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By H. J. McQueen

The irregular history of Mg wrought products is briefly described. The temperature and strain rate dependence of microstructural evolution, flow stress and ductility of Mg alloys in hot working, are described. The flow curves rose rapidly to a peak stress which was lower as temperature T rose and strain rate e declined and above 300°C the curves extended into plateaus until failure. Clearly grains not oriented for slip undergo mechanical twinning in the initial stages (a 0.15) at all temperatures. Basal slip proceeds in suitable grains and in the twins. The stress concentrations at grain and twin boundaries lead to slip on non-basal systems and to the formation of subgrains with greater dynamic recovery (DRV) at higher T or lower e. With increasing strain, misorientation builds up resulting in dynamic recrystallization (DRX) first at twin intersections and later at grain boundaries which have become quite serrated. Even after extensive straining at high temperatures, the new grains are found mainly along the boundaries of the original grains, leaving their centers with only basal slip except when nucleation at twins leads to completion of DRX throughout a grain. Despite similar shear modulus and melting point to Al, hot mechanical forming behavior of Mg alloys differ due to differences in crystal slip systems, twinning, and second phases. Moreover, the influences on forming of alloy additions (solutes, segregation in casting, dispersoids, precipitation) and impurities are not as well catalogued as for Al. Despite the benefits from dynamic recrystallization, varied grain orientation effects, heterogeneous substructures and the resulting stress concentrations result in considerably lower ductility for Mg alloys at the same stress level as for Al materials. Application of these theories to extrusion, rolling and forging and the effects on product properties are surveyed.

Jan 1, 2006

By Bruce V. Kiefer

A modernization project was undertaken by Kroman Celik Sanayii A.S. in order to improve their product quality, consistency and shape of the coil package, reduce maintenance and delays in rod mill, thereby increasing utilization and productivity. The project involved installation of a new Morgan Intelligent Pinch Roll and High Speed Laying Head, modifications to the existing controlled cooling conveyor, plus replacing the coil reforming station. The new pinch roll and laying head were to provide better control of the ring formation and consistency of the coil on the conveyor, while reducing delays on the conveyor. Changes to the controlled cooling conveyor included installation of new nozzle decks and Optimesh air distribution system along with re-arrangement of existing fans in order to improve both cooling rates and uniformity of cooling. This paper explains details and features of the newly-installed equipment technology. Resulting product and process improvements are presented, including increased tensile strength and uniformity, reduction in delays on the conveyor and reform tub, plus improvements in coil quality.

Oct 30, 2017

By S. Prasad

The effectiveness of ultrasonic velocity measurements and attenuation of the propagating pulse was evaluated as a means of Non-Destructive characterization of cold worked and annealed copper. Commercial copper is subjected to mechanical working such as forging, rolling and thermal treatment to induce re-crystallization. The microstructural changes that occur in copper and a variation in its mechanical properties are subjected to analysis using the ultrasonic technique. The signal processing is carried out using the wavelet analysis technique. The features of wavelet analysis namely, localization in space and the presence of an infinite set of basis functions allows removing noise from the time series and components of a non-stationary signal to be analyzed. This is seen to improve the accuracy of the results obtained from the ultrasonic technique in the case of copper, which has distinct coarse grains that are difficult to inspect due to backscattering from the grain boundaries.

Jan 1, 2010

By J. P. De Carvalho, R. Dimitrakopoulos

An actor-critic reinforcement learning approach is presented to improve the production of an industrial mining complex by defining shovel allocation and adapting the short-term plan given grade-control decisions. Blasthole data updates the simulated orebody models, which are input into a stochastic grade-control method based on a spatially constrained clustering approach that minimizes the profit-loss function. These aspects are embedded in a discrete-event simulator that defines the material flow from faces to processors. A case study at a copper mining complex shows the methods’ ability to adapt to new information, improving the quality of the material feed and increasing cash flow by 23% compared to a baseline case.

Jun 25, 2023

By Alim Ullah

The paper discusses the necessity of upgrading low-iron containing ores, giving as an example, NML-Tata Steel Project in the Quebec-Labrador region of Canada. As cooling of pellets is generally a bottle-neck in most pelletizing plants, examples are given of the methods used to improve cooling in the existing plants and a simple, low-cost alternative, tested on a pot-grate system, is presented. The procedure described is applicable to sinter plants also. The trends in iron and steel production worldwide are then given, as well as the reasons for the increase in steel production by the Electric Arc Furnace (EAF) route. The stoichiometric and thermodynamic requirements for producing iron, irrespective of the process, are explained. The different ironmaking processes, especially the Direct Reduction (DR) ones are briefly discussed, outlining recent improvements made to some of them. The pros and cons of producing cooled DRI and Hot-Briquetted Iron (HBI) are given with predictions made for their future growth. An alternative to cold-briquetting of DRI fines is also discussed. Highlights of an ironmaking processes which is at the laboratory/pilot plant stage are given.

Aug 1, 2018

By René Winand

A new process was studied at large laboratory scale at Université Libre de Bruxelles, under contract with Metallurgie Hoboken-Overpelt. A two cathodes (1m long ; 0.2 m high) channel cell was used at 2000 A/m2, with an electrolyte flow rate up to 1.8 m/sec. The main results may be summarized as follows : cathodes are electro¬refined grade in analysis ; metallographic structure and surface roughness are kept under control up to 1.3 cm (one side deposits) ; silver in cathode is controlled by CI and Br ions in solution ; organics must be used at very low concentrations (in the range of 0.1 mg/1, with a consumption of about 0.01 mg/lh).

Jan 1, 1987

By William J. Miles

The inhalation of dust has been a problem in the mining industry since antiquity. Crystalline silica is now known to be the cause of silicosis, a form of pneumoconiosis that is associated with excessive exposure to respirable particles in some mining and industrial environments. Crystalline silica was reviewed by the International Agency for Research on Cancer (IARC) in 1986 and classified as a Group 2A, Probably Carcinogenic to Humans in Volume 42 and Supplement 7 of the IARC Monographs (1987). In 1996, IARC reviewed additional literature and studies published in the intervening decade and recommended that quartz and cristobalite, two polymorphs of crystalline silica, be listed as Group 1, Carcinogenic to Humans. Their recommendations and reclassification were published in 1997 in IARC Monographs 68.[2] In both Monographs, IARC classified amorphous silicas as Group 3, Inadequate Evidence for Carcinogenicity to Humans.

Jan 1, 1998

By Aiyuan Ma, Kun Yang, Weiheng Chen, Jinhui Peng, Shiwei Li, Feng Xie, Libo Zhang

In this thesis, a new process of recovering zinc sulfide ores was developed. The novel synthetic coordination leaching process mainly included two steps: microwave assisted phase reconstruction and compound coordination leaching. By applying various techniques, such as chemical composition analysis, X-ray diffractometry (XRD) and Raman spectroscopy, it could be concluded that sulfide phases would directly oxidized to zinc oxides under the 500 ºC microwave roasting and adding 30% Na2O2. What’s more, zinc leaching rate reached to 61.16% within 2 hours. Compared to the current technologies, this procedure had the advantage of avoiding SO2 emission, high leaching efficiency, simple process, manipulate easily, and low cost, which could be expected tremendous application potentials.

Jan 1, 2016

By Jr. Langhans, J. S. McPartland

"The presence of zinc in cyanide solutions is generally thought to not have an adverse effect on precious metal recovery or recovery rate by heap leach processing. However, analytical interferences of zinc in solution can cause problems in accurately determining and controlling cyanide concentration in the leach solution, leading to increased cyanide consumption. Analytical methods and the chemistry of cyanide in the presence of zinc are reviewed. The effects of solution pH and zinc concentration on the free cyanide determination were evaluated in detail. Use of the standard silver nitrate titration and a modified titration method for controlling cyanide concentration during heap leaching were investigated experimentally. The practical implications of cyanide heap leaching in the presence of cyanide soluble zinc minerals are discussed.IntroductionThe presence of zinc in precious metal cyanidation circuits is not uncommon. Zinc can be introduced into cyanide leach solutions through dissolution of various zinc minerals1>, or through the use of a Merrill Crowe (zinc precipitation) circuit. Zinc minerals typically occur infrequently and in low concentration in gold ores, but are more abundant in silver ores. Merrill Crowe systems are most commonly employed for recovery of precious metals from solution for relatively high silver ores. It is desirable to control the amount of dissolved zinc in a cyanidation circuit for several reasons. Excessive zinc build-up in cyanide leach solution can, under certain circumstances, inhibit precious metal dissolution and adversely affect solution recovery systems. Additionally, high zinc concentrations can lead to excessive in-process cyanide inventories and potentially, to higher cyanide consumption"

Jan 1, 1999

By W. P. Barnett

In 1988, the U.S. Department of Energy's Pittsburgh Energy Technology Center identified three coal cleaning options for achieving flexible environmental control strategies aimed at reducing energy-related SO2 emissions. These are selective agglomeration, advanced froth flotation, and advanced cycloning. Each technology relies on maximum liberation of pyrite and other mineral matter through feed coal comminution to fine and ultrafine sizes. Research projects designed to expeditiously develop each of these technologies to the point of commercial viability were initiated. This paper will present the status of these projects and the application potential of each technology to coal beneficiation.

Jan 1, 1992

Bortech’s BoreClad corrosion protection system will be displayed at MINExpo. BoreClad is an innovative system for inside diameter cladding of nozzles, tubes and other circumferential devices. Pressure vessels, mud pumps and other mining equipment must be protected from corrosive caustic chemicals. Usually manufactured from mild steel, they can be clad with a protective material, such as stainless steel, to provide corrosion resistance. However, most welding processes leave voids where corrosion can damage the base metal. BoreClad provides void-free welds by combining gas metal arc welding with automated feed and rotation of chuckable parts. Workpieces of up to 915-mm- (36-in.-) long with a 460-mm- (18-in.-)swing can be clad with stainless steel, Iconel or other exotic metals. In addition to eliminating the voids associated with hand welds, BoreCladcan lay more than 2.2 kg/h (5 lbs/hour) of metal. That is a significant reduction in weld time. Web sitewww.bortech.com.

Jan 1, 2004

By O Jones

Longstanding occupational health challenges of the underground hard-rock mining sector require both an analysis of historical data to assess evidence of linkages between the source of the problem and subsequent illnesses, as well as investigating the means by which health risks to workers can be eliminated or minimised. This paper refers briefly to a recently established National Health and Medical Research Council (NHMRC) sponsored Epidemiological Study into the incidence of Lung Cancer, contracted by mineworkers in Western Australia (WA) due to the inhalation of diesel exhaust fumes from 1996 to 2012. Thereafter it reviews current knowledge of the nature of the challenges facing those responsible for the health and wellbeing of underground hard-rock miners in WA, commencing with the recent categorisation of diesel exhaust as ‘Carcinogenic to Humans, Group 1’, by the World Health Organisation’s (WHO) International Agency for Research on Cancer (IARC). An attempt is also made to explore how the challenge has changed with the adoption of more advanced engine technologies, including the increased generation of ultra-fine volatile organic and other nucleates, submicron carbonaceous agglomerates and toxic gases.The compounding effect of using the mine decline access entry as both the primary ventilation intake and haulage-way is also discussed, as is the need to develop a more appropriate metric for regulating diesel engine emissions. Finally the paper refers to ongoing in-mine research pursued by the National Institute for Occupational Safety and Health (NIOSH) at its Diesel Laboratory in an underground limestone mine near Morgantown in the USA.CITATION:Jones, O, 2015. Diesel exhaust and the underground miner in Western Australia, in Proceedings The Australian Mine Ventilation Conference, pp 167–172 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

A comprehensive review of ore pass records, from ten Quebec underground mines, indicated some of the limitations of available design tools to predict the occurrence of ore pass interlocking hang-ups in metal mines. The Distinct Element Method was used to perform a series of numerical experiments in order to investigate the influence of ore pass geometry, rock fragments shape and size distribution on material flow in an ore pass. Guidelines have been developed to help limit the occurrence of interlocking hang-ups in an ore pass. The proposed guidelines were evaluated with respect to field observations. Ein kompletter Bericht der Erzrollezeichnungen, von 10 Quebec unterirdischen Gruben, hat einige der Beschränkungen der vorhandenen Designwerkzeuge angezeigt, um das Auftreten Erzrolle der blockierenhang-ups in den Metallgruben genau vorauszusagen. Eine Reihe numerische Experimente mit der eindeutigen Element-Methode, wurden aufgenommen, um den Einfluss von Erzrollegeometrie, Partikelform nachzuforschen und Felsenkorngrößenverteilungen auf Materialfluss in ein Erz überschreiten. Dieses hat zu die Entwicklung der Richtlinien geführt deren Implementierung das Auftreten der blockierenhang-ups in eine Erzrolle begrenzen sollte. Die vorgeschlagenen Richtlinien wurden in Bezug auf Labor- und Feldbeobachtungen ausgewertet. Une revue de la performance actuelle des cheminées à minerai dans 10 mines souterraines du Québec a indiqué les limites des outils de conception servant à dimensionner les cheminées pour minimiser le nombre d’accrochages par enchevêtrement rocheux. Des séries de modélisations numériques, utilisant la méthode des éléments distincts, ont été réalisées afin d’évaluer l’influence de la géométrie des cheminées, de la forme des fragments rocheux et de la distribution granulométrique sur l’écoulement du matériel dans les cheminées. Cet exercice a permis de développer des lignes directrices pour le dimensionnement des cheminées afin de limiter l’occurrence d’accrochage par enchevêtrement rocheux. Les lignes directrices proposées ont été évaluées en fonction des observations effectuées sur le terrain.

Jan 1, 2003

By B. D. Thompson

Many mines adopt necessarily conservative backfilling strategies due to a lack of understanding of their backfill behaviour. In the past five years, extensive instrumentation campaigns have focused on measuring in-situ cemented paste backfill behaviour. These tests have resulted in optimised backfilling efficiency through elimination or reduction of cure periods where; i) controls on backfill behaviour are understood, and ii) barricade pressures are demonstrated to be within a safe range using routine monitoring as a required QA/QC procedure. Recently, this work has been extended to consider hydraulic backfill operations. Two stopes have been instrumented at Vale?s Coleman and Garson Ramp mines. The instrumentation and deployment methods are discussed, and representative total earth pressure, pore pressure, and temperature data are presented. In one case, pressures in the stope are relatively low as drainage causes strength gain in the fill and so pressures are arched. In a second example, again, drainage causes strength gain in the fill, but increasing temperatures correlate with pressure increases even during downtimes in filling. These pressure increases are thought to be caused by thermal expansion of the backfill in confined locations. Generally, the instrumentation approach has proven successful in measuring hydraulic backfill behaviour and offers good potential for incorporation into a procedure to safely maximise backfilling efficiency through routine barricade pressure monitoring, when combined with safeguards to ensure adequate fill drainage.

Aug 1, 2013

By Michael G. Pojar, Peter G. Chamberlain

Solution mining, primarily by heap leaching, has emerged as an important method for mining gold and silver in the United States. Heap leaching offers many economic and environmental advantages over conventional production techniques, in particular for lean ores and old mine waste rock. In order to more effectively pursue research on heap, dump, and in situ solution mining of gold and silver, the Federal Bureau of Mines conducted an extensive survey of leaching practices and problems. This presentation summarizes trends and statistics. Leaching is projected to provide 20 pct of primary mine produced gold and 10 pct of primary silver by the end of 1982. Current leaching practices in the United States are reviewed; operational problems and research programs to alleviate those problems are discussed.

Jan 1, 1981

By S. E. Phillipson

During the course of evaluations by the Mine Safety and Health Administration’s Roof Control Division, the controls on ground instability were investigated at surface and underground limestone mines throughout the eastern and southern United States. Structural geologic features, including joints and faults, were identified by basic geologic mapping as primary controls on highwall and back instability in surface and underground limestone mines. By comparing the spatial orientation of discontinuities and internal angle of friction with the orientation of highwalls on a stereonet, the potential for sliding, toppling, and raveling failures was evaluated in a semi-quantitative fashion. Structural geologic mapping identified faults and joints, which dismembered the back and were associated with ground instability, in underground mines. This paper documents the importance of recognizing structural geologic controls on ground stability in limestone mines, advocates basic geologic mapping as a critical component of ground control programs at surface and underground limestone mines, and provides examples of simple stability evaluations using the stereonet method.

Jan 1, 2006

By Zwaan J, Kepa J

Ok Tedi mine has become one of the major copper producers in the world. In the process of becoming of age, it overcame the challenges of operating in a locality which is young in geological terms, experiences very high rainfall and has a topography which gives rise to frequent landslides. This paper discusses some of the geological, mine and geotechnical engin- eering aspects of the Mt Fubilan ore deposit.

Jan 1, 1991

By Ernie Doell, Trung Nguyen

"In early 1995 Cluff Mining commissioned a newly constructed high density tailings thickener at its Cluff Lake uranium mill. The 85 ft diameter high density thickener is one of the first of its kind in North America, and incorporates the novel paste technology in its design to produce densified (in the range of 60 -65% solids) mill tailings suitable for stable deposition in the tailings management area. This paper discusses the impetus behind the installation of such an unconventional thickener, and the many trying experiences in making it operational.IntroductionCluff Mining, a wholly owned subsidiary of Cogema Resources Inc., is the operator of a uranium mine and mill complex at Cluff Lake which is located in northern Saskatchewan. Since 1980, the company has developed and mined out several different ore bodies within the Cluff Lake region for the production of uranium concentrates, commonly known as yellow cake. Based on the known ore reserves, the Cluff Lake operations are projected to last till the early 2000's.Tailings from the Cluff Lake mill have been discharged to a tailings management area consisting of a tailings pond and two facilities for primary and secondary treatment systems. The tailings pond has an impervious bentonite lined dam, and it is divided into a solids and a liquids holding areas. Until the beginning of 1995, the mill tailings were discharged in two separate lines to the solids pond; one line carried the slurry residue of 45-50% solids (w/w) from the CCD circuit, and the other discharged raffinate tails containing less than 1 % (w/w) gypsum precipitate. Supernatant in the solids pond is treated in the primary treatment system prior to discharging to the liquids pond. Figure 1 shows the site plan of Cluff Lake tailings management area.It has been estimated that by the end of 1995 the solids pond would be filled to about 60% of its design capacity, and probably would be full before the year 2000. Therefore, Cluff Mining had to consider a more efficient tailings disposal method that could extend the service life of the existing Cluff Lake tailings management area. A high density tailings thickener was believed to be the most practical and economical system for tailings disposal at Cluff Lake mine."

Jan 1, 1996

By W W. Moorhouse

A survey of recent literature indicates that sulphides occur in the volcanic rocks of the Archean, or in sedimentary rocks intercalated with the volcanic rocks. The thick sedimentary sections are generally poor in sulphides. Thus, the widespread pyrite and pyrrhotite mineralization in the Archean may be largely of volcanic origin. Introduction I N this paper, commercial base-metal deposits will not be considered, as they are dealt with in other papers of the Symposium. Instead, attention will be focused on those sulphides, often associated with graphitic argillites or tuffs, which have appeared in such embarrassing abundance in electromagnetic surveys of Archean areas. The data on which the paper is based are drawn from recent reports of the Ontario Department of Mines, the Quebec Department of Natural Resources and the Geological Survey of Canada. The information available from these sources is unfortunately limited, because sulphides commonly occur in sheared rocks, such as black argillites and tuffs, which rarely form conspicuous outcrops, and may not be exposed at all. Thus, in the absence of geophysical information, even detailed mapping may fail to reveal the presence of sulphide-rich rocks.

Jan 1, 1965

The use of comparative sampling methods during the evaluation of the tin-copper deposits at Cleveland mine yielded closely checking average results from groove, channel, AXT split diamond drill core, and bulk sampling for both tin and copper content of the ore.The weighted mean tin and copper grades and values for the groove, channel, and split core samples showed small percentage differences from bulk sample results, and the F-ratio test for single population origin of the four types of samples was accepted at the 99· 5 per cent level of confidence.These results indicate that grade estimates based on the assays from AXT split diamond drill core and/or groove samples would be reliable within practical limits.

Jan 1, 1968