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By Richard Minnitt, Philippe Renard, Christina Dohm, Winfred Assibey-Bonsu, Matthew Aboagye, Julien Straubhaar, Mahlomola I. Mabala

The application of multiple point statistics (MPS) in oil studies has gained traction over the years; however, the use of MPS in mineral resource estimation and classification is still limited. This is despite MPS’ ability to deal with complex and heterogeneous geology better than the commonly applied two-point based methods. The availability and choice of a representative training image (TI) are often cited as the main challenge holding back MPS’ application in mining geostatistical studies. On the other hand, the general approach used in mining whereby early focus is on higher grade areas and lower grades are planned to be mined later presents a massive opportunity for the development of representative TIs. Mined-out areas provide large amounts of historical data that can be used to develop training images or training datasets that can be used to estimate in mining extension areas (often lower in grade), provided low grade areas are underpinned by similar geology analogue. This approach will enable more robust estimates in mine/pit extension areas for both high- and low-grade extensions than with traditional two-point geostatistical methods.

Jun 25, 2023

By A. Ballester, F. Gonzalez, M. L. Blázquez

Pyrometallurgical process are usually used to recover valuable metals from metal sulphide concentrates. However, their use is diminishing as the cost of energy rises and pollution controls become strictes. An alternative method of treatment sulphides could be bacterial leaching due its simplicity and negligible contamination (1-2). This process is presently used commercially to re cover metals such as Cu and U from low grade ore concentrates. In spite of numerous researchs during recent years (3-5) there exists very little kinetic data concerning the speed of bioleaching process. The kinetic analysis of bacterial activity is related with the metabolism and growth of microox ganisms . This fundamental information permits ma- king the best utilization of bacterial oxidation and to suggest techniques which might increase the production of the products desired. However, bio- kinetic models are especially complicated due to the existence of many metabolic routes and parallel reactions which are important for the life of the bacteria. Microbiological oxidation of a mineral substrate is influenced by its own inicial concentration: This influence can be determined by means of a kinetic study. In a medium with sufficient concentration of nutrients (nitrogen, phosphorous and potassium) and an adequate supply of 0, and CO2, as the only & L source of carbon for the biochemical synthesis, the substrate concentration would remain the only limitation in the rate of leaching. In this case the Michaelis-Menten model could be applied (6). The model is based on an association of the enzyme (El with the substrate (S) with consequent decomposition of the latter into enzyme and products [ ] The rate of dissolution is defined by the equation : [ ] Were V is the rate of metal extraction (mg 1-1 1 h-1 ) ; S is the pulp density Mn is the maximum rate for metal extraction (mg 1-1 h-1) and K is the constant of Michaelis (concentration of substrate that yields Vm/2). This method is applicable only when the rate of bacterial growth is similar to the rate of metal extraction. It would therefore be sufficient to control the concentration of metal in the medium over the period of time. In the present work a systematic study of the kinetics of ZnS and CuFeS bioleaching in sphalerite and complex ore concengrates was carried out. The rate of dissolution of the Zn and Cu as function of the pulp density and temperature was determined. However, most oxidations of sulphide dissolution take place with a very slow kinetic; but, this can be accelerated considerably by the addition to the solution of suitable catalytic ions, as was Suggested many years ago by Bjorling (7). Such ions can exercise an important influence on the rate of the oxidation-reduction reactions, both homogenous and heterogenous, which take place during the leaching of sulphides; they also affect the nature of the reaction products. The action of catalytic ions has been fully developed in aqueous systems, but in the absence of bacteria (8 - 11) although the actual machanisms is not totally known. The mechanisms proposed as hypotheses in the literature (8) indicate that, in the case of ZnS, the catalyst ion act through an electrochemical mechanism according to the reactions: [ ]

Jan 1, 1989

By James W. Martin, Robert R. Faddick

INTRODUCTION Virtually every sector of society in our country feels the impact of tunnels, either through the transportation of water, commodities, or people. The economic implications are staggering. The Committee on Rapid Excavation (1) reported that during the near future, 1968-1975, underground excavation activity will comprise 946 miles of tunnels (subways: 85 miles; underground urban highways: 123 miles; intercity highway tunnels: 210 miles; water supply tunnels: 528 miles) and 5,119 million tons of crude ore; metals: 874 million tons; nonmetals: 899 million tons; and coal: 3,346 million tons. It is estimated that the cumulative demand for underground excavation in the decade 1970-1979 will be 13 billion dollars for construction-oriented demand and 16 billion dollars for mining-oriented demand. The respective figures for the decade 1980-1989 are estimated at 22 billion dollars and 18 billion dollars. Of the many advantages claimed for tunnels (2, 3, 4, 5) the environmental considerations are becoming increasingly important. Transportation tunnels particularly for rapid transit systems, offer reductions in noise pollution and air pollution while improving aesthetics and optimizing land use (fewer problems of right-of-way and disruption of utilities). Considerable interest has been shown recently in sub-surface construction and mining (6, 7, 8). Recognizing the future demands for tunnels has led to considerable study of methods to improve rates of tunnel advance per day, safety, and the overall economics. The search for higher rates of advance has Led away from what has heap termed conventional methods (drilling

Jan 1, 1974

By A. Noble

"Froth flotation circuits are widely used throughout the mineral processing industry for the concentration of fine particles. It had been estimated that nearly 2 Gt (2.2 billion st) of ores are treated globally each year using this versatile separation process (Fuerstenau, 1999). Due to the high feed tonnage, a large economic incentive exists for flotation plant operators to optimize the performance of this critical processing circuit. Prior to the 1950s, the optimization of flotation circuits primarily involved the manual adjustment of operating variables based on visual observation and sporadic sampling (Lynch, Harbort and Nelson, 2010). During the next several decades, however, the advent of improved on-line instrumentation coupled with the rapid development of high-speed microprocessors allowed the industry to develop more advanced control systems that could quickly adjust operational parameters in response to disturbances in ore characteristics and plant flows. These early online controls typically involved feedback loops designed to stabilize cell performance through the automatic manipulation of process variables such as pulp levels, gas rates and chemical dosages. The set-points for these controllers were often set by plant operators based on one or more operator objectives, such as maximizing throughput, recovery or grade. More recently, these regulatory controllers have been interfaced with high-level data display and management systems that provide operators with the ability to better optimize flotation plant performance based on mathematical models and rule-based algorithms (Greet, 2010).While tremendous strides have been made during the past several decades, even the most modern flotation plants are still faced with the long-standing question: “What are we trying to optimize?” From an operator perspective, some common responses include “Maximize tonnage of saleable concentrate” or “Maximize metals recovery at a customer-specified market grade.” These replies may or may not reflect those of management, who often focus on economic goals such as “Maximize profits for each operational unit” or “Maximize rate of return for all corporate assets.” Unfortunately, these high-level objective statements do not always translate well into practice due to the disconnect between plant operating protocols and product value. Attempts have been made by industry to overcome this issue using various types of optimization routines such as linear programming or other optimization engines. While this approach does have some merit, these blind routines require considerable input data and interpretational expertise and provide little or no fundamental insight that can be used to drive improvements in concentrator performance."

Feb 1, 2017

By J. D. Doll

MSHA has promulgated a rule to limit the exposure of underground metal/nonmetal miners to diesel particulate matter (DPM). In May 2008, the final personal exposure limit will be lowered to 160 µg/m3 total carbon. To comply with this rule, mine operators are implementing a variety of control technologies. In this study two types of control technologies (ventilation and cabs) which are being implemented in limestone mines were investigated. Two stone mines in this study use large diameter propeller fans for main mine ventilation and direct the air to the faces using auxiliary fans, stoppings, and long pillars while bypassing the old mine workings. NIOSH measured for sub-micrometer elemental carbon (EC) using SKC DPM cassettes (analyzed using NIOSH 5040) and a near real time instrument. With the present ventilation and the number and type of vehicles used, the concentration of EC from DPM at the working areas was at or below 400 µg/m3 for both mines and about 166 µg/m3 and 251 µg/m3 at the returns. The real time data showed that the ventilation was reaching the working areas and effectively diluting the DPM. Environmental cabs were also used to reduce DPM exposures in three underground limestone mines. Using NIOSH method 5040 and near real time EC instrumentation, NIOSH sampled inside and outside of a loader cab at one of these limestone mines to determine the effectiveness of the cab. The cab was found to be over 90% effective in removing DPM as long as the cab system was properly maintained, and doors and windows were closed.

Jan 1, 2009

By Ven Mercade

The flotation of calcite has been studied by many investigators, especially in terms of type of collector; pH; and metal ions that activate and, more importantly, depress the flotation of calcite (1)(2). Research was extended to the investigation of the effect of polyvalent metal salts and sodium silicate using these materials added separately or in mixtures (3)(4)(5)(6). Flotation of calcite was also studied with respect to its function as a carrier in the beneficiation of kaolin clays by Ultraflotation (7) (8) (9). The carrier used in Engelhard Minerals & Chemicals Corporation's industrial Ultraflotation operation is calcite. This fact, coupled with the continuing interest in Ultraflotation phenomena, led to a study to determine the effect of polyvalent metal-silicate hydrosols on the flotation of calcite.

Jan 1, 1978

By Boris K. Krstev

INTRODUCTION The flotation process, in the real industrial complexes, is characterized by the existence of the significant number of the close reciprocal interrelationship between the input and output Darameters. Traditional complexity is appeared with regard to absence of the suitable a priori information for the physico-chemical characteristics of the flotation process. It’s led to needful of taking of consideration about the undefinition which have got the place in the real conditions and application of the statistical methods. The identification of the flotation process through statistical methods is conception of the more-stages procedure, including the collection and previous analysis, the choice of the model structure and valuation method, the estimation of the model un- known parameters and the results interpretation. The essential concept for the subject of this paper belongs to the empirical models ("black-box") and deals with optimizing in constant industrial plant process. The offered method envisages the application of process operation data in order to improve the work process or constant accomplishment of better results for the target function in relation to the former achievement. The optimum process solution isn't afixed value under the influence of various factors, but "a moving point" along the response surface and deviates from the scheme solutions. The evolutive planning method constantly "investigates and approaches" the optimum solution for the selected target function. As a matter of fact the expert operates the plant without interrupting the normal work process. The essential concept of method is to attain changes in the standard conditions, but so limited that they will not effect either production or the product. This method is based on statistical concepts and availability of following the risk of error. The possible influental factors for the flotation process (m=l, 2, 3) is following: the metal content in the feed ore; production level (t/h); grinding fineness in the flotation pulp; pH-values; the consumption of collectors and modifiers The possible target functions are: the recovery of plant capacity, metal recovery in the concentration process and concentration quality. The application of the evolutive operativity method in the chalcopyrite flotation- Bucim concentrator, combines the statistical data and the operator's experience in the interpretation and making a decision which adds up to the precise automatic performance of the process. The advantages of this method in relation to the existing procedure for the flotation process are the following: • The method is unexpensive and losses are reduced to the time necessary to collect the data and record them in the computer. This method provides a constant process control and a quality decision which is better than those brought by an ex- pert with great experience ("hit-and-miss method"). • The method also provides incidental data about the effects. • The method should not be considered as a procedure for solving an incidental problem ("crash program"). • The obtained results must be interpreted by an appropriate expert in order to be considered instructive. MATHEMATICAL STATISTICS Taking into consideration the complexity of the enrichment processes it's necessary the application of "black-box" and mathematical modelling. The presence of the indefinite elements compel us towards the both theory of the probability and mathematical statistics. The mathematical statistics by the mineral processing investigation of the valuable raw materials in the last years has had greater signifance and widely spread application. The application of the mathematical statistics methods for the technological pro- cess analysis and the construction of the mathematical models is bound up by the task putting of the automatic control system de- sign (Fisher R. A. 1941, 1949). The statistical analysis in the enrichment processes is applied formerly, especially in the sampling estimation. Contemporary, in the last years is imposed the tendency of mathematical statistics application for the obtaining of quantity characteristics and quantity valuation from the individual influental factors. Above mentioned tendency in the significant level is based by the mathematical statistics development as a mathematical discipline close connected with the technical cybernetics general joining to the investigated object as a "black-box". Another essential factor in the mathematical statistics development is appeared the created mathematical theory of experiments as a new, to some extent, autonomous statistical domain. The theory of experiments has demonstrated exclusively importance for the investigation of the complex more-factorial processes in the chemistry, mineral processing, metallurgy etc. The investigation by the enrichment processes of the valuable raw materials and their management is possible by the statistical method application. In the same time, it's possible to use the wide-spread traditional methods of the statistical analysis, such as the methods of the dispersion, correlation, regression etc. Also, it may be mentioned above all the methods of the statistical planning of the extreme experiments. The more perspective are representatived some cybernetic methods which are based by the probability as an approach in the process analysis, for example, the identify of the ways and forms, the graph application as an additional instrument in the correlation analysis, the dynamic programming etc. The mathematical statistics application in the laboratory investigation scale is connected above all by the experimented material analysis and the compact representation of the obtained results. The mathematical statistics methods are more varrying and may be applied in the investigations of the wide circle of problems

Jan 1, 1996

By Harvey Parker

This is part two of an article on the prominent role that the United States and its industry leaders have played on the International Tunnelling and Underground Space Association (ITA), which represents the underground construction and underground space industries worldwide. The U.S. is officially represented in ITA by UCA of SME. (Part one is in T&UC, June 2007, pp 39-42) Tunnel advances in 1960s and 1970s The 1960s and 1970s were active and productive times for the U.S. tunneling industry. During that time, federal programs, sponsored by the Federal Railroad Administration (FRA), the Office of High Speed Ground Transportation (OHSGT) and the Advanced Research Projects Administration (ARPA), stimulated tunnel research and development. Also, the American Society of Civil Engineers (ASCE) and SME collaborated to create the Underground Construction Research Council (UCRC) and the Rapid Excavation and Tunneling Conference (RETC) series.

Jan 1, 2007

By Quanjun Liu, Rongping Lin, Rongdong Deng

Arsenic contamination significantly affects the quality of copper concentrates, presenting challenges during smelting processes. Considering that covellite and enargite have similar surface properties, they are difficult to separate by flotation, resulting in copper concentrates with excessive levels of arsenic. To address this issue, this study systematically investigated the flotation separation of covellite and enargite in microflotation and bench-scale flotation tests using calcium lignosulfonate as a depressant, with the results indicating that calcium lignosulfonate can be used to separate covellite and enargite because it enables the separation of arsenic-bearing copper minerals into high- and low-arsenic (As 0.57%) copper concentrates. According to contact angle and adsorption tests, scanning electron microscopy–energy dispersive spectroscopy, and X-ray photoelectron spectroscopy, the differential adsorption of calcium lignosulfonate onto covellite and enargite is the primary reason for their distinct flotation behaviors in the presence of calcium lignosulfonate. The selective depressive effect of calcium lignosulfonate provides a novel approach for improving the flotation separation of arsenic-bearing minerals from copper sulfide minerals.

Feb 28, 2024

By Russell L. Wood

The title of this session seems to have been picked especially for this paper. It is 1984, it is the morning after, and there is one monumental hangover among many if not most of the oil companies that have invested in mining in the past decade or so. How an oil company looks at mining depends on what time period you are talking about. A few years back around the time of investment this is what they were probably looking at: 1. A balance sheet of their own that was beginning to go wild, with many of their commodity prices having already seen increases of two, three, or four fold, and with no end in sight. 2. A need to invest their earnings someplace fast before the stockholders or the government got too interested. And that someplace should be in an industry where their own management skills could be applied. (Only a true cynic would suggest that this is a form of job security) 3. In mining there was an industry amazingly similiar to their own, one working with non-renewable natural resources, dealing with the same types of government agencies, and having the same type of critics and pressures from the general population. 4. An industry that was somewhat backward as compared with their own, and one where a generous ration of the capital and management skills so handsomely bestowed upon the oil industry could be used to great advantage.

Jan 1, 1984

General. Data for the operating information given in the 15 tables in this chapter was obtained from voluminous questionnaires sent to over 100 operating companies in 1972. There has been a considera¬ble change since then in supply and power costs and many companies have had expansions or revisions since that time, so it must be realized that information is valid for the year 1972. This is true except for the three new properties of Sacaton, Metcalf, and Pinto Valley. These three operations started up since 1972 and all information for them was obtained in 1975. The questionnaires were sent to all major copper properties throughout the world as well as to many smaller units and to some mines that had complex or unusual conditions. Properties for which no information is given did not submit completed questionnaires. Several operations were unable to supply information requested be¬cause of company policy prohibiting it. However, data is presented for 75 different operating properties. The reference number of the left-hand column is the same for all 15 tables of data. If the company had several operating properties as of 1972, then subsequent properties use the same number but a different letter. For example, Anaconda's property at Butte, Mont., is IA, whereas Anaconda's (now Anamax) Twin Buttes property in Arizona is IB. Table I gives general data for the properties including exact loca¬tion, milling rate, pertinent assay values and recoveries, and a brief listing of ore and gangue minerals. It was not possible to obtain any more information from the properties in Chile except that given in Table I. Crushing. Crushing plant operating data is given in Table 2. This table gives data on the crushers, feeders, and screens used at each property. The data obtained on feeders was confusing, but, rather than completely eliminate this information, it was decided to report it as given. The confusion lies only in the description of where the feeder is located. Where a primary feeder is listed it was not possible to determine if this feeder was on primary feed or primary discharge. For secondary feeders it is known that the feeder listed usually is feeding the secondary crushers, but at some properties it is handling the secondary crusher discharge. The same reasoning holds true for tertiary feeders-they handle either tertiary feed or discharge. This table contains a voluminous amount of data. A column giving tons per day per square foot of screen area would have been very informative, but some properties included circulating load in the feed rate and others listed new feed only, so calculations were meaningless. Autogenous Mills. The use of autogenous or semiautogenous mills for any property must be given serious consideration in the future. Table 3 lists data for four properties that are fully autogenous and four more semiautogenous mills that use balls to supplement the chunks of ore. This method of grinding is especially applicable when the ore is of such a nature that crushing problems would be severe, such as when ore is wet or sticky or contains a lot of fines. Paradoxically, it should also be considered when ore is tough and hard and blocky because then the competency of the ore means it can serve well as the grinding media. Where the ore varies greatly in hardness, as at Cyprus Pima and Lornex, semiautogenous grinding has been especially beneficial with capital costs and operating costs both 10-20% lower than could be obtained with conventional crushing and grinding. Rod Mills. For a great many years the standard milling operation used two- or three-stage crushing followed by open circuit rod mills and then ball mills in closed circuit with classifiers of some kind. A surprising number of properties crush to the fine size of about 3/8 in. and then use ball mills only, in closed circuit, with no rod mills. It is difficult to say whether rod mill-ball mill circuits or ball mill only is the best. One can be certain of two things: (1) the argument will go on for a long time and (2) for some mills one method obviously was superior over the other. As ball mills of 14, 15 ft, and larger came into use, more properties like Duval Sierrita (16b ft diam by 19 ft long) and Bougainville (18 x 21 ft) were built with single-stage ball mill grinding. Although there are larger rod mills used, especially in the iron ore industry, the largest rod mills on copper ore are at Twin Buttes (14 x 18.5 ft) and at Gibraltar (13'A x 20 ft). Table 4 lists operating data for rod mills. If a company is listed in Table I

Jan 1, 1985

By C. I. Basilio

The mechanisms involved in the adsorption of modified thiol-type collectors on sulfide minerals have been investigated in the present work. These collectors belong to the broad classes of thionocarbamates, thioureas, thiophosphates and thiophosphinates. They differ significantly from the traditionally used thiol-type collectors, such as xanthates and dithiophosphates, in terms of structural features that involve either the introduction of an additional oxygen donor or the alteration of electron densities on donor atoms. Electrochemical studies suggest that the adsorption of these classes of collectors is probably the result of a coupled reaction of the EC-type, involving an initial electron transfer step (E), followed immediately by a chemical reaction (C). Thus, the overall adsorption process is controlled by both the E, and pK of the system. The role of structural features in changing the interaction of the donor atoms with sulfide minerals is also discussed.

Jan 1, 1991

By A. Griffiths

The? use of hydrogen peroxide to detoxify gold mill waste waters containing cyanide and other toxic substances is already an established technology. Recent advances have extended the range of application of hydrogen peroxide treatment to include the removal of complex iron cyanides, the simultaneous removal of cyanide and toxic metals down to very low levels and treatment of barren bleeds, CIP' pulps and tailings pond discharges. Three treatment plants are described here. Each was installed at a gold mine in North America in 1987 and each illustrates a different application of hydrogen peroxide. The need for individual design of the detoxification plant to fit particular requirements is shown by the examples chosen.

Jan 1, 1988

By M. S. Moats, A. Luyima, W. Cui

"Organic smoothing additives are used to produce dense, thick, high-quality cathodes in copper electrowinning. Glue had been used traditionally and is still used in operations that do not employ solvent extraction to produce the electrowinning electrolyte. With the advent of solvent extraction–electrowinning, guar started to be used and remained in use for many years as it does not affect the phase disengagement in solvent extraction. Recently, however, guar has been replaced by less-expensive saccharide- and polyacrylamide-based additives. This paper is the first of a series of four papers that examine saccharides and polyacrylamides as new additives for copper electrowinning. A review of previous research related to copper electrowinning additives is presented here, along with a selected review of additives in other copper electrodeposition systems.IntroductionThe recovery of copper from solution by electrowinning was first practiced in the early 1900s, but it was the combination of solvent extraction with electrowinning (SX-EW) in March 1968 at the Ranchers Bluebird Mine (Kordosky, 1992) that changed the landscape for the electrowinning process. Most copper electrowinning capacity is now associated with solvent extraction, though some copper is still won directly from leach solutions (Robinson et al., 2013). The ability to produce high-purity copper cathodes from SX-EW has taken the continued improvement of SX-EW technology over the past more than 40 years.One of the technologies that has seen improvement is that of the organic smoothing agents used during the electrodeposition of copper in the tankhouse. These organic additives are added to the acidic copper sulfate electrolyte during electrowinning to improve the smoothness, brightness and density of the copper cathodes. The organic additives that are presently in use are different from those used in 1999 (Jenkins et al., 1999). Over the past decade, many tankhouses have replaced the use of guar-based organic additives with those derived from other saccharides. Until now, there has been no comprehensive publication in the open literature on the behavior of these additives during copper electrowinning."

Jan 1, 2016

By Qinbo Cao, Qianshan Peng, Heng Zou, Xingcai Yu

In this work, a new flotation strategy was proposed for the flotation of rutile. In this strategy, rutile was activated by Pb(NO3)2 and then floated with amyl xanthate (AX) as a collector at pH 8. Pb(OH)+ was the dominant lead species in the solution at pH 8 and is believed to be the major species reacting with the rutile surface. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) study revealed that the lead activation products were well distributed on the rutile surface, and AX− could further bind with the Pb atom on the Pb-activated rutile surface. In this regard, the Pb-activated rutile could be floated by AX. Furthermore, X-ray photoelectron spectroscopy (XPS) analysis indicated that Pb(OH)2 was generated on the Pb-activated rutile surface. The electron transfer during the adsorption of the AX− on the Pb-activated rutile surface was also investigated by XPS analysis.

By John W. Reddy

The C&NW Ore Dock at Escanaba, Michigan, is a major terminal on Lake Michigan for iron ore pellets arriving from the Marquette Iron Range located 112 km (70 miles) to the north. In an average year, the terminal handles in excess of 8 000 000 Mg (LT) of iron ore pellets consigned to a number of major steel companies. It is important to the steel companies for both cost control and operating efficiency that each cargo be sampled as accurately as possible in order to determine the physical and chemical properties of the pellets. This paper describes the equipment and operating procedures of the sampling facility and Presents some sampling data.

Jan 1, 1985

By N. Arbiter

Fracture under low velocity free-fall and double impact, and under slow compression have been-investigated. The pattern of breakage and the size distribution of resulting fragments for sand-cement and glass spheres have been determined. Photoelasticity methods were used to simulate the stress distributions in free-fall impact in order to explain the observed patterns of breakage. Oblique fracture planes, occurring only in free-fall impact, develop along lines which coincide with the trajectories of principal compression as determined by mathematical analysis Breakage efficiencies for different modes of fracture were compared for both types of spheres. For the same specimen and loading system, static loading and low velocity dynamic loading induce geometrically similar stress fields resulting in reasonably similar fracture patterns and shapes of fragments.

Jan 1, 1968

By D. G. Chedgy

Careful consideration is given to the type of cleaning equipment and control sys- teas to be used when selecting circuits for wash-ing fine coal (28M x 0 size fraction). However, the desliming, declaying and sizing procedures required to ensure efficient operation normally are not evaluated in sufficient detail resulting in disappointing system performance. This paper details desliming and dewatering circuit design which is extremely effective based on recent test data. The circuit maintains control of the 28M x 0 (declayed) size fraction with minimal misplaced material and maximized circuit efficiency. A discussion of circuit design parameters and control systems, as well as results from the testing program, are included in this text.

Jan 1, 1986

By S. Constantinescu

The alloys mainly used for short (or segmented) chip material cutting (cast iron, porcelain, etc) are alloys of the WC-Co type; in some cases with small additions of other carbons. The same alloys but of different granulometric classes are also used for pieces exposed to wear (wire drawing, moulds) The higher performance of the WC-Co alloys in chip machining applications is accounted for by their very good heat conductivity, which is 2-3 times higher than that of fast steels. The hard-alloys producers can resort to a wide range of possibilities to achieve variation of properties of a WC-Co composition and thus they can adapt their products to the particular type of tools they may choose to manufacture. The present metallography technique allows for a correct identification and evaluation of hard sintered carbons structures. The metallography approach is an indispensable method of investigation and control in the industry.

Jan 1, 2008

By Judson H. Whitman

To evaluate intelligently and to market a source of rare earth raw material, it is necessary that the producer understand the requirements of the processor and the manner in which these requirements effect the value and salability of his product. This paper will be an attempt to aid in such an understanding. The majority of rare earth processors are primarily chemical companies, not mining or metallurgical companies, as the complexities of the processing procedures are' much more chemical in nature than metallurgical. The rare earths and the rare earth industry are normally divided into two groups - the ?light? or cerium group and the ?heavy? or yttrium group. They are so named because cerium and yttrium are the most common elements in 'heir respective groups and are so divided on the basis of mineralogical and chemical characteristics. The dividing line of the two groups is not rigidly fixed but usually is considered as being between samarium (atomic number 62) and europium (atomic number 63). Although the two groups are quite similar, processing procedures differ significantly, hence most processors tend to specialize in one group or the other. There is, however, a growing tendency toward participation in both groups.

Jan 1, 1960