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By J. Shanks

In 1920 the writer presented some notes, embodying his experience with storage-battery locomotives as main under-ground haulage-motors at Brazeau collieries. (1) Since that date these motors have stood up well to the test of maximum output and heavy overloads, having accomplished all that was expected of them. The notes presented in 1920 gave a brief description of the conditions under which these motors were working at Brazeau collieries, also the cost, per ton mile, of operating them. The cost per ton mile has since then been appreciably reduced, by working the locomotives nearly to capacity and under more ideal haulage conditions, on both shifts. It is not the intention of the writer to repeat what was written in 1920, but rather to give members the benefit of his experience in operating different types or designs of locomotives; to draw their attention to the drawbacks of some designs, and to the improvements made in some of the more recent storage-battery locomotives put on the market, as regards efficiency, upkeep, and safety. Because of their flexibility storage-battery locomotives have advantages over any other type of haulage, where grades are suitable to their use. The number in use in the mines in the United States has increased enormously during the past few years, and this method of haulage is, at the present time, attracting the attention of British and Continental mining engineers.

Jan 1, 1924

By S. Torres, J. Álvarez, R. Castillo, R. Fuentes, C. Sandoval, R. Parra, Myakalwar A. K., M. Velázquez, J. Yáñez, D. Sbarbaro

Rapid analytical assessment in copper mining industry is a limiting factor for operational purposes and for the improvement of processes. The present work aims to review the analytical assessment in the copper industry utilizing emerging spectrochemical techniques such as laser induced breakdown spectroscopy (LIBS) and UV-Vis-IR Hyperspectral Sensing. LIBS is a plasma based spectroscopic method where the sample surface is irradiated by high power laser. The light emitted from the plasma contains atomic -molecular spectral information and can be detected using a simple CCD based spectrometer. UV-Vis-IR Hyperspectral Sensing is produced by the reflection of light from the sample’s rough surface in all directions and it can be collected by using an ellipsoid or paraboloid mirror arrangement. The electromagnetic radiation emitted by the samples in the UV-Vis, NIR and MIR region can be used for molecular characterization. The spectrometer splits different wavelengths through a CCD arrangement in 2D spatial and spectral dimensions, thus a hyperspectral cube of data is generated. Chemometric techniques such as principal component analysis (PCA), K- nearest neighbors (KNN), support vector machine (SVM) among others, can be applied to LIBS and Hyperspectral data for better classification and quantification purposes in copper ores. Real- time determination of elemental and mineral species used for online processing control will help to achieve the copper industry 4.0. INTRODUCTION The demand for copper mineral resources is intensely growing with the increase in population, per capita GDP, the development of new technologies and the increase in global living standard. With the rise in consumption of copper, it is important to optimize mining and metallurgical processes tending to the copper industry 4.0 (Ge, Song, Ding, & Huang, 2017). The real-time analytical assessment in the mining and metallurgical processes is a crucial part for allowing the global improvement in mining industry. The features considered for better analytical assessment are the instrumental automation and interconnection, real time results, low cost, quality in terms of accuracy and precision. Furthermore, improving recovery (extraction), timing and quality of final products avoiding environmental impacts. Some elements such as Cu, Fe, Ag, Au, Mo, S, As, Pb, Zn are important to be determined in the process control. Additionally, rapid mineral identification of few species such as CuFeS2, Cu4FeS5, FeS2, CuS, Cu2S, MoS2, Cu3AsS4, FeAsS, among other can be challenging.

Jan 1, 2019

By Jr. Mason

Eminent Domain is the power of the government or municipality to take property for public use without the consent or acceptance of the owner. Typically the agency taking the property will make an offer on the property, hoping that the owner will immediately accept and allow work to begin. If a mutual resolution regarding the property value cannot be reached, however, the municipality will condemn the premises and institute a condemnation action in a court of law, which is when the problems begin. The power of the government to take the subject property is limited by the Federal and State constitutional duty to pay "just compensation" for the property.

Jan 1, 1989

By Paul C. Schmall, Thomas Tuozzolo, Arthur B. Corwin

The Lenox Avenue Reconstruction Project involved the excavation and replacement of 750 m (2,500 ft) of deteriorated subway invert concrete, 5 to 7 m (15 to20 ft) below water table in very permeable ground. The Replacement work was done over an 8 month period, while maintaining track service through this subway section. The project was dewatered with a single 125 l/s (2,000 gpm) wellpoint system,750 m (2,500 ft) in length, which was installed from inside the active tunnel structure and configured to coexist in the subway tunnel with operating trains as well as the construction activities. A thin diaphragm jet grout wall was utilized on one end of the site to cut off the flow of water across a difficult geological interface that was situated immediately below the tunnel invert. The thin diaphragm jet grout wall permitted the large 116th Street Station area to be dewatered completely with well points from outside of the excavation.

Jan 1, 2001

A simple and cost effective technique to increase fragmentation and burden velocities without making major modification to the overall blast design is with ALTERNATE VELOCITY LOADING OR BOOSTERING OF ANFO. The technique requires the placement of a cartridge or slug of explosive, having higher density and detonation velocity than ANFO, every few feet in an ANFO column. The greater the difference in density and detonation velocity of the Alternate Velocity Load to ANFO, the more pronounced are the results. Emulsions were selected as the Alternate Velocity test explosives because they detonate closer to ideal conditions than most other commercial explosives.

Jan 1, 1989

By R. G. Lazzell

THE British are worried about the postwar possibilities of their coal mining industry. Indeed, there are causes for this worry, with the aver- age 1943 cost of production at about $5.40 per long ton, compared to $3.20 in 1938. Average production per man day has dropped from 1.12 in 1938 to 1.03 long tons in 1943. As a comparison, production per man day in the United States is approximately 5 long tons. The average day wage in the British mines is now a little aver $4; in 1938 the average day wage was about $2.25. Great Britain produced 227 million long tons in 1938 from their deep mines, and in 1943 production was 194.5 million, with an additional 4.5 million from strip mines. To meet present wartime needs, output is being supplemented by the production of strip- mined coal, an industry that did not exist prior to the war. Strip mining is now producing at the rate of 15 million long tons per year.

Jan 1, 1944

By Fred Jones

The Cripple Creek district is in Teller County, Colo., about 18 miles in an air line west of Colorado Springs and at an elevation of 10,000 It. A line drawn through Colorado Springs and Pikes Peak will, if continued, about pass through the district. The character of the country generally is rolling, with few trees and little snow fall. The annual precipitation is about 20 in. All the water used by the mines is supplied by the Altman Water Co., which pumps from the west slope of Pikes Peak. Gold was discovered in 1891, since which time the district has produced $411,000,000. The peak of production was reached in 1900 and amounted to $25,000,000. At present the production amounts to about $400,000 per month. Geology In general, the geology of the district is simple; ash veins and dikes traverse a volcanic plug of breccia. The ore occurs as enriched spots along these dikes and veins. The dikes represent the most recent extrusions and consist of basalt and phonolite. (For a complete geological description reference is made to Professional Paper 54, 1906, of the U. S. Geological Survey.) The ore consists of small parallel seams of high grade. In only a few cases is the gold disseminated through the rock; much of the gold in the broken ore is found in the fines. The wall rock is hard blocky granite or breccia. About 25 per cent. of the rock mined is shipped as ore to the Golden Cycle mill at Colorado Springs. The height of an ore deposit is usually several times its length. Few flat oreshoots have been found. The veins are all steep and have a dip of 70 to 80°. Development The claims are all 300 by 1500 ft. and are held by location or patent. All mining is done through shafts, one of which has reached a depth of 2600 ft. The main working shafts are 41/29 by 1335 It. and are made up of three compartments, each 4 by 41/2 ft. in the clear. They are timbered with 10-in. Oregon posts and plates and 8-in. spreaders. Two compart-

Jan 1, 1925

By Hon. Tasker Oddie

DURING the closing days of the last Congress a resolution was passed, creating the Senate Com-mission of Gold and Silver Inquiry. The resolu-tion charges the Commission with the responsibility to investigate and report to the Congress on Jan. 1, 1924, upon the following subjects: 1. The causes of the continuing decrease in the production of gold and silver. 2. The causes of the depressed condition of the gold and silver industry in the United States. 3. The production, reduction, refining, transportation, mar-keting, sale, and uses of gold and silver in the United States and elsewhere. 4. The effect of the decreased production of gold and silver upon commerce, industry, exchange, and prices. The personnel of the Commission is as follows: Senators Pittman, Sterling, Goodling, Walsh and Oddie. At a meeting on May 8, H. N. Lawrie, a mining engi-neer and economist, was appointed as Assistant to the Commission. The present situation with respect to the gold and silver mining industries is well illustrated by the follow-ing data: The total world production of gold (in dollars) for 1915 was $468,724,918, and for 1921, $329,915,101; as shown by the reports of the U. S. Mint; and for the year 1922, $306,793,000, which is based oh a prelimi-nary estimate; this indicates a decrease of 34.5 per cent. between 1915 and 1922. The total world production of silver (in fine ounces) for 1915 was 178,850,000 oz.; for 1921, 175,268,234 oz., a decrease of 2 per cent.

Jan 6, 1923

By Xin Jingmin

The present trend toward concentration of mining activities into fewer sections of a coal mine and application of automation and remote control technologies favor utilization of the longwall mining method. Longwall mining also offers the potential for improving safety and productivity, better ground control and higher levels of recovery. The production potential of a longwall operation is determined by the interaction of several factors including the rate of face advance, the thickness of extraction, the speed of cutting and hauling equipment, the physical dimensions of a longwall panel, and the reliability and availability of the equipment. Some of these factors are dictated by the environment in which the extraction process is to be undertaken. Some other factors, however, can be manipulated in order to optimize the production of the system. The objective of this paper is to develop a stochastic model to simulate the production operations in longwall mining. The activities and parameters that affect the production potential of the longwall operations and the relationships between the activities are identified. An attempt is made to verify these relationships through the use of existing data. The model is then used as a computer simulator to investigate the effects of various activities and parameters on the production capacity of a panel.

Jan 1, 1983

By Fabian Laumen, Sunny Schoone, Felix Leaman, ELISABETH CLAUSEN

The acoustic emission (AE) technology has a high potential for flow characterization in hydraulic transport processes. For instance, in deep-sea mining, there are applications where manganese nodules are transported from the bottom of the sea to the surface or a transport ship. Here, an AE-based flow characterization system plays an important role to avoid the transport of non-related objects. However, the structural materials for the components of this system must be carefully selected to ensure resistance against corrosion and a good AE signal transmission. Therefore, in this experimental study, we evaluated the AE attenuation behavior of four different materials that can be employed in marine environments due to their properties. The results were obtained using thin plates and they indicate which materials have the highest and lowest attenuations. Moreover, we provide insights regarding the different wave modes that propagate on the plates.

Mar 2, 2023

By Robert Glass Cleland

THIS IS a history of a company whose roots run deep into the nation's past and whose field of operations has never been narrowly confined. The men who founded Phelps Dodge were men of initiative and imagination. They were men of strong convictions and upright character. They held fast to the simple virtues and traditions of the days when America was young. This heritage they passed on to their successors. From the very beginning, under such leadership, Phelps Dodge became a company of large affairs. It bought and sold, exported and imported, built factories and organized railroads, converted great forests into lumber, and operated coal and iron mines. Much of the iron, copper, and tin plate used in the United States for a generation was under its control. Its business abroad was extensive enough to warrant the organization of a separate partnership in England. Then, almost half a century after its foundation, the company began to substitute new activities for old and eventually transferred its major operations to the West, primarily to Arizona. The family partnership became a corporation. Exporting and importing gave place to mining and metallurgy. Phelps Dodge became one of the largest

Jan 1, 1952

By Angel Rafael Arce Chilque

Um estudo visando à caracterização metalográfica e metalúrgica foi realizado em um aço ARBL (alta resistência e baixa liga) tipo X80, soldado com o processo arame tubular (FCAW) robotizado, com três diferentes níveis de energia de soldagem. Para tal foram utilizadas técnicas de metalografia óptica e microdureza Vickers (Hv). Foram depositados cordões de solda em forma de camadas sobre chapas do aço X80, variando a energia de soldagem e sem pré-aquecimento, no estado como soldado. Os resultados mostram que a técnica de sobreposição utilizada, com baixa e média energia de soldagem, não foi suficientemente adequada para melhorar as propriedades metalúrgicas dos cordões depositados anteriormente, inclusive da ZTA do metal de base.Os cordões depositados com alta energia de soldagem promoveram crescimento do tamanho de grão da GGZTA do aço X80 com a consequente diminuição da resistência ao impacto.Este trabalho da subsídios para uma melhor compreensão das soldas multipasses.

Aug 16, 2017

By Akinobu Kasami, Keiji Maeda, Makoto Naito, Masaharu Toyama

Gap electroluminescent diodes have been prepared by the vapor phase diffusion of zinc into n-Gap crystals which were grown from a gallium solution (10 wt pct Gap) doped with tellurium and Ga203. A marked improvement in the efficiency of the red electrolumines -cence has been achieved by heat treatment after diffusion. External quantum efficiencies of diodes annealed under optimum conditions are 0.2 to 0.6 pct at room temperature, or about 200 times higher than the efficiencies of diodes quenched after diffusion. The optimum dopant concentrations in the gallium melt from which the crystals were grown are 3to6 x at. pct Te and 4 to 8 x 10-2 mol pct Ga203. The efficient diodes are characterized by linearly graded junctions with an i-layer 0.1 to 0.2u thick. Annealing increases the emission intensity by a factor of 20 to 50 and decreases the current density to 1/3 to 1/8 that of quenched diodes at a given bias. The decrease in current is attributed to an annihilation of deep recombination centers in the depletion layer. The increase in emission intensity is interpreted in terms of an increase in lifetime of minority carriers and an increase in the relative intensity of red-to-infrared emission. The dependence of these quantities on the tellurium and oxygen doping levels is also discussed. A number of studies have been made of the red light emission from for ward-biased Gap diodes.' At room temperature this emission band is centered at 7OOO? with a spectral width of nearly 1000?. Low-tempera-ture photoluminescence indicates that this emission is due to either the radiative annihilation of an exciton bound to a pair of zinc and oxygen atoms substituting on nearest neighbor lattice sites2,3 or the radiative recombination of an electron bound to this Zn-O pair with a hole bound to an isolated zinc shallow acceptor.3 An emission band is also observed with a spectral peak at 9800?. This infrared emission has been shown to be due to the recombination of an electron trapped at an isolated oxygen deep donor with a hole trapped at an isolated zinc acceptor.4 The red emission from Gap diodes is fairly efficient at room temperature because the nearest neighbor Zn-0 pair forms a deep electron trap at 0.3 to 0.4 ev below the edge of the conduction band.2'4 In diodes grown by liquid epitaxy an external quantum efficiency of 2.1 x 10-2 (photon/electron) has been attained by heat treatment at relatively low temperatures.5 This heat treatment was found to increase the efficiency by a factor of 3 to 6. However, no detailed studies have-been reported on the effects of heat treatment. We can only cite Onton and Lorenz's work6 on the change ; in the relative intensity of red-to-infrared emission. Heat treatment has also been tried on junctions built in during growth, but contrary to expectations the efficiency decreased. In-diffusion is a simple and controllable method of fabricating p-n junctions. For Gap, zinc is generally used to form a p-type layer on n-type crystals. The emission efficiencies of in-diffused diodes are, however, extremely low in comparison with liquid epitaxial diodes.' Although efficiencies as high as 2 x 1O-3 have been reported, values from 10-6 to 10-4 are generally obtained by typical diffusion techniques. Out-diffused diodes are known to be a little more efficient than in-diffused diodes. Nevertheless, the quantum efficiency is at most 7 x 10- 3 and ordinarily of the order of 10-4.8 NO results have been reported on heat treatment of either in-diffused or out-diffused diodes. This paper reports a marked improvement in the efficiency of the red emission observed for in-dif-fused diodes as a result of heat treatment after diffusion. The method described reproducibly yields diodes with external quantum efficiencies of 2 to 6 x 10-3. The observed dependence of efficiency on annealing time and on doping level will be discussed in terms of the lifetime of minority carriers and the formation of Zn-O complex pairs. EXPERIMENTAL A) Diode Fabrication. The n-Gap crystals used in this study were grown from a saturated gallium solution by a slow cooling method.8 The Gap content in the gallium melt was fixed to 10 wt pct corresponding to a growth temperature of about 1100 Tellurium was chosen as the n-type dopant and added to the melt in concentrations ranging from 0.001 to 0.06 at. pct. Oxygen was added in the form of Ga2O3, whose concentration was varied from 0.004 to 0.2 mol pct. The resulting crystals were platelets with well-developed (111) surfaces. Typical electrical properties were Hall mobilities of 130 to 30 sq cm per v-sec and carrier concentrations of 1016 to 10" cm-3 at room temperature. Diodes prepared from crystals with relatively low doping levels, in which u = 130 to 100 sq cm per v-sec and n = 0.6 to 6 x 1017 Cm-3, were examined in detail. The p-n junctions were produced in these n-Gap crystals by the diffusion of zinc from the vapor phase by the following procedure. The platelets were carefully lapped on both sides to a thickness of 150 to 200 u while maintaining the (111) orientation. After being etched in hot aqua regia, the crystals together with the zinc were sealed in an evacuated 12 mm ID quartz ampoule 20 cm long. The crystals and the zinc were then separated from each other at opposite ends

Jan 1, 1970

By D. F. Malan, Y. Jooste

"SynopsisScattered mining was practised on Kusasalethu Mine (previously Elandsrand Gold Mine) prior to 1998, but at deeper mining levels it was no longer feasible, since it would have resulted in unacceptably high stress levels and energy release rates. Longwall mining was not adopted at these depths as the mine required a more flexible mining method owing to the highly variable grade and the presence of geological structures. A mining method was developed that consisted of dip stabilizing pillars for regional support, as well as bracket pillars to clamp geological structures. A strict sequence of extraction was followed and this, together with the particular layout, was called the ‘sequential grid mining method’. This method addressed two key problems, namely negotiating adverse geology and the erratic grade of the Ventersdorp Contact Reef (VCR) orebody. However, a significant drop in production rates resulted in the need for alternatives and improvements to the original mine design. Modifications to the design were proposed in order to increase production rates, and an investigation to consider the rock engineering implications of these modifications was conducted. The study indicated that the modified method, called the ‘multi-raise mining method’, appears to be feasible and might address some of the production problems that were experienced with the original sequential grid design. An analysis of actual seismic data showed no significant differences between the original sequential grid mining and the implemented multi-raise mining. The numerical modelling of the mining layouts showed slightly higher interim energy release rates (ERRs) and average pillar stress (APS) levels during the extraction process. The final values are nevertheless identical to that of the original sequence. The study also investigated the use of a modelled moment method to analyse future seismic trends. The study illustrated that the expected seismic trends will be very similar for the multi-raise method compared to the original sequential grid mining method. This study is nevertheless considered of a preliminary nature and ongoing monitoring and analysis of seismic data at the mine is required to verify the response of the rock mass to the modified sequence and increased extraction rate. In particular, future work needs to investigate the effect of mining rate (advance rates in individual panels as well as volume of mining in particular raise lines) on the level of seismicity."

Jan 1, 2015

By K. Mondal

A macroscopic approach integrated with microscopic analyses for wettability characterization is presented. Wetting depends on 1) Contact between the dust and the fluid droplets, 2) Wettability of the particles by the wetting fluid, and 3) Wettability rate (due to low contact times). The goal of this paper is to show that the wetting rate is a significant factor in dust control. Samples from the roof, three different horizons of the coal seam and the floor were pulverized to less than 25 µm. Experiments were conducted with known wetting fluids to correlate surface tension and equilibrium wettability. Further analyses were performed in terms of surface charge (zeta potential), particle size, mineral composition, elemental composition, and quartz content. The surface tension reduction was also achieved by the use of chemicals and/or altering the temperature of the water. Two methods were used to evaluate wettability rates: a) near real-time comparison of wettability rates, and b) comprehensive evaluation of the intrinsic wettability rates. The data obtained provides meaningful insights towards the design of engineering controls for an economical solution to dust control in coal mines.

Jan 1, 2012

By Samuel Hoyt

SOME of the more important properties of finished materials are strength, ductility, toughness, resistance to alternating and repeated stresses, etc: Of these, the property that appears to have received the least consideration, at least in this country, is toughness, which is clue, possibly, to our regarding toughness as a qualitative property or, at any rate, as one that, parallels ductility. This arises out of our greater experience with the simple carbon steels in the rolled or forged (non-heat-treated) condition which, qualitatively, are tough if ductile and are not tough if brittle. In this way we have erroneously become, accustomed to judging the toughness of a material from its behavior in the tensile or similar test. The point of view presented in the present paper is that toughness, like hardness or tensile strength, should be regarded as an independent property and of sufficient importance to require, in so far as that may be possible, quantitative determinations. If such be true, it becomes at once necessary to devise experimental means for measuring, or valuating toughness, and the notched-bar impact test (the Charpy test) is advanced as the most logical test that has so far been developed for this purpose. It is further advanced, with particular emphasis, that we have two kinds of toughness to deal with and, accordingly, they will be dealt with independently. CLASSIFICATION OF MATERIALS ACCORDING TO TOUGHNESS Toughness has been defined somewhat as follows: Tough materials are those that offer considerable resistance to permanent deformation but which, once such resistance has been overcome, may' be deformed plastically, but only by the expenditure of considerable energy. In other words; tough materials may be deformed plastically but they absorb a considerable amount of work in the process. This kind of toughness may be called "static" toughness when the rate of loading is reasonably slow or "dynamic" toughness when the rate of loading is

Jan 2, 1919

By M. Cohen, R. T. Howard

It has long been realized among metallurgists that a fast, reliable method for the quantitative determination of the percentage of microconstituents in an alloy would be of great benefit in studies of equilibrium and transformation in the solid state. For example, Polushkinl has shown that the compositions of two coexisting phases in a binary system at a given temperature may be calculated very simply with the aid of two alloys lying in the two-phase field if the relative amounts of the two phases in each alloy can be determined. Recently, Grange and Stewart2 have traced the course of the austenite-martensite reaction in a series of commercial steels by making visual estimates of the percentage of martensite formed as a function of cooling temperature. The correlation of mechanical properties with structure, a subject of wide-spread current interest, is likewise dependent upon quantitative microanaly-sis. Yet, there are very few investigations described in the metallurgical literature, wherein methods of quantitative microscopy are employed. Usually, the relative amounts of the microconstituents are estimated in a qualitative or semiquantita-tive way. The authors were faced with this problem some time ago in studying the kinetics of austenite decomposition. Several aspects of this research could not be treated satisfactorily by other quantitative tools, such as specific volume,' magnetic,6 dila-tometric, electrical resistance7 or x-ray measurements.a It became necessary to find an impersonal quantitative method that could be applied to microstructures. Fortunately, it was noted that geologists and petrographers had coped with quantitative microscopy to a considerable degree in their attempts to evaluate the mineral contents of rocks. A number of excellent articles were found on this subject, and since they appear to be unknown generally to many metallurgists, the first part of the present paper is concerned with a review of the literature in some detail. With this survey as a background, the authors have adapted the so-called methods of point-counting and lineal analysis to metallography, as described in the second part of the paper. Austenite-martensite structures were selected for illustration not only because they are important in many ways, but because such fine intermixtures are notoriously difficult to estimate visually. Literature Survey Perhaps the earliest work on quantitative microscopic analysis goes back to Delesse9 (1848) who proved mathemati-

Jan 1, 1948

By M. Cohen, R. T. Howard

It has long been realized among metallurgists that a fast, reliable method for the quantitative determination of the percentage of microconstituents in an alloy would be of great benefit in studies of equilibrium and transformation in the solid state. For example, Polushkinl has shown that the compositions of two coexisting phases in a binary system at a given temperature may be calculated very simply with the aid of two alloys lying in the two-phase field if the relative amounts of the two phases in each alloy can be determined. Recently, Grange and Stewart2 have traced the course of the austenite-martensite reaction in a series of commercial steels by making visual estimates of the percentage of martensite formed as a function of cooling temperature. The correlation of mechanical properties with structure, a subject of wide-spread current interest, is likewise dependent upon quantitative microanaly-sis. Yet, there are very few investigations described in the metallurgical literature, wherein methods of quantitative microscopy are employed. Usually, the relative amounts of the microconstituents are estimated in a qualitative or semiquantita-tive way. The authors were faced with this problem some time ago in studying the kinetics of austenite decomposition. Several aspects of this research could not be treated satisfactorily by other quantitative tools, such as specific volume,' magnetic,6 dila-tometric, electrical resistance7 or x-ray measurements.a It became necessary to find an impersonal quantitative method that could be applied to microstructures. Fortunately, it was noted that geologists and petrographers had coped with quantitative microscopy to a considerable degree in their attempts to evaluate the mineral contents of rocks. A number of excellent articles were found on this subject, and since they appear to be unknown generally to many metallurgists, the first part of the present paper is concerned with a review of the literature in some detail. With this survey as a background, the authors have adapted the so-called methods of point-counting and lineal analysis to metallography, as described in the second part of the paper. Austenite-martensite structures were selected for illustration not only because they are important in many ways, but because such fine intermixtures are notoriously difficult to estimate visually. Literature Survey Perhaps the earliest work on quantitative microscopic analysis goes back to Delesse9 (1848) who proved mathemati-

Jan 1, 1948

By Robert T. Howard, Morris Cohen

IT has long been realized among metallurgists that a fast, reliable method for the quantitative determination of the percentage of microconstituents in an alloy would be of great benefit in studies of equilibrium and transformation in the solid state. For example, Polushkin1 has shown that the compositions of two coexisting phases in a a binary system at a given temperature may be calculated very simply with the aid of two alloys lying in the two-phase field if the relative amounts of the two phases in each alloy can be determined. Recently, Grange and Stewart2 have traced the course of the austenite-martensite reaction in a series of commercial steels by making visual estimates of the percentage of martensite formed as a function of cooling temperature. The correlation of mechanical properties with structure, a subject of wide-spread current interest, is likewise dependent upon quantitative microanalysis.3 Yet, there are very few investigations described in the metallurgical literature, wherein methods of quantitative microscopy are employed. Usually, the relative amounts of the microconstituents are estimated in a qualitative or semiquantitative way. The authors were faced with this problem some time ago in studying the kinetics of austenite decomposition. Several aspects of, this research could not be treated satisfactorily by other quantitative tools, such as specific volume,4 magnetic,5 dilatometric,6 electrical resistance7 or x-ray measurements.8 It became necessary to find an impersonal quantitative method that could be applied to microstructures. Fortunately, it was noted that geologists and petrographers had coped with quantitative microscopy to a considerable degree in their attempts to evaluate the mineral contents of rocks. A number of excellent articles were found on this subject, and since they appear to be unknown generally to many metallurgists, the first part of the present paper is concerned with a review of the literature in some detail. With this survey as a background, the authors have adapted the so-called methods of point-counting and lineal analysis to metallography, as described in the second part of the paper. Austenite-martensite structures were selected for illustration not only because they are important in many ways, but because such fine intermixtures are notoriously difficult to estimate visually. LITERATURE SURVEY Perhaps the earliest work on quantitative microscopic analysis goes back to Delesse9 (1848) who proved mathemati-

Jan 1, 1947

By J-S Zhang

In this paper, the author briefly introduces the resource characteristics of Chinese iron ore, as well as the present increasing market demand for iron concentrate. The SHP-3200 wet high-intensity magnetic separator (HIMS) is used to separate complicated weak-magnetic iron ores being composed of specularite, limonite and siderite in Jiuquan Iron and Steel (Group) Co Ltd. Some technologies have been used to improve SHP-3200 HIMS, including modifying the angle of magnetic polar from 90¦ to 83¦, cooling the exciting coils by oil instead of air, adding reverse-washing equipment to wash off magnetic particles and adjusting the tooth-space of the matrix from 5.0 mm to 3.5 mm or 2.5 mm to enhance the recovery of fine particles. It is still difficult to meet the requirement for recovering more difficultly separated iron and the demands for high-grade concentrate of iron. In order to improve the recovery of difficult-separated iron, the film-magnetic separation technique is applied into the HIMS and a new LY matrix is designed to form magnetic gradient vertically. A flowing-film feeder is also added and the feed mouth is modified to make a slurry flow formed in the form of film along the wall of matrix. The microstructure and dissemination character of the mineral particles is studied, and the specific susceptibility of the primary minerals is measured. Then the distributive characteristics of a magnetic field for the separator with film-magnetic technique and the motion of particles in the process of separation are all analysed. By introducing the film-magnetic separation technique to SHP-Φ700 HIMS, the recovery of iron can be raised from 69.45 per cent to 76.07 - 78.96 per cent with the similar grade of concentrates of iron. Such an increase of 9.51 per cent in the recovery also shows that it is feasible for such film-magnetic separation technique to be applied into HIMS.

Jan 1, 2005