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By C. P. Proctor, J. T. Crawford

TROUGH washers were among the earliest methods used for concentrating ores; they are referred to by Agricola about the middle of the sixteenth century as already being used while the hand- operated jigging sieve had only recently come into use. For cleaning coal the trough washer apparently was first used in France and Belgium .about 1841. The early trough washers were intermittent and the refuse at least was shoveled out by hand. The invention of a continuous jig washer, by a Frenchman, Berard, in 1848, acted as a stimulus to coal washings in jigs and retarded progress in trough washing' in the nineteenth century. Chapman and Mott describe a number of trough washers developed in England and on the Continent from 1850 to 1900, such as the Bell and Ramsay, Ramsay, Bell and Green, Wunderlich, Scaife, McLellan; Lodge, Elliott, Blackett, and Murton. , The later of these removed the refuse mechanically, either intermittently or continuously, but in ways that interfered with stratification. THE RHEOLAVEUR A Belgian engineer, Antoine France, is responsible for the development of means to remove refuse materials continuously from a trough washer while preserving stratification and preventing the loss of coal with the refuse. The methods and equipment devised, which have become known throughout the world as Rheolaveur, were initiated at the St. Nicholas mine near Liége, Belgium, about 1912. This installation consisted of two units to wash 20 to 8-mm. (13/15 to 5/16 in.) and 8-mm. to 0 (5/16-in. to 0), each having only two superimposed inclined troughs. The first few "Rheo" boxes on the top trough removed refuse directly and the remaining Rheo boxes discharged impure refuse to the lower trough for rewashing. On the lower trough the first few boxes removed refuse and the following boxes removed a middling product

Jan 1, 1943

By Fred A. Anderson, George B. Wallace, Edward J. Slebir

Auburn Dam will be a thin, double-curvature concrete arch dam about 685 ft high. With a crest length of about 4000 ft, it will be the world's longest single-arch dam. The site is located on the North Fork of the American River about 40 miles northeast of Sacramento, Calif. Construction is scheduled to get under way in 1970. In planning for the design and construction of Auburn Dam (see artist's conception), the foundation material, with its various discontinuities, is being investigated and the structural characteristics of the rock mass evaluated. The investigation and testing programs will aid in defining the pertinent geologic features and their individual and cumulative influence on the foundation. The work includes geologic surface mapping, surface trenching, core drilling, geophysics, tunneling, excavating shafts and raises, performing in-situ tests, and conducting laboratory tests on core and block samples. Competent amphibolite is the predominant material in the foundation, but significant bodies of chloritic, talcose, and metasedimentary rocks, a strongly developed jointing pattern, faults, and shear zones also affect the deformability of the rock mass. A comprehensive rock mechanics program, closely coordinated with geologic investigations as well as the engineering studies, therefore is required The rock mechanics work is a combination of many analytical studies and experimental investigations. The experimental work includes laboratory tests on core samples from holes drilled for geological studies of the entire foundation and in-situ tests performed in selected areas. The laboratory testing program evaluates the general properties of all important rock types and aids in correlating many of the key structural features encountered within the foundation. To derive maximum benefit from the field tests, they are conducted in materials which represent a

Jan 1, 1970

By E. C. Harder

INTRODUCTION THE situation in the United States, at the present time, regarding the supply of manganese ores and alloys of manganese is one of great seriousness and is likely to become increasingly so while the European war continues. The two principal iron-manganese alloys, ferromanganese and spiegeleisen, are indispensable in steel manufacture, being used extensively in the Bessemer and openhearth processes.. Spiegeleisen, the lower alloy, contains between 15 and 25 per cent., and ferromanganese, the higher alloy, between 60 and 80 per cent., of manganese. Besides manganese the alloys contain iron and carbon. On the market ferromanganese is usually quoted on the basis of 80 per cent. manganese, and spiegeleisen on the basis of 20 per cent. manganese. The consumption of ferromanganese has been increasing during recent years at the expense of spiegeleisen, because larger quantities of the latter must be used to ac-complish the same purpose with the result that the amount of carbon introduced with it into the molten metal is frequently injuriously great. Manganese ore proper, in the form of manganese dioxide, is used extensively in many chemical industries, especially for oxidizing purposes. It is also used for the manufacture of both wet and dry electric cells and in the manufacture of paints and dyes. The manganese ore used in this country has been derived hitherto from three principal sources:. Southern Russia, Southern British India and East Central Brazil. The following tables show the quantity of manganese ore imported from these countries, and (for comparison) the domestic production, during 1912, 1913 and 1914. The imported manganese ore has been used largely in the manufacture of iron-manganese alloys and in addition large quantities of the alloys themselves have been imported, chiefly. from Great Britain, Germany and other European countries.

Jan 5, 1916

By C. M. Tucker, K. R. Van Horn, W. P. Sykes

Recent investigations of the molybdenum-carbon alloys have been reported by Becker and Ebertl,‡ Westgren and Phragmén2, T. Takei3, and H. Tutiya4. Takei3 studied the Mo-C system by employing metal-lographic and X-ray methods, and the other publications described the determination of the crystal structure of the molybdenum carbides. In exploring this system by a technique previously applied to the tungsten-carbon series5, the results of Takei were confirmed with two definite exceptions; i.e., first the composition of the eutectic, and second the nature of the carbon-rich intermediate phase. Consequently, a more thorough examination of the molybdenum-carbon constitution was initiated in an effort to correlate the data supplied by the microstructures, diffraction patterns and chemical analyses. Metallographic Investigation A briquette of molybdenum powder when heated in a carburizing atmosphere at 1500" to 1600" C. for several hours develops the carbon-rich layer shown in Fig. 1. The carburization was accomplished by placing the briquette in a carbon tube, which was heated in the hydrogen atmosphere of an alundum muffle wound with tungsten resistor. While the macrostructure indicates two distinct shells, and suggests the possibility of two carbon-rich phases, no evidence of this condition could be detected by the microscope, which revealed but one high-carbon constituent. This carbide forms next to the molybdenum as a relatively dense, light-colored zone (Fig. 2) which passes abruptly into an outer layer of spongy texture. As will be noted later, only one intermediate phase was observed in the X-ray photograms prepared of different locations in the carburized zone. The metallographic structure at the inner border of the shell, reproduced in Fig. 3, shows a marked porosity accom-

Jan 1, 1935

RichaRd PeaRce, Argo, Colo.: This contribution upon the very interesting subject of the origin of the gold of certain lode-formations offers many subjects for thonghtful consideration. The explanation, for instance, of the perplexing features of thin lava dikes seems to me to be in harmony with facts as I have myself observed them elsewhere. At Marshall basin, near Telluride, Colorado, there is an extensive lava-flow. The material of this formation contains a large proportion of fragments of foreign matter in the form of angular pieces of rock. The latter show no signs of having undergone metamorphism, such as would be expected to be due to the direct effects of heat; and the evidence in this particular case would certainly lead me to suppose that the flow was due to causes analogous to those suggested by Mr. Rickard. It was, I believe, a moving mass of material, having a temperatrire considerably below the actual melting-point of the rock of which it is composed. In regard to the theory which the author has built up from the existence of the iodide of gold in sea water, I cannot consider it untenable ; but I would put the question whether any investigations have been made with a view to determining whether gold and silver occur in the beds of rock-salt, formed, as is generally allowed, by the evaporation of bodies of salt water. At Stassfurt, in Germany, there is a very remarkable series of alternating beds of rock-salt and anhydrite, the uppermost members of which are covered with deposits of potash salts. The question occurs to me, why should not gold and silver have been discovered in these deposits? Iodine and bromine, I believe, have been found in the salts last deposited by

Jan 1, 1894

By E. C. Harder

The situation in the United States, at the present time, regarding the supply of manganese ores and alloys of manganese is one of great seriousness and is likely to become increasingly so while the European war continues. The two principal iron-manganese alloys, ferromanganese and splegel-eisen, are indispensable in steel manufacture, being used extensively in the Bessemer and open-hearth processes. Spiegeleisen, the lower alloy, contains between 15 and 25 per cent., and ferromanganese, the higher alloy, between 60 and 80 per cent., of manganese. Besides manganese the alloys contain iron and carbon. On the market ferromanganese is usually quoted on the basis of 80 per cent. manganese, and spiegeleisen on the basis of 20 per cent. manganese. The consumption of ferromanganese has been increasing during recent years at the expense of spiegeleisen, because larger quantities of the latter must be used to accomplish the same purpose with the result that the amount of carbon introduced with it into the molten metal is frequently injuriously great. Manganese ore proper, in the form of manganese dioxide, is used extensively in many chemical industries, especially for oxidizing purposes. It is also used for the manufacture of both wet and dry electric cells and in the manufacture of paints and dyes. The manganese ore used in this country has been derived hitherto from three principal sources: Southern Russia, Southern British India and East Central Brazil. The following tables show the quantity of manganese ore imported from these countries, and (for comparison) the domestic production, during 1912, 1913 and 1914. The imported manganese ore has been used largely in the manufacture of iron-manganese alloys and in addition large quantities of the alloys themselves have been imported, chiefly from Great Britain, Germany and other European countries.

Jan 1, 1917

By C. M. Tucker, K. R. Van Horn, W. P. Sykes

Recent investigations of the molybdenum-carbon alloys have been reported by Becker and Ebertl,‡ Westgren and Phragmén2, T. Takei3, and H. Tutiya4. Takei3 studied the Mo-C system by employing metal-lographic and X-ray methods, and the other publications described the determination of the crystal structure of the molybdenum carbides. In exploring this system by a technique previously applied to the tungsten-carbon series5, the results of Takei were confirmed with two definite exceptions; i.e., first the composition of the eutectic, and second the nature of the carbon-rich intermediate phase. Consequently, a more thorough examination of the molybdenum-carbon constitution was initiated in an effort to correlate the data supplied by the microstructures, diffraction patterns and chemical analyses. Metallographic Investigation A briquette of molybdenum powder when heated in a carburizing atmosphere at 1500" to 1600" C. for several hours develops the carbon-rich layer shown in Fig. 1. The carburization was accomplished by placing the briquette in a carbon tube, which was heated in the hydrogen atmosphere of an alundum muffle wound with tungsten resistor. While the macrostructure indicates two distinct shells, and suggests the possibility of two carbon-rich phases, no evidence of this condition could be detected by the microscope, which revealed but one high-carbon constituent. This carbide forms next to the molybdenum as a relatively dense, light-colored zone (Fig. 2) which passes abruptly into an outer layer of spongy texture. As will be noted later, only one intermediate phase was observed in the X-ray photograms prepared of different locations in the carburized zone. The metallographic structure at the inner border of the shell, reproduced in Fig. 3, shows a marked porosity accom-

Jan 1, 1935

By Arthur West

IT is the purpose of this paper to describe briefly some recent large power stations for blast furnaces, where the blast is exclusively supplied by gas engines using furnace gas. The stations are given in the chronological order in which they were designed, in order to indicate the various improvements suggested by experience. Fig. 1 shows the blowing-engine station of the Bethlehem Steel Co. at Bethlehem. Although the picture shows only five blowing engines, the house now contains 11 engines. In the diagrammatic. plan the arrow shows the position and direction of camera. This station handles five modern blast furnaces of 450 to 500 tons capacity each. In this, as in all the other stations described in this paper, each furnace is blown by-two single tandem gas engines. Ten engines are thus required for five furnaces, leaving one single tandem spare engine. This spare capacity has been shown by several years' experience at Bethlehem to be adequate to insure continuous operation. The engines in the Bethlehem station are right hand and left hand, arranged in pairs. The outboard bearings of each pair are close together so that there is not room for passageway between them. On the right of the picture are shown the inclined drums communicating with the cold-blast lines outside of building, so that any engine may be operated on any furnace. The illustration shows four cold-blast gate valves with pipes passing through wall, but since the photograph was taken the drums have been extended to take care of a fifth valve for a fifth furnace. At the extreme back of the picture can be seen the tubs of three twin vertical-horizontal Southwark steam blowing engines, which, although of modern design and as good as new, are not operated because of the greatly reduced blowing cost shown by the gas blowing engines.

Jan 6, 1915

By George M. Enos, Robert J. Anderson

This paper gives a summary of tests made on the accelerated electrolytic corrosion of the tin brass, 70:29:1 copper-zinc-tin (admiralty metal), of different grain sixes in various electrolytes. There has been great difference of opinion as to the effect of grain size on the corrosion rate of brass, particularly in condenser-tube practice, but so far as is known no information has been published on the subject. It has been assumed, on the basis of the amorphous-cement theory, that fine-grained brass would corrode more rapidly than coarse-grained because the amorphous phase is more soluble than the crystalline and there is more cement per unit area exposed in the fine-grained material. In previous work on the corrosion of metals and alloys in acid mine waters from coal mines,1,2 it was found that the grain size, within a restricted range, had practically no effect on the corrosion of the brass 70:29:1 copper-zinc-tin: In the tests made, samples of three grain sizes were included; viz., 0.025, 0.035, and 0.075 mm. diameter (1600, 817, and 177 gr. per sq. mm., respectively), and the average losses on exposure to the most acid of three waters were 7.07, 6.80, and 6.72 mg. per sq. cm. per day (24 hr.), respectively. No distinguishing features were observed on microscopic examination of the corroded samples. In two other mine waters, the corrosion losses were substantially the same for the respective samples. These tests were -incidental to other tests and were not sufficiently comprehensive to warrant drawing definite conclusions. In further work with the accelerated electrolytic corrosion test, as developed recently in the Bureau of Mines, tests were made

Jan 1, 1924

By Robert E. Palmer

The Hawkesworth detachable drill steel shank and bit were invented by A. L. Hawkesworth, while he was a mechanical foreman for the Anaconda Copper Mining Co., at Butte, Mont. Mr. Hawkesworth died on June 16, 1925, at the time that his invention was practically a proved success. The first application for patents was made by him in November, 1918, and the bit is now being manufactured under patents issued in 1922 and 1923. The credit for its development in the early stages belongs to A. L. Hawkesworth, Roy S. Alley, Harry A. Gallwey, E. J. Bowman and various officials of the Anaconda Copper Mining Co. Later improvements, manufacturing problems and the direct usage in the mines were originated and perfected by the mechanical department under C. D. Woodward, E. R. Borcherdt, head of the Rock Drill Equipment Department, Robert E. Kelly of the Mechanical Department, and various operating department heads of the Anaconda Copper Mining Co. The author wishes to acknowledge the assistance of these officials in the preparation of this paper. Comparison of Costs Using Regular Drill Steel and Detachable Drill Steel In 1922 production was satisfactory and sufficient enough to warrant a complete installation in an operating mine. The study and tests were made at the Badger State mine, the production of which averaged 1200 tons of ore per day. E. R. Borcherdt, head of the rock drill equipment department, was in direct charge of the trials, installation, operating problems and records during the entire .period, arid still continues in that position. This mine is a typical Butte mine, operated through a standard four-compartment shaft, served by a double drum hoist and an auxiliary hoist. The texture of the ground and ore has all the variations from soft to very hard granite and sulfide ore with production from levels between the

Jan 1, 1930

By William Kelly, F. H. Armstrong

The object of this paper is to describe the electric equipment at the iron-ore mines of Penn Iron Mining Co., Vulcan, Mich. and of Republic Iron Co., Republic, Mich.; to give the results of tests; and to discuss the methods in use from an operating as well as from an efficiency standpoint. Electricity was introduced at the Penn mines for pumping, hoisting, and compressing air in the spring of 1907, upon the completion of a hydro-electric plant built by that company on the Menominee river about 4 miles from the mines. This plant was described in a paper1 presented before the Lake Superior Mining Institute. A paper2 presented at a meeting of the same Institute describes some of the operating features, and the safety devices of the electric hoist at the Curry shaft were briefly described in the Proceedings of the First Co-operative Safety Congress held under the auspices of the Association of Iron and Steel Electrical Engineers at Milwaukee, Wis., Sept. 30 to Oct. 5, 1912. Generating PoweR Plants After the success of electrical operation was assured, a second set of water wheels and generator was installed at the falls, for which provision had been made in the original design and in the construction of the foundations, and later three additional wires were added to the main transmission line, doubling its capacity and reducing the line loss. The general conditions of this installation are particularly favorable for hydro-electric operation. In the neighborhood of three-fourths of the power used is for mine pumping, which in the main is regular and continuous. For air compressing, power is used for about 18 hr. a day for five days, and 9 hr. for one day in the week, though occasionally when shaft sinking is going on a very small amount of compressed air may be

Jan 1, 1915

By Reno Sales

THE present-day application of geological knowledge to mine opera-tions owes much to Survey activities. Early publications covering developed deposits at Comstock and Eureka in Nevada, and Leadville in Colorado, aroused great interest in mine geology among mine owners and operators. In later years personal contacts between Survey geologists, notably Lindgren, Spurr, Emmons, Weed, and Ransome, to name only a few, and mine managers, mine superintendents and mine foremen, brought directly home the importance of geological mapping and study in connection with mine operations. However, the Survey had recognized from the beginning that it was not practicable, either from the viewpoint of cost or policy, to supply direct help to the miner. The situation was met by many large mining companies through the organization of geological departments to deal with problems of geology which concerned not alone the every-day mine operation but also the life expectancy of the ore deposit. The mine owner therefore looked to the mine geologist to apply the "laws of ore deposition" in estimating the future of his mine. The examination of outside properties also became a duty of the company geologist where replacements were needed or where expansion of operations was contem-plated. And finally, out of this situation there developed the inde-pendent consulting geologist, specializing in geological examinations of prospects, mines, and mining districts, whose duties included the highly important but often difficult task of appraising ore reserves and ore possibilities. Thus, while it may be considered by many that the work of the mine geologist overlaps that of the Survey geologist, their respective fields of endeavor are not in conflict. The appearance of the mine geologist has lessened in no manner the need of intensive field and research work by the Geological Survey and related organizations.

Jan 1, 1934

By J. R. Long, E. T. Hayes, R. S. Dean, F. S. Wartman

THE production of titanium in 15-1b. lots and with a purity sufficient to be consolidated into ductile metal, as described in a previous paper,1 has provided adequate material for a study of the : physical properties of titanium and a more thorough examination of its working qualities. Data on the physical properties reported in that paper were obtained on metal fabricated by a fixed procedure, standardized for the purpose of control of the reduction, and are representative only of material fabricated under those conditions. There are many possible variables in the working schedule, which will have significant effects on the properties of the finished material; and since the previous working methods were not necessarily the best, an investigation of the fabrication of titanium by other methods was undertaken. In this work the consolidation of the powder by pressing and sintering was conducted essentially as outlined in the report cited' and all efforts were centered on fabrication methods for those powders and the properties produced by them. Hardness, density, microstructure, and tensile properties were determined at various stages in the working and annealing; and resistivity measurements were made on a few bars and drawn wire. [ ] CONSOLIDATION OF THE POWDER The screen analysis of the available titanium powder is given in Table I. No attempt was made to alter the size distribution from that noted because this powder, although coarse by normal powder-metallurgy standards, produced acceptable compacts suitable for the present work. Because of their large specific surface, finer powders are more contaminated by oxygen and produce harder compacts, which are difficult to work. The powder as produced is soft, compresses in a normal fashion, and exhibits very little tendency to adhere to the die surfaces. Unlike aluminum and magnesium powders, it can be readily pressed without the use of die lubricants. When compacted at so tons per

Jan 1, 1946

By J. R. Long, R. S. Dean, F. S. Wartman, E. T. Hayes

The production of titanium in I5-lb. lots and with a purity sufficient to be consolidated into ductile metal, as described in a previous paper,' has provided adequate material for a study of the physical properties of titanium and a more thorough examination of its working qualities. Data on the physical properties reported in that paper were obtained on metal fabricated by a fixed procedure, standardized for the purpose of control of the reduction, and are representative only of material fabricated under those conditions. There are many possible variables in the working schedule, which will have significant effects on the properties of the finished material; and since the previous working methods were not necessarily the best, an investigation of the fabrication of titanium by other methods was undertaken. In this work the consolidation of the powder by pressing and sintering was conducted essentially as outlined in the report cited' and all efforts were centered on fabrication methods for those powders and the proper- ties produced by them. Hardness, density, microstructure, and tensile properties were determined at various stages in the working and annealing; and resistivity measurements were made on a few bars and drawn wire. Consolidation of the PowdeR The screen analysis of the available titanium powder is given in Table I. No attempt was made to alter the size distribution from that noted because this powder, although coarse by normal powder-metallurgy standards, produced acceptable compacts suitable for the present work. Because of their large specific surface, finer powders are more contaminated by oxygen and produce harder compacts, which are difficult to work. The powder as produced is soft, compresses in a normal fashion, and exhibits very little tendency to adhere to the die surfaces. Unlike aluminum and magnesium powders, it can be readily pressed without the use of die lubricants. When compacted at 50 tons per

Jan 1, 1946

By J. R. Long, E. T. Hayes, R. S. Dean, F. S. Wartman

The production of titanium in I5-lb. lots and with a purity sufficient to be consolidated into ductile metal, as described in a previous paper,' has provided adequate material for a study of the physical properties of titanium and a more thorough examination of its working qualities. Data on the physical properties reported in that paper were obtained on metal fabricated by a fixed procedure, standardized for the purpose of control of the reduction, and are representative only of material fabricated under those conditions. There are many possible variables in the working schedule, which will have significant effects on the properties of the finished material; and since the previous working methods were not necessarily the best, an investigation of the fabrication of titanium by other methods was undertaken. In this work the consolidation of the powder by pressing and sintering was conducted essentially as outlined in the report cited' and all efforts were centered on fabrication methods for those powders and the proper- ties produced by them. Hardness, density, microstructure, and tensile properties were determined at various stages in the working and annealing; and resistivity measurements were made on a few bars and drawn wire. Consolidation of the PowdeR The screen analysis of the available titanium powder is given in Table I. No attempt was made to alter the size distribution from that noted because this powder, although coarse by normal powder-metallurgy standards, produced acceptable compacts suitable for the present work. Because of their large specific surface, finer powders are more contaminated by oxygen and produce harder compacts, which are difficult to work. The powder as produced is soft, compresses in a normal fashion, and exhibits very little tendency to adhere to the die surfaces. Unlike aluminum and magnesium powders, it can be readily pressed without the use of die lubricants. When compacted at 50 tons per

Jan 1, 1946

By Lester A. Blackner

The Ray Consolidated Copper Co.'s mining property is located on Mineral Creek, 6 miles north of Kelvin, at Ray, Pinal County, Ariz. (Fig. 1). The mining claims now owned by the company consist of 126 lode claims, comprising 2,144.9 acres, containing at the beginning of operations 82,904,368 tons of 2.19 per cent. copper ore. General Characteristics of the Orebody The main orebody is a disseminated deposit in schist and porphyry formed by secondary enrichment. Its existence was proved by churn drilling, and it is at present one of the largest proved copper deposits in the world. The orebody itself covers 205 acres with an average thickness of 121 ft., and occupies a definite belt which has a northwest direction. Its length is approximately 5,000 ft. The width varies, being about 2,000 ft. at the west end and 2,500 ft. at the east, narrowing down irregularly from both ends to a few feet in the center. The thickness of the body varies greatly along the line of lode, ranging from a few feet up to 470 ft. thick. The ore horizon is not constant, but varies, following in a broad sense the topography. The body in general dips slightly to the northeast, and is broken up by numerous small faults and fractures. The ore-bearing formations, consisting of mineralized schist and mineralized granite porphyry, stand fairly well and offer no difficulty in mining operations. The bulk of the ore is chalcocite disseminated in schist. In places cupriferous pyrite is closely associated with the chalcocite. The mineralized gr'anite-porphyry forhations are contiguous to the ore-bearing schist. • Overlying the orebody is an oxidized zone of leached iron-stained schist, averaging 252 ft. in thickness, termed "capping." The Line of

Jan 1, 1916

By Robert Mehl

THE purpose of this investigation was to prepare high-purity iron-carbon alloys, to determine as precisely as possible the A3(GOS), the Acm(SE), and the A1(PSK) transformation temperatures in the meta-stable iron-iron carbide system (up to 1.4 per cent C), and to study the influence of carefully controlled and constant rates of heating and cooling (1/8 to 2° C. per minute) upon the transformation temperature and upon the resulting microstructure. Apart from the general metallurgical importance attending the completion of such a task, it will be noted that highly precise transformation temperatures are of interest and importance in the thermodynamic study of this system1. Several determinations of the iron-iron carbide diagram have been made. These suffer generally from the low purity of the alloys used, and from the application of methods of investigation of low sensitivity. Attempts to compare and weight the many data available in an effort to construct as accurate a diagram as possible have, in the main, been unsuccessful. In general, the wide differences in the results of different workers, the lack of complete analytical data, the omission of important details relating to the heat-treatment of the alloys, and the meager description of the methods of investigation applied, render such a process of averaging nearly meaningless. It may be seen from the summaries by Epstein2 and Körber and Oelsen1 that variations as great as 30° C. exist in the reported data on the A3 temperatures in iron-carbon alloys. For-tunately, the A3 temperature in pure iron is now known to be 910° C. ± 1° C.3 The best recent work on iron-carbon alloys is that of Esser4 on hypoeutectoid steels and that of Sato' on both hypoeutectoid and hyper-eutectoid steels.

Jan 1, 1937

By Blake M. Loring

Recently the S-curves for 30 to 40 alloy steels have been pub1ished.l.2 These steels show individual characteristics, which make each additional S-curve of great interest. There are important differences in the mechanism of the transformation process, the type of transformation product, and the influence of alloying elements. Steels of the same general alloy composition may possess such variable characteristics with regard to the length of time of isothermal transformation that an S-curve for each heat of steel may be desirable. In the present work the isothermal transformation of a steel having the following composition and grain size was studied: 0.29 per cent carbon; 0.21 manganese; 0.026 phosphorus; 0.017 sulphur; 0.056 silicon; 1.45 chromium; 3.25 nickel; austenite grain size, 7. The progress of the isothermal transformation was followed by several different methods, including hardness measurements, dilatometer observations, and examinations of the microstructure. It was not expected that these methods would be in precise agreement.3 Accordingly, the changes in microstructure and hardness were given additional weight in determining the initial stage of transformation and the dilatometer measurements were relied on in estimating the completion of the process. The beginning of transformation was indicated by I per cent of transformation products and the end of transformation by about 99 per cent. The reproducibility of the various methods in the ranges of highest sensitivity was checked by several observations at each time and temperature. The steel used in this investigation was annealed for 24 hr, at 925°C. Macroetching revealed no serious segregation. The specimens for the metallographic and hardness investigations were 1¼ by ½ by ? in. Wires attached to the samples were used for handling. instead of tongs, to avoid chilling. The specimens were heated at 845°C. for ½ hr. and quenched into constant-temperature salt baths held at various temperatures from 205' to 650°C. The time required to transfer the specimens was found to be about 1½ sec., and nearly 5 sec. more was required for them to come to the temperature of the bath. After various lengths of time in the constant-temperature baths the specimens were quenched in water at 2I°C. The specimens were cut in half for the metallographic examination, to provide a surface free from decarburization. To determine the beginning and end of the transformation the percentage of transformation determined metallographically and by hardness was plotted against time. A planimeter was used in the metallographic determination. The hardness and metallographic determinations made at room temperature were confirmed reasonably well by dilatometer measurements taken during the process of transformation at the various temperatures. Two dilatometers were used to

Jan 1, 1942

By Blake M. Loring

Recently the S-curves for 30 to 40 alloy steels have been pub1ished.l.2 These steels show individual characteristics, which make each additional S-curve of great interest. There are important differences in the mechanism of the transformation process, the type of transformation product, and the influence of alloying elements. Steels of the same general alloy composition may possess such variable characteristics with regard to the length of time of isothermal transformation that an S-curve for each heat of steel may be desirable. In the present work the isothermal transformation of a steel having the following composition and grain size was studied: 0.29 per cent carbon; 0.21 manganese; 0.026 phosphorus; 0.017 sulphur; 0.056 silicon; 1.45 chromium; 3.25 nickel; austenite grain size, 7. The progress of the isothermal transformation was followed by several different methods, including hardness measurements, dilatometer observations, and examinations of the microstructure. It was not expected that these methods would be in precise agreement.3 Accordingly, the changes in microstructure and hardness were given additional weight in determining the initial stage of transformation and the dilatometer measurements were relied on in estimating the completion of the process. The beginning of transformation was indicated by I per cent of transformation products and the end of transformation by about 99 per cent. The reproducibility of the various methods in the ranges of highest sensitivity was checked by several observations at each time and temperature. The steel used in this investigation was annealed for 24 hr, at 925°C. Macroetching revealed no serious segregation. The specimens for the metallographic and hardness investigations were 1¼ by ½ by ? in. Wires attached to the samples were used for handling. instead of tongs, to avoid chilling. The specimens were heated at 845°C. for ½ hr. and quenched into constant-temperature salt baths held at various temperatures from 205' to 650°C. The time required to transfer the specimens was found to be about 1½ sec., and nearly 5 sec. more was required for them to come to the temperature of the bath. After various lengths of time in the constant-temperature baths the specimens were quenched in water at 2I°C. The specimens were cut in half for the metallographic examination, to provide a surface free from decarburization. To determine the beginning and end of the transformation the percentage of transformation determined metallographically and by hardness was plotted against time. A planimeter was used in the metallographic determination. The hardness and metallographic determinations made at room temperature were confirmed reasonably well by dilatometer measurements taken during the process of transformation at the various temperatures. Two dilatometers were used to

Jan 1, 1942

By Donald T. Hawkins, Ralph Hultgren

The lorsion effusion method has been used to measure the vapor pressure of lead over pure lead and eight Pb-Sn alloys ranging from 9.1 to 87.9 at. pct Pb in the temperature range 950° to 1125°K. The resulting ?H°y 298 = 46,630 ± 200 cal per g-atow for pure lead is in excellent agreement with previous work. Deriued ?Gph values for the alloys were smoothed and correlated with previous heat of formation data to obtain entropies for the liquid alloys. values for the tin component were calculated by Gibbs-Duhem integmtion. Surfhce depletion of these liquid alloys was found to be absent, as shown by the fact that the measured pressure remained substantially constant with time in contrast with previous measurements on iron-rich solid Fe-Mn alloys. The activities and Gibbs (free) energies of the liquid Pb-Sn system are not well known although the heats of formation have been accurately determined by K1eppa.l Vapor pressure determinations of the activity of lead by Voronin and Evseev2 disagree with those of Predel.3 Elliott and chipman4 measured activities by the electromotive -force technique in the ternary Pb-Sn-Cd system. From the resulting values of the activity of cadmium, they were able to calculate the activities of lead and tin for the binary Pb-Sn system at the compositions xsn = 0.33 and 0.67. Atarashiya, Uta, Shimoji, and Niwa5 determined the activity of tin from Hz-H2O equilibrium measurements, but their results are subject to question due to uncertainty in the final state of their samples. To resolve these differences, measurements of the activity of lead were made using a torsion-effusion apparatus. Among other advantages, this apparatus rapidly detects errors caused by surface depletion, which tends to reduce the apparent vapor pressure of the more volatile component. If the measured torques remain nearly constant with time, only bulk depletion is occurring. This contrasts with the rapid decrease in torque found in solid Fe-Mn alloys at high temperatures and low manganese contents.6 EXPERIMENTAL 99.999+ pct Pb was obtained from the American Smelting and Refining Co. and 99.999 pct Sn from Vulcan Detinning Co. Eight Pb-Sn alloys were prepared by melting together weighed amounts of the pure metals in evacuated Pyrex tubes and quenching the melts in water. Loss of weight in preparation was less than 0.02 pct in all cases. The effusion cells were made from high-purity, nonporous graphite. Graphite was chosen because of its resistance to reaction with lead and tin and because it can be accurately machined with precision orifices. Two cells were used with overall dimensions as shown in Fig. 1. The orifices of cells 1 and 2 were, respectively, 1 and 1.5 mm in diam.

Jan 1, 1968