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This symposium, being held at The President Hotel, Johannesburg on 9th-11th September, 1969, is being jointly sponsored by The South African Institute of Mining and Metallurgy, The South African Corrosion Council and the Southern Africa Stainless Steel Development Association, and supported by the C.S.I.R. The three days of technical sessions, at which 350 delegates are expected, will include introductory films on the properties and uses of stainless steels, papers on corrosion problems and prevention, design and economics, welding and applications in industries of particular importance to South Africa. The programme includes four overseas guest speakers who are acknowledged leaders in their respective fields. Detailed programmes together with application forms for registration will be published shortly. Enquiries to P.G. Box 8954, Johannesburg.

By M. B. Algeo

Discussion of the above paper M. B. ALGEO The management and staff of Buffelsfontein Gold Mining Company Limited are to be congratulated on the excellent performances described in the paper presented by Mr Christos. In this day and age, with the current economic and labour situation, the mining industry is being constantly pressed to increase the productivity of ever-diminishing quanta of resources. Stress in rock The ISRM Symposium, 1976 is to be held in Sydney from 9th to 13th August, 1976. It is being organized by The Australian Geo. mechanics Society as a regional symposium of the International Society for Rock Mechanics. Thermal analysis The First European Symposium on Thermal Analysis will be held at the University of Salford on 20th to 24th September, 1976.

Jan 12, 1975

By B. Litt, D. L. Van Coller

Job evaluation and the changing wage pattern by D. L. VAN COLLER, B.A.(Cape Town), M.A., B.Litt.{Oxon.) (Visitor) This paper sets out to show how changing forces are affecting the techniques that have been used in the evaluation of Black jobs on gold mines in the Anglo American Group since the introduction of job evaluation in 1961. Initially, job evaluation was essentially a management tool designed to differentiate jobs in a limited skill spectrum and thereby permit the establishment of a 'many stepped' job ladder for Black employees to climb. With the changing wage pattern, job evaluation is becoming an industrialrelations tool aimed at recognizing the skill and effort contributed by the worker so that the pay relationships between jobs are seen to be equitable by the employees.

Jan 8, 1974

By M. Timucin

Phase relations within the condensed Cu-Cu2S-PbS-Pb region of the Cu-Pb-S ternary were investigated. The boundaries of the ternary liquid-miscibility gap were redrawn, and the directions of the tie-lines were established by the quenching of samples equilibrated in evacuated and sealed silica capsules at 1473 K. The activities of lead in sulphur-saturated Cu-Pb alloys along the boundary of the miscibility gap were measured by the dew-point technique at 1473 K. From the tie-line distributions, measured lead activities, known activities of the Cu2S-PbS join, and the ternary Gibbs-Duhem integration, consistent sets of activities for lead and copper and partial pressures of sulphur were obtained along the ternary miscibility gap at 1473 K.

Jan 1, 1989

By P. R. Levey, A. van Bennekom

The effects of nitrogen alloying on the corrosion properties of austenitic stainless steels were investigated by a combination of potentio-dynamic and surface analysis techniques. The results indicate that nitrogen undergoes the phenomenon of anodic segregation, affecting both general and localized corrosion resistance. Nitrogen alloying is found to be beneficial to general corrosion resistance in a de-aerated sulphuric acid solution, but to be detrimental in an aerated solution of sulphuric acid This phenomenon is explained in terms of an ammonium-ion polarization effect. Localized corrosion resistance is found to improve dramatically as a result of nitrogen alloying, the nitrogen improving the formation, maintenance, and stability of the passive film in environments that promote pitting various theories that have been proposed to account for these phenomena are discussed.

Jan 1, 1995

By N. A. Barcza

Pointing out that South Africa needs to utilize its wealth-creating activities, together with local and international investment, to further develop its industries, the address asserts that the mining and minerals industries, especially in the manufacture of beneficiated products, offer the greatest potential for South Africa to achieve its goal. As many mineral-beneficiation processes are based on pyrometallurgical routes, the address goes on to describe some historical - pyrometallurgical operations and to indicate probable developments in the future. These include growth in the fields of both precious and base metals. After discussing environmental and recycling matters, together with manpower requirements, the address concludes that the major growth in the mining and minerals industries will occur in the manufacture of steel, stainless steel, ferro-alloys (particularly ferrochromium), aluminium, and titania slag.

Jan 1, 1996

By R. L. Paul

Although it is often said that South Africa does not have suitable deposits, or the potential to develop mines on a small scale, a recent survey by the Chamber of Mines1 showed that, out of a sample of 641 producers, 41 per cent had between 10 and 19 employees, and a further 29 per cent had between 20 and 29 employees. This goes to show that minerals-related small, medium, and micro-enterprises (SMMEs) do exist, and can play an important role in the development of rural industries in South Africa. Nchaka Moloi of the Department for Mineral and Energy Affairs defined the various categories of SMMEsas shown in Table I2. An enterprise could be placed in a certain category as long as two of the variables, employees, capex or production applied.

Jan 1, 1997

By C. L. Workmann Davies

Underground transport and communication in collieries was the theme selected for the 1983 mining school conducted by The South African Institute of Mining and Metallurgy. The response from the industry was so good that three separate schools of one week each were arranged, and a total of 222 delegates attended. Development of Mineral Resources The Institution of Mining and Metallurgy and The Department of Mineral Resources, Government of Thailand, with the cooperation of the Thai Mining Association and Chulalongkorn University, is to hold an international conference entitled 'Role of Government in Mineral Resources Development' in Bangkok from 5th to 8th Decembc -:" 1983. Electronics in Mining A symposium entitled 'Electronics in Mining', organized by The South African Institute of ElectriealEngineers, is to be held in Randburg, South Africa, from 18th to 20th September, 1984.

Jan 1, 1983

By D. R. Arnold

Discussion of the above paper by D. R. ARNOLDt This paper is the result of an excellent piece of work performed as a service to hyUrometallurgy in general and to the South African uranium industry in particular, and the authors are to be congratulated, Authors' reply Dr Arnold is correct in saying that the present Senbrix resins, which are based on the experimental heavy resins first developed at the National Institute for Metallurgy (NIM), need not necessarily show the same poor performance with respect to cobalt poisoning as the NIM prototypes. Oceanology International The next 01 World Conference is to be held Brighton, England, from 2nd to 7th March, 1980. The programme will concern technical advances in the offshore oil and gas industries, and is expected to include 140 papers from 20 countries.

Jan 1, 1979

By C. H. Wyndham, N. B. Strydom, S. Benade

A group of 23 underweight men weighing less than 50 kg were subjected to an acclimatization procedure in which the work rate was gradually increased from 35Watts on the first day to 70Watts on the eighth day. Excessively high body temperatures and heart rates were observed on these subjects throughout the acclimatization period and on their performance they must be rated as heat-intolerant. It can be concluded that such underweight men should not be subjected to acclimatization at such high work rates and that they should not be allocated to tasks involving these rates in a hot environment. The fact that their body surface areas are inadequate to enable them to get rid of the internal heat produced during strenuous work plus their low work capacities are the major reasons for their inability to tolerate heat.

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 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 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

By use of a finite-difference model of an experimental galvanic cell, the effect of a resistance in the metalic conduction path on the potential and current distributions in the cell was predicted. The model predictions were compared with experimental measurements of potential profiles (measured by use of a scanning reference electrode) and galvanic currents. The predictions agreed well with the experimental measurements. Apart from this model, which is applicable in macroscopic cells (Le. with an electrolyte of low conductivity), a calculation procedure was developed to predict the effect of an external resistance on the galvanic current in a microscopic cell (high conductivity). The responses of the galvanic currents in the microscopic and macroscopic cells to changes in the external resistance were compared. From the similarity of the responses, a simple practical procedure for the evaluation of the external resistance (meter resistance) that can be tolerated is proposed.

Jan 1, 1989

The Institute has concluded an agreement with the Chamber of Mines whereby the Chamber Librarian maintains a section in the Library for the Institute. Surface effects of underground mining South Africa is blessed with vast mineral resources. It is essential to exploit those reserves if the country is to remain economically viable. Surface-mining equipment The Goldfields Mining Expo '86 is to be held in Kalgoorlie, Western Australia, from 30th October to 1st November, 1986, in conjunction with the Annual Conference of the Western Australian School of Mines. Mintek reports Report M142D Characteristics of gold and pyrite flotation at the Chemwes plant. (1st issued May 1984.) Report M159D Beneficiation tests on andalusite ore from the Marico district. (1st issued Aug. 1984.) Report M164D The recovery of tungsten from South African low-grade schee/ite concentrates. (1st issued Sep. 1984.)

Jan 1, 1986

By Y. Hwang, C Kang

To understand the effect of thermal loading from HLW on the groundwater flow nearby, the coupling of TH in an equivalent porous medium is studied. Results indicate that under given conditions the alteration of groundwater flow by decay heat is localized phenomena. More comprehensive studies are underway for THM coupling. Zum Verstandnis fur die Wirkung der thermischen Belastung von HLW in der Nahe von Grundwasserstrom, ist die Verbindung von TH in den entsprechenden porigen Medium erarbeitet. Die Ergebnisse zeigen, dass unter vorgegebenen Bedingungen die Anderung von Grundwasserstrom durch Zerfallwarme lokalisiert wird. Zusatzliche umfassende Arbeiten sind fur die THM Kupplung auf dem Wege. Pour comprendre l'effet du chargement thermique de HLW sur l'écoulement d'eaux souterraines tout près, l'accouplement du TH dans un milieu poreux équivalent est étudié. Les résultats indiquent que dans des conditions données le changement d'écoulement d'eaux souterraines par la chaleur d'affaiblissement est des phénomènes localisés. Des études plus complètes sont en cours pour l'accouplement de THM.

Jan 1, 2003

By M. J. Gouws, T. P. Knoetze

The spontaneous combustion of coal and the explosion of coal dust are two phenomena that were identified by the South African mining industry as requiring investigation. Research contracts were awarded to the G.P. Badenhorst Research Facility of the CSIR and the Department of Mining Engineering of the university of the Witwatersrand by the now defunct National Energy Council. Both projects entailed tests on numerous coal samples in specially designed apparatus. Since the completion of the project, attempts have been made to predict experimental results without incurring the cost of performing experiments. This paper describes predictive indices, based on routine laboratory tests, that were developed by the different research teams for their particular projects. A comparison of the results obtained by applying the spontaneous combustion liability index and the explosibility index to common coal samples indicates that, in general, propensity to spontaneous combustion and explosibility exhibit an inverse relationship. A brief overview is given of some major South African coal-mine disasters.

Jan 1, 1995

By J. R. de Wet

The behaviour of mild steel in aqueous cyanide solutions similar to caustic cyanide elution solutions was investigated at high temperature in electrochemical experiments. The anodic polarization diagrams of mild steel indicated that steel may undergo active dissolution under these conditions. The rare occurrence of gold plating in practice is the result of the limiting of the anodic dissolution of the steel by the presence of a passive layer on the steel. This passive layer is stable only in a certain potential range, and the free corrosion potential attained determines whether the steel will be passive or active. For conditions typical of elution columns, several corrosion potentials are possible, depending primarily on the initial condition of the steel and the concentration of oxygen in the solution. If these conditions result in the formation of a passive layer on the steel, changes in concentration and temperature will not necessarily result in plating since the layer may exist in a metastable form.

Jan 1, 1993