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By G. R. Rawsthorne

"The Con-Rycon mine is located on the north shore of Great Slave Lake in the Northwest Territories within the present city limits of Yellow-knife. Development work on the Con property started in 1936, resulting in a mine-mill complex which produced its first gold brick on September 5, 1938. Since that date 5,000,000 tons of ore have been mined yielding 3,000,000 ounces of gold. At present there are 220 employees at the mine.MineThe mine has 1.22 miles of vertical shaft, 41 miles of level development and 10 miles of inclined raises. There has been 1,000,000 feet of diamond drilling in search of ore. The temperature at the 4900 level (4400 feet below sea level) is 68 deg. F.The present mining method is cut and fill. The majority of the ore mined today passed through an internal winze before reaching the main shaft. The long haulage and double handling will be eliminated with the completion of a new shaft presently under construction to the 5800 level.MineralizationThe ore treated today is from the Campbell shear 1vhich is characterized by lenses and veinlets of coarse textured quartz containing some carbonate, sulphides and finely disseminated as well as visible gold. At the lower levels of the mine the arsenopyrite content in the ore is de-creasing with a~ increase in the levels of chalcopyrite and pyrrhotite."

Jan 1, 1974

By Robert W. Bruhn

Ground movements associated with high extraction underground coal mining, such as pillar retreat and longwall, are some- times large enough to disrupt the ground water regime as well as damage buildings and other surface structures. A U.S. Department of Energy Bureau of Mines- sponsored subsidence study at Kitt Energy Corporation's Kitt No. 1 Mine near Philippi (Barbour County) , West Virginia has provided an opportunity to monitor the ground water response above a mine panel during both developmental and pillar re- treat mining. Findings concerning ground water effects presented in this paper indicate that total extraction mining produced significant water level declines in deep-lying strata but had little effect on water levels at shallower depths. Post-mining values of hydraulic conductivity were typically somewhat higher than pre-mining values. Changes in water chemistry associated with mining were not sufficient to render the water unfit for human consumption.

Jan 1, 1986

By D. Eastick, S. Hardcastle

"Over the last few years, a multi-faceted feasibility study has been evaluating the introduction of hydrogen fuel cell-powered equipment into underground mines to replaced diesel engine-powered equipment. The analysis has shown that under normal operating conditions fuel cells could at the very least be an environmental and health benefit by eliminating combustion engines and their unwanted by-products. However, they could also generate significant reductions in the amount of ventilation a mine needs to supply when compared to dieselized operations; this would further decrease a mine’s energy consumption, its associated greenhouse gas impact, and also reduce a mine’s significant ventilation-associated costs. Fuel cell-powered equipment also has the advantage of lower noise and heat production compared to its equivalent diesel-powered counterpart.The degree to which fuel cells can generate ventilation benefits in underground mines depends upon a number of operational parameters and mine specific qualifiers such as current ventilation control or management, mine depth, inherent dust conditions, and minimum velocity requirements.However, another major consideration in the introduction of fuel cells in underground mines will be the safety requirements associated with diluting and removing the potentially explosive hydrogen in the event of a gas leak. In outside surface applications, it is possible to use dispersion, buoyancy, time, and lack of ignition sources as mitigating factors in deriving a low risk of an explosion. However, in underground operations, these factors change, and dispersion and buoyancy are limited; time may not be available and, in non-coal mines, ignition sources are not typically controlled. When a hydrogen leak occurs, the availability of sufficient ventilation to dilute and effectively remove the gas will be critical. Consequently, ventilation may be the prime risk controlling factor. In this paper, the authors evaluate the potential benefits of replacing diesel engines with fuel cells in powered production equipment, discuss the mitigating qualifiers that could limit ventilation savings, and evaluate solutions to retain and maintain an additional ventilation capacity in the event of an emergency situation, such as a hydrogen leak from the fuel cell stack or its distribution system."

Jan 1, 2007

By Roy G. Stott, John A. Johnson, Floyd G. Anderson

"This information circular discusses drilling and blasting in open-cut iron-ore mines and is one of a series of papers describing iron-ore mining practices in the Lake Superior district to aid in preventing accidents in that industry.The Lake Superior district consists of the Marquette and Menominee ranges of Michigan, the Gogebic range of Michigan and Wisconsin, and the Vermilion, Mesabi, and Cuyuna range of Minnesota. Open-cut mines produce 8o percent of the iron ore mined in the district; 98 percent of the total Lake Superior district open-cut ore is produced in Minnesota and 2 percent in Michigan. The entire Wisconsin iron-ore production is from underground nines. The Mesabi range in Minnesota produced 93 percent of the open-cut iron ore and 76 percent of the total iron ore in the district in 1947.During the 8-year period 1940-47, 619,000,000 gross tons of iron ore were shipped from mines of the district, or 85 percent of the United States output. Approximately 78,000,000 gross tons of iron ore were shipped from the mines of Minnesota, Michigan, and Wisconsin in 1947.This paper is based primarily on observations daring the period July 1947 to March 1948. Thirty-two open-cut mines were visited; 28 on the Mesabi range, 3 on the Cuyuna range, and 1 on the Marquette range. In 1947, 36,100,000 tons of iron ore was shipped from these 32 mines, or 59 percent of the open-cut ore and 46 percent of the total iron ore shipped from the district. During 1947 about 90 open-cut iron-ore mines were operating in the district, and the annual production of each ranged from 25,000 to 10,000,000 tons.Many recommendations included in this paper for improving safety and preventing injuries to employees were taken from Bureau of Mines Information Circular 7387.Data were collected under the direction of Frank E. Cash, former supervising engineer, Health and Safety Division, Bureau of Nines, Duluth, Minnesota. E. W. Felegy, mining engineer, Safety Branch, gave valuable assistance in reviewing and editing the manuscript.The authors gratefully acknowledge the information and assistance given and the numerous courtesies extended to them by officials of the following mining companies:All the Lake Superior iron ores occur in bedded formations that range from less than 100 feet to over 2,000 feet in thickness. These formations are designated by one commonly applied name, ""iron formations.""4/The Mesabi range in northern Minnesota, about 70 miles northwest of Duluth, was opened to mining in 1892; it is the largest single source of iron ore in the United States. It is 75 miles long and, because of the gentle dip of the ore formation, it ranges in width from 1-1/2 to 3 miles.5/ The ore formation, which is nearly horizontal, has a maximum thickness of about 450 feet and is covered by a glacial drift that ranges from 10 to over 100 feet in thickness. Most of the ore is near the surface and adaptable to open-cut mining."

Mar 1, 1950

We report the studies of Proton-Exchange Membrane Fuel Cells (PEM FC) and hydrogen storage materials at McMaster University for the last 14 years. From the initial investigation of ionic conduction mechanism to the revelation of the origin of non-Arrhenius temperature dependence, as well as the synthesis and characterization of high temperature polymer electrolytes, both experimental and theoretical works have been compiled for the fuel cell membranes. In addition to the discovery of suppressed ionic conduction in Electrode-Membrane Assembly (EMA) and novel hydrocarbon PEMs based on micro-emulsion, the first evidence of hydrogen adsorption saturation by carbon nano-tubes was also achieved, which has been the bottleneck for the application of PEM FC. Prior to our study, a number of controversial publications have claimed the hydrogen capacity of these materials to be between 0.1 to 10.0 wt.%, and none demonstrated a plateau of adsorption with pressure that is consistent with monolayer saturation. Others suggested that the tube bundle structure is opened under high pressure to enable higher adsorption on newly uncovered surfaces, but received no confirmation. Using our home made high-pressure instrument with in-situ electrical probes, we found that a plateau is nearly achieved at about 300 atm in the room temperature isotherm, and that nanotube bundles actually compress with pressure instead of splitting, using in-situ electrical measurements.

Jan 1, 2005

By C. Droun

"Low back pains account for about 13 per cent of all compensation claims made to the Quebec Workmen's Compensation Commission and cost the employers a sum exceeding ten million dollars. The frequency and cost of these health problems in Quebec metal mines are proportional to the provincial trends. An elaborate review of the literature on the causes, nature and prevention of low back pain is made in this presentation. A prevention program for low back pain has been designed in cooperation with a team of seven medical specialists and two physiotherapists for the Quebec metal mines. The program is especially designed for persons who have had low back pain, in order to prevent a recurrence, and for persons beginning to feel chronic difficulties. It is based on existing programs at the Hawthorne Plant of Western Electric Company and at Minnesota Mining and Manufacturing, but it requires a much different approach because of the nature of medical care available at the mining sites. The program is difficult because it involves a change of attitude for every employee and every supervisor. The program, so far, is beneficial because several men are now seriously engaged in an active program of reconditioning and because the problem of low back pain ie beginning to be seen from a new angle."

Jan 1, 1973

By Claude Bazin, Patricia Obiang

"The slurry density (pulp percentage of solids) and the size of the grinding media are often used for the optimization of an operating ball mill. In many cases a change of ball size is made at the slurry density used with the original ball size. But is the optimum slurry density changing with grinding media size? Laboratory grinding tests were conducted to answer that question and results indicate that more than likely there is no need to adjust mill slurry density when adjusting the size of a grinding media in a ball mill. Full scale behaviour could be different because slurry density affects the slurry transportation through the mill and the classifier operation.INTRODUCTIONOre preparation begins with a fragmentation step that liberates valuable minerals or exposes mineral surface to the environment. The size reduction step of a mineral processing operation is energy demanding and the optimisation of this process should always be an objective for the plant metallurgists. Various approaches could be considered for improving the operation of a grinding circuit. For a close grinding circuit an adequate tuning of the classifiers operation may lead to substantial savings (McIvor, 1988). Once a grinding mill is in operation, few variables remain to be considered for process optimization. The ball charge is usually maintained to achieve a target power drawn by the grinding mill motor. The rotation speed is seldom considered (McIvor, 1983; Bazin and Lavoie, 2000) as a change of mill speed usually implies a costly pinion change. If the liner and lifter configuration is critical for SAG and AG mills (Latchireddi et al., 2005), few discussions are available for ball mills (Fuerstenau and Abouzeid, 1985; McIvor, 1983). The mill feed size distribution can also be adjusted but this implies changing the upstream processes, which transposes the optimization process to another level. Modification to grinding media shape is a possible avenue (Cooper et al., 1994), but it remains that slurry density and grinding media size are probably the most frequently considered variables for the optimization of a ball mill."

Jan 1, 2007

By W. R. Hardwick

This information circular describes mining methods and practices at New Cornelia Branch, Phelps Dodge Corp., Ajo, Ariz. It is one of a series being prepared by the Bureau of Mines on mining methods, practices, and costs in various mining districts of the United States. The New Cornelia mine (fig. 1) is at Ajo, a town in southwestern Arizona (fig. 2) on Arizona State Highway 85 in the western part of Pima County. The [oncentrator] and smelter are near the mine (fig. 3). Copper ore is mined, crushed, ground, and concentrated, and the concentrates are smelted. Copper is cast in anode form and sent to the Phelps Dodge Corp. refinery in El Paso, Tex.

Jan 1, 1960

By Francesco Montanari, Gianni Schena

"Recent improvements in X-ray computed tomography allow investigation of objects several tens of millimetres in dimension with spatial resolutions in the order of a few microns. These improvements are made possible by coupling the micro-focus technology adopted by some of the latest cone-beam X-ray sources with an increase in the efficiency of the detectors. The micro-focus technology allows the production of clearer images at high magnification by reducing the penumbra (fuzziness) associated with larger focal spot size.Even higher resolutions can be expected in the next few years with the commercialisation of nano-focus X-ray tubes. In practice one can inspect a system of fine composite particles and analyze the different mineralogical phases in each individual particle. Computed tomography allows accurate liberation studies, e.g. providing liberation spectra or washability data in tens of minutes. However, on-line application of micro-focus computed tomography is unlikely in the foreseeable future, despite rapid development.Dual-energy (DE) radiography is another X-ray technique, which allows retrieval of the volumetric content of valuable components in two-phase particles in a fraction of a second. A digital radiograph of a single two-phase particle produces a grey level image, where the luminosity of the pixels is determined by the sum of the attenuation levels of all the structures. Thus morphological and compositional effects concur to produce the radiographic image, which does not allow retrieval of the composition of the particle, as the 3D-structure of the particle is compressed into a 2D-image, with an obvious loss of information. Thus, in principle it is not possible to discriminate between thick, comparatively penetrable, and thin, comparatively impenetrable mineralogical components."

Jan 1, 2003

By A. T. Iannacchione

Numerical simulation of coal pi1lar loading has traditionally been a difficult task due to the unique and highly variable properties of coal and the inability of numerical procedures to duplicate these properties. This simulation was based upon material properties developed from laboratory tests of coal cubes and examined against coal pillar strength data developed from actual underground measurements. The coal cube measurements indicated the coal followed a nonlinear Mohr- Coulomb failure criterion. The in situ measurements showed that a pillar yield zone developed similar to Wilson's hypothesis and, at high confinements, the pillar core seemed to followed a pseudo-ductile behavior. The strain-softening material model, based on a 1inear Mohr- Coulomb failure criterion, simulated coal cube and pillar behavior at moderate load conditions. However, at high loads the models were inaccurate, due to an inadequate failure mechanism and/or to changes in the pillar constraints at the coalbed interface.

Jan 1, 1989

By S. H. Ash

THE BARRIER-PILLAR SYSTEM in the Lackawanna Basin consists of 93 barrier pillars between Archbald and Taylor, Pa. These pillars affect 48 mines, have a total length of 87 miles, and confine 21 underground pools, which contain more than 10 billion gallons of water. From an investigation of size, position, and condition of the barrier pillars, it is apparent that those concerned are uncertain, not only as to the method by which the sizes of the barrier pillars were determined but also as to the stability of those that may be expected to act as dams. Where a barrier pillar must act as a dam, its failure may result in loss of life, the mine, or both; it would be far better had it not existed and thereby given a false sense of security.

Jan 1, 1952

By Kunihiko Takahashi, Gjergj Dodbiba, Hisayoshi Umeda, Toyohisa Fujita

"An increasing number of mobile phones is increasing the number of the discarded mobile phones. Many efforts are thus being made to collect and recycle these devices. This paper is a short introduction of the recycling system of precious metals from the discarded mobile phone, currently available in Japan. Moreover, an attempt has been made to compare the energy recovery and the mechanical recycling of plastic wastes from the discarded mobile phone. The assessment has been carried out in the context of the life cycle assessment methodology (LCA). The environmental impact of each option was assessed by calculating the following impact indicators: depletion of abiotic resources (ADP), and global warming potential (GWP). 1. Introduction In 2003, the demand for mobile phones was increased since the camera was included in a mobile phone and the 3rd generation of mobile phones was introduced. In turn, the number of discarded mobile phone is rising sharply. Generally speaking, all the metallic parts of mobile phones can be recovered and recycled by using smelting and purification techniques. The recycled materials are then used to fabricate other new products."

Jan 1, 2008

By Reichman J. P

Extensive use is made of a small scale computer (IBM 1130), in the calculations of ore reserves for Western Mining Corporation's nickel mine at Kambalda, W.A. All surface drilling data such as assays, density and location information, are stored on disk files at the Company's Technical Computing Centre at Perth, W.A. The computer is used to search through the data, select significant ore intersections, calculate the area of influence of each intersection and perform the necessary calculations to arrive at an estimate of the ore reserve. Comparing the computer-assisted ore reserve calculation with an entirely manual operation, it is estimated that a saving of 40 percent in time is achieved together with

Jan 1, 1973

By J. F. T. Agapito

OCI Wyoming mines two flat-lying trona seams that are 3- to 3.5-m- (10- to 11.5-ft-) thick, about10 m (33 ft) apart and 250-m- (820-ft-) deep at its Big Island Mine in Wyoming. Continuous miners and a yielding-pillar system have contributed to improvements in resource recovery and productivity. The use of yield pillars minimizes the stresses transmitted from the upper to the lower seam. However, yielding must not impact the good, long-term stability needed to prevent subsidence for a large portion of the mine beneath the Green River channel.

Jan 1, 2000

By Jerome F. Kuzmick

INTRODUCTION THE use of iron powder during the post-war conversion period has been increasing with great rapidity. This is particularly true in regard to the manufacture of molded mechanical parts such as bushings, gears, cams, small wheels, and the like. Many manufacturers have found it possible to replace machined cast iron and carbon steel with molded iron powder parts, and thereby can not only effect a savings in cost, but can produce a better product as well. As the field of application for iron powder parts widens, greater demands are made upon the powder supplier concerning quality and uniformity characteristics. The following are some of the most important properties parts fabricators desire in the iron powder they use: I. The powder should have high compressibility so that good density can be obtained without the use of excessive pressures. At the same time, it should show low die wear so that a large number of pieces can be produced from the die. This means that the powder must be of high purity and good softness or plasticity. 2. The powder should produce compacts of high green strength, so that unsintered parts can be handled without breakage or fraying of the edges. 3. The sintering properties should be good so that satisfactory strength is obtained in the sintered piece. 4. Compacts made from the powder should show small but, above all, uniform dimensional changes during the sintering operation so that accurate parts can be produced, and warping and other such bad effects eliminated. 5. The powder should have satisfactory flow properties for automatic molding. 6. It is very important that the powder be uniform in sieve analysis, compressibility, flow, purity, and other qualities, from container to container in any given lot and from shipment to shipment. 7. Price-The fabricators desire all these good properties, but in many instances still do not wish to pay a premium price. There has been considerable discussion as to the importance of price of the powder in relation to the cost of the finished product. It is true that in cases where certain special properties only procured by powder metallurgy are required, price is not a criterion. On the other hand, there have been a number of applications recently made which would not be commercially practical with a powder which commands a premium in price. Iron powder parts are compressed in automatic presses to definite size, shape, and density. The powder is compressed to a density figure dependent upon the function the part is to perform, as well as upon such important considerations as press capacity and die wear. Such parts can be roughly broken down into the following density ranges:

Jan 1, 1948

The past four years since the 2008 MINExpo have been a roller coaster ride for the mining industry, with highs and lows and everything in between. One of the natural consequences of this uncertainty has been a number of significant consolidations and mergers, and this trend has trickled down into the crushing industry. And while there have been some significant changes to this sector of the mining industry, many of the big players have weathered the storm. The following is a look at some of the mineral processing companies that will be at MINExpo. McLanahan Corp. McLanahan Corp. is an example of the changes in the sector. The crushing and grinding stalwart acquired Universal Engineering, expanding its traditional focus on soft mineral crushing to hard rock crushing. At MINExpo, it will be showing off three new pieces of equipment, the LabMill Crusher, the Rocker Tooth Crusher and the Recessed Filter Press.

Jan 1, 2012

By Manqiu Xu, Joe Holmes, Peter Wells, Peter Langlois, Germain Labonté, Jim Barrett

"The flowsheet for the Voisey’s Bay mill had to meet the challenge of processing an ore containing high pentlandite and chalcopyrite values in a largely pyrrhotite/troilite matrix. In the 1994-97 period, circuit development focused on making a high-grade copper concentrate and a relatively low-grade nickel concentrate. However, in 1998 a circuit with copper concentrate, high-grade nickel concentrate and a Ni/Cu middlings concentrate was specified. Following a three year project delay, work resumed on the flowsheet in 2001, and the target for the overall grade of the nickel concentrate was raised from 14% to 20% nickel. To achieve this target triethylamine tetramine (TETA) and sulfite pyrrhotite depressants were used in an all lime circuit. It later became evident that, with appropriate selection of collector and adjustment of the circuit by the addition of a scavenger on the scavenger cleaner, it would be possible to approach the grade of concentrate required without the use of pyrrhotite depressants. The recycle of water and the contained thiosalts was also proven to be instrumental in raising the grade.Construction and commissioning of the mill were fast-tracked with start-up of the mill in September 2005 some six months ahead of the original schedule. Ramp-up of both throughput and metallurgy was faster than any other recent nickel installations with tonnage being limited mainly by concentrate dewatering due to the higher than initially planned ore grades.INTRODUCTIONNickel was discovered in the vicinity of Voisey’s Bay by Chislett and Verbiski working for Diamond Field Resources in 1993 and the Ovoid deposit was delineated in the winter of 1994/95. By the end of 1995 the Ovoid had been well explored and at that time was thought to have a reserve of at least 30 million tonnes with an average grade of 2.83% Ni and 2.0% Cu. Drilling to the east of the Ovoid had indicated the presence of significant mineralization. In June of 1995, Inco Limited bought a 25% share in the Voisey’s Bay Nickel Company (VBNC) which was a subsidiary holding company set up by Diamond Fields. Inco also bought 8% of Diamond Fields and negotiated the right to sell all the nickel produced from VBNC for twenty years as part of this agreement. In April 1996, Inco bought the 75% of VBNC shares that it did not own."

Jan 1, 2007

By B. H. Moore

The opportunity to evaluate the pile design procedures used on a major project is an infrequent occurrence. It is even more infrequent that the project involves piles with significant tension and horizontal capacities. This report synopsizes over twenty years of design and construction experience on just such a major pile founded structure. The philosophy governing foundation design procedures is described and discussed. The order and extent of full scale pile testing are evaluated. Principal points in the specifications are established and their effect on construction progress and claims are noted. The report concludes with recommendations for future projects.

Jan 1, 2010

By Cuppam Dasarathy

The incidence of liquid inzmiscibility in binar)) indium alloys has been theoretically analyzed on the basis of the Hildebrand-Alott equation. Bedictions of miscibility or otherwise Imve in general been found to agree with those phase diagrams that are already publislzed in the literature. Out of a total of 27 systems, where either the complete phase diagrams are published or liquid immiscible behavior is reported, the Predictions agree with the experimental data in 25 systems, the exceptions being the Te-In and Ni-In systems. According to the equation, liquid immiscibility is also indicated in the binary alloys of indium with K, Rb, Cs, Na, Sr, Ba, Ti, Zr, V. Nb(Cb), Ta, W, U, Re, Ru, Rh, Os, and Ir. RECENT investigations by the author have shown that indium when alloyed with iron, chromium, and cobalt shows liquid immiscible behavior.1"3 The Fe-In phase diagram shows a wide range of compositions where the liquids are immiscible.4,5 No intermediate phases are present in this system. No precise information is available about the extent of liquid immiscibility in the Co-In system. However, it is certain that there is a range of compositions where the liquids are immiscible and that there are two or three intermediate phases,376 in the system. Liquid immiscibility is also strongly indicated in the Cr-In system and no evidence was obtained in the brief investigation to indicate the presence of intermediate Cr-In phases.2 The present paper deals with a theoretical analysis of binary alloys of indium with certain elements of the periodic table and indicates the systems where liquid immiscibility may be expected. The incidence of liquid immiscibility in binary systems has been theoretically examined by many workers and many excellent papers are available on the subject. In this paper, the alloy systems are examined on the basis of the more recent ideas proposed by Mott.7,8 It has been claimed8 that the Mott parameter predicts the incidence of miscibility or otherwise with reasonable accuracy and consistency. BACKGROUND TO MOTT&apos;S APPROACH Hildebrand applied his immiscibility rule for non-polar liquids to various alloy systems.9 The basis of this rule is that the equation for the excess free energy of formation of a liquid solution is rather similar to the theoretical expression for the energy of mixing of a regular solution. He postulated that when the heat of mixing is sufficiently high, separation into liquid phases will occur and the condition for complete CUPPAM DASARATHY is at the Research Centre, British Steel Corporation, (South Wales Group), Port Talbot, Glamorgan, Great Britain. Manuscript submitted March 12, 1969. IMD miscibility was shown as where VA and VB were the atomic volumes of the components A and B, and ?EV the energy of vaporization of the component. The term (?EVA/VA)1/2 was regarded as a measure of the binding energy of the component A and was called the L&apos;solubility parameter" 8A. On this basis immiscibility occurs when 1/2(VA+VB)(bA-bBf > 2RT [2] Apparently, however, there were several inconsistencies in that according to Eq. [2] several systems known to be miscible in the liquid state were predicted as immiscible. MOTT&apos;S ANALYSIS ~ott&apos;" regards that the reason for the inconsistencies arising out of Hildebrand&apos;s equation was largely due to the electrochemical attraction between the two elements, not being considered. Hence, Eqs. [I] and [2] were modified by taking into account the electro-negativities of the two elements XA and XB, and Mott arrived at an equation for immiscibility, i(VA + VB)(6A - aB)2 - 23,Q60n(XA - XBf > 2RT [3j which can be written as i **&£*&* >&apos;*°™- &apos;• HI T being the melting point of the more refractory component of the system. In Eq. [4], the numerator was called the Hildebrand term, the denominator, the electronegativity term, and their ratio, the Mott number. Mott observed that if the Mott number of a given binary system was greater than the maximum number of Pauling bonds which the two metals could form, then liquid immiscibility could be expected. The maximum number of bonds formed by a given metal was considered to be directly related to the number of bonding electrons available, i.e., to its maximum valency. Since the valencies of the elements considered vary from 1 to 6, Mott assumed that if the ratio of the Hildebrand term to the electronegativity term was >6, then immiscibility could be expected. On the contrary, if the ratio is <1, the metals should be miscible. Further, the alloying behavior is not only influenced by the valencies of the two elements but also by the relative atomic sizes that influence the types of packing and hence the coordination number. Mott considers that on average the maximum number of near neighbors of unlike atoms is 6. Thus, on both valency and size factor considerations, Mott concludes that the maximum number of bonds&apos; possible in any system was 6, this being the upper limit of the Mott number for miscibility. In considering the alloying behavior of systems with Mott numbers between 1 and 6, Mott plotted the num-

Jan 1, 1970

By Jerome F. Kuzmick

The use of iron powder during the postwar conversion period has been increasing with great rapidity. This is particularly true in regard to the manufacture of molded mechanical parts such as bushings, gears, cams, small wheels, and the like. Many manufacturers have found it possible to replace machined cast iron and carbon steel with molded iron powder parts, and thereby can not only effect a savings in cost, but can produce a better product as well. As the field of application for iron powder parts widens, greater demands are made upon the powder supplier concerning quality and uniformity characteristics. The following are some of the most important properties parts fabricators desire in the iron powder they use: 1. The powder should have high compressibility so that good density can be obtained without the use of excessive pressures. At the same time, it should show low die wear so that a large number of pieces can be produced from the die. This means that the powder must be of high purity and good softness or plasticity. 2. The powder should produce compacts of high green strength, so that unsintered parts can be handled without breakage or fraying of the edges. 3. The sintering properties should be good so that satisfactory strength is obtained in the sintered piece. 4. Compacts made from the powder should show small but, above all, uniform dimensional changes during the sintering operation so that accurate parts can be produced, and warping and other such bad effects eliminated. 5. The powder should have satisfactory flow properties for automatic molding. 6. It is very important that the powder be uniform in sieve analysis, compressibility, flow, purity, and other qualities, from container to container in any given lot and from shipment to shipment. 7. Price—The fabricators desire all these good properties, but in many instances still do not wish to pay a premium price. There has been considerable discussion as to the importance of price of the powder in relation to the cost of the finished product. It is true that in cases where certain special properties only procured by powder metallurgy are required, price is not a criterion. On the other hand, there have been a number of applications recently made which would not be commercially practical with a powder which commands a premium in price. Iron powder parts are compressed in automatic presses to definite size, shape, and density. The powder is compressed to a density figure dependent upon the function the part is to perform, as well as upon such important considerations as press capacity and die wear. Such parts can be roughly broken down into the following density ranges:

Jan 1, 1949