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By J. Etcheverry, E. Seguel, R. Díaz, F. Parada, R. Parra, E. Balladares

A thermodynamic and kinetic model is proposed to explain the formation of bornite, chalcopyrite and magnetite during partial roasting of enargite-containing copper concentrates. The proposed mechanism involves solid-solid-gas and solid-gas reactions between chalcocite, pyrrhotite, gaseous sulfur and oxygen. The formation of bornite could be explained by a two-step reaction: the first one involving the formation of chalcopyrite by a reaction between Cu2S, FeS and gaseous sulfur, followed by a second step in which the newly formed chalcopyrite reacts with additional chalcocite to form bornite. Although thermodynamically the direct formation of bornite is more favorable than that of chalcopyrite, the lower diffusion kinetics of bornite formation could explain the preferential formation of chalcopyrite. If the reaction occurs with stoichiometric chalcocite and pyrrhotite in the presence of gaseous sulfur to form chalcopyrite, no bornite is formed, while for the stoichiometric reaction between chalcopyrite and chalcocite in the absence of sulfur, only bornite is formed. For the formation of magnetite and chalcopyrite the mechanism could involve the partial reaction of chalcocite and pyrrhotite in the presence of oxygen. The proposed model is thermodynamically consistent with the experimental results obtained in laboratory and pilot plant. INTRODUCTION The processing of high-arsenic copper concentrates with over 0.7 wt.-% arsenic by conventional smelting-converting normally require an additional arsenic removal step to reduce arsenic content to levels below 0.2–0.3%. One of these high-arsenic copper concentrates is the one produced by the Ministro Hales Division (DMH) of CODELCO, which has the typical chemical composition shown in Table 1. Enargite (Cu3AsS4), chalcocite (Cu2S) and pyrite (FeS2) are the main mineralogical species present in these concentrates, with over 75 wt.-%, as shown in Table 2. Partial or “neutral” roasting of these concentrates under controlled temperature and partial oxygen pressure conditions at 923–993K (650–720ºC) can remove up to 95% of the arsenic as As2S3 (As4S6), which has a high vapor pressure under these conditions, leaving a calcine with low residual arsenic. In copper concentrates, arsenic is present generally as enargite and arsenopyrite. This compounds as well as others such as pyrite and covelite, decompose readily above 770 K (500ºC), releasing, in addition to gaseous arsenic trisulfide, gaseous sulfur which by oxidizing to SO2 generates most of the heat required by the process.

Jan 1, 2019

By Thomas Hauquin, Olivier Deck, Yann Gunzburger

"In this study, 2D numerical modeling of a room-and-pillar mine is conducted along with the calculation of all terms of the mechanical energy balance. Simulations of different geometrical and geomechanical configurations are performed in order to investigate the conditions that favor a high seismic energy release (instability) during the excavation (removal) of one single pillar. At first, classical stressstrain simulations enable us to estimate the elastic and quasi-static response of the mine. Then, owing to the implementation of new functions in the modeling code, the seismic energy released when the pillar is removed is calculated. The obtained values are found to be in agreement with those calculated analytically using a modified energy balance based on the works by Cook (1967) and Salamon (1984).It is shown that the mine’s proneness to release large amounts of seismic energy, after sudden removal of one single pillar, mainly depends on three parameters: the initial extraction ratio of the mine, the depth of the exploited seam and the Young’s modulus of the surrounding rock mass compared to that of the ore. Moreover, it is pointed out that the magnitude of the seismic energy can be greater than that of the stored elastic energy, meaning that the dynamic (seismic) transient stresses should not be neglected when compared to the quasi-static stresses, particularly when trying to prevent the risk of rockburst and collapse in underground mines."

Jan 1, 2015

By Oliver Bowles

When a new type of equipment revolutionizes methods of quarrying one kind of stone, producers of other kinds focus their attention on its potentialities in their particular fields. The purpose of this paper is to discuss the accomplishments of the wire saw in slate, to show its more limited attainments in other kinds of stone, and to point out the possibilities of much wider application. A wire saw consists of a 3/16-in. or ji-in. three-strand wire cable that runs as a belt and cuts the rock by abrasion. (Fig. 1. The teeth of the saw are sand grains carried in the grooves between the strands. Accomplishments in Slate† Initial experiments with wire saws by the U. S. Bureau of Mines in the Colonial Slate Quarry, Wind Gap, Pa., in 1926, attained success so immediate and pronounced that within two years in virtually every quarry in the neighborhood of Wind Gap, Pen Argyl and Bangor, the most productive slate area in the United States, wire saws were substituted for channeling machines. An 80-ft. cut in slate is shown in Fig. 2. The technique of operation has been described in several reports (references at the end of the paper). The present purpose is to summarize the accomplishments in a large, typical slate quarry after nine. years of experience. Parsons Bros. Slate Co., at Pen Argyl, Pa., substituted two wire saws for six channeling machines in 1927. The following comparisons are made between the present method with wire saws and the former channel-ing-machine method. Rate of Sawing.—The average rate of cutting with a wire saw in the early days of its operation, as determined by the Bureau of Mines', wits 14 to 17 sq. ft. per hour. Parsons Bros. Slate Co. estimates the present rate of cutting at about 25 sq. ft. an hour, whereas the channeling-rnarhirle

Jan 1, 1938

By Oliver Bowles

When a new type of equipment revolutionizes methods of quarrying one kind of stone, producers of other kinds focus their attention on its potentialities in their particular fields. The purpose of this paper is to discuss the accomplishments of the wire saw in slate, to show its more limited attainments in other kinds of stone, and to point out the possibilities of much wider application. A wire saw consists of a 3/16-in. or ji-in. three-strand wire cable that runs as a belt and cuts the rock by abrasion. (Fig. 1. The teeth of the saw are sand grains carried in the grooves between the strands. Accomplishments in Slate† Initial experiments with wire saws by the U. S. Bureau of Mines in the Colonial Slate Quarry, Wind Gap, Pa., in 1926, attained success so immediate and pronounced that within two years in virtually every quarry in the neighborhood of Wind Gap, Pen Argyl and Bangor, the most productive slate area in the United States, wire saws were substituted for channeling machines. An 80-ft. cut in slate is shown in Fig. 2. The technique of operation has been described in several reports (references at the end of the paper). The present purpose is to summarize the accomplishments in a large, typical slate quarry after nine. years of experience. Parsons Bros. Slate Co., at Pen Argyl, Pa., substituted two wire saws for six channeling machines in 1927. The following comparisons are made between the present method with wire saws and the former channel-ing-machine method. Rate of Sawing.—The average rate of cutting with a wire saw in the early days of its operation, as determined by the Bureau of Mines', wits 14 to 17 sq. ft. per hour. Parsons Bros. Slate Co. estimates the present rate of cutting at about 25 sq. ft. an hour, whereas the channeling-rnarhirle

Jan 1, 1938

By Jin-Chun Kim

Nanosized W based powders (W, WC, WC-Co) were produced by chemical vapor condensation (CVC) process. Two different solid W(CO)6 and Co2(CO)8 metal-organic materials were used as precursors. CVC experiment was conducted in the temperature range of 400-1100. As-CVC WC1-x powder which had non-stoichiometric composition was carburized by using of the CH4-H2 mixed gas in temperature range of 750-850. The CVC W and WC1-x powders showed loosely agglomeration structure, and the Co powder had intricate long stand structure because of intrinsic magnetic properties of Co phase. Carbon content of the CVC powders controlled by gas-phase carburization was well matched with theoretical WC stoichiometry (6.13wt%).

Jan 1, 2006

By Weiying Zeng, Shouwei Wang, Jinbei Zhong, Xiangdong Meng, Lingtian Meng

"Due to a drainage problem, the Lanzhou to Chongqing high-speed rail line had been out of service during the 2015 wet season, so a drainage tunnel is to be constructed for the line and required to be accomplished before the 2016 wet season. This drainage tunnel is only 5 meters below the line which is in service, therefore blasting vibration needs to be strictly controlled. This paper introduces all theapplied blasting methods, parameters and detonation throughout the entire project, finally bringing in the electronic detonator stagger phase technique and corresponding time difference for detonation."

Jan 1, 2017

By D. W. Fuerstenau

This paper presents the results of an investigation of the stability of the mass flow rates and average pellet size in the different streams of an industrial-scale balling circuit. The variables in this study include water content, drum speed, and fresh feed rate. It was found that both the mass flow rates and pellet diameter are greatly disturbed when a change, positive or negative, in any of the variables takes place. For most of these disturbances to be damped down, a period of 1 hr or so is required. When a disturbance in the feed rate was made, the transient period extended to more than 1% hr (the duration of the experiment). It was observed that there is an interaction between the drum speed and moisture needed for producing an acceptable green ball product. The moisture content of the product pellets was found to be a function of the pellet size, with the larger pellets retaining a higher moisture content

Jan 1, 1983

By R. V. Ramani, V. T. Burgos, J. A. McClay

Introduction The Cost program was developed to provide the planning engineer with a tool to evaluate the cost implications of the technical mine design decisions. Direct costing methods are employed, where feasible, to provide greater detail and accuracy in the primary cost centers. Options have been provided in the cost computation, economic analysis, and output data subsystems to increase the flexibility of the system. Computer Program The program is written in Fortran IV for use in the IBM System 360/370 computers. i. Main - The main routine reads and stores input data from three sources, user input, Cost Data Library, and data transfer from the Master Design Simulator. Data is trans¬ferred to the appropriate subroutines, as they are called, by means of labeled common blocks. ii. Subroutine CSTCOM - is a data modification routine which computes the peripheral charges related to labor and supervisory costs. iii. Subroutine MANPWR - interrogates section data to determine the total labor and supervisory costs for each cost center. iv. Subroutine CAPCST - computes the total capital investment for each cost center, including the economic life and salvage value of each element. Capital costs are determined by user selection of quantities and models of equipment. Equipment costs are stored in the Cost Data Library for retriev-

Jan 1, 1975

By J. P. Ibáñez

The uptake of copper from extremely dilute aqueous solutions by alginate in the form of protonated dry alginate beads was investigated. Barium was used to cross link the alginate forming the beads. The effect of various experimental parameters such as pH and metal ions concentration on the uptake of copper were studied. The uptake was strongly dependent on the Cu-bearing solution pH up to a value of 4.5. A removal of 100% o was achieved when the initial concentration of copper was as low as 8.0 mg/L. The maximum uptake, i, e., the loading capacity, was found to be 167 mg of copper per g of beads. The mechanism governing the removal of copper was found to be ion exchange between protons of the alginate beads and cupric ions of the solution. For this ion exchange process a molar ratio, d[H+]/d[Cu2+], of 2.0 was determined. EPMA-EDX analysis of the Cu-loaded beads showed a uniform distribution of the ions throughout the structure of the alginate, regardless the solution pH. This may suggest that this sorbent material is a porous ion exchanger having high permeability and capacity. The uptake of copper and of the heavy metals cadmium and zinc by this sorbent is compared.

Jan 1, 1999

By Ismael Gottreux Vollet, Carlos A. Muñoz Lira, Alejandro Ferrada Vergara

Currently, underground mining of deeper massive deposits with lower grades, harder rock conditions in high strength environments, entails difficulties in caving, fragmentation and seismicity of the ore body. So far, the use of Pre-Conditioning (PC) with Hydraulic Fracturing (HF) has shown positive results in terms of seismic response and caving ability, while preconditioning combined with explosives aims to weaken the rock mass, causing an additional effect on fragmentation.

Jan 1, 2016

By David A. Lipton

U.S. Bureau of Mines personnel examined mines, prospects, and mineralized areas to determine the mineral resources and potential of the Moses and Dennison Peak RARE II areas in Tulare County, California. These areas, along the west slope of the Sierra Nevada, are underlain by grarnitic rocks of the Sierra Nevada batholith and contain numerous metasedimentary roof pendants. Silver, copper, and zinc occur in contact-metasomatic deposits within the metasedimentary rocks. In the Moses area, the Powell Mine (fig. 1) contains an estimated 90,000 tons (82,000 t) of subeconomic silver, zinc, and copper resources. The King Solomon Prospect has 3,000 tons (2,700 t) of silicified phyllite containing zinc. On the Helen-Joyce Prospect, 44,000 tons (40,000 t) of gossan occur above a poorly exposed silver-zinc rich zone. Potential exists for additional mineral resources and occurrences at each of these properties.

Jan 1, 1983

By F. G. Miller, R. C. McFarlane, T. D. Mueller

During the process of gas storage in pressure-depleted oil reservoirs, it has been observed that in some instances additional liquid oil is recovered and that the composition of the storage gas is materially altered. A mathematical study was made of the dynamic behavior of such a depleted oil reservoir undergoing gas injection. The important variable considered in this study, not included in previously published work, was that of compositional effects on the phase behavior of two-phase flow. Pressure, saturation and component composition profiles were developed for a linear, horizontal and homogeneous porous medium containing oil and gas but undergoing dry gas injection. Special new techniques were developed to overcome the problems of numerical smoothing which arise in the solution of the equations representing such systems. The method of solution includes the development of partial differential equations describing the behavior of the system, representing these equations by finite difference approximations, making certain simplifying assumptions and, finally, applying methods of numerical analysis with the aid of a high-speed digital computer. In an example calculation, results using the mathematical model are compared with field observations made on a gas storage project in Clay County, Tex. This field project involved a depleted oil reservoir used 'for gas storage and gas cycling purposes. As a result of these processes, the reservoir yielded substantial amounts of secondary oil, both in the form of stock tank oil and as vaporized products in the produced gas. The methods derived in this study may be applied to a variety of oil reservoir problems which are dependent on compositional effects. In recent years the number of oil reservoirs being used for gas storage purposes has increased greatly, and there has been at least one published account of additional oil recovery resulting from gas cycling a depleted oil reservoir after repressur-ing with dry gas for storage purposes. Additional oil recovery from oil reservoirs resulting from gas storage operations could become an important secondary recovery process. This is especially true since the use of natural gas in large metropolitan areas continues to increase and more gas storage volume near these areas is needed. These facts provided the motivation for the work reported here. This paper reports on a study of the inter-relations of composition, saturation and pressure changes which occur when hydrocarbon gas is injected into an oil reservoir system. From an understanding of the process, prediction methods may be developed for use in forecasting the secondary recovery products from gas storage operations in oil reservoirs and, consequently, .the economics of such projects can be developed. The process of storing hydrocarbon gas in an oil reservoir and the cycling process both involve the transient multi-phase flow of oil reservoir fluids with changing fluid compositions. There is a scarcity of work published on the subject. One of the first laboratory models developed to study a problem similar to the one posed here was published in 1948 by Standing, Lindblad and Parsons. l They developed a model to study gas condensate recovery by gas cycling, including the effect of heterogeneous reservoir permeability. Their results showed the compositional effects of injecting a gas of known composition into a two-phase condensate reservoir of known composition. A major finding of their study indicated that maximum oil recoveries from gas cycling projects result when low cycling pressures are used. Previous to their work it was generally considered

By P. Shahinian, J. Weertman

Minimum creep rates of nickel samples were measured in the stress region of 2.5x107 to 2.8xl0 dyne per sq cm and the temperature region of 400° to 1100°C. The creep rate seems to be proportional to (stress) at stresses below 7x10H dyne per sq cm. The activation energy of creep is approximately 65,000 cal per mol. IN a recent theory' of steady-state creep which is based on Mott's dislocation climb mechanism, the following creep equation was derived for creep in polycrystalline metals (if where K is creep rate, Q the activation energy of self-diffusion, S the entropy of activation of self-diffusion, L' the grain size, L the subgrain size, b the length of the Burgers' vector of a dislocation, u the shear modulus, u the stress, a the critical shear stress, M the density of active Frank-Read sources, v the vibrational frequency of a vacancy, and kT has its usual meaning. This equation predicts a creep rate which depends on the stress through a power law at low stresses. At high stresses the creep rate increases much more rapidly with stress. The theory breaks down for stresses great enough that the inequality holds true. It was the purpose of the present in-

Jan 1, 1957

By David K. Hylbert

This study investigated roof falls in room-and-pillar drift coal mines in eastern Kentucky and utilized geologic methods for predicting roof conditions in advance of mining. In the Highsplint mine, the roof was classified in four categories or conditions: Condition A and B (Laminated Shale); Condition C (Rolling Sandstone with Shale in Pockets); and Condition D (Zone of Major Sandstone Roll(s)). Structure contour and isopach maps of the Darby coal bed and associated immediate roof rocks were wed to project axial trends of the sandstone roof. Trend mapping in the mine and on outcrop provided more detailed control for roof projections.

Jan 12, 1978

By D. DeGagné, E. De Souza, J. F. Archibald

A comprehensive survey of minefill practices in underground mines in Canada has been conducted. The survey was designed to cover the entire filling operation for individual mines from feed to the preparation plant, to underground transportation, and to stope placement. The questionnaire examined such areas as mining method utilized, the purpose of backfilling, backfill formulations, including binding and chemical additives, slurry properties, transportation parameters, stope preparation procedures, backfill placement properties, fill instrumentation, and costs. This paper presents the current state of backfill usage in Canada, identifies trends in minefill practices and provides mine operators with an updated database to compare their own practices with modern trends throughout the industry.

Jan 1, 2001

By M. Boussuge

Ceramics and refractories have many common constituents and consecutively exhibit several analogous properties. For example, concerning the thermomechanical properties this paper will focus on, the type of creep that can be observed in both materials is often the same (kinematic hardening). Changes in microstructure (phase transformation, dehydration, sintering, crystallisation,...), induced by heating and/or cooling, can also drastically modify the mechanical behaviour of ceramics and refractories. But the coarse granulates, the porosity and the impurities contained in industrial refractories may lead to specific responses of this material to thermal and/or mechanical loadings. In particular, some differences can be observed with technical ceramics in the main type of damage observed in service : diffuse damage in refractories (microcracking) and localised damage in ceramics (macrocracking). In this paper, the possibilities of transferring a part of knowledge from ceramics to refractories will be discussed, in the field of thermomechanical properties : experimental characterization techniques, mechanical behaviour models. Finally, some problems caused by scale effects and by the integration of thermomechanical properties of refractories in the numerical simulation of industrial structures will be evoked.

Jan 1, 2004

By J. G. Smith, L. P. Sheets

Introduction Potential applications that exploit the electrical properties of coal measure rocks include: (1) radar sensing of coal face, floor, and roof for automated mining operations; (2) underground wireless communications; and (3) sensing extent of subsidence, blasting operations, coal gasification bums, and moisture migrations. Impediments to exploitation of electrical properties include: (1) a lack of reliable electrical properties data for in situ conditions and (2) a lack of correlation data between electrical properties and other relevant physical properties. In this paper data are presented for electrical conductivity and permittivity for Appalachian and Illinois shales for a frequency range 2 x 10 to 2 x 10 Hz. These data are useful in establishing in situ electrical property variability, lower limits, and anisotropy. Electrical proper¬ties measurement and values for other coal measure rocks are discussed as well. Laboratory measurement For the frequency range investigated, a capacitance bridge and Q-meter were employed. These instruments are designed to yield bulk values of permittivity and conductivity. Disk samples of thickness 0.396 cm (0.156 in.) and diameter 2.54 cm (1 in.) were machined from cores obtained from the two coal basins. While both the capacitance bridge and the Q-meter must be balanced manually, the bridge has an analog-to-digital interface and an attached computer specifically designed to expedite data collection and interpretation. Sample holders are critical components in the measurement process. A Hartshom-Ward holder was employed with the bridge and a Marconi micrometer jig was used with the Q-meter. Neither commercial sample holder was designed to regulate ambient humidity conditions. Because water adsorbed on sample faces may cause errors approaching 100%, special enclosures were designed for both holders. Each enclosure contains a flush-mounted externally-manipulable carousel, an externally-manipulable rigid arm that can accomodate translational motion and three-dimensional rotation, a compartment for humidity regulating solids or liquids, and a humidity sensor. Each enclosure will accomodate several samples that can be manipulated within the enclosure without opening it. Experience gained during this research demonstrated that humidity regulation was necessary to obtain repeatable results. Grinding and polishing shale to a very thin thickness (about 0.4 mm) was shown to cause changes in electrical properties as well. These latter changes were attributed to alterations in the water content. Theoretical considerations A very comprehensive discussion of the electrical properties of sedimentary rocks is available in literature (Sen and Chew, 1983). These authors reviewed the work of others and proposed modifications to better explain the frequency dependent behavior of the permittivity and conductivity of rocks. A large portion of their article was devoted to explanations of large relative permittivities at low frequencies such as observed in this research. They noted that the electrical properties of formations containing shales and clays are the most difficult to explain. Sen and Chew noted the need for additional experimental data and further refinements in theory. Results Shales, limestones, and sandstones were examined for a single 150-m (492-ft) core from Pennsylvania and for a dark shale from a southern Illinois coal mine. Figures 1 and 2 illustrate the conductivities and relative permitivities for the southern Illinois dark shale at a single location. The differences in electrical properties clearly

Jan 1, 1987

By John Chipman, Eric R. Jette, O. B. Ellis

IN the study of the chemical reactions occurring in the open-hearth furnace, it is frequently assumed that a condition of equilibrium between slag and metal is attained. In order to test this assumption it is necessary to have dependable operating data as well as an exact knowledge of the equilibrium state. Considerable progress has already been made in the study of slag-metal equilibria, notably in the earlier work of Herty1 and of Oberhoffer and Schenck2 and in the more recent researches of Krings and Schackmann3 and of Koerber and Oelsen.4 None of these investigators, however, have employed basic slags comparable to those encountered in basic open-hearth practice, so that up to the present time our only information regarding the equilibria of these slags is based upon observations drawn from steelmaking practice in which there is little assurance that actual equilibrium was attained. The original plan of this investigation was to secure simultaneous slag and metal samples at intervals during the making of an open-hearth heat, recording the heat history in detail and obtaining complete analyses of slag and metal, then to bring these slag samples into equilibrium with liquid iron in the laboratory induction furnace and thus to determine directly whether or not the observed relationships in the open hearth represent conditions approaching equilibrium. This plan was only partly successful. While slags were obtained from the open hearth under satisfactorily recorded conditions and these were remelted in the laboratory under equilibrium conditions, changes in slag composition, which accompanied the remelting operation, were so great that the final slag from the induction furnace bore little resemblance to its open-hearth parent and the direct comparison was therefore abandoned. The results, however, lie within a range of slag composition that is of interest in the making of low-carbon steel. As far as we are aware, they represent the first published laboratory study of equilibria involving slags that contain all the constituents of basic open-hearth slag. EXPERIMENTAL HEATS The first set of measurements on slagmetal equilibrium was made in the Research Laboratories of the American Rolling Mill Co. at Middletown, Ohio. This will be known as series A. The second set was made in the Metallurgical Research Laboratories at Massachusetts Institute of Technology, and will be referred to as series B. Series A.-The induction furnace used has been described.5 Approximately I kg. of a special ingot iron containing less than

Jan 1, 1941

By O. B. Ellis, Eric R. Jette, John Chipman

In the study of the chemical reactions orcurring in the open-hearth furnace, it is frequently assumed that a condition of equilibrium between slag and metal is attained. In order to test this assumption it is necessary to have dependable operating data as well as an exact knowledge of the equilibrium state. Considerable progress has already been made in the study of slag-metal equilibria, notably in the earlier work of Hertyl and of Oberhoffer and Schenck2 and in the more recent researches of Krings and Schack-mann3 and of Koerber and Oelsen.4 None of these investigators, however, have employed basic slags comparable to those encountered in basic open-hearth practice, so that up to the present time our only information regarding the equilibria of these slags is based upon observations drawn from steelmaking practice in which there is little assurance that actual equilibrium was attained. The original plan of this investigation was to secure simultaneous slag and metal samples at intervals during the making of an open-hearth heat, recording the heat history in detail and obtaining complete allalyses of slag and metal, then to bring these slag samples into equilibrium with liquid iron in the laboratory induction furnace and thus to determine directly whether or not the observed relationships in the open hearth represent conditions approaching equilibrium. This plan was only partly successful. While slags were obtained from the open hearth under satisfactorily recorded conditions and these were re-melted in the laboratory under equilibrium conditions, changes in slag composition, which accompanied the remelting operation, were so great that the final slag from the induction furnace bore little resemblance to its open-hearth parent and the direct comparison was therefore abnndoned. The results, however, lie within a range of slag composition that is of interest in the making of low-carbon steel. As far as we are aware, they represent the first published laboratory study of equilibria involving slags that contain all the con stituents of basic open-hearth slag. Experimental Heats The first set of measurements on slag-metal equilibrium was made in the Research Laboratories of the American Rolling Mill Co, at Middletown, Ohio. This will be known as series A. The second set was made in the Metallurgical Rescarch Laboratories at Massachusetts Institute of Techology, and will be referred to as series B. Series A.—The induction furnace used has been described. Approximately I kg. of a special ingot iron containing less than

Jan 1, 1941

By John Chipman, Eric R. Jette, O. B. Ellis

In the study of the chemical reactions orcurring in the open-hearth furnace, it is frequently assumed that a condition of equilibrium between slag and metal is attained. In order to test this assumption it is necessary to have dependable operating data as well as an exact knowledge of the equilibrium state. Considerable progress has already been made in the study of slag-metal equilibria, notably in the earlier work of Hertyl and of Oberhoffer and Schenck2 and in the more recent researches of Krings and Schack-mann3 and of Koerber and Oelsen.4 None of these investigators, however, have employed basic slags comparable to those encountered in basic open-hearth practice, so that up to the present time our only information regarding the equilibria of these slags is based upon observations drawn from steelmaking practice in which there is little assurance that actual equilibrium was attained. The original plan of this investigation was to secure simultaneous slag and metal samples at intervals during the making of an open-hearth heat, recording the heat history in detail and obtaining complete allalyses of slag and metal, then to bring these slag samples into equilibrium with liquid iron in the laboratory induction furnace and thus to determine directly whether or not the observed relationships in the open hearth represent conditions approaching equilibrium. This plan was only partly successful. While slags were obtained from the open hearth under satisfactorily recorded conditions and these were re-melted in the laboratory under equilibrium conditions, changes in slag composition, which accompanied the remelting operation, were so great that the final slag from the induction furnace bore little resemblance to its open-hearth parent and the direct comparison was therefore abnndoned. The results, however, lie within a range of slag composition that is of interest in the making of low-carbon steel. As far as we are aware, they represent the first published laboratory study of equilibria involving slags that contain all the con stituents of basic open-hearth slag. Experimental Heats The first set of measurements on slag-metal equilibrium was made in the Research Laboratories of the American Rolling Mill Co, at Middletown, Ohio. This will be known as series A. The second set was made in the Metallurgical Rescarch Laboratories at Massachusetts Institute of Techology, and will be referred to as series B. Series A.—The induction furnace used has been described. Approximately I kg. of a special ingot iron containing less than

Jan 1, 1941