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By R. F. Mehl, A. H. Geisler, S. Barrett

The studies of the mechanism of pre= cipitation and of the resulting property changes in aluminum-silver alloysl-3 have presented some new concepts of the aging reactioxl—concepts that may be fundamental in establishing a complete quantitative theory of age-hardening. With both aluminum-copper and aluminum-silver alloys, thin platelike aggregates form parallel to the Widmanstätten planes of precipitation.l,4 These platelets grow in lateral dimensions and in thickness with aging time until they arc thick enough to produce an X-ray diffraction line pattern. Their structure is that of a transition lattice which is coherent with the matrix, since the atomic spacings in the matrix and the precipitate are the same on each side of their common interface.2,4 The equilibrium precipitate forms later from and at the expense of the transition lattice. Since age-hardening occurs during the formation and growth of the transition lattice, the major contributor to the hardening no doubt is the stress condition in the matrix resulting from the matrix holding the precipitate in the coherent condition. The development of these stresses also appears to be responsible for an increase in the electrical resistance superimposed on the normal decrease resulting from a change in the concentration of the matrix during aging.3 The two consecutive reactions constituting the aging process are accompanied by characteristic microstructural alterations. The initial precipitation process results in the formation of a Widmanstatten figure, while the later transformation of the transition lattice to the equilibrium lattice is accompanied by a coalescence, in the case of aluminum-copper alloys,5 and by the appearance of light areas at the grain boundaries with aluminum-silver alloys showing a structural rearrangement of matrix and precipitate.3 This latter reaction is similar microscopically to the so-called "discontinuoils precipitation." Possibly discontinuous precipitation is a process that often if not always follows true precipitation of a coherent lattice and during which the transformation of the coherent transition lattice to the equilibrium lattice takes place accompanied by matrix recrystallization.3 Expermental Procedure The alloys were made using 99.97 per cent A1 or distilled magnesium, with

Jan 1, 1943

By William C. Marshall, Frank G. Norris

The term "total operation" is meant to include problems that cannot be answered from the standpoint of either the blast furnace or the open hearth separately but must be studied by considering the interrelations of these two processes. There are other ways of expressing this idea, such as reference to the blast furnace and the open hearth as an integrated process or by emphasizing the interrelation and interaction of the two processes. Much progress has been made in metallurgy and other fields by breaking complicated processes and reactions into simpler parts and studying each of these intensively. This intensive study frequently is done under the controlled conditions of the laboratory experiment. The entire process is understood better by this specialized study of each of its parts. This procedure is so satisfactory that an understanding of unit operations is a fundamental requirement of chemical engineering. Much discussion of the open-hearth process is in terms of one heat or one furnace. By this is meant that the conclusions apply to one furnace, wherever it may be. Furnaces seldom occur singly; they are located in groups and these groups are located in steel plants having characteristic blast-furnace equipment. Problems that are affected by the number of furnaces operating, by the number of blast furnaces in the plant and by the fact that the open- hearth shop is dependent on the bla furnace capacity rather than on its o needs for the amount of iron available among those which, in contrast to "u operations," we have chosen to call "to operations." Many of these problems, such as cha ing delays and the general mechani problem of material handling, are familiar that merely to define " total op ations" brings them to mind. These pr lems are of such importance that alrea they have received careful thought 2 study and probably will merit furt study. As will be shown later, these mechan problems are so intimately related metallurgical problems of total operati that the effect of certain changes cannot ascribed with certainty to either a mech ical or a metallurgical cause entirely. Although the problems coming under general term of "railroading" are inclu in the problems of total operations, ' others are selected for the discussion of paper, One of these is strictly a problem composition; the other is strictly a prob of tonnage production. The problem of phosphorus is pres whenever basic open-hearth slag is used the blast-furnace burden. This practice not secured universal acceptance chi because of difference in preference for h manganese or low-manganese pig iron hjgh-manganese (2.00 per cent) iron is to made, open-hearth slag as a source manganese is usually cheaper than m

Jan 1, 1943

By C. A. Zapfee, C. E. Sims

An investigation of the behavior of inclusions in steel several years ago1 led to the conclusion that some of the commonly occurring inclusions in steel have appreciable solubilities, particularly in liquid steel. In the belief that further study and clarification of this matter was warranted, a laboratory study of oxides in liquid steel was started. These oxides are generally the result of deoxidation treatment, and the basis of an understanding of their behavior must be, therefore, the behavior of the deoxidizer in liquid iron. The Fe-Si-O system was selected for the first study, and the apparatus used and experiments conducted are described herein. Apparatus The apparatus is shown in Fig. r and the system is shown by diagram in Fig. 2. Furnace, A lmosphere Commercial hydrogen (1) passes through an orifice (2) into a manometric system that measures the tankside pressure (3) and the back pressure (4) in the system. A water trap (5) guards against excess tankside pressure. A by-pass with stopcocks (6 and 7) is provided, so that the hydrogen can be routed directly from the tank to the furnace if desired. When stopcock 7 is closed and stopcock 6 is open, the gas proceeds through the conditioning train, of which the first unit is a furnace (8) that contains platinized asbestos at 350°C. The temperature is measured by a thermocouple and potentiometer (9) and is controlled by a slidewire resistance (10). In this furnace fres oxygen is converted to water vapor. The exiting gas passes over a water bath (11) kept slightly below boiling temperature by an auxiliary heating unit (12). This unit also heats a surrounding copper coil (13) containing water, and the heated water rises through a collar (14)

Jan 1, 1943

By J. E. Tobey, David R. Mitchell, J. H. Kerrick

DETAILED knowledge of purchase specifications established by coal consumers is essential to the successful design and operation of a coal-preparation plant. ANTHRACITE Specifications should be considered by both the consumer and the producer as guide posts outlining a certain path for both to follow. Plants differ, therefore specifications must differ to meet the varied requirements. Specifications are not of themselves a "cure all" or an assurance of complete satisfaction in fuel utilization. Specifications should not be regarded as a license to engage in an orgy of buying any and all coals that may happen to fall within their limits. This would lead to the-indiscriminate mixing of coals which may vary in their burning characteristics. Different coals of equal grade tend to be individualistic in their burning characteristics. Rather, specifications should be used to help simplify coal selection, to reduce the actual number of coals used over a given period; in other words, to have a stabilizing influence on coal or customer turnover. In the final analysis, the use of too many coals per year in a plant is costly to both the consumer and the producer. Too many sources usually result in higher operating and maintenance costs for the consumer and higher sales costs for the producer. Finally, the statement included in the report accompanying the comprehensive Coal Selection Charts prepared by the Coal Committee of the National Association of Purchasing Agents, and released in 1938, is significant. This Committee worked diligently for a period of 15 years seeking to find a scientific and reliable method for selecting coals. The two following paragraphs are quoted from its report: More important is the fact that no ready-made classification or set of specifications can possibly replace the judgment and resourcefulness of an experienced combustion engineer, or fuel technologist, nor the usual need for full scale plant tests under the exact conditions of use before a final decision is made . . .

Jan 1, 1943

By Richard Zinszer

Application of electric logs has been used in correlation of subsurface structure to determine the size and shape of the oil reservoir. Such a knowledge is hardly complete until saturation and productivity are determined for the various horizons. It is difficult to use electric logs successfully for this purpose because of the many factors that influence the curves. In this work an effort was made to establish an empirical correlation between formation resistivity for a series of electric-log curves and water saturation and oil productivity of sand. Electric logs were obtained by recording with 10 different electrode spacings through the same interval of a well. In the analysis of these curves all factors except two, a dependent and independent variable, were held constant. The interval studied had been cored and a large number of samples were analyzed in the core laboratory in order to compare the values of permeability and saturation with the measured values of formation resistivity. Results of this analysis indicate: (1) the depth to which mud filtrate enters a sand body, (2) a correlation between permeability and sand resistivity for shallow penetration depths, and (3) that the water saturation for an oil sand can be determined from the measured sand resistivity after making suitable correc- tions for sand thickness. The proceduer in the last method depends on a correction for thickness factor and a theoretical curve. The accuracy of the theoretical curve is now being tested in the laboratory. In an effort to place the analysis of electric logs on a quantitative basis, there is need for a better understanding of the many factors that influence an electric-log curve. These factors may be large differences in sand thickness, permeability of the sand, salinity of the interstitial water, mud resistivity, formation temperature, and other sources. A number of examples were presented by Archie,' which treat the effect of sand thickness on measured resistivity. He compared the true resistivity of a sand with the observed resistivity for sands 8 ft., 16 ft., and 24 ft. thick, and found the observed resistivity Of the 8-ft. sand to be approximately

Jan 1, 1943

By Oliver Bowles

[The inorganic nonmetallics - that is, all minerals aid their primary products except metallic ores and fuels - have an important place in industrial life of any country. They are essential to a multitude of products and processes, and their development is closely related to general industrial activity. Several are classed as strategic, and many others are performing necessary functions in the military program. It may be of interest therefore to trace their history over a period of years and to correlate their progress with the circumstances and events that are shaping national]

Jan 1, 1943

By H. R. Stahl

The disseminated lead district of Southeast Missouri lies 70 miles south of St. Louis. The only metal of economic importance in the ore is lead, but minor amounts occur of iron, zinc, copper, cobalt, nickel, silver and cadmium. These minor metals, as might be expected, tend to concentrate in both the flotation and table middlings. In the past, some zinc has been recovered by differential flotation. The silver and cadmium tend to associate with the zinc, and some recovery is made of these two metals at the smelter. The lead occurs as galena, or lead sulphide. The minor metals are also present as sulphides. The presence of oxidized lead is suspected, but has not been definitely proved. The gangue is chiefly dolomitic limestone, with small amounts of sandstone and shaly glauconitic and chloritic minerals. The ore contains about 3.25 per cent lead, occurring as galena disseminated through the gangue. Some of the galena is very finely disseminated, and the mineral in the gravity tailings, or chat; is seldom or never in the free state. The method of treatment of the ore has been evolved over a period of 75 years; hence probably is not far from correct. The milling processes have tended toward simplification during the past 15 years, but recoveries have never been sacrificed for the sake of simplicity. In many cases, simplification of flowsheets has led to better recoveries and operating economies. A simplified flowsheet is shown in Fig. I. The St. Joseph Lead Co. operates four mills in the Flat River district, with a normal total capacity of about 21,000 tons per day, divided as follows: Federal mill, 11,000 tons; Leadwood mill, 4500 tons; Desloge mill, 3400 tons and Bonne Terre mill 2400 tons. The methods of concentration used at these plants are similar in principle; they differ mainly in details and in the type and size of the equipment used. The process of concentration may be divided into five main steps; i.e., dry crushing, wet grinding, classification with its attendant desliming, tabling and flotation. A brief description of these processes will be given, noting important differences in the various plants, and also noting the more important changes or developments of the past few years. Dry Crushing The run-of-mine ore is hoisted in skips, the capacity of these skips ranging from 23/4 tons to 81/4 tons. At the Desloge plant, the ore is hoisted in 2-ton mine cars on self-dumping cages. All ore is hoisted at shafts adjacent to the various crushing plants, no ore being transported on the surface. Primary breaking at all the mills is accomplished with 9E Telsmith breakers. Preliminary screening is provided ahead of most of these crushers, either by station-

Jan 1, 1943

By Cyril Stanley Smith

BeTa brass (consisting of approximately equal atomic proportions of copper and zinc) exists as a random solid solution at high temperatures, hut at low temperature< an ordered structure is stable, with the copper and zinc atoms occupying alternate sites on the body-centered-cubic lattice. On cooling, ordering commences at a temperature of 450° to 470°C., depending on the composition. The degree of ordering progressively increases at lower temperatures until it becomes virtually complete at about 100°C. The electrical resistivity of the alloy illustrates the changes clearly (Fig. I). This type of reaction has been a favored subject for study by physicists. An excellent summary of the theory is to be found in a paper by F. C. Nix and W. Shock1ey.l All published data on electrical conductivity, specific heat and other properties agree in indicating that the ordering reaction in beta brass takes place so rapidly that it cannot be prevented or even retarded by quenching&apos; With most ordered alloys, cold-working induces disorder and

Jan 1, 1943

By William H. Spice

The year 1942 in the South Central Texas area was marked by a sharp curtailment of exploratory drilling as compared with the past several years. In the 33 counties that compose this district, 17 of which are nonproducing counties, only 51 exploratory wells were drilled during the year 1942. This compares with 118 exploratory wells drilled during 1941, or a decrease of more than 50 per cent. At the end of the year 10 active exploratory wells were drilling in this area, as against 19 being drilled at the end of 1941. Of the exploratory wells drilled, two brought in oil wells and were new field discoveries and one was a gas well extending a recently discovered shallow gas area in the western part of the district. This compares with five new oil fields, one new . gas field and two extension wells drilled in 1941. Both new field discoveries were small and in areas outside of the general trend of the main producing horizon of the district in Edwards limestone: One new field, the Imogene, in Atascosa County, is a deep Edwards limestone prospect at 7500 ft., and the other new field, the Poth, in Wilson County, is a sSEa110w Wilcox (Eocene) prospect at 4000 ft. Subsequent drilling in each field to the end of I942 has proved disappointing. There were no new discoveries along the old Balcones fault-line trend, although 35 of the exploratory wells were drilled in counties along this trend. Approximately 38 wells were drilled in or adjacent to the proven fields of the district, of which 18 were oil wells, 2 were gas wells and 17 were dry holes. The district produced 6,186,178 bbl. of oil during 1942, which was a 7 per cent decrease under production for 1941. Approximately 4,961,000 bbl. of this total production, a slight increase over 1941, was produced by the four Edwards-limestone fields, Luling, Branyon, Salt Flat and Darst Creek, and the rest of the production came from the other 42 active fields in the district. During the year, 20 new producing wells were completed and 221 wells were abandoned in the producing fields. This alarming excess rate of abandonment~ over completions will be further reflected undoubtedly by a further decreased rate of 1943 production under 1942. Two active fields in the district in which more than one producing well was completed during the year were Bee Creek and Washburn. The majority of exploratory work in the district was confined to areas along the Wilcox trend, with a certain amount in progress along the deeper Edwards limestone trend. The successful completion of sevemi wells in the Washburn field from multiple sands in the Lower Wilcor (Eocene) has stimulated exploratory work along this trend, while the completion of a small well in the Imogene field from the Edwards limestone at 7500 ft. has renewed interest in this horizon at depths greater than generally are producing in the district. New Fields ounty. ble Oil and Refining Company&apos;s No. I

Jan 1, 1943

By Charles C. Rodd

Prior to 1938, proration procedure in Kansas required the physical testing of wells in order to set up a basis for allocating production. Subsequently the use of liquid-level data and bottom-hole pressure data was authorized on certain types of wells as a basis for calculating well capacities, thereby permitting wells to be tested at low rates and with small volumes of production. This paper gives some attention to the equipment used for obtaining liquid-level data but in general it is devoted to the theoretical and physical factors involved in well testing by drawdown methods. These tests are divided into two classifications: (I) liquid-level data used directly to calculate capacities, and (2) liquid-level data and liquid-level measuring equipment used in connection with other data to determine bottom-hole pressure. Equations and calculations for both types are shown. Well capacities calculated from fill-up data have not been used generally but offer a simple means of testing some wells. Theoretical factors and calculations for such tests are shown. In the state of Kansas, proration laws required that the "ability of a well to produce" be given consideration in state allocation orders and for many years this was the only factor used in prorating the allowed oil. The "ability of a well to produce", was the quantity of oil that could be obtained from a well in a prescribed period, usually 24 hr. Early in the history of State-regulated proration, Kansas operators realized that, unless some restriction were placed upon equip- ment, the competition between producers to obtain large well "potentials" might result in a race to install the largest pumping equipment. Consequently, restrictions were placed upon the size of tubing and length of pump stroke that could be used in pumping wells during potential tests. Later, restrictions were placed also upon the size of tubing and chokes that could be used in flowing walls. Despite the restriction setup, better pumping equipment was designed and installed, pumps were improved, and various devices were invoked to obtain high rates of production for short periods of time. By 1937 pumping cycles of forty to forty-five 54-in. strokes per minute were not uncommon, and numerous wells had produced at the rate of 3500 bbl. per day for short periods. Such production was far beyond any rate that could be long sustained. Equipment necessary to take "potentials" was several times larger than that needed for normal producing purposes, and repairs and replacements required by the high pumping speeds were excessive. Also, many operators suspected that the high rates of production main tained during &apos;"potential" tests were conducivc to early water encroachment. By 1938 large-scale physical testing of wells in Kansas ended, the use of the bottom-hole pressure gauge had become common, engineers and operators were becoming familiar with the term &apos;&apos;productivity index," and bottom-hole pressure was being used as a factor in allocation in many areas. There were many drawbacks, however, to large-scale use of

Jan 1, 1943

By J. F. Barkley

During the present war emergency, under the urge of the Federal Government to store coal, the following questions are frequently asked by coal users: (a) Will the coal lose any, of its heating value in storage? (b) Will it slack and give a smaller-size coal? (c) Will its burning characteristics change in any way? (d) Will it catch fire from spontaneous combustion? (e) What precautions should be taken when coal is stored? DISCUSSION (a) Loss of Heating Value Studies by the Bureau of Mines show that the loss of heating value of coal in storage commonly has been overestimated. Various types of storage tests were made on New River, Pocahontas, Pittsburgh gas, and Sheridan (Wyo.) coals. The following is quoted from Bureau of Mines Bulletin 136, Deterioration in the Heating Value of Coal During Storage, by H. C. Porter and F. K. Ovitz (p. 8):

Jan 1, 1943

By Gregoire Gutzeit

The development reported in this paper was begun by the author a number of years ago, while he was a lecturer on complex chemistry and metallurgy at the University of Geneva, Switzerland, and in charge of that institution&apos;s research laboratory. Completion of the development and reduction to practice did not occur until last year at the Westport mill, laboratories and testing plant of the Dorr Company, where this method is now in general use for identifying and localizing the mineral constituents of both metallic and nonmetallic ores. It has proved to be a practical tool of the metallurgical staff at the Westport mill, devising unusual milling flowsheets for complex and refractory ore bodies. In a number of instances the findings have been successfully used as fundamental factors in the design and specification of complete metallurgical plants. Seven examples of the use of this method in solving practical milling problems are included in this paper. General Outline The microscopic study of an ore, at first only of scientific interest, has proved extremely useful both in practical geology and in ore dressing. The binocular magnifying lenses for rough observation of the products of an ore-dressing plant have been in use for a long time; but only within the last few years has a systematic microscopical examination of ore samples become a normal tool of any research laboratory dealing with ore-dressing problems. Such an investigation avoids considerable loss of time as well as empirical trials and useless experimentation. It will generally indicate the correct grinding and often will suggest the proper method of treatment. . The petrographic determination of transparent minerals in thin sections, or even in grains, has been perfected, and very accurate methods have been devised to meet any requirement, such as Feodorof&apos;s rotating stage on the petrographic microscope. Almost all transparent minerals can be positively identified by their optical properties; i.e., isotropism, anisotropism, color, pleochroism, refractory index, cleavage, crystal form, birefringence, and others. The identification of opaque minerals is a much more difficult problem and can be done only by using polished specimens. Unfortunately, most of the valuable metallic ores, and even some of the nonmetallic ones, are not transparent; therefore it has been necessary to develop a special technique for the determination of these minerals. Some optical properties—for instance, isotropism, anisotropism, color, cleavage, reflecting power-—are often adequate in roughly classifying the mineral. Only "reflecting power" is a measurable value, provided special photometric equipment (ocular photometer or Orcel&apos;s photoelectric cell) is available. The other optical properties mentioned are more or less relative,

Jan 1, 1943

By John A. Johnson

"INTRODUCTION The use of wet drilling with adequate ventilation has largely controlled production of dust in drilling rock; however, in some operations, such as shaft sinking and modern tunnel driving, when each of a number of drills is operating in a small cross-sectional area, it is at times difficult to ventilate well enough to keep the dust concentration within desired limits.Some chemical compounds, known as wetting agents, when added to water in small quantities reduce the interfacial tension and make it possible for the solution to wet dust particles more effectively than water alone.This report presents results of tests on the effectiveness of two wetting solutions in reducing the amount of dust produced by wet drilling in basalt.ACKNOWLEDGMENTSThe tests were conducted at the Bureau's Mount Weather Testing Adit, Mount Weathe, Va. The author acknowledges the assistance and cooperation of Wing G. Agnew, superintendent; Marvin M. Reveille, mining-ngineering aide; and the rest of the crew at Mount Weather in conducting the tests. C. W. Owings, mining engineer, Safety Division, assisted in conducting some of the first tests and gave valuable advice and guidance throughout the work and in preparing this report."

Jan 1, 1943

By Finney, W. R.

MUCH has been said and written of the "Big Inch," of the terrific obstacles encountered in its construction, of the colorful and tough men engaged in its building, but little has been publicized of the engineering and economic problems behind the scenes. Long before Pearl Harbor it was apparent to the petroleum industry that a critical oil shortage could be expected along the Atlantic seaboard, owing to delay in tanker deliveries as a result of convoy movements, and to allocation of vessels for foreign shipments. This area, with a normal consumption of approximately 1,800,000 barrels per day of oil and products, was almost entirely supplied by tanker. Pipe lines supplied an average of only 20,000 barrels per day in 1939, 40,300 barrels per day in 1940, and 55,000 barrels per day in 1941. A small amount of oil and products was also delivered via barge.

Jan 1, 1943

By Clare B. Carlson, C. P. Proctor

THE history of the froth flotation of coal is relatively short. The flotation process was applied to fine-coal cleaning about the time of the end of World War I. Coal flotation finds more widespread use in Europe than in the United States and is used on a commercial scale in nearly all major coal-producing countries in the world. In Fig. 1 the general arrangement of a froth-flotation plant at a British colliery is shown. GENERAL FEATIJIEES OF THE PROCESS Application The flotation process is applicable to the cleaning of the fine sizes, particularly minus 48-mesh coal, although it may be used on sizes as coarse as 1/8 in. Since most cleaning processes usually are not effective on sizes smaller than 48-mesh and certainly not effective on minus 100- mesh, the froth-flotation process offers a solution to the problem of cleaning these sizes. This process consists-of agitating the feed pulp with a small amount of reagents, usually 1.0 to 2 ½ lb. per ton of feed in the presence of water and air; the reagents help to form small bubbles that collect on the particles having a greater affinity for the bubble surface than for the water surface, in this case the fine coal, and the bubbles buoy these particles to the surface to form the frothor concentrate. Slate and shale particles remain wetted and suspended in the water to be drawn off as tailing. The frothers commonly used in coal flotation are cresylic acid, pine oil, and alcohols. More expensive frothers, used in ore flotation, work satisfactorily but do not compare with these cheaper reagents for over-all cost. Collectors- used are low-grade petroleum fractions, such as cheap, partly refined fuel oil, or lubricating oil, sometimes mixed with small amounts of kerosene. Other collectors used are the fatty acids and their

Jan 1, 1943

By Edward C. J. Urban

ESSENTIAL requirements for ensuring safe working atmospheres in underground metal mines are planned systems of ventilation and provision for effective distribution of sufficient volumes of air by auxiliary equipment. Investigators1 in the past have suggested that quantities of air supply ranging from 300 to 800 cu. ft. of air per minute per man underground are necessary, to establish adequate general ventilation. These fundamentals are just as important as the use of water in dust suppression, control of blasting, the use of personal protective equipment, frequent inspection of working areas and education of employees in good dust-prevention practice. During the past two years the necessity for direct control of the underground working environment has become particularly urgent. The increase in production rate, with two-shift and three-shift operation replacing the single shift, has complicated the problem of dealing with excessive concentrations of blasting fumes and gases, carbon dioxide and monoxide, heat and oxygen deficiency. Although previous industrial hygiene programs had given consideration to these factors, they were generally regarded by mine operators as secondary to the control of dust hazards. Today, blasting smoke in a mining area means delayed production because the miner cannot return to his work place after a short interval. Smoke on the haulage level means a safety hazard and exposure of the underground employees to excessive concentrations of atmospheric contaminants. Exposure to the moderately excessive concentrations of carbon dioxide and monoxide found in metal mines has caused physiological disturbances and a decreased capacity for work; deficiency of oxygen, in some cases to as low as 3 per cent, has resulted in fatalities. During the past 10 years the Saranac Laboratory2 has been associated with the iron mines in the Upper Peninsula of Michigan and Wisconsin in developing and maintaining an industrial hygiene and silicosis-prevention program. At present, about 35 underground iron-ore mines are operated full time in this area. With two exceptions, all of them are ventilated by main fan installations installed either on surface or underground. ,The types of mining used in these mines may be classified either as sublevel cave, radial top slice or sublevel stope, and the procedures commonly employed in the ventilation of these three types are described in Figs. 1 and 2. A number of different methods of mine ventilation had been in use in this area when the study was started. Natural ventilation had proved unsatisfactory. The wide variation between low air volumes during the summer months and higher volumes during winter led to unpredictable conditions that were difficult to control. In the majority of the mines two separate shafts or openings to surface are utilized in

Jan 1, 1943

By C. H. Mathewson, P. W. Bakararian

The greatcr part of the literature on the plastic behavior of magnesium dates back to that active period of research in crystal mechanics immediately following the widespread preparation of isolated metallic crystals large enough for the application of conventional methods of mechanical testing. These investigations, performed on single crystals, revealed an analogy between zinc and magnesium with respect to their fundamental mode of deformation. in the operation of glide and twinning, respectively, on crystallographically similar planes. Mathewson and Phillips (1928)&apos; by geometrical analysis identified the plane in magnesium as the twinning plane. Schiebold and Siebel (1931) confirmed this twinning planc, established the basal plane as the plane of slip, and a digonal axis I as the slip direction. They also rcported twin formation in a secondary role on the {IOI} plane. Schmid (1931)³ summarized and discussed the earlier evidence and presented the results of his own experiments on the effect of temperature and small amounts of soluble elements. From X-ray studies on extended wire single crystals, he concluded that slip along the basal plane in the direction of the digonal axis I closest to the stress direction was the sole slip system operating at atmospheric temperature. This conclusion was based on experiments with crystals of many different orientations relative to the stress axis. Special attention was directed to the basal plane and the digonal axis I, as the plane and direction of greatest atomic density. Determinations of resolved shear stress at the onset of plastic yielding-—i.e., the critical resolved shear stress—were also made; the average of these calculations showing 82.9 grams per sq. mm. This value varied only slightly up to 300°C. at which temperature it was found to decrease to 70.5 grams per sq. mm. The extension of his crystals at temperatures above 225°C. further disclosed the presence of new slip systems. After the origince specimens of circular section had been

Jan 1, 1943

By Lawrence K. Jetter, Robert F. Mehl

Some advances have been made recently in the theory of the kinetics of precipitation from metallic solid solution despite the complexities of the problem, but there is surprisingly little quantitative information available on rates of precipitation with which to test present theory or upon which to build new theory. Attempts to measure rates of precipitation have been beset with difficulties which originate both in the anomalies that attend the changes in the properties selectcd for measurement, as, for example, in electrical conductivity or mechanical properties, and also in the complexities in the structural changes in some systems, as in the aluminum-copper system. If the functional relationship between the quantity of precipitate and the value of the selected property is uncertain, measurements of that property are obviously of uncertain utility in determining absolute rates of precipitation. If the precipitating system passes through one or more transition stages, the interpretation of measured rates lacks definiteness; in such cases, it is necessary to measure the rate of reaction in each separate stage, if the rate measurements are to have any significance from the kinetic point of view.* These difficulties cannot be wholly avoided, for at least in some measure they are characteristic of the process of precipitation from solid solution, but they can be minimized both by the selection of a simple system and by the use of a method of measurement relatively free from anomalous behavior. The present paper reports dilatome tric measurements on the rate of precipitation of silicon from the aluminum-rich solid solution in the aluminum-silicon system—a study that approaches the desiderata of simplicity. The aluminum-silicon system offers advantages from these points of view: there are no known anomalies in the property changes accompanying precipitation; there are no known transition stages; the precipitate is an element, not a compound, and both matrix and precipitate are cubic, and while the structures are not identical (the solid solution is face-centered cubic and the precipitate is diamond cubic), the system at least approaches the ideal case of a crystal precipitating from a matrix of the same crystal type—the ideal case which Becker6 assumed in treating the precipitation process theoretically. The dilatometric method, while not free from disturbing effects, as the subsequent dis-

Jan 1, 1943

By Wilford S. Wright

FOR the past four years the management of the Black Hawk Consolidated Mines plant at Mogollon has conscientiously kept accurate records pertaining to cost of operation and the performance of certain equipment. These records have been valuable in coordinating the work in the mine, mill and power plant. Also, as to quantity and kind of equipment and supplies most suitable from the standpoint of economy and dependable operation, they have served as a guide. Through comparison with records at other mines, where the same things are being done in a different way, they have pointed out mistakes to be avoided. No outstanding accomplishments, either in costs or performances, are revealed; in fact, some of the results are perhaps quite inferior to those obtained at similar plants, but it is with the thought that more records should be published for the benefit of the mining profession that the author presents these data. To other operators and to mining engineers who are called upon to make estimates for prospective operations, the information herein should be helpful. GENERAL CONDITIONS Mogollon is in the southern part of Catron County, southwestern New Mexico. It lies near the western border of the Mogollon Range, 14 miles east of the Arizona line. Silver City, 80 miles to the southeast, is the nearest railroad point. The connecting road, over which supplies are hauled into camp by trucks, is an improved highway for about 50 miles; the remainder consists of graveled roads and unimproved steep mountain grades. One general supply truck and one tank truck make daily round trips. Hauling of supplies to the mine has cost at the rate of $0.08 per ton-mile; or, on the basis of ore production, $0.30 per ton mined. Lumber, hauled in from local mills, has cost an average of $30.00 per 1000 board feet, $8.50 of which has been for hauling. The annual consumption averages 108,000 board feet. Lime, hauled from a plant in Arizona, is about the only other item not brought out from Silver City. Fuel oil for the generation of power is the item of greatest hauling expense, the f.o.b. Mogollon cost of approximately $0.06 per gal. being nearly twice the f.o.b. refinery price. Water for power plant, mill and camp use flows to camp storage tanks through a 4-in. pipe line from a spring and intake 3 miles up Silver Creek Canyon. A few times, particularly in the month of June, mill operations have been suspended for two or three days because of water shortage. MINING CONDITIONS During the years 1938, 1939, 1940 and 1941, the mine produced 230,059 dry tons

Jan 1, 1943

By Margaret Dienes, Karl L. Fetters

It is recognized that ingot structure is important in determining the quality of finished steel. Such elements of ingot structure as the size, shape and distribution of primary crystals; the size, shape and distribution of shrinkage cavities; the degree and kind of segregation (both macro and micro); the distribution of nonmetallic impurities and gas cavities are each the result of solidification phenomena. &apos;These structural features vary with variations in ingot practice. Their control requires a knowledge of their correlation with the variables of ingot practice. The structures of full-sized commercial steel ingots have been studied extensively by the Steel Ingots Committee of the Iron and Steel Institute.l This work has contributed much to our knowledge of ingot structure and the factors that control it. These investigations of necessity have been limited in scope because of their costliness and the great amount of time required. Studies of the structure of small steel ingots have not been very satisfactory because of the rapid rate of freezing of the ingots. Their structures are thus difficult to resolve and to interpret. Medium sizes of steel ingots in the ranges of 150 to 500 lb. do offer opportunity for study, but their cost also becomes greater and their use less expeditious. Experimental models for the study of steel-ingot structure have been made of nonferrous metals. Gathmann2 used lead-tin alloys and reported that they were satisfactory for determination of the location of the major shrinkage cavities and the Liplanes of weaknessv resulting from the pattern of crystallization. Certain features of mold design have been illustrated by these results. Bezdenezhnihk3 has used copper and aluminum ingots similarly and has shown the effect of mold-wall thickness on the depth of columnar grains. These studies of nonferrous models have been useful, but their results have been limited because the analogy with steel ingots obviously is not a close one. Model wax ingots have also been useful in pointing out important features of mold design. Gathmann4 watched the solidification of wax ingots, through a glass-walled mold, and has reported the effects of mold type on the location of the shrinkage cavities. Segregation was simulated by using a mixture of paraffin and stearine and adding a red dye that on freezing segregated preferentially to the stearine. Brearley5 also used wax models to determine the effects of some of the principal features of mold design. Carlsson and Hultgren6 dsed stearic acid to show that the columnar crystals of ingots tend to slope upward progressively from the mold wall toward the center of the ingot. As with the nonferrous ingots, the wax ingots have

Jan 1, 1943