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By G E. Craig, W. M. Williams

A simple, easily constructed apparatus suitable for the zone refining of iron and other reactive materials is described. After eight passes at one inch per hour, the iron produced showed a marked drop in hardness to 49 Brinell. In addition, an arbitrarily -defined recrystallization temperature was lowered by about 35°C and the rate of grain growth greatly increased. CERTAIN materials, of which iron is one, are so reactive that they cannot be zone refined in any known container without becoming contaminated. For such substances, the floating zone method ( 1) may be used. In this method, the specimen is supported vertically in an inert atmosphere and the molten zone supports itself by its own sur-face tension. The method was first applied to silicon (2) and has since been used for other reactive metals such as zirconium and titanium. Smith and Rutherford (3) have previously reported on the floating zone refining of iron; the efficiency of the method for reducing the car-bon content was demonstrated on

Jan 1, 1962

By Ling Yang, John Henderson

Self-diffusion coefficients of copper in molten copper have been measured by the capillary reservoir method in the temperature range 1140o to 1260°C. The results can be represented by the equation D = [(1.46 * 0.01) x 10-3) exp [(-9710 * 710)/RT] cm2/sec. The energy of activation agrees within the limit of experimental uncertainty with that for viscous flow. The relationship between the diffusivity and coefficient of viscosity is best described by the equation D = kT/4pnr cm2/sec. MEASUREMENT was made of the self-diffusion coefficient of copper in molten copper in the temperature range 1413º to 1533ºK, using the capillary reservoir technique and CU64 as the radioactive tracer.The procedures for filling the capillaries, making the diffusion run and evaluating Dcu from the counting results were the same as described previously.1,2 All experimental operations involving the melt were carried out in a purified argon atmosphere. A graphite crucible, enclosed in a McDanel tube, was used as a container for the melt because of its satisfactory nature as a refractory material and the low solubility of carbon in copper. Graphite was also used for the capillary material. A McDanel thermocouple sheath, to which graphite radiation shields were affixed, was used to hold the capillaries. By moving this sheath through a rubber seal at the top of the McDanel tube, the capillaries could be lowered into or raised out of the melt. A Globar furnace with a constant temperature zone (± 2°C) of 2 in. was used to heat the assembly. The temperature of the furnace was the equilibrium value corresponding to a given setting of the transformer. Temperature was measured with a Pt-10 pct Rh/Pt thermocouple and varied during a run

Jan 1, 1962

By R. V. Mrazek, F. E. Block, S. B. Knapp

The mixed homogeneous and heterogeneous kinetics of the thermal decomposition of tungsten hexacarbonyl were studied by employing a batch reactor. The system was such that a sample of tungsten hexacarbonyl could be injected into the preheated reactor, and the progress of the reaction followed by a simple pressure measurement. Both the homogeneous and heterogeneous reactions were found to be first order, and approximate activation energies were determined for each reaction. It is shown that the dis-proportionation of carbon monoxide to give carbon and carbon dioxide cannot be the source of carbon in tungsten deposits prepared by this reaction. The kinetics of the thermal decomposition of tungsten hexacarbonyl have been investigated as part of a continuing study by the U.S. Bureau of Mines on the decomposition of organometallic compounds. Reactions involving the thermal decomposition of metal carbonyls have a potential application in the preparation of pure metals and fine metal powders. Indeed, it was these applications which provided the impetus for much of the early work involving the carbonyls of nickel1 and iron.' The relative lack of study of other metal carbonyls can be traced to the comparative difficulty in synthesizing these compounds. The most common use for tungsten hexacarbonyl has been as an intermediate in vapor-phase plating.7'8 However, attempts to obtain a carbon-free deposit of tungsten by this method have not been successful, and some investigators have taken advantage of the carbon contamination and used this process to form tungsten carbide deposits.lo Other investigators have studied the thermodynamic properties11"14 and molecular structure of tungsten hexacarbonyl. However, very little is known about the kinetics of this thermal decomposition, the mechanisms involved," or the source of carbon in the resulting plate. In contrast, studies have been made of the kinetics of the thermal decomposition of nickel tetracarbonyl, iron pentacarbonyl, and molybdenum hexacarbonyl.'l It has been found that these thermal decompositions occur by a mechanism which is partially heterogeneous in nature. Information available on the equilibrium constants for the decomposition of tungsten hexacarbonyl was used to determine a temperature range, 500" to 560°K, in which the reaction could be expected to be essentially complete. APPARATUS The apparatus used allowed the injection of a sample of tungsten hexacarbonyl into a preheated batch reactor and the use of a simple pressure measurement to follow the progress of the reaction in the sealed reactor. The pressure was sensed by means of a pressure transducer (Consolidated Electrodynamics Corp., 0.3 pct)* capable of operating at the *Reference to specific products is made to facilitate understanding and does not imply endorsement of such brands by the Bureau of Mines._______ reaction temperature. This type of sensing element was chosen to avoid the problem of condensation of the sublimed carbonyl in the capillary tubing leading to any type of remote pressure-sensing device. stirring was provided by rotating the entire apparatus. Glass beads placed in the reactor provided a pulsating agitation. To minimize thermal gradients in the reactor walls, the reactor was constructed of aluminum. The support tube which held the reactor in the furnace was thin-walled stainless steel to minimize heat conduction out of the reactor. As a result of these measures, a nearly uniform temperature (°C) was maintained throughout the reactor. Fig. 1 is a schematic diagram of the apparatus. The small gear motor rotated the entire apparatus at about 200 rpm. The bearings shown at the ends of the air cylinder were perforated to allow air to be fed to the charging piston and to allow inert gas to be fed to the reactor during the preheating period. The sample was simultaneously injected and sealed inside the reactor by operation of the air piston. Fig. 2 shows a cross section of the air cylinder and the adjoining portion of the support tube leading to the reactor. The sample carrier is shown in place at the right-hand end of the injection rod extending from the air piston. The piston is shown in the retracted position, as it would be prior to the start of an experiment. The small Teflon gasket which encircled the sample carrier at the end of the injection rod sealed the reactor when the sample was injected. This seal was maintained throughout the test by maintaining air pressure on the piston. The sample carrier was a 2-in. section of thin-walled, -in.-diam nickel tubing with an internal blank about 1 in. from the base and with the base end sealed.

Jan 1, 1969

By B. C. Jena

In a chromite smelting process for the production of high-carbon ferrochromium, the slag composition profoundly affects operating conditions and the economic performance of the process. For a Canadian chromite concentrate, optimum slag composition and operating temperature were determined by process simulation with a computer model, which is based on parameters, such as the minimisation of slag volume, liquidus temperature, electrical energy consumption and chromium losses. Chromium recoveries are identified for slag compositions spanning wide concentration ranges within the quaternary system MgO-AI2O3- SiO2-CaO. The simulated data are compared with the experimental results.

Jan 1, 1994

By F. Bourgeois, J. -S. Kroll-Rabotin

ABSTRACT: Falcon concentrators are enhanced gravity separators designed for concentrating fine particles. The Falcon UF model is unique in that it is dedicated to beneficiation of ultrafines, one key feature being that it does not make use of any fluidization water. We investigated the physics of particle transport inside Falcon concentrators, and concluded that separation efficiency is governed by differential settling velocity. We derived and published a predictive model of the partition function under dilute conditions. We intend to extend the initial model to concentrated ultrafine suspensions for application to industrial scenarios by adding hindered settling to account for solid concentration effects.

Jan 1, 2011

By Mathias Woydt

The tribological and mechanical properties of binderless and metal-bonded niobium carbides (8 or 12 vol.-% of Cobalt, 12 vol.-% of Fe3Al) are presented. Rotating disks made of niobium carbide bearing hard metals were mated against alumina (99.7%) under unlubricated (dry) unidirectional sliding tests (0,1 m/s to 12,0 m/s; 22°C and 400°C) as well as in oscillation tests (f= 20 Hz, ?x= 0,2 mm, 2/50/98% rel. humidity, n= 105/106 cycles). Microstructure and phase compositions were determined as well. The tribological data obtained were benchmarked with different ceramics, cermets, hard metals and thermally sprayed coatings, where NbC bonded with 8% and 12% Co presented above 8 m/s the lowest wear rates so far in such a benchmark. Binderless NbC (HP-NbC1) and the metal bonded NbCs exhibited low wear rates under dry sliding associated with high P?V load carrying capacities. NbC-based hard metal bonded with 12 vol.-% of Fe3Al resulted in a higher hardness level than for 12 vol.-% cobalt. The tribological profile established revealed a strong position of NbC bearing materials under tribological considerations and for closed tribosystems against established reference tribo-couples.

Jul 31, 2018

By S. J. Lui

Sodium oleate was an effective diaspore collector, whereas chelate collector OL2 showed certain collecting power over diaspore and nonionic surfactant OL3 showed little collecting ability. Then experiments were carried out using sodium oleate as the main collector with the addition of OL2,OL3 to study the influences on diaspore flotation, it could be seen from the experiments that accelerants had a marked influence on the recovery of diaspore, which could be raised by 10%, and the addition sequence also affected the flotation behavior: the best results could be gained when the accelerants were mixed thoroughly before adding and the best ratio of collector OL1 and accelerant OL2, OL3 stood at 30:2:1. Based on the calculation of the ingredients in the sodium oleate solution, sodium oleate reacted with surface of the mineral and formed the acid-soap polymer [HOl?Ol-] when pH was about 9. Zeta potential test showed the accelerant promoted the absorption of collector on the mineral surface, which lowered zeta potential. As could be seen from surface tension experi-ments, the addition of accelerant OL3 lowered the CMC value of OL1 solution, which was equiva-lent to raise the power of the agents. Further Infrared Ray experiments showed the co-absorption of OL1 and OL2 make aluminum oleate on the mineral surface more stable. Up till now, the mixed reagents with sodium oleate as the main collector, combined with other two accelerants had been used in the Zhongzhou concentration plant, which is the first diaspore flotation plant in China.

Jan 1, 2014

By F. Alsobrook

Industrial minerals are receiving increased attention by metals, coal and other companies seeking to diversify and stabilize earnings. Each industrial mineral has a unique set (and sub-sets) of business dynamics, however, and the diversity can present a bewildering maze to the corporate planner. Shrugging off this complexity and relying on serendipity for entry opportunities often results in unsuitable acquisitions. An effective alternative used in exploration can also be applied to strategic planning. By providing focus and direction, this flexible methodology can prevent wasting corporate resources on random pursuits and result in a quicker, more satisfactory achievement of diversification goals.

Jan 1, 1990

By Ed Labelle, Terry Overton, Gary Bell

"LocationThe Miller Minerals lime and limestone production facility is located in the Temiskaming district of Ontario at Hailey bury on the west shore of Lake Temiskaming. Located less than 300 km from Sudbury, Timmins, Rouyn-Noranda and Val d'Or, the plant is very well situated to market products to the mining, pulp and paper, and environmental industries. Being located a few kilometres from the Trans-Canada Highway and the Ontario Northland Railway adds to transportation efficiencies.ProductsAt Miller Minerals, two principal products in various sizes are produced, which are limestone (CaC03) and quicklime (CaO).HistoryProduction of limestone products began in 1979 at this quarry site. During the 1980s, limestone products were marketed to a variety of applications for mining, forestry, environmental and agriculture applications. In 1990, the production of quicklime products began, following the commissioning of an Italian-designed vertical shaft calcining plant. During the 1990s, both quicklime and limestone products were produced to meet the customers' demands.From the quarry's conception until 1992, the operation was owned and operated by Dymond Clay Products. In 1992, it was purchased by Miller Paving Ltd. of Markham, Ontario, and became a key part of the company's industrial minerals sector of business. Other Miller interests include dolomite, cement, paving materials and waste management."

Jan 1, 2000

By Susanne Pignolet-Brandom

Fourteen samples of crushed Duluth Complex rock were characterized by the QEM?SEM automated scanning electron microscope image analysis system to evaluate the application of the system to mining waste rock characterization. The system can reliably distinguish the iron sulfides, the copper-iron sulfides and the nickel-iron sulfides. Calcite was distinguished from all other minerals except fluorite. The volumetric abundances were verified by comparing elemental abundances calculated using the QEM"SEM volumetric percentages and appropriate mineral compositions with elemental abundances determined by standard laboratory procedure. The pH and sulfate concentrations of rinse water from laboratory leach experiments correlated well with the mineralogical data.

Jan 1, 1989

By Hans Lundberg

AFTER the war years, great activity has been shown in geophysical exploration for ore. The appreciation by mining and government geologists of geophysical techniques and results is largely responsible for the popularity of these methods. In Canada, plans are being made to study, by geophysical methods, the structure of a portion of the Pre-Cambrian shield in the hope that such studies will not only give a clearer picture of the geology, but will be of direct aid to the mining companies when selecting areas for detailed prospecting. Although geophysics thus has become more popular, some engineers are still reluctant to employ the methods to their full extent. Allotted funds are often rather low, so that the least expensive

Jan 1, 1947

By C. J. K. Purdy, H. E. Jamieson

"The comprehensive assessment of the environmental impacts of mining rare earth element (REE) deposits depends on a sound knowledge of the mobility of REEs in low-temperature aqueous environments. Temperature, pH and water chemistry are important factors controlling the aqueous mobility of REEs, while REEs are known to readily form complexes with both inorganic and organic ligands, and it has been shown that sorption and colloid formation may play an important part in dictating REE transport in the low temperature weathering environment. Ore and host rock mineralogy is also a key factor controlling the extent to which REEs are leached from mine waste. INTRODUCTIONThe aqueous mobility of rare earth elements (REEs) has commonly been explored in the past due to their potential application as tracers of geochemical processes in aqueous systems. REE mobility in low-temperature solutions has been shown to be dependent on the pH, temperature, ionic strength, and solution chemistry. For example, the aqueous transport of REEs can be modified by complexation with organic and inorganic ligands (Johannesson & Zhou, 1999; Klungness & Byrne, 2000; Luo & Byrne, 2004; Schijf & Byrne, 2004; Tang & Johannesson, 2010; Wood, 1990, 1993), or through sorption to suspended particles and colloids (Bau, 1999; Quinn, Byrne, & Schijf, 2004, 2006a, 2006b, 2007; Sholkovitz, 1995). Here we review the coordination chemistry, sorption behaviour and potential colloid association of REEs with respect to low temperature aquatic settings.RARE EARTH ELEMENT CHEMISTRYREEs include lanthanum to lutetium of Group IIIA in the periodic table. All share very similar chemical and physical properties. Often included in REE studies is another Group IIIA element, yttrium owing to its similar properties, and occasionally scandium, although its considerably smaller ionic radius makes for different properties and will not be discussed further here. The REEs are often subdivided into the light REEs (LREE), La to Sm, and the heavy REEs (HREE), Eu to Lu, which also usually include Y (hence are often referred to as YREE). The REE may be subdivided further into the LREEs, middle REEs (MREEs), and HREEs, in which case each classification includes La-Nd, Pm to Ho, and Er to Lu as well as Y, respectively, although definitions vary throughout the literature."

Jan 1, 2012

By Shilai Yuan, Huimin Lu, Liyuan Zhao, Zhijiang Gao

"A purification process was developed to removal impurity element boron from metallurgical grade silicon by electromagnetic induction slag melting. Vacuum melting furnace was used to purify boron in both Al2O3-MgO-CaO-SiO2 slag system and Al2O3-CaO-SiO2 slag system. The relationship between different slag chemistry and the removal of boron in silicon were studied using Back Propagation (BP) Neural Network model. The best slag chemistry for the removal of boron was predicted by Genetic Algorithm (GA) contributed by the use of Matlab. The results show that the mass fraction of Boron in silicon is reduced from 11.7496×10-6 to 2.3259×10-6 after slag melting in 28.96%Al2O3-3.43%MgO-36.24%CaO-31.37%SiO2 slag system. The relative error obtained with GA-BP Neural Network model was below 0.35%.IntroductionSolar energy, due to its low green house gas emissions, has been paid great attention. Accordingly, the demand for solar grade silicon (SoG-Si) has been growing rapidly. The quest for developing a low-cost method of producing SoG-Si has been moving forward in the last decade. Refining of metallurgical-grade silicon (MG-Si) attracts research interest due to its low material and energy costs, and more environmentally friendly technology in comparison to the traditional Simens process. As such, impurity elements in MG-Si must be removed to low levels for the photovoltaics (PV) cell to operate at optimum efficiency. Most impurities in metallurgical-grade silicon (MG-Si), especially metal elements, can be separated by directional solidification and the zone refining plasma-arc method [1, 2]. The main focus in refining MG-Si to SoG-Si is on the impurities which are the most difficult to remove. Boron has relatively high segregation coefficients (KB=0.8, concentration of Boron in solid silicon divided by its concentration in liquid silicon) [3] and higher vapor tension (the saturated vapor pressure of boron and silicon are 6.78×10-7 Pa and 0.4 Pa, respectively). The vacuum melting and directional solidification methods hence have no effects on boron removal.Slag refining involves melting MG-Si in the presence of a flux to produce a slag phase that can take up the impurity elements. The mechanism of slag refining is considered to include two main steps: the oxidation of boron and the absorption of boron oxide by slag materials. The oxidation of boron, described by the oxygen potential (PO2), resulting from the equilibrium Si and SiO2. The absorption of boron oxide, described as the slag basicity, is interpreted as expected to facilitate their extraction to alkali and alkali-earth oxides in the slag phase. Thus, effective removal may be obtained for a certain slag composition. Researchers [4-5] examined the effect of boron removal in CaO-SiO2 based ternary systems and showed that the addition of excess CaO can decrease the activity of SiO2. Researchers [6-8] studied the boron behaviors in CaO-SiO2-Al2O3, CaO-SiO2-Na2O, Al2O3-BaO-SiO2, CaO-SiO2-Li2O and Al2O3-CaO-MgO-SiO2 slag systems by adding boron in the silicon to a degree. Li2O, Na2O, MgO and BaO are thought to be associated with B2O3."

Jan 1, 2014

By Colin Hardie, Erik Bartsch, Guy Comeau

"The Xstrata Nickel Raglan Concentrator, located at the northern limit of Quebec’s Nunavik region has been in operation since 1997. Originally designed to process 800,000 tonnes per year of high grade nickel ore, plant capacity is currently approaching 1,200,000 tonnes per year due to an Optimization Project (FAG to SAG conversion) in 2005 and many recent processimprovements.In 2006, the Raglan Metallurgical Group with assistance from the Xstrata Process Support group decided to make SAG control one of its priorities in order to further increase throughput and improve stability. The original primary mill control logic delivered by the Optimisation Project in 2005 consisted of a simple PID loop controlling the mill charge (bearing pressure) through feed rate changes. Due to the multivariable, non-linear and disturbance dominated nature of the SAG circuit it was quickly found that this traditional PID control strategy was not able to adequately control the mill; resulting in poor stability, frequent operator interventions and less than optimum performance.This paper describes the successful integration of advanced field systems such as mill feed image analysis (Wipfrag) and crusher gap controller (ASRi), into a multi-variable fuzzy logic SAG mill controller. The process of how a strategy for control was developed and implemented directly in the existing control system (exploiting standard system capabilities) is discussed. It is also shown how this approach has provided mill automation which is simple, robust (despite erratic feed characteristics), and delivers both an increase in throughput and a reduction of variability.INTRODUCTIONOriginally commissioned as a Fully Autogenous Grinding (FAG) circuit in 1997, preparations to convert the Katinniq Concentrator Mill to SAG had in fact commenced as early as 1999, but were halted owing to alternative process improvements which achieved up to 1Mtpa as early as 2000. Up until this time, plant process controls had remained more or less static; modifications having been limited to those required by new equipment. Primary mill process controls and related measurements were at this stage limited to:"

Jan 1, 2008

By B. K. Larkin, H. R. Bailey

A model Of heat flow in an underground combustion process is studied. This model includes convection effects and thus is more general than previous studies which considered conduction as the only mechanistn for heat transfer. Both linear (tube run) and radial (field application) geometries are considered. The effects of ignition heaters, vertical losses and finite source width are considered for the linear case. The results are in the form of equations and are presented in graphical form for a number of cases. Convection effects increase frontal temperatures about 25 per cent over those computed for conductive transfer for typical field operating conditions. This increase in temperature is a result of heat being transported toward the front by the injection gas. Even greater temperature increases are realized as the per cent oxygen in the injection gas decreases. It is well known that compression costs are of considerable importance in estimating the economic feasibility of underground combustion. By assuming an ignition temperature for the combustion fuel, predictions of limiting conditions on fuel density and injection rate necessary to sustain the combustion zone are made. For typical field conditions, at least 0.75 lb/cu ft of fuel are needed with air as the injection gas. If the injection gas is 10 per cent oxygen and 90 per cent nitrogen, this figure is 0.69 lb/cu ft. INTRODUCTION The possibility of increasing oil recovery by underground combustion has been considered for many years. Recent field tests indicate that the underground combustion process is technically feasible. The economic feasibility depends to a large extent on the amount of air which must be injected to sustain combustion. Prediction of the success of employing underground combustion in a particular reservoir must be based on existing field tests, laboratory tube runs"' and solutions of mathematical or analog models. Vogel and Krueger5 devised an electrical analog of the heat transfer problem in an underground combus-ion process. They considered the problem of heat conduction from a cylindrical source with increasing radius assuming no vertical losses. Bailey and Larkin and Ramey solved the corresponding problem including vertical losses by considering a mathematical model of the conduction process. Ref. 9, 10 and 11 also present information related to the subject study. The present paper generalizes these results to include both conduction and convection mechanisms for heat flow. A model of the conduction-convection process is described. The partial differential equations governing this model are written and solved for a number of cases of interest. The formulas are evaluated and the results are presented graphically. A CONDUCTION-CONVECTION MODEL Description of the Model A number of models are employed in this paper, each of which approximate a particular physical situation depending on the geometry, i.e., linear or radial flow, the type of vertical heat losses, the nature of the source, etc. The geometry for both the linear and radial case is shown in Fig. 1. A particular linear model is described in this section, and variations from this model are described in later sections of the paper. Consider a homogeneous, semi-infinite porous prism with lateral sides insulated as shown in Fig. 1. The left end, x = 0, is heated for a time t, with a plane heater supplying a constant heat flux and during this time; gas (nitrogen) is passed through the pores of the prism at a constant mass flux. At time t, the heater is turned off and air is injected in place of the nitrogen. This causes combustion to take place, and a uniform source of width 1 is formed which moves at a constant velocity v, to the right. The frontal velocity v, is related to the gas velocity v,, through stoichiometric considerations

By F. A. Crossley

The titanium-rich end of the Ti-A1 system has been investigated up to 35 at. pct A1 (23 wt pet). One conzpound Ti3Al was found to occur between primary a and TiAl. It is ordered hcp with DO19 structure, it has virtually no solid-solubility range, and it has a closed maximum at about 875°C. OIL either side of the compound are a +Ti3Al two-phase fields. The limiting a1uminum solubility in primary a at the titanium-rich end is indicated to be 7.5 at. pct A1 (4.4 wt pet) at 550°C and about 6.8 at. pct Al fl wt pct) at 500°C. Quenching alloys from above the a + Ti3Al two-phase field produces the following structures with respect to alloy composition: Up to 13 at. pct A1 (7.8 wt pet), a solid solution; from 15 to 18 at. pct A1 (9 to 11 wt pct), shear transformation product or martensite; from 19 to approximately 30 at. pct (11 to 19 wt pet), submicro-scopic coherent Ti3Al in an a malvix. The twin hcp phase fields reported in the literature are the result of nonequilibrium corzdztions. Ti-A1 alloys, once partitioned by dwelling- in the a + ß phase field during either hot working or heat treatment, are extremely difjicult to homogenize at temperatures below 1000°C. Such partitioned alloys exhibit the characteristics or symptoms of two-phase materials, and may be said to suffer the "twin-phase syndrome". THE earliest investigations of the Ti-A1 system by Ogden et al.1 and Bumps et al.2 reported wide solubility of the primary solid solutions. Aluminum was reported soluble in the low-temperature allomorph to the extent of 37 at. pct (25 wt pct), and the first intermediate phase was reportedly TiA1. Somewhat later Kornilov et al.3 reported a similar diagram with phase boundaries displaced towards lower aluminum contents and higher temperatures. Beginning about this time (1956) reports in the literature made it very clear that one or more intermediate phases occurred at lower aluminum contents than TiAl.4-17 These reports included five major investigations of the titanium-rich end of the Ti-A1 diagram.4,12,14,16,17 Three of these diagrams show two two-phase fields below 37 at. pct Al, while two of them show a single two-phase field. The existence of the phase Ti3A1 is firmly established and is included in each of the diagrams, except one—that of Sato and Huang.12 The new phases are reportedly hcp and differ from primary a only slightly when disordered, and when ordered the "a" parameter is approximately one,4,12,15 two, 6-10,13,14 or four14 times that for primary a. Beyond this, however, the diagrams are remarkable for their lack of agreement. Two tacit assumptions are usually made in phase-diagram determinations of metal systems. These are: 1) equilibrium anneals bring the alloy to equilibrium or to indistinguishable closeness to it, and 2) equilibrium conditions established at elevated temperatures are either "frozen" by rapid quenching for evaluation at room temperature, or quench-transformation products are recognized as such. In the current investigation evidence was obtained that over substantial composition ranges neither of these two conditions was met in any of the more recent major investigations. I) MATERIALS, METHODS, AND TECHNIQUES The alloys of this investigation were prepared by nonc on sum able electrode arc melting. Materials used in the preparation of the alloys are summarized in Table I. The investigative tools employed were: optical and electron microscopy, differential thermal analysis (DTA), disatometry, X-ray diffraction, electron diffraction, and resistometry. Alloys for microscopic and X-ray investigations were prepared as 15-g melts. Alloys containing from 7 through 11 at. pct A1 were hot-rolled out of a furnace at 900°C, from 12 through 15 at. pct out of a furnace at 1000°C, and from 16 through 18 at. pct out of a furnace at 1125°C. Alloys containing more than 18 at. pct A1 could not be hot-rolled. The ingots were covered with Markal coating prior to hot rolling to minimize atmospheric contamination. After hot rolling, alloys containing up to 15 at. pct A1 were ground and pickled to remove 7 mils from each surface; alloys containing 16 and 18 at. pct A1 were skinned to a

Jan 1, 1967

Objective As mines become safer and disasters fewer, a time may come when no employees in the mining industry have any practical experience in managing a mine emergency. To fill an emerging gap in mine emergency response training, a multidisciplinary team of researchers and computer programmers from the NIOSH Pittsburgh Research Laboratory has developed an intervention for mining personnel who would be in leadership positions in the command center during emergencies. It is called MERITS, a computer-based emergency simulation exercise. MERITS is short for "Mine Emergency Response Interactive Training Simulation." It provides trainees an opportunity to gain command center experience during a simulated underground coal mine emergency. MERITS allows trainees to practice information gathering, situation assessment, decision-making, and coordination skills without risk to personnel or property. Individuals representing mine emergency response personnel, various State safety officials, and private mine management from three States have participated in MERITS training. What Is MERITS? MERITS is an extension of previous work that compiled a knowledge base relevant to mine disaster management via interviews, analysis of literature, reviews of past events, and observations of mock mine disasters. Findings from prior research found a need for an alternative method of command center training. This new computer simulation is being used to train emergency command center personnel to effectively manage an underground mine fire. Modeled after training simulations developed for other industries (e.g., to address nuclear accidents, chemical spills, evacuations, etc.), MERITS simulates underground and surface events related to the disaster. It exposes the user to events that typically occur during a mine emergency, such as lack of information and miscommunication. It also presents trainees with issues that must be addressed, such as making provisions for briefing news media and victims' families, ordering needed supplies, interfacing with Government enforcement agencies, and housing mine rescue teams. The outcome of the scenario is determined by the users' decisions and their emergency response plans. Field Results Field testing of MERITS was conducted with eight full-day training sessions at four different locations in Colorado, Pennsylvania, and West Virginia. These field tests benefited from the knowledge and experience of State of Pennsylvania inspection officials, representatives of the United Mine Workers of America(UMWA), and private mine management who served as trainees for the MERITS training sessions. Trainees self-reported an average of20 years of work experience in the mining industry. All trainees had participated in Mine Emergency Response Development (MERD) training exercises, and many had been involved in real mine emergencies. Trainee evaluation of the MERITS program is summarized below: •Twenty-six of the 27 trainees believed that the MERITS simulation helped them know how to prepare for a real emergency. •Twenty-five of the 27 trainees believed that the storyline for the MERITS simulation was either "very realistic" or "realistic." •All 27 trainees believed that the MERITS simulation helped them learn how to better handle a real emergency. •None of the 27 trainees stated that they were bored during the simulation. After the initial field tests, MERITS was refined and retested during training sessions for individuals from State agencies, the UMWA, and private industry. Mining personnel from underground coal and underground stone mines participated and responded positively to the learning experience. Technology Transfer Industry introduction to the MERITS program will occur throughout 2002. MERITS presentations at the Joseph A. Holmes Safety Association National Meeting in Virginia Beach, VA, in June.

Jun 1, 2002

By Rolando Gonzalez

Mexico’s role in the world economic community continues to grow. And it is important that the country makes use of its natural wealth, including its large underground deposits of minerals and metals. With that in mind, Industrias Peñoles S.A. de C.V.(Peñoles), a mining, smelting and refining company, began mining lead, zinc and other metals from the Francisco I. Madero Project (FIM). The mine is located about 600 km (370 miles) northwest of Mexico City in the state of Zacatecas. Peñoles plans to remove about 3 Mt/a (3.3 million stpy) of ore from FIM. To achieve this goal, the company needs to optimize its processing, to maximize the amount of metal it extracts through FIM’s large flotation lead-zinc concentrator. To ensure high productivity, Peñoles and its contract engineering firm, M3 Engineering and Technology, of Tucson, AZ, have implemented anore processing system.

Jan 1, 2003

By Leszek Maldzinski

The present concept assumes carrying out the process of controlled nitriding with NH3 alone. This is a simpler process than that using two-component mixes of ammonia diluted with N2 or NH3diss. The regulation of the chemical composition of the atmosphere in the retort, and therefore the regulation of the nitriding potential KN, is obtained through the variation of the inflow rate of NH3 into the retort. What is a completely new things in a relevant process, the inflow of NH3 into the furnace is at times reduced to zero, which widens the range of the gas composition in the retort (and by the same token, of KN). The amount of NH3 introduced into the furnace is regulated (controlled) with the aid of a gas analyzer (for example an infrared analyzer). The gas analyzer opens and closes periodically the NH3 inlet valve with a frequency maintaining a desired gas composition (a desired KN) in the retort. The concept was based on experimental and theoretical investigations in term of thermodynamic and kinetic of gas nitriding. Investigations were carried out in a laboratory furnace with a quartz tube and also in an industrial furnace with a steel retort and a circulating fan. Nitriding was performed using NH3, NH3+H2, NH3+NH3diss. mixtures. In an industrial furnace the supply of NH3 into the retort was periodically closed, though with an operating circulation fan. The studies demonstrated that the growth rate of nitrided layer depends only on the composition of the atmosphere, (or KN), in the retort. It depends neither on a type of atmosphere introduced into furnace (NH3, NH3+NH3diss. or NH3+H2) nor a type of furnace (laboratory with a quartz tube or industrial with steel retort and fan). The results proved also that entirely closing of NH3 supply to the retort does not affect the growth rate of nitrided layer. A detailed analyses of the results was performed in a paper.

Aug 16, 2017

By Silvio de Carvalho Sabença

Um forno a arco elétrico é um tipo de forno industrial que usa uma corrente elétrica alternada para produzir calor. Estes equipamentos servem como uma alternativa para os altos fornos tradicionais, e desempenham um papel importante na produção de aço. Em um forno de arco elétrico, a corrente elétrica passa através dos eletrodos de grafite, do aço e de outros metais, o que resulta na produção de aço de modo mais rápido e eficiente. A queda de tensão no arco é, praticamente, proporcional à distância entre o eletrodo e a carga. O eletrodo corresponde ao polo positivo (+) e a carga o negativo (-). Em corrente alternada os pólos, positivo e negativo, trocam de posição a cada meio ciclo da tensão de rede. Sob condições de arco, forma-se, no eletrodo e na carga, uma finíssima camada altamente ionizada devida a uma altíssima concentração do campo elétrico nestas zonas. No forno o arco se extingue quando a corrente se anula e reacende, quando a tensão volta a crescer. Devido a constantes quebra de eletrodo foi montado o grupo de trabalho com objetivo de reduzir o consumo dos eletrodos, otimização do consumo de energia, redução do Power On, aumento da potência média e redução nas quebras de eletrodos. Esta implantação foi extremamente importante pois o mesmo está garantindo a continuidade operacional, de forma segura e confiável, de um dos equipamentos mais importantes para a produção de aço na Usina.

Aug 17, 2017