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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 P. Rooney

In due course, new smelters will have to be installed in order to meet the increasing worldwide demand for copper. This paper presents the results of a study made for the purpose of identifying the most desirable countries in the world in which to locate a new smelter. Both sociopolitical and economic factors were taken into account. Criteria developed and methods used to assess each possible location are described. The study indicated that the most interesting potential locations are Canada, -Chile, Portugal and the USA for new copper smelting complexes.

Jan 1, 1983

By Stavros A. Argyropoulos

Exothermic mass transfer takes place in various areas involving metallic systems, ranging from liquid metal processing operations to the growth of thin films in microelectronics. The formation of intermetallic compounds plays an important role in the exothermic mass transfer of metallic systems. Two types of exothermicity are identified , namely , Microexothermicity and Macroexothermicity. The former is encountered when small amounts of metals are mixed, while the latter is exhibited when a solid metal in a lump form is added into liquid metal. In this paper two types of exothermic mass transfer in metallic systems will be presented and reviewed. Mathematical modelling work for these types of exothermic mass transfer will be analyzed.

Jan 1, 1993

By P. J. Mackey

New and emerging, as well as proven technologies for the smelting of copper, nickel, lead and zinc are briefly reviewed. The number of new technologies available today is greater than at any time in the past, and interest and development activities remain high despite the economic dif-ficulties faced by the non-ferrous metallurgical industry. Part of the impetus is provided by the realization that only the most cost effective producers will remain competitive, and that new technology is one key to cost effectiveness. The commercially proven "new" copper smelting processes can now be considered to be conventional- technology, and are expected to dominate copper smelting for acme time. There is a growing. interest in continuous copper converting, although direct smelting and converting to copper in one vessel remains the- ideal. There is little activity in nickel smelting. After many years. of development, it appears that several new direct lead smelting processes will soon be a commercial reality. The electrolytic zinc process is expected to continue its dominance, although there is a renewed interest in pyrometallurgical approaches. One of the new zinc processes, and a molybdenum smelting process, illustrate the possibilities of using plasma technology in non-ferrous metallurgy. In the area of complex sulphides, there is perhaps less interest in the treatment of bulk con¬centrate, and more in the treatment of so-called dirty copper concentrates. Much of the technology ancillary to smelting has remained relatively unchanged, and more effort must be made to advance the technology in areas such as materials handling, gas cleaning and sulphur fixation, and energy recovery. More attention to engineering design is also needed. Escalating capital costs may make mini-smelters attractive, but imaginative technology and innovative engineering will be required to make them cost effective. Finally, a glimpse is offered of the smelter of the future.

Jan 1, 1983

HW Process Technologies, Inc. (HWPT) has developed a patented membrane-based ion fractionation system, which specifically separates copper from gold and silver species in a cyanide matrix. This Engineered Membrane Separation (EMS?) system was pilot demonstrated on the 82,000 liters of pregnant leach solution' (PLS) generated from tailings, via thin layer leaching, at a mine site in Durango State, Mexico. The EMS? recovered ~90% of the gold-silver cyano-complex to a 90% volume permeate (based upon an EMS? feed stream of 100% volume) while rejecting -90% of the copper cyano-complex to a \0% (by volume) concentrate. The EMS? technology combines pore-size specific electro-statically charged membranes with engineered materials of construction and application-specific operational design that reject multi-valent, ionically charged species to the concentrate and transmit mono-valent species through the membrane to the permeate. The 850 ppm Cu PLS contained approximately 0.8 gil free NaCN with, the copper cyano-omplex principally in the CU(CN)3 and CU(CN)4 forms. The gold grade of the PLS was -2 ppm Au. The ~LS calcium concentration at -700 ppm Ca was reduced to ISO ppm.Ca (± 50 ppm) by sodium cycle ion exchange pre-treatrnent prior to EMS? processing.

Jan 1, 1998

By A. P. I. Popoola, D. O. Okanigbe, A. A. Adeleke

In view of the steady depletion of primary sources of copper and the increased global demand for refined copper, it becomes necessary to explore some secondary sources for possible extraction of copper. The waste copper smelter dust (CSD) is a rich secondary resource for copper as shown by the chemical composition of the South African Palabora coppers smelter plant CSD that assayed 18.02, 13.36, and 3.4 wt% copper, iron and sulphur, respectively. Studies on CSD have focused majorly on either dust characterization or treatment, while hydrometallurgical extraction without pretreatment and with pretreatment using techniques such as oxidative roasting are also considered quite attractive. The challenge of iron dissolution during the leaching stage in these processes necessitates adequate purification of the leach liquor before the extraction of the metal as nano-particles. Hence, this review examined the theories relating to the characterization and treatment of CSD for copper recovery as nanoparticles; with factors having a bearing on the treatment process such as kinetics considered with the aim of providing scientific basis for the research.

Mar 1, 2017

By Joseph Gambogi

In 1998, approximately 57,000 tons of titanium metal was consumed in the form of mill products (1). Only about 5% of the 4 million tons of titanium minerals consumed each year is used to produce titanium metal, with the remainder primarily used to produce titanium dioxide pigment. Titanium metal production is primarily based on the direct chlorination of futile to produce titanium tetrachloride, which is then reduced to metal using the Kroll magnesium reduction process. The use of titanium is tied to its high strength-to-weight ratio and corrosion resistance. Aerospace is the largest application for titanium. In this paper, we discuss all aspects of the titanium industry from ore deposits through extraction to present and future applications. The methods of both primary (mining of ore, extraction, and purification) and secondary (forming and machining) operations will be analyzed. The chemical and physical properties of titanium metal will be briefly examined. Present and future applications for titanium will be discussed. Finally, the economics of titanium metal production also are analyzed as well as the advantages and disadvantages of various alternative extraction methods.

Nov 26, 1999

By Guo Xueyi

The method of Substance Flow Analysis (abbreviated as SFA) provides a helpful tool for the study of the industrial metabolism of a certain metal within a regional level. In this work the flow of lead in China, 2006, was traced within the STAF model, and the situation of production, consumption and recycling of lead resources in China were introduced. The SFA is performed on lead flows during its one year life cycle in detail. As one of the biggest producer and consumer of lead in the world, China is facing a problem depletion of lead resources. How to increase the resource efficiency is a significant issue for lead industry of China. Based on the result, several suggestions were proposed in the paper, aiming to contribute important reference information for the industrial metabolism and resource management and recycling of lead industry in China.

Jan 1, 2009

By David Melgaard

A significant emerging recycling, waste minimization problem stems from legacy waste from the nuclear weapons program and from production of power using nuclear fuel. Premium quality metals used in nuclear plants become contaminated, making them unsuitable for reuse. Consequently, decontamination studies were conducted to evaluate the decontamination capacity and partitioning effeetiveness of Electroslag Remelting (ESR). Eight laboratory melts were conducted to evaluate the efficacy of using ESR to transport radionuclides from the liquid metal phase to the liquid flux or slag phase. To determine the decontamination effectiveness, several surrogate compounds for uranium, plutonium and other fission products were added to the melts. During the melts, the melting rate was varied, typical slag additives were used, and two different slag compositions were evaluated. The resultant post-test ingots and slag were then analyzed to determine the partitioning of the surrogates. ESR generally proved very effective in removing contaminates from the metal with a few noted exceptions. -

Jan 1, 2003

By B. R. Davis, Neale R. Neelameggham, R. E. Brown

The element Calcium element has a unique place in the production of etals, intermetallics and other compounds. The unusualness arises from the fact that we have several possible reductants – metallic calcium, calcium carbide, calcium cyanamide and calcium hydride. A review of how metallic calcium is manufactured and utilized is presented. The difficulties involved in producing the metal in large quantities and price implications are noted. . Fundamental thermodynamics of how these act as reductants are shown, along with the historic application of these in metal production during the past century and a half. Alternate applications as to how to control the cost of the reductant is indicated, such as the numerous attempts in making low cost titanium utilizing direct or indirect calcium reductant.

Jan 1, 2014

By Jorge Gibson, P. Chris Pistorius, Megha Jampani

Increased utilization of natural gas in blast furnace ironmaking can decrease both the cost and the carbon intensity of ironmaking, given current US natural gas prices. In this paper, three ways to utilize natural gas are compared: tuyère injection, prereduction of iron ore, and shaft injection. The basis for comparison includes coke replacement ratios, carbon intensity and furnace productivity. These were calculated using relevant mass and energy balances, a blast furnace productivity correlation based on the bosh gas flow rate, and measured and modeled prereduction kinetics. Of the natural gas utilization methods, prereduction has the highest effective coke replacement ratio (and hence the largest advantage in raw material cost), but is likely to have the highest capital requirement.

Mar 1, 2017

By H. Yin, T. Emi

"Advantages of gas/flux injection technology as materialized in the main stay unit processes for steelmaking are depicted covering hot metal pretreatment through secondary refining. Current status of micro-kinetic issues involved in the injection technology are reviewed including gas-in- metal, gas-in-slag, flux-in-metal, metal-in-flux and three-phase dispersion systems with reference to macro-kinetics. Key problems are briefly addressed to further develop injection technology for steelmaking processes.1. FROM PAST TO PRESENTApplication of gas injection to steel industry started in early 1950's when inert gas bubbling via stopper rod, lance, or porous refractory plug was practiced to make the temperature of steel melt in ladle uniform The gas bubbling in ladle was then extended to slightly removing hydrogen ti'om the steel melt tapped from Electric Arc Furnace (EAF) and Basic Open Hearth Furnace (BOH) when vacuum processing facilities were not popular. Later, oxygen gas injection via calorized steel pipe into molten steel bath in BOH Furnace was also put into operation to promote the decarburization to increase the productivity of the process. This line of development has been made in parallel with more profound processes, i.e, top blowing Basic Oxygen Furnace (BOF) for primary steelmaking and side blowing Argon Oxygen Oecarburization (AOD) vessel for decarburizing stainless steels.On the other hand, injection of fluxes into steel bath was first industrialized in Germany in 1960's, Primary objective was to desulfurize steel melt in ladle by injecting CaC2 or CaCrCaO mixture via lance under neutral slag cover with good success. Difficulties in injecting fluxes without clogging and rippling at a desired flux/gas ratio, and durability of injection lance were resolved in due time to bring forth many injection facilities to flourish for versatile refining operation. Top injection of fluxes from main oxygen lance to BOF was also industrialized as LDAC to promote early slag formation. A new process then emerged which injects oxygen gas and fluxes together through concentric annular tuyere, installed at the bottom of the BOE into steel melt. This process, developed in Germany [Oxygen Bottom Maxhutte (OBM)] and brought into maturity in USA (Q-BOP) and Japan in a large scale operation, became the predecessor of the combined blowing (top and bottom blown) BOF which dominates modern steelmaking."

Jan 1, 1996

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 G. Van Weert, A. van Sandwijk, O. W. J. S. Rutten

"Cathodic and anodic reactions in an acidic nitrate medium were studied in reference to the production of electrolytic manganese dioxide from pyrolusite' (Mn02) ores by reductive leaching. Two USA ores were investigated. The reductant for the pyrolusite ore is produced cathodically in an electrolytic cell and can either be nitrous acid (HN02) or nitric oxide gas (NO). In this work emphasis was placed on the nitrous acid leach. In a high-temperature leach in a nitrous/nitric acid medium, manganese and silver are solubilized and iron is not. Anodic electrowinning of manganese dioxide from the acidic manganese nitrate electrolyte yields flaky y-Mn02, similar to that produced from sulfate and chloride electrolytes. Cathodic regeneration of nitrorts acid was studied in a membrane cell in 1.0 M nitric acid and 0.0 to 0.1 M nitrous acid on a' platinized titanium cathode. At cathode potentials ranging from +950 to +700 mV (SHE), cathodic reduction to nitrous acid takes place, at cathode potentials < +700 mV, cathodic reduction of nitrous acid to nitric oxide takes place. A conceptual process is presented and discussed.IntroductionManganiferous-silver oresLarge reserves of manganiferous-silver ores are present in the Southwestern United States and Latin America. These ores are generally refractory to hydrometallurgical methods of treatment, due to the insolubility of the higher oxides of manganese (Mn 4+) in all common lixiviants such as cyanide solutions, dilute sulfuric acid, nitric acid, ammonia, salt solution, thiosulfates, etc. The silver is either bound by the insoluble manganese, or is rendered inaccessible to cyanide leach solution by the surrounding manganese mineralization.Higher oxides of manganese will dissolve if they are first reduced pyrometallurgically to manganous oxide (Mn2+). This is a widely used pretreatment for manganese dioxide ores and subsequent dissolution in sulfuric acid is common. In order to avoid the pyrometallurgical pretreatment with its large energy requirements and gaseous emissions, fully hydrometallurgical processes have been proposed. These processes are based on the presence of a reductant in solution, in order to reduce the insoluble higher oxides of manganese to soluble lower oxides. Aqueous S02 has been proposed and tested on industrial scale by the U.S. Bureau of Mines. After washing, silver could be extracted by cyanidation. The neutralization of the pulp prior to cyanidation however causes problems in filtration and the reagent consumptions are high [1]. More recently, acidified thiourea and bacteria were proposed for the solubilization of both manganese and silver in a single leach step. High extractions were obtained, but drawbacks of these methods are high reagent consumption or slow kinetics [2,3]. For the options of manganese recovery from the leach filtrate, precipitation with persulfate or ammonium carbonate and ion exchange have been proposed. The proposed options for silver reclaim are precipitation with either zinc or Na2S and adsorption onto activated carbon."

Jan 1, 1997

By Jean-François Boulanger

The production of rare earth elements from ore usually consists of three steps; the separation of a concentrate of REE bearing minerals; the cracking of the REE minerals to liberate the REE into an aqueous solution and separation of REE into individual elements. This paper describes the results of laboratory tests conducted on a carbonate-rich REE ore containing bastnaesite and monazite. The tests cover the whole processing sequence of beneficiation, preparation of the REE solution using a caustic leach followed by acid leach to break monazite and bastnaesite and liberate REE into an aqueous solution and the partial separation of the REE using solvent extraction. Details on the product quality and process performances (recovery and impurities removal) are given for each studied step. The paper also discusses the economic advantage of separating the REE rather than producing a mixed REO product to be sold to a refinery for REE separation. A mini-pilot plant version of the process is currently planned.

By J. L. Johnson

The U.S. Department of the Interior, Bureau of Mines, investigated recovery of concentrates containing tin, tantalum, and niobium from the Kougarok deposit on the Seward Peninsula, AK. To date, 25 million lb of tin has been delineated in occurrences containing 0.36 to 1.32 pct Sn, and the resource potential is estimated to be as high as 25 million short tons at average grades of 0.75 pct Sn, 0.025 pct Ta, and 0,025 pct Nb. Deslimed ore was concentrated to 54 pct Sn, 0.3 pct Ta, and 0.3 pct Nb, with recoveries of 74 pct Sn and 44 pct Ta/Nb using a Humphrey&apos;s* spiral followed by a Deister shaking table. Tin values in the slimes were upgraded to a 5-pct-Sn concentrate using a Bartles-Mozley separator followed by flotation. The 5- pct-Sn was further upgraded by fuming to give a concentrate containing approximately 60 pct Sn. The recovery of the two products combined was 80 pct Sn and 46 pct Ta/Nb, A flowsheet with mill-design parameters resulted from the metallurgical testing. An economic analysis was made based on the proposed process.

Jan 1, 1990

By Wang Shulan

The synthesis process of BaTiO3 from TiO2 and BaCO3 in the molten NaOH-KOH at 350oC was studied by the A.C impedance technique. The A.C. impedance of molten NaOH-KOH (xNaOH = 0.36) and the variation of the conductivity of the salt with time during the synthesized process were measured. The synthesized reaction of the BaTiO3 and the decomposition reaction of BaCO3 are fast and were finished in 10min. The interaction between TiO2, BaO and BaTiO3 and the molten salt was confirmed by the variation of the conductivity.

Jan 1, 2005

By W. K. Choi

Stainless steel exposed to wet environments at ambient temperature is subject to the formation of a surface biofilm. Depending upon the prevailing environmental conditions (dissolved oxygen, pH, Eh, concentration of cationic/anionic species), the biofilm may stimulate corrosion through formation of differential aeration zones and concentration cells. Corrosion significantly impacts the United States economy, since on a yearly basis, corrosion induced losses are estimated to be over $200 billion. A large portion of this corrosion is imputable to bacterial activity, and basic information is needed for a better understanding and control of the biocorrosion phenomenon. The present study has investigated the influence of Thiobacillus ferrooxidans in the corrosion of American Iron and Steel Institute (AISI) 304, 316 and 416 stainless steel samples. The formation of biofilm and microstructural changes on the surface of stainless steel samples and their weldments were assessed by microscopic examination, and the changes in the mechanical properties by stress-strain measurements. The significance of the results will be discussed.

Jan 1, 1993

By Autumn Fjeld

The filling and solidification of an industrial scale composite casting has been simulated to investigate the re-melting of the outer shell material during casting. Production of a composite requires a two-step casting process which includes centrifugal casting of a hard outer shell material and subsequent conventional ingot casting of a tough core material into the shell-mold assembly. During casting of the core, a thin layer of the shell material re-melts and mixes with the core material producing a bonding layer of intermediate composition. The present numerical model employs the volume of fluid method and an enthalpy-porosity technique to couple the filling of the core material and re-melting of the shell material. The interface between the two materials is tracked and can be used as a guide to examine the extent of melting and, to some degree, mixing of the two fluids and species diffusion.

Jan 1, 2008

Achieving continued economic growth with social equity within the natural limits of the Earth&apos;s &apos;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