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By Thomas L. Ochs

The Bureau of Mines is investigating the fundamental behavior of electric arcs in electric furnace operations. The electric arc is a poorly understood phenomenon. If the arc in a steelmaking furnace can be more carefully controlled, it should be possible to increase heat transfer to the melt, reducing both electrical and acoustical noise. As a first step toward a better understanding of the are, voltage and current signals from operating furnaces were analyzed. The results of the initial analysis show that instrumentation used in monitoring and controlling furnaces, such as meters and strip-chart recorders, gives incomplete or erroneous information to the operator and therefore leads to less than optimal control. Advanced instrumentation and analysis techniques, such as the waveform analysis used in these investigations, can improve the understanding of operation and the control of electric furnaces. This report describes the instrumentation and the numerical analysis methods used and compares these methods with standard metering and recording techniques.

Jan 1, 1986

By P Dowd, R Jeuken, C Xu

In Australian coalmines there are a number of coal quality parameters that are measured by analysing samples from boreholes. The data points are used to generate spatial models of these parameters, typically using inverse distance as an interpolation method. Numerous additional boreholes are drilled which have geophysical logs measured downhole but from which no coal quality samples are taken. Full suites of coal quality analyses are expensive and time consuming to drill and sample. If geophysical proxies for coal quality could be used, this would greatly improve the accuracy of the resource estimation without additional cost.This paper examines two of the most important coal quality parameters – ash and volatile matter – and assesses the results of a number of geostatistical interpolation methods. The aim is to improve the accuracy of the interpolated models. Auxiliary variables from geophysical logs are also trialled to improve the estimation.A multivariate analysis of ash, volatile matter and several auxiliary variables of a selected coal seam was undertaken in a spatial context, using variography. This was used to construct a model of co-regionalisation that relates all of the variables as manifestations of an underlying geological theme.The traditional inverse distance interpolation approach was compared to ordinary kriging, universal kriging, co-kriging, regression kriging and kriging with external drift approaches. The relative merits of the six interpolation methods were compared by removing all points, one at a time and estimating at the thus known location. The mean error and the root mean square error were evaluated as a measure of bias and precision.This paper demonstrates that there is significant opportunity to improve the estimations of coal quality when using kriging with external drift. For example, the results show that when using the depth of a sample as an external drift variable there is a significant improvement in the accuracy of estimation for volatile matter. Furthermore, when using borehole wireline density logs as an auxiliary variable for ash content, there is improvement in the estimation of the in situ ash. The underpinning reasons for this are discussed in the context of the underlying geology and the physical properties of the coal. These findings hold promise for utilising cheaper proxies for coal quality parameters to dramatically improve data density and the quality of estimations.CITATION:Jeuken, R, Xu, C and Dowd, P, 2017. Improving coal quality estimations using geostatistics and auxiliary variables, in Proceedings Tenth International Mining Geology Conference 2017, pp 157–168 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 20, 2017

By Lim Thi Duong, Du Duy Bui, Thuat Ngoc Pham, Chuc Ngoc Pham, Que Anh Nguyen, Hoa Anh Bui, Chi Thi Ha Nguyen, Hoan Thanh Nguyen, Bac Quang Nguyen, Kien Trung Nguyen, Dung Trung Doan, Nhiem Ngoc Dao

The microstructures and kinetics of a rich iron ore ( TFe = 65.84%) of Na Rua mine, Vietnam, used for the iron production were investigated in this study. Thermal behaviors of iron ores were well-examined by heating microscopy, thermogravimetric analysis, and differential thermal analysis. After being pelletized and then oxidatively fired at 500–1200 °C for 2 h, the pellets fired at 1200 °C (P1200) displayed a hard and dense structure with a decent compressive strength of 317.9 kg/pellet whereas those fired at 500 °C (P500) had a soft and spongy structure. The reduction of iron pellets conducted in a flow of a 60–100% CO2/ Ar gas mixture at 900–1100 °C showed significantly higher efficiency than the reduction using coal. The spongy pellets showed superior performance for the reduction in the CO/Ar gas mixture compared to the dense ones, compatible with the production of sponge iron. When mixed with an amount of coal, P1200 designed for iron production in the blast furnace demonstrated an impressive reduction activity compared to P500 and previous studies. The kinetics of pellet reduction was determined by the diffusion of substances through the solid product layers having the mathematical model of 1 − 2 3 f − (1 − f )2∕3 = kt . The microstructures of pellets during the oxidative firing and reduction were also examined by X-ray diffractometry; scanning electronic microscopy; energy-dispersive X-ray spectroscopy; and Brunauer, Emmet, and Teller method.

Jun 7, 2022

By Robert M. Keeney, Jay Lonergan

The electric smelting of manganese ore and the production of ferro-manganese did not exist as an industry, in the United States or elsewhere, previous to the outbreak of war in 1914. Ferromanganese had been produced, electrically, during times of high prices by two companies at Niagara Falls and by several European companies, but the production was spasmodic, and none was electrically produced when ferromanganese sold at from $35 to $40 per ton. Thus the electric smelting of manganese ore must be considered as a development caused by the high prices prevailing during the years 1916, 1917 and 1918, and the necessity of smelting domestic ore in order to fill the ferromanganese requirements of the steel industry of the United States, which increased from 189,088 tons in 1914 to 356,356 tons in 1918. The electric furnace is well adapted to smelting domestic ore because it can be located in small units near the source of ore supply. In 1918, the ferromanganese production of the United States was 333,027 tons, of which about 7 per cent., or 23,000 tons, was produced in the electric furnace. The electric furnace not only assisted materially in the development of a domestic-ore supply but made a considerable saving of coke, as it requires about 11/4 tons of bituminous or lignite coal per ton of ferromanganese compared with a blast-furnace consumption of 2.9 tons of coke per ton of ferromanganese. Some of the plants in the United States that smelted manganese orc in the electric furnace during the war and in 1920 are listed in Table 1. From early in 1919 to about February, 1920, little ferromanganese was produced in the electric furnace. During this period the price of ferromanganese (78 to 82 per cent. manganese) was about $100 per ton. During the first half of 1920, several plants resumed operation when the price of ferromanganese (76 to 80 per cent. grade) gradually increased to $200 per ton, delivered.

Jan 1, 1922

By Guillermo Zuloaga

The iron deposits of the Imataca Range of Venezuela, which occur along the Orinoco River, in the northern border of the Guayana Highlands, have lately attracted attention on account of their economic possibilities. Many deposits occur in this area; some of slight economic importance and others that may rank with the largest masses of high-grade iron ore of the world. The geology and the character of the ores seem to be remarkably similar to those of the large iron deposits of Brazil. In the investigation of the Venezuelan deposits a definite relationship has been found between the mineralization of the large orebodies and igneous intrusions, especially norites and granites. The following paper is the result of a field and laboratory investigation of the ore deposits. The field work was done during the months of February and March of the year 1929, partly in the company of Prof. W. H. Newhouse. The laboratory studies have been made in the Massachusetts Institute of Technology, under the supervision of Professor Lindgren and Professor Newhouse. GENERAL GEOLOGY OF GUAYANA HIGHLANDS General Geography and Physiography The Sierra de Imataca proper occupies a narrow belt along the south bank of the Orinoco River, in the northeastern part of the State of Bolivar and in the western part of the Delta Amacuro Territory of Venezuela. The State of Bolivar is generally known as the Venezuelan Guayana, as it forms part of the same physiographic province of the Guianas and northeast Brazil. In general the Venezuelan Guayana is an extensive plateau, sloping gently towards the Orinoco River to the north and towards the Atlantic Ocean to the east. In the northern part mountains are rare, and consist mainly of elongated low hills. Towards the British Guiana-Brazil boundary, table mountains with vertical cliffs are found forming the ranges of Parima, Roraima and Pacaraima. General Geology The Guayana Highlands are the northern extension of the Brazilian Archean shield. Only a few scattered masses of sediments remain on its

Jan 1, 1935

By James A. West

COUNTRIES of the Near East, with the world's largest and insist prolific petroleum resources, produced nearly 277 percent of the world's estimated total output of crude& oil in 1964 and accounted for about 60 percent of world exports of this commodity. Although petroleum largely dominated the mineral industry of tine area, production of antimony, chromium, copper, mercury, boron, potash, and phosphate rock was of world significance. Production of crude oil in Near East countries reached a record high of 7,520,000 barrels per day in 1964, an increase of nearly 11 percent over that of 1963. Kuwait maintained its position as the leading producer, accounting for almost 28 percent of the area's output. Saudi Arabia, Iran, and Iraq followed with 22.5, 22.2, and 16.5 percent of total area output, respectively. Despite record production, the Near East, proved crude oil reserve remained in excess of 211 billion barrels, or more than two-thirds of the estimated world proved crude oil reserve.

Jan 1, 1966

By E. Maltby Shipp

YouR committee's secretary submits the following report, or summary, to the members of the committee, in an endeavor to lay before them a general review of the information so far received and also his own knowledge of the work as carried on at a number of plants, this being done in part to secure further information and suggestions from members and lead to a more effective means of furthering the work of the committee. It is suggested that more detailed data be compiled regarding engineering features involved, and that papers be contributed which will deal with the safeguarding of underground electrical installations. There are few operating companies which have not started a more or less systematic campaign to safeguard their employees from accidental injuries and unhealthful surroundings, but a great deal is to be gained by experience. All may welcome the advice and cooperation of those who have been actively engaged in the work and have demonstrated the results obtainable by organized effort, and it is, therefore, exceedingly gratifying to note the ready assistance and hearty cooperation rendered by the companies that may be truly termed pioneers in the movement. No solution of the safety problem is to be found in a skrict standardization of methods, rules or devices, as the various mining, milling and metallurgical practices present too many conditions differing broadly in general principles, but some standard system embodying principles already proven to be efficient should be created, which may be modified or elaborated to meet specific requirements of each individual company, or to fit working conditions as they exist in the various mining camps throughout the country. An industrial plant is primarily a business undertaking, therefore the economic side of a safety or welfare campaign is of importance. Many small operators have been deterred from undertaking the work by their belief that it involved an expense beyond their means, and one that could not be counterbalanced by greater efficiency or saving along other lines. This idea is generally due to a lack of knowledge of the actual costs of such work, and of the results secured by judicious selection of a method commensurate with the size and nature of the opera-

Jan 1, 1918

By Susan W. Campbell, Bruce Regensburg

"The CIM Careers Task Force has addressed industry's concern of a perceived shortage of skilled personnel over the coming decade. The industry is faced with a fundamental shift by young Canadians away from scientific and engineering careers, coupled with the fact that today 's students know little about the minerals industry and have a poor image of it.The responses to two questionnaires which were distributed to CIM members, government, professional associations, and educational institutions, formed the backbone of the Task Force position paper, which presents a shopping list of ideas and initiatives for consideration and to facilitation by the various organizations concerned.Tackling the image of the minerals industry is part of the answer to the careers crisis. On the positive side, the minerals industry provides the allure of a treasure hunt for young people and is seen as a significant contributor to the economy. It is understood to be well paying, provide good opportunities for advancement, individualism, and travel, and to be rich in esprit de corps. Enhancement of these positive aspects of the image can take place at all student age levels.Numerous initiatives tackle the negative aspects of the image. Young people perceive the industry to be environmentally damaging, which is the most crucial aspect that needs to be addressed. The industry is seen as still in the pick-and-shovel days and as a sunset industry that is running out of ore. Work in the minerals industry is perceived as dangerous and lacking glamour. And finally, the perceived remoteness of operations and exploration is seen as a drawback to a largely urbanized student group.Tackling young peoples' curiosity and interest in the minerals industry throughout grade school and encouraging postsecondary science and engineering students to enter the minerals industry by ensuring summer employment is the second part of the equation.The CIM Careers Task Force position paper develops strategy to attract and maintain interest of students in grade school, junior high, senior high school, and in post-secondary levels. The strategy outlines initiatives targetted at each of the educational levels and action plans to accomplish the objectives."

Jan 1, 1993

By M. M. Papic

"This paper describes the Sasol coal liquefaction process, as used in South Africa. It covers coal supply, coal gasification, gas purification, Fischer-Tropsch synthesis, the major utility systems involved and the economics of the process.IntroductionThe Sasol coal liquefaction process is based on Fischer-Tropsch synthesis of liquid fuels from carbon monoxide and hydrogen, which are in turn obtained by gasification of coal with steam and oxygen. The process is shown schematically in Figure I.The first step in the process is coal preparation, in which the coal is crushed and screened to a 3-50 mm size for gasification on one side and to -3 mm size for steam and power production on the other. Oxygen needed for coal gasificatoin is produced in the air separation plant.Coal is gasified under pressure by steam and oxygen in the Lurgi gasification plant, where raw, impure gas is produced . The raw gas is first washed in a scrubber with a circulating gas liquor, heat is then recovered from it in a waste heat recovery boiler and the gas is further cooled for purification. Water-insoluble materials (tar oils) in the gas liquor are separated from aqueous solution and sent to tar refining for the recovery of tar products. The aqueous portion of the gas liquor goes to a Phenosolvan solvent extraction process, where phenols and ammonia are recovered. Water then proceeds to the effluent treatment plant.The scrubbed and cooled raw gas goes to a Rectisol gas purification plant, where all components other than hydrogen, carbon monoxide and methane are removed as completely as possible by absorption in refrigerated methanol. The acid gases (CO2, H2S) stripped from the methanol in the Rectisol unit are processed in a Stretford plant for recovery of sulphur. Regenerated methanol is returned to the process. The purified synthesis gas is passed to the fluidized-bed Synthol reactors, where Fischer-Tropsch synthesis reactions take place.The synthesis products are recovered in a product recovery unit as separate streams of decant oil containing higher-molecular- weight hydrocarbons, light oil comprised of lower-molecular- weight species, the aqueous stream containing water solubles, a C3/C4 stream, a C2 stream , a methane stream and a hydrogen-rich stream. Most of the hydrogen is recycled to the Synthol reactors; a major portion of the methane is reformed to hydrogen and carbon monoxide for recycle; the C2 fraction goes to an ethylene plant; and liquid streams proceed to the product refinery.The product refinery is used to upgrade and purify the Synthol products to specification fuels and chemicals.Sasol l, the first coal liquefaction plant in South Africa , was built in 1955. It is still operating and has a product output of about half a million tonnes per year. The Sasol II plant is in a commissioning stage and will be in full operation in 1981. It is about five times the size of Sasoll. It uses over 12 million tonnes of coal and produces more than 2 million tonnes of saleable products annually (1,2,3). The Sasol llI plant, which is a mirror image of Sasol II, is under construction and scheduled for completion in 1983."

Jan 1, 1981

By Andrew Hickinbotham

"A water well represents not only a significant investment but also is a key to making a living or sustaining a reasonable lifestyle. This naturally makes the water well a precious possession that needsto be protected.This paper describes the challenges that TransAlta Utilities Corporation faced and how it responded to the concern of residents that open pit coal mining would affect their water well supplies.BackgroundWells have a certain mystique. Tum on the silver tap and water flows at your command without you knowing how it got there and whether it will continue to flow.Each well is different and has a story to tell. Some wells have a lot of history and are described fondly and with pride (""Grandad built this place 50 years ago and she hasn't failed us yet""). Some are passed on from father to son, some are part of the pride of good farming, some wells are famous for tapping that huge underground stream or have been mysteriously witched or have been part of a rip-off by an unscrupulous well driller. Some have to be babied so that the cows can be watered, the children can have showers and the dishes can be done. All wells represent a significant $5,000 to $10,000 investment and is a key to making a living or sustaining a reasonable lifestyle.Most wells continue to provide water faithfully - until there is a problem. For those people living next to a mine, there is the additional concern that mining has or will affect their water well supplies. Water well problems reported to the mining company have to be dealt with promptly and responsibly. The mining company's groundwater specialist must gain the trust and confidence of well owners living in the area ."

Jan 1, 1992

By F. J. Schuh

The drilling industry long has been plagued by failures in the bottom few joints of surface and intermediate casing strings. This paper presents an analysis of the various possible causes of failure and concludes that failures are caused by short-lived, high-energy torque impulses delivered from the drill string through the bit while drilling out the cementing plugs, cement and floating equipment. The magnitude of these torque impulses is shown to be a function of the rotational momentum of the drill string, and a method is derived to calculate the magnitude of these impulses. The available methods of strengthening the bottom joints are reviewed. It is concluded that, while present methods are ineffective, a combination of improved procedures for strengthening and minor restrictions on drillout practices will prevent failures. Introduction In most cases, failure in the bottom few joints of casing strings is not discovered until electric logs record that the bottom one, two or three joints have parted from the casing string and slipped down the hole. However, in some cases the parted section of casing uncovers a high-pressure or lost circulation zone, or shifts laterally restricting the passage of drilling equipment. In these instances extensive remedial work is required to realign the parted pieces and seal the exposed formations. Several methods used to strengthen the bottom joints of casing strings include locking set screws in the couplings, putting wedges in special collars, welding straps across the couplings, welding the couplings and, most recently, using epoxy resin-based, thread-locking compounds. Since none of these techniques has eliminated the problem, this study was initiated to find the cause of failures and to evaluate the available methods of prevention. Mechanics of Casing Failures An analysis of the various possible causes of failure indicates that the casing is unscrewed rather than broken and that therefore failure must occur before the shoe is drilled. Since there is no general agreement as to the causes of casing failure, some possible mechanisms were ATLANTIC RICHFIELD CO. DALLAS, TEX. considered in this analysis. Failure of the bottom joints of casing can occur by only one of three types of stress: tension, torsion or bending. The possible mechanisms of failure were evaluated by determining the forces required to cause casing failure by each of the stresses; and, where applicable, the possibility of failure by fatigue was considered. For casing to part under tension requires a downward load of more than the tensile strength of the casing. The lightest API weight H-40 grade casing requires a bit load on the bottom of the casing of 27,000 to 34,000 Ib per inch of bit diameter (Table 1). Since maximum drill collar weights seldom exceed 10,000 Ib per inch of bit diameter, it is apparent that casing strings cannot be parted by the downward load of the drill string. The second mechanism considered was failure by bending. This mechanism requires that the lowermost casing joints be free to be deflected laterally until the bending stress exceeds the strength of the pipe. To fail, the casing (at a height L above the shoe) requires a force and deflection' at the shoe of To deflect the casing shoe with the drill string obviously requires a dog-leg at the casing shoe. This dog-leg must have a rate of change equal to or greater than the change in curvature of the deflected casing, which is given by

Jan 1, 1969

By Neil Schofield

"The estimation of recoverable ore reserves for feasibility in precious metal deposits such as Pine Creek must account not only f or the extreme variability of the ore grade but also for the complexity of the geology. Compatible models f or both must be adopted. Further, very selective mining demands reserve estimates be based on small selection units whose individual grades cannot be estimated reliably from the exploration drilling data.Multigaussian kriging is one method based on a multivariate normal model for estimating recoverable reserves under such conditions. In this paper, a non-mathematical description of the multigaussian model is presented together with its application to the Pine Creek Gold Deposit. The results, when compared to the first year of production, are encouraging for the model but not without surprises.Together, Part 1 and Part 2 of this study combine a detailed and geologically conditioned variogram analysis with an appropriate estimation method for a highly variable low-grade gold deposit. This and other studies of gold deposits familiar to the author show convincingly both that while the appropriate geostatistical skills and techniques are necessary to tackle the question of reserves, equally important but often discounted is the need for an appropriate and compatible geological model. IntroductionThe Pine Creek gold mineralization is associated with saddle reefs, and quartz and quartz- sulphide veining within the Enterprise Anti cline. The anticlinal structure is complex and, prior to mining, the mineralization was considered to be mainly strata controlled. Grades vary up to 160 grams in l .5rn core samples with coefficients of variation in excess of three.The estimation of the recoverable reserves for such a depo sit must account for both the geological complexity and the extreme variability of the gold grade.Part 1 of this work presented the geological model for the deposit and summary statistics 0 f the gold data. A detailed structural and variogram analysis considered both gold grades and the normal score (or gaussian transform) of these gold grades for different composite sizes."

Jan 1, 1988

By J. C. O'Rourke

"Gibraltar Mines Ltd. has been operating its open pit copper mine for fifteen years. In that time, over 140 million tons of waste and low-grade material has been placed on the mine waste dumps. Laboratory and in situ testing indicated that enough leachable copper was recoverable from the dumps to justify a leaching operation which would include the construction of a solvent extraction-electro winning plant. The plant, which was commissioned in October 1986, was designed to process 3000 USGPM of dilute copper solution to produce 5000 tons per year of high-quality cathode copper.This paper deals with the start-up and initial year of operation of this plant. The three areas: leaching, solvent extraction, and electrowinning are presented with emphasis on the innovations which were made to help overcome the problems unique to the Gibraltar operation.The Leaching CircuitThe mine waste dumps are leached to produce a pregnant copper solution as feed to the SX-EW plant. To achieve this the dumps are sprinkled with a mildly acidic solution which percolates through the dumps. In travelling through the dumps the solution contacts the surfaces of the liberated copper minerals and dissolves the soluble copper into the form of copper sulphate. The leaching reaction is achieved by a combination of bacterial action to oxidize the sulphides and solubilization of the copper into the acid solution.For the bacterial action to occur the dumps must be near the ideal pH of 1.9 to 2.1 and the necessary elements of the reaction must be present. Because a bacterial reaction is involved there is a lag time between the time when the conditions for bacterial growth are achieved and when the bacteria are in their active growth phase. Laboratory leaching tests with Gibraltar ore indicated that bacterial action takes two to three months to reach its maximum rate (Fig. I).The expected lag time for the planned rate of bacterial leaching prompted Gibraltar to start irrigating the dumps in late June 1986 for a plant start in early fall. The lag time proved to be longer than expected and the dumps took until November to start producing copper at the expected rate (Fig. 2)."

Jan 1, 1988

By J S. Petersen

The occurrence of coarse gold particles leading to grade complexity and sampling challenges is a common feature of many gold deposits. Poorly designed sampling protocols applied to these deposit types can lead to an excessively high fundamental sampling error. Together with other errors, the fundamental sampling error contributes to the nugget effect. Proper sample collection, preparation and assay protocols are required to minimise this error, and hence reduce the total nugget effect. Reduction of the nugget effect is a key requirement for subsequent geostatistical resource estimates to be effective. A case study from the Nalunaq gold mine in Greenland is presented, which is characterised by notable quantities of coarse gold (>30 per cent +100 ¦m gold) hosted in quartz veins. Diamond drilling provides a good measure of gross geological continuity at practical grid spacings, but is not considered to represent the mineralisation effectively. On-reef development with face and bulk sampling, together with detailed geological studies were undertaken during the resource delineation phase. This contribution describes the nature of the Nalunaq deposit, its gold particle size characteristics, how sampling and assay protocols were developed (including QA/QC issues), application of GyÆs sampling theory and its calibration, and how the data was subsequently applied to grade estimation.

Jan 1, 2005

By Charles L. Kimbell

The estimated value of world crude mineral production in 1990 exceeded $1,501.5 billion in terms of current (1990) dollars, or almost $1,160 billion in terms of constant 1983 dollars. This latter figure was 0.3% below the 1989 level and about 3.9% below the record high to date of $1,207.1 billion 1983 dollars set in 1980. Table 1 provides the latest available revised time series of the estimated value of world crude mineral production both in terms of 1983 constant dollars and in terms of current dollars. It also provides one of the two statistical bases for this estimation, this being the data on the value of production of a group of key commodities that was compiled for and published in the authoritative French language mineral industry periodical, Annales des Mines, for selected years up to 1983.1 It should be stressed that the values just discussed and those presented in the tabulation are for crude minerals only, and by no means reflect adequately the role of the entire mineral industry in the world economy. These figures represent only the value of mineral materials as they are mined or otherwise extracted from the earth. They do not reflect the value added to these materials through downstream processing within the facilities commonly accepted as mineral industry plants. That is, value added through beneficiation of ores, smelting, refining, and similar processing is not included in these figures. Comprehensive world data on the value added by such processing are not available; however, a conservative estimate of the total value of pro-cessed output from mineral industry plants derived wholly from primary (newly mined) materials would be on the order of about $2,780 billion constant 1983 dollars or $3,600 billion in terms of 1990 dollars.

Jan 1, 1993

By G. J. Desroches

"In order to improve zinc plant productivity, areas of low efficiency were identified. As a result, solution purification was improved, additional dust precipitator capacity was made available and a new zinc casting plant was installed. The effects of these and other changes are discussed and the expenditure and benefits reviewed. HistoryThe operation of the Flin Flon metallurgical complex including an electrolytic zinc plant commenced in October 1930. The design of the zinc plant was based on that of the Commonwealth Mining and Smelting Company at Trail, British Columbia, the Anaconda Great Falls Montana Plant and the Electrolytic Zinc Company plant at Risdon, Tasmania.The plant began with a design capacity of 60 tons per day and currently produces 255 tons per day. Since plant start-up, approximately 3.5 million ton s of zinc metal have been produced, most of it exceeding special high-grade specifications.IntroductionThe facility incorporates the basic process steps of roasting, leaching, purification, electrowinning and casting. Figure I details the flowsheet. During the late 1970s, management recognized that in order for the zinc plant to continue operating, it was necessary to introduce cost-effective practices.Study groups, consisting of design engineers and operations personnel, were formed to investigate the details of plant revisions.The objectives were to improve productivity by reducing manual labour, reducing energy usage, increasing zinc recovery, increasing metal output and reducing costs.This paper details the changes made during the period 1979to 1986 and shows how these changes have affected the productivity and economics of the zinc plant operation."

Jan 1, 1988

By J. M. Hodge

This paper represents a start on the problem of choosing alloy steels for a given application on the basis of toughness as indicated by the room temperature notched bar impact value at the desired hardness level, and as such, is very useful. I believe, however, that the authors will agree that it is only a start on this problem. The authors state that neglecting temper brittleness or other possible effects of the tempering temperature level, the impact values at a given grain size level will be determined principally by the hardenability. This is, of course, true inasmuch as the hardenability determines the microstructure, but it serves to emphasize the broad field that hardenability now covers, since this study apparently includes mi¬crostructures ranging from full martensite to coarse pearlite. Furthermore, the + or - 20 ft-lb spread in the correlation with hardenability, which certainly limits the usefulness of these results for many applications, indubitably reflects the wide range of microstructures corresponding to a given value of hardenability in terms of the difference between full martensite and asquenched hardness.

Jan 1, 1947

By Henry S. Rawdon

The relation between the course, or path, of the fracture of metals and alloys, produced in service or as a result of certain laboratory tests, and the crystalline units of which such materials are composed is of utmost importance. The fracture of normal material is, in general, intracrystalline, i.e., it consists of a break across the grains rather than of a separation between them. An interorystalline fracture indicates either that the metal is of very inferior quality or that the break occurred under very unusual conditions, e.g., at a very high temperature. The usual mechanical tests, when applied to metals of the type that breaks with an intercrystalline fracture, merely measure the coherence of adjacent grains for one another and reveal little as to the real properties of the metal itself. Even such a soft plastic substance as lead, under suitable conditions, may be rendered so weak and brittle that the metal can be easily crumbled into powder by the fingers although the constituent grains have lost none of the intrinsic properties of lead. Various erroneous explanations of this behavior of lead have appeared in the scientific literature, the change being described usually as an allotropic one. The importance, in an industrial sense, of a proper explanation of this type of the corrosion of lead justifies the description of the type of metal deterioration that follows. Corroded Lead Sheathing In Figs. 1 and 2 are shown two typical specimens of corroded lead sheathing selected from materials submitted to the Bureau of Standards for examination. Fig; 1 shows a section of the sheathing of an aerial cable; Fig. 2, that of the lead covering of a subterranean feeder-line of an electric light system. In this case the deterioration had proceeded to a much great'er extent than in the case shown in Fig. 1 so that certain portions of the metal could easily be crumbled into a coarse gray powder by the fingers. This was particularly true of those portions of the sheathing

Jan 1, 1921

By L. F. Mondolfo, B. E. Sundquist

The crystallographic orientation relationships resulting when lead is nucleated from the liquid by Ni, Cu, Ag, and Ge were determined. For each nucleating agent several definite orientatioz relationships were found. These relationships seemed to be controlled by good symmetry relations and low crystallographic disregistry between mating planes. For any given nucleating agent the under colling for nucleation was found fairly constant and independent of the orientation relationship and consequent disregistry. It was also found that, upon re melting and refreezing the Pb, the orientation relationship was changed. These findings prove that crystallographic disregistry is not the controlling factor in heterogeneous nucleation from the liquid. The results of this investigation tend to confirm the theory presented in a preceding paper that heterogeneous nucleation starts with the formation of an adsorbed layer of nucleated metal on the nucleat-ing impurity. Evidence is given that cavities in the nucleating agent act as centers of nucleation. IT has long been known' that solid extraneous particles are active in catalyzing phase transformations that occur in a system, particularly condensation and crystallization. It is well established that these heterogeneities act as catalysts by providing surfaces upon which nuclei of the precipitating phase can form with activation energies smaller than those required for homogeneous nucleation. Numerous investigations have shown that in this process of heterogeneous nucleation: a) the nucleus forms with one, or several, definite crystallographic orientation relationships with the nucleating phase2-4 and b) that there is a small range of undercoolings or super saturations characteristic of the nucleation of a given solid on a given Substrate.5-10 Turnbull and vonnegut11 have developed a theory based on theories developed by Volmer12 and Turn-bull and Fisher1= for heterogeneous nucleation from gases and liquids, that relates the super saturation or undercooling required for nucleation to the dis-registry between the lattices of the nucleus and the nucleating agent. This theory predicts that nucleation should occur with the orientation relationship between the nucleus and nucleating agent that minimizes the disregistry. Further, it predicts that the undercooling or super saturation necessary for nucleation should be a function of the disregistry. Numerous investigations have dealt with the orientation relationships resulting from the condensation of vapors onto crystalline solid substrates2,3 and a few with the nucleation of one phase by a second phase in solidification4,14. Others have dealt with the supersaturation8-10 and undercooling5-7 associated with nucleation in condensation and solidification respectively. However, there is virtually no report that gives both of these factors for the same system. In this investigation a study was made of the undercoolings and orientation relationships resulting when Pb is nucleated from the liquid by Ni, Cu, Ag, and Ge. It was the purpose of this investigation to check the Turnbull-Vonnegut theory, i.e., the importance of crystallographic disregistry between nucleating catalyst and nucleated metal. The results indicate that disregistry is not an important factor in nucleation and that the nucleation process is probably somewhat more complex than current theories suggest. EXPERMENTAL PROCEDURE Small single crystals of nickel, copper, silver, and germanium were prepared from materials of four to five nines purity, and the Pb used was also 99.999+ pet pure. Cu and Ag single crystals were prepared by sealing small chips of Cu or Ag in an evacuated quartz capsule and heating the capsule at 2000°F for 1 hr before cooling. Nickel crystals of 200 diam were also prepared in evacuated quartz capsules, but melting was done by heating the capsules in an oxy-acetylene flame for a few minutes. These spheres were invariably polycrystalline so

Jan 1, 1962

By F. M. d’Heurle

Films of molybdenum have been prepared by sputtering onto oxidized silicon substrates. The resistivity. lattice parameter, orientation, and grain size were studied as a function of substrate temperature and substrate bias. Under normal sputtering conditions, the resistivity of the films was found to be quite high (600 x 10 ohm-crn). However, with the use of the negative substrate bias of 100 v and a substrate temperature of 350°C, films weve produced with a resistivity of ahout twice that of bulk molybdenum. The lattice parameters measured in a direction nornzal to the surface of the films weve found to be gveatev than the bulk value. This was interpreted as being at least partly due to the presence of compressive stresses. The effects of annealing in an Ar-H atmosphere were studied in terms of diffraction line width, lattice parameter, and resistivity. BECAUSE of its relatively low bulk resistivity (5.6 x 106 ohm-cm)' molybdenum is potentially interesting as a thin-film conductor in integrated circuits. An additional feature which makes it attractive for this purpose is its low coefficient of expansion (5.6 x KT6 per "c),' which is fairly well matched to that of silicon (3.2 x 10 per c). It is possible to deposit molybdenum films by evaporation but generally films produced in this manner have a high resistivity. In order to achieve resistivities close to bulk value, Holmwood and Glang found it necessary to operate in a vacuum of about 107 Torr and to maintain the substrates at 600 C during film deposition. Sputtered molybdenum films have been examined by Belser et a1.7 and, recently, by Glang et al.' This paper describes the results of an attempt to extend some of that work and examine the effects of annealing and getter sputtering on the physical and structural properties of the films produced. SPUTTERING APPARATUS AND PROCEDURE The apparatus used for most of the film sputtering work described here consisted of two "fingers" serving as anode and cathode, respectively, which were mounted within an 18-in.-diam glass chamber. A liquid nitrogen-trapped 6-in. diffusion-pump system was used to achieve a vacuum of about 1 x 107 Torr within the chamber prior to sputtering. The essential features of the equipment are shown in Fig. 1. Cathode and anode fingers are stainless-steel tubes isolated from the top and bottom plates by Teflon collars. In order to limit the discharge to the space between anode and cathode, each finger is surrounded by an aluminum hield, at ground potential, having an internal diameter 18 in. larger than the outside diameter of the finger. The cathode and anode fingers are 6 and 4 in. in diam, respectively. A 116-in.-thick sheet of molybdenum is brazed with a 10 pct Pd, 58 pct Ag, 32 pct Cu alloy to a copper disc which is mounted by means of screws and a large 0 ring onto the lower end of the cathode finger. The disc is cooled during sputtering by water circulation inside the finger. The use of several feet of plastic tubing for the water input and outputg reduces leakage to ground to less than 1 ma when the cathode potential is raised to 5 kv. The upper end of the anode finger is terminated by a brazed-on copper block. A variety of specimen holders can be easily mounted on the upper face of this block. Substrate heating or cooling is achieved by use of an appropriate unit attached to the lower face of the same block. Heating is achieved by means of cartridge-type heaters and cooling by copper coils fed with forming gas under pressure. The inner chamber of the specimen finger constitutes a small vacuum chamber of its own which is evacuated by an auxiliary mechanical pump in order to limit heating element oxidation and heat transfer by convection currents. An advantage of the finger arrangement is the absence of cooling and heating coils and wires within the main chamber. The stain less-steel shutter is useful to establish a discharge for cleaning the cathode at the beginning of each sputtering run. Water cooling of the shutter reduces heating and the out-gassing of impurities which might condense on the nearby substrates. Unless otherwise specified, the substrates used in these experiments were 1-in.-diam oxidized silicon wafe:s, 0.007 in. thick, having an oxide thickness of 6000A. The substrate holders were large copper discs onto the surface of which a number of molybdenum discs, 116 in. thick and 78 in. in diam, were brazed. The wafers were clamped to the molybdenum discs

Jan 1, 1967