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By B. F. Tillson

Mining may be defined as a general term for the working of valuable deposits of minerals, either organic or inorganic in origin, for their removal from the crust of the earth. Besides subsurface excavations, mining generically includes opencuts, clay pits and stone quarries, oil wells, sulphur wells, salt wells, placers, coal stripping, and the leaching of ore bodies. The origin of the word "mine" or "mining" is a matter of conjecture. A Celtic origin has been suggested since the Irish word mein, or the mwyn, meant ore, but it seems to have come from an olf French verb mineor, which meant to excavate, to make an underground passage as in the military appraoch to a fortification, sometimes called ?sapping.?

Jan 1, 1949

By D. H. Polonis, M. B. Kasen

AN unusual thermal etching phenomenon has been observed on the surface of a Cu-Si alloy. The observations were made during studies of vacancy condensation pit formation which were reported in previous papers.1,2 Figs. 1 and 2 are photomicrographs of the surface of a Cu-4.8 pct Si alloy after heating in vacuo (3 x X mm Hg) to 525°C and subsequently holding at that temperature for 16 hr in an impure (air-contaminated) argon atmosphere. Under these conditions preferential removal of silicon from the matrix by oxidation results in a surface which is entirely a phase overlying an a plus y structure. The light areas of Fig. 1 are regions in which very little thermal etching has occurred, while the majority of the surface has experienced severe etching. Similar regions in Fig. 2 are seen as plateaus above contours produced by net transfer of material from the specimen surface. Twin boundaries are also visible in Fig. 2. The difference in matrix mi-crostructure between Figs. l and 2 reflects the par- ticular orientation of low-index planes with respect to the surface of observation. Thermal etching contours of this type have been studied in detail by Hondros and Moore Both of the photomicrographs show that one or more dark spots are located approximately at the center of every protected area; where two spots are in close proximity, the protected areas have merged. The microstructures indicate that the anomalous resistance to thermal etching is related to the presence of these spots. Williams and Hayfield have shown that local regions of unusually high oxidation resistance can be caused by a surface monolayer of atoms with a work function higher than that of the base material. The result is an inhibition of the rate of electron removal from the base material and a decrease in the oxidation rate. The source of the protected layer may be either surface diffusion from contaminants on the specimen surface or pipe diffusion of solute atoms followed by migration across the surface. In the latter case the driving force is a difference in chemical potential resulting in a Gibbs adsorption phenomenon. In the present case, chemical polishing of the specimen surface precluded contaminants of a strictly surface nature. Consequently, diffusion of impurity atoms from within the lattice appears to be the most tenable explanation of the observed phenomena. The authors propose that the structures of Figs. 1 and 2 reflect the diffusion of impurity atoms along extended dislocations within the individual a phase grains prior to surface oxidation. The central spots within the protected regions are seen as sites of dislocation emergence which have become locally decorated with oxide in the manner discussed in Ref. 1. Williams and Hayfield observed protected regions adjacent to the grain boundaries of iron-contaminated copper which they attributed to the segregation of iron to the grain boundaries coupled with high dif-fusivity along the complex dislocation array at such boundaries. No evidence of such grain boundary protection was observed in the Cu-Si alloy; this

Jan 1, 1964

By Charles H. Eldridge, Robert J. Anderson

When a metal or alloy is poured into a mold, internal stresses are set up by the cont,raction in volume on passing from the liquid state at the temperature of pouring to the solid state at the ordinary temperature. It is assumed by the writers that all castings are internally stressed. That any casting is internally stressed is shown by its warping or distortion on maturing at the ordinary temperature, by warping or cracking on heating, or by cracking or distortion on machining. In the investigation made by the writers, the internal stresses in cast non-ferrous alloys were studied with a view to examining the effects of heat treatment (i.e., simple anneal) on the release of such stresses. Data have been obtained that show quantitatively that internal stresses can be removed by appropriate heat treatment. The investigation was limited to a study of the effect of heat treatment on stress release in cast rings of the 87:7:5:1 copper-tin-zinc-lead alloy. The writers are indebted to E. G. Fahlman for the method used for inducing stress in cast rings; to M. E. Boyd for microscopic examination and for other aid; and to G. B. Dalrymple for the chemical analyses. General Information While casting stresses have been discussed considerably, they have usually been treated in a general way, and so far as the writers know no measurements of the magnitude of internal stresses in castings have been reported. It has been suggested by many investigators, particularly in the case of steel castings, that castings are internally stressed, and that these stresses can be removed by annealing. In a casting, the internal

Jan 1, 1923

By Robert J. Anderson, Charles H. Eldridge

When a metal or alloy is poured into a mold, internal stresses are set up by the cont,raction in volume on passing from the liquid state at the temperature of pouring to the solid state at the ordinary temperature. It is assumed by the writers that all castings are internally stressed. That any casting is internally stressed is shown by its warping or distortion on maturing at the ordinary temperature, by warping or cracking on heating, or by cracking or distortion on machining. In the investigation made by the writers, the internal stresses in cast non-ferrous alloys were studied with a view to examining the effects of heat treatment (i.e., simple anneal) on the release of such stresses. Data have been obtained that show quantitatively that internal stresses can be removed by appropriate heat treatment. The investigation was limited to a study of the effect of heat treatment on stress release in cast rings of the 87:7:5:1 copper-tin-zinc-lead alloy. The writers are indebted to E. G. Fahlman for the method used for inducing stress in cast rings; to M. E. Boyd for microscopic examination and for other aid; and to G. B. Dalrymple for the chemical analyses. General Information While casting stresses have been discussed considerably, they have usually been treated in a general way, and so far as the writers know no measurements of the magnitude of internal stresses in castings have been reported. It has been suggested by many investigators, particularly in the case of steel castings, that castings are internally stressed, and that these stresses can be removed by annealing. In a casting, the internal

Jan 1, 1923

By J. Lemish

Considerable research has been conducted in Iowa in recent years on carbonate aggregate reactions in concrete. Groups outside the state have become active in the past few years after recognizing that certain carbonate aggregates are reactive in concrete. The paper reviews the nature and extent of the problem and a summary is given of research by the author and his associates. In recent years considerable research has been conducted in Iowa on carbonate aggregate reactions in concrete. The research is part of a general study on the behavior of carbonate rocks as concrete aggregates sponsored by the Iowa State Highway Commission. Research on carbonate aggregates has not been extensive in the past. Laughlin1 published one of the first papers on carbonate aggregates in 1928 and was followed by others, notably H. S. sweet,' B. Mather et al.,3 and K. Mather4 who emphasized the petrographic and physical aspects of carbonate aggregates. The recognition that certain carbonate aggregates are reactive in concrete has led to increased participation in research in the past few years by groups outside of Iowa. Significant contributions have been made by Swenson and Gillot,5 Hadley,6 and Chaiken and Halstead7 in work which emphasizes the expansion of carbonate rocks in alkaline environments and the reaction of carbonate minerals or dedolomitization with alkalies. It is the purpose of this paper to review briefly the nature and extent of the problem and present a summary of the research by the author and his associates. EXTENT AND NATURE OF THE PROBLEM The problem is the deleterious behavior of certain carbonate aggregates in concrete. It was first recognized in Iowa over 20 years ago when poor service records of certain highways were correlated with aggregates produced from the Glory and LeGrand quarries. Deleterious behavior of carbonate aggregates have been reported in Canada and, more recently, in New York and Virginia. As more knowledge is gained concerning the problem, distress in concrete related to carbonate aggregates may be recognized over a widespread area. The problem may potentially exist in the Midwest, the Northeast, and other parts of the country underlain by thick sections of carbonate rocks readily available for utilization as aggregates. The nature of distress in Iowa highways is a general weakening and deterioration of concrete characterized by progressive cracking and spalling away from joints and edges (Fig. 1). The distress generally occurs after 15 years of service and becomes progressively worse. Specimens of such concrete lack the toughness of sound concrete and break easily under the hammer in the manner of a soft brick. The matrix is generally highly carbonated and dark borders, or reaction shells or rims outline the argillaceous carbonate aggregate fragments (Fig. 2). Cracks observed in cores cut across the aggregates and concrete matrix. Although localized volume change (expansion) is associated with spalling, there is no definite field evidence in Iowa that excessive growth of concrete slabs has occurred. The experience with carbonate aggregates in Iowa indicates that the concrete deterioration is not the same as that induced by the alkali-aggregate reaction associated with siliceous aggregates. The principal difference is that in Iowa the distressed concrete is weakened throughout the slab. In concrete affected by the alkali aggregate reaction, the

Jan 1, 1961

By S. J. Aresco, A. A. Orning

This paper presents a scheme for determination of precision for the various steps in coal sampling, sample preparation, and analysis. It also gives resulting data on 100 American coals from various coal fields covering all ranks from lignite to low-volatile bituminous. The variances of the various steps of the process are studied as a function of the coal preparation, the top size of coal as sampled, and the ash content. To understand the variables that control the overall precision of coal sampling, sample reduction and analysis, there is need for measurement of the variances due to successive steps of the process. The purpose of the present paper is to study these variances as a function of the coal preparation, the top size of the coal as sampled, and the ash content. The sampling data included are from 100 individual preparation plants from various coal fields in the United States and cover all ranks of coal from lignite to low-volatile bituminous; various types of preparation; deep, strip and auger mines; and, in many instances, mixtures from two or more coal beds or types of mines. The collection of data is continuing, but sufficient work has been done to draw some important conclusions. Since the work was done in conjunction with the Bureau of Mines sampling of coal, the time that could be spent at any one preparation plant was limited. This, in turn, limited the number of samples that could be taken for each coal. For this reason, the results from various plants were pooled in blocks. Two major blocking categories were "raw" and "washed!' The raw coals had no preparation other than crushing and/or screening. The washed coals were prepared further by some combination of wet or dry mechanical cleaning. The categories were further divided ac-

Jan 1, 1965

By F. X. Tartaron

The comparison of actual energy of comminution with theoretical surface energy presents a wide gap. On the other hand, Solid State Theory presents a viewpoint that places actual energy of breakage in understandable relationship with the theoretical strength of materials. Therefore the physical background of comminution theory favors Kick's Law. A11 discussions of comminution theory appear farfetched when comparison is made of the actual energy of crushing with the energy input called for by thermodynamic theory. Quoting Taggart:' "The work required to crush halite was of the general order of 0.10 kg cm per sq cm of new surface produced (based on air percolation) whereas the theoretical energy of this new surface, based on thermodynamic calculation by a number of investigators is 1 x 10'4 kg cm per sq cm or the work expended was 1000 times the new surface energy — an indicated crushing efficiency of 0.10 pct." It is frustrating to probe into comminution theory with the prospect that the energy one is measuring is 99.9 pct waste energy. Do the laws of comminution deal with energy consumed by mineral breakage or with waste heat energy? There seems to be something wrong. Solid State Theory may provide the answer. The following statement is particularly apt to the situation: "The fundamental fact about metals and indeed all materials, is that they are much weaker than they should be. By this, we mean that if the stress required to cause a given plane of atoms to slip past a neighboring plane is calculated from basic atomic and Solid State Theory, the resulting number is some 1000 times too large to be accounted for by errors in approximations or assumptions. We know now that this is due to dislocations, and we even have a fair understanding of the details of the process by which dislocations make a crystal weak. An intriguing possibility which suggests itself, results from the discovery of very minute metallic crystals which are apparently free of dislocations and which have a strength approaching the ideal value for a perfect crystal." Here we have an extraordinary reversal of the situation. The actual energy for breakage is only one-thousandth the theoretical instead of 1000 times as given by Taggart. But the theoretical energy presented by Solid State Theory is the binding energy between atoms (or ions) in a crystal lattice. This is the kind of energy envisaged by Kick's law. The surface energy or the other hand corresponds to Rittinger's law. Comparison of theoretical with actual, on the basis of surface or on the basis of Rittinger's law, seems to present an absurdity; yet Rittinger's law is confirmed by an impressive array of experimental evidence. Comparison of theoretical and actual on the basis of Solid State Theory or, in other words, on the basis of Kick's law seems reasonable; yet there is not a scrap of evidence to verify Kick's law. The situation appears paradoxical, but the developments in the next section of this paper show that the paradox is a hint to a strange turn of events. ENERGY-WEIGHT FRACTION FUNCTION charles3 has presented a final equation showing the relation of energy consumed in comminution to size of product n{-1) a-n + 1 E is energy, C is proportionality constant, a and n are constants and k is the coarsest size in the ground product (size modulus). In the course of study of a large amount of experimental evidence, Charles discovered that in the general case, a-n + 1 approximated zero. For some reason, a and n differed only by unity. But if a—n + 1 = 0 within experimental error, then it is obvious that Eq. 1 states that it requires an infinite amount of energy to grind any sample to any size. This is a case where nature gives an absurd answer to a man-made mathematical equation, hence something is wrong with the equation. An adjustment must be made to fit the equation with experience. TO reveal the nature of the adjustment, the differential equation preceding the second integration in Charles' group of equations is given When Charles integrated the quantity xa-n it was almost impossible for him to realize that he was dealing with a special case of integration and that

Jan 1, 1962

GERARD B. ROSENBLATT,* Salt Lake City, Utah (written discussion?). -Mr. Eschholz attacks this problem from what appears to me to be the proper angle. He does not limit his viewpoint to the attainment of ideal results under conditions approximating laboratory practice, but rather discusses actual commercial conditions that must be maintained in large-scale operations, where continuity of service without expert attendance is one of the prime considerations. I am of the opinion that Mr. Eschholz has not given sufficient consideration to the commercial possibilities of what he describes as System B, the use of low-tension a.-c. industrial or lighting circuits for supplying power to Cottrell treaters through the medium of a step-up transformer and a synchronously driven rectifier, without the use of motor-generators. It is true that, to date, few installations on a large scale have used this system, but I believe that when the conditions of power supply are suitable, and when proper precautions are taken, this system can be used successfully and to advantage. where at present it is considered necessary to use motor-generator sets. In the average commercial Cottrell installation of any size, the motor-generator set is used for two purposes: (1) To isolate the industrial supply circuit from the Cottrell circuit. (2) To. afford, an easily operated and smooth system of control for the Cottrell treater voltage With proper engineering, both of these objects can be accomplished without the use of motor-generator sets.

Jan 10, 1918

By A. W. Schlechten, C. M. Hsiao

The apparent vapor pressures of a number of metal sulphides were determined by measuring their rate of weight loss when they were heated under vacuum. The calculated pressures are due in some instances to the volatility of the sulphide and in others to the decomposition pressure. FIE direct reduction of metallic sulphides, as in the precipitation method for lead or antimony, is not a widely used process today. However, it might be employed for the production of a number of metals if the operation were carried out under reduced pressures. Two general procedures are possible; the reducing agent could form a stable nonvolatile sulphide from which the valuable metal could be removed by volatilization or liquation. The other approach would be to choose a reducing agent which would form a sulphide that could be volatilized away from the valuable metal. A vacuum operation would serve to protect the sulphides and metals from oxidation and would increase the evaporation rates. A related process is the separation of metallic sulphides by selective volatilization either at atmospheric pressure or under vacuum. This procedure is already used commercially for the elimination of lead and cadmium as PbS and CdS from zinc calcines; it might well have other applications. To predict such processes it is necessary to know the relative volatilities of the metallic sulphides and to know whether they volatilize as sulphides or whether the predominant weight loss is due to decomposition. Such data would also be of value in studying problems such as the use of sulphides for refractories, as described by Brewer,] or in the evaluation of the theory of ore deposition from the vapor state, as proposed by Brown.' Qualitative statements concerning the volatility of metallic sulphides can be found frequently in the literature and are well summarized by Mellor, but accurate determinations of rates of evaporation or vapor pressures are very scarce. Kelly" lists vapor pressure data only for PbS; his reference being to the work of Schenck and Albers,4 who measured the vapor pressure of PbS by a dynamic method between 850" and 995°C. More recently Veselovskii5 has determined the vapor pressures of the sulphides of antimony, lead, cadmium, and zinc at temperatures ranging from 360" to 1000°C using Knudsen's method. A second Russian worker, Pogorelyi,6 determined the vapor pressures of CdS and ZnS at temperatures from 900" to 1250°C. The results obtained by these workers are shown in subsequent graphs in comparison with the data of this paper. Brewer and coworkers1 have studied some of the metallic sulphides to determine their suitability as refractories in vacuum. Veselovskii's determinations on PbS checked well with those of Schenck and Albers, and his determinations of CdS check almost exactly with Pogo-relyi. For the vapor pressure of ZnS the data of Veselovskii and that of Pogorelyi are in fair agreement, as shown in Fig. 1, but it should be pointed out that Lumsden7 has discovered that the equation given by Veselovskii for the vapor pressure of ZnS: - 14,200 log P9.495 is in error by a factor of ten when compared to the experimental data. In contrast with the scarcity of data on vapor pressures, the decomposition pressures of many metal sulphides have been determined and are summarized by Smithells.8 Theoretical Considerations The experiments described in this paper consisted of determinations of the rate of weight loss of certain metallic sulphides under very low pressures at different temperatures. These data plus observation and analyses of the products reveal the mechanism of the weight loss and also provide a basis for the calculation of the vapor pressure or apparent vapor pressures of the sulphides.

Jan 1, 1953

By L. L. McDaniel

During the past few years a nuinber of improvements in smelting and power equipment have been made at the Douglas smelter of the Phelps Dodge Corporation at Douglas, Ariz. In the summer of 1935 work was started on the first unit of a new reverberatory waste-heat boiler plant which ultimately was to furnish steam for a modern high-pressure power pIant. A second reverberatory waste-heat boiler unit

Jan 1, 1944

By Alfred Weiss

Over the past 25 years hard-rock mining companies have developed a number of profitable computer applications which appear applicable to operations in the coal industry. The evolution of these applications are described and the most profitable discussed. The basic nature of these systems is that they must cut across organizational boundaries. While technological advances contributed significantly to the successful implementation of computers within mining, the human aspects related to organization, management and control of systems projects remain as key to future success in coal as they were and still are in hard-rock mining.

Jan 1, 1983

By D. J. McAdam

Results of investigation of corrosion-fatigue of metals at the U. S. Naval Engineering Experiment Station have been presented by the author in four papers.1, 2, 3, 4 In those papers references were given to the work of Haigh in 1917.5 The investigation at Annapolis included a variety of ferrous and non-ferrous alloys. The experiments showed that even slight corrosion simultaneous with fatigue may cause failure at stresses far below the ordinary endurance limit. The experiments also showed that, for most metals, severe stressless corrosion prior to fatigue is much less damaging than even slight corrosion simultaneous with fatigue. The term "corrosion-fatigue" was restricted to mean the simultaneous action of corrosion and fatigue. The combined effect of corrosion followed by fatigue was called "prior-corrosion fatigue." A stress-cycle graph representing corrosion-fatigue is a curve approaching a horizontal asymptote, the ordinate of which may be called a "corrosion-fatigue limit." To avoid confusion in later discussion, the term "endurance limit" will be restricted to mean the fatigue limit obtained by tests in air with specimens as free as possible from stress concentration and from corrosion. The cndursnce limit as thus obtained presumably represents an inherent property of the metal.

Jan 1, 1929

By D. J. McAdam

Results of investigation of corrosion-fatigue of metals at the U. S. Naval Engineering Experiment Station have been presented by the author in four papers.1, 2, 3, 4 In those papers references were given to the work of Haigh in 1917.5 The investigation at Annapolis included a variety of ferrous and non-ferrous alloys. The experiments showed that even slight corrosion simultaneous with fatigue may cause failure at stresses far below the ordinary endurance limit. The experiments also showed that, for most metals, severe stressless corrosion prior to fatigue is much less damaging than even slight corrosion simultaneous with fatigue. The term "corrosion-fatigue" was restricted to mean the simultaneous action of corrosion and fatigue. The combined effect of corrosion followed by fatigue was called "prior-corrosion fatigue." A stress-cycle graph representing corrosion-fatigue is a curve approaching a horizontal asymptote, the ordinate of which may be called a "corrosion-fatigue limit." To avoid confusion in later discussion, the term "endurance limit" will be restricted to mean the fatigue limit obtained by tests in air with specimens as free as possible from stress concentration and from corrosion. The cndursnce limit as thus obtained presumably represents an inherent property of the metal.

Jan 1, 1929

By R. K. Dann, L. W. Roberts, R. B. Benson

The mechanical properties of 300-series stainless steels were investigated in both high-pressure hydrogen and helium environments at ambient temperatures. An auslenitic steel which is unstable with respect to formation of strain-induced a (bee) and € (hcp) mar-tensile is embrittled when plastically strained in a hydrogen environment. A stable austenitic steel is not embriltled when tested under the same conditions. The presence of hydrogen causes embrittlement at the mar-lensitic structure and a definite change in the general fracture mode from a ductile to a quasicleavage type. The embrittled martensitic facets are surrounded by a more ductile type fracture which suggests that the presence of hydrogen initiates microcracks at the martensitic structure. If a steel is unstable with respecl to fortnation of strain induced martensile, plastic deformation in a hydrogen environment will produce rapid embrittlement of a notched specimen in comparison to an unnotched one. FERRITIC and martensitic steels can be embrittled by hydrogen that has been introduced into the alloys, either by thermal or cathodic charging prior to testing.1-5 However, conflicting reports exist as to whether austenitic steels that are stable or unstable with respect to formation of strain-induced martensite can be embrittled by hydrogen.8-12 A recent investigation has shown that cathodically-charged thin foils of a stable austenitic steel can be embrittled.13 An earlier investigation of a thermally charged 18-10 stainless steel revealed a significant decrease in the ductility only at the lowest test temperature of -78°C, although strain-induced bee martensite was shown to be present in one specimen tested at ambient temperatures.' When martensitic steels are tested in a hydrogen atmosphere, they are embrittled.'4-'7 It has been observed in this Laboratory that 304L steel, which is unstable with respect to formation of strain induced martensite, forms surface cracks when plastically strained in a high-pressure hydrogen environment. Work in progress elsewhere concurrent with this investigation has also established that 304L is embrittled when tested in a high-pressure hydrogen atmosphere." The objective of this investigation was to study the effect of a high-pressure hydrogen environment on the tensile properties of a stainless steel that contained strain-induced martensite (304L) and one that did not (310). EXPERIMENTAL TECHNIQUES Notched and unnotched cylindrical specimens were machined from 304L* and 310 rods that were heat- treated at 1000°C in argon for 1 hr followed by a water quench. The chemical analyses of these steels are given in Table I. The unnotched specimens had a reduced section diameter of 0.184 & 0.001 in., a gage length of 0.7 in., and were threaded with a 0.5-in.-diam. thread on each end. The notched specimens had a reduced section diameter of 0.260 * 0.001 in. and a 0.75-in. gage length, with a 30 pct 60 deg v-notch at the center. The notch had a maximum root radius of 0.002 in. The tensile bars were fractured in a hydrogen or helium atmosphere of 104 psi at ambient temperatures. The system used for mechanically testing the specimens is to be described in detail elsewhere.19 Several specimens of each type were tested in air using an Instron testing machine. The same yield strength and ultimate tensile strength were obtained in 104 psi helium with the above system as with the conventional testing machine. Magnetic analysis was employed to determine that there was a (bee) martensite in plastically deformed 304L and that it was not present in plastically deformed 310. The magnetic technique depended on allowing the material being studied to serve as the core between a primary and secondary coil. Thus, any change in the amount of magnetic material present between the annealed and plastically deformed steels will be indicated by corresponding changes in the induced voltage in the secondary circuit." The ratio of the output signal of a nonmagnetic stainless steel to a completely magnetic maraging steel was 2000 to I. Several unnotched 304L bars tested in hydrogen were analyzed for hydrogen by vacuum fusion analysis. There was an increase in the hydrogen content to approximately 2 ppm for the specimens tested in hydrogen, as compared to less than 1 ppm for the as-received material. Several thin sections cut from notched areas of 304L specimens tested in hydrogen and containing the fracture surface contained approximately 1.5 ppm H. The accuracy of these determinations was estimated to be ± 50 pct.

Jan 1, 1969

By Henry M. Howe

This paper may be regarded as a report of progress of an investigation into the influence of prior exposure to different high temperatures, under different conditions, on the properties of steel after it has been cooled completely. The following are the chief divisions: II.—Experiments on toughening manganese-steel by sudden cooling. III.—A study of the critical points of common or carbon-steel, chiefly by examining the spontaneous retardations which occur in heating and cooling it, and by examining the ductility of pieces of steel which have been cooled suddenly from different temperatures by quenching them in water or brine. IV.—A brief note on Osmond's theory. V.—A study of the critical points by examining the ductility of pieces of steel which have been cooled slowly from different temperatures at, above, and below them. VI.—A description of the furnace used, with notes on thermoelectric pyrometry. It remains to throw further light on the questions studied by ascertaining the condition of the carbon and the hardness proper, and by studying the microstructure and the fracture of the many pieces treated. I hope to present later the results of experiments in some of these directions. With few exceptions, the experiments have been performed in my private laboratory. I tender sincere thanks to my assistant, Mr. William Haskins, S.B., on whom most of the labor has fallen, for his zealous and intelligent co-operation; to the Sterling Steel Co. for their extra hard steel, Series 17; and to Mr. Joseph Hartshorne and the Pottstown Iron Co. for their soft basic steel. Series 8, 9,10, and 18 were supplied by Messrs. Spaulding, Jennings & Co., of the West Bergen Steel Works; to them also my thanks are due. The temperature of the pieces treated has been very carefully

Jan 1, 1894

By A. R. Elsea, C. C. McBride

HIGH-TEMPERATURE alloys, that is, alloys that are strong at high temperatures, have become increasingly important with the development of modern aircraft engines. Many alloys of this type are available. However, metallurgists do not have a clear understanding of the phases or structures which are responsible for these high-temperature properties. If these basic factors were understood, it might be possible to make better or cheaper alloys for service at high temperatures. For this reason, an investigation of the fundamental factors promoting high-temperature strength in alloys was started at Battelle Memorial Institute. This was to have included a study of the relationship between the structure and properties of cobalt-chromium base alloys of the vitallium type. It soon became clear that the structure of vitallium is quite complex and that the equilibrium diagrams which should explain these structures were unreliable. As a result, the cobalt-chromium binary diagram was determined as the first phase of this investigation1. This diagram is shown in fig. 1. During the study of the cobalt-chromium binary system, it was learned that these alloys may pick up considerable nitrogen when melted and heat treated in air. The extent to which nitrogen affects the various reactions in cobalt-chromium base alloys was not known, but there were indications that this impurity might be responsible for some of the erratic test results obtained for vitallium. Consequently, nitrogen was the first ternary addition studied. Thereafter the work was extended to ternary additions of iron and of nickel. This paper describes the investigation of the effects of nitrogen, iron, and nickel upon the reactions in cobalt-chromium alloys with 80:20 and 68:32 cobalt-chromium ratios. Experimental Work Alloy Preparation: A series of cobalt-chromium base alloys containing various amounts of the third element being studied were made for both the 80:20 and the 68:32 cobalt-chromium ratios. Electrolytic chromium, cobalt, and iron, and reagent-grade nickel powder were used as melting stock. Table I contains the chemical analyses of these materials. The charges were melted in alun-dum thimble crucibles which absorbed chromium oxide and effectively deoxidized the melts. These crucibles were supported by close-fitting graphite sleeves so that if they cracked during melting the metal would not be lost. Carbon increases, during

Jan 1, 1951

By J. R. Spencer

When supplies of high pressure mercury or other liquids are required in analytical work, it is convenient to have the source of supply at a relatively constant pressure and available in sufficient volume to satisfy the requirements of the apparatus in use. It is also desirable that the pressuring device be as simple and as inexpensive as possible and convenient to operate. This pump combined with a small storage reservoir containing gas under pressure has the attributes of (1) positive control of the maximum output pressure through the use of a regulator in the low pressure air supply; (2) an increasing capacity as the rate of withdrawal of mercury from the pressured system is increased; and (3) simplicity, requiring only the use of a lathe, drill press, and welding unit in its construction. DESCRIPTION Essential parts of the pump are shown in Fig. 1. In appearance the unlt is similar to the usual steam pump in common use in industrial applications although considerably smaller in size. The main differences lie in the area ratio of the air and mercury pistons and in the design of the air valve mechanism. Approximate diameters of these pistons are 4.25 in. to 0.375 in. respectively, giving an area ratio of about 130 to 1. The air piston (2) is attached to the end of shaft (4), with the mercury piston being merely a reduced extension of the shaft. Mercury intake and discharge to the pump are controlled by high pressure check valves that screw into the ports indicated at (6). Air supply is controlled by the valve assembly mounted on top of the

Jan 1, 1950

By Robert E. Brand, Strathmore R. B. Cooke

For a study of the bonding that occurs in magnetite pellets during oxidation, cubes of magnetite, hematite, and quartz were prepared, each with one surface polished and nearly optically plane. These faces were fired together under pressure and at various temperatures to determine whether bonding would occur. Sections of surfaces that bonded were examined microscopically. An attempt was made to measure the strength effected by this treatment. EARLIER work1,2 has shown that the strength developed by fired magnetite pellets containing silica or silicates is due to three separate effects. Two of these are associated with the formation of slag in the interior of each pellet at temperatures above 1000°C, where the atmosphere is substantially though temporarily neutral. The third is independent of the silica content and is responsible for the development of a hard shell around the pellet during the initial stages of firing, a condition which permits the pellet to assume the increasing load of the overlying burden and prevents extrusion of the slagged and semi-liquid interior. Pellets made from hematite concentrates do not show these effects unless specific additives are incorporated, and it is these differences in behavior which in large part account for the difficulty in producing satisfactory pellets from such concentrates. Elsewhere it has been stated that "the most important factor responsible for the development of strength in fired magnetite pellets containing no additive is the oxidation of magnetite to hematite and the subsequent recrystallization and grain growth of this constituent."' The object of the investigation reported in the present paper was to study in detail the mechanism described above and to evaluate its contribution to the strength of the fired pellet compared with other possible mechanisms, excluding slag bonding. This was effected by placing together polished faces of two cubes prepared from specific minerals and then heating them under constant pressure at different temperatures both in air and in nitrogen. The materials used were magnetite, hematite, and quartz. The magnetite was coarsely crystalline material from western Montana, the hematite was Itabira ore from Brazil, and the quartz was of optical grade but of unknown origin. A high-grade Lebanon (Pennsylvania) magnetite concentrate was used to prepare briquets for the investigation of bonding strength. Analyses of the iron oxide materials are given in Table I. The specimens for furnace treatment were prepared with a carborundum cut-off wheel, which cut the minerals into cubes approximating % in. along each edge. Care was taken to make the sides as parallel as possible. The edges of the faces to be polished were beveled, and the cubes were mounted in brass rings with sealing wax, this being essential to prevent the specimens from rocking during polishing. To prevent excessive friction, the wax was recessed so that only the brass ring and the face of each specimen would be in contact with the polishing lap. Each specimen was then ground with No. 600 carborundum to produce a level surface before polishing. The Graton-Vanderwilt process was not used for polishing because of the long time required by this method, but several other methods were tried. Cloth laps using levigated alumina or chromium oxide did not produce the desired polish. Satisfactory results were obtained by means of a pitch lap: which was used for all the mineral cubes, with levigated alumina as the polishing medium. The lap was operated in a machine similar to those used in the preparation of single optical surfaces. It was run at low speeds and moderate pressures, and polishing was stopped occasionally to prevent overheating of the lap. A good polish with flat surfaces could be obtained in about 5 min. After polishing the sealing wax was removed either in hot water or in a solvent such as turpentine.

Jan 1, 1955

By W. C. MENDENHALL

THE problem of maintaining the mining industry is two-fold; finding new supplies in the face of increasing difficulties, and making such advances in the arts of extraction and preparation as to use supplies of lower grade. Progress in mining and reduction methods and in transportation makes ore today of that which was waste yesterday. These are the fields of the metallurgists and the transportation engineers. The geologists and mining engineers must work together on the problem of ore finding. As the old prospector fades from the scene, men with equal hardihood and patience and equal power to meet the physical obstacles which confront the seeker after ore, must take his place, armed with all that has been learned from human experience about the causes, the controlling conditions, the indications, and hiding places of the metals. Such a seeker is dealing with some of the most complex and obscure of natural phenomena. In nature's laboratory, tremendous forces are at work. Tempera-

Jan 1, 1926

By Lewis Reeve

As. part of a program of investigation of the properties of electric arc welds carried out in the laboratories of the A. 0. Smith Corporation, considerable work has been done on the determination of the oxygen, nitrogen and hydrogen content of different types of weld metal, employing for this purpose the so-called "vacuum fusion method." It is the purpose of this paper to describe certain improvements that have been introduced in this method of determining the gas content of metals, with particular references to the steel specimens examined in this investigation. The method and apparatus used at the beginning of the investigation were essentially those of the Bureau of Standards as described by Vacher and Jordan.1 Later a number of changes were introduced which resulted in. more rapid evacuation of the graphite crucibles employed and which enabled larger volumes of gas to be dealt with than could be handled conveniently in the Bureau of Standards equipment. In addition, the analyzing of the gases evolved from a melt in the same apparatus as collected was abandoned in favor of analysis outside the equipment using standard methods of gas analysis. The time required for gas analysis in the apparatus itself, as described by the Bureau of Standards, was found to be considerable, and during this time the rest of the equip-ment was tied up, preventing its use for the analysis of further steel sam-ples. As a result of the modifications introduced, the time required for the analysis of a steel sample for gas content was reduced from about 8 hours to less than 3 hours. Subsequently, the whole procedure of melting the sample and collect-ing the gases evolved was modified so as to enable a distinction to be drawn between the easily reducible oxides such as iron oxide and the more stable oxides such as silica and alumina. At the same time evidence was obtained indicating the probable existence in the steels of other nitrides than those of iron alone and making possible their quantitative determination.

Jan 1, 1933