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By M. J. Santofimia

Multiphase microstructures in steel have been intensively studied in the past years, but combining non-equilibrium phases still offers a great potential for further development of these steel grades. Thus, improved combinations of mechanical properties can be obtained with microstructures formed by bainite or martensite, in combination with retained austenite. In particular, microstructures on the basis of carbon-depleted martensite and retained austenite can be produced by the very promising production process named quenching and partitioning (Q&P). Originally, the Q&P process aimed to avoid the formation of bainite during the heat treatment. However, the process does provide the possibility for (carbide-free) bainite formation during the partitioning step, i.e. in the presence of martensite. This article evaluates this approach, considering thatthe formation of bainite from austenite is strongly influenced by the preceding formation of martensite. Although the accelerating effect of the presence of martensite during bainite formation has been observed, it is not yet fully understood, and experimental and theoretical studies are being performed in order to come to a more effective exploitation of these processes for the formation of multiphase microstructures.

Jan 1, 2013

Many industries base their decisions on the assaying of tiny analytical sub-samples. The problem is that most of the time several sampling and sub-sampling stages are required before the laboratory provides its ultimate assays using advanced chemical and physical methods of analysis. As long as each sampling and sub-sampling stage is the object of due diligence using the Theory of Sampling it is likely that the integrity of the sought after information has not been altered and the generated database is still capable to fulfil its informative mission. Unfortunately, more often than not, unawareness of the basic properties of heterogeneous materials combined with the unawareness of stringent requirements listed in the theory of sampling, lead to the conclusion that massive discrepancies may be observed between the expensive outcome of a long chain of sampling and analytical custody, and reality. There are no areas that are more vulnerable to such misfortune than sampling and assaying for trace amounts of constituents of interest in the environment, in high purity materials, in precious metals exploration, food chain, chemicals and pharmaceutical products. Without the preventive suggestions of the theory of sampling serious difficulties may arise when making Gaussian approximations or even log-normal manipulations in the subsequent interpretations. A complementary understanding of Poisson processes injected in the theory of sampling may greatly help the practitioner understand structural sampling problems and prevent unfortunate mistakes from being repeated over and over until a crisis is reached. This paper presents an overview of the theoretical, practical and economic difficulties often vastly underestimated in the search for quantifying trace amounts of valuable or unwelcome components.

Jan 1, 2009

By P. Kohler, T. D. Sampson, T. H. Tunley

The Metsep Process for the separation and recovery of zinc, iron, and hydrochloric acid from spent pickle liquors by T. H. TUNLEY, B.Sc. (Ch em. Eng.) (Visitor), P. KOHLER (Visitor), and T. D. SAMPSON, Pr. Eng., B.Sc. (Chem. Eng.), B.Econ. (Visitor) A spray roaster has been installed in the Johannesburg area for the treatment of spent liquors from a variety of small pickling operations. A new process was developed for the processing of the liquor that is contaminated with zinc chloride, and a commercial plant was built incorporating this process. An ionexchange plant separates the zinc from the iron chloride, and a liquid-liquid-extraction plant converts the zinc chloride to zinc sulphate and recovers the hydrochloric acid.

Jan 5, 1976

By C. Chapman, M. G. Reading, M. P. Amsden

Computer control of flotation at the Ecstall concentrator By M. P. AMSDEN, C. CHAPMAN, and M. G. READING Ecstall Mining Limited, a subsidiary of Texas Gulf Sulphur Company, operates the Kidd Creek Mine, a 10000 tons per day base metal producer, near Timmins, Ontario. Two different types of ore are mined and milled: copper-zinc and silver-lead-zinc. At the highly automated Ecstall concentrator the ores are processed by selective flotation in three individual circuits. One of the most important metallurgical tools for process control is a sample system incorporating continuous on-stream X-ray analysis. Recently this system was automated further by the addition of computer control of reagents for two copper-zinc flotation circuits. The computer programs, utilizing optimum seeking methods and smelter contract terms, have increased copper recovery by 1,1 per cent, zinc recovery by 1,4 per cent, and have reduced reagent costs by 16 per cent. Although not expected, copper and zinc concentrate grades were improved slightly as well.

By A. J. S. Benade, A. J. A. Heyns, N. B. Strydom

The maximum oxygen intakes of samples of about 30 Bantu, weighing less than 50 kg from different tribal groups (Zulu, Xhosa, Sotho and Shangaan) were measured on a treadmill. The mean maximum oxygen intake of the 164 men was 2,12 litresjmin and only 18 men (11 per cent of the sample) had maximum oxygen intakes of 2,5 litres/min or above (the minimum requirement for such tasks as shovelling rocks and tramming it). The samples of the different tribes differ in age, but when the age effect is taken into account then there were no significant differences between tribes in maximum oxygen intakes. An incidental finding was that both age and body weight correlated significantly with the maximum oxygen intakes of these underweight subjects. Not one of the subjects who weighed less than 45 kg or who was older than 40 years had maximum oxygen intakes high enough to permit their being able to do strenuous work underground. It is clear therefore that Bantu who weigh less than 45 kg or are older than 40 years should not be employed on such strenuous tasks as shovelling rock and tramming it.

By W. A. Te Riele

The National Institute for Metallurgy was the venue for a one-day colloquium on 'The Chemistry of Processes for the Recovery of Gold on Activated Carbon'. Organized by the South African Chemical Institute (Southern Transvaal Section) in collaboration with the National Institute for Metallurgy (NIM) and the South African Institute of Mining and Metallurgy, the colloquium attracted tremendous interest from the mining industry. Some 300 metallurgists, engineers, and chemists were brought up to date on advances in this technology made by scientists of NIM and the Anglo American Research Laboratories (AARL).

Jan 1, 1980

By C. -I. Lee

Since the early 1970s, Korea has constructed many large-scale tunnels and underground storage caverns in response to the rapid industrial development. The rock mechanics engineers have accumulated valuable experiences in the area of underground space technologies. But they still face technical challenges in environmental and safety aspects. To discuss those challenges in Korea, a brief engineering description of underground space projects including oil and gas storage, food storage, pumped storage power plant, transportation tunnels, waterway tunnels, and radioactive waste disposal is presented. Mechanical and hydrological stability analyses of the storage caverns in Korea are also introduced. Depuis le début des années soixante-dix, le développement industriel rapide en Corée a entraîné la construction de nombreuses galeries et cavernes de stockage souterraines. Les ingénieurs de mécanique minière ont donc accumulé des expériences précieuses dans le domaine de la technologie de l’espace souterrain. Cependant, ils font toujours face à de nombreux défis techniques en ce qui concerne les aspects de l’environnement et de la sécurité. Pour présenter ces défis en Corée, l’étude présente décrit les projets d’espace souterrain, y compris le stockage de pétrole et de gaz, de nourriture, centrales de stockage pompé, tunnels de transport, tunnels navigables, et évacuation des déchets radioactifs. Des analyses de stabilité mécanique et hydrologique des cavernes de stockage en Corée sont aussi présentées. Seit Anfang der 70er-Jahre, baute Korea in Folge raschen Industriewachstums viele lange Tunnelsund unterirdische Lagerungsräume. Fachkräfte im Bereich Gesteinsmechanik sammeltenwertvolle Erfahrungen über unterirdische Raumtechnologien. Dennoch stehen sie auch heute nochvor technischen Herausforderungen im Bereich Umweltschutz und Sicherheit. Zur Erläuterungdieser Herausforderungen in Korea folgt eine kurze technische Beschreibung der Projekte zurSchaffung unterirdischen Raumes für beispielsweise Öl- und Gaslagerung,Nahrungsmittellagerung, Pumpspeicherwerke, Straßen- und Wasserstraßentunnels, als auchLagerung radioaktiven Mülls. Mechanische und hydrologische Stabilitätsanalysen derLagerungsräume in Korea werden ebenfalls dargestellt.

Jan 1, 2003

By F. L. D. Cloete

he above article by E. Barnea, which appeared in the January 1978 issue of the Journal (vol. 78, no. 6, pp. 143-145), calls for comment in view of the author's claims for the novelty of his proof. He states in his article that its main purpose is to give a mathematically acceptable proof by induction of the 'recently proposed' equation

Jan 1, 1978

By A. Montini, M. H. Moys

A technique for the measurement of slurry consistency inside a grinding mil is described. The rate of slurry drainage from a sensing probe mounted through the mil shell is measured and correlated with the percentage solids of the slurry discharging from the mil. The response time of the measurement(obtained on a pilot bal mil) is compared with the response time of the viscosity of the mill discharge. It is shown that the new measurement should allow much tighter control of the mil behaviour, with concomitant savings in the consumption of power and steel.

Jan 1, 1988

By G. B. Lundstrom

SYNOPSIS For some time, Vaal Reefs South has operated blindhole borers successfully as an integral part of the mining cycle of operations. To date, over 13 000 m of mechanized boxholing has been completed, and from time to time impressive performances have been achieved. The paper describes the machines, the modus operandi, and the structure of the boring organization at the Mine, with some of the results recorded. The Mine recently took delivery of two new machines with interesting design features. The introduction and early experiences with these two machines are also described.

Jan 1, 1985

By F. Q. P. Leiding

SYNOPSIS A technique is described for measuring the change in volume in a borehole drilled in a rock mass subjected to stress and strain. It is shown that the volumetric strain or change in volume provides a practical estimate of the the stress in the rock.

A description is given of a simple, cheap device that enables the intact shear strength of rock to be determined quickly and inexpensively. Thin rock plates, prepared with a diamond saw, are tested in double shear by a linear punching action. By varying the direction of the diamond-saw cut in a number of specimens, the change in shear strength can be measured for different orientations relative to the rock fabric.

Jan 1, 1980

By A. M. Thyer

Throughout the history of mining, underground fires or explosions have killed many hundreds or thousands of people. Fortunately, the safety record has gradually improved as a result of many people’s work on improving safety standards and work practices. However, fire and explosion still remains a threat in many situations. As a result the UK Mines Inspectorate commissioned a project to study materials used underground and to develop a fire/explosion risk assessment system. Such a system has been developed, following the study of incidents, specified fire resistance criteria, and fire safety practices. The final methodology uses a series of check sheets to identify potential fuels and ignition sources, preventative measures, fire/explosion mitigation systems, and items for inclusion in emergency plans.

Jan 1, 2003

By P. A. Laxen, P. J. van Staden

Alternative procedures for the recovery of gold from old sand dumps are discussed, with emphasis on the use of heap leaching. The modification of material to improve its permeability prior to heap leaching is not currently receiving much attention in South Africa. The channeling of solutions through heaps and the high consumption of reagents sometimes ascribed to heap leaching can, as shown by the results described in this paper, be lessened by desliming of the sand prior to heap leaching and the treatment of the resulting slimes fraction by agitation leaching and carbon-in-pulp. This combined procedure results in a higher overal recovery of gold. Alternatively, the sand can be heap-leached as it is after agglomeration with lime and cement, which improves the mixing and neutralization of the material, as well as lessening the probability of channeling.

Jan 1, 1988

By A. N. Brown

Underground rock boring was the topic of the mining vacation school held at the University of the Witwatersrand in the week 4th to 8th February, 1980. The School, which dealt with the management and economics of the subject, attracted 75 delegates from all sectors of the South African mining industry, in addition to two delegates from Germany and one from Zambia.

Jan 1, 1980

By P. S. Turner

After a brief account of the differences between the control of underground fires and those on the surface, the paper describes the analogue detection system used on the mines of the Anglo American Corporation of South Africa Limited. The system comprises Spanair gas analysers, Becon combustion-particle detectors, a telemetering system, a surface signal-recording and-processing system, and an alarm system. The use of the system is described and illustrated.

Jan 1, 1982

By Z. Botha

Sheryl Sandberg, the COO of Facebook, published a book titled 'Lean In', where she invites women to sit at the table. In summary, to 'sit at the table' entails not only embracing opportunity, but to actively seek out opportunities in leadership positions. Sandberg points out that, unfortunately, apart from institutional obstacles, a woman's own perceived limitations have a negative impact on her leadership ambitions. To create an environment where diversity will flourish, where everyone has a seat at the table and everyone has a voice, safety must be established first. To establish safety within a diverse team, there is power in relationships and connections. This study will first and foremost review theories in literature as to why diversity and inclusion are so important and the value that diversity brings to our industry. The study also recommends a few focus areas for improving diversity and inclusion in the industry.

Sep 1, 2022

By J. E. Robinson, W. Pilkington, J. L. Taylor, B. J. Bluhm, E. B. Viljoen, P. Le Grange

The Chemwes uranium plant was designed and constructed within fifteen months; commissioning started during. June 1979, and the plant was producing at design capacity four months later. This account highlights the procedures and methods adopted to bring the plant Into production. The description of the various phases includes some details of the early evaluation, and the feasibility and optimization studies; of the financing, project management, design, construction, and commissioning of the plant; and of the training of personnel. Some of the mistakes made and the factors that contributed to the success are also listed.

Jan 1, 1981

By C. A. Snyders

The research presented in this paper investigated the practical aspects of the recovery of platinum group metals (PGMs) from a dilute cyanide leach solution containing base metals, in a manner similar to that used for gold extraction in a typical CIP process, and focuses on both the adsorption and elution stages. The carrier-phase extraction of precious metals using activated carbon offers significant advantages over other processes in terms of simplicity, the high pre-concentration factor, rapid phase separation, and relatively low capital and operating costs. As a sorbent, activated carbon is still by far the most important material because of its large surface area, high adsorption capacity, porous structure, negligible environmental toxicity, low cost, and high purity standards. Adsorption tests were conducted on a pregnant alkaline leach solution (0.15 ppm Pt, 0.38 ppm Pd, 0.1 ppm Au) resulting from cyanide extraction performed in column leach tests. The initial adsorption rates of Pt, Pd, and Au were very fast and recoveries of these three metals were approximately 90 per cent after 2 hours, and 100 per cent for Pt, 97.4 per cent for Pd, and 99.9 per cent for Au after 72 hours. The parameters that influence the extraction of PGMs and Au were examined to assess their relative importance during the adsorption process in order to provide the basis for process optimization. The concentration of thiocyanate was not identified as significant factor for PGMs adsorption, while Ni concentration was the most significant extraction process parameter. Base metal cyanide complexes adsorb and compete with the PGM complexes for sites on activated carbon, and while copper adsorption can be minimized by adjusting the residence time, Ni adsorbs at approximately the same rate as the PGMs, influencing the loading capacity and adsorption kinetics of the PGMs. The feasibility of eluting platinum and palladium cyanide complexes from activated carbon using an analogue of the AARL process was investigated. Platinum and palladium elute from activated carbon almost to completion in 4 to 5 bed volumes at 80°C, while the elution of gold at this temperature is slow, with a significant amount of gold still to be eluted after 16 bed volumes. The equilibrium loading of gold is exothermic in nature (Fleming and Nicol, 1984) which will result in an increase in gold elution kinetics with an increase in temperature at similar pre-treatment conditions. A similar result was found for the elution of Pt and Pd. Cyanide pre-treatment was found to have a significant influence on PGM elution. Higher cyanide concentration in the pre-treatment step results in more efficient elution up to a point, and results suggest the possibility of an optimum cyanide concentration, beyond which elution efficiency starts decreasing due to increased ionic strength.

Jan 1, 2013

By M. L. Mahlatji

Mechanical alloying of an equiatomic mixture of crystalline Ti and Pt elemental powders in a high-energy ball mill formed an amorphous alloy by solid-state reactions. Mechanical alloying was carried out in an argon atmosphere at a rotation speed of 1200 r/min and a 20:1 ball-to-powder weight ratio, for time intervals of 4 to 40 hours. At an intermediate stage of mechanical alloying, scanning electron microscopy showed the formation of characteristic layered structures of inhomogeneous composition within the powder particles. X-ray diffraction analysis showed the gradual disappearance of crystalline Bragg peaks and the emergence of broad amorphous maxima as milling progressed. The amorphization process was completed after 8?12 hours. The amorphous state of the product indicated that temperatures during processing did not exceed the crystallization temperature of the alloy.

Jan 1, 2014