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By A. E. Martin, Gerhard Derge

IF the molecular constitution of molten slags were better known, the nature of chemical reactions in slags and between slags and metals could be better understood and as a consequence might be better controlled. Constitutional information can be obtained by studies on either the molten or the solidified slags. Valuable as the studies on solidified slags admittedly are for many purposes, especially as control methods in steelmaking, they are always of questionable value in giving information on the molecular constitution of liquid slags. However, the characteristics of molten slags such as viscosity, rates of diffusion, and electrical conductivity can be determined experimentally and interpreted along with other knowledge on slag-metal and slag-gas reactions so as to provide direct information on liquid slags. Metallurgists are accustomed to regard reactions in molten slags as involving only neutral molecules, whereas it is quite possible that ionic constituents are actually involved. For example, the dissociation of calcium silicate usually is represented as Ca2SiO4 = 2CaO + SiO2 although a reasonable alternative would be to write Ca2SiO4 = 2Ca+2 + Si04-4 Such ionic dissociation has been suggested frequently without adequate experimental proof. This paper deals especially with electrical conductivity measurements on slags of the blast-furnace type. These measurements were made to determine whether or not slags are ionized and, if so, to provide a qualitative estimate of the extent of ionization. Electrolysis experiments that indicate the identity of the ions present are also reported. Since the presence of ions has not been considered carefully in modern slag studies, the relevant literature will be reviewed. REVIEW of LITERATURE In 1906 Aiken1 obtained a patent for a continuous process of producing iron electrolytically by passing a direct current through a bath of FeO-SiO2 to which iron oxide was added periodically to maintain a uniform concentration. The patent also included the addition of CaO and MgO to the bath to lower its melting point. The silicate melts involved were thus in the same system as basic open-hearth slags but with higher FeO and lower CaO contents. Electrical conductivity measurements were made on some molten silicates by Doelter2 in 1907. Natural silicates, such as

Jan 1, 1943

By Morris Muskat

In preparing a well for pumping, observations are often made of the fluid level in the well bore or bottom-hole pressures at various times before equilibrium has set in. From a qualitative point of view one may immediately infer that if the rise in the bottom-hole pressure or fluid level is rapid the permeability of the sand about the well bore is large, and converse conclusions may be drawn if the rise is slow. However, a more quantitative estimate will give additional information of value, as will be shown in this paper. To derive such an estimate we may proceed as follows. Let h be the fluid height, above the sand face, at time t, and let yo be the average density of the fluid that enters the bore. The bottom-hole pressure, for a fluid height h will therefore be p = rogh, neglecting, of course, the friction drop in the well bore, while the fluid is rising, as may be justifiably done for most pumping wells. If a is the free area of the open-flow string—assumed to be uniform— the rate of production from the sand during the rise of fluid will be: where the last part of the equation merely indicates that, in general, the production rate Q must be considered as a function of the back pressure, and is determined by it alone. In fact, equation 1 shows that if the rate of rise of the pressure or fluid level is determined as a function of the height of rise, or p, for a number of values of the latter, this functional relation between Q and p will be immediately given. Conversely, if we know this functional relation, the rate of increase of p or h may be predicted, or, by observing the rate of rise of p or h some of the constants of the sand may be determined. Thus we may approximate the production from a well in a pumping state by that of a dead

Jan 1, 1937

By John S. Johnson

The maintenance cost, or renewal cost, in any preparation plant is a large item of expense and reflects in the total cost of producing and preparing the ton of coal. It is given constant study to the end that ways and means of controlling and reducing this proportion of the total cost may be developed. Study of this item of cost has proceeded along usual lines, which are: proper functioning of the maintenance organization; systematic and thorough inspection to prevent breakdonns; the making of repairs before renewals are needed; maintenance work done thoroughly the first time, instead of patching, study of parts needing frequent renewal or repairs or conditions resulting in delays, thorough knowledge of cost by the mall responsible for maintenance; and the use of special equipment and materials. This paper is to deal with special equipment and materials to reduce the maintenance cost hut before going into that I want to express an opinion on the general subject. Maintenance Organization Usually maintenance is taken care of by a group of men who perform their work on the off shift. The work is arranged by the operating official who should be thoroughly familiar with maintenance, so that materials needed may be made up for the particular job and waste of time in looking up materials be prevented. To perfect the maintenance organization, all operating attendants should be thoroughly trained to be familiar with all working parts of their equipment, to make a thorough inspection and to write out the slip for the work required. This requires job analysis, but it is worth the effort, because the attendant usually is better informed than anyone else about his particular equipment. The operating official can judge the scope of the work to direct the repair and to have material ready. Lubrication is an important item in maintenance, and a subject by itself. Usually the breaker oiler is designated to perform this task. This man should be picked for his ability and put in line for promotion to machinist. He should be trained as an inspector, as he is constantly visiting most parts of the breaker and has an opportunity to observe needed maintenance. The first thing is to lay out maintenance work and arrange to have it done; the next is to check the work and see that it has been properly done. This check should be made by the operating official, and through the attendant. The cost statement showing the various items of maintenance cost is not often understood by the man in direct charge. Cost sheets should be simplified and worked up by breaker sections; e.g., the cost of

Jan 1, 1947

By John S. Johnson

The maintenance cost, or renewal cost, in any preparation plant is a large item of expense and reflects in the total cost of producing and preparing the ton of coal. It is given constant study to the end that ways and means of controlling and reducing this proportion of the total cost may be developed. Study of this item of cost has proceeded along usual lines, which are: proper functioning of the maintenance organization; systematic and thorough inspection to prevent breakdonns; the making of repairs before renewals are needed; maintenance work done thoroughly the first time, instead of patching, study of parts needing frequent renewal or repairs or conditions resulting in delays, thorough knowledge of cost by the mall responsible for maintenance; and the use of special equipment and materials. This paper is to deal with special equipment and materials to reduce the maintenance cost hut before going into that I want to express an opinion on the general subject. Maintenance Organization Usually maintenance is taken care of by a group of men who perform their work on the off shift. The work is arranged by the operating official who should be thoroughly familiar with maintenance, so that materials needed may be made up for the particular job and waste of time in looking up materials be prevented. To perfect the maintenance organization, all operating attendants should be thoroughly trained to be familiar with all working parts of their equipment, to make a thorough inspection and to write out the slip for the work required. This requires job analysis, but it is worth the effort, because the attendant usually is better informed than anyone else about his particular equipment. The operating official can judge the scope of the work to direct the repair and to have material ready. Lubrication is an important item in maintenance, and a subject by itself. Usually the breaker oiler is designated to perform this task. This man should be picked for his ability and put in line for promotion to machinist. He should be trained as an inspector, as he is constantly visiting most parts of the breaker and has an opportunity to observe needed maintenance. The first thing is to lay out maintenance work and arrange to have it done; the next is to check the work and see that it has been properly done. This check should be made by the operating official, and through the attendant. The cost statement showing the various items of maintenance cost is not often understood by the man in direct charge. Cost sheets should be simplified and worked up by breaker sections; e.g., the cost of

Jan 1, 1947

By Maurice Ewing

THE purpose of this paper is to present the results of the application of the earth-resistivity method of subsurface investigation to the problem of locating seams of anthracite coal beneath a mantle of soil and subsoil. Details are given of the successful use of this method in locating the outcrops of anthracite seams in actual prospecting. The presence of the outcrop of an anthracite seam is indicated at points where electrical resistivity tests showed relatively low readings. The reason for, this is that in some localities the resistivity of anthracite was found to be about 0.0001 megohm-cm. compared to 1 to 200 megohm-cm. for shales and sandstones. For two reasons it is believed that the data sum-marized in this paper should be of particular interest. In the first place, most of the interpretations of the resistivity survey have been checked by subsequent drilling and some by the removal of the overburden and the exposing of the anthracite seams. It is infrequent that the oppor-tunity for checking results so thoroughly is given. In the second place, the fact that recent commentators 1.2.1 on the application of geophysical methods to mining have concluded that direct prospecting for anthracite and other types of coal is not promising makes the good results obtained more significant. So far as the authors can learn, the only previous experiment with electrical methods in the Pennsylvania anthracite field was one made by Sherwin F. Kelly in 1922, when he used the self-potential method at Wilkes-Barre4. The profile he made does not show a very marked correlation with the geologic cross section. Kelly points out that stray currents from electric motors in the mines undoubtedly affected his results, but the experience of the present authors with stray currents from mining machinery suggests the possibility that the potentials measured by Kelly were due almost entirely to this effect.

Jan 1, 1936

By Henry A. Stiff

The classification and correlation of water analysis data presents many problems which can be solved by graphic methocis. The pattern system, a new type of graphic procedure described in this communication, is believed to have several advantages over older methods. Examples of the application, of the pattern system to the solution of problems encountered in petroleum production are given. INTRODUCTION Several graphic methods for presenting analytical water data have been developed and are now in use.1,2,3,4 It is believed, however, that a recently developed type of graph called the "pattern" offers several advantages over other methods. This system presents a better picture of the total salt concentration than is usual in such graphs. The effect of dilution or concentration has been reduced to a minimum, and at the same time distinction between various types of water has been improved. The system is extremely versatile, yet so simple it can be plotted on ordinary graph paper and adapted to almost any type of filing system. DISCUSSION The essential feature of the pattern system is the graph shown in Fig. 1. Horizontal lines extending right and left from a vertical line at zero form the graph. Positive ions are plotted to the left while negative ions are plotted to the right. The figure immediately beneath each ion gives the scale. Most oil field waters can be plotted on a scale where 100 milli-equivalents of sodium and chloride and 10 milliequivalents of each of the other ions are represented by one scale unit. For highly concentrated brines, 1,000 milliequivalents of sodium and chloride and 100 milliequivalents of each of the

Jan 1, 1951

By Henry A. Stiff

The classification and correlation of water analysis data presents many problems which can be solved by graphic methocis. The pattern system, a new type of graphic procedure described in this communication, is believed to have several advantages over older methods. Examples of the application, of the pattern system to the solution of problems encountered in petroleum production are given. INTRODUCTION Several graphic methods for presenting analytical water data have been developed and are now in use.1,2,3,4 It is believed, however, that a recently developed type of graph called the "pattern" offers several advantages over other methods. This system presents a better picture of the total salt concentration than is usual in such graphs. The effect of dilution or concentration has been reduced to a minimum, and at the same time distinction between various types of water has been improved. The system is extremely versatile, yet so simple it can be plotted on ordinary graph paper and adapted to almost any type of filing system. DISCUSSION The essential feature of the pattern system is the graph shown in Fig. 1. Horizontal lines extending right and left from a vertical line at zero form the graph. Positive ions are plotted to the left while negative ions are plotted to the right. The figure immediately beneath each ion gives the scale. Most oil field waters can be plotted on a scale where 100 milli-equivalents of sodium and chloride and 10 milliequivalents of each of the other ions are represented by one scale unit. For highly concentrated brines, 1,000 milliequivalents of sodium and chloride and 100 milliequivalents of each of the

Jan 1, 1951

By J. H. Wernick

IN a study of the rate of decomposition of %-in. cubes of limestone, dolomitic limestone, and dolomite in a sweeping nitrogen atmosphere, Joseph, Beatty, and Bitsianes' found that the zone of calcination advanced at substantially a constant rate at a given temperature. The purpose of this paper is to show that their data indicate at least two processes occurring when the above carbonates decompose. It is suggested that there are two processes occurring consecutively, one the limiting process in a given temperature range and the other the limiting process over another temperature range. The data of Joseph and co-workers have been extended by use of the Arrhenius equation, Eq. 1, a relation beween the velocity constant k of a reaction and the absolute temperature T. d In k A ' dT Rr2 A is the activation energy in calories per mol (additional energy that must be added for an average molecule to react), and R is equal to 1.986 cal

Jan 1, 1955

By T. F. Witherbee

THE Fletcherville Furnace was built in 1864 and 1865, making its first blast from August until October of the latter year, when it was blown out to prevent its "bunging-up." Repairs were made in time to enable it to be blown in again December 12th, 1865, the blast ending October 7th, 1866. Total product 1921.15 tons iron, an average of 6.8.2.5 tons per day, from ores yielding 44.8 per cent. Consumption of charcoal 223.2 bushels per ton of iron. The furnace journal up to this time shows no record of furnace dimen¬sions, or temperature of the blast, but as near as can be ascertained, they were as follows, viz. Height of stack, 42 feet. Diameter of bosh, 11 feet. Angle of bosh, 7 1/2 inches to 12 inches rise, about 58°. Diameter of open tunnel head, 42 inches. Number of tuyeres 3; each 3 inches in diameter. Dam 15 inches high. Tuyeres 24 inches high. Tymp 22 1/2 inches high. Diameter of steam cylinder, 20 1/4 inches. Stroke 5 feet. Diameter of blast cylinder, 64 inches. The engine is direct-acting horizontal non-condensing. December 26th, 1.866, the furnace was again put in blast, having been considerably altered in the crucible; the height of stack, bosh, and tunnel head remaining as before. Six tuyeres were put in, three in each of the side arches. The hearth or crucible was rectangular in form, 3 feet wide x 32 feet long x 62 feet high. Inclination of bosh 58°. Height of tuyeres 26 inches ; nozzles 2 1/4 inches diameter. Temperature of blast estimated to be about 500°.

Jan 1, 1874

By R. H. Richman

Coarse-grained Fe-Ni-C martensites formed at subzero temperatures were strained in compression at room temperature and the plastic deformation modes examined as a funclion of carbon content. At very low carbon levels, defovmation occurs hy wavy slip; commencing at about 0.05 pct C, mechanical twinning accounts for an increasing proportion of the plastic flow. Beyond approximately 0.4 pct C the deformation appears to be entirely by mechanical twinning. The habit planes of the operative twin modes were determined to be (113), (0131, and "(089)" in decreasing frequency of occurrence. Some of the implicaticms of Ihe o6served deformation modes upon the structure and properties of ferrous martensites are discussed. METALLURGISTS have long sought to explain the mechanical properties of ferrous martensites, particularly the extraordinary hardness and strength of the high-carbon varieties. Until recently the lack of precise knowledge of the structure of martensite crystals was the most serious barrier to understanding; however, the advent of thin-foil techniques for transmission electron microscopy has removed much of the mystery from martensite structure. Observations by Kelly and Nutting,"' and many others since, indicate that Fe-C based martensite crystals are internally twinned to a degree dependent upon the carbon content, and that a martensite plate containing 0.8 wt pct C or more consists of a stack of twin-related lamellae with each lamella on the order of l00A thick. Such a structure would be expected to influence greatly all aspects of metallurgical behavior, and many of the properties of Fe-C based martensites have been rationalized accordingly. Recent independent experiments led Winchell and cohen3 to conclude that the strength of ferrous martensite is derived primarily from solid solution hardening of the iron lattice by interstitial carbon atoms. Strength contributions from precipitation, dislocation-atmosphere interactions, clustering, short-range order, crystallite size, and so forth, were considered to be of secondary importance. In the view of Winchell and Cohen, the twinned structure of martensite serves mainly to limit the effective length of dislocation lines in the lattice, and thereby confers an added measure of hardening. Few properties of metallic crystals are as sensitive to metallurgical structure as are deformation mechanisms. It is somewhat surprising therefore, that, except for metallographic evidence of mechanical twins in strained martensite,4 no systematic examination of plastic deformation

Jan 1, 1963

By Blake M. Loring, Robert A. Colton

MeltiXg procedures for most metals and alloys usually include some provision for the control of oxygen, since this element frequently has some undesirable effect on the properties of the metal or alloy concerned. In the melting of the various bronzes, this is especially true, since oxygen can be introduced into the melt in a number of ways, most of which are difficult to control. In making bronzes from virgin materials, oxygen is usually present in the commercial grades of copper used; electrolytic fire-refined copper ingots usually contain from 0.02 to 0.05 per cent oxygen. When ingot metal or scrap bronze is used in the charge, oxides are almost always present to some degree. Under certain melting conditions and in certain types of melting equipment the atmosphere over the metal may be highly oxidizing. This, of course, may be desirable in the melting practice used, but is certain to introduce appreciable amounts of oxygen into the melt, and that may not be entirely desirable. From the foundry viewpoint oxygen may have several harmful effects on bronzes. The formation of excessive amounts of oxides may produce drossy metal, which, in turn, means dirty castings and a potentially high rejection rate. It is claimed, too, that oxides in the metal may combine with hydrogen to form steam and thereby produce porosity in certain of the bronzes. The presence of certain refractory oxides, such as SnOz, may be undesirable from the viewpoint of making machining difficult, or as possible stress-raisers in the metal matrix. It is often said that excessive oxide present in the liquid metal makes the metal run sluggishly. Since it appears impractical to try to control the amount of oxygen introduced into the metal beyond taking the economical limit of precaution about charging dirty scrap, it would seem' that control of the oxygen content of the liquid metal offers the most promising approach to this problem. This might be done by using slags, or covers, or by the use of some element or compound added to the melt to remove oxygen preferentially. Most aspects of this problem have been considered and considerable work has been done along these lines. A reconsideration of the problem is indicated, however, by the controversial nature of the evidence at hand, especially on the possibility of using a chemical deoxidizer to control the oxygen content of bronzes. Choice of Deoxidizer The choice of the chemical agent selected as a deoxidizer would naturally depend first on the alloy in which it is to ~he used: in this particular case the alloy is Navy gun metal. In Table. I are listed a group of elements that might be considered as deoxidizers for bronze, with some of their properties that should be considered in

Jan 1, 1946

By Blake M. Loring, Robert A. Colton

MeltiXg procedures for most metals and alloys usually include some provision for the control of oxygen, since this element frequently has some undesirable effect on the properties of the metal or alloy concerned. In the melting of the various bronzes, this is especially true, since oxygen can be introduced into the melt in a number of ways, most of which are difficult to control. In making bronzes from virgin materials, oxygen is usually present in the commercial grades of copper used; electrolytic fire-refined copper ingots usually contain from 0.02 to 0.05 per cent oxygen. When ingot metal or scrap bronze is used in the charge, oxides are almost always present to some degree. Under certain melting conditions and in certain types of melting equipment the atmosphere over the metal may be highly oxidizing. This, of course, may be desirable in the melting practice used, but is certain to introduce appreciable amounts of oxygen into the melt, and that may not be entirely desirable. From the foundry viewpoint oxygen may have several harmful effects on bronzes. The formation of excessive amounts of oxides may produce drossy metal, which, in turn, means dirty castings and a potentially high rejection rate. It is claimed, too, that oxides in the metal may combine with hydrogen to form steam and thereby produce porosity in certain of the bronzes. The presence of certain refractory oxides, such as SnOz, may be undesirable from the viewpoint of making machining difficult, or as possible stress-raisers in the metal matrix. It is often said that excessive oxide present in the liquid metal makes the metal run sluggishly. Since it appears impractical to try to control the amount of oxygen introduced into the metal beyond taking the economical limit of precaution about charging dirty scrap, it would seem' that control of the oxygen content of the liquid metal offers the most promising approach to this problem. This might be done by using slags, or covers, or by the use of some element or compound added to the melt to remove oxygen preferentially. Most aspects of this problem have been considered and considerable work has been done along these lines. A reconsideration of the problem is indicated, however, by the controversial nature of the evidence at hand, especially on the possibility of using a chemical deoxidizer to control the oxygen content of bronzes. Choice of Deoxidizer The choice of the chemical agent selected as a deoxidizer would naturally depend first on the alloy in which it is to ~he used: in this particular case the alloy is Navy gun metal. In Table. I are listed a group of elements that might be considered as deoxidizers for bronze, with some of their properties that should be considered in

Jan 1, 1946

By K. A. Johnson, H. F. Yancey

Physical properties have been used for a long time in characterizing different kinds of coal, and such physical properties as friability and slacking have been included along with chemical properties in grouping coals according to the widely used system of classification adopted by the U. S. Geological Survey. Nevertheless, the usefulness of physical properties for classifying the different ranks or kinds of coal has been limited because it has not been possible to express these properties in definite form as numerical values. Because of the present wide interest in the formulation and adoption of a satisfactory system of coal classification, the Northwest Experiment Station of the U. S. Bureau of Mines, in cooperation with the College of Mines of the University of Washington, has recently completed a study of the physical and chemical properties of approximately 100 different coals ranging in rank from lignite to anthracite. Purpose and Scope For this investigation samples were collected in approximately 45 mines and prospects in Washington and 23 mines in other states. The following studies, in addition to proximate and ultimate analyses, were made of the samples: Determination of (1) friability, (2) slacking or weathering characteristics, (3) yield of products by low-temperature carbonization in a laboratory retort, and (4) agglutinating value. Most of the coals examined were subjected to each of the tests enumerated, but with coal of some ranks this was unnecessary in some instances, and in others it was not feasible to do the work involved. A report which includes the analyses of the coals and the details of the methods of examination used in the investigation is being published by the Bureau of Mines.' It is the purpose of the present report to show the results of the friability, slacking, low-temperature and agglu-

Jan 1, 1932

By Eugene P. Pfleider, Claus Freyberger

Generally, the different methods of financing new mining projects are not well understood by the engineers and supervisory personnel. Nor are the effects of these alternatives on depletion, taxes and profitability readily apparent to even the sophisticated management personnel without the aid of cash flow studies. Fortunately, with the advent of the computer it is possible now to simulate many different combinations of 1) equity, 2) loan and 3) production payment financing with little effort. A general computer program for cash flow analysis of mining ventures has been developed and applied as a case example to a 1967 feasibility study of the Underground Mining of Minnesota Taconite. The effects on profitability as measured both in rates-of-return and present value are presented for various financing combinations. In addition, percentage depletion rates were altered so as to measure the impact of this statuatory allowance. Based on the cost data as presented in the aforementioned 1967 feasibility study, and assuming 7% loans, the rates-of-return vary from 9. 9% to [00] % on equity variations and from 9. 9% to 11.4% on total invested funds.

Jan 1, 1969

By T. R. Cass, M. R. Achter

A technique for measuring the creep and rupture strength of nickel specimens bonded by sintered oxide layers has been developed for the investigation of the role of grain-boundary oxide in the oxidation strengthening of nickel during creep at 817 °C. Prom the inverse dependence of the rate of bonding on the thickness of the starting oxide, it is suggested that the rate of diffusion of Ni++ through NiO is the controlling process at the start of sintering. Cornparisons of the creep and rupture strength and of the microstructure of sintered couples with conventionul creep specimens suggest rupture in nickel is prevented by load-bearikzg, ikltergranular layers of oxide. A number of recent investigations have shown that at high temperature and low stress the creep-rupture strength of nickel and nickel-base alloys may be much greater in air than in an inert gas or vacuum.'-7 For example, at 817°C and 2500 psi, nickep failed in vacuum in 48 hr but not in air after 4000 hr, and a Ni-Cr-A1 alloy5 at 1038°C and 3000 psi failed in vacuum in 4 hr but not in air after 731 hr. Fig. 1 is a typical creep curve in air for materials experiencing this pronounced environmental strengthening. A common feature of these curves is the entry into a third stage of accelerating creep, concurrent with the for-

Jan 1, 1962

By R. J. C. Tait

INTRODUCTION Process Control at the Ecstall Concentrator begins in the open pit at the Kidd Creek Mine. While this paper, naturally, emphasizes the instrumental and technical features of the Process Control system within the concentrator itself, it would not be complete without some mention of the selective mining methods and grade control practices at the mine, and of certain features of plant design, which are simple, but highly effective, elements of the Process Control system. The success of the entire Process Control system, from pit to concentrate load-out, owes much to the high degree of cooperation and mutual understanding among all the operating departments at Ecstall Mining Limited and to the willingness of management to accept, from the start, an overall control philosophy based upon the inter-dependence of mining and metallurgical operations. INFLUENCES OF MINERALOGY AND METALLURGY ON MINE PLANNING AND PLANT DESIGN Mineralogically, the Kidd Creek ores are fine grained and mostly very complex. Because of complex mineral associations and extensive inter-locking, very fine grinding and regrinding of middling fractions are necessary and selective flotation requires a very delicate touch. Four separate concentrates are made for shipment to copper, lead and zinc smelters. The Process Control system is tailored to the metallurgical objectives of maximum recoveries of copper, lead, zinc and silver into concentrates of optimum quality, for maximum economic returns. For example, zinc and lead in copper con-

Jan 1, 1970

By Augustus Locke

THERE are three matters related to ore-hunting which I wish especially to discuss here: first, the paucity of the special writings applying to it; second, the failure of scientists to concern them-selves importantly with it; and, third, resting on these conditions, certain possible activities for economic geologists. First, as to the writings. Geological papers. are being produced in the United States alone at the rate of 10 to 12 shelf-feet per year.1 But papers specifically for the ore-hunter would go in a slim, annual pamphlet; all that have ever been written would go in a briefcase. The art of technical ore-hunting-geology conceived as a guide to ore-has only a scant literature.

Jan 4, 1922

By W. A. Longacre

IN the geophysical exploration program of the Cleveland-Cliffs Iron Co. on the Marquette Range of Northern Michigan, the vertical intensity magnetometer has been used to obtain magnetic anomaly maps of large areas. A network of magnetic base stations has been established and the relative vertical intensity at each station measured carefully with respect to a prime base. In the search for the relatively nonmagnetic soft red hematite ore, the magnetic exploration is indirect, involving the study of dikes, faults, contacts, and other structural features. It was found that the, magnetometer, adjusted to a scale value of approximately 40 y per scale division, was satisfactory for this type of exploration, although many magnetic anomalies were encountered that required the use of auxiliary magnets.

Jan 10, 1951

By George K. Burgess

The suggestion has often been made that it would be highly desirable, at least for certain grades of steel, to be able to control more certainly, by pyrometric measurement or otherwise, the temperatures of the operation of the open-hearth and other furnaces used in the manufacture of steel and iron. That the properties of the ingot and finally of the finished steel product are intimately related to the final temperatures attained by the metal in the furnace and to the temperature of casting, has been recognized by metallurgists for a long time, and this question has been very thoroughly treated, especially by Prof. Henry M. Howe, and by A. W. and H. Brearley.1 It is the object of this paper to demonstrate that in so far as casting temperatures of furnaces, steel ingots, and similar operations involving the temperatures of streams of iron and steel are concerned, well-known pyrometric methods may be easily applied—if certain recently determined corrections are made and precautions taken—with a relatively high degree of accuracy. Greater but not insurmountable difficulties will be encountered in the case of open-hearth furnace temperatures, while for those of the converter type a ready solution does not seem practicable. It appears that certain essential data have always been lacking in reporting observations such as those of Le Chatelier in 1892. Thus the correction to be applied for the characteristic radiation—or emissivity— has hitherto not been adequately taken into account nor the limitations of the several possible pyrometric methods clearly recognized. In view of the fact that in open-hearth practice the temperature to be measured in the furnace itself, in the stream of metal and slag and in the teeming into molds or ingots is usually above 1,500" C. (2,700" F.)

Jan 1, 1917

By John Wulff, H. H. Uhlig

Since its first mention in the literature in the eighteenth century12 the phenomenon of passivity in metals has stimulated much speculation and attendant controversy as to its nature and cause. No one of the numerous theories so far proposed has been generally accepted. ‡ Faraday,' in 1836, associated the passivity of iron with a protective film over the surface of the metal, which materially prevents or slows down reaction with corrosive environments. His theory was that oxidizing acids like nitric acid form an unstable oxygen or oxide layer over the iron surface, which protects the underlying metal from further attack. This concept was simple yet plausible, and without alteration has frequently been assigned in present-day discussions as explanation of the passivity of many metals. With the advent in recent times of stainless steels, it is not surprising that this oxide film theory of passivity proposed by Faraday has been used to explain the phenomenal corrosion resistance of stainless steels and other passive alloys. The passive alloys, such as the chrome-iron alloys, are supposedly covered with a protective oxide film, which forms on exposure of the alloy to air, is extremely stable and self-healing, and accounts for the remarkable resistance of these alloys to corrosion. Within the past few years, several investigators, following the theory of film protection, have attempted to gauge the resistance of the supposed film on steels. Brennert8 and Donker and Dengg9 determined the potential at which a negative ion (e.g., C1-) moving in an electric field reacted with the metal anode, as detected by increased current flow or change in potential of the steel electrode in an electrolytic cell. The potential corresponding to reaction Brennert called the film break-through potential.

Jan 1, 1939