Search Documents

By H. L. Luo, W. Klement

By rapidly quenching Ag-Pt alloys from the melt, a continuous series of solid solutions has been obtained. At equilibrium''2 these fcc elements form a peritectic system, Fig. 1. Weighed amounts of silver and platinum powder (325 mesh, purity greater than 99.9 pct) were mixed for 24 to 120 hr, pressed into compacts, sintered at 1000°C in a hydrogen atmosphere for at least 16 hr, and then furnace-cooled. Because of the difficulty in achieving homogeneity in alloys containing more than about 40 at. pct Pt, the sintered compacts were induction-melted under hydrogen in alumina crucibles and then cold-rolled into wires. Small amounts ("30 mg) of alloys cut from various sections of the sintered compacts or rolled wires were heated to at least 50' ~ above the liquidus in an alumina insert held within an induction-heated graphite crucible; then the molten alloy was ejected by a blast of helium onto a lightly polished copper strip held on the inner periphery of a rotating wheel. The flakes thus obtained were typically 1 sq mm in area or often slightly larger for the silver-rich alloys. X-ray diffraction patterns were obtained with nickel-filtered copper K radiation in a 114.6-mm-diam Debye-Scherrer camera with rotated specimens. Lattice parameters and associated uncertainties were estimated from extrapolations against the Nelson-Riley function. High-angle lines were always resolved and spacings were computed relative to r(CuKa!,) = 1.540508 The details of these techniques have been discussed previously.s'6 Lattice parameters of the solid solutions are plotted in Fig. 2, together with the data of Schneider and Esch,' Johansson and Linde,' and Novikova and pudnitskii. Each of the present lattice spacings represents two or more independent determinations. The alloys were homogeneous within 2 at. pct of nominal composition as estimated from the uncertainties in the lattice spacings. Many of the mechanisms involved in the achievement of metastable solid solutions by rapidly quenching from the melt have been previously discussed. There is some evidence" that such solid solubility cannot be obtained when the liquid alloys are cooled

Jan 1, 1963

By H. F. Moore

AT PRESENT, I am connected with an investigation of the so-called fatigue of metals under stress. So far we have studied the more fundamental and simple case of the repeated stress, without the additional complexity of impact, which might bring in other factors. We feel that this investigation, which has been in active progress for a little over a year, has shown more conclusively than has been shown before that steel under repeated applications of stress, reversed from positive to negative, will not fail below some fairly clearly defined limiting stress that,, so far we can see, does not bear any definite relation to the ordinary elastic limit, being as large as the elastic limit in some cases and about one-half the elastic limit in others. I might be asked, first, what is fatigue. The old view is summed up "in the word "crystallization." The idea was that under repeated stress the material changed its crystalline structure. I do not know of any evidence in favor of the theory that metals materially change their crystalline structure under repeated stress. The crystals are broken under repeated stress. The second theory, advanced by Bauschinger, the German scientist, is that under repeated stress some inherent property of the material changes its elastic limit; it is an inherent property of the material, possibly some property of the amorphous cement between the crystal. The third view is that all fatigue of metals is the result of the spread of damage from little localized overstresses. I do not feel justified in stating my positive belief in the third view as against the second, but I have yet to run across a case of failure of steel or other metal, either in the laboratory or in service, that could not be explained by the gradual spread of damage from some nucleus. We have found, for example, that it is possible to subject a homogeneous steel, like Armco iron or a 0.90 per cent. carbon steel, that hag been thoroughly annealed, to one hundred million reversals f stress as high as the elastic limit of the steel with no sign of failure. We stopped the test at one hundred million because the machines Were required for other work. Forty-five days, continuous running at 1500 revolutions a minute is required to produce one hundred million repetitions. On the other hand, a complex structured steel, like a chrome-nickel steel that

Jan 6, 1921

By Robert A. Brusca

OUTLINE Mineral Poor, but great primary inputs Net importer of most primary inputs • Copper • Zinc • Aluminum • Oil Problems for Japan • Supply Disruption • Currency Swings Remedies • Yen pricing of primary products • Long term contracts • Ownership of primary commodity producers Current Approach No Text Available

Jan 1, 1990

By J. J. Frawley, W. J. Childs

PREVIOUS studies have shown that if a supercooled liquid metal was perturbed by vibration the probability of nucleation is is During a recent investi- gation to determine quantitatively the amount of energy needed to cause nucleation in a given supercooled liquid specimen, it was found that at low-energy values in the megacycle range, below the threshold energy value for cavitation, the amount of dynamic supercooling was greater than the amount of static supercooling. That is, if a specimen had a given amount of thermal supercooling under static conditions, its thermal supercooling could be increased by the addition of low-energy sound waves. The material used in this investigation was high-purity bismuth. This material was chosen because of its low melting point and the high degree of supercooling which could be easily obtained. The sound gener- ator employed in this work was a commercially built Sperry ultrasonic testing unit. This unit was equipped with a barium titanate crystal as a piezoelectric transducer. These sound waves were transmitted to the supercooled melt by a Pyrex rod, as shown in Fig. 1. The transducer was coupled to this Pyrex rod wave carrier by motor oil. The Pyrex wave carrier was approximately 1.5 ft long to prevent damage to the transducer by heat. The diameter of the Pyrex wave carrier appears to be critical. In the initial tests a wave carrier of 0.5 in. in diam was employed. However, the sound waves had no effect on the amount of dynamic supercooling. When the diameter of the wave carrier was increased to approximately the inside diameter of the Pyrex crucible, the sound waves were more effective. Approximately 200 g of metal was melted under a stannous chloride flux in a 30-ml beaker by induction heating. The temperature was recorded by a Pyrex-encapsulated chromel-alumel thermocoule which was placed in the beaker after the bismuth melted. The Pyrex wave carrier was immersed slightly below the surface of the liquid bismuth and the specimen was reheated to about 500°C. It was observed that the amount of supercooling depends on the amount of superheating the specimen receives; therefore, for meaningful results the amount of superheating was the same for all heating cycles. The specimen was allowed to cool in air and the change in temperature was continuously monitored with a potentiometric strip-chart recorder.

Jan 1, 1969

By J. N. Houser

THE industrial relations between the Tennessee Copper Co. and its employees have developed a number of interesting things and have been most, profitable to the employees and to the company. It is noteworthy that considerable has been done without a formal organization of any kind built up through the efforts of the company. From time to time there have been discussions regarding the advisability of a formal organization and the decision has always been in favor of the present method. In the year 1919, the company was dealing with its employees through union committees and, after an understanding was reached, satisfactory results began to be obtained, but as time went on the committees did not function and it came to a question of how to reach the men. For the past two years, about once a month, but at no stated time, there has been a meeting with a committee of employees consisting of 40 or 50 men out of 700. This committee is secured by notify-ing the locals. In addition, the Service Department notifies a number of men not represented in the union, so as to have a large representative committee. The meetings are on company time and the men are rotated, so that in time every employee attends , at least one meeting. All department heads and a number of foremen also are present. The operating plans and policy of the company are set out at the meetings and the market outlook for products is discussed. Explana-tions are also given of anything that has come up since the last meeting which affects the employees, and an effort is made to inform them of what will probably happen in the next month or two. Once a week there is a meeting of department heads with the manager, for discussion of all operations as a whole and such depart-mental details as seem advisable. When the depression started, it was necessary to curtail operations and the reasons were carefully explained; before the men were laid off, the employees as a whole were advised of the coming layoffs through these meetings. They were also advised generally who would be retained and given an opportunity to express their agreement or their. disapproval. In fact, an effort was and is being made to keep the employees advised in advance of matters affecting them and to give them full opportunity to express themselves.

Jan 12, 1922

By Charles A. Mitke

Discussion of the paper by CHARLES A. MITKE, presented at the San Francisco meeting, September, 1915, and printed in Bulletin No. 105, September, 1915, pp. 1941 to 1958. GERALD SHERMAN, Bisbee, Ariz.-Mr. Mitke justly might have made much stronger his claim for increase in efficiency of labor due to the introduction of forced ventilation. The product per man shift in stoping in the Gardner division has practically doubled. While it is true that improved methods have been responsible for a great part of this gain, and what is due to better ventilation cannot be definitely known, yet it is also true that the results could not have been obtained in that division as it was in 1912. . The paper discusses the two systems of ventilation in use, exhaust and pressure. In both the object is the same, to take foul air or gas out of the mine by the most direct course and replace it by fresh. In coal mines, the exhaust system is in almost universal use, and since the most advanced work in ventilation has been in that class of mines, it was naturally the first one to be considered. It has the advantage of leaving all adits, shafts, or other openings free for use. Doors are only needed to direct the course of the air, and not to confine it. Its disadvantages appear in case of fire, or if the ground over the mine is much broken by subsidence. The fan must work in gas in the case of a -fire, and may be. damaged or destroyed either by heat or by corrosive gas. At the time of the fire in the Lowell division of the Copper Queen, a small exhaust fan was placed over a ventilating raise, but the vanes and housing were destroyed by sulphurous gases within a few weeks. If the ground above the mined area is much broken, as is frequently the case when the ore deposit is thick vertically, a good deal of air is likely to pass through it, particularly if it is near the surface. Leakage from this source is a loss to the exhaust system by short circuiting, which is exaggerated by a contraction or block in the air course. It serves as an added outlet in the pressure system. This is strikingly shown at the United Verde, where many jets of steam may be seen coming up through the ground above the stoped country on a cold day.

Jan 12, 1915

By Edmund C. Pechin

I REGRET that I am unable to present this subject in definite form and detail. All I shall attempt at this meeting is to lay before you some curious facts, the bearings and explanations of which must be reserved for future consideration. I hope before the next meeting to have carried experiments far enough to furnish a more important contribution to the science of iron metallurgy. The Wickersham process consists in the introduction into the molten metal, as it runs from the furnace, of air from the hot blast. Mr. Samuel Wickersham is the originator of the plan, as applied in practice, although Mr. Martien had the idea a long time ago, and, I believe, went to England about it. But at that time Mr. Bessemer was coming before the public with his invention, which engrossed the attention of iron-masters, and Mr. Martien accomplished nothing. The principal difficulty in our experiments at Dunbar was to get a practicable runner or trough, through which the molten metal should pass, and in which it should be exposed to the action of the Mast. The runner we used was ten feet long, and perforated on the sides to permit the entrance of the air-currents. When we used a cast-iron and fire-clay runner, the heat was so great that before we were more than half done with a run, the lower part of the runner was melted, and we had a magnificent Fourth of July display of fireworks until the blast was shut off. We had to abandon fire clay. The runner with which we have had the best success is made of wrong- ht-iron tubes, 29 inches in diameter, attached to a wrought-iron frame, and lined with a mixture of crushed conglornerate (quartz) and a little fire clay to give it cohesion. The wrought-iron shell curves inward over the upper edges, so as to catch and throw back into the current the flying sparks and particles of metal thrown out by ebullition. With this we have been able to run 12 to 14 tons at a heat with great ease. Mr. Wickersham has since prepared this material (pounded quartz) into a shaped brick or tile, with the necessary perforations for the passage of the air, which promises to answer every requirement for steady working. As regards the improvement in the quality of the iron, there seems to be no question. A large number of practical tests were made in

Discussion of the paper of L. A. DELANO, presented at the St. Louis meeting, October, 1917, and printed in Bulletin No. 129, September, 1917, pp. 1267 to 1286. L. A. DELANO.-Since this paper was written, our daily mill tonnage has increased, from 2100 tons to 2700 tons a clay. We now use 11,000 lb. of chrome-steel balls of 2 ½ -in. maximum diameter, for an average crushing capacity of 275 tons per 24 hr., this giving a much higher crushing efficiency. I wish to call attention to two typographical errors in my paper as published. On page 1271, Table 1, the screen analysis of ore at the Bonne Terre mill should be stated in inches instead of mesh. - On page 1272, "the rolls average 185 tons per 24 hr., and have shown by test that 250 tons per hour can be maintained" should, of course, read "250 tons per 24 hours." THE CHAIRMAN (0. M. BILHARZ, Miami, Okla.).-Is the increased mill capacity due to improvement in the re-crushing of middlings or to keeping middlings out of circulation and treating them separately? L. A. DELANO.-AS was shown in Mr. Rabling's paper (Bulletin No. 128, p. 1161) the tonnage was raised by about 400 tons by simply changing the arrangement of screen openings in the jig bed and using punched plate instead of woven-wire screen. Then, by adding a ball-mill, we are taking from the jigs a much larger tonnage of middlings than before or as much as the ball-mill will crush. By sending the ball-mill product to tables and flotation, the jig capacity for original ore is increased. CHAIRMAN BILHARZ.-In your opinion, the satisfactory operation of a Hancock jig on a given ore requires adjustment of the length of the different screens and careful selection of screen openings? L. A. DELANO.-I think it does. In order to decide what screen openings to use on the jigs, we did a great deal of experimental work, making screen analyses of the various hutch products, and then hand-sorting the galena, middlings and chat from each size screen to determine the percentage of galena in each. Then adjusting our jig screens, we gradually worked the process up to a very efficient basis. ERNEST GAYFORD, Salt Lake City, Utah.-I would like too ask Mr. Delano whether the work of the Allen cone has been quite as satisfactory as the manufacturers claim for it.

Jan 1, 1918

The annual world production of minerals approximates 1,700,000,000 tons, over 90 per cent. of which consists of coal and iron. Of this amount about two-thirds is used within the countries where the minerals are produced and one-third is shipped to other countries. The movement of most of these minerals, though, shows a rather remarkable concentration. For instance, manganese moves from three principal sources and converges at four or five consuming centers; chromite and tungsten move from two principal sources. The United States is more nearly self-sustaining in regard to mineral commodities as a whole than any 'other country on the globe; but the interests of conservation - call for an international viewpoint in the handling of our mineral resources., There is perhaps as much need of specializing in mineral output as there is of specializing in manufacturing. The thought that every country on the globe should be self-sustaining in regard to mineral supplies is of somewhat the same order as the thought that every family should produce all its own raw materials rather than take advantage of the more favorable conditions existing elsewhere and so specialize in human effort. Extension of international control of minerals seems to offer possibilities of loss and gain-loss through a considerable sacrifice of national trade .and a narrowing of the field for private initiative in trade; gain through the possibility of attaining certain ends which are attainable only by international agreement, such as an allocation of supplies which will be to the advantage of the greater number of nations rather than to the advantage of the few that are strong enough to dominate the situation. The interests of conservation clearly require international control. Moreover, the lesson of the war points to the necessity of overhauling old international understandings and machinery, even though such a task would encounter great difficulties, not the least of which lie in the persistence of human habits and inertia. Whether the time has come to establish a league of nations with economic control can be determined only by our individual and collective answers to the question whether we are willing to make the necessary economic sacrifices, individually and nationally, in the interest of world harmony. The mineral industry should fully understand that, with international control, efforts to promote export will need to be modified and curtailed; that expansion of our trade in many lines will mean equivalent loss of trade to other nations; that the almost universal conception that expansion of foreign trade is a meritorious aim and end in itself, without regard to its effect on other countries, will need revision.

Jan 3, 1919

ONE of the features of the annual meeting was a round table conference on carbon in pig iron, on Feb. 16. This was presided over by R. H. Sweetser, and the discussion, which was so interesting as to require holding an additional session in the after-noon, ranged over such a wide field that only a brief outline of it will be attempted here. The full discus-sion together with the papers will be printed later. The first paper was one on the need for research in foundry pig iron (1648-C) by Richard Moldenke, who pointed out the trend in present practice of attaining low cost in pig iron production by hotter blast, addi-tion of. scrap to the blast furnace, and. the enormous increase in the output per furnace day. He pointed out that remelting processes are oxidizing processes, to some degree at least, and the metal cannot be given the deoxidizing finish which is characteristic of the steel-making process. The trend today is toward specifying total carbon content in foundry pig irons, and since the carbon content depends on a variety of factors, he suggested that the blast-furnace men and the foundry men study the question and agree on a minimum of total carbon for the given silicon ranges. The discussion of this paper was participated in by E. J. Lowry, Robert Jones, T. L. Joseph,. R. H. Sweet-ser, J. G. Ferguson, W. B. Coleman, E. P. Ross and D. J. Demorest and ranged from a comparison of the total carbon used in making a ton of pig iron in charcoal practice versus coke practice to a discussion of the bad effects observable from the use of scrap This paper was followed by one on carbon character-istics of copper-bearing pig iron by W.. B. Coleman. In view of the belief in many foundries that copper-bear-ing pig iron made trouble in the foundry, experiments were made by adding copper in various amounts up to 1 per cent and with the cooperation of the Robesonia Iron Co. a large number of tests were made over a run of foundry iron. The final conclusion was that the ad-dition of less than 1 per cent metallic copper did not seem to alter the physical properties and that a blast furnace using copper-bearing ore can produce pig iron suitable for making small castings, showing low-Brinell hardness test, good transverse and deflection tests, and high-total carbon.

Jan 3, 1927

By G. K. Engelhart

A multi-stage counterflow process developed in Germany preheats dry pulverized portland cement raw materials held in suspension in rotary kiln waste gases. Capacity of the first kiln installed for this purpose in the United States has been increased from 860 to 1500 bbl per day, with fuel reductions from 1,100,000 Btu to 650,000 or 700,000 Btu per bbl. Sixty percent of total waste gas is used. As full use of the gas stream is approached, additional kiln production and fuel economy may be expected. EFFECTIVE use of rotary kiln waste gases to preheat dry pulverized materials has been demonstrated in full-scale operation at the Allentown Portland Cement Co. plant, Evansville, Pa. Pulverized raw materials are preheated in suspension in the gas stream in a multi-stage counterflow process which draws the gases through a series of cyclone collectors. Upon entering the first cyclone stage the material, continuously delivered and suspended in the gas stream, is successively collected and re-suspended until it discharges through the kiln feed pipe. Gas and material contact time is thus prolonged, providing a high degree of heat recuperation with a very low temperature differential between gas and material at the final stage. The suspension preheater, developed by Klock-ner-Humboldt-Deutz AG of Cologne, Germany, was first installed at the Norddeutsche Huette plant, Oslebshausen, Germany. Similar preheaters are now in operation at three other German cement plants. The first American installation, at the Allentown Portland Cement Co. plant, was designed and manufactured by Fuller Co. of Catasauqua, Pa., Humboldt's licensee for the United States, Canada, and Mexico. Design of this installation is essentially the same as the German original, but provision was made for varying the method to adapt the process to specific objectives of American portland cement production. Differences between German and American cement clinker production practices are directly related to differences in three primary production cost items: fuel, labor, and power. Because fuel costs are high in Germany and elsewhere in Europe, thermal efficiency has been the first objective of European cement producers and manufacturers of rotary kilns. The Germans have developed such recuperative equipment as the present suspension preheater, the Miag calcinator, and the Lepol kiln, the invention of 0. G. Lellep. In North America labor is the principal cost item, although rising fuel costs are of growing concern. High clinker production is therefore of first importance. Recent installations of longer dry process cement kilns have been disappointing, failing to make satisfactory reductions in exit gas temperatures when production is held at an acceptable level. The Humboldt suspension preheater satisfies both

Jan 1, 1955

By Robert M. Dreyer

Diamond is the hardest known material. The diamond industry is separated into two major segments: (1) industrial and (2) gem. The major industrial use of diamonds is as a high-grade abrasive in a wide variety of applications for which no effective low-cost substitute is available. Table 15.4C.1 gives data on diamond production and on United States diamond imports. In both gem and industrial diamond production, but especially in the case of gems, the quantity of stones produced is not directly correlated to value, for the determination of value is markedly affected by quality. South Africa long has been the world leader in gem diamond production with an estimated production in 1968 (including South-West Africa) of about 4 million carats, equal to 43% of world production. During the past decade there has been a marked rise in gem diamond production in the USSR, so that nation is now the second-ranking world producer, with Angola (Portuguese West Africa) third. In natural industrial diamonds, the major production comes from Congo-Kinshasa (former Belgian Congo) which had a production of 15 million carats in 1968, equal to 47% of world production. In the past six years, there has been a remarkable increase of industrial diamond production in the USSR, which now ranks second with a production of 6 million carats, equal to about one-fifth of world production. South Africa now ranks third followed by Congo-Brazzaville and Ghana. No natural diamonds are produced in the United States. Since the discovery of an economical method for synthesizing small diamonds, there has been a rapid increase in synthetic production from 4 million carats in 1962 (1 carat equals 200 mg) to 11.5 million carats in 1968. Table 15.4C.1 gives the gradually increasing imports of industrial diamonds and indicates a relatively stable price. In 1968, the imports of industrial diamonds were 13.5 million carats with a value of $59.2 million. Table 15.4C.2 shows the rapidly increasing imports of cut and uncut gem diamonds into the United States. In 1968 the United States imported 2.5 million carats of uncut stones with a value of $166 million and 1.5 million carats of cut stones with a value of $175 million. Diamond marketing is dominated by DeBeers Consolidated Mines, Ltd., which, through subsidiaries, controls many of the major African diamond deposits. More important economically, however, through its Central Selling Organization, DeBeers markets 86% of the non-Communist world's natural diamonds, including most of those derived from deposits outside of corporate control. In 1967 the mines owned by DeBeers produced nearly 8 million carats, and the Central Selling Organization sold over $600 million in gem and industrial diamonds. The dominance of diamond sales by

Jan 1, 1976

REORGANIZING AMERICAN ENGINEERS There are in America approximately 500 engineers' organizations of various kinds, and yet it is estimated in many communities that 30 to 50. per cent. of the resident engineers are not members of any society of engineers. There is no enumeration of the engineers of the country, but estimates range from 100,000 to 300,000, the latter number probably including assistants, such as instrumentmen, draftsmen and inspectors, together with professional engineers. These local, state, regional and national organizations are for the most part independent and have no means for cooperation. Steps toward the improvement of these conditions are being taken in a number of localities and have already been taken in others. Many engineers are giving the matter serious attention. American Society of Civil-Engineers took an important action at the June meeting of its Board of Direction, by, authorizing the creation of a Committee on Development of Am. Soc. C. E. This action is now well known to all representatives on Engineering Council. Other Founder Societies axe reported to be considering similar action. Engineering Foundation, at its meeting on Sept. 12, adopted the following resolutions: Survey of Engineering Organizations BE IT RESOLVED: that the Engineering. Foundation is prepared, the four Founder Societies concurring, to devote its strength and its' income, so far as this may he required, to a study of existing engineering organizations, and from information thus developed to formulate a series of constructive recommendations which may he serviceable in guiding the further development of local and national engineering organizations in their relations to the profession of engineering, to the public and to each other, to the end that a foundation may he laid upon which to establish a broadly planned procedure, which, while recognizing and preserving all that has already been accomplished, shall increase the power of American engineers in upbuilding their profession and in the service they render to society; and RESOLVED: that in accepting the responsibility for such an undertaking, it will be the purpose of the Engineering Foundation to organize the proposed research along the broadest possible lines, to call to its aid highly qualified experts, and to avail itself of the help of agencies which may be willing to cooperate; and RESOLVED: that in proposing this research the Engineering Foundation has no desire or purpose to intrude upon the domain of individual organizations; that it does not propose to control the action of any individual or organization; nor to ask the acceptance of its conclusions; but that its purpose shall he to develop a possible procedure, or a series of such procedures, of such evident, merit that they will appeal to those who are likely to be most interested; it will do this in the belief that in so far as its work may justify the confidence of engineers and of engineering organizations, it will bear its own fruitage.

Jan 11, 1918

By W. E. Horst

John Dasher (Central Research Laboratory, Crucible Steel Co. of America, Pittsburgh. Pa.)— Getting spodumene to float quickly and cleanly can be a problem. The author has presented an excellent account of a valid and useful approach to the scale-up of such problem floats. This indicated advantages for doubling retention time, i.e., buying another set of flotation cells. The author states that 21 pct of the spodumene floated in 2 min in the laboratory cell, that the grade of the rougher was about 75 pct spodumene, and that the final tailing contained 4 to 12 pct spodumene in different sizes with the present cells and 1 to 9 pct spodumene with twice as many cells. About 20 years ago, this writer obtained in the laboratory the flotation of over 90 pct of this spodumene in a King's Mountain sample in 1 min at a grade of 90 pct spodumene in the rougher and a final tailing that contained only 1 pct spodumene. The methods of Norman, Ralston," and Gieseke' were used, which teach that spodumene floats quickly and cleanly if its surfaces have been properly conditioned chemically and/or mechanically prior to flotation. Although feed preparation is not discussed, the results reported indicate that it is inadequate. This writer suggests that improvements in this area might be more effective than doubling the number of cells. W. E. Horst (author's reply)—Dasher's comments are appreciated by the author and require some clarification. He suggests that improved spodumene flotation performance may be obtained by feed preparation techniques rather than increased retention time in flotation. Certainly flotation performance is dependent on feed preparation and this is an important feature in the flotation process. It is true that certain types of spodumene ores, particularly weathered ores, require more complicated feed preparation processing than clean ores to achieve the desired flotation results. It was not implied that current feed preparation techniques are the same as experienced during the scale-up investigations. Although discussion of feed preparation was omitted from the article on scale-up relationships, the important feature was that pre-treatment processing was the same for each level of operation investigated— laboratory, pilot plant, and plant scale. Under these similar conditions large differences existed in recovery for comparable time intervals in each scale of operation. It is highly probable that feed preparation techniques could be modified and thereby increase the flotation rate for each scale or all scales of operation discussed. However, modifications would have to be justified on an economic basis.

Jan 1, 1960

HAVING previously described the metals to you, before I proceed any farther I do not wish to fail to tell you, as I promised to do in the first chapter on metals, what I have learned through experience concerning the semiminerals, although this may seem to you outside our proposed subject. Since these are not produced by Nature as all rock or all metal they are called semiminerals by speculative physicians. Many kinds of these are found; those that resemble rocks are earthy, very difficult to liquefy, and much more adapted for adorning paintings than for anything else. Those that liquefy with fire, like sulphur, antimony, marcasite, [22] calamine, zaffre, manganese, and others, resemble the metals almost like brothers. Some others are more watery so that they dissolve in water, although they are fairly dense, and are obtained and reduced to their, perfection by means of water. These are the salts, vitriol, rock alum, and saltpeter. To these, as a watery thing, belongs also quicksilver, as it is commonly called because of its motion. Although it appears. not only liquid, but very liquid, this is not at all similar in its effects to any of the above. Indeed, it retains its same being until its very form is consumed. Since the reasons for its effects are almost impossible to investigate, I do not intend to speak of them here or to enter now this maze of speculation, because I wish to make definitely clear to you what this quicksilver really is. Therefore, leaving aside opinions and disputes, I shall take only those of the said semiminerals that I know are useful. First we shall see the method by which the semiminerals can be found and then how they are to be extracted from their matrices. These, perhaps, have no less need of effort and industry than the metals since they are substances completely hidden in the rocks or in the earth. For this reason some of these that are sought are made use of by means of fusion after they have been mined from their mother mountains, and some others need to be disposed by a certain maturative corruption, now with moisture and coldness, now with dryness and heat, as with waters, rains, frosts, or long baking in the sun, with fire, or even with a strong reheating within themselves. Most of them can finally be brought to the desired end by means of solution with water and fire.

Jan 1, 1942

By Willard P. Ward

I DESIRE to put on record a fact in relation to the effect of manganese on pig iron which I have never seen in print, and which may, perhaps, not have been observed by anyone except myself. In 1875, while experimenting on the production of ferromanganese in a blast furnace, I had burdened the furnace with a charge which I calculated would produce a 15-per cent spiegel. The furnace was very hot, having been running for a couple of days on a very light burden, and making a burnt iron, preparatory to the experiment I proposed to make to produce a high grade of spiegel. I calculated that the charge would begin to work in the furnace in about twelve hours after it was put on. After the lapse of that time I commenced to watch the furnace carefully, but found little or no. change in the appearance of the metal, although there was a very decided change in the cinder, showing that the manganese ore had come in work. The iron was quite gray and very tough. The character of the cinder was good for a spiegel cinder, and I could not imagine where the manganese was going to, as it (lid not appear to be in either metal or cinder in anything like the quantity indicated by the charge. The next morning things were still in, the same condition. The furnace was very hot, the cinder good, and the iron very gray. I was then sorely puzzled. I had never heard of a gray iron with over 4 or 5 per cent, of manganese, and had no notion that an iron with more manganese could be gray and tough. With great difficulty a piece for chemical test was broken from a pig. Not less than a hundred blows from a heavy sledge were required to break it off I took the specimen to the shop and directed that some borings from it should be brought to the laboratory, as soon as possible, whither I myself at once repaired -to put things in readiness for a rapid manganese determination. In about half an hour the machinist came in with the iron specimen in one hand and about, a dozen blunted and broken steel drills in the other, saying that it was impossible to drill the iron. There were several little depressions in the iron, which was malleable enough to be indented by the point of the drill, but not a chip had been cut from it. The metal was never subjected to further physical tests. A chip broken from

Jan 1, 1882

By W. R. Jones

composition, he cannot reasonably asl; the manufacturer to guarantee that this composition shall give certain physical results. W. R. Jones, Pittsburgh, Pa. : The question that naturally occlun to me is this: Has Dr. Dudley in his inveatigtrtions been aiming to prove a theory, or has he been guided by an earnest desire to discover what are the proper elements in the composition of a good-wearing steel rail ? Unfortunately, for correct chemical information, he has omitted in his analgw two very importnat elements,—sulpbur and copper. Now, before we will even begin to admit the correctnets of Dr. Dudley's conclusions and the formula he prescribes, we will at the start question the propriety of any chenlist or scientist prescribing a formula for making steel when he has iguared such important ele ments as sulphur aud copper. I, for one, will not accept any such formula. Are we sure, or is Dr. Daclley sure, that the chemical analyseq embodied in his paper are correct? This may seem a presumptuous queetion, yet, with my experience with chenlists, I naturally doubt the correctness of the analyse8, and, before I will accept them as correct, I will ask that comparative tests of phosphorous and man ganese be made by the Pennsylvania Railroad chemists and the chemists of the leading steel-works in the country. Let us first verify the correctness of the analyses before we consider the con clusions. I can enumerate a great number of instances in which chemists have differed very widely in their determinations of phos phorus and manganese. A prominent iron fitam made a contract with the Edgar Thomson Steel Company to deliver pig metal guar anteed to be between 0.07 and 0.08 phosphorus; an analysis by our chemist resulted in phosphorus 0.148 and 0.152,—a rather startling difference! Again, a sample bar of steel, in which our chemist reported phosphorus 0.11, was tested by a chemist of au other Bessemer works, ana his determinations were phosphorus between 0.07 and 0.08: A leading engineering establishmeut of Pittsbdrgh bought iron claimed by a chemical analysis to contain 0.08 phosphorus; our Mr. Ford found phosphorus 0.145. A chem ist connected with an open-hearth works reported manganese in a piece of steel, 1.14; in a second determination from the same piece of steel, by the same chemist, manganese was reported 0.43. The chemist was kept in ignorauce of the fact that both samples were from the saw piece of steel. Two dctermiuations for manganese

Jan 1, 1881

By Ronald C. Koo

THE effect of grain size on the mechanical properties of the bcc metals has been a subject of intensive theoretical and experimental study.'-l5 Quantitative relationships have been established experimentally between yield stress and grain size and between the ductile-brittle transition temperature and grain size in a number of metals.6"15 Much significance has therefore been attached theoretically to the grain size dependence. In all these experiments, different grain sizes were always achieved by annealing specimens at various temperatures. The implicit assumption was that any change in the dislocation substructure or in the distribution of impurities which might occur simultaneously with the production of various grain sizes had only a negligible effect on the mechanical properties. The validity of this assumption, however, is questionable. transformation in iron-nickel alloys is actually an extraneous phenomenon due to inadvertent compositional changes in the martensite if the heating rate is not sufficiently rapid. This complication can be avoided by up-quenching for the reversal treatment,5 and then the stabilization does not appear. Clearly, the lattice imperfections and strengthening produced by the reverse transformation are not responsible for the marked stabilization which has been observed by other investigators in these alloys. Data will be presented in this note to show that, at least in recrystallized tungsten of commercial purity, the difference in the ductile-brittle transition temperature of specimens annealed at various temperatures is more a result of a variation in the distribution of impurities rather than of the difference in grain size produced by the anneal. Ductile-brittle transition temperatures in tension were determined on powder-metallurgy tungsten specimens recrystallized at various temperatures. Tensile specimens having a gage length of 1.50 in. and gage diam of 0.18 in. were recrystallized at 1450°, 2000°, 2350°, 2550°, 2750°, or 2800" for 30 min in a vacuum furnace at a pressure of 1 x 10"5 mm of Hg and then tested at a constant extension rate of 8 x 10 per sec in an argon atmosphere from 100" to 800". Typical quantitative analyses of impurities are given in the Table. These results show that, within the precision of the analyses, see Table, annealing did not result in any detectable change in the impurity contents of the specimens, nor was there any detectable difference in purity between specimens having large differences in grain size annealed at the same temperatures . The results of the tensile tests yielded three distinct ductile-brittle transition curves approximately 225' apart. As shown in Fig. 1, data of specimens annealed at 1450°C and those of specimens annealed at 2000°C (O) fell on Curve A. Data of specimens annealed at 2350" and 2550°C fell on Curve B, and those of specimens annealed at 2750" and 2800°C fell on Curve C. The decrease in ductility with increase in annealing temperature became so pronounced that one third of the specimens annealed at 2750" and two thirds of the specimens

Jan 1, 1963

By Cecil Desch

THIS annual lecture, under the auspices of the Institute of Metals Division, and which was illus- trated by lantern slides, has been printed in full and a limited number are available for distribution on request. Some excerpts from the lecture are given below: Ever since the simple geometrical relations of crystals were discovered, it has been recognized that their proper-ties are best explained by assuming that their ultimate particles are arranged on a space lattice, and that the char-acteristics of that lattice determine the shape of the crystal and its physical and mechanical properties. Modern ex-amination by means of X-rays has widened that concep-tion and given it greater; definiteness, and the atoms are now regarded as the particles forming the space lattice. The splendid achievements of investigators in this field have made it possible to state, for a large number of sub-stances, the form and dimensions of the lattice. The char-acteristic of a lattice is that a unit of simple geometrical form is repeated at regular intervals in three dimensions so as to fill the entire crystal. It follows that there must be certain planes in which the atoms are more closely packed than in planes drawn at any angle to them, and it is these planes of closest packing which play the greatest part in determining the growth and other properties of the crystal. There are actually two stages in crystallization, what-ever be the medium in which it occurs. The first is the ap-pearance of crystal nuclei; the second the growth of those nuclei to form crystals of appreciable .size. The first is clearly a kinetic phenomenon. In the molten mass, solu-tion, or vapor, the molecules are in a state of rapid motion and frequent collision. When the temperature has fallen so far. that it is possible for a crystal to exist, a few col-liding molecules may fail to rebound, and so become at-tached to one another, the balance between the attracting and repelling forces-between them causing them to arrange themselves on a space lattice, to which other molecules sub-sequently attach themselves. It was once maintained that the X-ray evidence demanded that the molecule should dis-appear in the solid crystal, but this was a wrong inference, and in many crystals, but not in all, the chemical molecule retains its identity in the solid state. In pure metals the atom and the molecule are identical, so that the conditions are unusually simple. How many. nuclei will be formed in a given mass is evi-dently a problem in probability. Experiments to deter-mine the relation between the temperature and the number of nuclei formed in a given time have been made with some success by using viscous organic substances, but metals offer much greater difficulties, and the few determinations which have been published are vitiated by serious errors. However, the examination of sections of ingots of the same composition and cast at 'the same temperature in similar molds will show, that the number of crystals does not vary widely.

Jan 3, 1927

By J. Suiter, H. F. Ryan

H. F. Ryan and J. Suiter (CSIRO)—In this paper the authors have presented "a physical model which has as its central hypothesis the solution strengthening of regions along grain boundaries in the order of tens of angstroms thick", and their calculations have used 40Å as the zhalf-width of this boundary region. Selection of this value by the authors suggests that they were unaware of a number of recent field-ion microscope observations of grain boundary structures (e.g., Refs. 29 and 30). The accompanying figure, Fig. 9, shows a portion of an ion micrograph of a tungsten specimen containing a grain boundary, and the regular arrangement of atoms in various crystal planes in each grain can be seen, except in the boundary zone which is not more than two atom diameters in width. Since it is expected that solute atoms will segregate only to the region where the lattice is disturbed, it would seem that a value of 4Å for the half-width of the boundary region would be more appropriate than the value of 40Å assumed by the authors. If the former value is used in Eq. [8] of their paper to obtain curves showing solute concentration in the grain boundary as a function of temperature, the resulting curves differ significantly from those obtained by the authors. Although there are only relatively slight changes in the regions corresponding to higher temperatures (i.e., grain boundary concentrations of approximately 1 at. pet), at lower temperatures the curves are no longer realistic. For example, the curve corresponding to u = 7000 cal per mole gives a solute grain boundary concentration in excess of 100 pet at a temperature of approximately 360°K, and "flattens out" at a grain boundary concentration of about 300 pet! Similar results are obtained with each of the other curves. Ion microscopy of dilute solid-solution alloys has shown that solute atoms give rise to image points which in most cases are of higher intensity than those of the solvent atoms.31 If the same behavior occurs when the solute atoms are present in much lower concentrations then ion microscopy should provide a sensitive tool for studying the segregation of impurities to the grain boundary regions. Although many grain boundaries in tungsten have been examined after different thermal and mechanical treatments, there has not been, as yet, any systematic study of such segregation. In general the micrographs show no clear indications of marked grain boundary segregation, but occasionally areas are found where the grain boundary contains an appreciable number of image points of high intensity in a very narrow zone, see Fig. 9. If it is assumed that these correspond to impurity atoms then it is possible to estimate the impurity concentration both in the grain boundary and within the body of the grains. Application of this method (to a larger area

Jan 1, 1965