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By A. -M. Lafront

The corrosion resistance of die-cast and freely-solidified and electromagnetically-stirred thixocast AZ91D alloy has been studied using electrochemical noise technique in a 0.05M NaCI solution at pH 6.1 and 25°C. Specimens polished at different depths were immersed for a period of 75 min in order to assess the influence of the microstructure on corrosion kinetics and morphology. At depths between 10 and 50 µm (skin), all specimens showed general non-uniform corrosion with the lowest corrosion resistance. Between 100 and 200 µmn (interior skin), the observed corrosion was accompanied by superficial undefined pits due to metastable pitting. The corrosion form for 100-200 µm gave the best corrosion resistance. Stable pitting corrosion was observed beyond 400 µm deep on the bulk specimens. The skin of all thixocast specimens prepared billets showed a more corroded surface than that of die-cast. The interior skin as well as the bulk specimens showed better performance than that of the die-cast specimens.

Jan 1, 2007

By I. Farr, H. Wittens

"In 1989 and 1990 abnormally high levels of arsenic in ore from the Thompson Open Pit Mine threatened Manitoba Division's electro-nickel production. The paper will discuss our development of a flotation process to separate pentlandite and gersdorffite (the prime nickel and arsenic bearing minerals).The presentation will focus on the development of the process from conception, through lab and plant test work, to plant optimization and full scale production. The paper will conclude with the benefits and cost of the completed project.INTRODUCTIONRejection of arsenic from nickel sulphide ores was not a primary concern in the Manitoba Division until 1989. At that time increased production in the Thompson Open Pit mine, which contains high arsenic ore zones, resulted in excess amounts of arsenic in the Thompson Refinery affecting electro-nickel quality. This problem was resolved through extensive efforts by Mill personnel. The purpose of this paper is to familiarize the reader with- the Thompson Mill.- the mineralogy of the Thompson orebody.- the evolution of Ni/As separation in the Mill.- the metallurgical impacts of the separation on the Mill.- the importance of the separation to the Manitoba Division."

Jan 1, 1991

By H. J. McQueen

Aluminum was hot worked at 400 - 500°C and strain rates (e ) of 0.004 -0.1s-1, under reversing strains (c) of 0.5 to 0.2 or 0.5 to 0 and also advancing from 0.5 to 1 or 0.5 to 5. Under similar test conditions for different parts of the strain paths, the average measured flow stresses are found to agree with each other. In the forward and backward strain path tests, the almost identical steady state plateaus affirm the occurrence of dynamic recovery (DRV). On reversal of strain direction at constant e , there was generally negligible Bauschinger effect. In specimens annealed at 400°C, static recrystallisation (SRX) was followed microstructurally. mainly by disappearance of elongated grains with serrated boundaries because the new grains were only little a finer than the old due to low strain energy. The only influence of reversing strain path observed was the effect of change of grain boundary area as grains elongated or returned towards equiaxed. In optical microscopy, elongated grains with serrations and deformation bands confirmed DRV in forward path specimens. In reverse path specimens, equiaxed grains were gradually restored with retention of serrations and bands. In low magnification polarized optical microscopy, grain alignment increased with strain for forward path specimens; whereas it decreased in reverse path ones, supporting DRV. Orientation imaging microscopy (OIM/SEM) revealed that elongated grains are broken up as deformation bands rotate during the forward path and that grains return to equiaxed appearance on backward straining. Comparative studies using optical microscopy in polarized light (POM), OIM/SEM and transmission electron microscopy (TEM) revealed that while subgrains remain equiaxed and constant in size and character during the forward and backward paths, the fraction of low angle facets decreased while that of high angle grain facets increased with increasing strain; these are coupled with a fairly low fraction of medium angle boundaries. The results contribute to the understanding that dynamic recovery in aluminum maintains sub-boundaries with low misorientation but as grains elongate and more subgrain become adjacent to grain boundaries the fraction of high angle boundaries rises (with backward straining it was vice versa).

Jan 1, 2007

By R. Hendricks

"IT IS a pleasure for me to appear before yon today and to have this opportunity of reviewing with you recent developments in the world lead and zinc industry. To provide essential background material, I propose reviewing the period from 1950 to the present, a period which has undoubtedly been the most hectic in the long history of the industry.In capsule form, the pattern for this period is one of repeating cycles of boom and recession, of failure through research to develop adequately new markets and new uses for lead and zinc, of surplus production and growing inventories, of price instability, and lastly, of an abdication in some sections of the industry of responsibility for control of its own destiny by turning to governments for support in time of stress. This is not a pretty picture but, as the 1950 decade ends, there are signs of a new maturity and of a growing determination on the part of the industry to put its own house in order.The difficulty suffered by the world's lead and zinc industry in the current decade originated with the support extended to it in 1950 by the U.S. Government at the time of the Korean conflict. Recalling the shortage of base metals in World War II and fearing that the Korean conflict might develop into World War III, the U.S. Government in 1950 adopted a policy to encourage the production of lead and zinc, both domestically and abroad by means of development loans and long-term floor priced purclu.se contracts."

Jan 1, 1960

Roasting of molybdenite concentrate is an important stage in the production of commercial molybdenum trioxide. The oxidation kinetic and mechanism of molybdenum sulfide concentrates from two plants were investigated at temperatures from 444 °C to 640°C. The rate of reaction was determined for thin layer samples in a muffle furnace at controlled temperatures, oxygen excess and removal of sulfur dioxide. For both concentrates the rate of reaction is fairly slow at temperatures below 500°C and remains fairly constant from 540 to 600 °C. It was observed that the concentrate from the first plant presents a tendency for sintering or glazing at temperatures above 620°C, whereas the same phenomena was observed at 20 or 30 °C higher temperature for the second concentrate. A kinetic model of two reactions, involving the formation of Mo02 as intermediate oxide for the production of Mo03 is proposed and activation energies of 23.0 and 20.8 kJ/mol for the first and second reaction were calculated for temperatures between 520 °C to 600 °C. These low values of activation energies indicate that the overall rate of oxidation is controlled by mass transfer, particularly in a porous layer of oxides. Therefore, the renewal of the surface by mixing and motion of the concentrate layer is of great importance. Sublimation of Mo03 becomes significant for temperatures above 650 °C.

Jan 1, 2007

By P. Leo

Al-Mg-Si alloys are widely used as medium-strength structural materials; extrusion is the most common processing route. In the present hot deformation investigation of a 6060 alloy, the microstructure of the alloy has been analyzed in the as-cast state, after homogenization heat treatment and after hot deformation by tensile tests in the range 400-490°C and 10-4 to 10-2s-1 on both as cast and homogenized alloys. After deformation the microstructure of the as-cast alloy exhibited cavitation. The flow curves at the lowest test temperature T show a gradual softening after a stress peak, being more evident for the alloy deformed in the homogenized state in association with a high yield stress; at higher T a plateau is attained which is lower as T rises and strain rates decrease. For each fixed T, the ductility decreases as strain rate increases for the homogenized alloy whereas, for the as cast alloy, it rises with strain rate. Constitutive analysis gives Q = 240kJ1mol for the homogenized alloy in agreement with published values; this indicates a more rapid strength decline with rising T than Al, suitable for good hot workability along with the lack of cavitation.

Jan 1, 2011

By Robert B. Parsons

"Several recent cases indicate that the Courts may be leaning toward a more favourable treatment of mine closing and related costs. In this article, we look at two recent cases, Burnco Industries Ltd. and Nomad Sand & Gravel Ltd. The former was heard before the Federal Court - Trial Division and the latter before the Tax Review Board.It appears that in certain situations mining companies may now be able to sustain current deductibility of estimated mine closing costs during the productive years of the mine, rather than waiting until either the date on which mining ceases or the reclamation and similar activities commence. This would be of great benefit to the mining industry, as waiting until the bitter end often means that there are no revenues available against which the expenses may be offset and, hence, no tax relief.IntroductionUnder the Income Tax Act in Canada, taxpayers are not permitted any deductions in respect of an outlay or expense in determining income from a business or property, except to the extent that such expenditures are made or incurred by the taxpayer for the purpose of gaining or producing income. In addition, no deductions are permitted for amounts transferred or credited to a reserve, contingent account or sinking fund except as expressly permitted by the Act.In large measure, these provisions are relevant to the mining industry to the extent that they determine the periods during which expenses may be charged against revenues for income tax purposes. Several recent cases have indicated that the Courts are leaning toward a more favourable treatment of accrued costs in the mining industry than was previously considered to be the case."

Jan 1, 1982

By V. G. c Papangelakis, M. Huang

A conductivity cell, developed previously, was employed in an effort to investigate the inter-relation between electrical conductivity and acidity of sulphuric acid - metal sulphate solutions at high temperatures. The measured solutions include the H2SO4-H2O, MgSO4-H2O, H2SO4-MgSO4-H2O, H2SO4-MgSO4-Al2(SO4)3-H2O solutions. All solutions reported in this paper were measured from 15 to 250 °C at equilibrium vapour pressure. The maximum measured concentrations of H2SO4, MgSO4 and Al2(SO4)3 were 0.45 m, 0.30 m and 0.10 m, respectively. It was found that, from 15 to 250°C, there is a linear relationship between H2SO4 concentration and electrical conductivities for acid concentration up to 0.45 m. At 250 °C and constant H2SO4 concentration, the solution conductivity drops with the increase of MgSO4 concentration. Lt is suggested that this drop is caused by a decrease in the concentration of H. Finally, an empirical model was developed based on the available measurements. This model has been tested against real laterite leach solutions where sulphuric acid and metal sulphates are dominant electrolytes. The average difference between the estimate acid concentration from this model and the one from titration was less than 5%.

Jan 1, 2004

By D. Larouche, M. Mardan

Hot tearing is a complex defect in aluminium castings which is produced during solidification when a certain amount of liquid phase remains and weakens tensile resistance of the alloy. In direct chill casting of aluminium alloys, hot tears initiate at the surface of sheet ingots just after the primary cooling zone, where the microstructure is particularly vulnerable. In order to study the hot tearing susceptibility of these alloys, and the effect of grain refiners on their thermo-mechanical behavior , tensile tests were carried out in the semi-solid state ( ~95% solid) and at low strain rates using an apparatus called DCSS, for Direct Chill Surface Simulator. This apparatus, originally developed at Alcan Arvida R&D Centre (ARDC), is an instrumented rig test reproducing the conditions prevailing during the primary cooling stage of the DC casting process. The mechanical behavior of solidifying shells and the hot tear formation under applied tensile loads were measured and the occurrence of hot tearing was observed. Temperature in different locations of the casting, applied load and surface strain were monitored during the tensile tests conducted on aluminum alloys AA5182, AA6111 and AA3104. The microstructure of the tested samples was examined using the optical microscope to evaluate their columnar or equiaxed aspect and their effect on the mechanical response of the alloy. A special emphasis has been given to the evaluation of fractions solid existing in the castings at the start of the tensile tests, taking into account the local temperature, thermal gradient and cooling rates experienced. It was found that excessive grain refiner additions decreased the strength of solidifying shells because of the increased level of porosity induced by easier nucleation of new phases (gas included). It was also observed that cooling rates increased with the level of grain refiner, a phenomenon that was associated to the higher number of contact points obtained with small equiaxed grains. Finally, the concept of a stress based criterion for hot tearing was reinforced by the strengths obtained on not grain refined AA5182 and AA6111 showing similar fraction solid near the surface, but significantly different grain sizes.

Jan 1, 2006

By T. C. Holmes

"Dome mine, in the Porcupine mining camp of northern Ontario, is one of the important gold mines of Canada, its production of gold from the commencement in 1910 to the end of 1946 having a value of $149,000,000.GENERAL GEOLOGYThe oldest rocks in the mine are greenstones of Keewatin age(l). Those to the south are known as the southern greenstones, but little is known of their structure. Those in the northwest part of Fig. 1 and the north part of Fig. 2 are known as the northern greenstones or greenstone 'nose'. They face north, dip steeply north, and end to the east against an unconformity which pitches northeast about 20°. The volcanics are overlain unconformably by Timiskaming .conglomerate and slate. All these rocks are cut by porphyry. Closely associated with the porphyry is a group of rocks that have suffered extreme alteration. Diabase dykes intrude all the other rocks and the ore. The principal massive rocks in the mine are two adjacent flows known asthe andesite (south) and dacite (Fig. 1). They are composed chiefly ofmassive, medium-grained lava. Pillows, flow lines, and other typically volcanicfeatures are found along the tops of both flows and at other places in theandesite. These parts nearly everywhere show a slight schistosity panllelwith the flows except in the orebodies, where they are massive."

Jan 1, 1954

By P. O. Parfitt

At the McIntyre mine, there are two distinct operations: a gold mine with narrow veins, mined by cut-and-fill methods, and a copper mine with large, open, long-hole stopes. The application of the Critical Path Method to scheduling work in the copper mine, where it has been used successfully for several years, is de-scribed briefly. This application is relatively simple. Use of C.P.M. has now been extended to the gold mine. To replace the former method of scheduling from bar-charts, a procedure was developed for scheduling automatically. To handle an operation of this size and complexity, a computer was essential. Improved schedules are now being produced, with a saving in time.

Jan 1, 1967

By A. A. Nourbakhsha

The main application of refractories based on andalusite in ferrous metallurgy are in air heaters of blast furnaces, mobile mixers, and hot-metal transfer, pig iron ladle, steel-casting, and intermediate ladles. Three specific properties of andalusite are very interesting for the production of high-quality shaped and unshaped mullite refractories: being free of water, its crystal a remains stable without changing its density or volume after firing and therefore has no internal porosity .Graphite additives due to its great wetting ability play an important role in raising the property of refractory bodies. In order to improve properties of andalusite graphite bodies, oxidant agent for increasing in hot strength and oxidation resistance can not be avoided. In this research, firstly 8 pig iron ladles from ESC(esfahan Steel company) with different conditions selected and monitored during usage to determine of main factors affecting on corrosion of refractories. Results showed that tap to tap time, undischarged pig iron ,penetrated pig iron are the main ones.Literature studies showed that the graphite addition help to thermal shock resistance and liquid penetration(steel,pig iron) effect. In this research particle size distribution of aggregates containing andalusite and graphite determined by andreazen equation. Then different mixes with different percentage of graphite,Si, FeSi, SiC prepared by uniaxially pressing under 1500kgf/cm2 pressure by adding 4%wt novalak resin and 0.4%wt HMTA as hardner. Samples fired at 1100-1500oC under reduction atmosphere. According to specific standards density, porosity and CCS measured. Analytical tests such as XRD, SEM were carried out on sample selected from point of view of mechanical properties at different temperatures. Results showed that optimized amount of Si and Fe-Si for _-SiC formation in body is 4 and 6 %wt respectively at 1500OC. XRD and SEM analysis on sample with Fe-Si additives showed no destructive phase through the matrix, also SiC additives not only increase oxidation resistance but also no effect on thermo-mechanical properties.

Oct 1, 2011

By L. Henry Smith, David C. Arthur

"The Williams Mine is Canada’s largest gold producer, with annual production of 450 000ounces from 2 300 000 tonnes of ore. Highly mechanized and automated underground mining practices are employed in order to achieve and maintain high levels of productivity and minimize costs.The mine ventilation system is modified to include a new vent raise and variable pitchvane-axial fan. This addition allows several fan installations underground to be decommissioned. A substantial net savings in installed horse power is achieved.Heating costs associated with under-ground ventilation air are a significant portion of mine operating costs. Air heating costs are substantially reduced by recovering heat from upcast exhaust air, minewater and compressor cooling circuits. This waste heat is used to supplement propane fired air heating systems for underground ventilation air. An additional benefit is the availability of a heat sink for summer cooling of the compressors.System design, energy savings data and payback calculations are presented."

Jan 1, 1996

By E. Ghali, W. Zhang, M. Robichaud, G. Houlachi

"The performances of six mesh and one plate dimensionally stable anodes have been investigated in the zinc electrolyte at 38oC and compared to conventional silver-lead alloy anodes. The electrochemical behaviour of these anodes was studied by cyclic voltammetry, galvanostatic, potentiodynamic, open circuit potential and electrochemical noise measurements. It was observed that at the end of 24 h of galvanostatic polarization at a current density of 50 mA/cm2 in the zinc electrolyte at 38oC, the mesh V had the lowest potential followed by mesh III, mesh VI, plate-V, mesh IV, mesh I, and mesh II electrode. When the potentials for mesh I, mesh III, mesh IV, VI and plate-V, mesh V were compared with that of the Pb-0.7%Ag anode (1920 mV/SHE), they were found to be 6%, 16%, 7% 10%, 17% lower, respectively.After 16 h decay following the 24 h polarization, the mesh III had the lowest corrosion rate (51 mS/cm2) among the seven specimens, followed by the plate-V, mesh V, VI, IV, I and II (221 mS/cm2). For the fresh surface as received, after two hour open circuit potential measurements, mesh I had the most positive (noble) potential (1382 mV/SHE) among the seven electrodes followed by the plate-V electrode, mesh V, mesh IV, mesh VI, mesh III and mesh II (751 mV/SHE). After consecutive series of electrochemical testing, mesh V, mesh III, mesh VI had lower corrosion rates (~ 343± 6 µA/cm2) than that of mesh IV, mesh I, plate-V, and mesh II (~ 644± 143 µA/cm2).INTRODUCTIONThe continued use of lead based anodes in the electrowinning process has been mainly due to their relatively low cost as compared to other materials (Msindo, Sibanda, & Potgieter, 2010). They have good electrical conductivity, stability during electrolysis, very good corrosion and wear resistance (Ivanov, Stefanov, Noncheva, Petrova, Dobrev, Mirkova, Vermeersch, & Damaerel, 2010). However, lead-based anodes give their high energy consumption and low corrosion resistance for electrowinning. To overcome these problems, Dimensionally Stable Anodes (DSAs) has been chosen (Msindo et al., 2010). Comparing to the traditional lead anodes, the DSA anodes have many advantages: (1) no contamination; (2) no loss of anode material, pure electrolyte; (3) lower gas bubble effect through special anode designs; (4) use of higher current densities (Msindo et al., 2010). The success of DSA anodes has been attributed to their chemical stability that allows them to maintain nearly constant dimensions during the life of the anode even when operating in environment with low pH values. Due to their stability, the consumption rates of DSA are as low as 1 mg/amp.y (Alfantazi & Moskalyk, 2003)."

Jan 1, 2016

By J. C. Moreno, G. Rios, M. Palacios

The Huelva smelter was commissioned in 1970 coinciding with the shutdown of the old smelter in the Rio Tinto mine site. That new smelter consisted of two Momoda blast furnaces with a capacity of 500 dmtpd of concentrate. Nevertheless, soon after their start-up, it was clear that an increase in the smelting capacity was needed. After an analysis of the existing alternatives at that time, the flash smelting technology was chosen. The new Outokumpu Flash Smelting Furnace (FSF) came into operation on 18 September1975, with an initial capacity of 900 dmtpd of concentrate, using four Venturi-type burners and preheated atmospheric air. Since that date the Huelva Smelter team, together with Outokumpu (now called Outotec), have continuously improved our FSF design, process conditions and operational practices, leading to a present capacity of 3,500 dmtpd of concentrate. Since 1975, five smelting campaigns have been completed, the last ending in November 2013 with the rebuilding of the original FSF hearth. This paper describes the history of these improvements and the lessons learned.

Jan 1, 2014

By J. Bednar, R. R. Rogers, W. Dingley

"Zinc is by far the most important metal used for protecting steel from the ravages of corrosion, and cadmium is also used extensively for this purpose. These metals are applied by electrodeposition in cyanide baths when a particularly good appearance and high throwing power are required. One great disadvantage in using these baths has been the decrease in cyanide concentration and the increase in carbonate concentration that takes place during the plating. Another disadvantage has been the development of serious embrittlement in high-strength steels. The present authors have developed new cyanide baths for electroplating both zinc and cadmium on steel. These baths are stable in composition during plating, they have not produced appreciable embrittlement in the high-strength steels that have been investigated up to the present time, and they permit the use of considerably higher plating current densities. In addition, they produce extremely fine grained coatings that are attractive and have excellent adherence and covering properties. Brighteners can be used in the plating baths if bright finishes are required."

Jan 1, 1967

By J. B. Boniwell

The INPUT electromagnetic prospecting system was originally developed by Dr. A. R. Barringer in an effort to increase the sensitivity and penetration of airborne EM methods. Although brought to an operational state some several years ago, it is only through relatively re-cent modifications and testing that some of the potential of the system has been fully realised. This is brought into perspective by some recent results over known ore deposits and geologic environments.

Jan 1, 1967

By Charles Kingsley

THE PRESIDENT (DR. C. B. KINGSTON, member C.l.M.M.) expressed regret that neither of the authors of the paper was able to be present to submit the paper in person. In their absence, it would be introduced formally from the Chair. It was a clear, straightforward account of a fine piece of shaft sinking, cleverly conceived and boldly executed. He referred briefly to the distribution and nature of the Dome ore-bodies and stated that, for both the miner and the metallurgist, the mine had provided a wide range of problems of unusual interest. Discussion on the paper was then invited. MR. THOMAS PRYOR said the paper was most opportune, because the subject of internal shafts did not appear to be fully treated in current mining literature. Many members were not familiar with Canadian gold deposits and it would be of interest if the authors could give a brief description of the location of the ere deposits of the Dome mine. This information would doubtless explain why a new internal shaft was needed in a position which required such an exceptionally long cross-cut to connect it to the main hoisting shaft to surface. It would also add to the value of the paper if the authors would give some idea of the duty expected of the new shaft in terms of tons of rock hoisted and of trips engaged in the transport of men and materials, and it would be helpful if figures could be given of the total capital cost of the hoists and subsidiary excavations at the shaft top, and of the cost per foot for sinking and lining the shaft below the collar. Turning to details of the paper, one was favourably impressed by the care given to the provision of a good travelling way for men in the main cross-cut, as shown in Figure 1. It was by no means always that one could walk in comfort and safety in a working where there was a 20-in. ventilating pipe in the roof.

Jan 1, 1939

By Zhenyu Han, Dion Weatherley, Ruslan Puscasu

"This study aims to demonstrate the capacity of the Discrete Element Method (DEM) to model and simulate fracture in brittle rock, capture the crack propagation process and determine crack propagation rates for various levels of external loading. In the numerical experiments reported here, a macroscopically homogeneous body of brittle rock, containing a single pre-existing crack, was subjected to tensile stress loading. Simulations concerned with model I crack growth process in 3D were carried out. The process of fracture has been observed under various steady state and dynamic conditions. The numerical results obtained reproduce qualitatively and quantitatively a variety of observed fracture phenomena. Specifically, this study examined the onset of cracks, single dominant cracks that grow across the specimen, crack bifurcations and branching. The density of fractures that can be nucleated and grow to a significant size with and without arresting each other, crack growth speed and stress distribution, all have been consistently and systematically analyzed. Suggestions on potential future developments are made and discussed.INTRODUCTIONFracture and failure mechanics are very important in mining, manufacturing, materials processing, mineral processing, civil and mechanical engineering, and many other disciplines of science and engineering. Yet, due to the complexity of fracture phenomena, no theoretical models of broad applicability are currently available (Bieniawski 1967). The simulation of crack propagation is therefore considered an open question in numerical rock mechanics. Although, a significant body of experimental research on fracture of materials was carried out since the early days of fracture mechanics (circa 1940s) (Poncelet 1946, Mott 1948), often in parallel with the development of fracture mechanics theories as well as with the development of experimental and observational techniques themselves, the experimental results were often done on particular classes of material such as glasses and other very brittle materials. Indeed, a number of specific experimental observations on the behavior of growing cracks in brittle materials were made in the 1940s for which generally accepted explanations based on physical principles are still lacking. Likewise, quantitative numerical modeling, based on both continuum and discrete methods, as a basis for understanding dynamic crack growth is still in a preliminary stage."

Jan 1, 2015

By John L. Bonus

"WITHIN THE BROAD PARAMETERS implied by the title of my speech, I propose to deal more particularly this evening with a subject the many aspects of which have constituted the essential elements of one of the main thrusts undertaken by the MAC in the past two years, i.e., to create among Canadians a much greater awareness of the importance of mining and to demonstrate to them what are the many and varied benefits they derive from mining activities across their country. In other words, MINING - WHAT IT MEANS TO CANADA.I also intend to discuss some aspects of government-industry relationships.I am very conscious of the fact that I am speaking to an audience made u in large part of experts in several fields of mining and exploration activities. They will be familiar with many of the points I intend to discuss. However, without in any way suggesting that familiarity breeds contempt, might I emphasize that even in this particular forum there is justification for reiterating some of our basic philosophies and suggesting ways whereby they might be better understood and promoted.Let us first summarize the present dimensions of the Canadian mining industry."

Jan 1, 1971