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By Frank Drake

Manganese-ores are known to exist in the Caucasus in a number of localities, viz., in the government of Kutais, near the village of Chiaturi; in the same goverilment near the Choruk river, southward from Batum; and in the governments of Erivan and Tiflis. In smaller quantities they are found in various other places also. The first-mentioned deposits are by far the most important; the others being not only less extensive, but remote from present means of communication, and, from their character, expensive to work, although in some cases the ore is of a superior quality. All the manganese-ore now known in the market as a Caucasian " ore comes from Chiaturi, no other deposits in the Caucasus having been worked commercially; movements have been made, however, towards the exploitat,ion of some of those on the Choruk river. The Manganese-Ore District of Chiaturi. General Remarks, Statistics, Etc.—No other known deposit of manganese-ore can approach that of Chiaturi in capacity for producing large quantities of high-grade ore at a low cost. The deposit is said to have been discovered in 1848, by the geologist Abich, but the first shipments were not made until 1879, when 871 tons* were produced. Since that time, the production has steadily increased, until now the world relies on this deposit for about one-half its supply of manganese-ore. The industry is also of great importance locally, and aftords a livelihood to a considerable proportion of the population of the district in which the deposit is situated.

Jan 1, 1899

By Frederic Dewey

BONE-ASH cupels have been used from time immemorial to absorb litharge, and accompanying oxides; in assaying. Doubtless, also, from the earliest days cupels have been most unjustly blamed for much poor assaying. It has long been known that the precious metals go with the litharge into the cupel. This occasions a loss of precious metals and reduces the results of the assay. There have been many investigations of cupels and the most diverse views have been expressed, the extremes being the statements of Lodge 1 that every cupel has some effect upon the loss in assaying telluride ores and of the Campredons2 that coarse and fine and hard and soft cupels all give the same loss of silver when cupelling the same weights. The truth lies between these statements and much nearer the latter. In a vast majority of cases the influence of the cupel is not dominant and is outweighed by other conditions, particularly the temperature of the cupelling bead. At the Spokane meeting of the Institute I presented a paper on the Assay and Valuation of Gold Bullion,3 which recorded the results of many hundreds of assays made in the Mint service under everyday commercial conditions, which of necessity differ from scientific conditions. In following this matter up, for the purpose of increasing the accuracy of our commercial methods of bullion assays, the question of the absorption of gold by the cupel was found to be a most important one and was taken up for investigation. In a lesser degree, the silver absorption is important and interesting, but at present it appears to be far more complicated and, while many figures showing silver absorption may be found through this paper, much further investigation is required to put the subject upon a satisfactory basis.

Jan 11, 1917

By B. J. Kochanowsky

To improve blasting methods it is necessary to know how the explosive force acts and how rock resists this force. Because of the tremendous power developed within milliseconds and the great number of other factors directly affecting the technical and economic results, an analysis of the fundamentals of blasting theory is difficult. But since the rules used for layout design and for calculations of size of explosive charges are based on theoretical assumptions, complete knowledge of blasting theory has great practical importance in mining. Analysis of Blasting Theory: It is interesting to note the opinion of blasting experts with respect to contemporary blasting theories. F. Stussi,' Professor of the University of Zurich, stated: "We do not have enough experience yet to change our army engineering regulations in blasting and base it on new fundamentals. It is our duty to collect more practical data and to do more research in blasting to close this gap." K. H. Fraenkel,' editor of the Manual on Rock Blasting published in 1953 in Sweden and written by well-known Swedish, German, Swiss, and French blasting and explosive experts, said: "To the best of our knowledge no suitable formulas for civil blasting work are to be found in the American, French or German literature."

Sep 1, 1955

By Arthur T. Word

STANDING room only seemed to be the order at the annual session and luncheon of the Eastern magnetite committee. Gatehouse check at the former indicated at least 80, with 33 attending the luncheon - all the crowded facilities could handle. Chairman Crockett opened the meeting by calling upon Meredith E. Johnson, who presented his illustrated paper on "Prospecting for Iron Ore in New Jersey in 1943." This "wartime" brief was discussed by Lucien Eaton, P. W. Henry, and Chairman Crockett. H. E. Hawkes, Jr., of the U. S. Geological Survey, then presented his unscheduled paper on the "Magnetite Deposits of the Jersey Highlands." Discussion was by A. W. Pinger and Chairman Crockett. Fred E. Stiefel then described shaft sinking at the Fisher Hill mine of the Republic Steel Corp., giving a detailed description of how modern

Jan 1, 1944

By William G. Brissenden

Gaspe Copper Mines Ltd., a subsidiary of Noranda Mines Ltd., operates a completely integrated copper mining, milling and smelting plant at Murdochville, on the Gaspe Peninsula of Quebec. Operating six days a week, the mine produces 8000 tpd of ore. The mill runs continuously and capacity is rated at 6500 tpd of ore. Treating Gaspe concentrate output plus a certain amount of custom concentrate, the smelter produces between 3700 and 4000 tons of copper anodes per month.

Jan 9, 1959

By Paul A. Bailly

“For innovative leadership in bringing about a quantitative rationality to mineral exploration; for the impact his efforts and wide respect have made on national mineral policy issues; for his effective managerial role in major mineral discoveries; and for his lecture, ‘Managing for Ore Discoveries.’”

Jan 1, 1980

By L. E. Welch, C. W. MacGregor

THE past 20 years has seen a revolutionary change in the testing of materials at elevated temperatures. This has largely been brought about by the practical importance of the creep problem in the design of equipment for operation at high temperatures. The short-time tension test carried out at elevated temperatures has consequently assumed in many cases only a secondary role compared to the long-time creep test. In many problems, however, a knowledge of the short-time high-temperature properties of a metal is essential. To mention a few cases in which this is so, we might include all hot-forming operations such as rolling, forging, etc., the welding problem if residual stresses are to be computed, the development of new alloys for high-temperature service where, in the initial stages, time does not permit of long duration creep tests, and others. Usually a knowledge of the short-time properties is desired, if only to serve as a background against which to compare creep behavior. In conducting short-time high-temperature tests, it has been almost the universal practice to determine stresses based on the original area and strains referred to the original gauge length which is usually chosen as 2 in. It has been pointed out 1,2 that one of the reasons that the true significance of certain tensile properties is not understood, which perhaps curtails their usefulness, especially when the material is applied [ ] under conditions differing considerably from the test conditions, is that true physical stresses and strains are not determined. It is essential to have a knowledge of true stresses and strains in order to correlate the values present in the tension test with those existing, for example, in hot metal-forming operations and in the general problem of the yielding and failure of metals under combined stress conditions. Stress and strain values based on the original dimensions of the test piece do not exist physically except in the early stages of the test. Since at the present time there is very little information in the literature on true stress-strain relations in the short-time high-temperature tension test it is proposed in the following pages to describe a

Jan 1, 1942

By Kenneth K. Humphreys, Joseph W. Leonard, Robert L. Llewellyn, William F. Lawrence

INTRODUCTION Cleaning fine coal sizes utilizing air currents in machines as the primary separating medium is called dry concentration or pneumatic cleaning. In 1947 approximately 18 million tons (16.38 million mt) of bituminous coal were cleaned by air machines; in 1965, 25.4 million tons (23.1 14 million mt); but in 1975, only 7 million tons (6.37 million mt). Table 11-1 shows the tonnages cleaned of bituminous coal and lignite in the United States by various types of equipment from 1938-1963. Table 11-2 shows only tonnages cleaned by pneumatic methods from 1964-1975. The decrease in tonnage to approximately 7 million tons (6.3 million mt) is due to a higher moisture content in the mined coal and the greater difficulty in cleaning the coal by air. There also was a definite trend to load raw coal at the mines, especially the slack which is the most expensive to clean due to the dewatering and drying requirements. While there have not been any applications of pneumatic cleaning in the anthracite field, its use has not been fully explored. The same is true for lignite and subbituminous coals.

Jan 1, 1979

By J. M. Adams

It is my purpose to give some of the results obtained by an experience of nearly seven years in working ores by the method frequently called the Washoe Process, and in several mills of which I have had charge, but principally in the Owyhee Mill, at Silver City, Idaho, which had twenty 650-pound stamps, and sixteen pans. I shall discuss here merely the mechanical details for working ores generally, subdividing the subject as follows : 1. Preparation of the ore for the stamps; 2. The crushing in the battery; 3. The settling of sand or pulp in vats or tanks; 4. The treatment in the pans; 5. The results obtained in settlers, agitators, and concentrators; 6. The straining of quicksilver, cleaning of amalgam, and retorting; 7. The saving of slimes and their subsequent treatment; 8. The loss of quicksilver. For descriptions of the various kinds of orebreakers, stamps, tanks, pans, settlers, etc., I must refer to the various works on these subjects, prominent among which are the reports of the United States Commissioner of Mining Statistics,and the volume on "Mining Industry," the third volume of the United States Geological Survey on the Line of the Fortieth Parallel through the gold and silver bearing regions of the great West, undertaken under the able guidance of Clarence King, assisted by Mr. James D. Hague and others. In this discussion it will be assumed that the general arrangement of the quartz mill is understood; and the question will be treated how to secure, from such a mill, the greatest economy in working, combined with the largest results. This place seems fittest for a single preliminary suggestion—namely, that there should be double "floors" throughout the mill, so that nothing can sift through and be lost.

By Strathmore R. B. Cooke, Iwao Iwasaki, C. S. Chang

The effects of aeration on an aqueous suspension of pyrrhotite were studied and their results correlated with flotation tests using xanthates as collectors. The effects of copper activation and of pH variation were determined and possible mechanisms postulated. PYRRHOTITE has long been considered a gangue mineral to be eliminated as tailing in the treatment of various sulphide ores. However, in recent years the world-wide lack of sulphur resources has called attention to this mineral as a potential source of both sulphur and iron. Its importance as an economic mineral, however, has not been particularly emphasized. For this reason very little is known about its response to flotation, except that it can be depressed easily in alkaline circuit, by long aeration,1,2 addition of oxidizing agents,3 or by starch.' The object of this work was to study the floatabil-ity of pyrrhotite. This includes the effect of oxidation by aeration, of copper activation, and of change in pH. Preparation of the Pyrrhotite Sample: It was desirable that the highest grade of pyrrhotite obtainable be used for this experiment, since the presence of other minerals could affect the surface properties.5 However, no pyrrhotite was available as crystals, and massive deposits of hydrothermal origin commonly contain considerable amounts of chalcopyrite. Pyrrhotite concentrate was, therefore, prepared from a sulphide deposit occurring near Aitkin, Minn. The deposit is of pyrometamorphic nature consistirlg mainly of pyrrhotite and pyrite with graphite, silicates, and carbonates as gangue. The ore, already crushed through 3 mesh when received, was screened at 65 mesh and the undersize discarded. The oversize was crushed through rolls, and then stage-ground dry in an Abbe porcelain mill, the —65 mesh portion being screened out after every 15 min of grinding until all the material passed through this size. The ground product was then concentrated with a drum-type dry magnetic separator. The rougher concentrate was cleaned twice and then demagnetized. The final product was split in a Jones splitter and stored in air-tight bottles. Microscopic examination of the concentrate showed that it was relatively clean and free of pyrite, locked particles, and gangue. By means of the krypton gas adsorption method," the specific surface was determined to be 3000 cm2 per g. The chemical and screen analyses of the final concentrate are given in Tables I and II respectively. It is a well-recognized fact that the oxidation of some sulphide ores during stockpiling, grinding, and conditioning affects their flotation behavior. The problem of oxidation may become serious in the case of pyrrhotite, since this is known to be more easily oxidized than many other sulphides. To ascertain the extent of oxidation, an experiment was carried out by aerating an aqueous suspension of pyrrhotite with air, oxygen, and nitrogen as follows. A 300-g sample of pyrrhotite in 2700 ml of water was agitated and simultaneously aerated in a Fager-gren-type laboratory flotation machine. A Precision wet test meter was connected to the air inlet valve, the flow rate of the gas being kept constant at 0.3 cu ft per min throughout the experiment. Samples of approximately 30 ml each were taken from the cell at 0, 4, 10, 20, 35, 60, and 90 min. After the pH was taken, each sample was filtered and the filtrate was analyzed for total iron and sulphur. The iron was determined colorimetrically by the thioglycolate method using a green filter.' The filtrate was oxidized with bromine to convert all of the soluble sulphur compounds into sulphate and this was determined with a Parr turbidimeter." When aeration tests were made in alkaline circuit, calcium hydroxide or sodium hydroxide was added at regular intervals to maintain a constant pH. A similar procedure was followed in an experiment to determine the abstraction of copper. ion by pyrrhotite. In this case various quantities of cupric chloride were added. The filtrate from each sample taken was analyzed for copper, total iron, and sulphur. The carbamate method with a green filter was used for the copper analysis,' since this method could tolerate a considerable amount of iron in the solution. A pneumatic cell, made from a 350-ml fritted glass Buechner funnel, was used for this experiment. The detail of the assemblage has been described elsewhere." In the present work a stainless steel baffle was inserted in the cell. This baffle overcame the tendency for the coarse pyrrhotite particles to be swirled around the wall of the cell and thus fail to collect in the froth. A 50-g sample of pyrrhotite was added to the cell which contained 260 ml of water. When pretreat-ment of the sample was desired, reagents, such as activator and pH regulator, were then added and the pulp was conditioned for a specified conditioning time. Prior to the addition of the collector approximately 15 ml of the solution were removed for pH measurement and for iron and sulphur analyses. Copper when used as activator was also determined. Collector and frother were then added and the pulp was conditioned for an additional 2 min. Air was admitted to the cell and the froth removed. The separation required from 4 to 6 min, depending on the characteristics of the froth. The float and non-float products were filtered, dried, weighed, and assayed for iron.

Jan 1, 1955

Jan 1, 1894

By P. K. Foster, C. M. Payne, A. McNabb

Some measurements of the rate of loss of hydrogen from cylinders of iron and steel are analyzed in terrns of a trapping theory. The apeement is encozcraging and gives rise to estimates for the density of traps in the metal. Furthermore, the results appear to be consistent with the assumption that the diffusion constant D for the steady flux of hydrogen through iron lies on the extrapolation of the linear curve (log D us 1/T) obtained at higher temperatures. IT has been shown in a previous paper1 that the literature relating to hydrogen diffusion in steels contains sufficient evidence to invalidate the application of Fick's laws to hydrogen diffusion in steel at low temperatures. To account for the deviations from simple diffusion behavior a trapping theory was developed, and the fundamental laws modified accordingly. In the present paper, new data on the evolution of hydrogen from long cylinders are presented, and together with some published data are examined in terms of the requirements of the theory.' Properties of solutions of the basic equations derived previously1 and appropriate to the present experimental conditions are outlined in the first section as they determine the form in which the experimental data must be presented for a comparison of theory and experiment. Two new solutions not previously reported have been derived as described in the Appendix. The experiments and treatment of data are then given in Sections 2 and 3 and the results are discussed in Section 4. 1) THEORETICAL CONSIDERATIONS The hydrogen-diffusion theory1 applied in this paper postulated that lattice-dissolved hydrogen at a concentration C diffuses randomly in accordance with Fick's first law, but that the lattice contains a uniform density N of traps which can capture and delay hydrogen atoms. kC atoms are trapped per second in a region containing unit concentration of vacant traps while p are released per second in a region containing unit concentration of occupied traps. On this basis it was shown (Eq. [30] of Ref. 1) that, when local changes in the lattice-dissolved concentration C are slow enough for equilibrium to be established with the traps, the system is represented in dimensionless form by the equation:

Jan 1, 1965

By J. M. Adams

IT is my purpose to give some of the results obtained by an experience of nearly seven years in working ores by the method frequently called the Washoe Process, and in several mills of which I have had charge, but principally in the Owyhee Mill, at Silver City, Idaho, which had twenty '650-pound stamps, and sixteen pans. I shall discuss here merely the mechanical details for working ores generally, subdividing the subject as follows: 1. Preparation of the ore for the stamps; 2. The crushing in the battery; 3. The settling of sand or pulp in vats or tanks; 4. The treatment in the pans; 5. The results obtained in settlers, agitators, and concentrators ; 6. The straining of quicksilver, cleaning of amalgam, and retorting; 7. The saving of slimes and their subsequent treatment; 8. The loss of quicksilver. For descriptions of the various kinds of orebreakers, stamps, tanks, pans, settlers, etc., I must refer to the various works on these subjects, prominent among which are the reports of the United States Commissioner of Mining Statistics, and the volume on "Mining Industry," the third volume of the United States Geological Survey on the Line of the Fortieth Parallel through the gold and silver bearing regions of the great West, undertaken under the able guidance of Clarence King, assisted by Mr. James D. Hague and others. In this discussion it will be assumed that the general arrangement of the quartz mill is understood; and the question will be treated how to secure, from such a mill, the greatest economy in working, combined with the largest results. This place seems fittest for a single preliminary suggestion-namely, that there should be double "floors" throughout the mill, so that nothing can sift through and be lost.

Jan 1, 1874

By Robert S. Moehlman

Is recent years, exploration and development by diamond drilling has become a popular attack on the problem of finding new ore shoots and developing extensions of known shoots. Diamond drilling has been used in recent years in extensive sampling of disseminated copper deposits, in preference to churn drilling. At the Harvard gold mine, near Jamestown, California, Philip R. Bradley, Jr., general superintendent, reports that: "The Harvard work was a singular example of the reliance that can be placed on diamond drilling in evaluating an ore body." Drilling at the Harvard mine will be discussed in a subsequent section of the paper. So popular has diamond drilling become, indeed, that many who have had slight experience with drilling are inclined to regard it as a cheap cure-all. This paper proposes to show some of the limitations on the application of drilling and some of the steps that should be followed in drilling programs to obtain reliable results. Cost oF Drilling Drilling has the advantage, over shaft sinking and drifting, of lower cost and greater speed. As compared with churn drilling, the advantage of bringing up a coherent sample instead of fine cuttings for a sample is obvious. Diamond drilling is generally more expensive, however, and more engineering effort is required in combining the average of core and sludge samples. Exploration of drift walls by hammer drills to a depth of less than 30 ft. is generally cheaper than diamond drilling, but beyond this depth the diamond drill is cheaper and more efficient. The principal factor in determining cost of drilling is the character of the ground drilled. Broken ground with many fissures is most expensive to drill. Hard ground is less of a problem with diamond drills than with ordinary machine drills. Hardness or softness affects only the speed of drilling. Caving, easily washed, sandy or clayey ground requires continual cementing and casing, which is the greatest cost problem. Thus, soft, incompetent ground is more costly to drill than hard, massive ground. Cost of drilling per foot in good to fair ground varies from less than $I per foot, achieved in some districts in Ontario, the Mother Lode, and Missouri, to $5 per foot in many western states. In bad drilling ground, costs may range from $5 to $15 or more per foot, thus approaching the cost of drifting. Other factors that increase the cost per foot are: I. Short total length of hole drilled, so that the cost of moving in crews and equipment must be spread over a relatively few feet. 2. Cost of drilling per foot increases with depth beyond about 500 ft.. as more time is consumed in pulling rods' 3. Cost of preparing drilling stations, getting air underground to stations? etc' 4. Inaccessibility and lack of water on the job make for higher costs.

Jan 1, 1946

By Hans M. Ewoldsen

The generation and evaluation of solutions to body force problems is of extreme interest to the geotechnical profession, as all natural stress states must necessarily include some contribution from the weight of the material. In this chapter the elastic solution for the stress field around a circular, horizontal tunnel at an arbitrary depth beneath the surface of a half-space is reexamined. The influences of body force, initial stress, and free surface proximity are examined and related to in-situ cases. The solution as presented deals only with an isotropically elastic medium; this medium is further considered only in a half-space configuration. It is readily apparent that these restrictions impose severe limitations if analogies are attempted with in-situ cases where geologic discontinuities, inhomogeneities, and irregular boundaries exist. The question might be raised as to the propriety of geotechnically oriented researchers even considering such idealized conditions. There is, however, much to be gained from study of such solutions. The lack of geologic discontinuities and inhomogeneities allows the investigator to separate and leisurely examine such parameters as are included in the solution, without worry of interrelationships of a host of other parameters. Further, elastic solutions have had extensive usage prior to the development of such techniques as the finite-element solution. It is interesting to compare body force solutions with the external field solutions which in the past have been used for design purposes. Finally, the exact solution may be used to verify the accuracy of the finite-element type of solution. The mathematical solution on which this chapter is based was originally developed by R. D. Mindlin.l Because of the complexity and length of the solution, no attempt was made to determine the resultant stress fields until the advent of the present-day high-speed digital computer. How-

Jan 1, 1972

By K. H. Hiller

A rotational viscometer has been designed which perrnits the measurement of the rheological properties of drilling muds and other non-Newtonian fluids under conditions equivalent to those in a deep borehole (350F, 10,000 psi). The important mechanical features of this instrument are described, and its design criteria are discussed. The flow equations for the novel configuration of the viscometer are derived and the calibration procedures are described. The data and their interpretation, resulting from measurement of the flow properties and static gel strengths of homoionic montmorillonite suspensiom at high temperatures and pressures, are presented. Data are also presented for the flow behavier of typical drilling fluids at high temperatures and pressures. The pressure losses in the drill pipe and the annulus depend critically upon the flow parameters of the drilling fluid. This work demonstrates the need to measure these parameters under bottom-hole conditions in order to obtain a reliable estimate of the pressure losses in the mud system. INTRODUCTION The rheological properties of drilling fluids are affected by temperature and pressure, but the extent of these effects on the dynamic flow properties is not well known. Measurements of changes of the flow properties of clay-water drilling muds with temperature have been reported by Srini-Vasan and Gatlin.1 The temperatures reported did not exceed 200F, a limitation imposed by the apparatus used by these authors. The rheological properties of clay suspensions were measured at temperatures up to 100C by Gurdzhinian.' Neither the nature of the exchange ions in the clay suspensions nor the degree of purity were defined in his work, nor were the measurements extended to currently used drilling fluids. The lack of systematic measurements of dynamic flow properties at high temperatures and pressures seems the more surprising since during the last decade the importance of the control of the hydraulic properties of drilling fluids has come to be widely recognized. Very good mathematical treatments of the friction losses in drill pipe and annulus have been developed.3 4 These treatments are based on the assumption that drilling fluids behave as Bingham plastic fluids. Quite often this assumption is justified, while in other cases a power law equation pro- duces better fit than the Bingham model does. For convenience in applying viscometer data to pressure-drop calculations, the Bingham plastic flow equation is preferable and, therefore, has been applied to the data reported in this paper, although other equations may fit these data more accurately. In a Bingham plastic fluid the relationship between the shearing stress 7 and the rate of shear D is given by the following equation: where is the plastic viscosity and 4 the yield point. If 4 = 0, the equation for simple Newtonian flow, 7 = pD, is obtained. Two empirical constants are required for the description of laminar flow of a Bingham plastic fluid, and calculations of the flow behavior at high temperatures and pressures cannot be better than is permitted by the accuracy with which these constants are known. For this reason a high-pressure, high-temperature rhe-ometer has been designed to measure the plastic viscosity the yield point +, and the static gel strength S, at pressures up to 10,000 psi and temperatures up to 350F. The important features of its design will be described. The results of measurements on homoionic clay slurries will be discussed insofar as they are relevant to an understanding of the general flow behavior of clay-water drilling fluids. The results of measurements on some typical drilling fluids will be presented also, and their practical implications will be briefly discussed. DESCRIPTION OF EQUIPMENT MECHANICAL FEATURES A viscometer designed to measure the plastic viscosity, yield point and gel strength of non-Newtonian fluids must permit the measurement of the shearing stress t at any given rate of shear D. This is possible only if t and D are approximately uniform throughout the entire sheared sample. A Couette apparatus is the most convenient method of realizing this condition, as has been pointed out by Grodde." The "high-pressure, high-temperature rheometer" described in this paper is basically a rotational Couette viscometer that is immersed in a cell in which pressure and temperature can be controlled over the range of interest. Fig. 1 shows schematically the important features of the pressure cell and associated equipment. The heart of the instrument is the rotating cup. It is shown more clearly in Fie. 2. which revresents the lower one-third of the pressure cell (below the input drive shaft shown in Fig. 1), and it is shown in detail in Fig. 3. For measurements of dynamic flow properties, the rotating cup is driven by a 1/2-hp electric motor, which operates through a Vickers

By R. P. Laforce, ZJ. R. Low, A. M. Turkalo, D. F. Stein

The interaction of the crlloying eletnenls, nickel and chromium, with the impurity elements, antimony, pIzosphorus, tin, and arsenic, to producse reversible temper brittleness in a series of high-purity steels containing 0.40 wt pct C has been investigated. The alloyed steels contained approximately 3.5 pcl Ni, 1.7 pct Cr, and 0.05 to 0.08 pct of the particular irnpurity to be investigated. Susceptibility to teirlper embrittlement was measured by comparing the notched-bar transition temperature of each steel after quenching from the final temper and after very slow cooling (step cooling;) following the final temper. A plain carbon steel without alloying elements, bu/ ud/h 0.08 pel Sh, does not embrittle when step-cooled through the emzbrittling range of temperatures. The same embrittling treatment, applied to a steel with about the same antinzony content but with nickel and chvonziunz added, causes a 700°C increase in transition temperature. If chromium or nickel is the only alloying element, the increase in transition temperature is only 50%, again with antimony present. A carbon-free iron containing nickel, chromium, and antimony shou~s a 200°C shift in transition temperature for the same thermal treatment. Specific alloy-impurily interactions are also observed for the other impurity elements, phosphorus, tin, and arsenic. Additional investigations involving electron microscopy, trzicrohard-ness tests of vain boundaries, minor additions of zirconiutn and the rare earth and noble metals, nzainly with negative results, are also described. HE particular type of embrittlement investigated is that which is encountered in alloy steels tempered in the temperature range from about 350" to 525'C or slowly cooled through this range of temperatures when tempered above this range. This type of embrittlement is sometimes called reversible temper brittleness to distinguish it from the embrittlement indicated by a minimum in the room-temperature V -notch Charpy energy vs tempering-temperature curve encountered in the range 28 0" to 350°C. Temper brittle-ness seriously restricts the use of many alloy steels since it precludes tempering or use in the embrittling range of temperatures and may significantly raise the ductile-brittle transition temperature of heavy-section forgings and castings tempered above the embrittling range, since such sections cannot be sufficiently rapidly cooled after tempering to avoid embrittlement. The very voluminous literature of temper brittle-ness up to about 1960 has been reviewed by woodfine' and LOW.' Of particular significance to the present investigation was the demonstration by Balajiva, Cook, and worn3 that high-purity Ni-Cr steel does not exhibit temper brittleness and the subsequent detailed and systematic study by Steven and Balajiva~ of the effect of impurity additions on the susceptibility to embrittlement of Ni-Cr steels. Steven and Balajiva showed that, of the impurities which may be found in commercial steels, Sb, As, P, Sn, Mn, and Si could all produce temper brittleness in a high-purity Ni-Cr steel. The principal purpose of the present investigation was to study the effects of particular alloy-impurity combinations on susceptibility to temper embrittlement. The steels used were high-purity 0.30 to 0.40 wt pct C steels containing 3.5 wt pct Ni and 1.7 wt pct Cr, separately or in combination. The susceptibility of these steels was then determined when approximately 500 ppm by weight of antimony, arsenic, phosphorus, or tin were added as an impurity. The melting, casting, and forging practices used in the preparation of the materials investigated are described in Appendix A. Table A-I in this appendix shows the analysis of all steels to be discussed. The steels were produced as 20- or 2-lb heats. The smaller heats were used after it had been demonstrated (see Appendix B) that a small, round, notched test specimen could be used to measure the shift in the ductile-brittle transition temperature caused by temper brittleness with about the same result as that obtained by Charpy testing. HEAT TREATMENT Unless otherwise noted, all steels were tested for embrittlement in the tempered martensitic condition. A typical heat treatment for a 0.40 C, 3.5 Ni, 1.7 Cr steel was: 1 hr at 870"C, in argon, quench into oil at 100"C, quench into liquid nitrogen, temper 1 hr at 625"C, and water-quench. The warm oil quench was used where quench-cracking was encountered; otherwise the initial quench was into room-temperature oil or water. For other compositions austenitizing temperatures were 50°C above Acs with the remainder of the thermal cycle the same. Steels in this condition, with no further heat treatment, are designated as non-embrittled. The above quenching and tempering cycle for the 0.40 pct C steels resulted in as-quenched hardnesses of 48 to 53 RC and as-tempered hardnesses of 24 to 31 Rc except in the case of the plain nickel or plain carbon steels. In these, the as-tempered hardness was as low as 80 to 90 Rg. No attempt was made to adjust the tempering temperature to obtain the same hardness in ali steels since it was felt that a uniform thermal cycle was more important than exactly equivalent hardness values. Pro- the standard quench and temper described above, the standard embrittling treatment was "step-cooling". For this the thermal cycle was: 593"C, 1 hr; furnace-cool to 538"C, hold 15 hr; cool to 524"C, hold 24 hr; cool to 496"C, hold 48 hr; cool to 468'C, hold 72

Jan 1, 1969

By Benjamin Webber

MANY of the auriferous placers of the arid Southwest differ widely from the standard types of stream and eluvial deposits of more humid regions, although exhibiting some of the features of each. This diver-gence in characteristics is of geological and economic importance and appears sufficient to warrant the consideration of these placers as a class distinct from both stream and eluvial deposits. It is hoped that the consideration of these auriferous gravels as a distinct type of deposit will facilitate recognition of morphological and economic features that might remain obscure if these deposits were viewed in the light of stream or eluvial placers whose type locality is a more humid environment. "Bajada placer" is proposed as the designation for this type of placer deposit. Bajada is the Spanish term for slope and is used locally in the Southwest to indicate the lower slope of a mountain range, the portion consisting of rock debris and standing at a much lower angle than the rock slope of the range proper. It has been used in a geologic sense by Schrader1 and others. The type locality of bajada placers is the Sonoran Desert,2 where they occur on the bajada or rock debris slope of desert ranges. Stream placers are represented in the Southwest, but most of them lie within the mountain topographic province, the Mexican Highlands2 section of, the Basin and Range physiographic province. Eluvial placers may occur in the mountainous semiarid Mexican Highlands but are almost unknown in the extremely arid Sonoran Desert, as mountain slopes are generally too steep to permit the accumulation of any considerable mantle of residual debris. Since their salient distinctions are almost wholly the result of formation under conditions of extreme aridity, bajada placers are largely confined to the Sonoran Desert, although a few occur in the adjacent Mexican High-lands. They may be modified by the action of ephemeral streams, in which case the placer gravels of these arroyas approach stream placers in type and habit of occurrence, but their relation to an arid environment and the bajada type is usually apparent.

Jan 1, 1935

By L. S. Birks

The bainite transformation in a 3.5 pct Ni-1.25 pct Cr steel was studied under various conditions of cooling and stress. Several characteristics may be specified: 1) transformation in the bainite region (925° to 575°F) is very little affected by the manner of cooling from the austenitizing temperature at 1600°F to 575°F)tothe upper limit of bainite transformation at 925°F; 2) starting time for the bainite transformation is the same order of magnitude for either isothermal transformation or continuous cooling, but the rate of transformation is somewhat greater for isothermal transformation; 3) tensile stress accelerates both isothermal and continuous cooling transformation, and 32,000 psi stress changes the form of the isothermal transformation diagram to correspond in appearance to the continuous cooling diagram; 4) transformation for nonlinear, continuous cooling may not be determined directly from the linear, continuous cooling transformation diagram, but may be predicted by assuming first that the fractional amount of austenite transformed in a given small temperature interval depends on the approximate linear cooling rate during that temperature interval and then by summing stepwise over the whole temperature range. IN a previous publication' an X-ray spectrometer was described with which the X-ray diffraction from a specimen could be observed continuously under controlled temperature and tensile stress. This instrument has now been applied to a study of the austenite-bainite transformation in a Ni-Cr steel for both isothermal and continuous cooling conditions, with and without stress. Certain characteristics of the transformation lead to a method of predicting the amount of transformation to be expected at a given temperature for any type of cooling curve. Material and Specimen Preparation The steel chosen for the investigation was a Ni-Cr steel having the composition in the following percentages: 0.30 C, 0.27 Mn, 0.019 P and S, 3.50 Ni, and 1.25 Cr. In order to fabricate specimens suitable for the X-ray spectrometer, a 1/4 in. plate was ground down to 0.060 in. and then cold rolled to about 0.035 in. Next it was heat treated by quenching in oil from 1650°F and tempering at 1200°F for 1 hr. Then it was etched in dilute nitric acid to reduce its thickness to 0.014 in. and cut into blanks in the shape of flat tensile specimens 3 1/4 Vi in. long, 7/16 in. wide, with a notch % in. long and 7/32 in. wide; see Fig. 1. X-Ray Technique Since the X-ray spectrometer has been described in detail elsewhere,' only a brief outline of the principles will be repeated here. A focusing, pow- der-diffraction arrangement' was used, as shown schematically in Fig. 1, and the specimen was mounted vertically in a vacuum furnace (not shown in the figure). The X-rays, moving in a horizontal plane, enter and leave the furnace through beryllium windows. As shown in the figure, X-rays diverging from the line source A are diffracted by the specimen B and converge at the detector slit C. The detector D and the slit C may be set at the proper angle in the horizontal plane to receive X-rays diffracted by either the face-centered phase (austenite) or the body-centered form (ferrite, bainite, martensite). The specimen is heated by electrical conduction between connectors E, and E,, and a Pt—Pt-10 pct Rh thermocouple spot-welded to the center of the notched region on the side away from the X-ray beam indicates the temperature continuously on a Brown recorder. Temperature control is exercised manually with a variable transformer on the input to E,-E,. Any desired time-temperature relationship is easily obtained by first drawing the desired curve on the temperature recorder chart and then adjusting the variable transformer during the run so that the thermocouple

Jan 1, 1957

By Y. C. Liu, G. A. Alers

The effect of rolling reduction on the textures of Cu-A1 alloys has been investigated both by pole figure and by modulus methods. In alloys which exhibit complete copper or brass types of rolling texture, the rolling reduction has little effect on the texture except to increase the degree of preferred orientation. In alloys which exhibit a transition texture, however, increased rolling reduction increases the amount of brass-type texture at the expense of the copper-type texture. The present experimental results show that there is no one-to-one correspondence between the SFE and the rolling texture of fcc metals. Additional data taken from the literature for fcc metals also support this conclusion. On the other hand, the present and previous experimental results are shown to be in good agreement with the suggestion that the texture transition occurs at a critical value for the separation distance between two partial dislocations—a consequence of the "dislocation interaction" hypothesis for texture. formation. This critical separation occurs when the parameter .r/ub is 3.75 x 10'3. From this, a value for the SFE of 39 ergs per sq cm may be deduced for a Cu-2.85 at. pct A1 alloy. ThE correlation between the rolling texture of fcc metals and the stacking fault energy, SFE, was one of the first attempts to relate atomistic properties with the type of rolling texture.' This correlation gives a qualitative explanation for the experimental observation that the addition of alloying elements, which generally lower the SFE, changes the copper-type texture to a brass-type texture. The simplicity of this correlation had led to its general acceptance and even its quantitative use.' However, it is only a correlation and is largely based on descriptive features of pole figures, and on the poorly known SFE values in dilute alloys. Quantitative verification of this phenomenologi-cal correlation is, in fact, completely lacking. One purpose of the present study is to test this correlation. Another atomistic description for the formation of rolling texture is the "dislocation interaction" hypothesis of texture formation.3 In this hypothesis, the factor controlling the type of rolling texture depends on whether or not the separation distance between two partial dislocations exceeds a critical value. Materials having a separation of less than the critical value are supposed to exhibit a copper-type texture while those with a separation above the critical value are supposed to have a brass-type texture. At the critical value, it is expected that the material should show equal amounts of copper- arid brass-type orientations in their textures, i.e., a 50 pct transition texture. The SFE appears in this hypothesis as only one of several factors which determine the separation distance between partial dislocations. It is possible to test the validity of these two concepts by studying the rolling texture as a function of rolling reduction. Since the SFE per se is an intrinsic property of the metal, it should not, by definition, be influenced by local irregularities, such as variable stress conditions. Thus, no change in texture-type is expected to occur with changes in rolling reduction. On the other hand, according to the "dislocation interaction" hypothesis, any factor that effectively influences the separation distance of partial dislocations would be expected to change the rolling texture. Since the separation distance between partial dislocations is known to depend upon local stresses,4-6 it is anticipated that there would be an effect of the degree of reduction on the texture-type. Also, since applied stresses are more likely to increase, rather than to decrease, the separation between partials,4'5 the overall effect would be to increase the amount of material in the brass-type orientations as rolling reduction is increased. Furthermore, this reduction dependence would be most prominent in alloys exhibiting the transition texture since the distance between partials in those alloys is thought to be close to the critical value. Experimental data in the literature is insufficient to distinguish between these two alternatives. Haessner studied the effect of rolling reduction on textures in a series of Ni-Co alloys by means of the X-ray intensity-ratio technique,' and found that while one texture parameter indicated no reduction dependence the other indicated a slight dependence of the rolling texture on reduction in the range of 96 to 99 pct. As has been noticed previously, the intensity-ratio technique is a convenient but controversial method7 because there is no a priori reason to suggest which intensity-ratio would describe the texture most meaningfully. A more quantitative method of describing textures is found in terms of the orientation dependence of Young's modulus. Here, the type of modulus aniso-tropy associated with the copper-type texture is sufficiently different from that observed for the brass-type texture to allow the two types to be easily distinguishable and a quantitative measure of the amount of each can be deduced from the numerical results. This ability to provide quantitative data is particularly valuable when the two textures occur simultaneously in one alloy as is the case for the transition textures. In this paper the modulus method, supplemented by pole figure data, is used to look for an effect of roll: ing reduction the texture. Also by combining the texture measurements with recent determinations of the SFE in Cu-A1 alloys'0'" it should be possible to test for a relationship between the SFE and textures.

Jan 1, 1970