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By H. C. Hamontre

The liquid-level gage described in this report is an instrument designed to locate liquid levels in wells rapidly and accurately and, with auxiliary equipment described, to follow moving liquid levels automatically. The depth at which the instrument makes contact with the liquid in a well is indicated at the surface by a depth meter on the cable to which the instrument is attached. When the gage is used to follow a surging moving level, the liquid depth is indicated continuously at the surface. This report contains a description and illustrations of the gage and outlines the operating procedures. The instrument is 1-3/4 inches in diameter and approximately 6 feet in length and may be operated through 2-inch tubing. The gage consists essentially of a float that moves upward with respect to the rest of the assembly, causing a change in the flow of electric current from the surface when the liquid level is reached. The instrument has been tested under a variety of conditions and has been found to be sensitive to changes in liquid level of 1/2 inch. Its accuracy is limited principally by the accuracy of the wire-line depth indicator used. It is not affected by pressure or temperature, and it can be run in open hole or under pressure through a lubricator. It employs only one electric circuit and can be run on an Amergraph single-conductor cable (type 1-H-0) ,

Jan 1, 1954

By A Gerson, S Miller, R Smart, J Thomas

Environmental Geochemistry International (EGi) and the Ian Wark Research Institute (IWRI) collaborated in a three-year Australian Minerals Industry Research Association (AMIRA) research project (Project Number P387A) focussed on the prediction and kinetic control of acid mine drainage. As part of this project, single addition, and sequential net acid generation (NAG) testing was carried out on sulfide mineral samples. The test samples comprised a range of synthetic waste materials prepared using a quartz bulk and controlled quantities of the commonly occurring sulfide minerals; pyrite (FeS2), pyrrhotite (Fe7S8), arsenopyrite (AsFeS), chalcopyrite (CuFeS2), chalcocite (Cu2S), covellite (CuS), bornite (Cu5FeS4), galena (PbS) and sphalerite (ZnS). NAG test results clearly show that there are significant differences between the acid forming potential of sulfide minerals. The NAG test results for each mineral were compared with theoretical acidity values (NAPP*). The NAPP* calculation was based on stoichiometric oxidation reactions assumed for each of the sulfide minerals. Sequential NAG values for pyrite corresponds closely to predicted NAPP* values, confirming the assumption that pyrite oxidation occurs according to the stoichiometry assumed. For the pyrite sample with 5 wt per cent S, two NAG stages were sufficient for all of the sulfur to be released to solution. Since sulfides in waste materials will generally be dominated by pyrite, results also confirm the validity of including NAG testing for ARD evaluation of most waste rock. NAG testing confirms that of the sulfide minerals examined, only pyrite, pyrrhotite, arsenopyrite and chalcopyrite are acid producing, ie able to produce leachate with a pH less than 4.5. In the case of sphalerite, galena, bornite, chalcocite and covellite the pH of the final NAG solution was greater than 4.5. The significant differences between the acid forming potential of different sulfide minerals could lead to overestimation of acid producing potentials based on NAPP values calculated from total per cent S alone, ie assuming all S is present as pyrite. The oxidation of galena during the NAG test resulted in the consumption of acid. The examination of the galena surface by X-ray photoelectron spectroscopy (XPS) after oxidation in peroxide solution indicated the presence of polysulfide. The reaction of sulfide to polysulfide is acid consuming, thus explaining the net acid consuming behaviour of galena in the NAG test. This reaction pathway may provide a possible explanation for the lower than expected acid production observed for some of the other sulfide minerals examined.

Jan 1, 2003

By Y. M. Ha, T. D. Nguyen, D. T. Nguyen, H. K. Choi

Conventionally, cement deep mixing (CDM) columns are designed to have constant diameters over the improved depth as this facilitates the construction procedures. However, this design pattern may be inefficient in cases of spread footings or shallow foundations. This paper first briefly introduces principles of an improved CDM method that can create head-enlarged CDM (termed PF) columns. A simple analysis approach was introduced to obtain optimal shape of PF columns that results in minimum settlement. The effectiveness of this improved method over the conventional CDM method was then illustrated by settlement analysis for an actual footing in a case study using two recommended analytical methods in the literature. Analysis results from the case indicated that by using the same amount of soil-cement mixed volumes, settlement from a footing on PF columns can reduce up to 10 % compared with that from the same footing on CDM columns. In addition, a material quantity comparison for the case indicated that to have the same settlement values the volume of each PF column can be reduced of around 10% compared with that of the CDM column. INTRODUCTION The cement deep mixing (CDM) method is one of the most popular methods in ground improvement works. Details on the method such as construction procedures, necessary equipment and recommendations are described in many references or manuals (e.g. Bruce et al. 2013, BS EN 2015, Kitazume and Terashi 2013). Conventionally, CDM columns are designed to have constant diameters over the improved depth as this facilitates the construction procedures. However, this design pattern is found inefficient in cases of spread footings or shallow foundations as the upper soil layers are naturally weaker than the deeper ones but are subjected to larger amount of induced stress from the superstructures.

Jan 1, 2019

By P. Prusti

An air dense medium fluidised bed separator (ADMFBS) is the efficient process for dry beneficiation of coal. Magnetite powder is used as medium to make required pseudo-fluid density in the fluidised bed. The dynamics behavior of coal particle with reference to its position changes from ideal solution to pseudo-fluid condition in different bed densities depending on its shape, size and density. In this study, three set of projected areas of coal particles were taken. Each set contains four different shapes i.e., cubical, rectangular prism, spherical and triangular prism with different density starting from 1.3 to 1.8 gm/cc. It is observed that coal particles having density less than the bed density, floats in different positions in the dense medium fluidised bed. Higher projected area particles float in deeper height in comparison with smaller projected area. The difference in position of coal particles in the bed increases (nearly 1 to 4 cm) as the coal density approaches towards bed density irrespective of the different shapes. Different shapes of coal particles behave in different ways based on the operating parameters like bed density, coal density and projected area of coal particle. Empirical model equations are proposed to predict the position of coal particle of each shape in the air dense medium fluidised bed system. Keywords: ADMFBS, particle dynamics, projected area, shape

Sep 1, 2012

By M. Tangstad

Keywords: Pyrometallurgy, ROMA, Norway, furnace, fines The ROMA project is a competence project on optimizing the usage of raw materials and energy in the ferromanganese, silicon, and aluminium industries. One of the items investigated in this project is the effect of fines on the furnace, and the usage of agglomerates versus lumpy ore. From lab-scale experiments it is shown, that for the charge to agglomerate in the furnace, the charge has to be exposed to a temperature higher than about 1200°C, independent of fines content. The fines less than 1 mm also showed higher agglomeration properties, compared to 2?4 mm, which showed no agglomeration property at all. The properties of agglomerates are very dependent on the pre-treatment of the agglomerate. Sinter and pellets, which have been heated to high temperatures, show a better strength, but also a lower CO reactivity. Sinter also shows a lower melting temperature compared to the ore.

Jan 1, 2011

By B. Surender Mohan

Mother Earth being a treasure of minerals, it is prime duty of the mankind to preserve this natural source to ensure steady growth of the nation. Utmost care is to be taken to see that these natural resources are explored and exploited scientifically in a sustained manner to ensure that the resource base improves and last longer. In this backdrop, the topic of ?Lignite - its resource and technology options to exploit deep seated deposits? is an apt subject to be deliberated upon in the present context, where the shallow deposits may slowly get dwindled. I shall deliberate upon the resource base of lignite, production profiles of the last five decades, consumption pattern, demand / supply projections, future available technology options to exploit the deep seated deposits, growth trends of the sector etc. in my paper. With the available resource base and future technology options, I can confidentially make a statement that ?lignite will remain as cocontributor along with coal to India?s energy generation and may well maintain its same status in the 21st century too, as it has been in the later part of the twentieth century?.

Aug 1, 2013

By M Singh, R C. Steinhaus, J J. Rust

Metallurgical process control systems in mineral plants often employ state-of-the-art monitoring analysers in an attempt to optimise plant operations and enhance mineral recoveries. These systems are unfortunately invariably fed by simplistic ‘sampling’ designs consisting of various in-stream methods or pressurised probes. These are unfortunate compromises and provide a false picture of what a mineral flotation or other process can achieve. The situation is further aggravated by some manufacturers using misleading marketing to suggest discrete cross-stream methods for metallurgical accounting and unreliable continuous in-stream off-takes for control sampling and that they are of synonymous integrity.Reliable, absolute or representative samples are often absent in many modern day concentrator plants, due to compromises around sample taking, particularly in terms of delineation and extraction errors and thus leading to sample bias. For more reliable information from online analysers we need a continuous, but much more reliable sample taken, than is current practice.Online analysers require a fully proportional and continuous supply of sample for effective process control, otherwise maximised or benchmark recoveries will be nothing but a pipe dream. Large discrete cross-stream samples from mechanically less reliable equipment cannot be used as feed to online analysers, as it will negatively impact real-time feedback and efficient process control.It is possible to build correct sampling systems that could do both process controls online and metallurgical accounting at the same time. Multotec Process Equipment (Pty) Limited, in close association with experienced sampling consultant Francis Pitard, have jointly patented a concept to achieve this and which is embodied in the design of the unique Rotating Cone® Sampler (International Patent Application No. PCT/IB2016/057464). This versatile unit for dry and wet applications has high division ratios via two-step sampling and division.A prototype was built and tested to validate the design and levels of precision achievable when employing the unit to split dry mineral fines or even certain foodstuffs.CITATION:Steinhaus, R C, Rust, J J and Singh, M, 2017. Does process control sampling always have to be a compromise?, in Proceedings Eighth World Conference on Sampling and Blending , pp 197–202 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2017

By Carlos A. Prato, Federico Pinto

"ABSTRACTThe design of drilled shafts often incorporates large factors of safety, for which settlements under service loads are highly influenced by the initial elastic stiffness. In the case of groups of drilled shafts with typical spacing, the elastic shaft-soil-shaft interaction dominates the behavior even for loads close to the bearing capacity, for which the initial stiffness is a key parameter in the design. This paper describes typical trends in results obtained by means of different approaches currently available in the literature for the evaluation of the initial stiffness of a single shaft. An experimental technique that provides a rapid and inexpensive means for the evaluation of the initial stiffness is described, and the results obtained for typical cases are compared with analytical predictions.IntroductionThe behavior of drilled shafts under axial loads is generally governed by the initial stiffness, as the factors of safety considered in design are often large, due to a superposition of conservative assumptions on soil properties and expected loads. In the case of shaft groups, the initial elastic stiffness plays a major role together with the elastic group effects, as nonlinearities tend to localize around the shafts and have a lesser effect than elastic deformations on adjacent elements (e.g., Leung et al., 2010). An accurate characterization of the initial stiffness is thus warranted for the analysis of drilled shafts and shaft groups under service loads.Initial stiffness of shafts may be estimated on the basis of soil stiffness and structural properties of the element by means of numerical methods (e.g., Pinto and Prato, 2006), as well as analytical methods (e.g., Randolph and Wroth, 1978). The soil stiffness may be determined by means of geophysical tests (e.g., Spectral Analysis of Surface Waves, SASW, Stokoe et al., 1994), or correlations with Standar Penetration Test (SPT) blowcounts or Cone Penetration Test (CPT) resistances (e.g., Sabatini et al., 2002).The initial stiffness may also be measured on drilled shafts by means of load tests. Static load tests (SLT), however, have some limitations on measuring small deflections, for which the initial stiffness is often extrapolated by means of large strain measurements (e.g., Chin, 1970), where the SLT measurements are more accurate."

Jan 1, 2014

THE CHAIRMAN (H. W. MORSE, Los Angeles, Cal.).-I would like to open this meeting for a little while to the general subject of leaching. We ought not to hold back if we have any new schemes for the future. I know that those of us who are tangled up with this lei thing work will appreciate any suggestions that will make us work harder and, scheme, harder to pull through these past difficulties on leaching. F. S. SCHIMERKA, Clifton, Ariz.-Under the direction of J. W. Bennie, General Manager of the Shannon Copper Co., Clifton, Ariz., 'it has been my valued privilege to cooperate in the elaboration of a hydrometallurgical process aiming at the recovery of copper in mill tailing resulting from a gravity concentration of a low-grade semi-oxidized sulphide ore occurring in a porphyritic gangue. The experimental work which has been carried on with a 25-ton plant is completed, and the company is building at present a leaching plant on a larger scale, the first unit consisting of a 150-ton roasting furnace and accessories for leaching the calcine.

Jan 12, 1916

Thank you for this opportunity to address your conference on 'The role of coal in the New Zealand energy market'. New Zealand's energy market has, in common with much of New Zealand, undergone major change following the market reforms of the Labour Government. As far as the energy sector is concerned this change has been for the better, as it has created for the first time in a very long time a 'true economic market' for energy in New Zealand. This is in marked contrast to the previous regime where: ò Electricity was state operated, subsidised and cross subsidised. ò Oil was imported and subject to a raft of taxes and duties. ò Coal produced by state mines was priced by cabinet committee, based on other energy prices rather than on the costs of production and delivery of the energy product. Today, with the establishment of the SOE's we have a market of competitive supply, where the customer has the choice of energy with prices based on the true costs of production and delivery. This can only be good for the customer as the cost is now based on the real costs of production, not on political whim. So where does coal fit in this brave new world of free market energy supplies? Well, opportunity, they say, knocks but once.

Jan 1, 1990

By Auhin Kumar Maparu

Metal oxide nano-particles are used as additives in various industrial applications such as pigments in paints, additives in adhesives, plastics, cosmetics, functional coatings, personal care and health care products, for antibacterial applications and more recently in heat transfer applications. In most of these applications, usually dry nano-particle powders are added to the formulations. However, often it becomes difficult to achieve a uniform and stable dispersion of nano-particles in the given formulation. Thus, a scalable and commercially viable process for in-situ production of stable nano-particles suspensions in the desired medium will certainly be more beneficial. Ultra-fine grinding in high energy mills (planetary mill, stirred media mill) has been used to produce fine particles (sub-micron size). However, in order to obtain nano-particles (particle size <100 nm), the choice of appropriate dispersant and solvent is crucial, since freshly generated nano-particles tend to agglomerate due to their high surface reactivity. We have employed molecular modeling (MM) based selection methodology to arrive at the most suitable solvent?dispersant combination for preparation of the given metal oxide nano-particles. Molecular modeling techniques are employed to compute the interaction energy of a given dispersant with surface of the metal oxide particles in the presence of the dispersion medium. The interaction energy helps identify a dispersant that has strong affinity for the metal oxide surfaces allowing for strong dispersant adsorption and hence a more stable dispersion. For example, in case of aqueous nano-titania suspensions, poly-carboxylic acids like citric acid provide better dispersion than mono-carboxylic acids like lauric acid, mysristic acid, and oleic acid. While in non-aqueous medium like ethanol, p-hydroxybenzoic acid and glycerol trioleate perform better. The suspension is produced in-situ by ultra-fine grinding of the metal oxide powder in the presence of the selected dispersant and dispersion medium in a planetary ball mill. By careful selection of various process parameters such as percent loading of powder, jar filling, grinding media to powder ratio, time and amount of dispersant addition, both aqueous and non-aqueous suspensions of metal oxide nano-particles with average particle size less than 100 nm are produced. The aqueous suspensions of alumina and titania produced in presence of citric acid dispersant exhibit median particle size of 83 and 62 nm, respectively. These suspensions have been found to be stable for nearly 3 years. The nano-particles thus produced are used in the preparation of nano-fluids?advance heat transfer liquids, which show enhanced heat transfer capabilities and unaltered stability and performance even after several heating-cooling cycles. The nano-particles are also utilized for making efficient photo catalysts, which are found to be highly effective under sunlight. Keywords: stability, nano-fluid, milling, grinding, thermal conductivity, nanocoolant, photocatalyst

Sep 1, 2012

By G. D. Rosales, P. F. A. Braga, S. C. A. França, C. P. Pinto

The growing market demand for lithium is mainly due to its use in the manufacture of batteries for electric or hybrid vehicles and portable equipment (smartphones, tablets, power tools, notebooks, etc.). Currently there is great interest in finding new sources of lithium and technologies for its utilisation. Li-S batteries have received attention due to their theoretically high specific energy density, which is 3 to 5 times greater than that of Li-ion batteries. Unlike Li-ion batteries, of which the main raw materials are lithium carbonate and lithium hydroxide, the main raw material for Li-S batteries is lithium chloride. The anode used in Li-S batteries is metallic lithium, produced by a molten lithium chloride electrolysis process. The extraction of lithium from pegmatites such as spodumene, previously abandoned in the 1990s for being uneconomical, has become attractive due to the increase in prices as well as the need for greater lithium purity of products made from lithium-bearing minerals. The main methods used for lithium recovery from spodumene ore include the sulfuric acid process, the alkaline process (lime or limestone as raw material) and the chlorination roasting process. Thermodynamic modelling using HSC software 5.1 was conducted to predict different reactions that could occur during chlorination roasting of the spodumene/MgCl2+CaCl2 system. Lithium extraction from the solid obtained after the chlorination roasting was also investigated. The results of thermodynamic analysis provided a better understanding of the chlorination roasting process for lithium extraction. Metallurgical tests with a mass ratio of 1:6 (spodumene:chlorides) and molar ratio of 2:1 (MgCl2:CaCl2) allowed over 95% recovery of the lithium contained in the spodumene concentrate. Keywords: Spodumene, lithium chloride, chlorination roasting

Jan 1, 2020

By A. H. Tousley, C. L. Vickers

The author presents a history of the development of the Port of Long Beach from its beginning in 1905 to the present construction of a new bulk loading facility. In describing this new facility, emphasis is placed on such aspects as rail car and truck handling, gravity yard, rotary car dumping, bottom dumping, car dumping equipment, feeding and conveying, ship-loader-stockpiler, stockpiling and reclaim, dust control, and construction problems. Development of the Port of Long Beach, Calif. (see Fig. I), began in 1905. In that year private Long Beach interests acquired 800 acres of marshland in the Inner Harbor area and initiated a program of channel dredging and land reclamation. Efforts to establish a municipal port began a short time later and culminated in the opening of Pier 1 in 1911. An event of even greater significance to the port future also occurred in 1911. This was the tideland grant enactment by the state legislature that conveyed to the city of Long Beach all of the state&apos;s rights in the tidelands located within the city boundaries. The grant stipulated that all revenue produced from the tidelands be used for the development of navigation, commerce, and fisheries. During the next 15 years up to 1926, the port&apos;s commercial growth was steady, although relatively slow. During this period, several fundamental steps in the development of a major harbor were accomplished. These included the creation of the Board of Harbor Commissioners in 1917, the dredging of the Inner Harbor and entrance channel to accommodate deep draft vessels, and the correction of a serious silting problem through construction of the Los Angeles River Flood Control Channel. These efforts bore fruit during the ensuing 10 years in the establishment of more than $30,000,000 worth of industrial plants and private marine terminals in the Inner Harbor. Commerce over municipal wharves also increased more rapidly, and it became necessary to start the development of the harbor in a seaward direction. In 1936, oil was discovered in the harbor area, and the first Harbor Dept. well was brought in 2 years later. It soon became evident that the city of Long Beach would receive substantial revenue that, under the terms of the state grant of 1911, must be used in the development of the port. It was further realized that to properly guide and coordinate such development, a long range comprehensive plan was essential. The Board of Harbor Commissions contracted with G. F. Nicholson and J. F. Collins, consulting engineers, for the preparation of such a report that was completed in 1940. The Nicholson-Collins report proposed the development of an East Basin, between the entrance channel and the Los Angeles River, and a West Basin in the area now occupied by the Long Beach Naval Shipyard. Twenty full-size berths were to be provided in the East Basin and more than fifty berths in the West Basin. The report recommended extensive modern terminal facilities for handling waterborne cargo. Attention was given to improvement of the street and highway system to give better vehicular access and to avoid congestion within the port. To a large extent the recommendations of the Nicholson-Collins report were followed in the subsequent development of the East Basin. This development was greatly accelerated by World War 11, with its need for increased oil production and additional shipping facilities. The wartime and immediate postwar construction was largely concentrated on Pier A, with the development of Piers B, C and D following in more recent years. An important factor in the planning of these piers was their dual function as oil drilling sites and cargo piers. The Navy&apos;s acquisition of the West Basin area made it necessary to depart from the Nicholson-Collins plan and find other areas for future expansion. At the present time only one Inner Harbor Port-owned area having protected deep water frontage remains undeveloped. This is the property fronting on Channel 2 in the Inner Harbor acquired in December 1957, from Pacific Dock and Terminal Co. The growth of the port has been in a southerly direction since the construction of the Long Beach Naval Shipyard in the West Basin area. Recent extension of Piers F, G and J into the ocean follows typical port construction methods developed during the expansion of the Middle Harbor during the last 20 years.

Jan 1, 1963

By D. G. Cerigo

"INTRODUCTIONAn interim report covering an uncompleted project on revenue mill optimization was presented at the invitation of Mr. C.S. Stevens, the Secretary of the Canadian Gold Metallurgists. The work described summarizes the preliminary work carried out at the Noranda Research Centre on computer mill optimization and is an attempt to arrive at a model of a circuit using the ""black box"" approach and hence by using economic factors related to concentrate dollar value to maximize revenue. The help and cooperation of Mr. J.D. Wild, Mr. M.J.S. Bennett of Noranda and Dr. A. Bobkowicz of McGill University is gratefully acknowledged.DERIVATION OF MODELHistorical data from the Normetal mill were used for the study. Normetal ore contains chalcopyrite, sphalerite, gold, silver, pyrite and pyrrhotite. For simplicity, data were chosen for days when only two concentrates had been derived, a copper concentrate which also contains the gold and silver, and a zinc concentrate. In these periods when pyrite concentrate was not produced, its circuit was used as an extra zinc scavenger unit. Figure I is a schematic drawing of the circuit and Table I explains the nomenclature.The mill had been operated to obtain a fixed grade of copper and zinc in the copper and zinc concentrates respectively, at the same time insuring acceptable recovery levels. The target grade for the copper and zinc concentrates had been derived by manual calculations based on past experience. The data used were 170 sets of daily mill reports, a sample of which is shown in Table II. The data consist of daily tonnages of feed, concentrates and tailings and their average compositions obtained by taking samples every twenty minutes from each stream and analyzing the daily composite samples."

Jan 1, 1967

By G. J. Hawkes

"We all know that every man who works for us should have a thorough knowledge and understanding of his responsibilities. But how about ourselves? Du we have a thorough knowledge and understanding of our own responsibilities as Mill Superintendents?I once had an occasion to say to a Manager that I did not know something was my responsibility and he replied with suitable emphasis ""Everything inside those four walls is your responsibility"". That makes the extent of our responsibilities clear but does not give us a check list to keep an eye on as we do our job from day to day.What are our responsibilities? I suggest they are the following:1. Developing and maintaining efficient operating and maintenance crews.2. Milling the required tonnage.3. Recovering the economical maximum amount of gold.4. Keeping costs at the economical minimum.5. Seeing that the figures are reasonably accurate for tonnages, assays, production, losses, and costs.6. Preventing accidents.7. Preventing fires.8. Maintaining the equipment and building and keeping them clean and tidy.9. Enforcing company rules and regulations."

Jan 1, 1965

By Keith A. Heasley, John L. Ellenberger

The National Institute for Occupational Safety and Health (NIOSH) has continued the research role of the former U. S. Bureau of Mines to develop techniques that will reduce the hazards in the mining work place associated with coal bumps. Current research focuses on both analyzing historical seismic data from bump-prone operations and utilizing a mine-wide seismic network to investigate the exact strata failure mechanics associated with bump-prone geology. The anticipated outcome of this research will be reduced bump incidences through advanced engineering concepts and designs which implement the new understanding of strata behavior. The analysis of the historic seismic data consists of correlating observed mining seismicity with the geologic and geometric parameters at the sites. The primary seismic parameters are the timing, location and magnitude of are corded seismic event. These parameters are correlated with such mining parameters as: the overburden, the size of the immediate gob, the size of the district gob area, etc. This detailed analysis of historical seismic data has provided an informative quantifiable relationship between many of the specific mining parameters and the induced seismicity. The second aspect of the coal bump research is the instrumentation of an appropriate field site to determine the main roof, floor, and gob behavior associated with bump behavior. The chosen field site is a deep-cover longwall mine with competent geology in a historically bump-prone area. The primary field instrumentation is a three-dimensional, full-waveform, seismic array with both surface and underground sensors surrounding an active multi-panel district. The purpose of this seismic array is to determine the timing, the exact location, and the mechanism (tensile fracture, bedding plane slip, etc.) of the failure of the strata surrounding the active and multi-panel gobs. The preliminary results presented in this paper help to define the strata failure areas around the longwall panel.

By J. H. Waxweiler, L. C. Ikenberry, R. J. Bendure

Carbon which is present as insoluble carbides in austenitic stainless steels can be measured quantitatively by dissolving the steel in iodine-methanol and analyzing the residue for carbon. Severe sen-sitization was observed in Type 302 due to precipitation of only 0.003 pet carbon. Both cold work and the presence of delta ferrite caused a marked acceleration in rate of carbide precipitation. Carbide precipitation rates in 17-7 PH were stzulied for the austenite conditioning and also the aging heat treatment. CARBON and its compounds exercise a major influence on the properties of stainless steels and their response to thermal treatment. Sensitization in 18-8 type stainless steels has been the subject of numerous investigations throughout the years. Bain, Aborn, and utherford," and Binder, Brown, Frankss all studied the effects of heating austenitic stainless steels in the temperature range of 1000° to 1500°F. The primary purpose of most of these studies was the investigation of susceptibility to in-tergranular attack in acids due to these sensitizing heat treatments. Intergranular precipitation of carbides was always associated with intergranular attack but it was recognized2 that severe attack could occur with but minute quantities of precipitated carbide. Mahla and ielsen utilized the electron microscope to make a significant contribution in illustrating the appearance and method of growth of chromium carbides during sensitizing heat treatments. However, as they stated, their studies of residues could not be used to obtain a quantitative measurement of the amount of carbon which was actually precipitated. The aim of the present investigation was to devise a relatively fast, simple method for the quantitative measurement of carbides in stainless steel. EXPERIMENTAL WORK The initial investigations were made to determine the best means of separating carbides from the matrix. A number of dissolving media were tried using both chemical and electrolytic attack. Qualitative examination of the extracted residues by X-ray diffraction indicated that solution in iodine-methanol would furnish a good means of separation. Consequently, further work was pursued along this line. The method is quite simple. The sample in the form of millings or nibblings is dissolved in iodine-methanol solution at room temperature (6-g iodine, 25-ml methanol per g of sample). The insoluble residue containing the carbides is separated by suction filtration through an ultra-fine glass filter disc. This is a very fine filter medium that will retain particles as small as 0.1 to 0.2 p in diameter. After washing with methanol and drying, the filter disc and residue are placed in a conventional combustion carbon-tube furnace and the carbon determined gravimetrically. Using this technique it was found that reproducible insoluble carbon values were obtained. However, since such small amounts of insoluble carbon were obtained on Type 302 after sensitizatipn at 1250°F and 1500°F, the values were confirmed by a second method. In the second method the sample was dissolved with copper potassium chloride and filtered through a millipore paper. This treatment dissolves the matrix but leaves undissolved practically all of the carbon irrespective of how it is present in the steel. The amount of insoluble carbon present as chromium carbide is determined by calculation from the analysis of the residue for chromium and iron. The derivation of the formula used for this calculation is discussed later. The values obtained by the indirect copper-potassium-chloride method were in agreement with those obtained by the iodine-methano1 method. See Table I. It should be pointed out that the sensitivity of the direct combustion method is not too high when the amount of carbide present is small. This is due primarily to inherent blanks and to analytical errors such as weighing. For this reason it cannot be stated with any degree of certainty that there is a significant difference between values of 0.002 and 0.005 pct. Having confirmed that the iodine-methanol extraction gave a quantitative measurement of the precipitated carbides in Type 302, exploratory tests were conducted on Armco 17-7 PH stainless steel. Samples from commercial Heat 54807 were solution annealed at 2000°F, water quenched and heated at 1250" and 1500°F, and water quenched. The analysis of Heat 54808 is as follows:

Jan 1, 1962

By N. B. Davis

I. Introduction. II. Definition of Plasticity. III. Theories of Plasticity. A. Structure of the clay particles. (1) Fineness of grain. (2) Plate structure. (3) Interlocking particles. (4) Sponge structure of particles. B. Presence of hydrous aluminum silicates. C. Molecular attraction between particles. D. Presence of colloidal gelatinous matter. (1) Review of theory of colloids. (a) Suspension colloids. (b) Emulsion colloids. (2) Experiments. IV. The Formation of Clays. A. Residual clays. B. Transported clays. V. Summary. VI. Conclusion. I. IntRodUction While working with a number of very sticky cracking clays from western Canada the writer became interested in a study of the cause of the excessive plasticity. This led to a review of the rather bulky literature on the subject and the finding that plasticity still remains to be satisfactorily explained. Most of these investigations seem to have been carried on solely from the chemical viewpoint, the geologic aspects having been ignored. In nearly every case, the investigators have worked with the higher-grade clays of low to medium plasticity, such as the kaolins, the excessively plastic ones having generally been neglected, partly because of their limited application, yet the author believes that these are

Jan 1, 1915

By W. Smith, F. G. Rinker, D. Beggs

Early in 1965 the Surface Combustion Division of the Midland-Ross Corporation was awarded the contract to engineer and construct a taconite pelletizing plant for the National Steel pellet plant, administered by the Hanna Mining Co., near Keewatin, Minn. This plant, which will have an annual capacity of 2,400,000 long tons, will produce pellets from magnetite concentrate using a new process developed through a joint research program by Midland-Ross, Hanna Mining, and the National Steel Corp. The work that culminated in the decision to construct this plant is the result of a research program for the development of the Midland-Ross heat fast process for the production of prereduced or metallized pellets. PELLETIZING PROCESS There are many acceptable methods for producing oxide pellets from ground iron ores and concentrates, and all of these give an acceptable product for blast furnace utilization. The vertical shaft furnace, the traveling grate, and the grate-kiln have been installed in many pelletizing plants in the northern hemisphere; therefore, the acceptance of these methods and the problems associated with them are well understood. However, this research project investigated a method for improving upon these processes to produce a high quality oxide pellet at a low operating cost.

Jan 9, 1966

By J. A. Kosek

Work has been conducted under Bureau of Mines Contract Number HO 357078 to develop instruments for detecting CO, NO and NO2 in a mine atmosphere, using fuel cell technology. The approach has been to optimize the fuel cell sensor configuration for the specific detection of CO, NO and NO2 in the presence of other mine gases utilizing recent advances in catalyst, electrode and solid polymer electrolyte membrane technology. Para-metric testing has been conducted on three electrode sensor cells to define performance and life characteristics as a function of temperature, feed flow and applied sensor voltage. Extended life testing has been performed on sensor cell configurations exhibiting favorable characteristics. Reliable, efficient gas sampling and electronic control circuitry has been fabricated for use with the sensor cells, and integrated into devices to meet the performance and design specifications for portable, battery-powered, hand held direct indicating gas detectors for use underground. Twenty of the production-type, direct indicating CO detectors have been tested and delivered to the Bureau of Mines under the present contract. Three prototype diffusion head CO monitors have also been delivered for evaluation under the pre-sent contract. The gas sampling pump and related parts have been replaced by a diffusion tube assembly in which CO reaches the sensing electrode surface by diffusion alone. In addition, delivery will be made of ten direct-indicating nitric oxide detectors and ten direct-indicating nitrogen dioxide detectors. These instruments are very similar in design to the direct indicating CO detector.

Jan 1, 1979