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By John J. Reed

This paper was prepared as a supplement to the general review by Dr. N. G. W. Cook. His analysis of the problem in terms of the strain energy involved in making the excavation is excellent. It will contribute much towards a clearer understanding of rock behavior and control. Several of the practical applications described herein can be directly related to Dr. Cook's theories and conclusions, and are based on the very same principles. CONTROLLED BLASTING IN ROCK EXCAVATION Generally speaking, the natural rock is a relatively strong and competent structural material, if we conserve its inherent good properties and perhaps reinforce its weak spots. The difficulty often lies in blasting out the tunnel or chamber without damaging the walls and roof we wish to have remain afterwards. Much progress has been made in the last five years in better understanding the controlled excavation of rock. The specialized techniques known as smooth wall blasting and presplit blasting have now developed from the status of curiosities of rock excavation to the point where these techniques are specified in contracts drawn up for such rock excavation projects as tunnels, underground pourer houses, etc. These techniques have been well described and discussed in previous publications; there is no need to reiterate here. It might be well to point out that recent research has demonstrated the effect that inherent rock stress may have on presplitting in certain directions. Material can be presplit most readily parallel to the direction of maximum compressive stress, and this may not always be in the direction desired. Inherent rock stress measurements by stress relief over coring, etc., may have important value in deciding how to best presplit proposed excavations. In addition, recent work at the Colorado School of Mines has demonstrated the feasibility of con-

Jan 1, 1967

By Walter A. Backofen, Donald H. Avery

Intense primary and cross-slip traces were observed in easy glide on Cu: 6 pct-A1 single crystals deformed in tension. A mechanism of cooperative source operation is developed which recognizes that both the applied stress and that resolved from dislocation arrays contribute to the stress on a source. By considering the stress from arrays, the activation of secondary systems in easy glide and the difference in appearance of slip markings on pure and solid-solution crystals are explained. Furthermore the cross-slip system is predicted to be second favored during easy glide for a large range of orientations. FROM many studies of easy glide in fcc metal crystals, a pattern of observations has developed which still requires full explanation. In pure copper, aluminum, and silver, the easy-glide, slip traces are fine and uniform with steps 50 to 100A on the primary* system.1-4 Yet it has not been at all clear why slip in the pure materials should occur in this way. On the contrary, one might expect, with simple slip and a low hardening rate, that the weakest sources on the primary system would operate extensively to produce strong slip traces. In a brass, however, intense slip steps up to 0.5 are found on both primary and cross-slip system4,6-9 seeger10 has pointed out that in a material of low stacking-fault energy such as a brass, extensive easy-glide cross-slip could not be thermally activated, but rather must originate on the cross-slip plane. In further explanation, the wilsdorfs4 and seeger10 noted that only the cross-slip system would not harden differently than the primary, whatever the latent hardening tendencies of other systems; therefore, in brass, which exhibits high latent hardening, the cross-slip is the only secondary system which could be expected to operate extensively, once it became active. The explanation of how the cross-slip system, on which the applied stress is low, becomes activated has been related, in a nonspecific way, to pileups by Hirsch11 and Honeycombe.l2 In the work to be described, deformation traces on solid-solution Cu: 6 pct A1 single crvstals were studied with conventional light microscopy and a mechanism proposed to explain both the observed activation of secondary systems in easy glide and the difference in appearance of slip markings on pure and solid-solution crystals. EXPERIMENTAL In preparing the Cu-A1 single crystals, rectangular bars approximately 0.4 in. by 0.4 in. by 6 in. were first machined from ingots made by vacuum melting copper of 99.999 pct and aluminum of 99.99 pct purity. They were then packed in powdered graphite and the crystals grown in a modified Bridgman apparatus at a rate of 5 mm per hr under an atmosphere of purified nitrogen. Crystal perfection as indicated by Laue back-reflection spots was good except for the last inch to freeze, which was discarded. Orientations so determined are shown in Fig. 1. Tensile specimens with a reduced gage section were obtained by masking the ends with electrical tape and chemically polishing in a solution of 20 pct HNO3, 24 pct HAc, 52 pct H3PO4, 2 pct Hcl, and 2 pct H20 at room temperature.13 Finally, the specimens were electropolished in a 30 pct ortho-phosphoric acid bath at 12 v. Tensile deformation was performed in an Instron testing machine at a strain rate of approximately 1 pct per min. During easy glide, extensive cross-slip was observed with all crystals, in spite of the low Schmid factor on this system, and in no case was any other secondary trace encountered. A certain sequence of slip-line development was associated with the extension. At yielding, intense primary traces passing completely through the crystal developed at some point on the gage section, generally near the grips; weak cross-slip traces also appeared, extending from the primary traces into the adjacent undeformed crystal, Fig. 2. Further extension led to primary traces adjacent to the first-formed and connecting with those of the cross-

Jan 1, 1963

By R. Lyndon Arscott, P. Hackett

This chapter reviews the early stages of a study designed to investigate the physical behavior of the coal measure rocks around longwall panels over a relatively large area. The aim of the work is to attempt to explain a directional tendency for a certain type of underground fracture. The geological structure of the area is reasonably uniform but the effect of some local anomalies is also discussed. Although some definite tendencies have been recorded, the results so far achieved need confirmation by further experiments. The chapter deals first with some in-situ strain measurements carried out in longwall panels and continues with a discussion of the relationships between induced fractures and the natural variations in the structure of the rock mass. Finally, some light is shed upon the gas outburst phenomenon although eradication of the hazard is far from assured. STRESS AROUND A LONGWALL PANEL Considerable progress has been made during the last few years towards the determination of the mechanism of failure of small samples of rock under varying environmental conditions. Much more laboratory testing needs to be done in this field but an even greater amount of study needs to be devoted to the extrapolation of laboratory phenomena to failure around underground excavations. The problem is made more difficult because the stress redistribution around an excavation is often difficult to define, particularly when part of the rock mass fails and a

Jan 1, 1972

By Milan Matula

One of the main characteristics of the development of rock mechanics in some countries is a close cooperation between experts in rock mechanics and workers in related fields, including soil mechanics and engineering geology. The purpose of this chapter is to outline the contribution that engineering geology can make to rock mechanics and to present a few examples of engineering geology studies that have been used in solving some practical rock mechanics problems. Engineering geology investigations dealing with the influence of geological factors on the physical properties of rock materials and rock masses fall into three main categories : 1) Systematic study and correlation of the physical properties of the main rock types with the petrogenetic evolution that caused the differences in the properties of these various rock types. 2) Study of the heterogeneity and anisotropy of both rock materials and rock masses. 3) Delimitation of rock masses which are approximately uniform in physical properties (quasihomogeneous units). Delimiting of the quasihomogeneous rock masses is the main contribution that the engineering geologist can make to rock mechanics. This delimiting is based on the evaluation of many complex geologic factors, not on test results alone, and therefore is most effectively done by trained engineering geologists. The foregoing types of studies are being used in Czechoslovakia for several purposes, including : 1) the compilation of regional engineering petrologic data-that is, the systematic definition of the main rock types of the country in terms of their representative physical characteristics;

Jan 1, 1970

By S. Fugleberg

As a result of research work done during the planning of the Kokkola zinc plant it was found that a very efficient cementation of impurities from the suspension obtained after leaching copper and cadmium cakes was achieved by adding zinc dust to the batch without filtration after the leaching. All elements nobler than cadmium are precipitated with the exception of lead, which must be removed in a separate step. Using pure zinc dust, free from noble metals, the cadmium sponge produced will only contain elements that can be re- moved from cadmium by meltrefining. The process is thus : 1. Leaching and purification 2. Removal of lead (with BaCO3) 3. Precipitation of cadmium sponge with pure zinc dust 4. Meltrefining of briquetted sponge with NaOH for removal of Zn (and others) The paper deals with the removal of the most critical elements, i.e. Co, Ni, As, Sb, Cu, Pb, T1 in the liquid phase and Zn and T1 in the melt. A survey is also given of the behaviour of most of the other elements normally found in Cd raw material, such as Ge, Te, Se, Sn, In, Ga. It is shown that in most cases the benefit of an electrolysis in Cd production is very limited. In Kokkola 99.998% Cd is achieved by this method, but in favourable cases it may be possible to come quite close to five nines.

Jan 1, 1973

By Robert H. Richards, Richard W. Lodge

A great deal of speculation, as well as actual experiment, has been devoted to ascertaining the changes in the materials (luring their descent in an iron blast-furnace, affecting (1) the chemical constitution, (2) the mechanical condition, and (3) the arrangement of the materials. With a view to throw some light upon the third question, we constructed a model and tried experiments which are here described. Our model is a vertical section of a furnace, with the lines of the Edgar Thomson furnace D of 1885 for the use of which we arc indebted to Mr. Gayley. The model is 40 inches high, and made to scale (1/2 inch equals 1 foot), and the horizontal section of the space through which the charge falls at any point in the descent is 11/2 in. x d, d being the diameter of the furnace at that place. We are unable to say just where the idea of making this model came from ; perhaps, partly from The Principles of the Manufacture of Iron, and Steel, 1884, I. Lowthian Bell, p. 124 ; partly, also, from

Jan 1, 1888

By V. F. Marsters

Peru has produced petroleum since the early seventies, the first work being in the Zorritos field, in the Province of Tumbes, adjoining Ecuador. In the early nineties, the Negritos field, in the Department of Piura, came into prominence, and by 1905 had attained an annual production of 335,160 bbl. The early development of the field was under the general direction of the London & Pacific Petroleum Co., but it is now handled by the International Petroleum Co. In 1900 and 1901, the Lobitos field became the scene of marked activity. In 1905, its total production amounted to 75,000 bbl.; it has continued to increase as has Negritos. From 1897 to 1902, there was prospecting in the region of La Brieta (or Fernandez), on the Mancora River, about 25 to 30 km. from the coast. Small production of a heavy oil was obtained from three different sands. So far as the author knows, no work has been done in that locality since 1902. There are thus four distinct fields in the north endof the Peruvian coastal plain. The, remaining productive locality of Peru is the Pirin or Pusi field, at the northwest end of Lake Titicaca, Department of Puno, in southern Peru. The first prospecting near Pusi was done by Brown Brothers, of Los Angeles, Calif., who obtained modest production about 1906; according to reports, activities ceased about 1914 or 1915. The maximum annual production was obtained about 1908, estimated at 76,000 barrels. Peru possesses two distinct geographic provinces in which we may look for the development of a larger oil industry; namely, the coastal plain province, and the inter-Andean plains.

Jan 7, 1922

By Ernest A. Hersam

The small amalgamation-test of the laboratory is not always reliable as a basis for important decisions as to the character and commercial treatment of ores. The conditions of continuous practice on a large scale are not always reproduced in the brief laboratory-test. Sometimes such a reproduction would be very difficult, or impracticable; sometimes it is not even attempted, and the test is performed in a rough way, without regard to the effects of small variations in the methods pursued. The aim of a laboratory amalgamation-test is to learn how much of the gold or silver in an ore can be economically recovered by amalgamation on a commercial scale. The yield can be increased, perhaps, by additional chemical treatment or by extreme comminution of the ore; but this might cost more than the value of such increase. Moreover, in practice, other operations often follow amalgamation; and these operations may remedy a defective extraction by amalgamation, more economically than could be done by directly increasing that extraction. The test should be performed, therefore, upon a uniformly-sized material, and under conditions that are precisely known and capable of being exactly duplicated, or purposely modified. The crucial feature of the test is the effectiveness of the contact made between the gold or silver of the ore and the amal-gamating-surfme. This may depend upon the temperature; the duration of contact; its force, due to gravity or impact; the hardness, plasticity or liquidity of the amalgam; the roughness or other quality of the amalgam-surface; the scouring action of the ore upon the amalgam, or the suspension and

Jan 1, 1905

By David B. Burrows, Rlkl Kobayashi, Norman L. Carr

The viscosity of hydrocarbon mixtures, whether in the gas or liquid phase, is a function of pressure, temperature, and phase composition. This paper presents methods for the prediction of the viscosity of the gas or less dense fluid phase over the practical range of pressure, temperature, and phase compositions encountered in surface and subsurface petroleum production operations. The correlation necessary to predict the effect of pressure on viscosities is presented in Part I. Serious discrepancies in high pressure gas viscosity data in the literature are discussed. The application of the correlation to predict absolute viscosities is discussed in Part 11. Auxiliary correlations are presented to enable calculations of viscosities from a knowledge of the pressure, temperature, and gravity of the gas phase. INTRODUCTION A knowledge of the viscosity of hydrocarbon fluids is needed to study the dynamical or flow behavior of these mixtures through pipes, porous media, or more generally wherever transport of momentum occurs in fluid motion. Since flow is predominantly in the laminar region in petroleum reservoirs, the influence of fluid viscosity on this flow is especially important. As early as 1894, Onnes1 and Onnes and de Haas' noted that the viscosities of homologs under corresponding states could be correlated. The theorem of corresponding states has been further developed and applied to the viscosity of pure, nonpolar gases under pressure by Comings, Mayland, and Egly.3 It was demonstrated that the viscosity ratio could be expressed rather closely as a function of reduced pressures and temperatures, 1.e.: µ/µ1 = f( TR2 PR) ........(1) temperature, absolute units where: TR =------------------------------ ------ critical temperature. absolute units _pressure, absolute units critical pressure, absolute units µ = viscosity of gas at reduced temperature TR and reduced pressure PR µ1 =. viscosity of gas at atmospheric pressure and at temperature TR Serious discrepancies in the viscosity of pure hydrocarbon gases at high pressures have been called to Our attention by Comings, and and Egly. They made a careful analysis of the following methods commonly used to measure gas viscosities: 1. Oscillating disc viscometer4,5 2. Rolling ball viscometer6,7 3. Capillary tube viscometer12 On the basis of their analysis of the problem and their experimental data on the viscosities of methane, ethylene, carbon dioxide, and propane, they preferentially selected data obtained by the capillary tube viscometer to develop their viscosity correlation. Since then a need has existed to verify the experimental technique of Comings, Mayland, and Egly for the determination of viscosities at high pressure; to extend the data to mixtures of hydrocarbons; and to extend the range of their correlation to include higher pressures. Using the correlation procedure of Comings, May-land, and Egly, the prediction of gas viscosities is resolved into the correlation of the effect of pressure, temperature, and composition on the viscosity of hydrocarbons and their mixtures and the prediction of viscosities of mixtures of hydrocarbons and other natural gas components at one atmosphere pressure.

Jan 1, 1955

By J. B. Woodworth

Under the above title it is desired to bring to the attention of assayers a short-cut method which has been perfected by Mr. A. S. Warren, of Buffalo, and the writer; has been used several years at three " Lake copper " refineries in occasional alternation with the regular " combination," or a wet and fire," assay; and has proved more rapid, and rather more accurate than the latter on all refined copper—namely, the direct cupellation of the silver chloride (+gold) precipitate, without scorification. No claim of priority is made for this direct method, as it has suggested itself to many others, and was mentioned by Mr. Warren in the symposium of assayers' results brought together in 1895 by the Secretary," after the plan and suggestions of Dr. A. R. Ledoux.† Lately, this important subject of assaying copper-materials seems to have been re-opened for discussion. The shortening of time by 'the direct method is so considerable (nearly 20 minutes on a batch)—to say nothing of the saving

Jan 1, 1902

By G. W. Tuffnell, S. Floreen

Three Fe-18 pet Ni-base ternary alloys cortaining carbon, molybdenum, or cobalt were aged to pgroduce hardening by carbides, Ni3Mo, or ordering, respectively. Each alloy was tested in rotating-beam fatigue tests after hardening to 195 ksi ultim.ate tensile strength. The fatigue properties of three alloys soere essentially identical. The results suggest that tlze fatigae strength of an igron-base alloy should depend primarily upon the tensile strength, and not iipon the hardening mecaanisrn. THE fatigue strengths of many steels have been found to be directly related to their ultimate tensile strengths. For ultimate strengths below 200 ksi, the fatigue endurance limit at 107 to 10' cycles is approximately half the ultimate strength. Essen- tially all of the steels that have been tested, however, have been hardened by carbon. Thus it is not certain whether the relationship between fatigue and ultimate strengths is a general one that applies for other types of hardening in steels, or whether it applies only for the particular method of hardening by carbon. The recent developments of the martensitic precipitation-hardened stainless steels and the marag-ing steels have shown that it is possible to achieve high strengths in iron-base alloys by other hardening mechanisms than that due to carbon. Therefore, it is now possible to compare the fatigue properties of several iron alloys having the same ultimate strengths but hardened by different mechanisms. For the present study a binary Fe-18 pct Ni martensite was selected as a base material. This particular matrix composition has been found to have deformation characteristics very similar to pure iron.' Three ternary alloys were prepared by adding either 0.23 wt pct C, 5 wt pct Mo, or 20 wt pct Co to this base composition. After suitable heat

Jan 1, 1965

By M. G. F. Söhnlein

IN THE metallurgical treatment of sulfide silver-tin ores mined at Oruro, Potosi, and Chocaya, the most important and difficult step is chloridizing-roasting. The ores are chiefly mined from veins in rhyolite, a detailed description of which can be found in most textbooks on ore deposits. The chief gangue minerals are Pyrite and quartz, and the silver content is derived from tetrahedrite, jamesonite, stibnite, and cylindrite. Most of the tin is present in the form of a rather impure cassiterite, which forms microcrystalline aggregates of varying richness with quartz and pyrite; occasionally, some tin is found as stannite, cylindrite, and other complex sulfantimonates. The silver content of the minerals that compose the ore is approximately as follows: Pyrite, 3 to 5 oz. per ton; jamesonite, 30 to 50 oz. per ton; stibnite, 30 to 150 oz. per ton; cylindrite, 200 to 300 oz. per-Jon; tetrahedrite, 500 to 3000 oz. per ton. Occasionally, some ruby silver ore is found, but it is very rare. In the mines of Oruro, which are the deepest in the sulfide zone, tetrahedrite has nearly disappeared, stibnite, jamesonite, and, in the deepest levels, cylindrite taking its place. At present, there are six mills treating this ore, two at Potosi, two at Chocaya, one at Poopo, and one at Machacamarca. The ore is crushed dry, given a chloridizing roast, leached with water and hyposulfite solution (or with brine) to extract gold, silver and copper, and concentrated for tin with or' without regrinding.

Jan 8, 1920

By B. M. Larsen, T. E. Brower

In two previous paperslJ dealing with the carbon-oxygcn reaction, and the simultaneous content of each, in liquid steel in the furnace, we have made use of the quantity A[O], defined as the excess oxygen beyond what would be in equilibrium with carbon then present if the pressure of carbon monoxide were I atm.; that is, if [C] X [O] is taken as 0.00222, A[O] = [O] - 0.0022[C] where [O] is the percentage of oxygen by weight as measured by the method described earlier.3 This quantity ?[O] proves to be substantially independent of carbon content over the range 0.08 to I,z per cent, as well as of the basicity of the slag, and is nearly always within the limits o.o15 to o.oz5 per cent when the bath is boiling normally and is in what we have termed a steady state, Apparently it must be at least about 0.014 per cent before boiling occurs; but this threshold value seems to depend upon the ease of bubble formation at the metal-hearth interface, hence upon the condition of the surface of the hearth. In any case, ~(01, on the average, changes considerably following any disturbance of the bath, as by addition of ore. The present paper deals with the average changes in A[O] level following addition of spiegel or crop ends, or after procedures to promote stirring, or by tapping of the steel from the furnace. The observations were made on a large number of commercial heats, and consequently are subject to the influence of various disturbing factors; the results have the compensating merit of showing the consistency obtainable under the limitations imposed by practical operation. Variability of Excess Oxygen in Normal Open-hearth Operation The preceding genera' statements refer to the average value of A[0] particularly in heats that are boiling actively; on individual heats, which are less active, there may be a variable time lag between the disturbance and its effect, which complicates the interpretation of what is going on. For instance, if in the normal refining process boiling is sluggish, the slag usually is gaining Oxygen from the gas phase above it, Or from added Ore$ faster than it is losing oxygen to the metal; Yet when the bath starts to boil vigorously, the opposite condition may prevail for Some time. The consequence of this lag is a variation of A[o], the interpretation of which in a sing1e heat may not be immediately obvious. This condition is illustrated in Figs. I and 2. In Fig. 1, A[0] at the beginning of the test period was near the lower limit of its usual range (dashed lines) in the steady state as a consequence of the lime boil, which had ended about as indicated. The bath is now cold, carbon drop is slow, and the first small orc feed causes only a small rise in A[O]; as the temperature rises and as lime dissolves in the slag, and the bath becomes more active, the

Jan 1, 1948

By B. M. Larsen, T. E. Brower

In two previous paperslJ dealing with the carbon-oxygcn reaction, and the simultaneous content of each, in liquid steel in the furnace, we have made use of the quantity A[O], defined as the excess oxygen beyond what would be in equilibrium with carbon then present if the pressure of carbon monoxide were I atm.; that is, if [C] X [O] is taken as 0.00222, A[O] = [O] - 0.0022[C] where [O] is the percentage of oxygen by weight as measured by the method described earlier.3 This quantity ?[O] proves to be substantially independent of carbon content over the range 0.08 to I,z per cent, as well as of the basicity of the slag, and is nearly always within the limits o.o15 to o.oz5 per cent when the bath is boiling normally and is in what we have termed a steady state, Apparently it must be at least about 0.014 per cent before boiling occurs; but this threshold value seems to depend upon the ease of bubble formation at the metal-hearth interface, hence upon the condition of the surface of the hearth. In any case, ~(01, on the average, changes considerably following any disturbance of the bath, as by addition of ore. The present paper deals with the average changes in A[O] level following addition of spiegel or crop ends, or after procedures to promote stirring, or by tapping of the steel from the furnace. The observations were made on a large number of commercial heats, and consequently are subject to the influence of various disturbing factors; the results have the compensating merit of showing the consistency obtainable under the limitations imposed by practical operation. Variability of Excess Oxygen in Normal Open-hearth Operation The preceding genera' statements refer to the average value of A[0] particularly in heats that are boiling actively; on individual heats, which are less active, there may be a variable time lag between the disturbance and its effect, which complicates the interpretation of what is going on. For instance, if in the normal refining process boiling is sluggish, the slag usually is gaining Oxygen from the gas phase above it, Or from added Ore$ faster than it is losing oxygen to the metal; Yet when the bath starts to boil vigorously, the opposite condition may prevail for Some time. The consequence of this lag is a variation of A[o], the interpretation of which in a sing1e heat may not be immediately obvious. This condition is illustrated in Figs. I and 2. In Fig. 1, A[0] at the beginning of the test period was near the lower limit of its usual range (dashed lines) in the steady state as a consequence of the lime boil, which had ended about as indicated. The bath is now cold, carbon drop is slow, and the first small orc feed causes only a small rise in A[O]; as the temperature rises and as lime dissolves in the slag, and the bath becomes more active, the

Jan 1, 1948

By Carl Zapffe

The object of the Bradley process is to free manganese oxide from its associated gangue and separate the contained iron oxide by dissolving the manganese and precipitating it from the solution. This results in producing two oxides as concentrates, the one to be converted into a manganese sinter and the other into an iron sinter. The manganese sinter may be made to contain as high as 70 per cent. inanganese and as low as 1 per cent. silica, with phos'phorus not to exceed 0.02 per cent, and from that figure downward to about 0.005 per cent., and with sulfur at 0.007 per cent. The iron sinter contains about 2.50 per cent. manganese, making the total recovery of the manganese 98 per cent. The method involves selective roasting, which converts the manganese into a form in which it is soluble in an aqueous solution of ammonium sulfate, then precipitating the manganese as a hydrate by using ammonia gas, then stabilizing and washing the hydrate, followed by sintering; concurrently most of the iron oxide is converted by roasting into an insoluble form and becomes a residue with magnetic qualities, which makes possible the recovery of much of the iron in the ore. Leaching manganese by using sulfur dioxide gas was shown possiblc Inany years ago. Mr. Bradley tried it for a year, working in conjunction with the original experimenters of that method, and found that while relatively pure inanganese oxide could be produced, the likelihood of developing a commercial process along this line was not very encouraging. He also attempted leaching with nitric and sulfur acids, but the cost of recovery mounted and the quality of the product was not as good Mr. Bradley tried nearly every leaching method proposed, and the expen-ments were made on a large scale in the spacious laboratories of John C. Wiarda & Co., in Brooklyn, N. Y. Insufficient encouragement was discernible in the results obtained. Upon the suggestion of N. Arthur Laury, of John C. Wiarda & Co., Bradley undertook using arnrnoniurn sulfate. Because a high rate of recovery appeared feasible, Bradley planned the erection of a 4-ton pilot plant at the State of Minnesota Mines Experiment Station, at Minneapolis. The results of that work are described in this treatise.

Jan 1, 1929

By Howard N. Eavenson

WHEN the A.I.M.E. was formed 75 years ago the bituminous coal industry was in its swaddling clothes, although it had been operating for more than a century and coal was being mined in every state now producing it, and its output had long passed that of anthracite. In 18/1, the value of bituminous coal was about seventy per cent of the value of all metals produced and more than one fifth of the value of all products of mines, both metallic and nonmetallic.[1a] While many of the operating mines then shipped by rail, most of the development was along waterways, although the canal era of transportation was nearly at its end. Coal mining is a heavy industry and one of the best measures of its progress is its output throughout the period. Fig. 1 shows this graphically from 1800 to 1945. From 1870 to 1910, the production-which is very nearly the consumption-almost doubled every decade, a most amazing growth. In 1918, in World War I, a peak was reached and a decline began, which ended in 1932. A gradual recovery then started, interrupted in 1938 but culminating in the record output of 1944, when, owing to World War II, a tonnage of 619,576,000 was produced. It is evident that the forces leading to the continuous increase ending in 1918 have spent themselves and that only unusual conditions will require so large a production again. The postwar conditions of World War II will probably

Jan 1, 1947

By J. R. Hornaday, A. E. Morris, N. A. Parlee, D. C. Carmichael

Rates of absorption and effusion of hydrogen in solid iron were measurede by a Sieverts type of apparatus. With clean a iron these rates are diffusion controlled down to 420°C and are represented by the equation D = 6.70 x e-'100' crn2 sec-I Certain surface impurities can affect these rates at all temper-atuves. Thin oxide films lower, the apparent diffusivity of annealed iron markedly. Cold-worked iron (75 pct) annealed at 430°C has practically the same solubility and diffusivity as anealed iron. THE mechanism of absorption and evolution of hydrogen in solid iron alloys is not fully understood despite the large number of investigations on the subject. While there appear to be many instances of simple solid-state diffusion control of rate, there are many cases where investigators have either concluded that surface reactions are rate controlling or that some "nondiffusible" hydrogen resides in discontinuities. The purposes of this research were 1) to develop a sound method for studying this absorption and evolution behavior, 2) to examine it in pure annealed iron, and 3) to determine the effects of important variables, such as cold work, surface condition, and composition. This paper relates the progress toward these objectives. Much of the present knowledge of the movement of hydrogen through iron alloys comes from permeability studies which involve the measurement of the rate of passage (under steady state conditions) through membranes of the order of 1 mm in thickness. This method is open to question on various grounds. If surface reactions are involved, two different surfaces operating under two different conditions must be considered. The presence of defects in the membrane even of microscopic dimensions may lead to erroneous results. A few people have studied evolution of hydrogen into vacuum, under carefully controlled (unsteady state) conditions, and some of the best diffusivity data come from these sources. Most of these methods measure rates of evolution only and thus do not make a rigorous test for reversibility of behavior. It appeared that an "unsteady state" method that would permit the measurement of both rates of evolution and absorption under controlled temperature, pressure, and other conditions would offer several advantages. Accordingly the modified Sieverts apparatus described below was designed and built. APPARATUS This apparatus is shown in Fig. 1. The sample bulb is detailed in Fig. 2. Hydrogen of 99.5 pct purity and argon of 99.99 pct purity were used. The hydrogen was deoxidized and dried by means of a Deoxo unit followed by a "Dri-erite" tower. The argon was only dried. The gas burette was graduated in tenths of a cubic centimeter, and, with the aid of a travelling magnifier, readings could be estimated to the nearest 0.01 cc. The level of mercury in the burette was adjusted by means of a leveling bulb operated by a fine screw adjustment. An electrical system, consisting of two slightly separated platinum electrodes inserted in one leg of the manometer and a small light bulb was used to obtain rapid accurate adjustment of the pressure. The capillary tubing of the Vycor sample bulb was 3 mm bore as was all tubing back to the gas burette. The samples were discs made from vacuum-melted Ferrovac-E iron of greater than

Jan 1, 1961

ALTHOUGH the open-hearth charge contributes CO, C02, H2, and water vapor to the combustion gases and absorbs oxygen from them, in the main the thermal effects in the melting charge and molten bath can be considered independently of those in fuel combustion; the latter then is regarded simply as the source of the net heat required to finish a heat of steel. First of all, it should be remembered that a large percentage of the heat supplied to the bath is furnished by oxidation of the various elements in the charge itself. If this charge consisted of 80 to 100 per cent of hot metal and the oxidation were accomplished by blowing in air or oxygen, as in the bessemer converter, the net heat absorption would be negative; that is, the bath would contribute part of the heat required to keep the melting chamber hot, in addition to that contained in the finished steel and slag. - In actual open-hearth practices, probably the nearest approach to this is in the duplex furnace, charged with bessemer-blown metal and some hot metal, where very little heat is required to complete the refining and nearly all the heat energy from fuel combustion is used to keep the roof and walls of the melting chamber up to around 2900 to 3000 F (1600 to 1650 C), so that the bath will not cool off during the refining. The other extreme is with all-cold charges containing around 80 per cent steel scrap and 20 per cent cast iron or cold pig iron, in which case a very large proportion of the heat in the bath at tap is supplied from the fuel combustion. THERMAL EFFECTS IN MELTING In a typical heat, the fuel furnishes about four million British thermal units per ton of steel produced. The heat required for the metallurgical processes is not easily defined in useful manner but it ranges downward from about one million Btu, depending not only on the charge but on the manner of calculation. In any event, this requirement appears small in comparison with the

Jan 1, 1951

By Hiroshi Oikawa, R. G. Blake, A. G. Guy

An equatzon has been derivedfor conveniently calculatzng the couvse of homogenzzation in a three-corviDonent solid solutiorz. The necessary assumptions are that the initial distributions of concentration are sinusoidal and that the four interdiffusion coefficients are constant. Employed in the deriuation were the Laplace transform and the fouter Fourier sine transfovwz. The final equation is shown to be in good agveetnent with the experimental results of Kirkaldyet al. on Cu-Sn-Zn alloys. COMMON boundary conditions for representing physical problems are those of the finite solid and of the infinite solid. Many metallurgical phenomena, however, have the geometrical form of a finite pattern reproduced throughout an infinite solid. Precipitation within a uniform matrix and segregation during solidification are examples. The purpose of this treatment is to show that a convenient and useful mathematical analysis is possible in those cases in which the finite pattern can be approximated by a sine function. The particular topic to be considered here is the elimination of segregation by diffusion, but the mathematical model has applicability in many other areas. It should be recalled that the mathematical solution of a typical problem involving a finite solid, such as diffusion into a thin layer, is quite involved.' Various types of solutions are used depending on the degree of advancement of the diffusion process and on the initial conditions. A step function is the simplest initial condition, but even in this case the general solution has the form of an infinite series. Kirkaldy et a1.2 have

Jan 1, 1968

By R. F. Mehl, M. Gensamer

THE stresses which initiate deformation processes in metals are fundamentally important in the study of the mechanical properties of metals. A point of inflection in the load-elongation curves obtained for single crystals1 has been rather too readily interpreted as a true yield point, and the critical resolved shearing stress on the plane of slip taken as a material constant. Even early work showed that the stress at this point varies with rate of loading, but it has not been generally appreciated that creep tests under static loads alone are suited for determining the existence or nonexistence of a yield point.2 It has now been shown by Miller that single crystals of zinc3 when loaded statically begin to yield at loads too small to measure; as a result there is no case now known, apart from that cited in the present paper, in which a true critical stress for yielding has been demonstrated for single crystals of metals. The case of iron has especial interest: the existence of an upper and lower yield point and of an elongation at the yield point in ordinary iron and steel marks this substance as unusual, though the effects have been found to a very minor degree in other metals and alloys. ‡ Most alloys do not show such marked phenomena when appreciable yielding begins, and accordingly modern practice is to speak of the yield strength of such materials, a stress read from the load-elongation curve after elongation has begun, rather than yield point. The special behavior of iron suggests that it is more likely that single crystals of iron should have a true yield point than other metals. The study of the mechanical properties of metals and alloys requires a determination of the crystallographic mechanism of deformation, whether deformation proceeds by slip, twinning, or cleavage, or a combination of these, and a determination of the stresses that induce these modes of

Jan 1, 1938