Search Documents

By C. Burton Clark

The important role of the petrographic microscope in the petrology of refractories is discussed, based on 45 years of industrial experience by the author. Highlights of his career are used to illustrate improvements in equipment and techniques during the period. Two specific investigations are described which emphasize the interrelated use of the petrographic microscope with other instruments such as the x-ray diffractometer and scanning electron microscope. Emphasis is placed on the use of phase equilibrium diagrams for guidance in predicting and interpreting reactions that occur under non-equilibrium conditions in the manufacture and use of refractories.

Jan 1, 1982

By G. C. Gullo, H. Wabusseg, P. J. Uggowitzer, H. Kaufmann

"The basic concept of New Rheocasting (NRC) is described and the application of wrought alloys with this process is discussed. Practical experiments with the aluminium alloy AIMgSi I are explained. For this alloy the proper NRC - casting temperature was determined by using Thermo Cale - computer software and DT A and the essential processing conditions are shown. In the experiments the melt was taken from an aluminium holding furnace and cast into NRC steel cups. After controlled cooling the resulting slurries were cast into a 4-step die on an UBE HVSC 350 Squeeze Casting machine. The characteristic microstructural values such as grain size and shape factor were measured and compared with classical casting alloys. The influence of the wall thickness of the step part (6 mm, 10 mm and 14 mm) on the microstructure is described. Tensile properties in different heat treatment states are compared with characteristic prope1ties of the same alloys in forged condition. The ew Rheocasting - process CNRC)The NRC process is a recently developed new semi-solid processing method which allows the production of pore-free, pressure tight components.In the NRC process a fu lly liquid, but only slightly superheated melt is taken from a holding furnace and poured into specially designed steel crucibles, which are placed on a carousel next to the Vertical Squeeze Casting machine. In this ,NULL,slurry maker'· globul ar a-Al grains grow, following forced homogeneous nucleation at the cup wall [ 1, 2]. In the few minutes during which the melt is cooled to sem i-so lid processing temperature, a stable ske leton of a-Al phase forms. The resulting slug keeps a cylindrical shape during its slide into the sleeve of the Vertical Squeeze Casting machine, where it is cast into shape."

Jan 1, 2000

By Jose M. Gomez-Vega, Osamu Takai, Atsushi Hozumi, Hiroyuki Sugimura

"Ongoing research is reported aimed at improving the properties of mesoporous silica-based coatings on various substrates for optoelectronic or medical applications. Tetraethylorthosilicate (TEOS) was selected as the silica precursor, and amphiphilic triblock copolymers poly( ethylene oxide)- poly(propylene oxide)poly( ethylene oxide) as the surfactant micellar template or structure-directing agents. Cetyltrimethylammonium chloride (CTAC) was also used as a control agent. The effect of the templating agent and type of substrate (glass, Si, and Ti) on the mesoporosity, particularly on the alignment of the mesochannels, has been investigated. Three · different treatments (thermocalcination, photocalcination, and solvent extraction) have been also studied to remove the organic templates.IntroductionThe fabrication of mesoporous silicate-based materials through the utilization of a sol-gel process, where cooperative organization of organic and inorganic species takes place, provides a versatile approach to nanoscaled structures with potential applications in fields such as catalysts, optoelectronics, biomaterials, etc. Compared to conventional low molecular weight surfactants, self assembly of amphiphilic·block copolymers can result in mesostructured materials with larger pore sizes (up to 30 nm).1 Most of the synthetic strategies use silicon alkoxides as the silica precursor, although non-silicate metal alkoxides, e.g; Ti, Zr, Al, and B, have been also used to obtain different mesoporous materials, or even mixed metallic oxide systems. 2 Recently, Yang et al. 3 • 4 were able to synthesii:e a great variety of mesoporous metal oxides ID nonaqueous media using inorganic precursors (metal chlorides) and block copolymers as structure-directing agents."

Jan 1, 2000

By J. V. Atwood

The U.S. Bureau of Mines has developed a novel Double Membrane Electrolytic Cell (DMEC) that exhibits unique features for recycling contaminated metals and metal alloys. The DMEC incorporates two anionic ion exchange membranes, separating anodic and cathodic regions of the cell. The ion exchange membranes prevent significant transport of unwanted cationic impurities to the catholyte from the impure anolyte while the anion/cation balance in cell compartments is maintained through the free movement of anions between compartments. The membrane barrier makes it possible to electro refine highly contaminated materials or to electrowin from solution while utilizing alternate anode reactions. Sinceanolyte and catholyte cross contamination has been eliminated, premium cathode products are produced. The DMEC has been tested at bench, pilot, and commercial scales. Configuration of the DMEC, cell operation, scale, up efforts, and significant design factors are discussed. Two separate recycling investigations utilizing DMEC technology are presented. The first investigation examines recovery of high purity cobalt and nickel from severely contaminated super aIloy scrap. The second involves? upgrading contaminated cobalt in the U.S. Government's National Defense Stockpile. Capital and operating costs for both potential applications are presented.

Jan 1, 1995

By Yun Li

In 1999 Yunnan Copper Corporation (YCC) decided to modernise their copper smelter and change the existing sinter plant I electric furnace process to a combination of ISASMEL T and electric slag cleaning furnace. The main aim of the project was to improve the environmental performance and decrease the energy consumption. Generally the project has been successful, partly attributable to the selection of a reliable and fully demonstrated technology. The design capacity for the ISASMELT furnace is 600,000 tonnes of dry copper concentrate per year. The furnace has been running smoothly since heat up in May 2002. YCC expended considerable effort in the preparation for plant operation. An extensive training program for key YCC personnel at the Mount Isa Copper Smelter improved their understanding of the process significantly and ensured successful hand-over of the technology. This paper describes the project history and summarizes initial operating results.

Jan 1, 2003

By G. S. Hill

A large amount of the stereological error associated with liberation studies can he eliminated by assessing areas instead of linear intercepts. The presentation of a simple geometrical model as a stereological 'worst case' allows calculation of the worst possible grade/recovery curve for a given assemblage of areas. The true results are expected to lie in the window between this worst case and the hest possible case, represented by uncorrected data. The width of this window typically corresponds to an error margin of about 5% grade at a given recovery. An indication of where the data lies within the range of possible grade/recovery results may he obtained from a qualitative analysis of the locked section complexity. Assemblages consisting of texturally complex locked sections (ie. containing many mineral nuclei) are likely to exhibit minimal stereological bias and therefore will tend to lie close to the uncorrected side of the grade/recovery window.

Jan 11, 2011

By Ruiling DU, Jiazhi Zhang, Yong Zhao, Keng Wu

Reaction kinetics of metallurgical physical chemistry which was successfully applied in metallurgy (as ferrous metallurgy, non-ferrous metallurgy) became an important theoretical foundation for subject system of traditional metallurgy. Not only the research methods were very perfect, but also the independent structures and systems of it had been formed. One of the important tasks of metallurgical reaction engineering was the simulation of metallurgical process. And then, the mechanism of reaction process and the conversion time points of different control links should be obtained accurately. Therefore, the research methods and results of reaction kinetics in metallurgical physical chemistry were not very suitable for metallurgical reaction engineering. In order to provide the definite conditions of transmission, reaction kinetics parameters and the conversion time points of different control links for solving the transmission and reaction equations in metallurgical reaction engineering, a new method for researching kinetics mechanisms in metallurgical reaction engineering was proposed ,which was named stepwise attempt method. Then the comparison of results between the two methods and the further development of stepwise attempt method were discussed in this paper. As a new research method for reaction kinetics in metallurgical reaction engineering, stepwise attempt method could not only satisfy the development of metallurgical reaction engineering, but also provide necessary guarantees for establishing its independent subject system.

Jan 1, 2015

By Xie Zhang, Chongyang Zhao, Qingyun Huang, Bing Xie, Xiaopeng Zhen

"Extracting vanadium from vanadium containing hot metal into vanadium slag by BOF is the main vanadium production process in China. In this paper, the influence of Si content in hot metal on the quality of vanadium slag is analyzed. Synthetic vanadium slag with different SiO2 content were melted at 1673 K and then cooled to 303K at the cooling rate of 3?/min. Optical microscopy, SEM, EDS and XRD were used to analyze the mineralogical phases and crystallization behavior of vanadium slag. The results show that vanadium slag mainly contains spinel phase and silicate phase; V is enriched in the spinel phases while Si is concentrated in Fe2SiO4 CaFeSi2O6 and (Fe,Mn)2SiO4 as silicate phase. The melting point of slag increases gradually with the addition of SiO2; whereas viscosity decreases with an addition of 15~19% SiO2 and increases with an addition of 19~27% SiO2.IntroductionVanadium is an important element which is used almost exclusively in ferrous and non-ferrous alloys. The major vanadium products include FeV, V2O5, V2O3, VN and Al-V-Ti alloy. Furthermore, vanadium slags are mostly produced by oxidizing the elements in V-containing hot metal during a duplex refining process. Therefore, the process of removing vanadium from hot metal has its significance on the subsequent process[1].The extraction of vanadium is greatly affected by the mineralogical composition of vanadium slag[2], the distribution of the elements between the spinel and silicate phases and its physic-chemical properties. These characteristics of vanadium slag have been studied in some details. It has been reported that Si mainly exists mainly in the form of silicate which wraps the spinel crystals while small amount of Si stands as phosphorus quartz or diopside[2]. Chen et al.[3, 4] points out, when SiO2 content in vanadium slag increased every 1%, V2O5 decreased 1.48%. Moreover, silicate phases would embarrass the oxidation of V-containing spinels through decreasing the exposing probability[5]. Meanwhile, melting point and viscosity of vanadium slag has been greatly influenced by the SiO2 content. Therefore, this work attempts to analyze the above-mentioned questions systematically."

Jan 1, 2012

By Kenneth P. Michalek, James E. Kelly, Jonathan A. Dantzig

"Many investigations have been reported regarding the simulation of continuous casting with emphasis on in-mold heat transfer. These analyses have been limited, however, because they require either estimation or measurement of the characteristic heat transfer between the ingot and the mold. In this paper, a self-consistent model 'is presented for calculating the heat transfer between a solidifying continuous casting and the mold, in the context of the continuous casting of steel. Using both thermal and stress analyses, the air gap formed during continuous casting is calculated and used to compute the heat transfer coefficients. Iteration between the thermal and stress analyses is used to determine a self-consistent solution. IntroductionThe continuous casting process for steel is illustrated schematically in Fig. 1. Molten steel is tapped into a tundish from which it flows at a controlled rate into the continuous casting mold. The initial shell of the casting forms in the mold by transfer of heat from the metal through the mold wall to the cooling water. The remainder of the casting is solidified by application of water sprays, and/or radiation cooling below the mold.Heat transfer in the mold portion of the process is important because it controls the formation of various defects which are deleterious to subsequent processing. Examples of defects formed in this region are surface irregularities, such as cold folding and oscillation marks, and more serious defects, such as longitudinal or transverse cracks. A more catastrophic problem which may occur is a breakout, in which the shell ruptures and molten steel is discharged in an uncontrolled way."

Jan 1, 1986

By Priscilla Aki Mori de Hanashiro, Viviane Tavares de Moraes, Denise Crocce Romano Espinosa, Hugo Hashimoto

"The LCDs are used in televisions, calculators, mobile phones, computers (laptops and tablets), video games and other electronic devices. The advancements in technology make obsolete these devices, causing excessive disposal of LCDs and therefore decreasing life span of landfills. In this context, the LCDs from LED LCD TVs arise as an additional source of waste electrical and electronic equipment (WEEE). Thus, it is essential to develop LCDs recycling methods, beginning with the LCD characterization followed by displays processing, aiming the materials separation and using some Ore Treatment Techniques, and finally, the recovery of indium using acid leaching. The analysis methods that will be used in this work are: Fourier Transform Infrared (FT-IR) and Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES).IntroductionLiquid Crystal Display (LCD) technology is applied in modem televisions, calculators, mobile phones, computers and a wide range of electronic devices. It has replaced Cathode Ray Tube (CRT) technology as the most advantageous display product, due to lower electrical power consumption, size and weight reduction, and no radiation emission [ 1]. The constant improving of LCD screen technology reflects on its growing contribution to the amount of waste electrical and electronic equipment (WEEE): an estimated 50 million tons of WEEE are produced every year [2]. Once the most common method of its disposal are landfills, the LCD technology therefore became an environment issue [3].LCD structure is composed by components made by different materials. In order to develop a LCD recycling methodology that gives the right destination to these materials, a previous characterization stage is required. This characterization includes a disassembly process and material identification analysis. One of the LCD components is the screen, which is composed by polymeric and glass layers. The liquid crystal glass was the starting material of this study. It contains indium in the form of indium tin oxide (ITO) film. This ITO film is deposited in the glass by a sputtering process and acts as the electrode material [4,5]. It has in its composition 90% ofln203 and 10% ofSn02 [6]."

Jan 1, 2014

By G. G. Krishna Murthy

Several experiments were carried out to simulate the bath smelting reactions where iron oxide particles were dropped on to an iron-carbon bath containing molten CaO-SiO2-Al2O3 slag layer on its surface. The composition of the slags used in the experiments was %CaO:46.1; %SiO2:41.7; and %A1203:12.2. Experiments were con¬ducted with carbon saturated iron melts contained in either a pure graphite crucible whose walls were covered with a pure alumina tube, or a pure flat bottom alumina crucible, at 1723-1823 K. Degree of reduction of a pure iron oxide particle was linear with time in the initial stages (up to about 20% oxygen of the original pellet was reduced). The rate of reduction of smaller oxide pellets was smaller than that of a bigger pellet - the time for complete reduction of a 5.6 g wustite pellet was smaller than that for a 1.2 g wustite pellet. It was also established that the interaction rates obtained by adding a molten pure oxide particle of given weight to the system were lower than that determined by using a solid oxide particle of same weight. The overall rates of reduction decreased with decreasing the bath temperature. The experimentally determined rates of reduction based on the time for 70% reduction were influenced substantially by addition of slag up to about 50 g on to a bath of 78.8 mm in diameter, and remained constant when slag present on the bath surface was between 50 g and 200 g.

Jan 1, 1993

By T. Asahina, M. Nakamura, M. Mabuchi, I. Shigematsu, M. Nakanishi, G. Yamauchi

"Commercial stainless steels (SUS304L and SUS430) were subjected to equal channel angular extrusion (ECAE) at room temperature to a total strain of 2.3 to 9.2. For each type of stainless steel, it was shown that the sample processed by ECAE showed higher room temperature strength than the as-quenched sample. This is probably due to the heavily worked structure. On the other hand, both strength and elongation of the ECAE processed SUS430 were increased by annealing at 773K. It is likely that higher strength is attributed to both the heavily worked structure and fine substructures. It is also likely that higher elongation is attributed to the fine substructures. It is concluded that ECAE is available for improving the room temperature strength of commercial stainless steels.INTRODUCTIONEqual channel angular extrusion ( ECAE ) is a technique that provides the repetitive deformation and allows to high intensity of deformation. With this procedure, a sample is pressed through a channel that has an equal cross section but bent at an angle of ?> [1-2]. Shear strain is introduced when a sample passes through the bending point of the channel. Repetitive processing is feasible because the cross-sectional dimension of a sample has no change during processing. To date, many reports have described that ECAE is available for the fabrication of fine-grained materials [3-14]. On the other hand, an ECAE processed sample can achieve high intensity of deformation through repetitive deformation. According to the equation given by Segal [ 2 ], a strain of about 1 is introduced in each pass through die if the angle ? is 90 deg.It is well known that high tensile strength can be achieved in metallic materials through work hardening [15]. It is also known that metallic materials with fine grain size show high strength [16]. Hence, it is expected that ECAE is available for strengthening method in metallic materials. In the present paper, we will report the mechanical properties of stainless steels processed by ECAE. As samples, SUS304L austenite stainless steel and SUS430 ferritic stainless steel were chosen. Each alloy has a single-phase structure (fee or bee) and shows no phase transformation, so that transformation strengthening cannot be applied. Hence, a heavy cold work such as ECAE may be effective for strengthening of this stainless steel. Annealing was conducted for the ECAE processed SUS430 to vary its microstructure. Then, the effect of annealing on the strength of the ECAE processed SUS430 was also investigated."

Jan 1, 2000

By Jin-yan TIE, Ke-xin JIAO, Qian Li, Hai-bin ZUO, Jian-Liang Zhang, Meng SHEN

This paper designs three factors such as temperature, pH, conductivity and three levels of orthogonal test. Temperature is a significant factor. However PH and conductivity are not significant through poor analysis. Further research is conducted on the temperature. Temperature stability is 50 . Suitable water velocity is 2.3m/s, which is calculated based on the largest part of the heat flux intensity and the corresponding water temperature should be controlled with 1.5. Meanwhile, water velocity increased has little effect on the heat transfer capabilities.

Jan 1, 2015

By Chunhua Liao, Chao Peng, Guangsheng Huo

To get the separation of tungsten and molybdenum, we adjusted the pH of the solution to 7, at which tungstate (WO4 2-) will be polymerized into HW6O21 5-, while molybdate will still exist in the form of MoO4 2-. Two strongly basic anion exchange resins (D201, D213) were experimented for the separation of tungsten and molybdenum. The results of condition experiments indicate that D213 resin performs better in the treatment of lower concentration solution A (WO3 10g/L, Mo 4.12g/L) with a separation factor as high as 10.64. While D201 resin is more suitable for the high concentration solution B (WO3 70g/L, Mo 28.97g/L) with a separation factor of 6.9. The results of column testing performed on D213 resin show that the solution after loading process with a mass ratio of Mo/WO3 = 50 and the desorption solution with a mass ratio of WO3/Mo = 27 can be obtained

Jan 1, 2014

By Gerardo R. F. Alvear, Alistair S. Burrows, Stanko Nikolic, James S. Edwards

"The copper ISASMELT™ process has evolved over more than a quarter of a century and can now be considered mainstream, with single furnaces producing more than 340,000 tpa of copper in matte. The next evolutionary step for the ISASMELT™ technology is to directly challenge the dominance of the Peirce-Smith converter by the implementation of a continuous copper converting process on a commercial scale. The present work describes the status of the continuous converting process – ISACONVERT™.Continuous converting has been performed successfully in pilot scale ISACONVERT™ plants, where operating results have verified the predictions of fundamental research and reinforced the underlying confidence in the design parameters. From a matte feed rate of 250 kg/hr, a calcium ferrite slag and a low-sulfur blister have been produced. Design is now complete for the first commercial application of the ISACONVERT™ process. The present paper describes the status of ISACONVERT™ by summarising results of recent pilot plant tests and describing the first commercial plant design."

Jan 1, 2009

By V. A. Luganav

The behavior of arsenopyrite under heating has been studied by many scientists. It has been already established that under heating at more than 650°c and without air access the arsenopyrite dissociates with the formation of one atom arsenic. Under vacuum the dissociation process begins at 5500C with the formation of elemental arsenic. The residue of dissociation process contains pyrrhotite and throilite. In the presence of pyrite, arsenopyrite dissociates under lower temperature and with a higher velocity than without it. The industrial realization of fool scale processing of arsenic bearing raw materials is possible only by the use of standard equipment and oxygen containing blast. In this view the paper presents the results of the study on the effect of oxygen in the gaseous phase and its addition into the charge of pyrite in the process of arsenopyrite decomposition. Thermodynamic analyses showed that under thermal processing of arsenopyrite in the presence of pyrite and limited quantities of oxygen in the gaseous phase the formation of arsenic sulfides is possible according to the following reactions:

Jan 1, 2003

By Wenzhou Yu, Cong Zhang, Wenhui Ma, Gang Wang, Kuixian Wei

"A novel technique was successfully developed for nickel further purification by vacuum directional solidification. The removal effect of impurities in nickel was studied based on theoretical analysis and experiments. High removal efficiency of impurities in nickel can be realized according to theoretical analysis. The experimental results show that the vacuum directional solidification treatment could increase the nickel purity from 99.96% to 99.996%. Since vacuum directional solidification could effectively remove the impurities from nickel with low contamination and low cost, it is a potential route to obtain high-purity nickel for commercial application.IntroductionNickel is widely used in metallurgy, machinery, petroleum industry, chemical industry, construction industry, light industry, and other industries for its ductility, medium hardness, ferromagnetism and high chemical activity. Nickel-based alloy is an important material for the key parts of aircraft, tanks, submarines, radars, nuclear reactors and aerospace fields [1-5]. Generally, nickel contains Si, P, S, Fe, Cu, Zn, As, Cd, Sn, Sb, Pb, Bi, Al, Mn, Mg and other impurity elements, which may hinder the commercial application of nickel. Therefore, it is necessary to refine the crude nickel for the high purity nickel."

Jan 1, 2014

By Niels Verbaan

NioCorp is developing the niobium/scandium/titanium Elk Creek carbonatite deposit. The probable reserve announced by the company in 2017 indicated significant niobium (0.79% Nb2O5), titanium (2.81% TiO2), and scandium (71 g/t), and is composed predominantly of calcite, dolomite, and ankerite. Niobium is mostly (80%) contained in pyrochlore with the balance in various Fe-Nb-Ti oxides, which also host most of the titanium. Scandium is primarily deported in dolomite, with lesser quantities in pyrochlore and biotite. The process flowsheet recovers separate niobium, titanium, and scandium products. Scandium is extracted from whole ore hydrochloric acid leach solutions using solvent extraction and is further refined through a re-leach and precipitation process. Scandium leach residues are treated in a sulphuric acid sulphation process to recover separate niobium and titanium precipitates as well as to solubilize the remaining scandium. Both hydrochloric acid and sulphuric acid reagents are recycled within the flowsheet. This paper will discuss key bench and pilot test results of the niobium extraction and recovery circuits and will present a conceptual flowsheet developed by the project team for NioCorp at SGS Minerals.

By D. B. Dreisinger, V. van der Pas

Zinc sulphate electrolyte used for zinc electrowinning must be purified for cObalt ions. The cobalt is removed in a cementation stage by the addition of zinc dust. Copper arid antimony are frequently used additives which enhance the cementation of cobalt. This paper aims at a better understanding of how copper and antimony promote the removal of cobalt. Initial experiments were done in a batch cementation reactor. Copper and antimony precipitated in the early stages of cementation indicating that a preferential substrate was formed. The individual role of copper and antimony was further investigated in an electrochemical cell. On a microsca1e, the , growth process, morphology and the composition of the precipitates were examined with SEM and XRD. It was found that cobalt could not be deposited in its pure form but as a cobalt-zinc alloy with zinc as the prime constituent. Copper increases the cathodic surface area of zinc dust by precipitating as numerous dendrites. Antimony acts as a cathodic surface onto which a cobalt-zinc alloy with an increased cobalt content is deposited.

Jan 1, 1997

By Yuan-bo Zhang, Gui-hong Han, Yan-fang Huang, Tao Jiang, Guang-hui Li

"Under isothermal conditions, the reduction behavior of oxidized pellets balled with bentonite was investigated with CO-CO2gas mixers in the temperature range from 900°C to 1100°C. The whole reduction of oxidized pellets was followed up by means of weight-loss technique. And the swelling index of pellets was examined by visualizing physical changes of pellet in a horizontal tube furnace. The results present that the reduction rate of oxidized pellets is increased with the increase of reduction temperature. While the swelling index is firstly increased and then decreased with the increase of reduction time and reduction extent, which can be ascribed to the disruptive stresses induced during the transformation of hematite to magnetite. The maximum swelling index is gradually increased with the increase of reduction temperature and CO content.IntroductionWith the rapidly development of iron and steel industry, direct reduction iron has been considered as one kind of high quality burdens in electric furnace steelmaking [1]. At present, ""Two-step"" coal-based direct reduction process, which employs oxidized pellets as raw materials, has been used in industrial production [2]. The reduction behavior of iron ore oxidized pellets has been becoming one of the most frequently studied topics in extractive metallurgy[3]. The heat and mass transfer in direct reduction processes results in a series of stepwise reduction reaction (hematite--magnetite--wustite--iron), accompany with the volumetric swelling of pellets[4]. A lot of literatures have been reported on the reduction model of ferrous oxides and swelling behavior of pellets. A. A. El-Geassy K, et.al [5-7] revealed that the reduction process was controlled by chemical reaction at early stage by employing pure Fe203 as raw materials and CO as reduction gas. Chen Y [8] made research on the reduction kinetics of porous oxidized pellets and obtained the rate constant and activation energy of at different reduction stage. In addition, the swelling and disintegration of iron ore pellets was affected by chemical composition of pellet and reducing parameters, which have been studied by numerous investigators [3,9, 1O]."

Jan 1, 2013