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By J. P. Van Dillen

Continuing interest in processes that will effect separations in the fine particle size range has prompted intense interest in the use of high gradient magnetic separation (HGMS) for beneficiation of uranium ores. Some of the uranium minerals are paramagnetic and hence are amenable to concentration by HGMS. This paper presents a brief review of the problems associated with uranium ores beneficiation, a description of the HGNS process, and the effects of the parameters--pulp velocity, field strength, matrix loading and magnetic field gradient on product recovery and grade. Unsatisfactory separation of uranium minerals by HGHS is related to ore specific properties such as lack of liberation, fine dissemination of uranium minerals, uniform distribution of magnetic minerals throughout the ore matrix and interference of micron sized slimes. Experimental techniques to identify and resolve some of these problems are outlined.

Jan 1, 1982

By I. J. Jansen

Successful soil construction involves preparation of an adequate base, selection of high quality soil materials, and placement of those materials by means which will establish a continuous macropore network and modest to low soil strength. Where such has been accomplished, experiments reveal row crop productivity on reclaimed land which is very competitive with that on undisturbed land. Inferior productivity and sensitivity to drought stress are experienced where the soils are excessively compacted during construction. Some deep tillage practices have been quite successful in improving the compacted soils, but it is preferable to avoid compaction as the soil materials are handled.

Jan 1, 1987

By Roland B. Drugge

The adaptation of pelletizing processes involves the coordination of various factors such as temperatures, gas flows, productions, etc., in order to obtain optimum performance. The consequent problems are considerable due to the large number involved as well as the lack of knowledge of their correlation. It is therefore essential to establish a fundamental theory which takes into account the heat transfer phenomena and the secondary factors which are relevant to the properties of the product. Straight grate and grate kiln pelletizing processes involve heating of a stationary bed on a travelling grate. The heat transfer conditions are therefore of primary importance. This is why this article pays particular attention to conditions which obtain when a stationary bed is heated, in which certain special reactions occur. The conclusions drawn from this penetration of the heat transfer phenomena can be expressed in postulates acting as guide-lines for the establishment of proto-typal processes. Examples of elaborating such processes are also given in the article. Some operational experience at LKAB are also given.

Jan 1, 1975

By L. T. Matthews, C. E. Loo

During sintering, porous ore particles are easily assimilated by liquid melt. Two simple models of the process are considered: the dissolution of a solid by a liquid and the penetration of a liquid into a porous solid. Laboratory sintering studies covering a range of experimental conditions were undertaken to characterise the assimilation of large particles of ore and flux by melts formed from different mixes of fines. For ores, the process appeared to be complicated by the detachment of fines from the ore surface prior to melt formation, according to the mass of adhering fines and surface roughness of the particle. This delayed the onset of assimilation and sometimes reduced it, although melt penetration was fast and effective. Studies using different temperature profiles suggested that the assimilation of haematite was controlled by the transport of Fe2O3 away from the surface of ore particles. The assimilation of limestone depended more on thermal conditions than on the three magnesia-bearing minerals considered. Changing the composition of the initial melt significantly altered the extent of assimilation of ores and limestone, but again had a less marked effect on the magnesia-bearing fluxes.

Jan 8, 1992

By Yohan Cha, Eun-soo Hong, Gye-Chun Cho

"Rapid population growth and scarcity of space have led many developed cities to bury supply facilities. In line with this, utility tunnels have been employed in Korea since the 1970s. However, approximately 70% of structures were installed more than 20 years ago, in response to the issue of ageing, tunnel enlargement has been proposed. The aim of this study is to investigate geo-mechanical behavior due to tunnel enlargement. Tunnel enlargement methods have been researched to suggest a optimal method. A finite element analysis is conducted to evaluate ground behavior by the expansion of internal space. Vertical displacement and settlement trough width are investigated according to ground stiffness and different enlargement size. It was determined that displacement is affected by the enlargement size and ground stiffness. Based on the deformation results obtained from the numerical analysis, it is possible to predict ground behavior and stability upon tunnel enlargement. INTRODUCTION Various infrastructures such as electric lines, communication lines, gas pipes, and water pipes are jointly accommodated by utility tunnels. These utility tunnels improve the aesthetics of urban areas and help ensure stable supply. The first utility tunnel in Korea was adopted in 1978 and new tunnels are still being installed with the development of new suburb cities. Nevertheless, about 70% of the utility tunnels were installed over 20 years ago and they are still being used through ongoing repair. Moreover, 90% of utility tunnels were installed before 1995. With aging of the nation’s utility tunnels various problems such as concrete deterioration and scarcity of capacity have arisen. As solution, reconstruction has been considered. Reconstruction can enlarge space and improve the performance by replacing existing structures. For reconstruction, two routes have been proposed: underground excavation and cut and cover. In order to avoid traffic problems caused by road occupation and civil appeals during construction projects, underground excavation is the more attractive option. Tunnel enlargement methods have been classified (Seo et al., 2008; An et al 2013) and major considerations during tunnel enlargement have been outlined (Beak et al., 2007). Enlargement construction cases on road tunnels around the world were introduced (Kim et al., 2012) and the deformation curve during tunnel expansion was proposed to investigate the range of protection that should be offered (Kim et al., 2008; Beak et al., 2011). However, tunnel enlargement technology is limited to road tunnels and railway tunnels. Hence, a study on shallow box tunnel enlargement is required for practical application."

Jan 1, 2016

By A. Anttila

The grinding mill is probably the most common unit operation used in mineral processing. There is, however, much which can still be done in the way of optimization. This paper discusses the results of a well controlled pilot scale test in which the performance of a tumbling mill with a conventional rubber lining equipped with lifter bars is compared to that with a smooth rubber lining of the magnetic type. The results indicate that the smooth lining is about 14 percent more effective with respect to energy consumption. By optimizing the size of the grinding media, the mill capacity can be increased in many grinding operations. In this specific case the -20 mm ball charge required 26 percent less grinding energy than one with a -30 mm ball charge. The energy savings can. in most cases, be converted to increased capacity. The wear of the grinding media is difficult to assess over a short period test but the results suggest it is somewhat less when a smooth lining is used. The wear of the linings has not been included in this study but it is generally accepted that the use of the magnetic lining reduces the lining costs dramatically. Computer simulation using the Millsoft code, developed by Mishra e.a. confirms and explains the increased effectiveness of comminution when smooth lining and smaller grinding balls are used.

Jan 1, 1998

By Ajit Kumar Jaiswal

"Electric Arc Furnace (EAF) being a power-intensive equipment, EAF based industries are highly dependent on scarce electric energy. This is the reason Government of India is highly concerned about this and laid emphasis on the conservation of electric energy.This paper highlights factors contributing to reduction in specific electric energy consumption in EAF and suggests measures not only for power saving, but also for productivity improvement. To name a few, these are proper sealing of furnace, introduction of oxy-fuel burners, foamy slag practice, increased usage of hot metal/DRI, post-combustion of CO gas for preheating of scrap, improved selection & design criteria of electrics, power demand management, and process automation. Few cases also have been cited, where the above measures have helped in reaping significant benefits.IntroductionFor a long time, Government of India had focused on increase in energy supply, in particular, through electricity generation. Now the emphasis of Government of India has shifted from electricity generation to its conservation for following two reasons:??Power plants have become very cost-intensive??By saving energy, more of it can be delivered at lower cost to the consumersPower generating units, transmission & distribution agencies as well as consumers all have roles to play in the area of energy conservation. By energy conservation, we mean curtailing energy requirement by reducing energy wastages and taking up measures to improve energy efficiency of electric equipment/appliances. In almost all cases, this would be economically beneficial.India’s cost-effective energy conservation potential has been estimated by the Planning Commission at 23 per cent of total commercial energy generated ?1?. A national movement for energy conservation can significantly reduce the need for fresh investment in energy supply systems in coming years. It is imperative that we make all-out effort to realize this potential. Whether a household or a factory, a small shop or a large commercial building, a farmer or an office worker, every user can and must make this effort for his own benefit and for the nation’s benefit as well."

Jan 1, 2009

By Yuanbo Zhang, Zhixiong You, Daoxian Duan, Guanghui Li, Tao Jiang

"Manganese is mainly consumed by steel and battery industries. In recent years, it is essential to utilize the low-grade manganese oxide ores with total manganese grade below 25%, as the high quality manganese ore resources are becoming scarce with the rapid development of the steel industry. Conventional pyro-metallurgical processes for utilizing manganese oxide ores are characterized by high production cost and energy consumption, low productivity, serious environmental pollution, etc. In this study, reduction thermodynamic of MnO2 reduced by sulfur was firstly carried out. Then, a novel process of reduction roasting with sulfur followed by acid leaching was developed to recover manganese from the very low-grade manganese oxide ores. Effects of main factors, including temperature, reduction time and S/Mn mole ratio, were investigated, and a high leaching efficiency of Mn above 95% was obtained under optimal conditions.IntroductionHigh/middle-grade manganese oxide ores are generally used in the metallurgical industries, particularly in steel plants and ferro-alloy units. The consumption of metal manganese in the ferro-alloy industry accounts for 85- 90% of the total Mn demanded [1]. Therefore, high quality manganese ore resources are becoming scarce with the rapid development of steel industry. It is essential to make good use of large quantity of low-grade manganese ores (TMn < 25%) presently available."

Jan 1, 2012

By Cynthia K. Belt

Improved energy efficiency has grown in importance within industry as energy costs have escalated. The analysis of trends and changes to a process is critical in making the best business decision in energy management. Frequently, energy use per day (Kilowatt-Hour or British Thermal Units) is used to track energy efficiency. Sometimes, the somewhat more complex method of energy per processed weight (Kilowatt-Hour per Metric Ton or BTU per Pound) is used to make this evaluation. Yet both methods ignore the effects due to throughput and weather. In this paper, different thermal processes and systems will be evaluated using statistical methods to highlight alternative methods to evaluate energy efficiency. Examples and potential problems will be discussed for both a single process and a collection of processes within a plant or corporation.

Jan 1, 2008

By Mark Cross, Andrew P. Campbell, Koulis A. Pericleous

"Computational Fluid Dynamics (CFD) modelling is being used to simulate the freeze layers formed within direct smelting processes. There has been some concern whether water-cooled elements can withstand the p~ocess conditions and in particular abnormal cases where they may be splashed in molten metal.To validate the models being developed, two cases from literature have been modelled for solidification and stress analysis. The solidification case is presented in detail and is for hot molten metal flowing through a cylindrical pipe. The walls are at a temperature below the melting point for the metal. The resulting solid (or freeze) layer is within 3% of the value calculated by Sampson & Gibson9 •Preliminary modelling of the refractory-slag interactions is presented. Although three basic mechanisms: Penetration; Corrosion; and Erosion will eventually be modelled, only the penetration is considered here. The corrosion mechanism is to be modelled by tracking the time that the penetrated refractory is at the required temperature.Future work, after adding all the required physics, will focus on the modelling of a water-cooled element placed lower in the smelter. Process perturbations will be simulated to examine what these elements will withstand."

Jan 1, 2001

By Haibin Wang, Kaile Tang, Chenn Q. Zhou, Guangwu Tang, Zhixiang Cui, Ping Zhou, Armin K. Silaen, Hongjie Yan, Zhi Wang

The submerged lance smelting furnace (SLS) for copper smelting has been developed and used by Dongying Fangyuan Nonferrous Metals Co., Ltd. The technology has shown advantages such as high oxygen enrichment, good feed adaptability, short processing time, high SO2 concentration for acid plant, and auto-thermal operation. In this study, computational fluid dynamics (CFD) was used to investigate the gas/matte two-phase flow characteristics and the chemical reactions in the SLS during typical operational conditions. The Eulerian-Eulerian approach was employed to model the phase interactions. The chemical reactions were modeled by calculating the mass transfer coef ficients and using the eddy-dissipation model. The simulation was conducted using the commercial software ANSYS Fluent®. The developed CFD model is able to predict the flow, temperature, and species distributions inside the SLS under various operating conditions.

Mar 1, 2018

By G K. Robinson, M D. Sinnott

Three-dimensional granular flow models have been run to simulate three types of sample cutters: a cross-stream cutter, a vezin, and a cross-belt cutter. This type of modelling involves solving the equations of motion for large numbers of individual particles as they travel along a conveyor belt and interact with a sample cutter. It allows flows of bulk materials to be visualised and understood. Here we have used spherical particles. These results illustrate some advantages that modelling has compared to physical bias testing: By taking reference samples which are very close to the actual samples, the estimation of bias can be achieve quite precisely with very few runs. (Many Standards about bias testing recommend a minimum of 20 runs, but we have found that five runs generally provide adequate precision.) Potential bias can be divided into two components: the particles which are missed but should have been sampled and the particles which are extra but which should not have been sampled. This more detailed information can provide useful insight. Exactly the same material can be sampled using different sample cutters, thereby avoiding a source of variation that complicates physical testing. Much more detailed visualisation is possible, allowing better understanding of the bulk material flow in various circumstances.

Jan 1, 2005

Jan 1, 2008

By R R. Anand

Recent research by CRC LEME from an Australian mineral exploration perspective, has focussed on regolith architecture and mechanisms of geochemical anomaly formation, within transported regolith. Methods have been developed for the rapid production of regolith-landform maps which is the starting point for understanding regolith architecture in the third dimension. Methods for development of 3D regolith models are less well advanced, and require integration of all available geological and geophysical datasets, but still with a heavy reliance on drill-hole information. The base of the transported regolith û the unconformity û remains the most important regolith boundary for geochemical sampling in transported regolith terrains. A new generation portable spectral logger, employing a broader spectrum can interpret important features from drill chips within the regolith. This allows internal architecture, redox fronts and the all-important interface to be objectively identified. Transported lateritic components can provide vectors to mineralisation in depositional regimes. Palaeomagnetic and new radiometric methods which date individual phases of the regolith provide evidence of different episodes, each characterised by different geochemical dispersion patterns in transported regolith. Along with lateritic residuum, calcrete is prime sampling medium. Calcrete is probably enriched in gold through physical and biological processes, rather than straight chemical processes. In South Australia, the lowermost calcrete layer buried within the depositional regime, especially where it lies directly over the silcrete layer at the buried interface, is the desired sampling medium. Certain gum trees, with deep roots in transported regolith have been shown to record anomalous values of gold and basemetals in leaves, twigs and bark. Anomalous metals in acid-sulfate soil seeps can also provide a window through sedimentary cover in respect of mineralisation in the basement. A number of Yilgarn occurrences of gold anomalies in transported cover, strongly infer hydromorphic and biological mobilisation of gold. This inference is supported by micro-analyses of regolith mineral hosts in hardpans and mottled sediments, which show gold and pathfinder elements prefer to reside in goethite and specific types of clay minerals. This creates anomalies in specific mineral phases. However the inference that that these are sites of mobile or labile metal ions remains enigmatic. Similarly there is inconclusive evidence that selective extractions will provide an anomaly not otherwise detected by conventional total dissolution methods. Hydrogeochemistry is a promising exploration tool for basemetal exploration. The importance of microbes in both the dissolution and precipitation of gold in the Australian regolith is demonstrated. We are on the verge of identifying the functional gene sequence of individual active microbes. A consideration of possible mechanisms for creating anomalies in soils above transported regolith, presents difficulties in facilitating upward movement of ions from the watertable to the surface. Perhaps the best avenues of research lies with surrogate soil gases, and biotic transfers.

Jan 1, 2004

By S. M. Marshall

FOR a number of years European investigators have used laboratory methods of predicting the probable strength of coke made from coal, and recently several investigators in the United States have reported the use of various tests for this purpose. There is at present no method accepted as standard, however, nor is there even agreement as to the general type of test that should be used. Furthermore, because the details of most of the tests have not been worked out carefully, one investigator can not hope to duplicate the work of another. The extension of coke manufacture to new localities in the United States, and the increasing need for cokes of exceptional qualities made from the most economical mixtures, made it desirable to have some simple laboratory test which will determine whether given coals, alone or blended with other coals, are more satisfactory from the standpoint of coke strength than others of different cost. The work described herein has resulted in the development of a simple laboratory test which, it is believed, can be generally adopted in coal laboratories, and which will give concordant results even though performed by different investigators in different laboratories. The general method of predicting whether a coal or a mixture of coals will produce a strong coke, resistant to crushing and shattering, has been to correlate the known strengths of the cokes produced in commercial ovens with some measurable constituent or with some property of the coals, and then to use the relationship so found for forming an estimate of the coking strengths of coals unknown. Several such correlations have utilized the percentages of the various ultimate constituents of coal, such as the oxygen content and the hydrogen-oxygen ratio;(39)§ other correlations have involved the proportion of a, (3 and y compounds, (17&apos;21,30 or of "oil and solid bitumens."(16,30) Also a relationship has been traced between the coking properties of coal and the rate of change of the resistance offered to the flow of an inert gas by fine particles of the coal while being slowly heated. (11,17b) But the most general corre-

Jan 1, 1929

By G. N. Goldberg, Robert A. Rapp

The steady-state kinetics and microstructures of simultaneous internal oxidation and external scale formation were investigated for the oxidation of Cb-Zr and Ch-Zr-Re alloys in pure oxygen at 1000°C. For each binary alloy, a constant rate of scale formation was observed at steady state; the internal oxidatton zone reached a steady-state, time-independent thickness. The dependence of the scaling rate on zirconium content exhibited a maximum at a low zirconium colttent; more concentrated alloys oxidized at a slower rate than pure columbium. This composition dependence of the scaling rate may be partially attributed to the effect of the internal oxidation process as an intenla1 sink for oxygen, with the formation of voluminous, and relatively impermeable ZrO2 precipitates. However, the morphologies of the ZrO2 internal oxide precipitates also affected the scaling rate. The internal oxide precipitates were distributed uniformly in the external scale. The steady-state thicknesses of the internal oxidation zones were not in agreement with those predicted theoretically from an idealized simple model. However, in this particular alloy systen1 the ideal model is not satisfied experitmentally. For ternary Cb- Zr - Re alloys with Nr10e = 0.02 or 0.05, the steady-state thicknesses of the internal oxidation zones were less than those for the corresponding binary Cb-Zr alloys. For ternary alloys with NRe(0) - 0.05, a more adherent and much less porous external scale was formed, and a reduction in the kinetics of scale formation was observed. A number of authors&apos;-7 have reported linear oxidation kinetics for the reaction of pure columbium at 1000°C in air or in oxygen of about 1 atm pressure. A thin and tightly adherent oxide layer is found at the metal/oxide interface beneath a porous external layer of scale. Although the suboxides CbO and CbO2 represent thermodynamically stable phases at 100O°C, generally only Cb2O5* is identified as a reaction product in quenched specimens. Studies at 1000°C at lower oxygen pressures8,10 (Po2 - 10-4 Torr) show that both CbO and CbO2 do form and that CbO2 is a protective oxide. The growth of CbO2 results in parabolic kinetics until Cb2O5 is nucleated and grows. Apparently because of the large volume change associated with its formation, Cb2O5 is porous and does not serve as a diffusion barrier; linear kinetics prevail after the surface is covered with Cb2o5. On the basis of these observations, several authors5,9,10 have suggested that the linear oxidation of pure columbium at 1000°C in air or oxygen of 1 atm is limited by a Loriers-type mechanism,11 whereby the total rate or reaction is controlled by ionic diffusion through a thin layer of CbO2 which is maintained at a constant thickness throughout the linear oxidation. However, the concept of a Loriers model for a three-phase CbOlCbO2 Cb2O5 scale, with the only oxygen activity gradient across the NbO2 phase, is not self-consistent. Further, the suboxides CbO and CbO2 were not observed in the high-temperature X-ray diffraction study of columbium oxidation by Goldschmidt.8 From investigations in which the large PO2, dependence of the linear scaling rate was demonstrated, the importance of an oxygen adsorption or dissolution step has been suggested.4,5,7,10,12 Thus the mechanism for the linear oxidation of pure columbium remains quite controversial. Since further insight into the oxidation mechanism of pure columbium is not provided by this investigation, the authors wish to emphasize at the outset that their experimental results are not interpreted in terms of a particular rate controlling step for the oxidation of pure columbium. Previous investigations13-18 of the oxidation of Cb-Zr solid-solution alloys in air or oxygen at 1000°C suggest a remarkable dependence upon zirconium content. For an alloy of bulk zirconium mole fraction, N2r(0) equal to 0.05 or 0.10, the oxygen uptake is reported to be as high as four times greater than that for pure columbium;13,14 for alloys with NZr(0) 0.05 or 0.10 the oxygen uptake is reported to decrease with increasing NZr(0); to a minimum uptake of about one quarter that for pure columbium at NZr(0): = 0.50.13-15Since zirconium forms a more stable oxide (ZrO2) than the lowest columbium oxide (CbO), and since columbium exhibits a high solubility19,20 and diffusivity21,23 for oxygen, the internal oxidation of the zirconium component to ZrO2 is expected at a reaction front ahead of the advancing metal/scale interface. The external scale is then formed at the metal/scale interface by the inward migration of oxygen through the scale, probably through a series combination of molecular and ionic diffusion. Internal oxidation in conjunction with external scale formation has been investigated by Maak24 for the oxidation of dilute Cu-Be alloys in pure oxygen at 850°C. For cu-Be and many other binary alloys,24-27 very small, essentially uniaxial internal oxide particles are formed in the most dilute compositions; for somewhat more concentrated alloys. the internal oxide particles precipitate as platelets or needles. From pertinent solutions to the diffusion equation, Maak28

Jan 1, 1967

By S. W. Miller

DURING the examination of welds made in steel by the oxy-acetylene and electric-arc processes, the writer has met with some unusual structures, which he has not encountered elsewhere. They seem to be quite closely associated with the welding methods used, and characteristic of them, and would seem to be worth noting, especially as the references to them in the literature are few, and their explanation not clear or complete. An introductory word or two about fusion welding may not he out of place. The oxy-acetylene process is based on the great and very local heat generated by the burning of acetylene in the presence of commercially pure oxygen, the two gases being thoroughly mixed before combustion. The theoretical temperature is somewhat under 4000° C., but on account of various losses, the actual maximum temperature is probably about 3000° C. 1 The electric-arc process, using a metal electrode, which is also the filling rod, generates a still higher and more local temperature. The actual temperature of the positive crater of the carbon arc is given as 3500° C.2 No figures have been found for the temperature of the arc using a metal electrode, but it would probably not be very different from that of the carbon arc, and probably higher than that of the oxy-acetylene flame. The greater localization of the electric arc is due to the fact that it is not surrounded by a large envelope flame as well as to its higher temperature; while the oxy-acetylene white cone, or welding flame, in which the carbon of the acetylene is burned to CO, is surrounded and preceded by -a long envelope flame, itself of quite high temperature, in which the CO is burned to C02, and the hydrogen of the acetylene to

Jan 2, 1918

By J. E. Steiner, J. M. Hodge, M. A. Orehoski

Ingots of four steels (1045, 1080, Ni-Mo-V, and Ni-Cr-Mo-V) were cast at pressures varying from about 1 to 760 mm of mercury, so as to obtain a range of hydrogen contents in each steel. The susceptibility of these steels to flaking was evaluated by cooling hot-rolled blooms at a range of cooling rates, varying from water quenching to slag cooling, and studying the occurrence of flaking as a function of cooling rate. The steels exhibited differences in susceptibility to flaking, and a tlzreshold value for hydrogen content for each steel was found, below which the susceptibility was very low and above which the susceptibility increased markedly with increasing hydrogen content. Mechanical property evaluations, metallogvaplzic exantinations, and X-my diffraction determinations o,t retained austenite were made on samples from the blooms. A mechanism of flaking which is consistent with the observed behaviors, the effects of hvdrogen content, and the differences in susceptibility among the steels investigated is postulated, based on the results of mechanical property evaluations and metallographic and X-ray diffraction studies. ThE important role of hydrogen as a factor in the occurrence of "flakes" or "hair-line cracks" in steel has now been established by many investigations. These have included investigations by steel producers and forging manufacturers, to whom the prevention of flaking is a very real and serious problem, and many research studies aimed primarily at establishing the mechanism of this behavior Several investigators3 have reported that steels cast at reduced pressures (absolute pressures of about 1 mm) not only are low in hydrogen content but are essentially insensitive to the formation of flakes. These investigations have shown that a general relationship exists between hydrogen content and susceptibility to flaking. The difficulty of obtaining suitable samples of steels of a given composition with the desired range of hydrogen contents, particularly in the relatively large sections in which flaking most commonly occurs, has been the principal obstacle to quantitative evaluations of these relationships. Steels with intermediate hydrogen contents between 1 ppm, and the 4ppm or higher of air-cast steels are generally not available in commercially produced steels. Laboratory procedures, in which the hydrogen is introduced into solid steel samples by heating in a hydrogen atmosphere under pressure, generally involve a limitation in the size of the sample which can be treated, and thus are not representative of the behaviors in large sections. The availability of a facility at the South Chicago Works of U.S. Steel, in which several ingots could be cast from a single heat of steel at total air pressures ranging from 0.25 to 760 mm of Hg, has made it possible to overcome this obstacle and to obtain ingots of a given steel covering the intermediate range of hydrogen contents desired. These ingots, furthermore, are of a size suitable for the production of product with section sizes large enough to be representative of the products in which flaking most commonly occurs in commercial production. In these experiments, this facility was used to study the relationships between hydrogen content and the susceptibility to flaking of four steels, two plain carbon steels at 0.45 and 0.80 pct C and two low-carbon alloy steels representing a medium and a rather high hardenability level. These flaking studies were supplemented by evaluations of mechanical properties and by metallographic studies on samples from the blooms, in order to obtain pertinent information on the factors other than hydrogen content which influence the susceptibilities of these steels to flaking. Based on the results of these tests, a mechanism for the initiation and propagation of the flaking cracks, which is consistent with the observed behaviors, is postulated. MATERIALS AND EXPERIMENTAL WORK Steelmaking and Conversion. To provide material for the investigation, five 29- by 35-in., hot-topped, big-end-up ingots were cast from each of four 80-ton, basic electric-furnace heats of four different steels (a 1045 steel, a 1080 steel, a Ni-Mo-V steel, and a Ni-Cr-Mo-V steel). A double-slag practice was used on all steels and the two plain carbon steels were Si-A1 deoxidized with an addition of 2 lb of A1 per ton, while the Ni-Mo-V and Ni-Cr-Mo-V steels were deoxidized only with silicon and

Jan 1, 1964

Jan 1, 1888

By G. J. C. Young

The paper describes the replacement of a conventional filtration, clarification and zinc precipitation plant by a carbon in pulp (CIP) electrowinning plant, with the objective of improving the recovery of gold from cyanide leached, acid plant calcines. The discussion covers the early laboratory studies to the design and erection of the full scale plant. Particular emphasis is placed on the problems encountered with commissioning and the strategies which were employed to solve them.

Jan 1, 1982