Search Documents

By Frank T. Sisco

DURING the past year the iron and steel industry of the world as a whole operated on a satisfactory basis. No discoveries nor new processes of outstanding importance were announced either here or abroad, although rumors of such were persistent. In general, the efforts of operating and research men in the iron and steel industry seemed to be confined to improving quality and reducing cost, not a new aim, for the same efforts have been noted in nearly all of the annual reviews of the industry for at least fifty years. Most published papers on blast furnace or steel-making practice were of minor importance, at least when judged by the criterion of radical change in process or product. If the number of reports in the technical journals, or articles in the trade press, is used as a basis for comparison, continuous-mill sheet is still the most important single product of the industry; papers were published detailing the results of the investigation of various phases of the

Jan 1, 1938

By John A. Putnam, Morrough P. O’Brien

DATA on the physical and thermodynamic properties of hydrocarbons have been made available in recent years but the formal method of applying these data to flow in porous media appears not to have been fully developed. By making usual thermodynamic assumptions and employing existing data on permeability to two-phase flow, Darcy's law may be applied to obtain the flow characteristics for representative combinations of flowing medium and geometry. The numerical examples presented herein are based on hydrocarbons for which complete physical and thermodynamic data are available under equilibrium conditions. INTRODUCTION Thermodynamic data are obtained in the laboratory under equilibrium conditions and their application requires the assumption that equilibrium also exists during flow. This assumption is at least usual in engineering analyses, though not easily justified in many instances, and will be followed here. In regard to hydrocarbons, laboratory experience in determining the pressure-volume-temperature relationships indicates that gas-liquid mixtures must often be stirred vigorously for periods of 15 to 20 min. before reaching equilibrium. On the other hand, boiling and condensation are known to occur on solid surfaces and the large surface exposed to the flowing substance by a porous medium may bring about rapid approach to equilibrium. For the purpose of providing at least a guide to experimentation and a standard for later comparison with experimental results, it will be assumed that the phases present in cross sections perpendicular to the direction of flow are in thermodynamic equilibrium. Another assumption usually made in the solution of problems of flow in porous media is that the fluid remains at a constant temperature; i.e., isothermal flow. This assumption is arrived at by considering the porous medium and surroundings to be an infinite heat source and the rate of heat flow to be infinite at a boiling front. Its validity depends in large measure upon the character of flow, the number of components, and the physical and thermodynamic properties of the fluid. However, the assumption of isothermal flow represents a limiting case. The other limit can be represented by the assumption that the fluid is thermally isolated; i.e., irreversible adiabatic. The thermodynamic process characterizing the actual flow of a given fluid system probably lies somewhere between these two limiting cases and might be thought of as a flow system in which the confining walls are maintained at a constant temperature. For isothermal flow the solid material of the porous media is considered as the infinite heat source capable, without loss in temperature, of giving up heat to the fluid as the latter tends to cool by expansion. For the thermally isolated system, the solid material is considered to give up no heat to the fluid. In the intermediate case the impervious walls confining the porous media are at constant temperature from which heat is transferred along various paths, solid and fluid, throughout the porous media. It would appear that an actual petroleum-

Jan 1, 1941

By M. L. Holzworth, Joseph C. Kremer, Paul A. Beck, L. J. Demer

FOR alloys which are in practice heat treated to obtain increased strength, such as steels, duralumin, copper-beryllium, and others, the treatment usually involves heating to a relatively high temperature. At such temperatures the grain size of the product is largely determined by grain growth. Even in metals and alloys annealed merely to relieve work hardening, recrystallization is generally followed by a certain amount of grain growth. Thus, effective grain size control, which is often of great practical importance in manufacturing processes, depends on the grain growth behavior of the material used. Despite its importance, grain growth has been the subject of few investigations of a fundamental nature. The term "grain growth" has been used to designate a group of related, but distinctly different, phenomena. The two most important and best known of this group are illustrated by the following example. Curve a in Fig r shows the increase of the average grain size of a copper-beryllium alloy, containing 2 pct Be and 0.15 pct Co, with increasing annealing temperature. The time of annealing was 2 hrs. The grain size was quite uniform in all specimens. The results of a similar experiment with an alloy containing 2 pct Be and 0.31 pct Co are shown by curve b. It is seen that for any annealing temperature below T. the grain size was smaller than in the previous case. Grain growth became slower with the higher Co content. This "inhibiting" effect of the higher Co addition was associated with the appearance in the microstructure of fine, light blue particles of the CoBe phase. Up to temperature T. the structure of the inhibited alloy (curve b) was just as uniform as the structures represented by curve a. However, after annealing at T, or at higher temperatures, the inhibited alloy showed some extremely large grains (much larger than the grain sizes developed by the uninhibited alloy with low Co content) mixed with the small grains according to curve b. The presence of these mixed or "duplex" structures is indicated in Fig 11 by the vertical lines branching off curve b. The type of grain growth occurring in uninhibited Cu-Be alloys (curve a) has has been most frequently and best investigated in brass. This type has been designated as "normal grain growth," while the grain growth phenomena occurring in inhibited materials were, at times, referred to as "abnormal grain growth." However, since the latter term has been applied occasionally to the phenomenon of critical recrystallization, which also results in large grains although by an entirely different mechanism, in the present paper a different nomenclature has been adopted in order to avoid confusion. Typical of the grain growth in uninhibited metals and alloys is the continuous

Jan 1, 1947

By Richard B. Reese, George R. St. Pierre, Robert A. Rapp

The vapor pressures of pure iron and pure chromium have been measured using a Knudsen cell coupled with a mass spectrometer. The experimental results agree well with some previously reported data; heats of sublimation and vaporization have been calculated. From vapor pressure rr~easurernents, the activities of iron and chromium in their binary alloys have been determined for NcY = 0.10 to 0.65 over a 1400" to 1700~ temperature range. The activity of chromium in the liquid alloys was found to exhibit positive deviation from ideal behavior when referred to solid chromium as the standard state; however, for the activity of chromium referred to nonequilibrium undercooled liquid chromium as standard state, the activity behavior is almost ideal. ALTHOUGH the Fe-Cr system is important as the basic system of alloy steels, the thermodynamic properties of this system have not been thoroughly investigated at elevated temperatures. In view of the potential practical applications of such data as well as their contribution to alloy theory, further study of the Fe-Cr system was undertaken. In addition, further development of experimental techniques for equilibrium measurements at high temperature is required. The present research involved an application of the Knudsen effusion method in conjunction with a time-of-flight mass spectrometer. Belton and ~ruehan' have measured the activities in Fe-Ni and Fe-Co alloys by a similar method. Speiser, Johnston, and lackbburn' have determined the vapor pressure of pure solid chromium between 1283" and 1561°K by a Langmuir free evaporation technique. The vapor pressure of chromium was described by the expression: over the temperature range 1283" to 1561°K. McCabe, Hudson, and paxton3 have measured the vapor pressures of pure iron and pure chromium by the Knudsen cell technique around 1500°K. The vapor pressure and heat of sublimation at O°K, AH,", for pure chromium agreed within experimental error with the measurements of Speiser et al. at 1200°C. Kubaschewski and HeYmer~ determined the vapor pressure of pure solid chromium in the temperature range 1170" to 1400°C by the Knudsen effusion technique combined with a radioactive tracer analysis of crS1. Their results agreed with the work of previous investigators. Edwards, Johnston, and Ditmars5 have measured the vapor pressure of pure solid iron by the Langmuir technique between 1356" and 1519°K. The vapor pressure of solid iron in the temperature range studied was given by: The data of McCabe, Hudson, and paxton3 on the vapor pressure of pure iron around 1500°K by the Knudsen effusion technique were in good agreement with those obtained by Edwards et a~.~ Hultgren, Orr, Anderson, and Kelley give the selected values for the AH: of pure iron and pure chromium as 98,990 *200 and 94,340 * 500 cal per mole, respectively. These values are the average values determined in the several investigations by different methods. The Fe-Cr phase diagram7 is shown in Fig. 1. Previous determinations of activities in this system have been carried out by several investigators, but most of the work has been done on solid alloys. Using a Knudsen effusion method with cr5', Kubaschewski and Heymer4 reported that the Fe-Cr system exhibits positive deviation from the ideal behavior for compositions ranging from NCr = 0.0398 to 0.699 at 1170"

Jan 1, 1969

By E. C. Wright

FOR many years the cost of making pig iron and steel in the Birmingham district has been about the lowest in the United States. The close proximity of the important raw materials such as coal, iron ore, limestone, and the large available scrap supply made it possible to assemble all of the important ingredients necessary for steel- making with only nominal costs for transportation. Both iron ore and coal were being mined in this district at one time for about $1 per ton from underground operations. At that time mining wages were low everywhere and the labor rate in the South was considerably below that of other mining districts. This situation persisted until the emergence of labor unions as an economic and political force, emigation of southern labor to northern plants, and continued growth of industry in the South in the years following the depression of 1932. Since that time union organizing of miners and steel workers throughout the nation has increased labor costs in mining and steelmaking. This influence has been felt particularly in underground mining operations since the proportion of labor cost to total cost is still high. The previous advantage in basic labor rate in the South has been almost entirely eliminated by the equalization of labor rates in basic industries by national unions. Since 1945 these influences have been especially noticeable in increasing the cost of mining coal and iron ore in the South. The northern steel districts are still being largely supplied with iron ore from the Minnesota open-pit mines and the cost of this ore has not increased nearly as much as the cost of ore obtained from underground mines in Birmingham. A similar situation exists in coal mining; the thinner seams in Alabama are not so amenable to mechanization as the northern mines and, as a result, the output per man-day in southern mines is only about three tons of coal as compared to five or six tons per man-day in the large captive mines of West Vir-

Jan 1, 1950

By P. A. E. Armstrong

For hardening, the steel should be heated just above the critical temperature, as a properly forged steel quenched from this heat has some toughness, with maximum hardness and density. The quenching bath should be kept at approximately a constant temperature. In drawing or tempering, longer time periods at lower temperatures are better than the shorter periods at higher temperatures. A recent questionnaire brought out the following facts: The double-arc, double-taper bit and cross bit give the best service; resharpening of the drill steels most frequently was caused by wear of gage; chipping of bit was, with one exception, the second cause; breakage of shank was with one exception, the third cause; upsetting of bit, upsetting of shank, and breakage of body were the fourth cause. The direct cause of the necessity of resharpening given was poor heat treatment first, and faulty steel and severe rock conditions second. Rock-drill Steel By N. B. Hoffman Much of the drill steel produced in America is manufactured into hollow rods. After all forging has been finished the entire bar should be thoroughly annealed and heat trcated before the point is hardened and tempered, at least where the drill has heavy duty, such as working in deep holes and hard rock. A large number of tools of like character and doing work requiring similar properties are now being made of alloy steels; for instance a steel with a carbon content of 0.75 to 0.85 per cent., manganese 0.25 to 0.35, phosphorus under 0.020, sulfur under 0.030 and vanadium 0.18 to 0.23 has proved very satisfactory for chisels. A steel of this type properly manufactured will be far superior to the ordinary carbon steels, while at the same time is one whose price range should not prove prohibitive. Much of the cutting efficiency of a drill depends on proper heat treatment. This vanadium steel has a far greater safe hardening and forging range than ordinary carbon steels, making it more nearly foolproof. It will harden nicely at 1400" I?. but will also harden well and satisfactorily at 1550" F. retaining its quality of hardness and toughness in either case. Drill Steel from Hollow Ingots BY P. A. E. ARmstrong Hollow drill steel is made from a drilled billet with a sand-filled core or the drilled, pierced, or the drilled and pierced billet, not sand-filled, is rolled down over a projectile or ball much the same as in ordinary pipe manufacture. The first is the method generally used in this country; the second is used largely in Sweden. Swedish hollow drill steel has a

Jan 1, 1922

By C. S. Sivil

To modern civilization the platinum metals are of inestimable value. Their distinctive properties, both physical and chemical, render them indispensable in an age in which the processes of the laboratory are becoming an essential part of the daily life of the world. Generally, their function, though vital to particular processes, is not spectacular, and so remains unknown to all except the operators. EARLY METHODS OF MANUFACTURE The properties of platinum were recognized as of prime importance for scientific work at. a very early date, probably between 1750 and 1760. The difficulty of making articles from it seemed almost insurmountable, because no means of attaining the temperature necessary to melt it were known at that time. It is true that solid platinum could be obtained by fusing the metal with a more volatile metal such as arsenic, which was subsequently driven off by baking, but such a method, at its best, would give only a very brittle product, which was totally unsuitable for the purposes for which it was intended. Little, if any, progress could be made until it was discovered that platinum sponge, heated to white heat and hammered in an iron or clay mold, would metallize and retain the shape of the mold. This was a process that could not be wholly satisfactory but from it developed the method of pressing the sponge in a mold and forging it at white heat into wire or sheet. At present a somewhat similar process must be used for fabricating articles of tungsten, molybdenum and other metals of high fusing point, as with these metals we face today the same problems that the scientists of the eighteenth century encountered with platinum, but possibly the next significant advance in the metallurgy of these metals will be the devising of means to melt and cast them.

Jan 1, 1931

By J. B. NEALEY

THE common method of shale mining, drilling, shooting and steam-shovel loading, is fast giving place to a comparatively new method which is purely mechanical. This machine is known as the shale planer and takes a cut from a very large face, 50 ft. or more in height. As shale deposits are usually stratified, the quality varying with the stratification, a very uniform product is obtained with this planer, for its "cut" is across the entire face, vertically. This planer was designed and built some 15 years ago by J. M. Powell, president of the Indiana Drain Tile Co., Brooklyn, Ind. Unevenness in mixing the material from the different layers in the shale deposit of this company was causing considerable fluctuation in the firing- shrinkage and color of the ware produced, thus lowering the quality. Some method of maintaining a uniform proportion was vital and this planer was therefore devised. Its capacity was approximately 175 tons daily: cut, mixed and loaded.

Jan 1, 1929

By O. P. Chisholm

The most noticeable change in lead smelting over the past few years has been the increase in the smelting rate of lead blast furnaces. For several years a great deal of attention has been paid to the preparation of the blast-furnace sinter charge but more recently the plan has been to incorporate- almost the entire makeup of the blast-furnace charge, excepting coke and scrap iron, at the sintering machines. Formerly, sintering machines were used primarily for removing, sulphur and for agglomerating finely divided material both sulphide and oxide in character. Limestone flux usually was so proportioned that a relatively large amount was added to the furnace charge direct. This procedure was also followed with oxidized ores, which were purposely crushed coarse' so that they would be adaptable for direct smelting on the furnace charge. In later years it has been the tendency in western smelters to include practically all of the limestone and oxidized ores in the sinter charge. This has been somewhat more costly because fine crushing is required for sintering purposes and because these oxidized materials were given additional processing through the sinter plant. The addition of such oxidized materials to the usual charge to be sintered, brought about, in certain instances, a deficiency in heat ordinarily supplied by the sulphide constituents of the charge. This heat deficiency has been remedied by the addition of carbonaceous fuel, in the form of finely crushed coke breeze, or in a few instances by the addition of zinc retort-plant residues. The enhanced gold price has stimulated the mining of crude siliceous ores throughout the Western States and in the smelting of such ores more limestone is required for fluxing. Shipments of gold-bearing pyritic concentrates to Western smelters have increased, and the combination of increased silica, limestone and pyrite has increased the percentage of slag, which, in itself, is an aid in .securing smoother and more rapid smelting in the blast furnace. By the addition of these substances, the percentage of zinc in the slag has been appreciably lowered. at many plants, with resultant benefit to smelting speed at the blast furnace. This increase in slag formation with lowered zinc content has caused also perceptible lessening of the amount of lead on the charge and this has benefited the blast-furnace smelting. Although a satisfactory sinter is fundamental in increased rate of bullion production per furnace, there has been a trend over the list four or five years to decrease the percentage of coke and increase the percentage of scrap iron and limestone on the blast-furnace charge. As a result of these changes in practice certain blast furnaces, without any mechanical change, have doubled or tripled their tonnages. For furnaces whore the volume of air is recorded, records show decidedly larger air volumes with a comparatively small increase in air, pressure, or, none at all.

Jan 1, 1941

By Joseph Jensen

No outstanding example of an important producing unit operation exists in California today where the competitive drilling drainage feature is or was entirely eliminated We need not feel, however, that the thought of unit operation had its birth in 1924, when Henry L. Doherty named and sponsored it so strongly before the American Petroleum Institute and our own organization. No man or company in California ever drilled a wildcat well without exerting every possible effort to get all of the structure, so as to control drilling and avoid competition. Overproduction did not begin in 1923, so there has always been the wish to avoid it. In this state the practice of selling acreage around a wildcat has not been followed, except possibly in rare instances. The operator drilling the wildcat knew he must pay the bill alone, so he endeavored to get the benefit of his effort by tying up all of the land around his well and by so planning his different lease obligations as to avoid as much offsetting as possible. If he failed to get all of the land, it was because someone's price was too high, some other oil man also had the same idea and already held some lands, a competitor took leases away from him while his work was still incomplete, or (as was so often the case) the hidden structure when developed did not prove to be where the wildcatter thought it would be. The last named condition often led to a forced drilling campaign by the last leases secured and thus to serious drilling drainage problems. Ownership of the Land The land situation differs a great deal in various parts of the state. In the San Joaquin Valley, all the land is surveyed into sections and townships. Railroad land grants embraced a part of the land. In the areas that were developed at an early date, as at Kern River, Coalinga, McKittrick and the Sunset-Midway field, such land as the railroad company's diligent land department had been unable to sell for a song as grazing land still remained in its ownership. Operation and ownership

Jan 1, 1930

By C. Kremer Bain

UNDER present economic conditions the necessity of mechanizing the mines of our country has become a very important problem. More and more mines are looking toward increased or complete mechanization of their operations, so in the writer's opinion it is quite pertinent that some of the associated problems that accompany such a program be pointed out. The following generalization on attempting a comparatively slight change in mining methods at the Southeast Missouri properties of the St. Joseph Lead Co. is an attempt to point out to anyone faced with a mechanization program that much time and C. KREMER BAIN, Member AIME, is Assistant to General Manager, St. Joseph Lead Co., Bonne Terre, Mo. AIME Sun Francisco Meeting, February 1949. TP 2743 A. Discussion (2 copies) may be sent to Transactions AIME before March 31, 1950. Manuscript received Dec. 27, 1948; revision received Oct. 13, 1949. effort can be saved, and many headaches avoided, if company policy can be established whereby everyone in the organization from the top down is desirous of improvement and is working towards the common objective. Any changes in mining methods, machinery, and so on, must entah coordination of all the other phases of mining as they all have to mesh as accurately as a smooth running chain of gears if satisfactory results are to be obtained. The purpose of this paper is to point out some of the problems which :have to be surmounted when any mechanization program is attempted, rather than to go into the mechanical details and actual operating data of the equipment employed. After all, machines have to be adapted to best suit the local conditions, so no general formula can be given that would apply to other properties. Although St. Josepll Lead Co. has been mechani-cally-minded for a number of years, as shown by the fact that over 110 million tons have been loaded mechanically since 1922, any further mechanization or changes always present a problem. When our ore bodies were of great height and area the breaking and loading were developed to a high degree of efficiency according to known standards. But in recent years, when our ore bodies became smaller and more scattered, the amount of tonnage we were able to break was not sufficient to supply our shovels with enough rock to keep them working to capacity. Our first step in attempting to rectify this situation was to develop a technique of moving the shovels to the broken ore in various stopes, which sometimes entailed a move each shift. A shovel is not producing when being moved, so within the last two years we have been endeavoring to devise some means of getting more rock broken in these smaller stopes and it was then that we became interested in jumbo drilling. To illustrate the fact that mechanization is a process of a chain of developments rather than a stroke of genius can best be shown by a general summary of conditions and obstacles which were encountered in our present attempt to establish template drilling of a standardized round. Our first jumbo was more or less the conventional type with two machines mounted on a crossbar. This arrangement proved to be impractical to duplicate satisfactorily the regular routine of slabbing in a more or less radial pattern as carried out by column drilling. One machine was either too close to or too far from the face and there was another disadvantage in that one drillman was frequently delayed while waiting for his partner to bottom a hole. Our next step was to eliminate the crossbar so the machines could operate independently of each other, but we still encountered the same objections mentioned above except that one drillman was free to drill three holes instead of one in a vertical plane independently of his partner. Time studies while trying to adapt the jumbo to the regular slabbing practice as accomplished by column drilling, revealed that twice as much time was spent in maneuvering the jumbo into position and aligning the holes as was consumed in drilling.

Jan 1, 1951

By C. Kremer Bain

UNDER present economic conditions the necessity of mechanizing the mines of our country has become a very important problem. More and more mines are looking toward increased or complete mechanization of their operations, so in the writer's opinion it is quite pertinent that some of the associated problems that accompany such a program be pointed out. The following generalization on attempting a comparatively slight change in mining methods at the Southeast Missouri properties of the St. Joseph Lead Co. is an attempt to point out to anyone faced with a mechanization program that much time and C. KREMER BAIN, Member AIME, is Assistant to General Manager, St. Joseph Lead Co., Bonne Terre, Mo. AIME Sun Francisco Meeting, February 1949. TP 2743 A. Discussion (2 copies) may be sent to Transactions AIME before March 31, 1950. Manuscript received Dec. 27, 1948; revision received Oct. 13, 1949. effort can be saved, and many headaches avoided, if company policy can be established whereby everyone in the organization from the top down is desirous of improvement and is working towards the common objective. Any changes in mining methods, machinery, and so on, must entah coordination of all the other phases of mining as they all have to mesh as accurately as a smooth running chain of gears if satisfactory results are to be obtained. The purpose of this paper is to point out some of the problems which :have to be surmounted when any mechanization program is attempted, rather than to go into the mechanical details and actual operating data of the equipment employed. After all, machines have to be adapted to best suit the local conditions, so no general formula can be given that would apply to other properties. Although St. Josepll Lead Co. has been mechani-cally-minded for a number of years, as shown by the fact that over 110 million tons have been loaded mechanically since 1922, any further mechanization or changes always present a problem. When our ore bodies were of great height and area the breaking and loading were developed to a high degree of efficiency according to known standards. But in recent years, when our ore bodies became smaller and more scattered, the amount of tonnage we were able to break was not sufficient to supply our shovels with enough rock to keep them working to capacity. Our first step in attempting to rectify this situation was to develop a technique of moving the shovels to the broken ore in various stopes, which sometimes entailed a move each shift. A shovel is not producing when being moved, so within the last two years we have been endeavoring to devise some means of getting more rock broken in these smaller stopes and it was then that we became interested in jumbo drilling. To illustrate the fact that mechanization is a process of a chain of developments rather than a stroke of genius can best be shown by a general summary of conditions and obstacles which were encountered in our present attempt to establish template drilling of a standardized round. Our first jumbo was more or less the conventional type with two machines mounted on a crossbar. This arrangement proved to be impractical to duplicate satisfactorily the regular routine of slabbing in a more or less radial pattern as carried out by column drilling. One machine was either too close to or too far from the face and there was another disadvantage in that one drillman was frequently delayed while waiting for his partner to bottom a hole. Our next step was to eliminate the crossbar so the machines could operate independently of each other, but we still encountered the same objections mentioned above except that one drillman was free to drill three holes instead of one in a vertical plane independently of his partner. Time studies while trying to adapt the jumbo to the regular slabbing practice as accomplished by column drilling, revealed that twice as much time was spent in maneuvering the jumbo into position and aligning the holes as was consumed in drilling.

Jan 1, 1951

By J. W. JESSUH

TO certain people the name of Northern Rhodesia brings only a vague recollection of a distant country somewhere in Africa; to others, it means a big game territory and the opportunity for excellent shooting; to some, a land of sunshine and peace; but to mining men the name signifies the land where the latest discoveries of copper ore are astonishing the mining world and bid fair, in a few years, to make Northern Rhodesia one of the largest copper- producing countries. There is a fascination about this part of the globe that is somewhat similar to southern California, and at the same time there is that feeling of mystery peculiar to a tropical climate. Perhaps it is the isolation, the fear of wild animals, or the influence of an undefinable something which cannot be expressed.

Jan 1, 1931

By A. Muan

Liquidus data are presented for mixtures in the ternary system FeO-Fe2O3-SiO2 in equilibrium with a gas phase with O2 pressures ranging from 10-10.9 to 1 atm. Data obtained are combined with previously published data to construct lines of equal 02 pressures and lines of equal CO2/H2 mixing ratios along the liquidus surface. Courses of crystallization of selected mixtures under conditions of constant total composition, constant O2 pressures, and constant CO2/H2 mixing ratios are discussed. PHASE equilibrium studies of silicate systems where iron is one component are complicated by the fact that iron readily occurs in three different states of oxidation: Fe3+, Fe2+, and Fe0. Success or failure in work with iron silicate systems is to a large extent dependent on control of the oxidation state of iron and all investigations therefore must be carried out under carefully controlled atmospheric conditions. Silicate systems containing only strongly electropositive metals (like Na+, Ca2+, Mg", etc.) can, for simplicity, be treated as condensed systems, that is, the gas phase can be neglected and the phase relationships discussed in terms of the phase rule written in the well known simplified form P + F = C + 1. In the case of iron silicate systems, however, the composition of the condensed phases varies with the gas composition, and a complete picture of phase relationships can be obtained only by varying the gas composition over a wide range. In order to understand the phase relationships in the more complicated multicomponent silicate systems with iron oxide as one of the constituents, a knowledge of the ternary system FeO-Fe2O3-SiO2 is essential, since it constitutes a bounding portion of all such systems. It was with this in mind that the present study was undertaken. Previous Work A considerable amount of work has been done on various aspects of the chemistry and metallurgy of systems containing silica and iron oxides. The two bounding binary systems FeO-Fe2O3 and FeO-SiO2" The first attempt to obtain information on phase relationships of iron oxide-SiO, mixtures at different 0, pressures was made by Greig.' Darken" determined the melting points of iron oxide on solid silica under various atmospheric conditions. Darken did not determine experimentally the composition of the melts at liquidus temperatures but discussed very ably the principles involved in applying the phase rule to the system. In a recent study Schuhmann, Powell, and Michal8 determined experimentally the liquidus surface of a portion of the ternary system and combined the new information with data in the literature to construct a phase diagram. Their method was briefly as follows: Homogeneous mixtures with various contents of SiO2, FeO, and Fe2O3 were made up by melting together stock mixtures in various proportions. Samples of the homogeneous mixtures, the compositions of which were determined by chemical analysis, were then heated in platinum crucibles in an inert atmosphere until equilibrium among the condensed phases was achieved. The samples were quenched to room temperature and the phases present determined by microscopic examination. Assuming that no change in composition takes place during the equilibration run in inert atmosphere, the liquidus surface can be determined, but no information is obtained regarding the partial pressures of 0, of the gas phase in equilibrium with the condensed phases. The author's method, to be described in the next section, permitted the location of points at the liquidus surface as well as a calculation of the corresponding partial pressures of O2. Experimental Method General Procedure: The standard quenching technique was adapted for a study under controlled variable atmospheric conditions. Premelted mixtures of silica and iron oxides in platinum envelopes were held at constant temperature under chosen atmospheric conditions until equilibrium was reached among solid, liquid, and gas phases. The sample was then quenched to room temperature, the phases present identified, and, for the most significant runs, the composition was determined by chemical analysis. The corresponding partial pressure of 0, was calculated from known equilibrium constants of the gas reactions occuring in the furnace atmosphere. Materials: Starting materials were oxides of commercially highest available purity; cp silicic acid was dehydrated by heating to 1350°C for 6 hr and cp Fe2O3 was dried at 400° C for the same length of time. Samples of 10 g were made up by mixing

Jan 1, 1956

By C. H. Loux

THIS paper deals primarily, with the advantages realized from the adoption of methods more suitable than those previously used. The improvements noted include: (1) modification of practice in shrinkage stoping, (2) use of sublevel caving over grizzlies, (3) improved haulage and loading, (4) use of contract wages wherever possible. The Washington mine is on Jonestown Hill, one mile south of Oxford, in northwestern New Jersey. It is producing 16,000 tons of concentrates a month, which are being shipped to the Alan Wood Steel Company's furnaces at Swedeland, Pennsylvania.

Jan 1, 1933

By F. F. Claussen

The method of making silver ingots in use at this Mint being radically different from that employed at any other Mint of the United States or, so far as known to me, any Mint in the world, there may be some interest in a description of the apparatus used and a brief history of its distinguishing feature, viz., the rotary ingotmould, which, though not a recent improvement, is comparatively unknown. The furnaces used for silver-ingot-melting are four in number and have a capacity of some seventy thousand standard ounces of silver per day of eight hours. This output is increased, when the exigencies of the service demand it, to one hundred thousand ounces. They are built of fire-brick and elevated 21/2 feet from the floor of the melting-room, in order to have space to place iron boxes and to work, in case a crucible breaks in the furnace and its contents run into the ash-pit. The furnaces are circular in horizontal section, 2 $ feet in diameter and 29 feet high inside in the clear, and rest on castiron plates, with top-plates of the same, and sides encased in boileriron. The furnace-covers are also of cast-iron, dome-shaped, and are handled by means of a small crane and lever. The furnaces stand in sets of two, and one crane and one ingot-machine serves two furnaces. The crucibles used are made specially for this purpose of a mixture of black-lead and fire-clay; the size known as No. 200 will contain and safely melt, without danger of slopping over, from 8600 to nearly 10,000 ounces of standard silver; and this is the usual weight of the ingot-melt at this Mint, as against 1800 ounces at the Carson City mint and 2600 to 3000 ounces at Philadelphia and San Francisco. Each crucible will endure, on the average, ten melts. The crucible stands in the center of the furnace, on the bottom of an old one, cut down to a height of about three inches. The fuel used is coke. Experience has shown that, notwithstanding the higher first cost, Connellsville coke is cheaper than Alabama coke and much more suitable to the work. A small triangular black-

Jan 1, 1888

By J. B. Austin

Jan 1, 1945

By Samuel M. Dunaway

INTRODUCTION ASARCO Incorporated purchased the East Tennessee Zinc Mines of the American Zinc Company and commenced operating on November 29, 1971. Presently, three mines are operating producing 6620 t/d (7300 stpd). The ore mined is sphalerite which occurs In lower Ordovician carbonates of the upper Knox Group and occurs in open space and fracture filling. Orebodies range from 3 to 46 m (10 to 150 ft) thick with dips from flat to 20º. The mining method is random room and pillar modified by shrinkage and bench stoping. Like other mining departments, the mining group at the Tennessee Mines Division is constantly looking for methods to improve productivity and safety and to reduce mining costs. This involves testing new equipment, trying new ore extraction ideas and making mining plant alterations to meet changes in operating conditions. The areas of change that will be described in this paper are longhole raising, jumbos and LHD loading, shaft sinking, conveyor transport of ore and sublevel haulage developments. LONGHOLED RAISES Raise driving has always been a hazardous occupation for miners and today it is becoming more difficult to get competent people for this kind of work. This problem has led us to seek an easier, safer way in which to excavate raises. The first longhole raises were excavated in the early 1970's using a Gardner-Denver air trac equipped with a PR-123 rock drill. The machine used 38 mm x 244 cm (1 ½ in x 8 ft) round rods with rope

Jan 1, 1977

By Paul C. Merritt

The story now unfolding on the Mesabi Range is more than just another chapter in the continuing history of iron mining. It is an epic of foresight, research and pioneering instinct just now culminating in the rapid growth of a new industry hardly more than ten years old. And that growth has been impressive. In the decade that has passed since Reserve Mining Co. blazed a trail as the first successful large- scale commercial taconite operation, the number of plants now existing or soon to be operating has grown to six. From Reserve's initial capacity of 3 million tons of pellets per year, total production capacity on the Range has surged to 31.5 million tons while capital investment has leaped from $300 million in 1955 to almost $1 billion today. During the past year alone, more than $500 million has been committed to these projects, an amount probably greater than that going into any other single mining area in the world. There is more yet to come.

Jan 10, 1965

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

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

Jan 1, 1962