slag Valorisation Symposium was held in Leuven, Belgium. This paper gives a brief summary of the symposium, providing an overview of slag valorization opportunities. The authors believe that high temperature process slags can have interesting applications and that within the next 10 to 20 years slags will need such valorization options in order to compete with other materials and get general support for further production. On the other hand, the authors also expect a higher demand for slags for the production of various materials. High temperature processes should anticipate on the growing opportunities for valorization of slags and increase the resilience of their process by better understanding slag processing, slag quality and material requirements. More interdisciplinary research efforts are required to reach this level of knowledge for the different high temperature processes. Such an interdisciplinary research platform was recently established at KULeuven, Belgium, named SMART-PRO2 (Sustainable Materialization of Residues from Thermal Processes into Products).

Jan 1, 2010

By Fumito Tanaka

The Mitsubishi Process is the sole pyrometallurgical process for the continuous production of blister copper from copper concentrates. Continuous converting originates from the application of the proven technology of a lime-ferrite slag (CaO-FeOX-Cu2O) on the Converting Furnace (C-furnace). Recent improvements on the C-furnace operation have included increasing the processing of recycled materials and the investigation of alternative fluxing agents. However, some minor oxides adversely affect C-furnace operation, with respect to magnetite behavior of the slag, with the most significant impact having been observed with the silica content of the slag. This paper will quantify the impact of silica on the lime-based slag, and discusses the controls that have been identified to sustain continuous converting operation.

Jan 1, 2005

By A. Gibson

Most methods for the treatment of scrap printed circuit boards do not reclaim the components in working order as the boards are either fed to a copper smelter, to recover the valuable elements, or, simply landfilled. This work reports the dissolution of the solder in fluoroboric acid containing Ti4+ ions which was particularly selective for solder, allowing the components to be recovered. The solder was subsequently electrowon from the leachant. The boards were then shredded and the copper dissolved in ammonium sulfate and, then treated via solvent extraction to give an electrolyte suitable for electrowinning. The remainder of the metals were dissolved aqua regia, silver remained unattacked by the aqua regia, palladium precipitated as Pd(NH4)Cl6 in the presence of zinc and nickel, the gold was removed by solvent extraction and precipitated as nanoparticles. The aqua regia was then diluted and the zinc and nickel separated by solvent extraction.

Jan 1, 2009

Achieving continued economic growth with social equity within the natural limits of the Earth's 'eco-systems is the major issue facing the world today. The material and energy needs of the world cannot be met with the current ways of addressing this issue. The need for metals, an important class of materials, will continue into the future because their unique properties make substitution by other materials impossible in many applications and this need will continue to be met from primary metal production and recycling. However, the recycling rate will increase and the usage pattern of metals will change to reflect the environmental impact of their production and use. Pyrometallurgy has an important role in meeting the metal needs of the future since some metals can only be produced pyrometallurgically; the energy required to produce some metals pyrometallurgically is significantly less than by other methods; most metals are most efficiently recycled pyrometallurgically; and the release of harmful and toxic elements into the biosphere can sometimes best be controlled through pyrometallurgical processing. The development of strategies for pyrometallurgical processing for the future lies in the recognition that sustainable development calls for large step improvements in value delivered per unit of environmental impact over the entire supply chain. Pyrometallurgists can respond to this challenge by contributing to reducing the environmental impact of meeting metal needs using three broad strategies: "end-of-pipe" approaches to convert emissions into benign materials for storage or disposal; flowsheet redesign to limit or eliminate emission production; and improved recycling technologies. A number of examples are discussed to illustrate how the sustainability driver is already influencing the technological development of pyrometallurgical processes, and how these will develop further as the sustainability driver strengthens.

Jan 1, 2003

By Hui Wang

With the great increasing use of nickel metal hydride batteries recently, the waste of this kind batteries have been paid for close consideration. For the main reason that the waste of the batteries contained precious metals and lanthanide which cost great lose. This paper introduces the pyrometallurgical process of recovering nickel and cobalt from the waste of the nickel metal hydride batteries. Particularly, the waste for the process was from factory during the producing program. The use of designed solvent to divide nickel and cobalt in melted state from the waste is described. Also, the result of the nickel and cobalt and melted gangue that mainly consist of lanthanide oxide are included in details. The aim of the paper is to find out a simple and feasible way to reuse waste from nickel metal hydride batteries.

Jan 1, 2009

By Egil Aukrust

"An American Iron and Steel Institute Task Force evaluated developing direct steelmaking technology worldwide to seek a replacement for the coke-oven, blast-furnace, basic-oxygen process technology now in use. To remain internationally competitive it is essential to move away from the traditional series of batch processes towards continuous processing and the associated energy savings which are possible with high technology process control systems. The group identified in-bath smelting of iron ore pellets or fines with coal as the process most sui table for domestic raw materials (including abundant scrap) and called for research to study operation with varying degrees of preheat and prereduction of the ore by the gases generated from the coal and various degrees of combustion of these gases above the melt.A coordinated, 3-year, $27 million, direct steelmaking research program is proposed. Concurrent projects include design, construction, and experimental operation of an in-bath smelting pilot plant; modeling, simulations, and laboratory-scale experiments at universities on slag-phase and metallicphase reactions and interactions; and large-scale heat transfer and reaction rate trials. Also included are modeling studies and pilot plant trials of on-stream decarbonization and desulfurization; application of circulating fluid bed technology to fine ore reduction and hot gas cleanup; and specific heat transfer and fluid flow research projects.IntroductionThe American Iron and Steel Institute (AISI), based on the Task Force studying direct steelmaking, believes strongly that a coordinated program of research on the reduction of domestic raw materials to liquid steel should be undertaken as part of the Steel Initiative program. To specify the steelmaking process for development best suited to the American steel industry and domestic raw materials, it was important to determine the state-of-the-art of direct steelmaking worldwide, both as practiced and under development, and then, by expert analysis of the processes and their potentials, to choose the process most likely to provide a domestic competitive edge."

Jan 1, 1988

By S. Prasad

The effectiveness of ultrasonic velocity measurements and attenuation of the propagating pulse was evaluated as a means of Non-Destructive characterization of cold worked and annealed copper. Commercial copper is subjected to mechanical working such as forging, rolling and thermal treatment to induce re-crystallization. The microstructural changes that occur in copper and a variation in its mechanical properties are subjected to analysis using the ultrasonic technique. The signal processing is carried out using the wavelet analysis technique. The features of wavelet analysis namely, localization in space and the presence of an infinite set of basis functions allows removing noise from the time series and components of a non-stationary signal to be analyzed. This is seen to improve the accuracy of the results obtained from the ultrasonic technique in the case of copper, which has distinct coarse grains that are difficult to inspect due to backscattering from the grain boundaries.

Jan 1, 2010

By Pengfu Tan

A thermodynamic model has been developed to model the desilverising process of lead by the addition of zinc during lead refining, whereby silver-zinc solid solutions are formed, and floats out of the dissolved zinc/silver in the lead bath. The solubility of silver-zinc solid solutions in lead decreases with falling temperature. A number of variations and modifications of the desilverising process are modeled, and applied to a wide range of silver contents in lead bullions in the industry.

Jan 1, 2005

By Ramona Prillhofer

Salt slag is a waste product produced by the recycling of aluminum. In most European countries (e.g. Austria, Germany) the landfill disposal of this waste is forbidden because the slag contains soluble salts and these represent a potential source of pollution to the surface and groundwater. Additionally, consisting metal and some compounds in the salt slag can react with water and resulting from this, noxious gases are generated. The recovery of useful materials from these wastes is accordingly both environmentally necessary and economically feasible. This study describes a complete recycling-process for the salt slag, which includes a leaching-cristallization-process to obtain the oxidic residue, a pyrometallurgical-step to clear the oxidic residue and finally an extensive characterization of the achieved products. Due to the increasing price of raw materials, the utilization of the oxidic residue into commercial products has been investigated and application possibilities will be discussed.

Jan 1, 2009

By Lloyd Robert Nelson

The historical progression in installed electric furnace smelting capacity of some 1650 calcium, chromium, manganese, nickel and silicon ferro-alloys furnaces is reviewed. Key increases in the inherent installed electrical capacity, often achieved through uprating furnaces, are identified. Possible factors facilitating such advances are explored, including: specific process engineering and pyrometallurgical enhancements (e.g., improved control over the consistency, size and chemical form of raw materials, extents of preheating and pre-reduction delivered into the furnace; and patterns of feed distribution); furnace electrical configuration (AC or DC; immersed, submerged-, shielded- or open-arc); form of electrode (graphite, self-baking or composite); furnace configuration (circular or rectangular; closed or open and 1-, 3- or 6- electrodes); better engineering and equipment designs (e.g., high-intensity cooling) and state of furnace electrical and metallurgical control systems. A view is presented on the prevailing state of evolution of the Mega-scale in ferro-alloy smelting and opportunities for still further improvements.

Jan 1, 2014