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By A. Ross Rornmel

ABILITY to speak effectively is one of man's most longed for and coveted abilities. It is the ability to stand on one's feet, transfer knowledge and thoughts to others, to reach an objective professionally or otherwise by leading groups through a channel of planned thought. Each day group speaking plays an important part in making or marring success, and the engineering profession often provides this opportunity and requirement. An ability to speak effectively develops courage, poise, confidence, and prestige for the speaker. The technical man cannot be reluctant to face an audience. He is often called upon to do this in presence of employees, supervisors, and other groups. His ability to speak effectively is as much a requirement as the fundamentals of his profession. The three fundamentals of effective speaking are: (1) Enthusiasm and Confidence. These are joined because of their close relation. (2) Preparation. This includes knowledge of the subject. (3) Presentation. By this is meant the features of delivery.

Jan 1, 1946

By Benny Langston, Frank M. Stephens

Although little information is available concerning small-scale equipment for dust collection in laboratories, it is possible to adapt standard equipment for laboratory use. Dust from laboratory processes may be collected by cyclone separators, filters, electrostatic separators, scrubbers, and settling chambers. IN recent years much attention has been given to recovery, treatment, and disposal of dusts discharged into the atmosphere from operations of industry. considerable data has been accumulated on both operation and design of dust-collector equipment for commercial installations. On the other hand, there is almost no published data on design and construction of small-scale equipment to handle dust problems that arise in the ore-dressing laboratory. Dust-collection equipment such as multiclones, single-cyclones, scrubbers, chemical and mechanical filters, settling chambers, and electrostatic separators has proved its efficiency for collecting dust in industry. In the laboratory, however, the engineer is faced with the problem of collecting small quantities of dust, inexpensively, without diverting the major effort from the metallurgical problem to the problem of collecting dust produced by the process. For most applications standard dust-collection equipment is too large for use in the laboratory; however, for control of dust in large working areas it is often possible to use a standard dust collector, such as an air filter, with branch ducts to eliminate a health hazard. For example, the well-furnished sample-preparation room containing small jaw crushers, rolls, and pulverizers, in addition to the riffles and screens necessary for preparation of samples, presents a perennial source of dust. The authors' experience has shown that a combination system consisting of overhead branch ducts to the individual equipment and floor ducts with grills, where applicable, connected to a central dust collector effectively removes dust generated in preparation of samples. Fig. 1 is a sketch of a downdraft dust-collector for table installation. Similar systems can be built with floor grids. For portable equipment such as laboratory vibrating screens this type of installation with a steel grill to support the heavy load is reasonably efficient. Overhead branch ducts to individual crushing and grinding equipment, although efficient, must be carefully controlled by dampers to prevent excess loss or a change in the composition of the sample. Change in sample composition can result from excess velocity, which causes selective removal of constituents of low specific gravity. Fig. 2' shows the theoretical effect of terminal velocity on spherical particles of different specific gravities in air and water under action of gravity. Fig. 3 shows the effect of air velocity on composition of CaCO, coal mixtures. Although the entrainment of dust particles in a moving air stream is the basic mechanism by which all dust-collection equipment functions, usually intake velocity of the dust-collection system must be controlled to prevent loss of part of the sample. As an example of what may happen when excess velocities are used, a mixture of 50 pct coal and 50 pct limestone was crushed to —10 mesh and fed to a pulverizer equipped with an overhead dust-collection system. Fig. 4 shows the overhead dust-collection equipment used in this test. The pulverizer was set to give a product 95 pct —100 mesh in two stages. Velocity of air passing over the lip of the pulverizer was measured with an anemometer. After grinding, the finished product was analyzed to show the amount of calcium carbonate present. Fig. 3 shows graphically the increase in calcium carbonate as velocity through the dust-collection duct was increased. These data show that at a velocity of 1 ft per sec little if any of the coal was entrained by the overhead draft. At the maximum velocity, about 6.5 ft per sec, approximately 7 pct more coal was entrained than calcium carbonate. From an operating standpoint, this problem can be remedied easily by dampering the line to control velocity. The lowest velocity commensurate with satisfactory dust control should be used to prevent excess loss and, in some cases, selective dust loss. Collection of Dust in Laboratory Processes As in industry, the engineer desires to collect efficiently the dust produced by processes being investigated on a laboratory scale. However, in the collection of laboratory dusts he is faced with two additional problems: 1—The volumes of gas and the quantity of dust that must be recovered are small when compared with the capacity of standard dust-collector equipment, which must be scaled down in design except for collection of dust from large pilot-plant operations. 2—In addition, because of the variety of problems studied in the process laboratory, the engineer cannot design today a dust collector that will meet the conditions imposed by the processes of tomorrow. Sometimes, therefore, he must compromise collection efficiency to minimize the cost of fabrication and the amount of time diverted from the metallurgical to the dust-control problem. For collection of dust from laboratory processes a cyclone separator, filters, electrostatic separators, scrubbers, and settling chambers can usually be adapted for small-scale operations. The following

Jan 1, 1955

By Bruce T. Stanley

The concepts of ore reserve estimation at the Henderson mine are reviewed presenting a geostatistical approach and procedure as applied. Specific problems encountered are recapped and explained as to the nature and resolution thereof. The methodology and results are shown, along with an approximation of computer usage and capacities needed. The scope of the paper is to set forth an example of actual application, usage, and benefits realized from such a procedure. Local Conditions The Henderson molybdenite deposit is located in central Colorado about 69 kilometers west of Denver. The geology consists of a classic subvolcanic ryolite porphyry sequence with quartz-molybdenite mineralization occurring in an extensively fractured granite stock complex. Being assymetric and bilobate in section, the orebody measures approximately 300 meters thick and 600 meters by 1200 meters in plan. The orebody is sampled by means of underground drill holes which create an east-west fan pattern spaced roughly 60 meters apart in the north-south direction. Approximately 27,000 meters of drill hole assayed on 3.04-meter intervals were available for analysis. Recovery on the core is about 95 to 100 percent, thereby affording us with reliable data all prepared to the same standards.

Jan 1, 1977

By M. L. Pearce

A comparison of the isotope-dilution, vacuum-fusion, and chemical methods of analysis for nitrogen in Si-Fe is made with particular emphasis on the effect of sample history. The superiority of the isotope-dilution method from the point of view of 1 HE analytical techniques used to determine nitrogen in Si-Fe have been subjected to close scrutiny in recent years primarily because of the marked influence of the element on the properties of the alloy. These investigations have led to a diversity of opin- both precision and accuracy is demonstrated. The solubility of nitrogen in 3.06 pct Si-Fe is investigated and the effect of silicon content on the activity coefficient of nitrogen is derived. ion regarding the reliability of the vacuum-fusion and chemical methods of nitrogen analysis when applied to si- Fe.'-' A majority of workers appear to favor the vacuum-fusion method over chemical methods particularly in those cases where part of the nitrogen may exist as silicon nitride or the total nitrogen content is very low. Contrary views have been expressed, however,' and it has been demonstrated that for some Si-Fe alloys both methods yield results which are significantly lower than those

Jan 1, 1963

By Marius S. Darrow, William B. White, Rustum Roy

The PbS-PbTe systen has been studied by quench-ing and D.T.A. techniques f?om 400' to 1150°C. Runs were made in evacuated silica tubes so that all equilibria are at the vapor pressure of the system. Lattice parameters of the quenched salnples , measured by X-ray diffraction, show a complete crystalline-solution series existing over a narrow temperature range between approximately 805" and 871°C. An exsolution dome extends from a maximum of about 805"C (approximately 30 mole pct PbTe) to 1 and 96.5 pet PbTe at 400°C. A narrow melting region, deternined by D.T.A., extends form 918c (mp PbTe), The shapes of the liquides and solidus curves imply the existence of a minimum at 871°C at approximately 65 pct PbTe. THe exact composition of the minimum could not be established due to the very narrow two-phase region. At compositions containing less than 50 pet PbTe, liquidus temperatures begin to increase, while the solidus remains almost flat to about 15 mole pet PbTe before beginning to vise toward the mp of PbS (1075 C). LEAD sulfide and lead telluride are isostructural (NaC1 type) semiconductors whose electrical and optical properties have been extensively studied and used in recent years. If appreciable crystalline solution exists between these compounds, the variation of physical properties with composition could be of interest. The purpose of this investigation was to determine the extent, if any. of crystalline solution, and to obtain the phase diagram for the system. To the knowledge of the authors, only three studies of the system PbS-PbTe have been reported, and, in chronological order, each investigation found an increasing amount of crystalline solution. In 1956, Yamamoto reported finding no evidence of crystalline solution between the compounds. Sindeyeva and Godov-ikov,' in 1959, found very limited crystalline solution. but only under conditions of excess tellurium concentration. Finally Melevski s3 investigation in 1963 indicated that one solid phase exists in the region from PbS to 7 pct PbTe and from 82 pct PbTe to PbTe at 886'C, with an eutectic at 55 pct PbTe at that temperature. Detailed data on the solvus boundary were not given. EXPERIMENTAL EQUIPMENT AND MATERIALS Commercially produced PbTe and PbS powders were used as starting materials. Batches of specific mole percent composition were accurately weighed and mixed in a plastic bottle, in a shaker mill. An analy- sis of impurity content is given in Table I for pure PbS and PbTe and for two randomly selected batches after the powders were mixed. Individual samples, ranging in weight from 0.2 to 0.5 g, were sealed in evacuated silica tubes which had been thoroughly washed and rinsed with acetone and distilled water. Thus all data taken were at the pressure of the system. Subsolidus relations were studied down to 400°C by heating the samples in a vertical tube furnace for 24 hr. The sealed tubes were quenched in water with quench time from the hot zone not exceeding 1 sec. Temperatures were measured by a chromel-alumel thermocouple and controlled to 53°C for most runs. The number and composition of phases present were determined from powder X-ray diffraction patterns taken at room temperature on a Norelco diffractome-ter, using silicon as an external standard. Above 850°C quenching techniques were, in general, found to be unsatisfactory, and differential thermal analysis (D.T.A.) was used to determine melting relations. The evacuated tubes were recessed about 1 cm at one end to accommodate the differential thermocouple. Al203 was used as the reference material in a similar tube containing the other side of the differential couple. For temperature measurements, a separate thermocouple was placed in the recess of the tube containing the sample to be measured, thus providing an opportunity to obtain thermal, as well as differential, analysis. All thermocouples for these measurements were Pt-Pt 10 pct Rh. Temperature and differential curves were recorded separately on synchronized strip-chart recorders. Thermocouples and recording equipment were calibrated using NaCl and gold standards, using the melting points 801" and 1063 C, respectively, which span most of the temperature range of interest. Heating and cooling rates generally were from 4 to 7°C per min. It was found, in fact. that rates ranging from 1.5 to 25°C per min did not significantly change the data obtained.

Jan 1, 1967

By Will H. Coghill

WITH gold at $35 for the last four years, almost double the old figure, and 'an unlimited market, there is perhaps more activity in the mining and milling of that metal than in that of any other of the widely distributed ores. Despite threats from Russia, the Rand district is still dominant. In South Africa in 1936, 48,200,000 tons of gold ore was crushed after sorting out about 10 per cent of that mined. The pounding of 5914 trusty stamps on the 60 mi. of Rand reefs is noteworthy. At the end of 1935, 466 tube mills were operating on the Rand, the popular size being 6 1/2 by 20 ft. The grinding medium normally consists of ore pebbles picked from the ore but recently a composite load of 3-in. steel balls and pebbles has found favor for added capacity, a ratio of 2.5 tons of pebbles to one ton of halls being maintained. The total ore fed to the mills is only about 0.14 ton per hp.-hr. Such a slow rate 'of feed cannot help but result in overgrinding. Ball mills, 9 by 8 ft., some of which have come from Canada, are now being tried. Stamps have been ousted from all new flow sheets, but the old stamp mills are continually renovated and kept on duty as they are at the Homestake in the United States. Half of the world's gold and silver ores is still crushed by stamps, a few of which are single, dropping in individual mortars.'

Jan 1, 1938

By Arthur F. L. Bell

Prior to 1908 the oil production in the State of California had been almost entirely a heavy fuel oil, with a high flash point, but changed within a short period to a large percentage of refining oil with a low flash, by reason of the heavy production of light oil coming in from the Santa Maria field, the Midway field, and the increased production of the Fullerton field. This is clearly shown in the following tabulation of California's pro- The bringing in of these high percentages of light oil with their dangerous low flash and the increasing demand for the refined products necessitated the devising of some cheap and efficient means of quickly separating the lighter elements either in the field or at the main distributing points; also it became necessary to remove the excessive percentage of water which many of the light oils carried in emulsion. Union Oil Co. Port Harford Plant Probably the first important attempt to top light oil in California by other means than the ordinary stills was tried about 1908 by the Union Oil Co., at its plant at Port Harford, San Luis Obispo County, with Santa Maria oils. The process was the invention of Hubert G. Burroughs who afterward obtained a patent for the process, No. 998,837, dated July 25, 1911. The apparatus used consisted of a series of 12-in. pipes mounted in units of three pipes, one above the other, the crude oil being admitted to the upper pipe and filling it about two-thirds of its

Jan 1, 1916

By E. T. Dumble

Discussion of the paper of E. T. DUMBLE, presented at the San Francisco meeting, September, 1915, and printed in Bulletin No. 104, August, 1915, pp. .1623 to 1638. E. L. DEGOLYER, Norman, Okla. (communIcatIon to the Secretary*).-Referring to Mr. Dumble's description of the stratigraphy of eastern Mexico, I should like to question the classification of the ?Papagallos? or ?Mendez? shales as being of Cretaceous age and the so-called overlapping of the Papagallos or Mendez shales by the Alazan shales; the classification of the San Felipe series as Cretaceous, and the correlation of the San Felipe series with the San Juan limestones. Mr. Durable apparently recognizes the continuity of the great shale formation by his use of the terms "Papagallos" and "Mendez," as equivalent and interchangeable, since the Papagallos Hills in the State of Nuevo Leon and Mendez Station in Northern Vera Cruz, localities at which the shale formation outcrops, and from which the formation names are taken, are approximately 250 miles apart and on opposite sides of the Tamaulipas barrier. The Papagallos shales (evidently referring here to the northern extension only) are said to be non-fossiliferous and no reason for .their Cretaceous classification is given, though in a previous article' they are classified as Cretaceous because at their northernmost outcrop they "have the same relation toward the overlying Tertiary that the Escondido (Cretaceous) has through its whole extent." The Alazan fossil locality was found by me and the first collections from it were sent to Dr. Dall; about 17 species of marine invertebrates were recognized by him, the fauna noted as having a distinct Pacific tincture, and the age of the formation from which they cause pronounced lower Eocene. The outcrop of the shale formation has been traced continuously from this point by me and my assistants into the Panuco River region, where Eocene fossils are reported at a depth of 1,810 ft. in a well at Topila.2 From Topila the formation has been traced continuously north to the Padilla-Jiminez region in Central Tamaulipas. Lithologically, the formation is fairly constant and though I am only generally acquainted with it north of the Padilla-Jiminez region, until definite evidence of the Cretaceous age of the Papagallos shale in its type localities, or of an overlap, is available, it seems to me more logical to consider the shale formation a single stratigraphic unit of Eocene age.

Jan 12, 1915

Gardner I?. Williams, authority on diamond mining, died at San Francisco, Cal., on Aug. 22, after an illness of nearly a year. Mr. Williams, who was in his eighty-first year, was born in Saginaw, Mich. He was graduated from the University of California in 1865, and afterward took a course at the Freiberg Mining Academy in Saxony. He was awarded the degree of LII. D. by the University of California in 1910, and Doctor of Engineering by the University of Michigan in 1917. Beginning in 1870, Mr. Williams spent two years as assistant assayer at the United States Mint in San Francisco. He successfully developed

Jan 1, 1923

Gardner I?. Williams, authority on diamond mining, died at San Francisco, Cal., on Aug. 22, after an illness of nearly a year. Mr. Williams, who was in his eighty-first year, was born in Saginaw, Mich. He was graduated from the University of California in 1865, and afterward took a course at the Freiberg Mining Academy in Saxony. He was awarded the degree of LII. D. by the University of California in 1910, and Doctor of Engineering by the University of Michigan in 1917. Beginning in 1870, Mr. Williams spent two years as assistant assayer at the United States Mint in San Francisco. He successfully developed

Jan 1, 1923

By F. F. Sharpless

ON Saturday evening, Sept. 9, a small party of Institute members, their wives and friends, left New York to attend the Fall Meeting of the Institute at San Francisco. In this party there were: President and Mrs. Arthur S. Dwight; Mr. and Mrs. George D. Barron; Mr. and Mrs. H. J. Stehli; N. S. Spencer and Miss Spencer; the Secretary and Mrs. F. F. Sharpless. They were joined at Chicago by E. F. Eurich, and by Mr. and Mrs. R. L. Baldwin and daughter. Our party was met at Chicago by Mr. and Mrs. L. V. Rice, Mr. and Mrs. A. D. Terrell and W. F. Boericke, who constituted themselves an impromptu entertainment committee and proceeded to carry out a delightful little program. We were taken to the Lake Shore drive, where a stiff wind off the lake refreshed us after a sultry day on the train, and on our return to the city saw Chicago illuminated with all its brilliance of electricity. We were entertained at dinner at the Drake Hotel. In spite of being two hours late getting into Omaha, we were right on the dot at Denver on Tuesday morn-ing. Horace F. Lunt came to the hotel soon after breakfast, and told us that a trip to the mountains had been planned. Having learned the number in the party, he began to gather up his automobiles for a 10 o'clock start.

Jan 10, 1922

By P. C. Johnson, B. A. Stein

This paper describes a study of the effects of combined heat treatment and explosive loading on the mechanical properties of high-strength steels. nis program investigated two distinct areas: 1) the effect of shock waves, without gross irreversible defmmution, on a 3-Cr steel at various stages of heat treatment; and 2) the effect of rapid deformation (explosive forming) on H-11 and D6-AC steels in the metastable austenitic state. The mechanical properties of these steels were improved, in some cases markedly, as a result of these treatments. ,AUSFORMWG, which requires the plastic deformation of metastable austenite, is a process which can appreciably improve the properties of selected alloy stee1s.l,2 The Ausform process significantly increases the strength of these steels without decreasing their ductility. The properties at high temperatures are also improved through a change in the response of the steels to tempering. Although the mechanism by which ausforming alters the properties of these steels is not fully understood, it appears that the dislocation arrays produced by deformation of the metastable austenite influence the structure of the martensite on subsequent transformation. This, in turn, affects the strength, ductility, and tempering response of the martensite. This research used chemical explosives to deform steels at various stages in their heat treatment in order to improve the properties of these steels. The explosive energy is used in two ways; 1) high-pressure shock waves are propagated through the steel to produce extensive microscopic shear strain without causing a large irreversible change in shape, and 2) explosive energy is used to cause extensive macroscopic plastic strain in the metastable austenitic state (explosive forming). I) AUSFORMING WITH INTENSE SHOCK WAVES The steel used in this phase of the research was an alloy having a nominal composition 0.43 pct C, 3.0 pct Cr, 1.5 pct Ni, and 1.5 pct Si. The steel was subjected to intense shock waves in three conditions: 1) in the metastable austenitic state, 2) in the tempered mar tens itic state, and 3) in the tempered martensitic state after ausforming by conventional techniques. The specimens were in the form of disks 2.75 in. in diam and 5/16 in. thick. These were incorporated into a specimen assembly consisting of two disks pressed into a 5 by 5 by 1 in. block of stainless steel, Fig. 1. Spalling (or scabbing) is confined to the front disk. The specimen is protected from oxidation and decarburization by the surrounding metal. The temperature of the assembly is monitored by a thermocouple inserted into one side of the stainless steel block. The assembly is positioned over an oil reservoir which serves both as a means of catching the disks and as quenching medium for the disks shocked under ausforming conditions. Plane shock waves are introduced into the assembly by a metal driver plate impacting the top surface of the block. The driver plate is accelerated by a chemical explosive sheet supplied by E. I. du Pont de Nemours & Co. All the specimens were subjected to plane shock waves having a peak pressure of approximately 430 kbar. The pressure is that quoted by G. E. Dieter for the plane wave generator used in this work.' The driver plate used was 1/4 in. thick, so that the initial pulse was essentially a l/2-in.-wide square wave. The attenuation of the peak pressure during the subsequent 1/4 in. is estimated to be less than 5 pct. The shock front induces a temperature rise, a portion of which is irreversible. Rough estimates (+25 pct) of this temperature rise have been made for iron shocked at room temperature.4 For a 500-kbar shock wave, the temperature rise in the shock front is about 700°F, and is held for a time of the order of microseconds. The irreversible temperature rise, which remains after the shock wave passes, is about 450°F.4 The disks are quenched to room temperature within a few seconds of the shock treatment. It should be emphasized that the temperature rises given above are estimates for pure iron at room temperature, and are not necessarily true for the tests made in this work. The disks shocked at temperatures in the metastable austenitic range were austenitized in the stainless steel assembly in a furnace protected from the firing area. The assembly was removed from the furnace and placed over the recovery reservoir. The plane wave generator was then positioned and

Jan 1, 1963

By C. M. Signer, W. P. Hewitt

THIS is a story of a mine discovered in the days of the Conquistadores but that remained unimportant until the second decade of this century. Without the usual legendary history of romance and fabulous riches it has become famous for the development of unexpected metals and unusual problems. These developments and experiences, exciting and interesting as any legend, are the substance of the San Antonio mine of the Santa Eulalia district in northern Mexico. Originally opened for its silver-lead content, it developed a tin deposit of singular economic importance and unique geologic interest, a vanadium orebody that for a few years placed it among the leading vanadium producers of the world, and now lead and zinc sulphide ores. It has been the seem of a disastrous flood that brought deep-sea divers into Mexico's desert mountains and raised important problems regarding ground water, demanding unusual measures. Geology and operating questions relating to the above matters will be discussed and much of it is recent history which has become a part of Mexican mining lore. History Dates Back to 1325 Santa Eulalia is the oldest of American cities, founded in 1325 by the Aztecs under the name of Tenochtitlan and devastated in 1521 by Cortes and his rapacious band of iron-willed adventurers. Their lust for gold burned through the Aztec empire and onward into most of North America. Santa Eulalia was in the path of conquest. In 1591 the district's first ore discovery was made near what is now the San Antonio mine. The ores carried no gold and the silver-lead content was unattractive to the early pioneers. Not until 1700 was real mining activity undertaken.

Jan 1, 1952

By John Cogan

INTRODUCTION Lake tapping is a method of blasting an intake into a body of water from below the natural water surface without first lowering that surface or installing a protective cofferdam around the tap hole. Lake taps are done by first excavating a tunnel almost to the water/rock contact and then blasting out the final protective rock plug at one time to allow water to suddenly inflow into the tunnel from the lake. This procedure can be done "dry" or "wet." In the dry method the tunnel is empty of water before the final plug blast while in the wet method it is partially filled with water. This paper describes a wet method lake tap as performed at Alaska Power Authority's Tyee Lake Hydroeletric Project in southeast Alaska. The Tyee Lake project is located approximately 40 miles southeast of Wrangell, Alaska, in a glacially formed valley called the Bradfield Canal. The project consists of a powerhouse located at sea level on the canal, a system of tunnels and shafts connecting the powerhouse to Tyee Lake at elevation 373 m (1225 ft), and an 129 km (80-mile) electrical transmission line leading from the powerhouse to Wrangell and then Petersburg, Alaska. Tyee Lake itself is a natural lake gouged out of the rock by glacial ice during the last ice age. The objective of the project was to tap into the lake and use the water as a source for power production. The techniques used for lake taps have been developed in Norway where conditions are favorable for their use in hydroelectric proj¬ects. Over 100 have been performed. In the United States the Tyee

Jan 1, 1984

By W. R. Hibbard

Evidence is presented which confirms previous findings that models of solution strengthening depending solely on lattice parameter changes are incomplete. Direct evidence for the Suzuki interaction of chemical effects was obtained from alloys with constant lattice parameter, for which solution strengthening was nearly independent of temperature from 300° to 20°K. SOLUTION hardening principles have been reviewed recently by Parker and Hazlett.' In addition, the interactions of dislocations and solute atoms were reviewed by Cottrell.' It is not proposed to review this information again here, but to refer only to those details which are pertinent to the developments which have occurred since these papers were published. Literature Survey To set the stage, it has been known for some time that solid solutions are stronger than the pure parent metals, and that the strength increases with increasing amounts of alloying element. One of the most extensive earlier investigations was that of Lacy and Gensamer,3 who reported that the solid solution strengthening of iron is a power function of the composition, that the relative strengthening is a function of the solubility limit, and that the rate of strain hardening is a function of the amount of solution hardening. Thus, the slope of the plastic portion of the stress-strain curve increases with increasing yield strength. An approach to the development of principles resulted from work by Gulyeav,4 who reported that the strengthening effect of solid solution alloys is periodic in character when plotted as a function of the atomic number of the solute. A more quantitative approach was to relate the amount of solution hardening to the lattice parameter of a solid solution. This was done quite early by Norbury,5 and later by Brick, Martin, and Angier,6 Frye and Hume-Rothery,7 and French and Hibbard. This relationship is only approximate in character. The next development was to relate the amount of solution hardening to lattice stress, as proposed by Frye and co-workers.9 They calculated what they called ionic overlap from the lattice parameter changes represented as a change in volume, using Bridgman's hydrostatic compression equation. The resulting correlation was somewhat improved as compared to the simple correlation with lattice parameter. The next step was carried out by Dorn, Pietrow-sky, and Tietz,10 who suggested an effect of valence differences in addition to the effect of lattice parameter. Their proposed parameter shows flow stress as a single valued function of the concentration and a relationship involving these two atomic variables. In addition, they contributed new data on the temperature dependence of solution hardening which indicated that it was a strong function of temperature for aluminum alloys. Allen, Schofield, and Tate11 carried the valency effect even further by reporting data indicating that with a given solvent element the stress-strain curve is a function of electron density, entirely neglecting the size factor, which varied by a factor of two. This evidence led to a quantum mechanical calculation by Cottrell, Hunter, and Nabarro,12 based on the formation of a dipole around an edge disloca-

Jan 1, 1959

By J. D. Hanawalt

Significant strides were made in the year 1948 leading to further recognition of the place of magnesium as a common commercial metal, rather than as just a premium aircraft material. One of the factors contributing to this recognition was the price stability and, in many cases, price reduction of magnesium products in 1948. In contrast to most other metals, manufacturing advances in magnesium outweighed the effects of increased labor and other costs. At the present time, many magnesium extrusions, die castings, and permanent mold castings can be purchased as cheaply as their aluminum counterparts in these forums, though competitive prices for sheet still await the inauguration of a modern tandem rolling mill for magnesium, such as has already been demonstrated.

Jan 1, 1949

By John L. Lamont, Walter Crafts

SELECTION of an alloy steel for a heat-treated article has been facilitated by methods for the calculation of hardenability,1 as-quenched hardness,2,3 and tempered tensile strength.4 Ductility and toughness may also be estimated if the steel is completely hardened on quenching,5,6 and the present study was carried out in order to develop a basis for estimating the Izod impact strength of partially hardened steel. The investigation was directed toward the prediction of Izod impact strength in steels of normal commercial quality without consideration of special compositions or heat-treatments that might produce abnormal brittleness. It was found that Izod impact strength of alloy steel is controlled by hardness, degree of hardening on quenching, and grain size. In fine-grained steels the impact strength for any given degree of hardening is inversely proportional to the tempered Rockwell C hardness, and the relation of impact strength to hardness is lowered by incomplete hardening. Calculation of the tensile strength and impact strength of heat-treating steels has shown that, except at very high strengths, tensile strength is raised by alloys without loss of impact strength whereas the tensile strength gained by higher carbon contents tends to be accompanied by a disproportionate loss of toughness. Plain carbon steels give relatively low and unpredictable impact strength. The calculation is sufficiently accurate to be helpful in the selection of alloy steel, and common grades of alloy steel have been evaluated with respect to combinations of tensile strength and impact strength attainable after heat-treatment in sections from I to 4 in. in diameter. PROCEDURE The study of the relation of hardness to impact strength was based on test data derived from 24 heats from four producers. The steels included the following SAE and AISI compositions: 1020, 1o30, 1040, 1340, 3310, 3316, 4320, 4330, 4340, 8620, 8630, 8640, 8720, 8730, 8740, 9310, 9317, 9440, 9917 and three high-alloy chromium-nickel-molybdenum steels. As far as is known, the steels tested were of normal commercial quality. They were supplied in 4-in. sections, which were forged to smaller sizes, prenormalized, and machined to final dimensions. Heat-treatment was carried out by heating to the usual austenitizing temperature for the grade of steel, holding for one hour per inch of thickness and quenching in still oil at room temperature. Previous work had indicated that this quenching treatment approximates a severity of H = 0.35. The bars were tempered as follows: ½ in., I in., and I 5/8 in., 2 hr; 2 ½ in., 3 hr; 4 in., 5 hr. All bars were air-cooled from the tempering tem-

Jan 1, 1947

By F. L. Sizer

SOME old-time views which have recently come into my possession have inspired me to record that part of the early history of Leadville, Color- ado, with which I am familiar, the years 1878 to 1882, in the hope that others will add to what is here mentioned. My first appearance in Leadville was in June, 1878, immediately after graduation from the University of Michigan, and I found a congenial and lively crowd of young men, already there. The old log hotel, at the corner of Pine and State streets, housed some distinguished guests in the summer and fall of 1878. It was my good fortune there to make the acquaintance of James B. Grant, afterwards Governor of Colorado, in July of that year, when we were both glad of the accommodation afforded by cots in the second floor loft of the hostelry presided over by Herman Hibschle. Grant was then building his smelter and our associates were Eddy and James, August R. Meyer, and Berdell and Witherell. The Grand Hotel-Harris and Walsh, pro- prietors-was the first-class hotel of the place; but in a very few months there were many competitors.

Jan 1, 1924

By W. Crafts, J. L. Lamont

Selection of an alloy steel for a heat-treated article has been facilitated by methods for the calculation of harden-ability,' as-quenched hardness and tempered tensile strength.2 Ductility and toughness may also be estimated if the steel is completely hardened on quenching, 5,6 and the present study was carried out in order to develop a basis for estimating the Izod impact strength of partially hardened steel. The investigation was directed toward the prediction of Izod impact strength in steels of normal commercial quality without consideration of special compositions or heat-treatments that might produce abnormal brittleness. It was found that Izod impact strength of alloy steel is controlled by hardness, degree of hardening on quenching, and grain size. In finegrained steels the impact strength for any given degree of hardening is inversely proportional to the tempered Rockwell C hardness, and the relation of impact strength to hardness is lowered by incomplete hardening. Calculation of the tensile strength and impact strength of heat-treating steels has shown that, except at very high strengths, tensile strength is raised by alloys without loss of impact strength whereas the tensile strength gained by higher carbon contents tends to be accom- panied by a disproportionate loss of toughness. Plain carbon steels give relatively low and unpredictable impact strength. The calculation is sufficiently accurate to be helpful in the selection of alloy steel, and common grades of alloy steel have been evaluated with respect to combinations of tensile strength and impact strength attainable after heat-treatment in sections from I to. 4 in. in diameter. Procedure The study of the relation of hardness to impact strength was based on test data derived from 24 heats from four producers. The steels included the following SAE and AISI compositions: 1020, 1030, 1040, 1340, 3310, 33167 4320, 43.30, 4340, 8620, 8630, 8640, 8720, 8730, 8740, 931°, 9317, 9440, 9917 and three high-alloy chromium-nickel-molybdenum steels. As far as is known, the steels tested were of normal commercial quality. They were supplied in 4-in. sections, which were forged to smaller sizes, prenormalized, and machined to final dimensions. Heat-treatment was carried out by heating to the usual austenitizing temperature for the grade of steel, holding for one hour per inch of thickness and quenching in still oil at room temperature. Previous work had indicated that this quenching treatment approximates a severity of H = 0.3; The bars were tempered as follows: 34 in., I in., and 1% in., 2 hr; 235 in., 3 hr; 4 in., ; hr. All bars were air-cooled from the tempering tem-

Jan 1, 1948

By J. L. Lamont, W. Crafts

Selection of an alloy steel for a heat-treated article has been facilitated by methods for the calculation of harden-ability,' as-quenched hardness and tempered tensile strength.2 Ductility and toughness may also be estimated if the steel is completely hardened on quenching, 5,6 and the present study was carried out in order to develop a basis for estimating the Izod impact strength of partially hardened steel. The investigation was directed toward the prediction of Izod impact strength in steels of normal commercial quality without consideration of special compositions or heat-treatments that might produce abnormal brittleness. It was found that Izod impact strength of alloy steel is controlled by hardness, degree of hardening on quenching, and grain size. In finegrained steels the impact strength for any given degree of hardening is inversely proportional to the tempered Rockwell C hardness, and the relation of impact strength to hardness is lowered by incomplete hardening. Calculation of the tensile strength and impact strength of heat-treating steels has shown that, except at very high strengths, tensile strength is raised by alloys without loss of impact strength whereas the tensile strength gained by higher carbon contents tends to be accom- panied by a disproportionate loss of toughness. Plain carbon steels give relatively low and unpredictable impact strength. The calculation is sufficiently accurate to be helpful in the selection of alloy steel, and common grades of alloy steel have been evaluated with respect to combinations of tensile strength and impact strength attainable after heat-treatment in sections from I to. 4 in. in diameter. Procedure The study of the relation of hardness to impact strength was based on test data derived from 24 heats from four producers. The steels included the following SAE and AISI compositions: 1020, 1030, 1040, 1340, 3310, 33167 4320, 43.30, 4340, 8620, 8630, 8640, 8720, 8730, 8740, 931°, 9317, 9440, 9917 and three high-alloy chromium-nickel-molybdenum steels. As far as is known, the steels tested were of normal commercial quality. They were supplied in 4-in. sections, which were forged to smaller sizes, prenormalized, and machined to final dimensions. Heat-treatment was carried out by heating to the usual austenitizing temperature for the grade of steel, holding for one hour per inch of thickness and quenching in still oil at room temperature. Previous work had indicated that this quenching treatment approximates a severity of H = 0.3; The bars were tempered as follows: 34 in., I in., and 1% in., 2 hr; 235 in., 3 hr; 4 in., ; hr. All bars were air-cooled from the tempering tem-

Jan 1, 1948