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By Yanagase T, Nakamura T, Ueda Y

The possibility of removing the phos phorus and sulphur contained in steelmaking slag has been studied by observing directly through the microscope melts heated on Pt- filaments. After a CaO crystal was placed in the molten slag, distributions of P, S and other elements formed around the CaO crystal were determined with the aid of EPMA. The results indicated that a layer of 2CaO SiO2 is formed on solid CaO in CaO-Si02 melts. Then between CaO and the newly formed compound the molten slag tends to migrate through cracks. For higher Fe 2 03 contents, the layers of the compounds 2CaO.Si02 and 3CaO SiO2 formed around the CaO crystal are not continuous but look more like particles, which promotes the dissolution of CaO. Phosphorus in slag was found to be enriched in the 2CaOòSi02 layer. Phosphorus in the 2CaO SiO2 phase is not related to the primary slag composition, being about 5-7% P205.. Sulphur in slag,as well as the phos- phorus,was concentrated in the 2CaO.Si02 phase. Disintegration due to weathering observed for slags produced in these investigations appeared to be due principally to hydration of lime.

Jan 1, 1980

By J. Loredo

The region of Asturias, located in the northwest of Spain, has an extensive mining history; coal, gold, zinc, lead, copper, cobalt, mercury, iron, manganese, fluorspar and others have been extracted from the antiquity. In the Asturian Central Coal Basin, the closure of all open pit coal mines and their restoration, the progressive closure of underground coal mines that is happening from the 1980?s, and the restoration of spoil heaps, provides post mining lands for alternative uses. In relation to metallic mining, the abandonment of all mercury mines without restoration in the 1970´s, has left significant quantities of wastes and mining works. More than thirty years later most of them remain without restoration. In these sites the legacy of the historical mining activities is apparent in the form of shafts, galleries and transversals, old mining installations and spoil heaps. Mine wastes have eventually become important Hg and As pollution sources, resulting in a widespread contamination of the surrounding soils and surface waters. Abandoned mines of other metals such as copper, cobalt, iron, etc. and industrial minerals such as fluorspar, have also left a mining legacy to take into consideration. In this context of declining mining areas, some remedial options have been applied to specific areas resulting in alternative uses as pastures, agro-forestry, industry and socio-cultural activities.

Jan 1, 2008

By J. Jordan, D. K. Denton, D. Tesarik, D. F. Scott, T. J. Williams

Personnel from the Spokane Research Laboratory of the National Institute for Occupational Safety and Health integrated the results of studies from a seismic tomographic survey, a finite-difference analysis, laboratory measurements of compression wave (ultrasonic) velocities in rock cores, and site geology to evaluate the use of seismic tomography for identifying induced pressures in an underground pillar at the Edgar Mine, Idaho Springs, CO. The key findings were that (1) the seismic tomograms showed that seismic velocities in rock adjacent to mine openings were low, (2) a difference tomogram in which in situ stresses on the east and west sides of the slot were compared showed that velocities increased west of the slot but decreased east of the slot, (3) geologic features (rock types and a fault) identified through geologic mapping were recognizable in the seismic tomograms, (4) ultrasonic velocity measurements on the rock cores agreed with seismic velocity measurements in the tomograms, and (5) results from a finite-difference analysis compared well to the seismic tomograms west of the slot but not east of the slot. The significance of this research is that seismic tomography is a useful tool for determining relative stress in underground pillars.

Jan 1, 2004

By D. S. Holmes

Biological processes for metal solubilization and ore beneficiation are in widespread use today. There are also some promising new applications of biotechnology in the areas of metal concentration and toxic metal cleanup. Recent progress in genetic engineering promises both to revolutionize the existing biological process and to expedite the adoption of the new biological applications. But before it can do so effectively, progress must be made in many areas of fundamental research and in biochemical engineering. These issues are addressed with special reference to the biotechnology of semi-enclosed containers (bioreactors), dumps, heaps, in situ and under- ground leaching, and with respect to the biotechnology of metal concentration. Finally, certain biological considerations for bacterial strain improvement are discussed.

Jan 1, 1987

By K. F. Bailey

Naturally occurring asbestos in aggregate and other mineral deposits, and the release of asbestos fibers into the ambient environment, is a public health concern. Determining the presence of asbestos in an ore body also presents a considerable sampling and analytical challenge. Improper and inaccurate identification of asbestos can result in unwarranted public and worker panic leading to significant costs to mine operators both in terms of dollars and company image. Some companies have been forced out of business simply because they had the non-asbestiform, prismatic variety of one of the six asbestos minerals. In the late 70’s, asbestos was found as a contaminate in a trap rock quarry in Rockville, Maryland. This discovery led to a massive overreaction by federal, state and local governments. In 1986, the Occupational Safety and Health Administration (OSHA) promulgated a final rule that regulated the common non-asbestiform mineral habits of actinolite, tremolite, and anthophyllite as if they were asbestos. The rule was reversed after a six-year struggle. Recently, the Libby, Montana, W. R. Grace vermiculite - asbestos, as well as the California chrysotile in serpentinite, and the New Jersey Southdown quarry – asbestos events have rekindled the entire issue of naturally occurring asbestos. It is time to get this concern addressed with sound science so that real asbestos is properly identified and controlled.

Jan 1, 2002

By Schulz R. S, Staunton W. P, McGuire J

The increased activity in the Australian gold industry over the last decade has resulted in a concomitant increase in the use of sodium cyanide, with a projected consumption of 80,000 tonnes per annum by 1991. Growing environmental awareness by government, industry and the public has generated increased interest in the fate of cyanide near gold mine tailings dams and has highlighted the lack of basic knowledge in this area, particularly for Australian conditions.

Jan 1, 1991

By Olga K. Karakasi, Angeliki Moutsatsou, Ioanna Kavallari

"The present study focuses on the amelioration of the behaviour of high calcium fly ash (HCFA), investigating its application in a new environmental field: oil spill clean up. High calcium fly ash is a by-product of electric power plants, produced annually in large quantities, whose greater amount is landfilled. Some of its properties, such as its chemical and mineralogical composition, its fine particle size, its porosity, floating ability and hydrophobic character make it an attractive material for this purpose. Researches showed that when added to an oil spill, it forms a semi-solid phase, which allows the quite total removal of the oil, but it is not stably retained on the surface. In order to ameliorate its floating ability, the decrease in its specific gravity by mixing with a lighter material is investigated. In the present study the mixing with two materials, already used in oil spill clean up, sawdust and a polymer, has been examined. Addition of 15-25% w/w sawdust to HCFA results in a material with better performance than HCFA or sawdust alone: it has a satisfactory floating ability and allows total removal of oil. Addition of the polymer, however, has resulted in no significant amelioration of the oil sorption behaviour of HCFA, probably because no affinity between HCFA and polymer has been achieved.IntroductionCoal fly ash is a by-product of coal combustion in electric power plants, produced worldwide in huge quantities, approximately 500 million tones annually. High calcium fly ash (HCFA) is classified to class C presenting a (Al2O3 + SiO2 + Fe2O3) > 50%. The production of lignite fly ash in Greece comes up to 13 million tones annually, of which only 12% is used in construction applications, the other being landfilled [5, 6].Besides its limited application worldwide as a construction material, research is focusing on the development of new environmental applications, such as waste stabilisation and solidification, soil and water environmental improvement [9, 12]. For the application of fly ash in further environmental fields several chemical modifications have been applied, in order to improve its properties. Extensive research has been focused on the conversion of both coal and lignite fly ash to zeolite and its further application in environmental field, such as the uptake of inorganic (heavy metals and ammonium [8, 11]) or even organic compounds (methylene blue [15]) from waste water streams, or the use as molecular sieves, to adsorb water molecules, SO2 and NH3 from gas streams, due to the high cation exchange capacity and porosity of the produced zeolithic material. Furthermore, lignite fly ash has been combined with sodium silicate solution, prepared by treatment of rice husk ash, and tetrapropylammonium bromide, to synthesise hydrophobic zeolite ZSM-5 [4]."

Jan 1, 2008

By Wiechers HNS

In China the hydrogeological type of solid mineral deposits can be divided into A. Mineral deposits with fissure water; B. Mineral deposits with pore water; and C. Mineral deposits with karst water. The hydrogeological conditions of mineral deposits with fissure water are relatively simple with the exception of a few cases. Mineral deposits with pore water are few but great amounts of ground water can be encountered in the mine accompanied by floating sand or slope failure during the exploitation. Mineral deposits with karst water are complex in their hydrogeological conditions. Enormous inrushes occur frequently in the mines of north China; Karst collapses are a serious matter in the mines of the south; Subterranean river and conduit systems are often encountered in the southwest. This paper will give full discussion on these features and put forward a way of combating and controlling the groundwater problem in accordance with type and feature.

Jan 1, 1988

By Robert S. Moehlman

Is recent years, exploration and development by diamond drilling has become a popular attack on the problem of finding new ore shoots and developing extensions of known shoots. Diamond drilling has been used in recent years in extensive sampling of disseminated copper deposits, in preference to churn drilling. At the Harvard gold mine, near Jamestown, California, Philip R. Bradley, Jr., general superintendent, reports that: "The Harvard work was a singular example of the reliance that can be placed on diamond drilling in evaluating an ore body." Drilling at the Harvard mine will be discussed in a subsequent section of the paper. So popular has diamond drilling become, indeed, that many who have had slight experience with drilling are inclined to regard it as a cheap cure-all. This paper proposes to show some of the limitations on the application of drilling and some of the steps that should be followed in drilling programs to obtain reliable results. Cost oF Drilling Drilling has the advantage, over shaft sinking and drifting, of lower cost and greater speed. As compared with churn drilling, the advantage of bringing up a coherent sample instead of fine cuttings for a sample is obvious. Diamond drilling is generally more expensive, however, and more engineering effort is required in combining the average of core and sludge samples. Exploration of drift walls by hammer drills to a depth of less than 30 ft. is generally cheaper than diamond drilling, but beyond this depth the diamond drill is cheaper and more efficient. The principal factor in determining cost of drilling is the character of the ground drilled. Broken ground with many fissures is most expensive to drill. Hard ground is less of a problem with diamond drills than with ordinary machine drills. Hardness or softness affects only the speed of drilling. Caving, easily washed, sandy or clayey ground requires continual cementing and casing, which is the greatest cost problem. Thus, soft, incompetent ground is more costly to drill than hard, massive ground. Cost of drilling per foot in good to fair ground varies from less than $I per foot, achieved in some districts in Ontario, the Mother Lode, and Missouri, to $5 per foot in many western states. In bad drilling ground, costs may range from $5 to $15 or more per foot, thus approaching the cost of drifting. Other factors that increase the cost per foot are: I. Short total length of hole drilled, so that the cost of moving in crews and equipment must be spread over a relatively few feet. 2. Cost of drilling per foot increases with depth beyond about 500 ft.. as more time is consumed in pulling rods' 3. Cost of preparing drilling stations, getting air underground to stations? etc' 4. Inaccessibility and lack of water on the job make for higher costs.

Jan 1, 1946

By R. A. L. Black, J. E. Jennings

The problems of slope stability in open cast mines are examined. A criterion, the instantaneous stripping ratio, is suggested for use in the design of pit slopes and as an index of control at all stages of the exploitation of the orebody. This criterion may also be related to safety and to the maximizing of profits. Two approaches to safe design of slopes, one from the point of view of soil mechanics and the other from the point of view of rock mechanics, are described and critically compared. The effect on slope stability of the regional tectonic stress field is discussed. Explanation is given of the application of the Terzaghi effective stress concept to problems in both soil and rock environments, including possible effects when borehole deformation techniques are used to measure stresses in rock in situ. A company embarking on open cast mining is faced with two basic questions: 1) will the venture be profitable and 2) can it be carried out with safety? The two questions are obviously interrelated because both depend upon the slope angles adopted for the pit. The cost of open cast mining depends largely upon the stripping ratio, defined as the volume of overburden that must be removed to the volume of ore recovered. The steeper the slope angles, the more favorable the stripping ratio, but the stability of the slopes, and therefore the safety of men and materials in the pit, require that the angles be made relatively flat. Consequently, the design depends upon a compromise: the slopes must be steep enough to result in economical mining and flat enough to ensure safety. Today there is a world trend towards deeper mining by open cast methods. This is mainly due to the higher cost of underground mining and the lower cost of open excavation resulting from the introduction of large modern earth and rock-moving machinery. Deeper open cast mining has led to a very great increase in the volumes of wasted overburden, and much thought is being given to the considerable economic benefits which would result if pit slopes could be made steeper by even one or two degrees. The result has been an increasing interest in research into slope stability problems in the expectation that the application of scientific principles will provide solutions leading both to economies and to more predictable operation of the mines. In at least four places, the U.S., Australia, Western Germany and Southern Africa, comprehensive investigations are at present in progress, and it is the object of this paper to review some of the more important aspects of these programs. RELATION BETWEEN ECONOMY OF OPERATION AND SLOPE ANGLES The main object of any industrial enterprise in a free economy is to make a profit. In mining, where profits must be made from a wasting capital asset, a further definition of the profit motive is imposed, namely that the economic aim should be to maximize the total possible profit. But since profits deferred for a number of years are not as valuable as profits that are immediately available, it is usual to discount deferred profits at some rate of interest which reflects their current or present value in the hands of the investor. Thus, in mining the logical aim can be defined more closely still: to maximize the present value of the total future profits. In commercial terms the present value represents the market value of the operation as a going concern. Many factors enter into the forecast of current and future profits. They include the volume of production, the price of the salable product and the cost of production. Current profits can be estimated with reasonable accuracy by the operating engineers; but it is the task of economists and management to assess future trends in the mineral markets and in the economy as a whole, and together with the engineers, they can then estimate the future cost and profitability of the mining operations. In open cast mining, the rate of ore production once decided on remains a virtually constant factor unless a major change in the capital structure of the mine is made. But one factor over which the operator has a considerable measure of control is the ratio of the volume of ore mined to the volume of waste over-

Jan 1, 1963

IT is intended in this paper to present in broad outline to the members of the Institute a short account of the conditions and operations that constitute what is, variously known as Subterranean Warfare, Military Mining, or Tunnelling. Realizing ,the magnitude of the operations, and the varied and minute details met with in them on,the Western Front, it is the writer's intention to confine these notes to operations carried out by the First Australian Tunnelling Company. In so doing there is no wish to detract from the very fine records of the Second and Third companies it is to be hoped that members of the Institute (or others) who were with these companies will write accounts of their doings-the former in the water-logged areas to the south of Armentieres, and later in the sand-dunes at Lombardzee, and the latter in the chalk area of the Lens coal...

Jan 1, 1920

By Jaime Meléndez Martínez

Recent interest in unconventional reservoirs motivates our work in laboratory measurements of seismic anisotropy. Seismic anisotropy is the variation in speed of a wave as a function of its direction of propagation. Analyzing anisotropy in unconventional reservoirs is important since anisotropy leads, for example, to differential stresses upon loading and could affect hydraulic stimulation (Reinicke et al., 2010, Zimmermann and Reinicke, 2009); in this sense, laboratory measurements are an important tool to study seismic anisotropy at small scales which can aid in the characterization of larger formations. The purpose of this work is to describe the laboratory methodology used to simultaneously measure ultrasonic P and S-waves in three different directions from a single core sample. Elastic anisotropy of a Proterozoic sedimentary rock from south-west Alberta is investigated. In metamorphic rocks seismic anisotropy is caused by preferred mineralogical alignment or foliation. Assuming a transversally isotropic medium, arrays of compressional and shear piezoelectric ceramic transducers were mounted on a sample trimmed from a core to measure travel times of ultrasonic P-waves and S-waves as a function of confining pressure at directions perpendicular, parallel, and oblique to the plane of foliation (bedding). Results show strong anisotropy agreeing with the assumption of a transversely isotropic medium. Dependence of travel times and hysteresis effects can be observed when pressurizing and depressurizing.

Jun 1, 2012

By J. M. Wempen

Booster fans in underground coal mines are often located using the concept of a neutral point. Normally, intake airways are maintained at higher absolute pressure than return airways; therefore, air leaks from intake to return. By adding a significant pressure force to a region of a ventilation system, booster fans installed in a return airway can increase the pressure in the return so that air leaks from return to intake. This is commonly referred to as recirculation. The neutral point occurs at the location in the system where the pressure difference between [ ] the intake and the return airway is zero. At this point, there is no leakage or recirculation. Ideally, placing a booster fan near the neutral point minimizes leakage and recirculation. However, in practice, the position of the neutral point is not static and it changes as the ventilation system parameters change. Booster fans have the potential to increase the capacity and efficiency of coal mine ventilation systems. However, these fans add a significant pressure source to ventilation systems and can create areas where the pressure in the intake is less than the pressure in the return causing recirculation. In systems with multiple booster fans, there may be multiple recirculation paths and, as the capacity of these fans increases, recirculation is more likely to occur.

Jan 1, 2012

By R. F. Mehl, B. Lustman

THE formation of intermediate phase layers in cementation processes has been subjected to extensive qualitative investigation though to relatively little quantitative study; this work has recently been fully summarized by F. N. Rhines.1 It is necessary here only to enumerate the general conclusions drawn concerning the kinetic laws governing the growth of intermediate layers and to state what is known concerning the structural changes accompanying the generation of phase layers. I. When the intermediate phase is protective in type-i.e., when its density is less than that of the base metal, so that a continuous coating is formed and maintained-the isothermal growth of the phase follows a simple parabolic equation: [1 = ki [I]] where X is the thickness of the alloy layer, k the reaction rate constant, and [t] the time. The applicability of this equation to diffusion processes is tested by plotting the square of the thickness versus time, or by plotting the thickness versus the square root of time; the resultant achievement of a straight line in such a plot has been considered sufficient proof of the validity of this equation. Exceptions have been found where liquid phases are involved in the reaction, where the diffusion layer is cracked,2 and where thin semimetallic oxide and sulphide coatings are formed on metals.3 In the first two cases the thickness increases linearly with time, and in the latter it is a logarithmic function of time. 2. The rate of thickening varies with temperature according to the Arrhenius equation: [k = Ae-QIRT [2]] where k is the parabolic rate constant of Eq. I, or some other rate-descriptive function, A is the action constant, e the base of natural logarithms, Q the heat of activation, R the gas constant, and T absolute temperature. This equation has been found to be generally valid except when transformations occur during reaction in either the base metal or in the reaction layer; in such instances Eq. 2 is still applicable with different values for the constants A and Q above and below the transformation temperature. 3. All phases that are stable at the temperature at which diffusion occurs will appear in the interdiffusion of two components. In some cases certain of the phases may be too thin to be observed and identified easily. Nonequilibrium phases have never been noted in thick reaction layers; i.e., layers of a thickness that may be discerned microscopically. The relative thickness of each phase in a diffusion layer is proportional to the concentration gradient and to the rate of diffusion in that phase.4 The reaction layers tend to have a

Jan 1, 1942

By A. K. Mukherjee

In this apparatus closed sized particles are placed in a container and then fluidized by passing water through the load of particles. Water flow is adjusted to deposit particles in one or more layers depending on the specific gravity of each of the particles, after which the deposited particles are separated in portions of different specific gravity. The obtained portions represent different ore content of the closed sized fraction. The process is repeated for all other size fractions to generate washability curve of the feed. Three different types of iron ores and one coal sample are tested in this equipment. The theoretical yield-grade curve generated for iron ore feed is unique in absence of any such practice for ore minerals. Similar curve is generated for coal and it is compared with washability curve, an existing practice followed worldwide. This comparison validates the performance of the process and the equipment.

Sep 1, 2012

By I. R. Kramer

A delay time for yielding in cold-worked face-centered-cubic metals was found. Slip on (123) planes was observed. Glide on these planes occurred during the delay-time period before slip starts on the (111) planes. AN important approach to the study of the anchoring and blocking of dislocations is available through the delayed-yield phenomenon which has been observed in body-centered and hexagonal close-packed metal by several investigators. Clark and his associate1-5 showed that a delay time for yielding is present in mild steels and fine-grain molybdenum. Type 302 stainless, SAE 4130 normalized, SAE 4130 quenched and tempered, and 24s-T aluminum aid not have a delay time. Kramer and Maddin6 studied the delay-yield effect. in metal single crystals. While they found a delay time in body-centered-cubic metals none could be found in the face-centered-cubic metals. Later7 a delay time was found in hexagonal close-packed metals. cottrell8 has proposed an explanation for the difference in the yield phenomena of b.c.c. and f.c.c. metals based upon the anchoring of edge dislocations by the proper types of impurity atoms (C and N). In the body-centered-cubic lattice the interstitial atoms are near a cube edge and can interact with an edge dislocation, while in a face-centered-cubic lattice the distortion around an interstitial atom is of spherical symmetry and cannot anchor a screw dislocation which has practically no hydrostatic component. Cottrell's theory seems to account rather well for the behavior of body-centered-cubic . metals. EXPERIMENTAL PROCEDURE The apparatus used in these experiments is essentially of the same design as described previously.' Single crystals 1 in. long and having a diameter of % in. were placed in a pendulum which consisted of a bar 8 ft long designed with a crystal holder to accommodate the specimen at low temperatures. This portion of the apparatus was supported on fine molybdenum wires. A bar of the same diameter and length comprised the other portion of the apparatus. This bar was supported on a set of roller bearings arranged around the periphery of the bar to allow accurate alignment. This bar was propelled by means of a spring-loaded gun and allowed to strike the lead bar in front of the single-crystal specimen. SR-4 type A-8 resistance strain gages were cemented to the specimen and the strain measurements were obtained by amplifying the strain-gage output by means of a high-gain preamplifier. A tektronix 545 oscilloscope was used together with a polaroid camera to record the strain and time sweep. An Ellis Associate Bridge was used to calibrate the strain gages and calibration readings were obtained before each test. The sweep of the time signal was initiated by means of a miniature thyraton which was fired when the two bars came into contact. The single-crystal specimens were cut from single-crystal bars about 12 in. long, grown by a modified Bridgman technique. The aluminum crystals were made with material of 99.99 pct purity while the purity of the copper was 99.999 pct. A cut-off wheel was used to prepare the specimens which were then machined to the desired length. The two opposite faces of the specimen were parallel to each other and perpendicular to the axis of the specimen. The specimens were compressed 1 pct. No machining followed thereafter. In some cases prestraining was carried out in liquid nitrogen by impacting the specimens directly in the apparatus so that subsequent observations could be made without allowing the specimen to warm up to room temperature. The single crystals were compressed 1 pct at room temperature in a hand press without much control of the rate of deformation. In some cases specimens were recompressed to obtain the desired length change. As far as could be determined in these experiments this factor did not seem to influence the results. The SR-4 strain gages were glued with a cellulose type cement onto the specimen surface and baked at 45°C for 12 hr. As a check on the baking treatment gages were allowed to dry at room temperature. All delay time tests in this paper were conducted in a liquid nitrogen bath at -195°C. A schematic delay time oscilloscope trace is shown in Fig. 1. At point B the elastic stress wave caused by the impact reaches the strain gage on the specimen. The portion BC is the elastic strain. In this investigation the strain at point C was used to calculate the critical resolved shear stress by multiplying by the proper modulus depending upon the orientation of the single-crystal specimen. The time between C and D is the delay time portion of the curve. This portion of the curve is fairly flat but does have a definite microstrain associated with it. After the point D is reached the specimen deforms rapidly and the strain reaches a maximum at E. Following this, depending upon the length of the bar behind the specimen, the strain remains constant for a period and then decreases when the reflected elastic wave returns from the end of the pendulum bar. A permanent plastic strain is recorded on the oscilloscope trace and also measured by a strain-measuring bridge. The strain, E p,

Jan 1, 1960

By E. R. Spencer, E. R. Bauer

Previous studies and research efforts have shown that noise-induced hearing loss (NIHL) is a problem in the U.S. mining industry. In response, researchers at the National Institute for Occupational Safety and Health (NIOSH) have been conducting a cross-sectional survey of equip­ment noise and worker noise exposures in the mining industry to estimate the potential for NIHL within the mining community. One commodity recently surveyed was the extraction of sand and gravel from surface pits and by dredging. To address the potential for NIHL in the sand and gravel industry, sound levels on and around the dredges and processing equipment were recorded to iden­tify areas of high noise levels. Full-shift worker dosimetry, in conjunction with task observations, was documented to determine the relationship between exposure and source. This paper presents research examining noise on dredges used in several surface mine sand and gravel operations and in the processing facilities. Results indicate that there are areas on the dredges (crane, suction pumps and diesel engines) where sound levels greater than 90 dB(A) are pres­ent. In addition, crushers and screens used in the processing of the sand and gravel also generate sound levels greater than 90 dB(A). Although no surveyed worker exceeded the Mine Safety and Health Administration’s (MSHA’s) permissible exposure level (PEL) of 90 dB(A) eight-hour time-weighted average (TWA8), laborers, mechanics, oilers, helpers, pickers and greasers are the workers most likely to be exposed to hazardous sound levels and to thus develop NIHL over time

By J. Chipman, T. Fuwa

The effects of various elements on the activity coefficient of carbon in liquid iron have been studied by two experimental methods: 1) equilibration with controlled mixtures of CO and CO2; 2) the solubility of graphite in the melt. Activity coefficient of C is increased by Al, Co, Cu, Ni, P, Si, S, and Srz. It is decreased by Cr, Cb, Mn, Mo, W, and V. THE thermodynamic properties of the iron-carbon binary system have now been fairly well established, although some uncertainty remains with respect to the exact location of some of the phase boundaries. The activity of carbon in ferrite and in austenite has been measured in the classic researches of R. P. smith' while similar measurements by Richardson and ~ennis, and by Rist and chipman3 have established the values of the activity of carbon in liquid iron up to 1760°C. On the other hand, our knowledge of the effects of alloying elements on the activity of carbon in dilute solutions is restricted to Smith's experiments on systems Fe-C-Mn and Fe-C-Si in the austenitic range and to some more recent experiments of schwarzman4 in the a range. In addition there have been a number of determinations of the effects of various elements on the solubility of graphite in liquid iron, and from these the corresponding effect in saturated solution may be obtained. The purpose of the present study was to extend the investigation of the liquid system to include the effects of alloying elements upon the activity coefficient of carbon, principally in dilute solutions. Equilibrium measurements were made on the reaction C + co, = 2 CO (g) The prepared mixture of CO and CO,, diluted with argon, flowed over the surface of the liquid metal which, after several hours' exposure to the gas, was quenched and anqlyzed. As in the earlier experiments, the principal experimental difficulty was in the deposition of carbon on the parts of the furnace at temperatures slightly below that of the metal bath. In order to minimize this difficulty, the ratio (Pco)2 /PCo2 was restricted to values not much higher than 100 atm, and correspondingly the carbon concentration in the metal seldom exceeded 0.30 pct. EXPERIMENTAL METHODS The method and apparatus were essentially the same as used by Rist and Chipman.3 The gaseous mixture consisting of highly purified CO, CO,, and argon, each controlled by a flowmeter, was led into the furnace and passed over the surface of the liquid-iron melt which was heated and stirred by high-frequency induction. One slight modification was made in that a molybdenum susceptor was placed outside the crucible for the sake of uniformity of temperature and to combat the tendency of carbon to precipitate on the crucible wall. Pure alumina crucibles approximately 25 mm ID were used. The charge consisting of about 30 g was made up of electrolytic iron, the alloying element to be added, and enough graphite to supply slightly more or less than the anticipated equilibrium carbon concentration. All metals used were of high purity. Metallic chromium, columbium, and vanadium were from special lots supplied by the Electro Metallurgical Co. Tin, copper, molybdenum, tungsten, cobalt, and nickel were of purest commercial grades. The electrolytic iron, after being cut to the proper size for charging, was prereduced by hydrogen at 850° to 1000°C to remove surface oxidation. The oxygen content of the reduced material was 0.002 pct. This treatment made it easy to control the carbon content of the initial melt. The charge was melted under the gas mixture to be used for the entire run. In some earlier melts the charge was melted under a stream of argon, but in this case some alumina was reduced from the crucible, and the aluminum thus absorbed in the melt was subsequently oxidized with the formation of a solid film of alumina on the surface of the melt. AS another safeguard against film formation, overheating of the bath was carefully avoided. All runs were made at a temperature of 1560°C. Under experimental conditions a charge of pure iron picked up 0.17 pct C in 3 hr and 0.23 pct C in 6 hr under an atmosphere for which the equilibrium concentration of carbon is 0.27. It is clear that the time required to reach equilibrium from an initially carbon-free melt would be very great. For this reason each experiment was started with a melt of known carbon concentration not far above or below the expected equilibrium value, and each melt was held at temperature for a period of at least 5 hr. Under such circumstances it was possible to chart the approach to equilibrium from both high-carbon and low-carbon materials. Temperature was controlled by frequent optical observation and adjustment and the metls were timed in such a way that the final 2 hr occurred during a time when electric power was steady; for example, 2 to 4 pm or after 11 pm. In melts containine volatile metals such as copper, tin, and mangane\e the time of holding was decreased somewhat in

Jan 1, 1960

By Georg Keintzel

The origin and elimination of 3rd octave mill chatter is a frequently investigated topic since tandem cold mills are in operation. So far only chatter monitoring systems have been successfully deployed, but this implies speed reductions and therefore a significant loss in mill output. Primetals Technologies has developed a new system using active injection of damping in order to eliminate 3rd octave mill chatter. The new hydraulics-based ChatterBlock® Control has now been proven successfully in mill operation. 3rd octave mill chatter, typically occurring in a frequency range between 90 and 150Hz, is a self-excited vibration phenomena typically occurring in the rear stands of tandem cold mills. It can produce significant gauge variations and even cause strip breaks. 3rd octave mill chatter is characterized by a quickly diverging vertical vibration of the rolls for specific rolling conditions (material, mill speed, forces, gauge etc.). Its occurrence requires immediate speed reduction of the mill in order to avoid strip breakage and/or strip quality degradation. This phenomenon thus severely limits mill productivity. The first step to proof the industrial feasibility of the new system was its installation on stand no. 4 of a 5-stand tandem mill. The development process and first results of the industrial implementation will be presented in this paper.

Aug 16, 2017

By Andreu J. Ferrero

Polyurethane and acrylate resins are routinely injected into soils to gain strength and control water flow. However, most published data regarding strength gain is derived from laboratory samples created under ideal conditions. This study endeavored to inject resins into full scale mock-ups that could then be excavated and tested to yield results comparable to actual field conditions. To achieve this goal, a large container was filled with a silty SAND (SM), as defined by the Unified Soil Classification System (USCS). The soil was moisture treated and compacted in lifts of 0.3m. PVC pipes installed in a diamond grid into the soil were used to inject polyurethane and acrylate resins. Dynamic cone penetrometer (DCP) tests were conducted on the polyurethane treated soils, the acrylate treated soils, and the baseline untreated soils in the container. Testing results will be correlated to SPTn and CBR values to evaluate increases in the soil strength parameters in the treated soils. Cored samples of polyurethane and acrylate treated soils will be tested in compression, shear, and triaxial. These laboratory test results will focus on material property gains for the treated soils, in comparison to standard values for similar soil types. Complete documentation of the soil type, compaction methods, injection methods, and testing performed have been documented and will be presented in the final paper.