Search Documents

By B. O. Pickard

WITH more than a score of shafts and numerous stope openings to the surface, all inter-connected underground; with underground temperatures high, often exceeding 100° wet bulb; with an ore presenting a dust health-hazard; with certain rocks giving off inert gases; with an altitude of 6000 ft. above the sea level and a dry desert climate, the Tonopah mines offered an interesting, problem to the student of metal-mine ventilation. Tonopah is not an old mining district relatively speaking. It was discovered in 1900 and Tonopah soon was a boom camp. By 1910 the mines of this district had paid many millions of dollars in dividends. At the time of the 1921 ventilation study, mining had passed its peak of production and the operators were striving to reduce costs, to discover new ore bodies, and to attract desirable workmen. In 1925, the camp was operating on a still less prosperous basis, but the several managements had not relaxed in their efforts to keep the mines on a paying basis, neither had they lost their faith in the ability of the mines and the price of the silver to "come back." Early in the fall of 1921 the Bureau of Mines was invited by the mine operators at Tonopah, Nevada, to make a detailed study of the under-ground air conditions in the Tonopah silver district. D. Harrington,? who was then directly supervising the ventilation studies of the bureau, detailed district engineer B. 0. Pickard, mining engineer E. D. Gardner, surgeon C. E. Kindall, and petrographer H. Insley to carry on the study. G. S. Rice, as chief mining engineer of the Bureau of Mines, was in general charge of the work. Upon the completion of the study each operator was furnished a report on conditions in his mine.

Jan 2, 1927

By W. S. Ayres

THE boiler from which these stay-bolts have just been obtained was that of the locomotive Catasauqua, Lehigh Valley Railroad, built at the company's shops, South Easton, Pa., in 1864. The iron is Lowmoor, and has been in use nearly ten years. The stay-bolts have become highly crystallized from some cause, and are very brittle, only requiring three blows of an ordinary machinist's hammer to break them. On the other hand, when annealed they are remarkably tough, as shown by the doubled sample. The majority of the broken bolts were found to be along the curve of the shell from a to c, Fig. 6. All of them were broken just inside the shell, and in no case next the fire-box. The fractures seen to have been of slow procedure, beginning at the top of the bolt, gradually working deeper and deeper until the pressure of steam overcame the tenacity of the remaining parts. Unequal contraction and expansion of the parts of the boiler seems in this case to be the only existing cause for a fracture. We cannot, from the data obtained, prove to an absolute certainty the manner in which the combined forces generated by the unequal contraction and expansion of the parts have arrived at their resultant work ; but we can, from these data and from existing circumstances, arrive at what seems to be a fair supposition, and thus at least anticipate the truth. The contraction and expansion in locomotive boilers has a large range between its extremes, and is very variable, both with reference to time and to their component parts. The shell and fire-box do not, perhaps, at any time, contract and expand at the same rate, nor proportionally ; but, on the contrary, owing to the great changes in temperature that take place both in the atmosphere around the shell, and in the fire in the fire-box, their condition is often changed suddenly, and widely from that which they just previously had. This racking tendency produces strains in the different parts, and it is fair to suppose that the continual motion of the two

Jan 1, 1874

By Donald W. Gentry, John F. Abel

This paper presents some of the results of a rock mechanics instrumentation program designed for, and implemented at. longwall panel 4N at the York Canyon Mine near Raton, New Mexico. The objective of this particular instrumentation program was to determine the response of the rock mass to longwall mining of a thick coal seam utilizing shield-type supports. Measurements were made in the rock along the ground surface, above the coal seam, in the coal seam, and immediately below the coal seam. Longwall test panel 4N had a total developed length of 762 m (2500 ft) and a face width of 168 m (550 ft), [Fig. 1]. The seam mining height in the panel area was approximately 3 m (10 ft). The average depth of overburden above the panel is 107 m (350 ft) although it ranges from 73-134 m (240-440 ft). Roof support at the face was provided by 116 Hemscheidt 320 HSL shields. These shield-type supports weigh 11.4 metric tons each.

Jan 1, 1979

By Fred C. Bond

IN crushing and grinding the larger particles are more exposed to the work input. They absorb most of the work and protect the smaller neighboring particles from destructive contact with the crushing surfaces or grinding media. The importance of this exposure differential upon the reduction efficiency and product size distribution has long been recognized. Unfortunately, there has heretofore been no direct method of evaluating it, and such indirect methods as observing the slope of the plotted product size distribution line have been used as an indication. In this presentation the Third Theory of Comminution' has been used, together with the exponential formula for size distribution, to evaluate the ex- posure ratio and exposure constant and to illustrate examples of their utility in crushing and grinding applications. The exposure ratio Er varies from zero to unity. It is zero when the product particles are all of one size, and it is unity when the work input has been equally distributed among all particle sizes. It can readily be found from screen analyses plotted according to the Third Theory. The exposure constant K is derived from the reciprocal of the exposure ratio Er. It permits more consistent predictions of size distributions and evaluation of many factors concerned in size reduction operations. The Third Theory1 states that the specific work input required for size reduction is inversely proportional to the square root of the product size less the work required to form the feed. When P represents the diameter in microns which 80 pct of the product passes, F is the size 80 pct of the feed passes, Wi

Jan 1, 1958

By George A. Bell

The mine and milling plant of Demonstration Gold Mines, Ltd., is near the city limits of Baguio, Mt. Province, P. I. The mine road connects with the main highway to Manila. The nearest railway point is near sea level, approximately 40 miles distant. The Baguio district is very mountainous and has one of the heaviest rainfalls in the world. It is therefore difficult to maintain roads or to impound tailings and mine dumps. All supplies are trucked into the district direct from Manila or the nearest railway point, which means uncertain deliveries and high freight rates. Installation of equipment is difficult and costly. The average elevation at the mine is 4000 ft. and the climatic conditions are ideal except for a three months rainy season. The company generates its own power for mining and milling operations with three 400-hp. Ruston Diesel engines direct connected to 250-kw. General Electric alternating current generators. Labor conditions have been excellent, although at present social security laws are causing some unrest. Labor receives a higher average wage rate in this district than other labor in the Islands. The company also furnishes free living quarters, hospitalization and workmen's compensation. Taxation has been reasonable up to the present time, but some of the new mining legislation may make it difficult to operate and pay dividends. The future depends largely upon the continuation of $35 gold and the political outcome in the Islands. History The Demonstration ore body was worked by the Igorots for many years, as evidenced by old stopes and fill encountered in present operations. Attention of Americans was first attracted soon after the Spanish-American war. During the building of the Benguet road to Baguio, the engineers and foreman became interested in the geology of the district.

Jan 1, 1939

By H. Vance

In 1932, as in 1931, the East Texas area outside the Gulf Coast exerted ' its influence over the entire petroleum industry. Practically 60 per cent of the oil wells completed in the United States during 1932 were in this area, development being chiefly confined to the East Texas oil field in Upshur, Gregg, Rusk, Smith and Cherokee counties. This East Texas area is geologically an interior salt dome basin, along the western edge of which are located the fault line fields as represented by Mexia and Powell. Production occurs on salt domes in the interior of the basin as represented by Boggy Creek and possibly Van, although no salt has actually been discovered in drilling at Van. Shore line conditions on the east side of this basin along the flanks of the Sabine uplift have been responsible for the East Texas oil field. Many known salt domes in the center of this basin have been tested but as yet have failed to produce oil in commercial quantities. The main producing horizon throughout the area is lowermost upper Cretaceous and is known locally as the Woodbine sand. The East Texas Oil Field Development.—Approximately 6000 producing wells were completed during the year in the East Texas oil field. No accurate estimate of the total initial production of these wells is available because few initial production tests were made as the wells were completed. The writer estimates the average initial production of these completed wells at 2500 bbl. per day while flowing wide open through tubing. Based on this estimate, the total initial production of the wells completed during the year is 15,000,000 barrels. At the close of 1932 there were approximately 9500 completed wells in the East Texas field. Of this number 176 were without pipe line connections. The oil produced from these unconnected wells could be marketed for $0.30 per barrel while the price paid for oil run from the connected wells was $0.75 per barrel.

Jan 1, 1933

By H. Ries

IN THE marketing of mineral products, it is always highly desirable for both the producer and the consumer to be able to discuss things in a common language, and this can only be done if there are standard methods for expressing the properties of the raw materials. Having developed such a form of expression, the next step would be the making of specifications, which may serve as a basis for selecting raw materials. Considering the large number of non-metallic minerals that are used, there are not a few for which there are no standard laboratory tests to be used in determining their properties, or even standard specifications on which grades or market price may be based. Indeed in many cases the consumer simply requests the producer to submit samples, and rejects or accepts them without any explanation. Could the producer know in advance just what the consumer needed, time and money might often be saved. It appears to the writer that it is of the highest importance to devise standard laboratory tests wherever possible, as this enables the consumer to state definitely what he needs, and is of great assistance to the producer. It should also work to reduce misunderstandings and disputes. 'In the case of sands, we find that they show a wide variation in their character, ranging from those that are so coarse as to be of gravelly nature to those that are so fine that they might be classed as silt; and from very clayey ones to those that are practically free from clay. For this wide range of sands, we have a corresponding variety of uses, which are based mainly on the physical properties of the sand, although these are not always very definitely stated. The chemical composition need rarely be considered, if the sand is of siliceous nature. To determine and express these properties there should be standard tests, which are to be followed in all cases where the material is tested in the laboratory.

Jan 1, 1926

By Eben E. Olcott

The Mine.—For some years attention has been drawn to the copper deposits of the Appalachian range of mountains, and especially to those in that portion crossing the corners of Virginia, North Carolina, and Tennessee. Certain it is that in many places in this locality available deposits of copper await the miner, and one after another are being opened and worked. The parts of these three States alluded to are but sparsely settled, and communications are insufficient to meet the demand for transportation. Railroads are wanted, as the existing wagon roads are unfitted for heavy hauling; these circumstances increase very much the difficulties in the way of mining enterprises. Notwithstanding this, the success of some of the mines of this section is an established fact, and Ducktown has for some years held a high rank among the copper-producing localities of the United States. of all these deposits, however, none is more interesting or more deserving of attention than the one now under consideration. The works of the Ore Knob Copper Company have been energetically pushed forward, since the reopening of the mine, in the spring of 1873, by Mr. J. E. Clayt,on, the superintendent and one of the chief owners of the property, and if one thing more than another can insure success it is the combination in this gentleman of rare business capabilities with the deepest personal interest in the prosperity of the undertaking. The copper vein at Ore Knob* is a clearly defined fissure traversing the gneissic rocks of Pre-silurian age in a direction 61' east of north.

By T. R. Braithwaite

The brief comments made in this chapter deal mainly with shaft sinking, but don't assume that freezing techniques apply only to shaft sinking. They can be used on tunnel work, on such things as liquid gas storage in sediment, and I think you will probably see other applications for it as we go along. The method was first developed in 1883 and was used to sink shallow shafts through water-bearing overburden in Germany and in England. One of the early shafts was in Germany and was sunk by freezing to 310-ft depth. The project required 17 months for drilling, roughly 5 1/2 months for freezing, and another 7 months for sinking, giving an average progress of 10 ½ fpm. Fortunately there have been numerous improvements and new developments in this technique through the years. With equipment and techniques available today, we can take a 20-ft-diam shaft down through 2000 ft of water-saturated overburden and the time schedule runs roughly 4 months for site preparation, freeze-hole drilling, installing the casings, and setting up the plant; 4 ½ months for freezing; and 6 months for excavating and installing permanent linings. This gives a progress rate of about 140 fpm, on average. I might qualify that a little in that the special linings that are required for some formations can affect the time. If it's straightforward sinking where one can use a heavy concrete lining, up to 630-640 fpm may be achieved in a shaft; but with special cast-iron tubbing or types like that, 5 fpd is pretty good progress, so the lining does affect the time. The freezing method is used mainly for sinking shafts through unstable water-bearing formations which cannot be grouted either effectively or economically and which are too deep to enclose in pile casing. Even with overburden, grouting methods available today can handle roughly 100 lb water pressure; in the range of, say, 100 to 150 ft from the surface, it's very often best to grout 40 or 50 ft. You normally drive a pile casing and go through it. Below that range, freezing is very often the economical

Jan 1, 1970

By Olof Löfgren

PART 1 INTRODUCTION All modern pelletizing plants are equipped with either the drum or the disc circuits. Choice of one or the other circuit is not simple and it is desirable to establish a firm basis for such a task. For a meaningful and a fair comparison it is necessary to have the two systems working in parallel in the same plant with the same concentrate under the same supervision. Furthermore, the comparison has to be based on a defined green ball quality and size distribution. BALLING CIRCUITS The LKAB straight grate plant at Malmberget, Sweden, was started up in Septenber 1973. It was designed for a 2.5 Mton annual capacity and was equipped with five balling drum circuits. During the first year of operation it was found that the induration plant had the potential for a higher capacity which required increased balling capacity. For this purpose it was decided to install a balling disc circuit complete with a roll screen. The reasons for selecting a disc were space limitations and LKAB's desire to gather experience on balling disc circuits. The disc circuit was started up in 1975 and was run in parallel with the balling drums in the same plant and with the same raw material and under the same operating personnel. The necessary conditions for a comparison were thereby fulfilled. The data for the size distribution and quality of the green balls were obtained on random sampling during one year of operation, so that all the variations which appear in a commercial plant are covered.

Jan 1, 1977

By V. W. Buys, R. E. Havener

11.3-1. Basic Principles. Communications systems available for application to surface mining operations can be divided into basic categories. These are: 1. Wired systems requiring some type of metallic conductor 2. Nonwired systems, or those commonly referred to as space-radio systems. Under the heading of wired systems, telephones of the ringer type utilizing magnetos were used in the early pit operations. These are still being used in underground mining operations where calling is accomplished by ringing a code made up of short and long rings. While the standard Bell Telephone Systems have not been applied extensively in underground mining, they have been used in open pit operations but have the disadvantage of using multiple pair cables which must be installed and maintained as the mining operations proceed. They have the advantage however, that when a Bell System is installed in a surface mining operation, communication is available not only within the operation but to any point in the world through the facilities of the world-wide Bell Systems. A second type of communication available is the audio system or public address system requiring the use of a special audio cable made up of shielded pairs for the loudspeaker and microphone circuits. Audio systems have one outstanding advantage over most telephone systems in that, with a high-powered amplifier, a paging call can be heard over and above the high ambient noise conditions usually found at a surface mining operation. However, they have the disadvantage of requiring special cable which must be installed and maintained. Another type of wired communication system available for surface mining is that of carrier frequency equipment similar to that used in underground mining operations. In this system, transmission is accomplished by means of a frequency modulated carrier that travels over the underground trolley wire, the rail on which locomotives travel, and adjacent telephone wires.

Jan 1, 1968

By George S. Barnett

The Equis and El Roble projects are located in the Cordillera Occidental of Colombia. The Equis vein deposits have sulfide ore reserves of 95,955 mt (105,770 st) grading 8.51 g/mt (0.248 oz/st) gold and 12.4 g/mt (0.36 oz/st) silver with 0.94 % copper, 1.10 % lead and 11.06 % zinc. Ore reserves at El Roble are estimated as 1.1 Mmt (1.21 million st) grading 4.89 % copper and 3.39 g/mt (0.099 oz/st) gold. Geologically possible reserves at Equis may total 1.6 Mmt (1.76 million st). El Roble has the potential to contain several tens of millions of metric tons. Exploration included diamond drilling, trenching, channel sampling, rock and soil geochemistry, geophysics and tunneling. Erratic high grade samples affect the weighting of channel and drill core samples. Secondary reconcentration of gold is also a factor. Sample maps and graphs show the distribution of values to be highly variable. Geostatistical treatment of some of these data gave important guidelines for parameters such as sampling densities, drill hole spacing and confidence limits.

Jan 1, 1985

By A. R. Troiano, W. J. Barnett

The existence of a grain size stabilization effect on martensitic type reactions as shown by Scheill in an iron-29 pct nickel alloy and by Troiano and Tokich2 in cobalt prompted a review of other martensitic reactions to determine if this stabilization effect is characteristic of all martensite type reactions. Preliminary work has shown this effect to be present both in the gamma —+ epsilon transformation in an iron-20 pct manganese alloy and the martensite transformation of SAE 4140 and 3 pct Cr-O.40 pct steels. No appreciable effect was found in an SAE 2340 steel. The M, temperature for the gamma —+ epsilon transformation was lowered from 380°F to about room temperature by varying the annealing treatment following cold work as shown in Table I. The effect of austenitic grain size on the M, of three steels is shown in Table 2. M, was deter- mined by the conventional quench-temper method of Greninger and Troiano. In a single crystal the change in external shape concomitant with the homogeneous shear mechanism of the martensite transformation can take place unhindered. In a polycrystalline specimen a restraint of these changes must occur at the grain boundaries. Therefore, the smaller the grain size the greater the shear strain energy necessary for the formation of a martensite crystal. The degree of lowering of M, due to the reduction of grain size is much greater when the change in crystal structure involves only a small energy change, such as face-centered cubic —+ close packed hexagonal (that is, CO and Fe-20 pct manganese alloy). The maximum lowering of M, observed in the steels investigated was 50°F with a change in the ASTM austenitic grain size of 1-2 to 8-9. In comparison, the crystal structure change face-centered cubic —+ body-centered tetragonal involves a considerable energy change. There is little doubt that with much finer grain sizes the increased grain boundary restraint would greatly enhance this stabilization effect. The implications of this phenomenon are multifold. Undoubtedly. under certain conditions it offers a method of stabilizing high temperature phases for room temperature

Jan 1, 1949

By B. B. Zavoico

There were no radical changes in the petroleum situation in the Russian Soviet Union during the 1926 to 1927 operating year. The developments of the previous year were continued, but the major undertakings were far from being completed. The pipe lines from Baku to Batum and from Grozny to Touapse, and the large refineries on the Black Sea are delayed in their completion by the insufficient authorizations; until their completion the changes in the general situation will be necessarily of a halfway nature. The marketing situation was subject to much controversy during the past year and, though certain statements are quite true, the bulk of the criticism against the petroleum industry hardly deserves mention. The home market in Russia is steadily growing, with the per capita kerosene consumption already exceeding the prewar figure and fuel oil consumption obviously gaining. The foreign trade is making rapid and well-grounded success, but continues to suffer from low world quotations. There is no apparent sacrifice of home consumers in favor of export trade. The production of all Russian fields increased by 13,750,000 bbl. as compared with the 1925 to 1926 operating year, and next year's program anticipates a further increase of 9,720,000 bbl. (Table 1). The increased and improved refining facilities will make the real gain in production in the next year even larger than these figures indicate.

Jan 1, 1928

By Thomas S. Nye

Mineral exploration in the United States relies heavily on theoretical geologic concepts and indirect methods such as geophysics and geochemical prospecting, as there are few exposed areas of mineralization which have not already been explored. In Mexico, ore grade samples can be cut at the surface on vein, replacement, and disseminated types of deposits in many areas. The problem is not in finding a mineralized area but in deciding which mineralized area can be explored and developed at the least risk and cost, with the greatest profit potential within the framework of Mexican mineral economics and that nation's government policies. Socio-economic Posture Mexico, prior to World War II, had suffered from more than one hundred years of intermittent wars and exploitation by internal and foreign elements. Consequently, the basic facilities which today's society takes for granted were scarce or non-existent in most of the country. Travel was largely a matter of negotiating poor dirt roads, riding horseback or walking. Relatively few people were literate and medical facilities were luxuries for the wealthy. Mexico's leaders were, however, determined to improve the lot of their people, within a system of private enterprise and personal freedom. Long-range programs initiated at about the time of World War II to provide infrastructure-education, health and welfare, transportation, power, water, communication-are now established fully or in part for most of the country and are being continually expanded.

Jan 12, 1972

By Clyde E. Williams

The purpose of this report is to supply the Coal Classification Committee' with information for use in the formulation of a system of classification of coals according to their uses. Consideration is given here only to the nonferrous metallurgical operations that consume relatively large amounts of coal or coke; i. e., the smelting of copper, lead, zinc and aluminum. For all of these uses, coal of certain definite qualities is desired. Geographical location, however, often determines whether these qualities can be specified. In some instances the preferred qualities must be specified, regardless of cost. In others, quality may be sacrificed for lower cost, although the best quality consistent with cost is usually the determining factor. These considerations will be outlined in the following discussion under the various uses, which, however, will illustrate the impracticability of preparing definite specifications for coal used in the majority of the nonferrous industries. Coal and Coke in Copper Metallurgy From the standpoint of coal consumption, copper smelting and refining operations are the most important of the nonferrous metallurgical uses of coal. As nickel ores treated in the United States and Canada are associated with copper, the first step in their recovery is really a copper-smelting operation; accordingly, the following considerations under copper smelting apply equally to nickel. Copper Smelting in Reverberatory Furnaces.—For a long time, rever-beratory copper-smelting furnaces were fired with lump coal burned on grates in a fire box. Later, lump coal was displaced by pulverized coal or oil burned directly in the smelting chamber. Recently, natural gas has been used in several plants, although producer gas was used for this purpose at Great Falls as early as 1903.2 Requirements for coal used in

Jan 1, 1932

By A. J. Strane

PRACTICALLY all explosives may be classified as those that burn and those that detonate. Explosives of the first class include .black blasting and smokeless powder and are broadly known as low explosives, or propellants, because they merely burn and do that comparatively slowly. Their action is as if some power behind the projectile or other material were exerting a shoving or pushing action. The high, or detonating, explosives produce a smashing or shattering effect upon the material. In using military- explosives of the propellant class, the breach of the gun, or cannon, is proportioned to hold the pressure, so that the projectile will be blown out. Exactly the reverse is true in commercial work; then it is the "breach" or the hole that is to be broken. The projectile and the explosive are therefore chosen that will rupture the largest "breach" possible. With the high explosives, it is easy to break out the breach (that is why they are of no value as military propellants)" but with some of the low explosives it is necessary to plug up the muzzle very carefully before shooting. Doubtless the use of incendiary mixtures of oxidizing and combustible materials led, in the 13th century, to the perfection of the mixture which is practically the same as our commercial black blasting powder of today. About 600 years later, nitroglycerine was discovered, but for years its great potential energy could not be used because, in its liquid state, it could not be safely handled or transported. The accidental discovery that kieselguhr would absorb, and hold fairly well, three times its own weight of nitroglycerine, however, made it available. "Guhr dynamite," as the combination nitroglycerine and kieselguhr was termed, was soon displaced by dynamites having an active base, such as wood pulp and other carbonaceous combustible materials. These do all that kieselguhr will do and, in addition, increase the chemical reaction and add materially to the effectiveness of the blast.

Jan 8, 1920

By Oliver Bowles

SUPERFLUOUS varieties and standards which are meriting the critical scrutiny of the manufactur-ing industry have a special significance in the non-metallic mining industries, where, many of the final or intermediate products are manufactured at the mine or quarry. Such processes of manufacture must be considered an integral part of mining in its broader sense. Improvements may be either elimination or standardization. - The chief requirement of elimi-nation is an agreement between consumers and pro-ducers based on facts deduced from: statistical data. Standardization is much, more complex. Standards .may be established only when a very; thorough knowledge has been gained of the physical and chemical properties of the products, and the requirements of consumers. The activities of the Bureau of Standards are. largely directed toward such determinations. Paving-brick manufacturers, together with highway engineers, representatives of certain engineering socie-ties, and Government bureaus, have agreed that of the 66 styles of paving brick on the market 11 only are, essential and 55 are superfluous. Steps have been taken to reduce the output of -all but the 11 standard types. It is customary for manufacturers of structural slate to prepare it in sizes specified by builders and architects. Thus the material cannot be manufactured in advance and the result is irregular activity of mills, delays in filling orders, etc. To improve this condition, the Structural Slate Co. has issued a series of pamphlets giving complete specifications of structural slate for various purposes. Architects find it so much easier .to, order slate from these sheets that standard sizes are specified in preparing plans for new structures. Slate switchboards are usually manufactured after. the order has been received. One manufacturer claims that 80 per cent. of all switchboards are of standard sizes, and he keeps such sizes in stock. The facility with which orders may be filled from stock, and the improved quality of seasoned switchboards, will undoubtedly influence electrical, companies toward a more uniform standardization in size. Simplicity, could be further attained by the elimination of minor irregularities in .style; for example, in the beveled. edges.

Jan 2, 1922

By H. l. Burghoff

THE presence of tellurium in copper and, by inference, in copper alloys, has been considered seriously detrimental and has been avoided. In particular, very small amounts of tellurium have been found to produce red-shortness, although the effects on cold-working and ordinary physical and mechanical properties have not been known so definitely. References in the literature are few, but as long ago as 1881, Egleston1 reported that 0.083 per cent tellurium in fire-refined copper rendered the copper red-short and therefore worthless for hot-rolling. In hot-rolling copper cakes containing this amount of tellurium, he found that fine cracks appeared in the cakes on the first pass through the rolls, the cracks opening further in successive passes. When cold, the metal was said to be tough and malleable. A few years ago, during the course of an investigation in our laboratory on copper-base alloys, it was found that tellurium-bearing alloys could be machined much more freely than similar alloys not containing tellurium. The study was pursued further in this direction, and considerable data were obtained, which indicated that certain tellurium-bearing alloys might have properties of commercial interest. The work eventually led to patent protection,2 a wide range of tellurium-bearing copper-base alloys being covered. This article presents results obtained on the effect of tellurium on the. mechanical properties of three copper-base alloys: commercial bronze (90 Cu, 10 Zn), 1.5 per cent tin bronze (98.5 Cu, 1.5 Sn), and silicon bronze (96 Cu, 3Si, 1 Zn).

Jan 1, 1937

By Wilhelm Rohn

When a metal solidifies, gas, initially present in solution, may be concentrated at the grain boundaries, leading to brittleness, or it may form solid compounds which, if localized at the grain boundaries, impair the properties. On the other hand, the solid compounds formed sometimes distribute themselves more or less uniformly, and hence may be relatively harmless. If metallic oxides are heated under a partial oxygen pressure less than that corresponding to the dissociation pressure of the oxide in solution in the melt, they will decompose and oxygen will tend to be eliminated from the melt. This paper presents data on the partial oxygen pressures of copper and nickel oxides over a wide range of temperatures; it also presents data regarding the amount and nature of the gases evolved in the vacuum melting of a 3500-kg. charge of nickel-chromium alloy and gives test values indicating the improvement in impact values ascribed to vacuum melting. The results of commercial experience with a 4-ton vacuum melting and casting furnace indicate that this method entails an increase in cost of about 10 cents per pound of ingot over orthodox practice, which may be justified for special products and may be lowered if hot metal is charged into the vacuum furnace. DISCUSSION (Howard Scott presiding) J. H. ScafF, New York, N. Y. (written discussion).—In the section of Dr. Rohn's paper describing the effect of melting -metals in vacuo, he says, "In this way plain copper, nickel and iron may be easily purified. For example, vacuum-melted copper does not contain any oxygen and for this reason it is never sensitive to hydrogen embrittlement." This statement is contrary to the results of our experiments at the Bell Telephone Laboratories on the effect of vacuum melting on the properties of copper. Several 150-gram samples of tough-pitch copper were melted in a vacuum of the order of 1 X 10-5 to 1 X 10-6 mm. Hg for 2 hr. Portions of the ingots obtained were swaged to 0.100 in., then drawn to wire 0.050 in. in diameter for physical and

Jan 1, 1933