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By R. Elliott, H. Bayati

"Effect of time and temperature on microstructure and mechanical properties of an austempered ductile iron, ADI, of composition 3.6%C, 2.6%Si, 0.4%Cu, 0.2%Mn are reported. Xray analysis and. microstructural observations indicate that lowering the working temperature, aging temperature, increases the lifetime of ADI significantly. Results show· that lowering the aging temperature increases the strength and reduces the ductility of ADI. DSC traces for ADI austempered at 340°C are presented. Comparison of the DSC analysis and kinetic measurements demonstrates that the DSC traces can be· used to predict the life time of ADI successfully.IntroductionAustempered ductile iron, ADI, is one of the most significant developments in cast iron technology over the past two decades. Outstanding properties of high yield, ultimate strength, ductility, fatigue and wear· resistance make ADI suitable for a range of applications including gears, connecting rods, crankshafts and agriculture machine components. The austempering reaction in cast iron occurs in two stages, Fig. I, in contrast to the single stage reaction in steel. In stage I the relatively low carbon austenite produced during austenitising transforms into ferritic plates and high carbon austenite, a metastable structure called·ausferrite. The high carbon ailstenite and supersaturated ferrite produced in stage I decompose into ferrite and carbide in stage II: to form a structure similar to the bainitic structure in steel. This behaviour exposes a well-defined processing window, t1 - t2, over which the maximum amount of ausferrite is produced, Figure 1. Whereas the bainitic structure determines the properties of austempered steel, ADI properties are mainly affected by volume fraction of retained austenite (VRA), austenite carbon content (ACC), unreacted or martensite volume fraction (UA V), compositiori and amount of carbides, and morphology of ferritic plates[l,2]. Due to the detrimental .effect of martensite and carbides on properties of ADI, an ideal structure of ADI consists only of ausferrite [l,2]. Thus, it is common to determine the processing window for each austempering treatment in order to identify the optimized austempering time. Decomposition of austenite (stage II) signals the end of the life time for an ADI component, therefore, the aging behaviour of ADI at different working conditions can be studied by determining the t2."

Jan 1, 2000

By C. Hennesmann, D. Maijer, S. L. Cockcroft, P. Yo

"Die cast aluminum wheels are one of the most difficult automotive castings to produce because of stringent cast surface and internal quality requirements. As part of a collaborative research agreement between researchers at the University of British Columbia and Canadian Auto Parts Toyota Incorporated, work has been underway to predict heat transport and porosity formation in die cast A356 wheels. The basic heat transfer equations have been solved using the commercial finite element package ABAQUS to which specialized routines have been added to predict porosity. Preliminary work on predicting porosity formation focused on using the Niyama parameter as a measure of the probability of porosity. The latest version of the model incorporates a new fundamentally based porosity criterion, which takes into account the effect of hydrogen concentration. The development of this model together with its application to a series of cylindrical test castings as well as a production cast wheel are presented.I. IntroductionDie cast aluminum wheels are one of the most difficult automotive castings to produce because of stringent cast surface and internal quality requirements. Microporosity, in particular, is a common defect that can adversely affect wheel quality. The mechanism of microporosity formation in aluminum alloys is complex owing to its dependence on the interaction of a number of phenomena occurring during solidification including the decrease in hydrogen solubility, the decrease in volume, the development of the solidification structure, and the increase in difficulty in interdendritic feeding [1]. As a result, the amount, size, and distribution of microporosity is affected by a large number of casting parameters including thermal variables, melt composition, grain structure, modification, and inclusion content, making optimization by trial-and-error methodologies difficult.The use of criteria functions, based on thermal conditions during casting, offers a relatively simple approach to predicting microporosity. In practical terms, they are useful because they provide a straightforward method of assessing the impact of varying casting parameters on porosity through various thermal parametersl21 such as thermal gradient, cooling rate, solidification time, and solidus velocity. Drawbacks of criteria functions include insensitivity to varying hydrogen concentration and the limitation to qualitative predictions. Consequently, in aluminum alloys, attempts have been made to develop models incorporating the effects of hydrogen gas and microstructure evolution. However, these types of models represent a significant increase in complexity and sacrifice the simplicity and ease of application of the thermally based criteria functions."

Jan 1, 2001

By Mike Johnson, Niels Verbaan, David Dreisinger

The Search Minerals Foxtrot project in Labrador is a surface deposit enriched in the highly sought after heavy rare earth elements. Early metallurgical work investigated beneficiation of the rare earth content of the Foxtrot resource using flotation, gravity separation and magnetic separation. The concentrate was then processed by acid baking and water leaching to produce a REE leachate for purification and recovery. The Search Minerals Direct Extraction Process was developed through bypassing the beneficiation process and directly acid treating a coarse crushed ore material prior to water leaching. The result is a simple, low risk technical process for direct recovery. Concurrently, the treatment of the water leach solution was modified to produce a high grade (98.9% total rare earth oxide) product for refining.

Jan 1, 2016

By A. J. Maselli, E. C. Cemak

Hartford Steel Technologies (HST) has a pyrometallurgical and hydrometaliurgical process capable of reclaiming valuable metals from a hazardous waste· stream such as EAF Dust. The HST Process effectively addresses the growing environmental concerns surrounding the increasing production of EAF Dust without producing any hazardous waste material as byproducts. Currently EAF Dust production levels are exceeding the 1,000,000 metric tons per year mark. The HST Process is designed to separate iron, zinc, lead, cadmium, copper, and silver metals using a two-phased process. The Pyrometallurgical side of the Process utilizes a Rotary Hearth Furnace to separate the iron metal from the remaining metals. These remaining metals are further separated, using a Hydrometallurgical Process, in a series of digestion tanks. The individual metals are then collected in saleable form.

Jan 1, 2000

By Jared Ball, Benjamin Hogg

There are over 100 process parameters that can be monitored during a single Peirce-Smith (PS) converter batch operation. To support a consistent operation it is important to select the correct Key Performance Indicators (KPI’s) to monitor. They should be strategically chosen to drive the desired behaviour with enough flexibility to endure process variations. At the Xstrata Copper Smelter in Mount Isa most of the PS converter operators have very little experience and are often lacking in the appropriate education or training to properly understand the process. For this reason 10 simple KPI’s were chosen that could be easily comprehended and monitored by all smelter personnel. KPI compliance has been supported by relevant project work in the converter area. Charge sequence trials have been performed in an effort to reduce splash and optimise activity time. The online measurement of full and empty ladle weights has enabled an immediate indication of skull size, skim/slag carryover, and metal loss.

Jan 1, 2009

Cospidie (3CaO*2SiO2*CaFe2) is one of the most important compounds crystallized in mold flux films during casting in the continuous casting process of steel, The primary crystallization field of cuspidine has been experimentally developed in the CaO-SiO2-CaF2-SiF4 system. The cuspidine-NaF binary and cuspidine-CaF2-NaF ternary systems have been also experimentally determined to study effects of addition of NaF on the primary field of cuspidine. In order to discuss its thermodynamic stability the standard Gibbs energy of formation of cuspidine has been deterimed by an electromotive force methods using CaF2 as solid electrolyte and a transpiration method as follows: ^fG° (cuspidine) /kjmol-1 = 5198 + 0.825T (+12) (1313<T/K<1329): EMF method ^fG° (cuspidine) /kjmol-1 = 5178 + 0.813T (+8) (1221<T/K<1469): Transpiration method The chemical potential diagram and constituent activities for the CaO-SiO2-CaF2 System have been evaluated based on the obtained thermodynamic data.

Jan 1, 2003

By Yoshihiko Maeda

It is said that the 21 st century will be an era of the remedy of the global environment. In order to reserve natural resources for the future and to avoid the dispersion of heavy metals after usage and to avoid pollution problems, it is extremely important to recycle heavy metals as much as possible by reasonable recovery procedures. The nonferrous metal industry is expected to play a important role in the recycling of heavy metals that are originally their products. From the depressed metal price experienced in Japan in 1980th due to the sudden change in current exchange rate between US dollar and Japanese yen, one of major nonferrous metal company, Dowa Mining, has diversified its business area not only to the so-called down stream, but also to the environmental business including metal recycling, industrial waste treatment and soil remediation by utilizing technologies and facilities once used or still used for mining and smelting of copper, zinc, lead and precious metals. In this paper some of these applications will be presented.

Jan 1, 2003

By W. Persson

The first installation at a copper smelter of a Semtech OPC System for continuous, on-line production control of copper converting in PS converters took place in 1994. At present OPC systems are installed at 19 PS converters. The technology presents to the operator real-time information on the progress of the process he is controlling in the form of optical process parameters, thus facilitating dynamic process control. The optical process parameters are based on time- and wavelength resolved registrations of the light emitted by the off-gas flames and identification of correlation between these parameters and characteristic metallurgical process data. The present paper provides a description of the technology as seen by the furnace operators and a summary of operating experiences made during five years of full-scale, operation at various smelters, reviews influences from the technology on smelter operational practises and comments on recent developments as regards new applications of the technology.

Jan 1, 1999

By P. N. Anyalebechi

"The effects of solidification rate, initial melt hydrogen concentration, and grain refining on porosity formation in aluminum alloy 2024 have been investigated with unidirectionally cooled laboratory-size ingots. The ingots were prepared from melts containing hydrogen concentration of 0.059-0.27 cm3/100 g and solidified at 0.2-37 °C/s. As expected, the amount of porosity, average pore size, and pore number density increased with increase in melt hydrogen concentration and decrease in solidification rate. However, the effect of solidification rate was greater at the very low melt hydrogen concentration (0.059 cm3/100 g). These results are consistent with reported effects of solidification rate and melt hydrogen content on porosity formation in other aluminum alloys. Interestingly, addition of grain refiner slightly increased the amount of porosity and the average pore size, especially at solidification rates above 1°C/s. IntroductionIn shaped castings and wrought products fabricated from ingots, billets, bars, or slabs of aluminum and its alloys porosity formation is a problem. This is because it compromises their tensile strength, fracture toughness, and fatigue properties [ 1-18]. The pores are usually the crack initiation and propagation sites [6,8,9] and the largest pores tend to dictate the fatigue life of the aluminum products [9,10,14]. Porous regions within an aluminum product probably yield first due to the reduced tensile load bearing capacity, causing the concentration of the strain near the voids which subsequently results in premature fracture. In aluminum alloy ingots, billets, bars and slabs porosity formation is particularly problematic because of its persistence through fabrication and potential for reappearance or exacerbation during subsequent thermal treatment processes before and/or after fabrication [19]. In fact, persistence of microporosity is a serious problem in large thick plates of wrought aluminum alloy products that must be rolled from correspondingly large direct-chill or electromagnetic cast ingots. Some of these thick plate products are machined into large aircraft components that are required in service to withstand multi-directional stresses and to possess high fatigue strength, fracture toughness, resistance to stress corrosion cracking, and strength in the short-transverse direction [1,20]."

Jan 1, 2011

By Germán Richter a

To comply with the chilean air quality regulation requirements, the Hernan Videla Lira Smelter which is a custom smelter having to cope with a wide variety of concentrates, has developed a two-step modernization plan. The main steps are: - A second acid plant of 80,000 Nm3/hr to be operating at the end of 1996. This will increase the sulphur capture from 43% to 701/o in association with the replacement of the Hoboken converter by a second PS-converter to reduce the operation problems resulting from the treating of high garde matte. - Oxygen enrichment, is going to be incorporated in 1998 in the Teniente Converter and PS-converters in association with tuyere injection of dry concentrates, increasing the sulphur capture to 90 - 93% of sulphur inputs. By this program, sulphur emissions will be decreased from 40,000 tpy today to less than 8,000 tpy and in this way to carry out the environmental regulations.

Jan 1, 1996

By Larry Hopkins

The molten metal circulation pump has become a staple for melting aluminum in reverberatory furnaces. The forced convection that is created in the melt efficiently provides circulation while dramatically improving melt rates, lowering fuel consumption, extending refractory life, and providing metallurgical homogeneity. Two metallurgical guidelines that are important to many casthouses are molten metal inclusion levels and hydrogen gas content. In order to improve molten metal quality, furnace and casting practices must &apos;manage these molten metal defects, Today specialized in-line degassing and filtration equipment is used downstream of the furnace to accomplish these tasks. In contrast, the molten metal gas injection pump has metallurgical contact time in the process for hours during the charging/homogenization cycle. The qualitative benefits of employing a gas injection pump to "pre-clean" are outlined and discussed against historical empirical information obtained with alternate methods. Further, a recent study quantifies the merits of this gas injection technique as an effective molten metal quality improvement tool. Specifically, the effects on inclusion level as determined by PoDFA?, gas content as determined by A1SCAN? sampling and alkali metal content as determined by spectrographic analysis are examined in relationship to various gas feed compositions and flow rates.

Jan 1, 1995

By Mark Jolly, Xiaojun Dai

"Foundry engineers in the traditional foundry usually regard the quality of casting component as the most important issue and leave the energy saving or energy efficiency as the subsidiary one. This frequently causes disproportionate energy consumption as a result of the inefficient casting processes used and increases the production costs. This paper presents the novel CRIMSON aluminium casting process and compares its facility and melting process with traditional melt furnaces and aluminium alloy melting process. A real example is investigated to demonstrate quantitatively how the traditional foundry wastes energy and what the improvement of energy efficiency can be achieved using the new CRIMSON method. The results of this investigation will help the foundry engineer recognize the importance of energy saving and demonstrate how to use this new technology to reduce production costs and carbon footprint without decreasing the quality of the cast component.IntroductionAluminium melting in metal casting industry is an energy intensive process where it is estimated that the energy consumption is in the order of 1,700 ~ 4,700 kWh tonne-1 in using crucible and natural gas [1]. Different countries may use different energy resources for aluminium melting: in US the main energy resources are natural gas, electricity and coke [2] and in UK most of the foundry use electricity, gas and oil as energy resources [3]. Due to the pressure of rising energy price and the strict environment law, it is anticipated that under the right socioeconomic conditions, the efficiency optimisation of industrial process can be an important step toward increased industrial sustainability [4]. In metal casting industry the energy efficiency of a casting facility depends largely on the efficiency of its melting and heat treating performance. In association with the two performances, over 60 % of the total process energy costs are represented in a typical casting facility [5] where there are huge opportunities for metal casting industry to adopt the best energy practices for potential energy saving. How to ameliorate the current processes for increasing energy efficiency will have a vital effect on reducing the production costs and increasing the competitiveness. For instance, by implementing some state of the art technologies such as the CRIMSON method in aluminium alloy casting will make use of such opportunities."

Jan 1, 2011

By D. G. Hattingh, A Els-Botes

"Considerable information is available on the factors influencing the iron-zinc reaction rate at 450° C of low carbon steels, in comparison there is a scarcity _of similar fundamental information of spheroidal graphite irons. This can be attributed to the more complex microstructure and ferrous alloy chemical analysis of spheroidal graphite irons. Hot-dip galvanizers have identified the complexity in controlling and predicting the thickness of the galvanized coating formed on commercial cast irons, which has serious financial implications for both the galvanizer and customer.Commercial hot-dip galvanizing has been in use for over 160 years and yet an elementary understanding of the dynamics associated with the hot-dip galvanizing of spheroidal graphite cast iron is still insufficient. To allow the. process to become a modem surface engineering technology, the fundamental aspects of the process must be thoroughly understood.When a clean iron or steel article is dipped into the molten zinc, zinc initially solidifies around the steel or iron. As heat is transferred to the article form the bath, this initial solidified zinc layer remelts and a series of iron-zinc alloy is formed by the reaction of the zinc with the surface of the article; on removal from the bath, some of the molten zinc is taken out on top of the alloy layers. At normal galvanizing temperature (450 °C), the reaction between iron and zinc is usually parabolic with time. The rate of reaction is rapid at first but then slows down and the coating thickness does not increase greatly if the article is immersed in the bath for longer times(1)."

Jan 1, 2000

By Yasushi Sawada

An experimental investigation was carried out to study the rates of reduction of iron oxides dissolved in liquid Ca0-SO2-A203 slags by Fe-C droplets at temperatures ranging from 1325 OC to 1550 OC. The %FeO in the slag was varied from 5.5 to 18. Flash X-ray images were employed to observe the behavior of Fe-C droplets in the slags during the reactions and for determining the slag-gas-metal interfacial area. Effect of P205 in the slag and sulfur in the droplet was also investigated. The reduction rates were determined by measuring the volume of CO evolved as a function of time and the estimated slag-gas- metal interfacial area. The reduction rates have increased with increasing %FeO in the slag and the slag temperature. The experimentally established relationship between the reduction rates and FeO (wt%) in slag is given by

Jan 1, 1992

By G. E. Lagos

This paper analyses the scope and instruments employed by the Basel Convention for regulating the transboundary movement of hazardous wastes, the present and projected hazardous waste regulations of Chile, reviews the Chilean import/export trade of wastes of the period 1985-1995, and discusses, the influence that the Basel Convention has had on mining trade, its perceived benefits and costs, and possible effects on Chile&apos;s trade of the application of the Convention&apos;s Decision III/l. There is no quantitative estimation as to the effect of the Convention on the general volume of imported or exported materials destined for recovery, recycling, reclamation, or reuse. All recycling imports, with the possible exception of residues of petroleum oil, which occurred during the decade 1985-1995, can be classified tentatively as non hazardous. The entry into force of the Convention has had several effects on Chile&apos;s trade. It has brought home the need to have a comprehensive hazardous waste legislation, it has been a base for applying import restrictions, which in all likelihood, would .have otherwise not been applied, The benefits and costs of this import restriction, as well as those of the multilateral export ban are analyzed.

Jan 1, 1999

By T. T. Chen

Canadian Electrolytic Zinc has developed the "cement-stabilization of jarosite residue" Garofix) process to stabilize zinc plant jarosite residues for disposal. The cement-jarosite mixtures cure quickly, have good mechanical strength and low hydraulic permeability; they possess good neutralizing capability and chemical stability. In the jarofix process, Portland cement partly decomposes jarosite to form (SO4MOH)12.nH2O, ferric hydroxide and an alkali sulphate. Approximately 40% of the jarosite reacts in mixtures containing 30% cement. The jarofix product also contains various Ca-Al-Fesilicate-sulphate-hydrate phases and gypsum, which bond the individual particles together imparting mechanical strength and reducing the permeability. Most of the reactions take place in the first few hours of curing. Ammonium jarosite is slightly more reactive than sodium jarosite but releases NH3 gas; water-soluble Zn in the jarosite residue is stabilized in the cement reaction products.

Jan 1, 1996

By Shengqi Chen

The reduction smelting of nickel laterites produces slag, consisting principally of the chemical components MgO, "FeO", SiO2, and A12O3, and ferro-nickel alloy. Despite the fact that the phase equilibria for the ternary MgO-"FeO"-SiO2 up to 1500°C is well established limited experimental data are available in the MgO-"FeO"-SiO2-Al2O3 system, which is relevant to commercial operation of the process. A methodology has been developed for the experimental investigation of the liquidus temperatures for the multi-component system MgO-"FeO"-SiO2-Al2O3-Cr2O3 in equilibrium with metallic iron. Experiments have been carried out using high temperature equilibration, quenching, followed by electron probe X-ray microanalysis (EPMA). Liquidus temperatures have been determined in the silica primary phase field in the composition ranges directly relevant to the Cerro Matoso S.A. ferro-nickel smelting slag. Liquidus isotherms have been determined for temperatures between 1450 to 1600°C. The study enables the liquidus to be described for a range of MgO/FeO ratios. It was found that liquidus temperatures in the silica primary phase field decrease significantly with the addition of AI2O3. Keywords: Liquidus temperature, ferro-nickel, pyrometallurgy, smelting

Jan 1, 2004

By B. C. Blakey

Unlike most hydrometallurgical slurries, those containing significant concentrations of goethite are typically highly viscous and shear-thinning, even at solid volume fractions below 5%. The viscosity may also depend upon time. These characteristics must be taken into consideration in slurry transport and heating. The technical literature is replete with apparent contradictions regarding the viscous behavior of these slurries, which may be due, in part, to variations in viscosity-measuring techniques. We present techniques that yield consistent results suitable for use in process design. A striking degree of time-dependent behavior is demonstrated for a laterite slurry. Reliable methods to design and analyze tubular transport and heating systems for time-independent slurries are summarized. Rules of thumb are then offered to account for the effects of time-dependency.

Jan 1, 2000

By C. Díaz

Roast-reduction smelting (RRS) of nickel concentrate, combined with flash smelting of copper concentrate, was one of the process options that Inco considered as a means of meeting its 1994 sulfur dioxide abatement target at its Copper Cliff operations. RRS involves deep roasting the nickel concentrate in fluid bed roasters. The roaster off-gas is heated in a sulfuric acid plant, and the low sulfur calcine is reduction smelted with coke in an electric furnace to yield a sulfur-deficient matte. The latter material is converted to Bessemer matte in Peirce-Smith converters, with minimal evolution of sulfur dioxide, and the converter slag is reverted to the electric furnace. Excellent nickel and cobalt recoveries are obtained. This paper discusses the development of RRS, including extensive commercial scale testing at Inco&apos;s Thompson Smelter, and its key operating parameters.

Jan 1, 1993

By Huimin Lu, Qiang Li, Jingbo Xu

"The smelting reduction of V-Ti bearing beach placer by combined rotary hearth furnace and direct current arc furnace was studied in laboratory. It takes the aid of back propagation (BP) neural network theory to build the nonlinear mapping relations between the crucial process variables such as content of carbon, temperature and time and the degree of reduction. Then by the integrating BP neural network and genetic algorithm (GA), the optimized process parameters for the high degree of reduction were searched. The comparisons between experiment results and neural network simulation results show that GA-based on BP method can predict the degree of reduction with higher prediction accuracy. Calculations show that the integrated energy consumption of new technology is 580kgce/tHM, less than the current existing blast furnace.IntroductionThese V-Ti bearing beach placers (VTBBP) are secondary Fe-rich minerals formed by rivers, ocean waves, ocean tides and ocean currents on beach zones, their useful minerals are V-Ti magnetite ores. On Asia Pacific zone, such as Japan, China, Philippines, Indonesia, Australia and New Zealand, the VTBBP have large reserves and wide distribution. But so far, the VTBBP are not still comprehensively utilized. Therefore, in this paper, a combined rotary hearth furnace technology and arc furnace smelting method is studied for comprehensive utilization of the VTBBP. The main objective of this paper is to find optimum operation conditions for the production ofV-bearing iron and titania-rich slag from the VTBBP by means of the laboratory testing.Recently, neural network (NN) expected to be able to provide an effective tool because of its advantages, which describe nonlinear mapping relations. With the characteristics of strong selflearning, self-organization, robust error toleration and accurate nonlinear relation approximation, artificial neural network can be applied to nonlinear process modeling based on sufficient training. Back-propagation (BP) training algorithm is probably the frequently used one in practical application. Genetic algorithm has parallel search strategy and global optimization characteristics, which makes the trained neural network being higher classification accuracy and faster convergence speed. So it is necessary to combine neural network and genetic algorithm. The nonlinear relationship between input and output presented by NN and the global optimal function of GA are abroad applied in the engineering and scientific research [1, 2]. So these methods supply an efficient path to solve the above problems. At present, it is common to study the optimization of process parameters by orthogonal experimental design, the method combining neural network and genetic algorithm is a novel and better method than orthogonal experimental design. Tills study organized the above advantages to optimize the process parameters for comprehensive utilization of the VTBBP."

Jan 1, 2012