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By K. M. Banks

Multiple-pass hot-strip-rolling schedules of carbon steels and niobium-microalloyed ferrite-pearlite steels were simulated on a Gleeble 1500 thermomechanical test apparatus. The effects of finishing temperature, coiling temperature, and chemical composition on the as-deformed ferrite grain size and hardness of the steels were determined. Low finishing temperatures and low coiling temperatures both contributed to ferrite grain refinement. Good agreement was found for the microstructure and hardness of the steels between the as-ruled condition and the results obtained from rolling simulations. The progress of recrystalization and precipitation was followed from examinations of the flow-stress curves during the hot-rolling simulations. The flow-stress behaviour during the finishing passes was consistent with the resulting changes in final ferrite grain size. It was found that the no-recrystalization temperature, TNR, is raised by increased additions of niobium.

Jan 1, 1993

Past work on the ignition of methane-air mixtures by coal-cutting picks is reviewed, with special reference to the factors that contribute to ignitions and ways of reducing them. The main conclusions obtained from this review are outlined for the following aspects: mechanisms of ignition, methane concentrations, and the roles of rock types, cutting parameters, cutting tools, and water. However, many of these factors have been investigated on a qualitative, rather than on a quantitative, basis. A considerable amount of effort over a long period has been expended in this area of research. It is shown that a number of the factors influencing ignitions by machine picks have been researched adequately, but that there is still work to be done. Research is continuing in this area, being concentrated primarily upon the ignition potential of the coal-cutting pick.

Jan 1, 1985

By J. le Grange, M. Tullmin, A. Strauss, F. P. A. Robinson, C. A. O. Henning

An experimental feritic stainless steel with a chromium content of 40 per cent was welded by laser and electron beam (EB) welding processes. These techniques were found to be particularly suited to the welding of this alloy in that the impact toughness of the weld metal and heat-affected zone (HAZ) of the laser welds compared favourably with those of the parent aloy. When the EB process was used, the impact toughness of the weld metal was over 180 J/cm2. Grain growth in the HAZ was minimal for welding with these two processes. Corosion tests, conducted in a solution consisting of 20 per cent sulphuric acid and 100 p.p.m. of potassium thiocyanate, and In a highly corrosive industrial solution, indicated that the laser and EB welds were free of sensitization effects, thus confirming the metalographic results.

Jan 1, 1989

By S. Nana, M. B. Cortie

Duplex stainless steels containing high levels of manganese and copper and lower-than-normal levels of nickel were produced and evaluated. The experimental alloys containing 3 per cent copper by mass could not be successfully hot-rolled. Alloys containing less than 2 per cent copper could be hot- and cold-rolled without difficulty. The wrought experimental alloys that contained copper were found to offer some advantages over the 2205- type duplex stainless steel in sulphuric acid at 52°C. Resistance to pitting attack was governed primarily by the chromium, molybdenum, and nitrogen contents, and one of the experimental alloys was superior to the 2205-type alloy in the ferric chloride test. It is concluded that manganese is a useful substitute for nickel in duplex alloys, but that further work is required before the present alloys, or variations of them, could be commercially viable.

Jan 1, 1993

By B. Z. Weiss, N. R. Comins, F. Blum

Some aspects of the mechanical behaviour of chromium-containing dual-phase 3CR12 steel were investigated as a function of the temperature and strain rate. The yield stress was found to depend on both the temperature and the strain rate, with no substantial differences between the longitudinal and the transverse directions. The strain-rate sensitivity decreased with increasing temperature. The yield stress could be presented as a function of a temperature-strain-rate parameter. Impact test results showed substantial differences between the energy absorption of the transverse and longitudinal specimens above the ductile-brittle transition temperature. Changes in energy absorption with temperature were gradual for specimens in both orientations, and the transition from ductile to brittle behaviour occurred between 373 and 173 K. Strain rates ahead of the tip of notches with different geometries were calculated and measured experimentally.

Jan 1, 1990

By J van Rooyen, S. Archer, M. Fox

The use of dilute sulphur dioxide (SO2) gas mixtures for the oxidation/precipitation of manganese has been explored widely in recent years. The technical merit of the concept is well proven and implementation of the technology on commercial scale is imminent. This paper reviews the technology of manganese removal by means of dilute SO2 gas mixtures and highlights some of the challenges associated with its implementation on industrial scale. A brief review of the technology is presented; the review considers both the mechanism and chemistry of manganese oxidation/precipitation with dilute SO2 gas mixtures. The impact of variables such as temperature, pH and SO2 concentrations on the manganese removal process is assessed. Challenges associated with implementation of the technology on industrial scale are discussed. Gas dispersion is highlighted as a critical design consideration.

Jan 1, 2007

By L. Cortez, Á. Magalhães, F. Durão

Methods based on regionalized variables theory, commonly known as geostatistics, have been widely used since more than three decades to predict/estimate spatial distributed data, namely mineral resources, with quite good results. However, some restrictive theoretical assumptions, such as the need of some kind of stationarity of data and the linearity of the predictor/estimator, are often wrong options in many applications. An alternative approach based on a finite mixture modelling, or cluster weighted modelling (CWM) technique, is presented and compared, in its theoretical and practical aspects, with the geostatistical methodology. CWM is a general non-linear framework based on the estimation of joint density functions allowing the calculation of the conditional probability function of the target values given their locations. Validation tests are performed in a 2D case study, where testing data proceeds from a soil contaminated by a heavy metal. The results of ordinary kriging and CWM estimations show a very good agreement with actual data. Keywords: Non-linear regression, Geostatistics, Ordinary kriging, Finite mixture modelling, Cluster weighted modelling.

Jan 1, 2003

By André Fouché

GFWW Bulk Sample Prep Plant INDEX ?Features ?Flow Diagram ?Pictures of Plant

Jan 1, 2005

The 114th Annual General Meeting of The Southern African Institute of Mining and Metallurgy was held at The Country Club, Johannesburg, Napier Road, Auckland Park on Thursday, 11 August 2011. Welcome The President extended a special welcome to the guests and representatives of our sister institutes and other associations, and also to recipients of awards, senior members of industry, Honorary Life Fellows, past-presidents, our members and other guests, among them the following: F. Cawood, President, Institute of Mine Surveyors of South Africa C. Roode, President, Mine Metallurgical Managers' Association of South Africa M. Cresswell, Chairman, South African Coal Processing Society A. Hay, Immediate Past President, South African Institute of Electrical Engineers L. Gardner, President, South African National Institute of Rock Engineers J. Krynauw, President, The Geological Society of South Africa (GSSA)

Jan 1, 2011

By N. C. Gay

The quantitative evaluation of the performance of fill materials placed in gold mine stopes is achieved by (i) measurement of the in-situ load- displacement, or stress-strain, characteristics of the materials; (ii) an objective comparison between the observed fill performance and that predicted from suitable computer modelling techniques; and (iii) objectively comparing conditions in backfilled and conventional stopes. Considerable problems have been experienced with the development of sufficiently robust instrumentation which can be installed within filled pad- docks and give reliable information over a long period of time. However, at most mines where backfill performance is being monitored, it has been possible to correlate stress measurements within the filled paddocks with strain measurements adjacent to the paddocks. The resultant stress-strain curves agree relatively well with those determined in the laboratory. Measurements in the hangingwall strata of filled and unfilled stopes indicate that the placement of fill does reduce the amount of inelastic convergence due to bed separation. Moreover, in some stopes, the rate of convergence with respect to face advance does reduce to that of the theoretical elastic convergence. Quantification of changes in the conditions at the stope face due to placement of fill has proved difficult. Observations indicate that, provided the fill is placed close to the face (- 5 m), and adequate temporary face support is used, conditions in filled panels are superior. In addition, in filled panels the damage caused by a rockburst in the stope and, particularly, in gullies is generally much less than would be expected in an unfilled stope. To quantify these improvements, parameters such as stope height, face advance and the frequency of falls of ground are being monitored.

Jan 1, 1988

By W. Lin, H. Endo, M. Kwasniewski, A. Kamei, M. Takahashi

Uniaxial tension tests were conducted on specimens of eleven granitic rocks which came from eastern Japan, and included a granite, four granodiorites, four tonalites and two gabbros. The axial and transversal deformability of these rocks was determined based on strain measurements using wire strain gauges. The experimental test results revealed that deformational properties of the rocks investigated varied depending on their petrographic features. However, the axial strain and the lateral strain characteristics showed a similar trend for all the rocks, i.e. the stress-strain curves were non-linear throughout the whole stress range from the initial point of loading to the point of ultimate failure. Moreover, the tangent Young's modulus and the ratio of the lateral strain to the axial strain decreased monotonously with the increasing of the axial stress. Still, the deformational properties were different for individual rocks in a quantitative sense. In particular, the difference in the lateral strains among different rocks was more distinct than that in the axial strains. For example, the Poisson's ratio at a stress level equal to 50% of the ultimate strength of a granodiorite was very low, close to zero. Furthermore, the Poisson's ratio of a tonalite was lower than that of a granodiorite, and assumed a negative value. This effect occurred because the lateral strain became positive as it changed from contraction at the initial stage of loading to extension at higher stress levels. There is no ready explanation for this phenomenon; it is believed, however, that it occurs due to microcracks pre-existing in rock materials and/or weak bonds between the adjacent mineral grains. Les essais de traction directe ont été conduits sur les échantillons de onze roches granitiques provenant de la région Est du Japon: un granit, quatre granodiorites, quatre tonalites et deux gabbros. Déformabilité axiale et transversale de ces roches s’était déterminée en utilisant des jauges extensométriques à fil. Les résultats obtenus à partir des essais montrent que la déformabilité des roches examinées varie selon leurs propriétés pétrographiques. Cependant, à partir des essais, une tendance semblable était observée dans les paramètres de la déformation axiale et la déformation latérale de toutes les roches; c'est-à-dire chaque courbe de contrainte-déformation était non-linéaire dans tout l'intervalle de contraintes à partir de l’état initial jusqu’à l’état d’une rupture finale au cours du chargement. De plus, le module tangent de Young et le rapport de la déformation latérale sur la déformation axiale a diminué de manière monotone avec l'augmentation de la contrainte axiale. Cependant, les différences quantitatives de propriétés de déformation sous traction étaient observées entre des roches individuelles. Particulièrement, la différence de déformations latérales était plus notable que celle-là de déformations axiales entre des roches différentes. Par exemple, le coéfficient de Poisson à un niveau de contrainte égal à 50 % de la résistance d'un granodiorite était très bas, près du zéro. En outre, le coéfficient de Poisson de la tonalite était inférieur que celui du granodiorite et a assumé une valeur négative. Cet effet est apporté parce que la déformation latérale est devenue positive en passant de la contraction dans l'étape de chargement initiale à l'extension sous les contraines plus hautes. Il n'y a aucune explication prête de ce phénomène; on prétend, cependant, qu'il est induit par des microfissures préexistantes dans des matériaux rocheux et/ou des joints faibles entre les grains minéraux adjacents. Einaxiale Zugversuche wurden auf Probestuecke von elf frischen, in Ostjapan vorkommenden, granitartigen Gesteinen durchgefuehrt, welche einen Granit, vier Granodiorite, vier Tonalite und zwei Gabbros umfassten. Die axiale und transversale Verformbarkeit von diesen Gesteinen wurde durch Verformungsmessungen mit Drahtdehnungsmessstreifen geklaert. Die experimentellen Versuchsergebnisse offenbarten, dass Verformbarkeitseigenschaften des untersuchten Gesteins in Abhaengigkeit von ihren petrographischen Eigenschaften variierten. Jedoch zeigten die axialen und die lateralen Spannungsdehnungslinien eine aehnliche Tendenz bei allen Gesteinen, d.h. die Verformungskurven waren nicht linear im ganzen Bereich vom Ausgangspunkt des Belastens bis zum Punkt des entgueltigen Bruchs. Ausserdem verringerten sich das tangentiale Elastizitaetsmodul und das Verhaeltnis der lateralen Verformung zur axialen Verformung monoton mit der Erhoehung der axialen Spannung. Dennoch waren die Verformbarkeitseigenschaften der einzelnen Gesteine in der quantitativen Wahrnehmung unterschiedlich. Insbesondere war der Unterschied bezueglich der lateralen Verformungen zwischen verschiedenen Gesteinen eindeutiger, als der in den axialen Verformungen. Z.B. war die Querkontraktionszahl auf einem Spannungsniveau, das 50% der Zugfestigkeit eines Granodiorits entspricht, sehr niedrig und nah an Null. Ausserdem war die Querkontraktionszahl eines Tonalits negativ und deshalb niedriger als die eines Granodiorits. Dieser Effekt trat auf, weil die laterale Verformung, als sie sich von der Kontraktion am Ausgangsstadium des Belastens bis hin zur Ausdehnung auf den hoeheren Spannungsniveaus aenderte, positiv wurde. Es gibt keine fertige Erklaerung fuer dieses Phaenomen; es wird jedoch angenommen, dass es wegen der Mikrorisse auftritt, die vorher im Gesteinsmaterial und/oder in den schwachen Bindungen zwischen den angrenzenden Mineralkoernern existieren.

Jan 1, 2003

By E. J. McLean

Gold mineralisation at Bendigo is exclusively associated with quartz reefs, commonly found within or near anticlinal fold hinges. The gold is typically coarse grained (0.5 mm to 5 mm), free milling and displays a complex, nuggetty distribution within the veins. This ore is highly amenable to gravity recovery processes. As the Bendigo operation is not permitted to treat whole ore by a cyanide leach/CIL circuit, the flow sheet is more complex than conventional gold recovery circuits. Primary gold recovery is from a gravity circuit closing the grinding circuit to a bulk gravity concentrate and from a flotation circuit treating cyclone overflow to a bulk float concentrate. The plant capacity is relatively low by current gold industry standards at 600 000 tpa. Re-establishing gold production at Bendigo has presented several challenging, and sometimes competing, issues in process design and operation. The mine, process plant, associated services and infrastructure are at Kangaroo Flat, a low density, semi-rural zone in the southern urbanisation of the Bendigo metropolitan area. One of the main processing challenges during the design was the competing comminution requirement to avoid over-grinding, which would flatten or smear the characteristic nugget gold and hinder effective gravity gold recovery, whilst also providing sufficiently well liberated particles that would respond well to flotation. Important, non-metallurgical challenges were to minimise impacts on the local community from noise, dust, air emissions, visual impact, water egress and off-site traffic.

Jan 1, 2007

By N. B. Devi

The extraction of Cu(II) from HCl media using Cyanex 923 in kerosene was investigated. The effect of shaking time, aqueous phase acid concentration, extractant concentration, chloride ion concentration, various metal ions (Mn2+, Mg2+, Fe2+, and Ni2+), and temperature on the extraction were studied. Using 0.1 M Cyanex 923 the extraction of Cu(II) was 6.7 per cent from 3 M HCl, which increased up to 78.5 per cent with 6.5 M HCl and then decreased due to acid extraction by the extractant. The maximum extraction (97.5 per cent) was obtained with 1 M Cyanex 923 from 5 M HCl solution. A mathematical model has been developed to describe solvent extraction equllibria over wide ranges of concentration of extractant, acid, and chloride ions. The composition of the extracted species has been predicted on the basis of slope analysis results and extraction equilibrium modelling. The negative values of enthalpy change and entropy change confirm the exothermic formation of the extracted complex.

Jan 1, 2012

By T. Wallmach

Heavy mineral deposits are a source of the economic important element titanium, which is contained in minerals such as ilmenite, pseudorutile and rutile. In the Ranobe heavy minerals deposit these minerals occur not only as primary unaltered minerals but also display various degrees of alteration resulting in an increased titanium content of the deposit. The presence of the various FeTi-oxide minerals? textural relations is a reflection of geological processes and may ultimately be used to unravel the geological history of the deposit. These minerals have different chemical and physical properties that influence metallurgical tests and the quality of products produced from various mineral beneficiation streams. It is therefore of metallurgical importance that the minerals are well characterized, defined and monitored during preliminary beneficiation tests.

Jan 1, 2007

By S. Kok, D. Delport, J. Calitz

Altering the microstructure in order to improve the tensile properties of bow shackles resulted in inconsistency in the fatigue performance. This raises the question whether the inconsistency in fatigue life can be attributed to microstructural changes along the profile of the shackle or to decarburization at the surface. Bow shackles forged from 080M40 (EN8) material were subjected to different heat treatments in order to alter the microstructure. The shackles were subjected to five different fatigue load cases, which represented typical loads experienced at termination points for an overhead power line with a span length of 400 m, with changes in conductor type, configuration, wind, and ice loading. Although the change in microstructure does improve both the tensile and fatigue performance, we found that the depth of the decarburization layer has a greater effect on the high cycle fatigue life of bow shackles than the non-homogeneous microstructure.

Oct 1, 2021

As part of a broad program to optimise the performance of their grinding circuit, BHP Billiton Cannington have installed an OCS© Expert system together with three VisioRockTM online particle size analysis cameras. The main purpose of the system is to stabilise grind size and feed to the flotation circuit. This particular application of OCS© is the first installation to incorporate Metso Minerals Process Technology-Asia Pacific's (MMPT AP) Dynamic SAG/AG Mill Model, which is able to predict numerous mill parameters that were previously unable to be measured with the existing plant instrumentation. Integrated into the logic of the control algorithm are online vision based, particle size measurements of the AG mill feed and recycle crusher product. This paper will describe the history of the project from initiation to date, the model and OCS© logic configuration, and demonstrate the significant benefits realised at Cannington mine.

Jan 1, 2007

By C. A. Garzonio, A. M. G. Affuso

The paper describes the analyses and the tests carried out on representative slabs of white Carrara marble which have highlighted the correlation between the micro fabrics and physical and mechanical parameters. The aim is to determine the conditions which indicate the triggering and evolution of the deformation phenomena. La note écrit l’analyse et les epreuves effectuée sur un echantillon représentatif de nombreuses dalles en marbrede Carrara. Les études montrent la correlation entre la minéralogie et les paramètres physiques et mecaniques. Le but est déterminer les conditions qui indiquent l’amorçage et l’evolutions des phénomènes de déformation. Diese Arbeit gibt eine Beschreibung der experimentalen Untersuchungen und der Analysen über die Marmorplatten von Carrara. Daraus resultiert, dass die Charakterisierung der Mineralogie und die Porosität der Gesteinsmaterialien die physikalische mechanische Degradation beurteilen und die Krümmungen bestimmen.

Jan 1, 2003

By H. M. Wells

The investment decision under uncertainty by H. M. WELLS, Pr. Eng., M.Se. (Fellow) The future outcome of a proposed investment is uncertain at the time the decision must be made to accept it or reject it. This uncertainty can be expressed in the form of a probability distribution. An attempt is made to rationalize the investment decision under these circumstances, especially when the range of possible outcomes extends into both the acceptable and unacceptable domains. A rigorous definition of risk is proposed, and a criterion of risk aversion is developed that forms the boundary between acceptable risk and unacceptable risk (called the loss limitation line). It is shown that this decision criterion can also serve as a quantitative yardstick in the evaluation of various possibilities for 'tailoring' the proposal to mlke it more compatible with the particular financial circumstances of the company concerned.

Jan 4, 1976

The 8th Annual University of Cape Town (UCT)/ University of Stelenbosch (US) Minerals Processing Symposium was held at the Van Riebeeck Hotel in Gordon's Bay on 3rd August, 1990, under the auspices of the Western Cape Branch of The South African Institute of Mining and Metallurgy. The primary object of this meeting was to give research students at UCT and US the opportunity to present their work to a critical audience from industry, and to obtain feedback regarding the research needs of the minerals industry. Although the emphasis of these symposia is on work in progress at US and UCT, they also create an excellent opportunity for informal discussion between academics and metallurgists in industry. The first symposium in this series was held in 1982 at US, while the symposium in 1989 was replaced by the International Colloquium on Developments in Froth Flotation, also held in Gordon's Bay.

Jan 1, 1990

By R. H. Steel

Ingot casting and wire drawing In Iron Age Southern Africa by R. H. STEEL (Visitor) This paper describes the experiments that were conducted in 1974/1975 on two related aspects of Iron Age copper technology in Southern Africa: ingot casting and wire drawing. Three types of ingot were successfully cast: the St Andrew's Cross ingot, the marale ingot, and the musuku. It is suggested that the 'studs' on the musuku are not the remains of broken-off rods as previously proposed by other investigators, but that the ridged pattern is an ornamental feature. Copper wire was successfully drawn with similar tools and according to the procedures described in the literature on African Iron Age wire drawing. It is concluded that these accounts are generally accurate and that the pre-European metal workers are worthy of respect for the results they achieved with primitive methods.

Jan 11, 1975