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By AIME AIME

PRIZES totaling $450 were awarded at the Annual Meeting luncheon on Monday, Feb. 9, to the winners of the third national student prize paper contest. The undergraduate prizewinners, each of whom received a check for $100, were as follows: Mayo W. Lanning, Lafayette College, for his paper entitled ?Some Aspects of the Mining Methods Employed at the Scrub Oak Mines of the Alan Wood Steel Company,? (entered by the Lehigh Valley Section). Charles F. Parent, Montana School of Mines, for his paper entitled ?Relationships of Manganese Minerals in the Butte District,? (entered by the Montana Section). Harry Czyzewski, University of Illinois, for his paper entitled ?A Metallurgical Study of Cast Irons Used for Glass Molds,? (entered by the Chicago Section).

Jan 1, 1942

By J. S. Ross

Although the opinion has prevailed for several years that bottoni-hole choking under certain flow conditions should effect an increase in flow efficiencies, the use of bottom-hole chokes until recently has been limited in application mainly because of mechanical difficulties encountered in their construction. Within the past year, however, bottom-hole choking, through the development of a removable type of choke, has been applied successfully under various conditions of flow in many Mid-Continent fields. The observation of these field tests indicates that bottom-hole choking, although not applicable to all flow conditions, has an important place in the operation of oil and gas wells. This paper gives briefly the conclusions drawn from the data obtained from the experiments with this bottom-hole choke under various flow conditions, and a description of the choke and its operation. Purpose of Bottom-hole Choking Since, in a normal well, the velocity with which the column of gas is moving generally has a direct bearing upon the quantity of oil it can lift, probably the main purpose of bottom-hole choking is to accomplish an increase in the velocity of this- rising column, particularly in the lower portion of the tubing string. This it does first, by expansion of the free gas accompanying the oil; next, by liberation and expansion of some of the occluded gas normally carried in the oil to the surface; and lastly, by atomization, which results in a more intimate and uniform mixture of the oil and gas. It is apparent, then, that if this velocity, particularly in the lower portion of the flow string, at a given rate of production, is inefficiently low, owing either to an insufficient supply of gas or to excessive surface choking, and slippage takes place, bottom-hole choking should bring about an increased velocity of the gas and hence an increased lifting capacity. But if the velocity of the column of gas at this same rate of production through a surface choke alone is at or above a velocity necessary to lift the oil efficiently, increasing the velocity by bottom-hole choking would probably serve no useful purpose, other than to steady the flow by the better mixture of oil and gas and to lower delivery pressures.

Jan 1, 1932

By George D. Graffin

The first use of graphite is lost in the mists of time. It was used by primitive man to make drawings on the walls of caves and by the Egyptians to decorate pottery. As early as 1400 A.D. graphite crucibles were being made in the Haffnerzell district of Bavaria. Through the Middle Ages graphite was confused with other minerals, especially galena and molybdenite. Two common names that are still used for the mineral are "Plumbago," meaning leadlike, and "Black Lead." The latter name implied that graphite is either composed of lead or at least contains a large percentage of it. Gessner is credited with having recognized it as a separate mineral in 1565, but its composition was not determined until 1779, when Scheele demonstrated that graphite oxidized to carbon dioxide, thus proving its carbon constitution. In 1789, Werner named it "graphite" from the Greek word "graphein," meaning to write. The United States has long relied on foreign countries for its graphite supplies. This reliance has been due more to the lack of suitable domestic graphites than to any particular preference for buying minerals overseas. Ceylon (now Sri Lanka) graphites were imported as early as 1820, and Madagascar graphites have been imported since the properties on that island were opened up about a hundred years later. Mexico has long supplied the United States with most of its requirements for amorphous graphite. Physical Properties and Classification Graphite is found in laminated, flaky aggregates disseminated in schistose rocks. It also occurs in veins and exhibits a foliated or fibrous structure. Graphite is a black lustrous mineral that crystallizes in the hexagonal system, with rhombohedral symmetry. The crystals have tabular form and are six-sided; the faces are commonly striated. The flakes have perfect basal cleavage and are opaque. When well crystallized, the flakes have a black metallic luster while the amorphous material is black and earthy, with a microcrystalline compactness. The flakes feel greasy. Graphite is an excellent conductor of heat and electricity. It melts at approximately 3500°C and sublimes at about 4500°C. It is combustible in the presence of oxygen between 620° and 670°C, but is stable and chemically inert at ordinary temperatures.

Jan 1, 1975

By AIME AIME

LEWIS EMANUEL YOUNG was elected a Director of the A.I.M.E. at the last Annual Meeting as a representative of District '4, including. Ohio, West Virginia, and western. Pennsylvania and New York. He also represents the Coal Division, in which industry lie has actively participated- for nearly twenty years. Dr. Young was horn in Topeka, Kan., Oct. 1, 1873, received mining degrees from Penn State and ,-Iowa. State, and a Ph.D., from Illinois. The first part of his professional life was spent in teaching first as instructor in mining at Iowa State, second .as professor of mining at the Colorado School' of Mines, third as director of the School of Mines and Metallurgy at Rolla, Mo., and finally he taught business

Jan 1, 1937

By K. D. McBean, W. H. Hannay, B. A. Stimmel

The electrolytic plant at Trail, B. C., was erected by the Consolidated Mining and Smelting Company of Canada, Ltd., for the treatment of zinc ores and concentrates, particularly those of the Sullivan mine at Kimberley, B. C. It began operations in 1916 at a rated capacity of 60 tons of cathodes per day, which has been steadily increased to the present production of 400 tons per day. The Sullivan has furnished the greater part of the zinc so far produced, although notable tonnages of customs zinc concentrates have been treated. The maximum yearly tonnage of customs concentrates, 25,000 tons, was treated in 1926. Practically no customs concentrates hale been treated since 1929. The total bar zinc production to the close of 1935 was 1,092,782 tons. The zinc mineral in the Sullivan ore is marmatite of somewhat variable composition, ranging between 6ZnS.FeS and 8 ZnS.FeS. Practically all the zinc ores tributary to this plant are marmatites; and the iron content of the zinc mineral varies considerably. The formation of zinc ferrite during roasting is now a matter of common knowledge, so the possible extraction from any zinc concentrate is largely a function of the iron content; the progress made in concentration is reflected directly in zinc-plant recovery. The Trail plant operafes on the low-acid system, as do all the other major plants on this continent at present operating, except the electrolytic plant of the Sullivan Mining Co. at Kellogg, Idaho. The new Magdeburg plant, in Germany, occupies an intermediate position between high and low acid. Plant operation at Trail will be treated in this paper under five main sections: roasting, leaching and purification, electrolysis, cadmium recovery and melting. The oxide section of the plant, treating zinc fume from re-treatment of lead blast-furnace slag, is practically a separate zinc plant; this is necessary because of the presence of fluorine in the smelter zinc fume. Cadmium is recovered electrolytically from the purification residues of both the sulphide and oxide leaching plants.

Jan 1, 1937

By D. D. Pollock

Many constitution diagrams do not indicate the limits oJ solid solubility of the silver-rich solid solutions below 200°C. Thermoelectric measurements were employed to determine this limit in the nieighborhood of room temperature. The appearance of a second phase causes a discontinuity to occur in the tkevtrroelectric power as a function of cornposition at constant temperature and pressure. This discontinuity was employed to determine the limits of the silver-rich terzinal solid solutions of the Ag-A l, Ag-As, Ag- Bi, Ag--Ge, Ag-In, Ag-Pb, Ag-Sb, and Ag-Sn systenls at 30°C. CONSIDERABLE work has been done on the constitution of binary alloys of silver. The available data have been compiled by Hansen1 and Elliott.2 However, many of the binary diagrams do not show the limits of solid solubility of the silver-rich solutions below about 200° C. This work was undertaken in an attempt to extend these limits to the neighborhood of room temperature . PREPARATION OF ALLOYS All of the alloys were made with silver containing less than 0.014 pct (by weight) of impurities. The materials were weighed out into 225-g heats and melted in a high-frequency induction furnace. The indium, tin, and antimony alloys were melted in A1203 crucibles, under a boric anhydride cover, and were poured into split graphite finger molds. The aluminum, germanium, arsenic, lead, and bismuth alloys were melted in machined graphite crucibles; they were also covered with boric anhydride and poured into split graphite finger molds. The $-in.-diam ingots were heated to 750°C and were forged and hot-rolled down to 0.1 by 0.1 in. The wires were pickled in a 25 pct HNO3-75 pct H2O solution to remove any oxygen-rich surfaces. The wires were then annealed at 550°C for 2 hr in a dissociated ammonia atmosphere. They were then furnace-cooled for 20 hr to room temperature in this atmosphere. The wires were cold-drawn to 0.0808 in. diam. The finished wires were again annealed at 550°C in the same manner as in the first anneal. Thermoelectric Power. The thermoelectric power of a single specimen of each alloy was determined against pure silver which contained a maximum impurity content of 0.014 pct by weight. The wire specimens were straightened and then cleaned with ethyl alcohol. They were then reannealed in the same way as the finished wires to assure that any residual stress would be at a minimum level. Previous work has shown that the presence of small amounts of stress has the effect of decreasing the thermoelectric power. The alloy specimen was soldered to the pure silver wire to form the measuring junction. A standard set of copper leads was then soldered to the reference junctions of the thermocouple. These junctions were maintained in separate dewar flasks which contained finely shaved melting ice during the test. The thermal electromotive forces of the thermocouples were measured at four temperatures between 15° and 45°C. A known source of electromotive force was balanced against the output of the thermocouple until a null balance was reached. The data were then expressed in terms of the thermoelectric power at 30°C. The results were then converted to absolute thermoelectric power, s303.3 These data have an average error of less than ±0.2 pct. RESULTS AND DISCUSSION All of the experimental data are given in Table 11. Since the electromotive forces of the binary alloys of silver were determined against the pure silver from which they were made, the resultant thermoelectric powers are only a function of the intentionally added binary elements at the constant test temperatures. This provides a direct measure of the effects of the alloying elements. The absolute thermoelectric power of an alloy of silver is given4 by:

Jan 1, 1968

By Anthony Folger, Howard R. Lowe, J. F. Dougherty, E. G. Trostel, Joffre Meyer

The status of the natural gas industry in Alberta, Canada, is described with particular reference to the current extent of natural gas reserves and possibilities for additional development. Certain major fields are discussed as representative of the types of gas accumulations within various broad geographical divisions of the provinces. The estimation of the future performance of a gas reservoir is discussed as the basis for an estimate of the future availability of natural gas from presently known reserves. The future availability of the provincial reserves and the estimated future demand for gas within the province are described. INTRODUCTION This paper is a condensation of a detailed study of the natural gas reserves and the future availability of pipeline gas in the province of Alberta as prepared for Trans-Canada Pipe Lines Limited and presented in public hearings at Edmonton and Calgary before the Petroleum and Natural Gas Conservation Board of the Province of Alberta. The study began in October, 1950, and resulted in the preparation of five volumes of data at the expenditure of more than 20,000 man-hours. This paper is designed to afford a broad picture with detail limited to a type example of both natural ga-accumulation and future availability of gas supply. The province of Alberta has an area of 255.285 square miles which, for sake of comparison. is 8,359 square miles smaller than the state of Texas. Natural gas was first discovered in 1883 at the now abandoned Alderson well located some 20 miles southeast of the town of Princess. The first gas in commercial quantities was found at Medicine Hat in 1890. During the last 68 years. 187 localities have been discovered which are capable of gas production, and 73 per cent of these have been found since 1945. Sixty fields currently are producing gas, including 22 non-associated gas accumulations. Location of the oil and gas fields and prospects in the province of Alberta is shown in Fig. 1, together with a list of the localities of measurable gas, Fig. 1A. The estimated total provincial gas reserve as of Jan. 1, 1952, for the 104 fields estimated, is 11.7 trillion cu ft proved and probable, and for the 187 known areas capable of production is in excess of 16 trillion cu ft on a total proved, probable, and possible basis. Five fields (Pincher Creek, Leduc-Woodbend, Viking-Kinsella, Cessford and Medicine Hat) are estimated to have recoverable reserves of more than one trillion cu ft each. A sixth field, Turner Valley, was initially in this group, but its reserves have been depleted substantially. Twenty-four fields, of which the above mentioned six fields are a part, have estimated gas reserves (including the possible category) in excess of 100 billion cu ft. These 24 fields account for 79 per cent of the total provincial reserves. Comparative systemic analyses reflect that 56 per cant of Alberta's gas reserves are contained in sediments of Cretaceous age; 30 per cent in sediments of Mississippian age; 10 per cent in sediments of Devonian age; three per cent in sediments of Triassic age; and the remaining one per cent in Jurassic and Permo-Pennsylvanian sediments. It is expected that the relative importance of the Mississippian, Devonian, and Triassic sediments will be increased as exploration progresses. GENERAL GEOLOGY The western Canada basin comprises the sedimentary area between the Canadian Shield and the Rocky Mountain Front Range, the Arctic Ocean, and the International Boundary. The basin has an approximate area of 765,000 square miles and embraces parts of the provinces of Manitoba. Saskatchewan. Alberta, British Columbia and the Northwest Territories. Generalized columnar sections for the Province of Alberta are shown in Fig. 2. Substantially all of Alberta, except its northeast corner, has sedimentary cover. Sediments of all the geologic systems are represented. except those of Silurian age.

Jan 1, 1952

By Charles W. Carter, Alfred H. Bell

In 1943, Illinois produced 82,256,000 bbl. of oil, or 5.5 per cent of the total for the United States, and ranked sixth in the nation in oil production. This represents a decline of 23 per cent from 1942, when the total Illinois production was 106,ggo,o~~ bbl. and Illinois ranked fifth. The daily average production for 1943 was approximately 225,000 bbl. Daily averages by months were as follows: Jan......... 238,000 July......... 218,000 Feb......... 240,000 Aug......... 216,000 Mar......... 237,qoo Sept........ 220,ooo Apr......... 230,000 Oct......... 220,000 May....... 221,000 Nov......... 223,000 June......; . 222,000 Dec......... z18,ooo This shows that most of the decline during the year took place between March and May, and that for the last eight months of 1943 production has been essentially steady. This means that there has been enough production from new wells drilled to balance the natural decline of the Older wells. The trends of drilling and production are shown in Fig. I and Table 3.

Jan 1, 1944

By Alfred H. Bell, Charles W. Carter

In 1943, Illinois produced 82,256,000 bbl. of oil, or 5.5 per cent of the total for the United States, and ranked sixth in the nation in oil production. This represents a decline of 23 per cent from 1942, when the total Illinois production was 106,ggo,o~~ bbl. and Illinois ranked fifth. The daily average production for 1943 was approximately 225,000 bbl. Daily averages by months were as follows: Jan......... 238,000 July......... 218,000 Feb......... 240,000 Aug......... 216,000 Mar......... 237,qoo Sept........ 220,ooo Apr......... 230,000 Oct......... 220,000 May....... 221,000 Nov......... 223,000 June......; . 222,000 Dec......... z18,ooo This shows that most of the decline during the year took place between March and May, and that for the last eight months of 1943 production has been essentially steady. This means that there has been enough production from new wells drilled to balance the natural decline of the Older wells. The trends of drilling and production are shown in Fig. I and Table 3.

Jan 1, 1944

By Peter Soo

Pvestrained Ferrovac E iron has been neutron-irradiated at approximately 90°C to an integrated flux of 1020 nut (E > 0.82 mev]. The irradiation was found to produce an incveased temperature dependence of the flow stress in addition to a greatly increased athemal stress. Measurements of the flow stress and stress relaxation, from which the activation volume and activation energy for slip were deduced, show that neutron irradiation changes the rate -controlling slip process to one based on dislocation interactions with tetragonal distortions which are Produced around submicroscopic interstitial loops in the lattice. The study indicates that without prestraining prior to irradiation the chances of detecting a change in the rate -controlling slip process are greatly reduced because in the initial stages of slip a substantial fraction of the radiation defects are swept out of the slip plane by gliding dislocations. Thus, activation parameters which are subsequently measured are representative of a greatly reduced defect density and would not differ appreciably from those for unirradi-ated material. The large increase in the athermal component of the flow stress is probably connected with the presence of depleted zones in the lattice which are introduced by irradiation. ALTHOUGH fast neutron-irradiation has not been observed to markedly alter the activation parameters for slip in bcc metals,' small but significant changes do occur. Most experimenters agree that irradiation predominantly increases the athermal component of the yield stress.'-= In addition to this, Laidler and smidt7 have shown that in iron irradiated to 5 X 10" nvt and molybdenum irradiated to 10" nvt, changes occur in the activation volumes for slip. A similar conclusion has been reached by Milasin and Malkin8 for irradiated iron. Work by Ohr et a1.5 shows that for Ferrovac E iron, irradiated to 1.2 X 1016 nvt, small increases in the activation energy for slip also occur. So far these changes in the activation parameters have not been explained on a firm theoretical basis. One important factor which would minimize the chances of detecting a change in the slip mechanism upon irradiation is the presence of "channeling" which has been observed in molybdenum,9 niobium,10 and iron.11These channels are formed by gliding dislocations which sweep irradiation defects out of the active slip planes and thereby create zones in which continued dislocation motion is encouraged. The activation parameters for the dislocations gliding in the defect-free channels would, therefore, be similar to those for unirradiated iron and a change in the rate-controlling slip process would be difficult to detect. In the present work, an attempt has been made to reduce the effect of uneven deformation on the measured activation parameters for slip in neutron-irradiated Ferrovac E iron polycrystals, so that a more realistic assessment of the effects of neutron-irradiation could be made. Primarily, the experiments involve the irradiation of specimens which had been prestrained to 9 pct elongation at room temperature prior to insertion into the reactor. It was hoped that the introduction of a large number of evenly distributed dislocations would substantially decrease any channeling effect which might otherwise occur. MATERIAL AND EXPERIMENTAL PROCEDURE The starting material was vacuum-melted Ferrovac E iron, an analysis of which is given in Table I. The standard tensile specimen had a gage length of 1.125 in., a cross-sectional diameter of 0.120 in., and a re-crystallized grain size of 1.2 x 10-3 in. All tensile tests were conducted on a floor model "Instron" tensile machine at a strain rate of 3 x 10-4 per sec. The irradiation of the prestrained specimens was performed in the Brookhaven High Flux Beam Reactor to an integrated flux of 1020 nvt (E > 0.82 mev) at a temperature of about 90°C. All specimens were excap-sulated in high-purity aluminum sheaths which were lightly swaged around the samples to ensure good thermal contact. Subsequent measurements on the irradiated specimens showed that within experimental accuracy the swaging had not deformed them. EXPERIMENTAL RESULTS Fig. 1 shows the flow stresses for a series of unirradiated control samples. In order to produce a comparable dislocation substructure throughout the test sm range, all specimens were prestrained

Jan 1, 1970

By R. Maddin, S. K. Tung

SUCCESS of the dislocation theory in formulating the transitional lattice theory proposed by Har-greaves and Hill in 1929' is well established for low angle grain boundaries. The theoretical work of Burgersa and Read and Shockley,3 together with the experimental observations of Aust and Chalmers4 and Parker and colleagues,6 leaves little doubt as to the structure of grain boundaries with differences of orientations up to between 15" and 20". Beyond these angles, the structure of the boundary is not so clear, and is still a matter for conjecture. There have been notable experiments devised from which the data could be used to calculate energetics for possible arrangements of atoms in forming a large angle boundary.6 Most of these experiments deal with diffusion through and along the grain boundary. The recent work of Rhines and Cochart7 and Rhines, Bond, and Kissel18 was concerned with the relative movement of grains in aluminum bicrystals under constant tensile loads with their boundaries aligned at 45 " to the tension axis. The gliding along the grain boundary was cyclic and began after an incubation period. The velocity of gliding increased with the sum of the angular difference, 8, between the operative slip direction in the conjugate crystals and the angular difference between the active slip planes as measured between their traces upon the grain boundary. The initial gliding rate varied with temperature, and the logarithm of the average gliding taken over a considerable period was a linear function of the reciprocal of the absolute temperature: the slope gave an activation energy of 11,000 ±1,000 cal per mole. Since the rate of grain boundary shear is sensitive to the misorientation of the grains themselves, as shown by several workers,7,8 it is suggested that further work of this type might be fruitful in adding information regarding the behavior of boundaries under stress. The techniques devised by Chalmers" added impetus to the facility for observing grain boundary behavior, in that they provided a simple means for producing bicrystals of predetermined orientation so that the angle of the boundary could be controlled,

Jan 1, 1958

By Henry F. Heblby

HOW often has the thoughtful observer pondered the apparent contradictions experienced in the weather? One can take records of two days, one in the winter and one in the summer. The "degree days1' indicate that space heating and domestic load were present in one case and not in the other. The Business Index may be about the same, indicating that the industrial activity of the area and its concomitant use of fuel were about the same. Thus the volume of the products of combustion released to the atmosphere varied only as related to the space heating demand. Yet on one day in winter the atmosphere may be clear and bracing, while on a summer's day the air is thick and murky and the visibility sharply reduced. The situation may be reversed. What are some of the factors that contribute to the creation of these conditions? These few notes have been prepared to indicate some of the influences that are exerted on the problem. The Sources of Atmospheric PolLution The industrial area of Pittsburgh, Pa., has been a dominant center for the production of iron and steel for over one hundred years. In fact, with the growth of the numerous auxiliary processes Allegheny County which contains Pittsburgh is prob- ably the most industrialized county in the world. In addition, the type of manufacture carried out in this area is predominantly dependent on thermal energy (heat). That energy is supplied from coke and coal produced in the vicinity of Pittsburgh Indicative of the stupendous quantities of fuel that are employed in this industrial area's economy, the following (Table I) taken from the U. S. Census (1940) may be of interest. In tonnage consumed in the area, the figures are equally impressive: Annual Tons oF Coal Metallurgical Industries.... 35,000,000 to 40,000,000 Commercial Installations (Pgh.)................. 1,500,000 Domestic hand-fired) (Pgh.)................. 750,000 An influence that has never been fully appreciated by many individuals is the fact that no matter what adventures the gases of combustion experience as they pass through the various processes, uti-mately the spent gases are discharged through chimneys to the atmosphere.

Jan 1, 1949

An overland belt conveyor system installed at Simco-Peabody's mine near Coshocton, Ohio, is presently carrying coal three miles at an estimated cost of 4.499 per ton-mile. Installed by Link-Belt Co. in late 1961, this system transports coal from open pit and underground mining operations to the Conesville Power Plant. Simco-Peabody has mining operations over a considerable area just east of the Conesville Station. In 1960 the power plant completed plans to enlarge by adding a third boiler. As a result, Simco-Peabody was required to provide means to produce and handle more coal. The haulage equipment, which consisted of one 90-ton, five 60-ton and one 50-ton off- highway trucks, was too small to handle the increasing daily coal demands. Annual tonnage was approaching a million tons and in a few years would be well over that figure.

Jan 4, 1963

By Betty J. Laswell, Gerald W. Laswell

If recent trends in the rotary drill market are indicative of future surface mining operating practice, then the move to scaled-up mining equipment by manufacturers may soon be over. Of the 48 different rotary drills currently produced by 12 manufacturers, over 60% were introduced within the past five years. By far, the new drills have been in the "small" class, capable of producing up to a 229-mm-diam (9-in.) blasthole with 222 kN (50,000 lb) or less of down pressure. New rotary drills in the "large" class, capable of producing a 311-mm-diam (12 1/4-in.) blasthole with up to 423 kN (95,000 lb) down pressure, have also been prominent. In the super-size category, new drills producing blasthole sizes to 444-mm-diam (17 1/2-in.) with up to 578 kN (130,000 lb) have been minimal.

Jan 7, 1978

Section 89 Virginia State Geological Survey, Box 329, University, Va. Arthur Bevan, State Geologist A list of publications will be sent free upon request. Publica¬tions are distributed free to residents of Virginia, and others are asked to pay the cost of postage. Selected Bulletins available are: Bulletin 3-A, Geology of the titanium and apatite deposits, with chapters on the Lower Cretaceous and The economic geology (1913), 4, Physiography and geology of the Coastal Plain Prov-

Jan 1, 1933

By H. W. Paxton, G. M. Pound

A method is outlined for taking into account variation in chemical potential of both components in evaluating capillary effects at growing interfaces. The results are compared with experiment, and seem to be in reasonably good accord for Widman-statten ferrite growing in austenite. ENERY pointed out that during the steady-state growth of phases with a rather small radius of curvature at their advancing edge capillarity cannot be neglected. By proper application of the Laplace equation a correction must be made to the activity gradients down which diffusion occurs. Subsequent workers have concerned themselves with attempts to evaluate specific cases by the use and modification of the principles laid down by Zener.2-5 To solve the problem in its simplest form it is necessary to assume thermodynamic equilibrium at the interface and to select some criterion which will allocate the available free energy between reversible and irreversible processes. Zener chose to assume that the division should be made such that the new phase grew at the maximum rate. Other workers have used the same2,3 or different assumptions, e.g., maximum rate of free-energy dissipation,4 minimum rate of entropy production.5 Li6 has proposed that the "thermokinetic potential" should be a minimum at steady state. The purpose of this presentation is to note that most prior treatments have considered variations due to capillarity only in the chemical potential of the mobile constituent, and that a more consistent treatment must involve a consideration of the variation of chemical potentials of both solute -and sol- vent in a binary system.* As an example, the way in which this arises for ferrite growing from austenite may be illustrated by reference to Fig. l(a). The line OABC shows a typical variation of carbon activity with composition at one atmosphere pressure (at a transformation temperature below A3). In the tip of a growing ferrite plate with a hemi-cylindricab leading edge of radius ?, the pressure due to capillarity is*

Jan 1, 1963

By H. M. Stewart, R. A. Grange

MANY steel parts may crack if quenched directly into a bath near room temperature, but not if quenched at a temperature just above the range where martensite forms and then allowed to cool slowly to room temperature. This latter procedure, which is the basis for such modern hardening techniques as "martempering " and "isothermal quenching," may entail some sacrifice in depth of hardening but very little, if any, in intensity of hardening. In planning such treatments, it is necessary to know the upper limit of the martensite range, and often desirable to know the proportion of martensite that would form on cooling to any lower temperature; furthermore, the tendency of a particular steel to crack when quenched is unquestionably associated with the temperature range of martensite formation, and consequently knowledge of this range aids in selecting the optimum composition for a given application. Certain puzzling phenomena associated with the properties of quenched and tempered steel may be at least partly clarified as the manner in which martensite forms is more fully under- stood. Information on the temperature range of martensite formation, particularly with respect to how much martensite results from quenching to a given temperature, is lacking for most commercial types of carbon and low-alloy steel. These considerations led us to study martensite formation in 14 carbon and low-alloy steels. The resultant data may be directly used in the following ways: (I) for selecting the lowest quenching temperature at which no martensite will form; (2) for selecting the highest quenching temperature at which virtually dl marten- site will form, thereby avoiding quenching to an unnecessarily lower temperature with attendant danger of cracking; and (3) in producing a mixture of tempered marten- site and bainite, which in high-carbon steels has been found to possess somewhat better ductility than tempered martensite, yet does not require the full transformation time necessary for a completely bainitic (austempered) structure. PART I. OBSERVATIONS OF MARTEN- SITE FORMATION IN FOURTEEN CARBON AND LOW-ALLOY STEELS Transformation of austenite to pearlite or bainite can be conveniently studied by observing the change that occurs over a period of time at constant temperature; such studies are the basis of the isothermal transformation diagram (S-curve). This isothermal technique is not applicable to martensite formation, which occurs within a time interval too small to measure, at least by any ordinary means. For all practical purposes, therefore, martensite may be regarded as forming only during cooling and not during a period of time at constant temperature. As austenite is cooled below

Jan 1, 1946

Use of rock grinding media in a mill at Tennessee Copper Corp. was mentioned in the MINING ENGINEERING Annual Review. (February 1953, page 158). Because interest in use of self-grinding media continues high we asked F. M. Lewis, Superintendent of Concentration at Tennessee Copper, to supply more details on this trial, and of plans to expand use of rock media in their mills that grind marble. Here is what he reports.

Jan 5, 1953

By D. W. Philips

The problem of strata control has of necessity been prominent in mining, and accounts of individual experience and research abound in the literature of most mining countries. Organized rescarch began in Britain by the formation of a committee, upon the recommendation of the Safety in Mines Research Board in 1923, to investigate methods of reducing accidents from falls of roof in coal mines. This committee examined current practice in supporting underground workings in the principal coal fields, and its findings have been published in the Board's publications.' - Toward the end of these investigations it was suggested by the Chief Inspector of Mines that committees of the several mining institutes be formed to examine the problem in their respective districts. The formation of these committees marked a new phase in research on strata control. The work, though being done in the separate coal fields, followed a scheme outlined by the chief Mining Engineer of the Research Board, and was coordinated by his office. FACTORS INVOLVED The subject is being considered in Britain from two aspects: 1. To provide. by supports, means to prevent falls of fractured ground. 2. TO develop methods whereby the strata can be maintained in the least broken condition and thus make falls less likely. The first aspect is the one that will most likely lead to immediate results from the accident standpoint. It depends largely upon the assimilation of already acquired knowledge regarding the properties of supports and their correct application. The second aspect is perhaps more fundamental, and involves also the properties of the strata and their behavior under the influence of the forces induced by mining. The problem involves many natural factors that cannot be controlled, such as depth, inclination and thickness of seam and nature of the rocks. Other factors, which may be considered to a certain extent controllable, cannot be varied readily and with sufficient frequency to facilitate easy investigation; some of these are: rate of advance of the working face, length of face, direction of the face with regard to cleat and inclination, system and arrangements of rock packing behind longwall faces. In any given case the very many factors present have a mutual influence upon the effects produced in the mine. For example, a study of the effects of rate of advance cannot be done without considering the effects of other factors such as nature of strata, direction of face and quality and arrangement of supports. Conversely, the length and direction of a working face

Jan 1, 1947

By D. W. Philips

The problem of strata control has of necessity been prominent in mining, and accounts of individual experience and research abound in the literature of most mining countries. Organized rescarch began in Britain by the formation of a committee, upon the recommendation of the Safety in Mines Research Board in 1923, to investigate methods of reducing accidents from falls of roof in coal mines. This committee examined current practice in supporting underground workings in the principal coal fields, and its findings have been published in the Board's publications.' - Toward the end of these investigations it was suggested by the Chief Inspector of Mines that committees of the several mining institutes be formed to examine the problem in their respective districts. The formation of these committees marked a new phase in research on strata control. The work, though being done in the separate coal fields, followed a scheme outlined by the chief Mining Engineer of the Research Board, and was coordinated by his office. FACTORS INVOLVED The subject is being considered in Britain from two aspects: 1. To provide. by supports, means to prevent falls of fractured ground. 2. TO develop methods whereby the strata can be maintained in the least broken condition and thus make falls less likely. The first aspect is the one that will most likely lead to immediate results from the accident standpoint. It depends largely upon the assimilation of already acquired knowledge regarding the properties of supports and their correct application. The second aspect is perhaps more fundamental, and involves also the properties of the strata and their behavior under the influence of the forces induced by mining. The problem involves many natural factors that cannot be controlled, such as depth, inclination and thickness of seam and nature of the rocks. Other factors, which may be considered to a certain extent controllable, cannot be varied readily and with sufficient frequency to facilitate easy investigation; some of these are: rate of advance of the working face, length of face, direction of the face with regard to cleat and inclination, system and arrangements of rock packing behind longwall faces. In any given case the very many factors present have a mutual influence upon the effects produced in the mine. For example, a study of the effects of rate of advance cannot be done without considering the effects of other factors such as nature of strata, direction of face and quality and arrangement of supports. Conversely, the length and direction of a working face

Jan 1, 1947