Search Documents

By Stephen J. Hales

State-of-the-art Resistance Spot Welding (RSW) equipment has the potential to permit adaptive feedback through recent advances in computerized process control. The initial step toward achieving this goal involves assessment of the effect of specific variables and the interaction between these process inputs on spot weld characteristics. This investigation addresses this issue through the application of Taguchi methodology to understand and refine a RSW schedule developed for joining of two dissimilar aluminum-lithium (AI-Li) alloys of different nominal thickness. The experiment was designed to establish a hierarchy of inputs with respect to each 'other, and to determine the significance of these inputs with respect to experimental noise. Valuable insight was gained regarding the interaction between process variables and the effect of certain equipment-related changes. In spite of a decrease in equipment performance, an improvement in the maximum strength attainable for defect-free spot welds resulted from the application of the statistical experiment.

Jan 1, 1992

By Y. Ide, K. Kishitake

It is expected that an Al-Cr-N composite nitride film may have a higher resistance to oxidation at elevated temperatures than the well-known Ti-Al-N films. The formation conditions of Al-Cr-N films by a de reactive sputtering method and their properties were studied in this study. The films characterized with respect to their high temperature properties such as chemical composition, crystal structure, microhardness, wear and· friction. The crystal structure of the Al-Cr-N films changed from hexagonal phase to cubic phase with an increase in Cr content in the films. The resistivity to thermal oxidation of the Al-Cr-N films is superior to that of usual TI-Al-N films. A half of the friction coefficient in the Al-Cr-N film was obtained comparing with that in the ordinary TI-Al-N film at room temperature and the wear rate of Al-Cr-N film was 2 order smaller than that of TI-Al-N film. The Al-Cr-N films show a small friction coefficient at 500°C and then they are recognized to have good tribological characteristics.

Jan 1, 2000

By Y. Maeda

Non-ferrous smelting furnaces generally lnstal1 a gas cooling system for treatment of waste gas containing S02. From the point of view of corrosion resistance and recovery of waste heat, the high pressure boiler system Is the best way to cool gas, however this system requires high Initial investment and relatively higher operating costs. Because the feasibility of this boiler system greatly depends on the smelting process and scale, other lower temperature systems, e.g. water-cooled Jacket system, are more suitable If the smelting process does not produce enough steam nor generate enough electricity to compensate operating cost. In addition, the water-cooled Jacket system Is simple in structure and easy to operate. For those reasons, it is applied widely. A new smelting furnace. was planned tin our factory and It was necessary to install waste gas cooling equipment. In our case, a water-cooled Jacket system was mo11e feasible because of the low gas volume and high dust content. H was also expected to operate without maintenance for ten years. On the other hand, some leakage problems with the water-cool1ed Jacket had been experienced In the past. That is because S02 in the waste gas changed into sulfuric acid which corroded the Jacket material, As the first step, several data from actual usage were reviewed to throw light on the corrosion process, and an appropriate procedure to determine the operating temperature of cooling water was obtained. For the basis of this study, a water-cooled Jacket system was newly designed and tested for three months in a pilot plant. After this system's performance was confirmed, It was installed In a new furnace as a commercial pl.ant. After one year of operation, the initial thickness of carbon steel Jacket remains almost the same.

Jan 1, 1992

By D. W. Ashman

The zinc pressure leaching plant at Cominco's Trail Operations is now in its ninth year of production. The plant produces a zinc sulphate and jarosite slurry which is further processed in the calcine leaching circuit. Elemental sulphur, a by-product of the process, is sold in the North American market. During the past eight years, a number of changes have been made to the plant to remove known production bottlenecks and to improve leaching extraction. These changes have raised production rates above the initial design so that the plant currently accounts for approximately 20 percent of Trail s zinc production. These rates are expected to be increased further upon the completion of the alterations currently in progress. The knowledge gained over the operating life of this plant has allowed Cominco to plan for a possible future expansion of the zinc pressure leaching plant. If expanded, zinc pressure leaching would account for approximately 48 percent of cominco?s zinc production.

Jan 1, 1990

By Q. G. Liu

New solid-state electrochemical sensors 1;.1sing Li2SO4-Ag2SO4 electrolytes have been developed to measure SO2 and/or SO3 in gas mixtures. Silver embedded in part of the electrolyte is used as the reference electrode. Although single-phase electrolyte sensors yield accurate results for one to two days, a two-phase electrolyte cell exhibits excellent long-term chemical stability. For example, stable and accurate potent iometric responses have been obtained over a six mo.nth period. The. advantages of the two-phase electrolyte ( 23 mol% Ay 2SO4 ) cell include excellent mechanical strength on temperature cycling and an insensitivity to compositional variations in the electrolyte and to temperature fluctuations. Experimental tests have shown excell.ent results in SO2-air. mixtures with the SO2 concentration ranging from 3 to 10,000 ppm (vol). However, the SO2 concentration range was limited by a lack of standard gas mixtures, and our sensor cells can be used to measure S02 concentrations significantly less than or larger than our experimental range. Results also indicate that the presence of significant concentrations of CO2 and H2O in the gas mixture has no effect on the sensor response. Thus the two-phase electrolyte ( 23 mol% Ag2S04) sensor has exceptional selectivity, reliability and long-term chemical and mechanical stability.

Jan 1, 1985

By Kimura. E.

Continuous estimation of phosphorus content of molten copper is required to produce phosphorus deoxidized copper in a continuous casting operation. The phosphorus content of molten copper was related to its electric resistivity, which was measured by the four-probed technique with a specially-shaped cell. In a laboratory scale, the linear relationship between the above factors was confirmed in the temperature range of 1083OC through 1200°C. The phosphorus concentration range measured was from 40 to 500 ppm. The phosphorus content was monitored successfully by measuring the electric resistivity of the molten copper in the distributor of a continuous caster in an industrial scale.

Jan 1, 1992

By Hartmut Rossel

VAW aluminium AG has built a "Recycling-Technikum" (Recycling Research Centre) to add a new arm to the company's Corporate Research and Development Department. The Recycling Research Centre, a pilot plant for scientific research, has been in operation since September 1993. These state-of-the-art facilities allow the investigation and optimisation of recycling techniques in 'a global way and in detail. Research is concentrated on the unit operations - processing, melting and waste-gas purification - with the available installations making it possible to compare different alternative process combinations on a 100-kg scale. One of the main targets of VAW research is the development of recycling techniques for packaging. The paper presents an approach to recover the aluminium contained in flexible packaging materials using an integrated melting and waste-gas purification system.

Jan 1, 1995

By Zhang Yongzhu

The metallogeneticy and mineralogy of three types of Chinese refractory gold deposits (Au-As; Au-As-MeS; Au-As-C) which are somewhat different from those abroad are discussed. The modes of occurrence, the distribution of grain size, and the morphological features of gold in minerals and their influences on gold recovery by direct cyanidation are also discussed. According to the mineralogy of gold and minerals, bacterial leaching, pressure leaching and roasting technology are suitable for the pretreatment of arsenopyrite-Au, pyrite-Au and carbonaceous-clay-Au refractory gold ores prior to cyanidation, respectively. The most important sulfide pyrite bearing much gold is difficult to be oxidized, its crystalline structure, conduct-types , and minor elements in different mineralizing stages are also discussed. The pyrite aggregates in different deposits are very complicated and much different. Gold grade of arsenopyrite is much higher than that of pyrite for some deposits which have a high correlation coefficient of Au vs As.

Jan 1, 1992

By Garry W. Warren

The brass foundry industry produces a significant amount of waste sand containing Cu, Zn and Pb which is often classified as a hazardous waste due to Pb content. The potential application of a hydrometallurgical process to treat the sand by extracting metal values and thus detoxifying the material has been investigated. The process involves leaching of metal values followed by cementation. The emphasis of this investigation was on the leaching step, although some preliminary cementation experiments have been performed. In order for any alternative treatment scheme to be successful, the smaller size fractions of the sand must be addressed. Experiments have been performed on five individual size fractions using various lixiviants HCI, acetic acid and HCI/NaCI. Cu extraction was found to be slower than either Zn or Pb. Results obtained in this investigation indicate that copper is present in two forms, an oxide form which dissolves rapidly and is insensitive to the level of oxygen, and a less soluble form, probably metallic which dissolves more slowly and requires an oxidizing agent. The presence or absence of oxygen had no influence on the rate of Zn dissolution indicating that zinc is present mostly in oxide form. Toxicity Characteristic Leaching Procedure (TCLP) tests showed that residues could be produced which meet the toxicity limit for lead. Preliminary cementation experiments have also demonstrated the feasibility of Cu and Pb recovery.

Jan 1, 1991

By Jefferson Caponero

The tire is an expressive component of Municipal Solid Waste, manly when its occupied volume is considered. Its treatment by pyrolysis stands for a list of advantages, such as: landfill releasing and a production of a high quality fuel. The exploitation of new natural resources is becoming more difficult each day, basically due to the environmental damages caused by this type of activity. This work presents a study on the thermal behaviour of Brazilian tires using thermogravimetric analysis and differential thermal analysis, in order to optimise the pyrolysis process of tires. Samples of I to 2 mm were investigated at atmospheres of nitrogen, argon, oxygen and mixtures of these gases at temperatures up to 1273K, under heating rates between 1 to 50 Klmin . The results showed that the behaviour of each sample is related to both the atmosphere composition and the heating rate.

Jan 1, 2001

By Yutaka Shiraishi

Two methods were developed to measure the viscosity of the slag from the glassy to the liquid states in an ascending temperature process. The first method employs rotating parallel plates within which is placed a solid cylindrical sample in line with a sphere. The second method uses a tube which is pushed into a sample held in a rotating crucible. Both methods were tested using standard glasses, including boron trioxide and NBS standard glass #711. The main difference between these two methods is in sample preparation. Comparative measurements between two methods were performed using a sodium boro-disilicate glass containing 5%mol of alumina. The results showed good agreement in the mid-range of glassy viscosities, 105 to 107 Pa.s. In the liquid state, there were no significant differences between the two methods.

Jan 1, 2003

By C. B. Solnordal, R. N. Taylor

"The heat transfer conditions on the outer side of a Sirosmelt lance have been determined using experimental measurements in combination with a mathematical model. By measuring the temperature distribution along the wall of an operating Sirosmelt lance, as well as the thickness of the slag layer on it, it was possible to use the model to determine both the heat transfer coefficient between the vessel contents and the lance, as well as the effective thermal conductivity of the slag layer. The effective thermal conductivity of the slag layer was found to be within the range 0.7-1.3 W.m-1. ºCl, which was in good agreement with measured values for magnetite. The outside heat transfer coefficient varied from 80 to ISO W.m-2. ºC1, which was smaller than quoted in the literature for metal/slag systems. The discrepancy was attributed to the high thermal resistance experienced between the lance wall and the slag layer, as well as the large quantities of combustion gases that envelop the lance tip and reduce convection and conduction from the melt to the lance. INTRODUCTIONThe Sirosmelt submerged combustion smelting process [1] utilizes top injection lances to deliver fuel and air into a metallurgical melt. To help prevent lance failure from attack by liquid slag, helical vane swirlers are used within the annular lance to impart swirl to the flowing air and enhance the heat transfer from the lance wall to the air. The swirlers thus cool the wall, and enable a frozen layer of slag to form on its outer surface. This solid layer ensures liquid slag cannot reach the lance surface, and the lance is protected.A mathematical model of the heat transfer processes associated with the lance has been developed, which combines heat balance equations with engineering correlations to predict the wall and cooling air temperature of the lance, as well as the air pressure distribution. An account of the model was given by Rankin et al. [2]. To further enhance the model and enable it to predict the thickness of slag accumulating on the lance, a detailed analysis of the heat flow through the slag layer commenced in 1992. By far the most complex aspect of the model, the flow of heat from the vessel contents to the outside of the lance was dependent on many factors, including:-"

Jan 1, 1996

By John Pilling

The concept of microstructure, its evolution through materials processing and its effect on the properties of the material is, perhaps, the foundation upon which the science of materials is built. PHAUST, a computer aided learning program, attempts to provide instruction in establishing the relationships between phase diagrams, thermal processing and microstructure. Using phase diagrams derived from a database or created by the user, the evolution of microstructure during processing is quantified using the lever rule and/or the Scheil equation and tracked through a doubly linked list (a form of binary tree). Microstructures, in the form of full colour cartoons are then drawn using the quantitative and logical information contained within the linked list using bitmapped templates and logigal operators such as NOT. AND, OR and XOR, giving the student a view of the structure as it would be seen under the optical microscope. The software provides complete diagnostics of student answers, locates errors and misconceptions as well as providing tutoring towards the correct solution method and answer.

Jan 1, 1991

By T. Ikeda, M. Maeda, K. Mita

Galvanized steel sheet is the major product for the automobile industry. Therefore, automotive recycling results in zinc-containing scrap that should be remelted in EAFs. Naturally, the EAF dust is a very important source of zinc for zinc recycling processes. The thermodynamic properties of the Fe-Zn intermetallic compounds formed on the surface of galvanized steel sheet should be clarified to make clear the evaporation mechanism of zinc; however, there are few reports on these compounds because of difficulties in their synthesis. There are various intermetallic compounds in the Fe-Zn system. We synthesized them at about 673K. A specimen was examined chemically and X-ray diffraction was applied to ensure the formation of intermetallic compounds. Material containing two phases was placed in a Knudsen type effusion cell and the mass spectrum studied to evaluate the vapor pressure of zinc. The thermodynamic property of intermetallics was then evaluated through measured intensity.

Jan 1, 2000

By Tatsuzo Kitamura

The tank house of Tamano refinery, that started its operation in January, 1972, was constructed incorporating the application of Periodic Reverse Current (P.R.C.) from the outset of design works. In 1973, the production of electrolytic copper came up to 8,000 mtpm, a sharp increase ds compared with the designed capacity of 7,000 mtpm, and successful operation has been achieved up to the present. P.R.C. has been employed for the purpose of raising productivity level and reducing copper inventories. Since there were various problems in P.R.C. application to such a large sized cathode as 1 m x 1 m, special attentions were paid to the following items: -Development of a unique bus bar to make an electrolytic current to each electrode as uniform as possible. -Improvement of circulating method of electrolyte. -Application of high-performance equipment to realize a uniform spacing between anode and cathode. Owing to these creative technical developments mentioned above, technical level for operation up to 350 amp per sq m of cathode current density has been established. The quality of electrolytic copper, which was a matter of interest, has been proved to be as excellent as those of conventional electrolysis products through a long term supply to the field of SCR and Dip forming where high levels in quality are required.

Jan 1, 1976

By J. M. D. Wilson

An analytical program using a combination of SEM-based image analysis techniques is developed for automated modal analysis of ores containing silicate and other gangue minerals. Previous knowledge, gathered by means of either optical microscopy, X-ray diffraction, SEM, or electron microprobe analysis is used to establish discrimination criteria in the image analysis program. The program initially discriminates minerals on the basis of their relative grey values in a backscattered electron image. For those minerals which have overlapping grey levels the minerals are identified by the program using energy dispersive X-ray spectrometry with X-ray counting for twelve or more elements. This technique is useful to quantify ores in which the gangue minerals are numerous. Two cases of application are presented.

Jan 1, 1999

By I. Gaballah

High and low grade concentrates of tantalum and niobium oxides were obtained by leaching a medium grade tin slag. Chlorination and carbochlorinalion of these concentrates were studied between 200 and 1000 "C. Chlorination or carbochlorination of the low grade concentrate led, at 1000 OC, to the extraction of about 95 % of the tantalum and niobium oxides. However, the tantalum and niobium chlorinated compounds were contaminated by iron and manganese chlorides. Complete extraction of the niobium and tantalum pentoxide was achieved during the carbochlorination of the high grade concentrate at 300 and 500 "C, respectively. While chlorination of this concentrate at 1000 "C, allowed to the volatilization of about 60 and 80 % of Ta205 and Nb205. In both cases, condensates were composed of almost pure tantalum and niobium chlorinated compounds. The results demonstrate the advantages of the lixivialion based on the "pseudo- structure" of the raw tin slag to obtain the high grade concentrate. The conclusions of this work suggest that the carbochlorination of the high grade concentrate is an efficient process for the extraction of refractory elements from tin slag.

Jan 1, 1993

By Hideaki Tokuyama

Recovery of Ni from acidic wastewater of metal surface treatment has been investigated for reuse of the metal and water. Ion exchange equilibria between Ni ion and a strong acid cation resin, DIAION SKIB, and effective diffusivity in resin particle have been studied and they related to the concentration of HCI. The amount of adsorbed Ni for unit quantity of resin decreases with the increase in HCI concentration. This trend is remarkable for acid concentration above 0.1 kmol/m3,. The exchanging ratio of Ni2+ to H+ in resin particle is I/2 and the values of equilibrium coefficient K and maximum exchange capacity Q are I.62 and 3.16 keq/m3 -dry resin, respectively. Effective diffusivity D. determined from the observed breakthrough curve increases with increasing concentration of DC!. A prototype of moving bed has been developed and applied for the recovery of Ni from model solutions of wastewater prepared by mixing HCl and NiCl2. This apparatus allows us to control the resin flow rate by changing the cross sectional area of hole I the Teflon plate installed at the bottom of resin bed. Characteristics of Ni recovery have been clarified under various liquid flow rates. In any case for Q1, Ni ion has been effectively recovered on SKIB resin and the removed fraction was more than 99.5 %. Higher loading ratio of ion is attained at larger liquid flow rate.

Jan 1, 2003

By Batric Pesic

Dissolution of gold with sodium bromate solutions of various compositions was studied by using a rotating disc technique. The role of bromide ion, acid and externally added bromine was examined. It was found that sodium bromate could not dissolve gold in the absence of either acid or bromide ion, or both. When acid was absent, no bromine necessary for gold dissolution could be produced. When bromide ion was absent, formation of soluble gold bromide species, AuBr,-, was not possible. Bromate concentration had a complex effect, and it was dependant on bromide ion concentration. For fixed initial bromide ion concentration, gold dissolution rate increased with sodium bramate concentration increase until certain level, beyond which further increase of bromate concentration decreased the gold dissolution rate. The negative effect of bromate was explained by the depletion of necessary bromide ion. Sulfuric acid concentration effect was a function of initially present bromine.

Jan 1, 1992

By M. P. Bohrer

A closed-loop hydrometallurgical process has been developed for treatment of smelter flue dust generated by copper recycling. The process is a semi-continuous operation in which zinc, iron, and copper are first extracted from the dust with a sulfuric acid solution. The lead and precious metals, initially present in the dust, remain as solids and can be recycled to the copper smelting furnace. Cementation with iron and zinc metal purifies the zinc and iron-rich liquid stream prior to spray drying. The spray-dried product, consisting of a mixture of zinc sulfate monohydrate and iron sulfate monohydrate, is a desirable micronutrient additive for use in animal feeds. Treatment of the smelter flue dust in this manner will generate a positive return on investment, as well as mitigate a potential environmental liability.

Jan 1, 1992