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By S. Dallaire

"RÉSUMÉLes revêtements céramiques ont une moins grande visibilité que les revêtements métallurgiques. Ils ont cependant jour un role significatif dans noire développement technologique. Les procédés de revêtement ont permis de s'affranchir de barrières technologiques importantes dans le domaine de l'optique, de l'électronique, de l'usure, des hautes temperatures. L'introduction de nouvelles technologies ou la mise en service de nouveaux matériaux peut nécessiter l'adaptation de certain procédés actuels ou le recours a des procédés qui ont peu percé jusqu’ à maintenant.ABSTRACTApplications concerned with ceramic coatings are not as well known as those with metallic coatings. However, ceramic coatings have played a tremendous role in the development of technology. Ceramic coating processes made it possible to overcome technological barriers in the areas of optics, electronics, wear resistance and high temperature applications. Ceramic coatings can provide new properties to materials never considered for demanding applications. They can also open new frontiers and revitalize materials which are maturing or in decline."

Jan 1, 1990

By R. H. Sweetser

There are so many conditions affecting blast-furnace results that it is hard to get satisfactory comparative data on the working of two furnaces, and much more difficult to get comparable results from the use of two entirely different fuels. The several advantages of charcoal over coke as a blast-furnace fuel have doubtless been apparent to many managers; but probably the conditions for comparative tests of the two were never so favorable as during the year 1905, at the works of the Algoma Steel Co., Sault Ste. Marie, Ontario, which comprise two modern blast-furnaces, well equipped, though of comparat.ively small capacity. For four consecutive months one of these furnaces was run with charcoal and the other with coke. Then the charcoal-furnace ran for a while with part charcoal and part coke; and, still later, with coke only. The ore-mixtures were

Jan 1, 1909

By Sam Tour

Some years ago, the writer described heat checks or thermal cracks that occur in die-casting dies.' The life of dies was considered in relation to. the casting temperature, the material used for the die and the heat to be absorbed by the die per unit volume of casting made. The mechanism of the action that results in thermal failure of dies was described. In the present paper the writer proposes to describe some additional observations in regard to heat checking, make one or two suggestions as to the method or methods for further attack of the problem, and give the results obtained on some work carried out along these lines. Importance of Heat Checking Heat checks in steel are the source of trouble in many industries besides that of die casting. Every shop where metals are subjected to hot working is searching for improvement and hoping for a cure. The development of a material of sufficient strength to be used as a die and yet devoid of the property of heat checking would be a godsend to many shops and many industries. The need for thorough study and research on the subject is evidenced by the wide variety of hot-working die steels on the market. It is peculiar, but true, that in practically every case the maker of the steel can give concrete evidence to prove his contention that his type of hot-working die steel is as good as or better than any other. A number of steel companies have several hot-working die steels from which choice can be made to fit a particular set of requirements. Possibly to expect one material to be universally the best hot-working die steel is unreasonable. In some hot-working operations, as in drop forging, the die must have great toughness to withstand the stresses developed; in other operations, as in hot piercing or punching, resistance to erosion at high temperatures, possibly defined as strength and hardness at elevated temperatures, is required. In still others, as in die casting, only sufficient hardness to resist scoring between moving surfaces is required, whereas the resistance to sudden changes in temperature must be at a maximum.

Jan 1, 1935

By Robert L. Gamble

The world's largest fluidized bed steam generator located at Rivesville, West Virginia is currently undergoing initial operation. This unit is designed to generate 3708 kg/s (300,000 Ib/hr) equivalent to 30 MWe of superheated steam while firing coal in a fluidized bed of limestone. Coal was first fired in this unit in December, 1976 and start up operation is progressing.

Jan 1, 1977

IN international affairs, the great event of June was the meeting of representative bankers at Paris -for consideration of the arrangement of a large loan to Germany. The conference dissolved in futility. Following this abortive conference, the delegates to the parley at the Hague assembled there on June 15. America is not represented at the Hague, any more than at Genoa. The British view the conference seriously and have Leslie Urquhart, the highest authority on Russia, attending in an official capacity. The Irish had their election and voted by strong majority in favor of the treaty with Great Britain, which was happy, but the general situation in Ireland is miserable. In China there were spectacular military and political events. Economically, Japan was in trouble. Conditions are becoming better in India, although no yet settled. Egypt has troubles still. Australia has a better chance for welfare, following the overthrow of its labor govern-ment early in April last. In Europe it is hard to discern any improvement except in Great Britain. Business in Great Britain has been slowly widening. The future of Great Britain, which is chiefly an in-dustrial country, depends on finding employment for its, 1,750,000 idle men. Personalities figured largely in June. Lenin's health was represented as having failed so that the govern-ment of Russia has had to be-turned over to a trium-virate. All of this has been denied. It is clear that some. mighty events are transpiring there. The assassination of Doctor Rathenau in Germany is probably also an occurrence of portent. The murder of Field Marshal Wilson, in London, tended to in-crease anger in England against the Irish. In the United. States the attention of Congress was concentrated on the soldier bonus, the tariff bill and the subsidy for shipping. All of these projects are economically bad and are of the same nature, viz., the allotment of a bounty to some classes of people, without consideration to the general national interest and welfare.

Jan 7, 1922

By W. T. Abel

The Bureau of Mines tested 48 materials for their ability to absorb H2S from hot simulated producer gas (1,000°-1,500° F). The material found best from the standpoint of absorption capacity, durability, and amenability to regeneration was sintered pellets of 75 percent fly ash-25 percent Fe203. The performance of this absorbent under simulated and actual conditions is described. The effect of absorbent composition, absorbent temperature, steam content of the gas, and tar vapors and dust in producer gas is discussed.

Jan 1, 1974

By A. E. Bellis, T. W. Hardy

The problem of heat treating high-speed steel becomes more and more important as the design of cutters becomes more and more complicated in increasing the efficiency of mechanical operatioqs. Hundreds of dollars are spent in the design and manufacture of milling cutters of special form for rapid production of duplicate or interchangeable parts, and then, as the heat treatment is faulty on the one hand, or scientifically executed on the other, the tool fails after a few operations, or its efficiency is greatly increased. The practical operation of giving these complicated tools the right temperature necessary to bring out the best cutting qualities, and at the same time bring-the tool out "clean," is a difficult one and calls for no small amount of skill. In order to be on the safe side the average tool hardener uses a temperature much too low to give the best results with the high-speed steel he uses. In the case of cutters which are finished to a given diameter before hardening, it is impossible to grind the tool after hardening, so that it is essential that the surface be protected from oxidizing or de-carbonizing. It is the aim of this paper to describe some experiments on hardening high-speed stee1, in which metallographic means were used to determine the correct hardening tempcratures. The accompanying table and plates show the results of hardening experiments on five different high-speed steels. The analyses for carbon, tungsten, chromium and vanadium of each steel are given in the accom- . panying table. Six specimens from the same bar of each kind of steel

Jan 1, 1917

If you are to be and remain competitive in the mining industry, it is vital that your company management systems are efficient. An integral part of today's competition in a ruthless market is to keep internal costs to a minimum. Integrating our core and parallel management systems is becoming an essential strategy to ensure efficiencies are maintained to the highest level, allowing the maximisation of profits, and to maintain that leadership status within our industry. The uniquely designed Integrated Management Process provides the path to develop, implement, and monitor an Integrated Management System in a simple but highly efficient and effective manner.

Jan 1, 1997

Up to 19 chemical parameters were studied in flotation pulps in six Australian lead-zinc concentrators with the aim of obtaining a better understanding of the nature of, and changes in, the chemical environment. This paperdiscusses collector residuals, metal concentrations in solution, and other parameters.Collectors used in the plants studied were various xanthates, Z-200, and Aerofloats. Xanthate residuals varied in different ways in most plants. However the general trend was for residuals to be at the O· 5-2 p.p.m. level in lead flotation and O· 5 p.p.m. or less in zinc flotation.Aerofloat residuals were also variable but in the plant concerned were at a much higher level (8-10 p.p.m.) than xanthate residuals. Z-200 residuals were in the 10-20 p.p.m. range and it was found that the Z-200 added to zinc flotation was reporting in dam return water and entering lead flotation.Copper concentrations in solution were negligibly low in those plants where cyanide was not used. When cyanide was used, copper was at the 5-20 p.p.m. level and appeared to be present as Cu(CN)-2. However the hiocyanatepresent may be important. Xanthate was also present in these solutions.Zinc concentrations ranged from 0·1 to 800 p.p.m. in different plants. The general trend was for the zinc level to be highest in the grinding circuit and to drop during flotation. However there was always an increase in zinc concentration when copper sulphate was added, even tho.ugh this incre.ase was not permanent, and the increase was greater with higher copper sulphate additions.The manganese concentration also increased appreciably during copper-activation of marmatite. In some plants lead concentrations increased from 0·1 to 1 p.p.m. during activation of marmatite.Calcium concentrations (20-1200 p.p.m.) and magnesium concentrations (10-600 p.p.m.) tended to be fairly stable in each circuit.

Jan 1, 1970

By Ben V. Petersen

Surveying is to tunneling, as a steering wheel is to a car—somewhat essential if you want to end up in the right place. The principles of tunnel surveying have remained unchanged since the first tunnels were constructed: To mathematically connect the selected start and end points of a tunnel and physically translate that alignment onto the ground. The alternative is just dead-reckoning and leaves the probably less than satisfying end results to chance. Today’s laser-guided tunnels often have to thread the needle through a maze of soil types, utilities, structural features and other underground considerations. Surveying makes it possible.

Jan 1, 2005

By B. Wasmund, M. Parravani, M. Jastrzebski, Z. Coull

"One of the main drivers of overall profitability of pyrometallurgical vessels is refractory lining campaign life. Increased economic pressure to improve vessel life requires innovative solutions to the problem of refractory cooling. Hatch has recently developed a high-intensity, waterless cooling system that bridges the performance gap between external shell cooling and internal water-cooled copper elements. External shell cooling has a limited effectiveness in protecting the refractory lining, because it is thermally insulated from the hotface of the lining by its thickness. This situation does not improve until the lining itself has become worn near the end of the campaign. The patented technology developed by Hatch overcomes this problem by positioning high-velocity air-cooling channels within the lining, closer to the hotface where the cooling benefits can be realized throughout the entire duration of the campaign. The current paper presents the development and application of Internal Air Cooling technology as well as results from the pilot campaign in an operating commercial vessel. Various adaptations for this novel, cost-effective and inherently safe system are also discussed."

Jan 1, 2015

By J. D. McBeth, G. M. Potter, Ramon Pizarro

Heap leaching is used by the Carlin Gold Mining Co., Carlin, Nev., to supplement conventional processing of gold ore by agitation-leaching and countercurrent decantation. Selected open-pit ore containing about 0.072 oz Au per ton is crushed to 3/4 inch, dumped by truck on an asphalt pad, and leached by sprinkling with dilute cyanide solution for 7 days. The heap is then drained and removed by front-end loader to tailings disposal. About 70 percent of the gold is dissolved. Leach solution from the heap joins the pregnant solution from countercurrent decantation for gold recovery by zinc precipitation. Four leach pads, each with a capacity of 1,400 tons of ore, are in use. About 10,000 tons of ore are heap leached monthly from about April through October. Heap leaching is recessed during freezing weather. Labor, equipment, and reagent requirements for heap leaching are presented.

Jan 1, 1974

E. S. BARDWELL,* Great Falls, Mont. (written discussion ?).-There are several points in. connection with the manufacture of ferromanganese in the electric furnace which it seems to me. might prove of interest in this connection. Recent observation of a, number of electric furnaces varying considerably in size and transformer capacity, and all working under the same conditions, shows the small furnaces to be much more efficient in operation than the large furnaces. The furnaces examined were all of the same type. The crucibles consisted of tanks varying in size from 71-z by 15 ft. by 4 ft. deep, to 12 by 20 ft. by 9 ft. deep, with linings formed of carbon electrode butts. The smaller furnaces had transformer capacity rated at 1500 k.v.a.; the largest furnace had a transformer rated at 3000 k.v.a. All of the furnaces were operated on three-phase, 60-cycle current, the three electrodes being in a straight line. The voltages varied from 65 volts in the smaller to 100 volts in the larger furnaces. The charges consisted of manganese ore, coal, iron turnings, and limestone in proper proportions. The small furnaces, operating at low voltage, were making good recoveries. The slag loss was low and the volatilization loss almost nil. The larger furnaces, operating at higher voltages, showed increased loss of manganese in the slag and greatly increased volatilization loss when working on the same charges as the smaller furnaces, or on charges similarly calculated. The exact reasons for this state of affairs are difficult to state; a number of factors probably contribute to the results obtained in the large furnaces. First as to the effect of the higher voltage on manganese content of the slags. Increasing the voltage of the furnaces apparently tends to promote irregular working. The current takes the path of least resistance; this means superheating in certain areas in the crucible and insufficiently high temperatures in adjoining areas. The partially reduced manganese in the cooler areas passes into the slag and escapes further reduction.

Jan 11, 1918

By C. J. Tonkin

Compressed air is widely used on South African gold mines. However, due to recent and proposed future electricity tariff increases it is quickly becoming too expensive to produce and use. Boxfront chute systems at ore passes were focused on during this study, and a number of alternative power sources were examined. After comparing primarily costs, and secondarily safety and practicality, of a number of systems based on water and hydraulic oil, a system making use of either air or water was determined to be the most cost effective. A payback time of 8 years was calculated, which will be significantly less taking into account the avoidance of failures due to electricity and water shortages, which would not affect this system due to its ability to swap between either air or water. It was recommended that this system be installed at all boxfront chutes as soon as possible so that the company can begin to benefit from the cost savings.

Jan 1, 2013

By B. M. Currell, M. J. Neate, P. W. Bowden

Historically the hydrogen fluoride laden fume emitted from the electrolytic cells in the aluminium reduction process is further treated in pulse jet dust collectors. These dust collectors act as dry scrubbers performing two duties: adsorbing the gaseous fluoride emitted from the cells onto alumina dust; and collecting the alumina dust minimising particulate and fluoride emissions to the environment.Patented StarBag (TM) technology has been used in aluminium smelters in Australia as a means of increasing the dust collection and fluoride scrubbing capacity of existing collectors. This technology provides an alternative to major capital equipment upgrade where increased capacity is required, and potentially lowers the production cost per tonne of aluminium where capacity limitations are being realised and production expansion is required. This paper presents the findings of on-site pilot scale, and full production scale comparative tests, highlighting the operational and variable differences observed utilising the Star-Bag(TM) technology at Boyne Smelters Ltd in Australia. The results illustrate how this technology can be utilised to increase the hydrogen fluoride scrubbing efficiency and dust collection capacity of existing capital equipment.

Jan 1, 2006

By J. David Lowell

The first part of this article is a review of industry techniques and styles during the past 50 years. It is followed by my career history during the same period. The second part covers my ideas about what works in mineral exploration. These include estimates about discovery costs, thoughts about education of explorationists, organization of exploration groups and my opinions about the relative value of exploration techniques. Evolution of exploration techniques [Table 1] shows the evolution of mineral exploration techniques and styles from 1950 to 2000. During the first half of that period, there was a progressive increase in exploration drilling. During the second half, there was a decrease in prospecting and an increase in high technology, indirect exploration and a rapid increase in discovery cost.

Jan 1, 2000

By Yan D. S

The removal of antimony from a refractory gold-bearing stibnite ore by roasting and selective chlorinating roasting was investigated. The influence of roasting temperature, roasting time, roasting atmosphere and type and amount of chlorinating agents on antimony removal were studied. The laboratory studies carried out included roasting tests of 4 g samples in a laboratory rotary kiln, followed by 400 g samples roasted in a fluidised bed. The test results revealed that antimony was efficiently removed by roasting at temperatures over 800¦C in a nitrogen atmosphere. The most efficient volatilisation of antimony was achieved with the addition of ferric chloride at temperatures between 350-600¦C.

Jan 1, 1995

By A Xenidis, N Papassiopi, I Paspaliari

Acid generating sulfidic tailings covering a surface area of approximately ten hectares have been deposited in the historic mining area of Lavrion in Greece. For the development of a remediation strategy, the performance of three alternative acid generation control techniques was assessed under actual field conditions. The techniques involved the application of dry covers, including a synthetic HDPE liner and a compacted clay layer with capillary barriers. Furthermore, the potential formation of a low permeability hardpan layer at the sulfidic tailings surface by limestone addition was investigated. The field tests covered an area of 2500 m2, which was divided in equal quadrants, corresponding to the control plot and the three alternative remedial options. To monitor the amount and quality of percolated water, lysimeters were installed beneath the four plot areas. Based on the monitoring results over a period of six years, due to the dry climate encountered in the Lavrion area, a low amount of water percolates through the pyrites if no action is taken (control area), corresponding to 20 - 25 mm per year. This water is highly acidic, pH = 1.2, and contains a heavy load of contaminants, eg Fe 40 g/L, Zn 15 g/L, and As 1.5 g/L. The HDPE cover eliminated the percolation of water into the material for a period of five years, whereas thereafter the volume of leachates increased to values similar to those recorded in the control plot. The water collected in the lysimeter of the clay cover has been minimal corresponding to approximately five per cent of the drainage volume produced in the control area. In the fourth plot, which involved limestone addition to sulfidic tailings, the volume of drainage initially collected was almost double compared to the control area. After three years of monitoring, significant reduction in the amount of percolated water was observed, attributed to the formation of a cemented layer (hardpan), at a depth of 40-80 cm from the testpad surface.

Jan 1, 2003

By Allan E. Koski

Michigan is the second largest iron ore producing state in the United States. The Empire Mine, celebrating its 30th anniversary in 1994, is the largest iron ore mine in the state. The Empire Iron Mining Partnership is an iron ore mining, concentrating and pelletizing facility managed by The Cleveland-Cliffs Iron Co., a subsidiary of Cleveland-Cliffs Inc. The Empire Mine is located near Palmer, MI on the Marquette Iron Range in Michigan's Upper Peninsula. The partnership includes Inland Steel Co., LTV Steel Co., Wheeling-Pittsburgh Steel Corp. and Cleveland-Cliffs. Mine construction began in 1960. The first pellets were produced in late 1963. Successive expansions in 1967, 1974 and 1979 resulted in Empire reaching a present annual capacity of 8.1 Mt (8 million long tons) of pellets. In late 1993, a milestone was reached with the production of Empire's 152-Mt (150-millionth long ton) of iron ore pellets.

Jan 1, 1994

By Sherwin F. Kelly

One of the most succinct and illuminating perspectives of the field of geophysical exploration to appear in recent years is an article by E. A. Eckhardt, in the magazine Geophysics for October 1949. Although his review covers the year 1948, many of the data presented are apropos to a review of 1949, and form a pertinent background for a consideration of current progress. He presents charts of the world-wide distribution of gravimeter and seismograph activity in oil exploration, which show that surveys in the United States accounted for practically 68%; of all gravity work and 80%; of all seismic activity. Canada ranked second, with a proportion of roughly 6%, in each case; South America accounted for about the same percentage of seismic work, and double that amount for gravity surveys. Within the United States, Texas and Louisiana were the scenes of the greatest activity, both claiming about 60% of all surveys by each method.

Jan 1, 1950