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By Robert Warner

WHEN a new mine is opened, and often when an operating mine must adapt itself to physical or economic changes, a mining system must be selected in complete detail. In the past the plan chosen was usually the product of the local staff alone, however limited the training and experi-ence of that staff might be, which often resulted in the introduction of methods that were familiar to the staff, but not so well suited to the con-ditions as others unknown to the local men. A new management, noting the difficulties with the existing layout, might make modifications or complete changes, so that many mines in their history have seen a whole series of mining systems, each somewhat laboriously grafted on to its predecessor. This should not be interpreted as a condemnation of the older staffs for sticking to the tried systems, such as open square-sets in the early days at the Homestake, because they knew it would work after a fashion, nor does the statement apply to the technically trained, and usually broadly experienced staffs of most present-day properties. The older miners did not have the variety of tools and methods, nor the present freedom of transfer of information as to what the other man is doing, and so did the best they could under the circumstances. Finally, the higher grade of the ores made the choice less vital. The ever-increasing need to mine low-grade orebodies, with a fixed or even lower price for the metal produced, has caused an increasing need for low-cost mining. In most new mines this has simplified the problem of selection by eliminating from consideration all of the high-cost systems, but it has also complicated the choice by the necessity for refinement in detail and a close adjustment of the plan selected to all the conditions at the property. In these low-cost problems any textbook division of mining systems as applied to "beds, veins or masses" avails little as a guide. It should be realized at the outset that to' be successful under modern competitive conditions a system of mining must be worked out with elaborate detail, with careful time scheduling and control of the various elemental operations, and that after it is introduced it must be run with a large amount of technical direction.

Jan 1, 1933

By V. I. Purcell, R. E. Snow, S. C. Sun

FATTY acids have been used as standard collectors for floating the matrix1-8 but not the leached zone phosphate ores. After a series of investigations, Davenport9 and Tarbutton10 concluded that the Florida leached zone ores tested were unamenable to fatty acid flotation and must be upgraded by floating the siliceous gangue with Armac-T as collector. The cationic flotation was estimated11 to cost almost ten times as much as a fatty acid process that would ideally give the same flotation grades and recoveries of phosphates. Mineralization: Extensive deposits of leached zone aluminiferous phosphate occur in The ore sample used for this work was obtained from the Virginia-Carolina Chemical Corp., Clear Springs area, Florida. The ore is a potential source of uranium and aluminum as well as phosphorus. Since the uranium and the recoverable aluminum are contained in some of the phosphate minerals, an upgrading of phosphate results in a corresponding enrichment of both uranium and aluminum. The phosphate minerals in the ore are primarily pseudo- wavellite, millisite, and carbonate fluorapatite, with a minor amount of wavellite. Quartz and clay are the common gangue minerals, quartz being pre- dominant. Others present in small amounts are ilmenite, hydrated iron oxides, staurolite, monazite, and zircon.

Jan 1, 1957

By R. F. Mehl, W. Batz, C. Wells

Diffusion coefficient values for carbon in austenite covering a wide range of temperature and composition have been determined employing statistical methods. In addition, the relation between concentration and each of the following, D (diffusion coefficient), Q (activation heat of diffusion), and A (the constant in the diffusion equation), has been obtained. A study of the rates of diffusion of austenite was published in Metals Technology in 1940.' The present investigation is an extension of the earlier work, undertaken (1) to obtain values of the coefficient of diffusion, D, over a much wider range of carbon concentration, and (2) to provide data in all ranges of concentration and temperature in such abundance that statistical methods could be employed to evaluate the accuracy of the data with unusual precision. Composition of Materials: Composition of materials used in this research program are listed in table I. These materials, all forged to about 1 1/4 in. rounds, consist of a high-purity iron, Armco iron, a large number of laboratory-made plain carbon steels containing amounts of impurities normally expected in high-quality commercial steels, and three silicon steels. Since it was known at the time these steels were being made that impurities in the amounts present were unlikely to affect carbon diffusion rates' significantly, the effort made to obtain high-purity steels was not as persistent as it otherwise would have been. Procedure: In general, the procedure followed by Wells and Mehl and described' in detail in an earlier publication' is the one used by the present authors. However, certain modifications have been made which it is believed allow diffusion data to be interpreted more objectively and correctly. These are described completely under appropriate subheadings which follow. Experimental Procedure: Experimental procedure includes (1) the preparation of specimens by welding steels of different carbon contents, (2) the heating of these for certain times at selected temperatures in order to diffuse carbon along the specimens across the welded "interface," and (3) the determination of the carbon distribution across the diffusion zone. Preparation of Specimens: Prior to welding steel of one carbon content to iron or steel of another carbon content, surfaces to be welded are machined perpendicular to the longitudinal axis of cylinders which are about 3/4 in. in diam and 1 1/2 in. long. The prepared, flat, parallel surfaces are brought together and butt-welded electrically. Evidence of a good weld is given in fig. 1. Welding temperature

Jan 1, 1951

By Bruce A. Kennedy

SME hopes to publish its first separate volume of Mining Exploration Transactions later this year. The reason for this separate publication was stated in "Rock in the BOX," December 1969 [ ], p. 14, as follows: "Because of the great upsurge in mineral exploration (during) the last few years and the fragmentation and narrow specialization of the earth sciences into a great many fields not directly related to exploration, many explorationists feel that a need for a special journal devoted to mineral exploration now exists." To summarize the history behind this change in publication policy of the Mining and Exploration Division, we go back to 1968 when a small group of M&E Division members advocated the establishment of an entirely separate journal devoted specifically to exploration. S. Parker Gay Jr. was appointed chairman of an ad hoc committee to investigate the feelings of the other Division members toward such a journal. Approximately one thousand questionnaires were sent out and the returns showed an extremely favorable reaction. Gay reported the results of his survey to the M&E Division Executive Committee Meeting in Salt Lake City in September 1969. These results were also published in the December 1969 issue of [ ].

Jan 1, 1970

By J. C. Karcher

GEOPHYSICAL methods have been more extensively applied to prospecting for oil during 1936 than at any previous time. Their use has been extended to include al- most every oil and gas producing area in the United States. More than ten magnetometer parties, more than nine gravimeter parties, more than five electrical surveying crews, more than fifty torsion balance parties, more than two hundred seismic reflection parties, and several refraction parties were- operating in the United States throughout the year. A tendency has been noted to abandon the use of the pendulum for geophysical prospecting in the oil fields and to increase the use of the

Jan 1, 1937

By C. F. Jenkins, G. V. Smith

Serrated plastic flow in stable austenitic alloys based on Fe/Ni has been shown to be related to the presence of carbon and/or chromium in the systems. Strength peaks and plateaus in the serrated-flow temperature region for a commercial alloy correlate with an increased dislocation content, arising, presumably, from enhanced multiplication as a result of a strong interaction between dislocations and solute atoms. The data generally support a mechanism controlled by migration of vacancies, with the energy for vacancy motion being modified by the presence of chromium. Chromium atom -dislocation interaction is responsible for effects above 500°C, whereas the defect interacting with dislocations between 200" and 500°C is suggested to be a carbon-vacancy Pair. ThE phenomenon of jerky flow, serrated flow, or the Portevin-le Chatelier (P-C) effect in austenitic stainless steels is usually attributed to substitutional at1,2 mospheres1,2 or to precipitates&apos;-4 which form at dislocations during plastic deformation. On the other hand, evidence exists which supports a direct inter-stitial-dislocation interaction mechanism for serrated flow in fcc Ni-C,5,6 Ni-H7-9 and in nickel-austenites containing carbon." The present work consists in a study of serrated plastic flow in stable austenitic al-loys. The effects of carbon and of chromium were investigated separately, and a commercial stainless steel with different levels of interstitial impurity concentration was studied in an attempt to delineate the combined effects of the alloying elements. EXPERIMENTAL TECHNIQUES a) Materials and Fabrication. A commercial AISI 330 stainless steel and several specially prepared aus-tenitic alloys have been studied. The experimental alloys were prepared by arc melting the constituents under purified argon. Analyses of the materials are given in Table I. The commercial alloy was obtained as 5/8 in. bar stock and rolled to 0.092 in. sq, with several intermediate anneals. At this stage some of the material was annealed in Pd-purified hydrogen at 1100°C to establish different levels of interstitial content. All other heat treatments were in vacuum (10-5 torr). The "pure" alloy ingots were swaged to 0.120-in. rod and annealed in Pd-purified hydrogen at 1100°C. The analyses for these conditions are also contained in Table I. Following the above treatment, the final wire sizes Table I. Chemical Analyses of Test Materials Hrin Hydrogen at Cr, Ni, Alloy 1lOO°C wt pct wt pct C, ppm* N, ppm* Type 330 As-received 14.78 33.25 430 300 Type 330 64 14.78 33.25 40 50 Type 330 200 14.78 33.25 27 21 Fe/35 Ni 72 - 35.10 <10 62 Fe/35 Ni 200 35.10 <I0 44 Fe/35 Nil15 Cr 72 14.95 34.94 <I0 61 Fe/35 Ni/15Cr 200 14.95 34.94 <10 45 Fe/35 Ni/C $ 35.OM 380 *Sensitivity: N t 5 ppm Ct10ppm. f Nominal Ni content. % A master NiC alloy was used in preparation of this material; courtesy of D.E. Sonon. were obtained by either swaging or cold drawing. The test results did not vary with these techniques. b) Specimen Preparation. Two sizes of specimen and two gripping systems were used. i) 0.070-in. wire with a chemically milled gage section: 0.75 in. long, 0.060 in. in diam. These were fastened into grips containing tapped grooves. ii) 0.050 in. wire, gage length 1.5 in. Ball bearings were welded to the ends of the wires and the gage length was taken to include all material between the welds. Socket-type grips were used with these specimens. With specimens of type ii), joining was performed in a specially constructed brass jig, under argon, and automatic timing was utilized in the procedure. No adverse effects of welding were noted. Specimens were encapsulated and solution treated for 1 hr at temperatures selected to produce the same average grain size, -50 µ. Annealing twin boundaries as well as normal crystal boundaries were counted. The temperatures used are listed in Table 11. Table 11. Specimen Size. Temperature of Heat Treatment and Resulting Grain Diameters for Test Materials Recrystallization Resulting Material Condition Temperature Grain Sue AISI 330 Not H purified 0.070 120O°C 45 to 55µ in, wire AlSl 330 H , pure, 0.070 in. 1150°C 45to55µ wire Fc/35Nil15Cr Pure, 0.070 in. wire 1000°C 45tossp Fe/Ni Pure. 0.070 in. wire 775°C 45 to 55µ Fe/Ni/C Pure, 0.050 in. wire 850°C 10 to 20p AlSl 330 Not purified, 0.050 1150CC 45to55p in. wire AlSl 330 ti, pure, 0.050 in. 1150°C 45to55p wire

Jan 1, 1970

By J. Parke Channing

IT, HAS been my privilege to be Chairman of Engineering Council for very nearly three years, during which time Mr. A. D. Flinn, the. Secretary, and myself, have seen the organization develop until it is functioning smoothly and accomplishing what it can with the money at its disposal. The earliest attempt at what may be called an Engi¬neering Council, of which. I have any knowledge, was made six or seven years ago when the four Founder Societies each appointed two men, who occasionally met to discuss matters submitted to them which were of importance to, the, profession as a whole. I was one of the representatives of the American Institute of Mining Engineers.

Jan 1, 1920

By R. L. Templin

In treating a cast metal by any working process such as rolling, drawing or forging, variations in the conditions present in the remelting, casting, chilling and preheating of the initial ingot will certainly have some effect on the physical properties of the final product. In considering the effects of cold working on the physical properties of metals, however, it will be assumed that these factors, being controlled according to best practice, will remain constant and therefore may be neglected. Starting with such a uniform metal ingot, the next operation in the production of wrought metal involves hot working by rolling, forging or extrusion so as to produce a slab, billet or bloom. This working must be sufficient to produce substantial grain refinement and minimize any defects occurring in the initial ingot. Even such a hot-worked product is not suitable as a starting material for determining the effects of cold working because it contains internal strains analogous to those resulting from cold working. It is necessary, therefore, to supplement the hot working with a considerable amount of cold working, followed by a proper annealing in order to obtain a material suitable for use in defining the effects of cold working on the physical properties of a metal. That is, if the effects of cold working are to be evaluated accurately it is necessary to have other effects at least constant if not absent. Such material, unfortunately, cannot always be obtained in commercial practice but the requirements just indicated certainly represent the desired goal; this goal has been attained in the treatment of some metals, one being aluminum. Factors That Must Be Considered Simultaneously with Cold Working So many other factors affect the physical properties of a metal that it is necessary to consider these factors simultaneously with cold working; their effects vary in magnitude with the amount of cold work present. The most important of these factors are: (I) chemical composition, (2) structure, (3) temperature of working, (4) character of working, (5) rate of working, and (6) methods used for measuring results. For

Jan 1, 1930

By Henry A. Stiff, Lawrence E. Davis

A graphic method was developed which can be used to predict the tendency of oil field waters to precipitate calcium Sulfate under a variety of conditions. Application of this method is made to the prediction of sulfate scale formation in heater treaters. boilers. oil wells. cooling systems and water injection wells. INTRODUCTION A solution may be said to be in equilibrium with respect to a given salt when the concentration of that silt in equal to its solubility. If for any reason the concentration of the salt is increased or its solubility decreased. the equilibrium is upset and precipitation of the salt takes place. Thus, if the concentration of a salt in a particular solution is known and its solubility can be calculated for a given set of conditions, the tendency of this salt to form a precipitate under these conditions can be predicted. Based on these principles a method has been developed for determining the tendency of oil field waters to form calcium Sulfate precipitates under various conditions. THE SOLUBILITY DIAGRAM Calcium sulfate precipitation most frequently occurs when two waters are mixed: one containing calcium ions. and the other sulfate ions. As one of these waters is added to the other a point may be reached where the concentration of calcium Sulfate is greater than its solubility. thus causing the formation of a precipitate. The solubility diagram is a graphic device for determining the location of such points, thereby making possible a prediction of the tendency of such a system to deposit sulfate scale. A similar diagram can be used to solve many other problems involving the precipitation of calcium sulfate. Fig. 1 shows a solubility diagram representing the mixing of two waters. Water "A" contains a high concentration of odium, magnesium, and sulfate ions together with a small amount of calcium. Water "B" contains a high concentration of calcium ions together with sodium, magnesium and a small amount of sulfate ions. The percentage mixture of these waters is plotted along the abscissa of a system of rectangular coordi-

Jan 1, 1952

By W. H. Chang

The phase identification results on several Mg-base alloys are presented. These results have been correlated with strength data and microstructural studies to indicate that carbide dispersion may contribute significantly to raising the recrystallization temperature and strength of Mo alloys. Evidence is presented to show that the degree of carbide dispersion, and hence the extent of strengthening, is governed by the "metal/carbon" ratio which, in turn, depends on both the carbon content and the presence of stable -carbide-forming alloying elements. IN recent years, Mo-base alloys containing small additions of C, Ti, and/or Zr have been developed, which exhibit much higher recrystallization temperature and strength than those of unalloyed Mo. The superiority of these alloys undoubtedly results from simultaneous operation of more than one strengthening mechanism. In the present paper, the strengthening effect of carbide dispersion will be discussed. Although the role of carbide dispersion is being increasingly recognized, the nature of the carbides has, to the author&apos;s knowledge, not been well es- tablished. In Table I are presented some of the phase identification results on representative Mo alloys. These results have been obtained by X-ray diffraction of residues electrolytically extracted from an ethyl alcohol solution containing 7 pct HC1.

Jan 1, 1961

By T. C. Rao

Oil agglomeration experiments were carried out on coal fines to study the effect of process variables such as pulp density, bridging oil dosage and intensity of agitation on (i) size distribution and (ii) yield of agglomerated product. It has been observed that the growth of agglomerates follows a self-preserving behaviour and using this, a characteristic curve has been derived. This curve has been found to be independent of the process variables. It has also been noted that the growth of agglomerates follows second order kinetics. In an attempt to model the process for predicting the size distribution and yield of agglomerates at different levels of the variables, the cumulative 50 percent of the agglomerates passing size (d50) has been correlated with the variables (i) through the kinetic equation and (ii) directly. These equations, coupled with the characteristic curve can predict the size distribution of the agglomerates at any levels of the variables tested. The yield of agglomerates has been found to follow a definite relationship with d50.

Jan 1, 1984

By S. R. Zimmerley, John Gross

The deductions drawn in crushing and grinding operations have heretofore been based on a separation of the products into various sizes. A crushed product may be sized by sieving, by elutriation and by aid of the microscope. To estimate the surface of each size the relation of the surface to the estimated average diameter must be assumed. Such a relation, owing to the irregularity of the particles, may involve two assumptions: First, a factor to convert average diameter to surface for one particular size; and second, a variation in the factor as the diameter of the particle changes. Obviously a surface measurement in which such assumptions and estimates are involved is questionable. In the first paper of this series1 a method has been given by which an accurate measure of surface of quartz can be obtained from its dissolution rate. By the use of this method, surface measurements have been made on a series of sieve sizes of crushed quartz, the results of which are given and discussed in this paper. Prepaeation of the Quartz Sizes The quartz, consisting of large uniform pieces with a density of 2.65 and a purity of 99.5 per cent. SiO2, was crushed to pass 20 mesh and was then sieved. Tyler standard sieves were used, the sieving being done by hand according to the proposed standard method submitted by the senior author to the Milling Committee of the A. I. M. E. A wet split of the sample was made on a 270-mesh sieve. This was followed by dry sieving until less than 0.05 per cent. of the weight of the sample passed through the sieve in 1-min. sieving. The +28-mesh material was discarded because that size did not contain the difficult grains from the 20-mesh sieve.

Jan 1, 1930

By James K. Stanley

IRON-COBALT alloys in the range of 35-50 pct cobalt are of interest in the electrical industry because they possess the highest magnetic saturation of any magnetic material known.1,2 The magnetic saturation induction of the 35 pct alloy is 24,200 gausses, compared to 21,600 for pure iron (Fig I). This difference is significant in electrical apparatus, where weight or space is at a premium. Saturation values higher than that for iron can be attained up to about 70 pct Co but economics restrict the use to as low a cobalt content as possible without sacrifice of saturation. Fig 2 shows the iron-cobalt equilibrium diagram. Up to the present time, two factors have retarded the use of iron-cobalt alloys in the electrical industry for magnetic purposes.† One is the high cost of cobalt ($1.50 per pound) and the other is the inherent brittleness of the binary iron-cobalt alloys. Straight iron-cobalt alloys up to 25 pct cobalt are ductile and easy to process to thin sheet or strip by conventional methods of hot and cold rolling, but the alloys containing higher percentages of cobalt, including those for which the saturation magnetization is a maximum (35 to 40 pct), are increasingly brittle with increasing cobalt, at least up to 50 pct, and are consequently difficult to process, either hot or cold. Work by White and Wah13 indicated that iron-cobalt alloys could be made ductile by alloying with vanadium, and after quenching the alloys (vanadium up to about 4 pct) were found to be cold rollable to very thin gauges. With this as a background, we resumed our work on these alloys with the objective of developing methods for economical commercial production of wide strip. For this purpose we have concentrated on the 35 pct alloy in order to obtain the highest possible saturation value. Experiments were carried out on many alloy additions to the iron-cobalt alloys and on the response of these compositions to heat treatments. This work finally culminated in a commercially producible iron-cobalt alloy which has been named Hiperco. * MATERIALS STUDIED AND PROCEDURE Binary alloys of iron and cobalt in the range of 35 pct cobalt are difficult to hot work (by forging or rolling) without such additions as C, Mn, Si, V, Cr, Mo, W or perhaps others. Another beneficial effect of such additions is that they in-crease to a greater or less extent the strangely low electrical resistivity of these alloys (about 10 microohms per cm3

Jan 1, 1947

By B. Silliman

THE remarkable outflow of natural gas recently developed in Western Pennsylvania, and along the valley of the Ohio and its tributaries, has called attention to an important series of patents for improvements in glass-fnrnaces and the manufacture of glass, which the brothers Siemens have made since 1872. The basement-patent of this series, is No. 127,806 of the U. S. Patent office, and is of date June 11th, 1872. This has been followed by eleven other patents (including one re-issue), all for improvements in glass-furnaces, or methods of manufacture, of which the latest is of date July 11th, 1882. Nine of these patents were issued in 1880-82. The following is the list of these patents, in order of dates, viz.: 1872. June 11th. No. 127,806 (U. S. office), Improvement in glass-furnaces; 17 sheets drawings, 5 pages text. This is the basement-patent. 1877. April 17th. No. 139,800. Improvement in the manufacture of glass; 3 sheets drawings, 2 pages text. Boats and floating vessels swimming in the liquid glass of the tank-furnace. Re-issued in 1880. q. v. 1880. April 27th. No. 226,931. Furnace for annealing and tem pering glass. " July 13th. No. 220,846. Glass-melting-furnace. " August 3d. No. 230,668. Glass-melting-furnace; 4 sheets drawings, 2 pages text.

Jan 1, 1885

By H. A. Guess

INTRODUCTION. HISTORY AND PRODUCTION STATEMENTS. SOUTHEAST Missouri is the oldest of the large producing districts of the United States. The first recorded production from disseminated ores was in 1869, although for many years prior to that time lead had been mined from shallow pockets, and steady growth in production has been shown ever since, the greatest increases being during the past five years. The production by years for each of the operating companies from 1869 to 1907, inclusive, is given in Table I. In Table II. is given the production by years from 1908 to 1912, inclusive, for the district as a whole, showing the tonnage of crude ore mined, yield in concentrates, average assay of concentrates; yield in metallic lead both per ton of crude ore and in total; also approximate value of the yearly production.

Jan 12, 1913

Henry D. Hibbard, High Bridge, N. J. (Communication to the Secretary): There is one chemical factor which has not been considered in the author&apos;s tabulation of tests, but which is none the . less important because it cannot be practically estimated, and that is the element oxygen. This element has been, and probably will continue for some time to be, one of the great causes of the continual discrepancies between the chemical and physical properties of steel. Probably oxygen occurs, in important proportions, only in soft steel, such as that which we are now considering. In this steel its physical effect is to diminish tensile strength and elongation. The percentage of oxygen in the steel, under working-conditions that are as uniform as possible, is likely to vary inversely as that of the manganese, or perhaps, and more probably, it may bear even an inverse geometrical ratio to the manganese-content. At all events, to follow the author&apos;s plan, the line representing the loss of strength due to oxygen is probably a curve. Plotted by itself, the line would probably be straight; that is, the decrease in strength would be proportional to the increase in oxygen, but if the results were superposed on the percentages of manganese, they would give a curve, because the percentages of oxygen increase faster than those of manganese decrease. Were the oxygen-line to be developed and added to the diagram, it would seem that the manganese-line should then be straight. Due allowance for the effect of oxygen, therefore, would modify two features of the paper. It would increase the figure for the strength of pure iron from 38,000 to about 45;000 pounds per square inch, and it would straighten out the manganese-curve. The manganese-line in the paper is curved between 0.50 and 0.20 per cent. Above 0.50 per cent. it is straight, which may be ascribed

Jan 1, 1893

By L. D. Jaffe, D. C. Buffum, F. L. Carr, M. Goldman

IN an earlier investigation by Jaffe and Buffum,&apos; a time-temperature transformation diagram for isothermal temper embrittlement of an SAE 3140 steel showed some suggestion of two overlapping "noses." These authors mentioned, as a possible explanation, that their specimens embrittled at 525°C were slightly softer than expected, perhaps because of some slight unknown variation in tempering treatment. Because a double nose would be of considerable importance in elucidating the mechanism of the temper brittleness reaction,&apos; it appeared worthwhile to redetermine the portion of the diagram near 525°C. The same heat of SAE 3140 steel was used as in the previous work, and experimental procedures were the same.&apos; Blanks were austenitized 1 hr at 900°C, water-quenched, tempered 1 hr at 675°C, and water-quenched. Groups were then embrittled isothermally at the temperatures and for the times shown in Table I, and water-quenched. For comparison, one series was tempered various times at 675°C, water-quenched, and given no further treatment. V-notched Charpy impact specimens machined from the blanks were tested over a range of temperatures. Energy absorption and percentage of fibrous fracture were plotted vs test temperature for each group, utilizing both the new data and those for the same treatment obtained in the earlier work,&apos; except that the earlier data at 525°C were discarded.* are given in Table I. After a small correction (-0.28°C/BHN) for the variation of hardness" from Rockwell C24, the transition temperatures were plotted against embrittling time for each embrittling temperature, using the data of Table I for the range of treatments covered there, and using previous dataL for other treatments. By cross-plotting, Fig. 1 was finally obtained. It appears from this figure that if there are two noses to the time-temperature-transformation diagram for isothermal temper embrittlement of SAE 3140 steel, the upper nose must lie above 575°C. As interest had been primarily in the region near 525°C, a thorough study of embrittlement above 575°C was not made. Fig. 1 shows that such a study is needed, especially since preliminary measurements at the tempering temperature of 675°C reveal much more rapid embrittlement than would be expected from the data at lower temperatures. The transition temperature increased, approximately, as the logarithm of the tempering time (about 81/2°C, after correction for hardness, for each doubling of the time).& Since three tensile specimens tempered 240 hr at 675°C and water-quenched had an average yield-tensile ratio of 0.844, with 70.7 pct reduction of area, it is assumed1 that the tempering temperature is not above Ae1. The omission of a quench-and-reheat operation below Ae1, for the groups tempered at 675°C, as compared to groups embrittled at lower temperatures, should not affect results." More detailed investigation of embrittlement above 575°C is now under way.

Jan 1, 1954

By N. K. Chen, R. Maddin

Single crystals of molybdenum were extended at temperatures from 1300° to 2500°C. It was found that with increasing temperatures, the yield becomes more pronounced and the number of slip bands for equal amounts of elongation decreases. Slip at high temperatures fragments the structure. OTHER than the investigations on sodium and potassium by Andrade and Tsien,&apos; the researches of Steijn and Brick&apos; on a iron single crystals at low temperatures are about the only studies of the influence of temperature on glide of body-centered cubic single crystals. The effect of test temperature on glide has been rather widely investigated with hexagonal crystals" and less widely with face-centered cubic crystals. ~~ a result of these studies it can be said that, in general, the onset of plastic flow as measured by the initial rate of strain hardening becomes more abrupt with increasing temperature, and the value of the yield decreases with increasing temperature. Strain hardening, however, is markedly affected by changes in temperature except at very low and very high temperatures where the strain hardening rate becames constant. In the present investigation it is shown that temperature affects the glide of molybdenum single crystals in much the same manner as crystals of other classes, it., for comparable strains the number of slip bands decreases with increasing temperature; shear along the slip bands increases with increasing temperature; the yield becomes more pronounced with increasing temperature of test; and the strain hardening approaches a constant at very high temperatures. In addition, it is shown that, in agreement with the work of Tsien and Chow, Qlip occurs on (110) planes in <Ill> directions. It is further shown that slip at high temperatures fragments the structure into either irregular sized cells or bent atomic planes which are roughly aligned in crystallographic directions. Experimental Procedure Single crystals 3 mm in diameter by about 25 mm long were prepared using the technique previously described.&apos; The furnace in which the crystals were grown served as the extension apparatus for the tension tests. It consisted of a 4 in. water-cooled brass tube 20 in. long which was continuously evacuated at the bottom. Two water-cooled copper electrodes held the specimen by means of spherical collets secured in place in the electrodes by set screws. These electrodes served also to transmit power and stress to the specimen. The lower electrode was clamped to a stand, while the upper electrode was fastened to one side of a lever arm flexibly supported at the top through a slightly offset pinion. A metal bellows operating elastically was attached to the upper electrode to affect a vacuum seal and allow freedom of motion. The level of the arm was adjusted by rotating a graduated nut. Rotation of the electrode was prevented by a key fitted into a groove. After the specimen was mounted and the vacuum secured, the lever arm was adjusted so that the bellows was at its relaxed position. This insured that the total weight of the specimen, the upper electrode, and the downpull of the vacuum were balanced by the horizontal beam. Since the specimen was heated by its own resistance, expansion of the specimen proceeded freely by this arrangement. During the time of heating the specimen, the beam was maintained in a horizontal position by turning the nut at the top. By graduating the lever arm and using a known dead weight on the lever arm to supply a tensile stress, the graduated nut could be read to 0.0001 in. extension. Since

Jan 1, 1955

By Richard Ageton

SALT bodies in the form of rolls, horses (sometimes called horsebacks), folds, wants and pinches1 have been encountered while driving entries and mining out rooms during the development of the potash mines in New Mexico. Superficially these sporadic salt occurrences appear to be much alike, but closer examination reveals individual characteristics, and after four years of observation it seems possible to divide them into three general groups that may tentatively be called "depositional," "erosional," and "structural." The data collected are not yet sufficient to permit forecasts of their probable location, so that the annoyance of having to mine salt instead of potash could be avoided or lessened. However, the information so far available appears to throw some light on the occurrence of the sylvinite2 bed now being mined, and it is as a progress report that the writer presents the results of his observations. The mines of the United States Potash Co. and the Potash Company of America are about 20 miles northeast of Carlsbad, in Eddy County, N. M. They are on the southwestern flank of the Permian salt basin, which underlies western Texas, Oklahoma and Kansas, south-central Nebraska, southeastern Colorado and eastern New Mexico. The cuttings from many oil wells and the cores from the potash tests drilled in this basin indicate that this salt series approached its greatest thick-ness (about 4000 ft.) in the southeastern part of New Mexico and the adjoining portions of Texas, and that the most advanced stages of

Jan 1, 1936

By J. R. Vilelia

IN accordance with the custom of this society, we are gathered here, as we have every year since 1924, to honor the memory of the eminent American metallurgist and teacher, Professor Henry Marion Howe. Unlike many of the distinguished metallurgists who have preceded me as a Howe lecturer, I cannot bring to you reminiscences of his personality, for it was not my privilege to be associated with Professor Howe, or to be directly one of his students. Yet, Professor Howe and Professor Albert Sauveur, through the medium of their books, were my first teachers of metallography, as they have been of almost all American metallurgists of my generation. As a teacher, and for many years the acknowledged leader of American metallurgists, he exercised a profound influence in the growth of our science and was held in honor by the men of science of his time. I can speak no words of technical appreciation that will add luster to his fame, for by his prophetic vision, his teachings, and his researches he stands among the immortals in the memory of all metallurgists. In 1926, the third Howe Memorial Lecture was presented by Professor William Campbell&apos; of Columbia University, who entitled it "Twenty-Five Years of Metallography." He took as a starting date for his chronology the turn of the century, which coincided with his arrival from England to work in association with Howe at the Columbia School of Mines. In that informative lecture Professor Campbell enumerated the important advances in metallography achieved during the first quarter of the century, and, it now appears, may have established the custom of reviewing such progress every twenty-five years. The scope of Professor Campbell&apos;s lecture was as broad as his metallurgical knowledge, for it embraced a wide portion of the field of metallography, both ferrous and nonferrous. Twenty-five years later, the Howe Memorial Lecture Committee saw fit to assign to me the honor of writing a lecture that would commemorate the work of Henry Marion Howe and would at the same time constitute the 25th anniversary of the lecture by Professor Campbell. The Committee suggested that this lecture might properly be called "Twenty-Five More Years of Metallography," a suggestion that I have adopted. I must confess, however, that I have not followed the precedent established by Campbell and have narrowed the scope of this lecture to an appraisal of those achievements which in my opinion have contributed most to the progress of microscopical metallography during the past twenty-five years. Progress in Metallography The metallographic methods most widely used today, with the exception of the electron microscope, were firmly established more than twenty-five years ago. In general, our specimens were prepared for microscopic examination in those days in much the same manner as they are today. It is true that new details of technique have been introduced from time to time, and that superior equipment is available today, but on the whole, these improvements have been in the nature of refinements, often a matter of personal preference, and none can be considered essential to the attainment of the ultimate goal of the art and science of metallography, which is to reveal the structure of metallic specimens with unequivocal clarity so that they may be interpreted correctly. Mechanical metallographic polishing, which was the only method available in 1926, is still universally practiced and still consists of abrading the metallic specimen with a series of abrasives of increasing fineness until a specular surface is attained. We have now the alternative method of electropolishing, but it is not widely used because, except in a few special cases, its results are inferior to those of competent mechanical polishing. Likewise, most of the etching reagents preferred today were in common use more than twenty-five years ago and were applied in the same manner as they are today. Valuable improvements have been made in the optical and mechanical performance of metallurgical microscopes, but there was no dearth in those days of excellent instruments equipped with achromatic and apochromatic objectives capable of yielding micrographs comparable in quality with the best that we can make today. In fact, it would be a difficult task for any metallographer today to make optical micrographs at magnifications in excess of 3000 diameters that would surpass those made by Lucas more than twenty-five years ago. One of these is shown in Fig. 1. Yet, it is unquestionable that on the whole, the micrographs appearing in the metallurgical literature today are vastly superior to those

Jan 1, 1952