Search Documents

By W. H. Brandt

ThEre has been much progress in the last two decades in understanding the hardenability of steel. Roughly, the progress has been along two lines, which may be designated as empirical and fundamental. This empirical work has progressed to the point where steels may be manufactured to the desired characteristics quite closely and heat-treatment and application problems can be approached with considerable confidcnce. Particularly noteworthy among the empirical work is that of Grossmann,12. who has given formulas for calculating hardenability as a function of composition, and the establishment of the isothermal transformation curve by Davenport and Bain.13 The latter does not fall entirely in the class of an empirical study, for while it provides a means of presenting a tremendous amount of empirical data in the form of a single curve, it also outlines clearly the problems that face the fundamental investigator. The isothermal transformation curve shows clearly that the phenomena occurring in the neighborhood of the knee of the curve are those that limit the hardenability of steel. Above the knee of the curve, the product of decomposition of austenite is lamellar pearlite and fundamental progress has consisted chiefly of a detailed study of structure and formation of pearlite, largely at the hands of Mehl and his collaborators.'-5 They have shown that formation of pearlite proceeds by a process of nuclea-tion and growth and they measured both the nucleation and growth rate. However, there is still a wide gap between our empirical knowledge and fundamental knowledge, owing largely to the fact that there is no satisfactory theory of nucleation rate or of growth rate. This paper is being written in an attempt to Hl in a small part of the gap. A method was prcsented recently1' for calculating the velocity of edgewise growth of pearlite using an expression for the carbon concentration that satisfies the diffusion equation. The edgewise velocity of pearlite growth in a plain carbon eu-tectoid steel was calculated, using linear extrapolations of the ferrite and comentite solubilities. While the results are in fairly good agreement with the experimental facts, the calculated velocity of edgewise growth is smaller at 600°C. than G, the radial growth velocity of pearlite nodules, whereas one would expect it to be larger. In this paper the calculation will be repeated using a new extrapolation for the ferrite solubility, which gives better agreement between G and T', the calculated velocity of edgewise growth. A calculation will also be made of the effect of carbon content on velocity of edgewise growth, and the problems of calculating the effects of other alloying elements on growth rates will be discussed. It will be assumed that the mechanism of pearlite growth, established by Mehl and

Jan 1, 1947

By F. L. Robertson, C. H. Bacon, J. W. Till

A description is given of the development of a process for making low sulphur steel on furnaces fired with 2 1/2 pet sulphur oil. Slag and metal are analyzed at melt. Slag weight is estimated. A simple method for calculating necessary lime additions for making 0.025 and 0.035 pct sulphur steel is given. DURING the last 15 years John Summers & Sons have been confronted increasingly by the problem of producing a low sulphur steel from high sulphur materials. The principles adopted, the processes used, the data collected on a furnace specially set aside to study this problem, and speculation on future developments are dealt with in this paper. This study is limited to two melting shops which make sheet steel only, of the following analysis: C, 0.06 pct; Mn, 0.33; S, 0.04, 0.035, 0.03, and 0.025; and P, 0.02 and 0.015. All the processes described have reference to the manufacturing of this steel and are not necessarily applicable, without modification, to other steels. The raw materials used are given in Table I. Development of Process About 1934, Schenck's work on phosphorus was applied to frame quantitative rules for the removal of phosphorus, with great success. We could however, neither in our own work nor in the voluminous literature, find any assistance to frame quantitative furnace rules to remove sulphur. Perhaps, we should have persevered with Schenck's outstanding chapter on sulphur in The Physical Chemistry of Steelmaking, but we missed the importance of one (Ss) sentence on p. 478. "Evidently this ratio -------- is [S] the important quantity to be considered from the point of view of chemical reaction; it is clear that the sulphur content of the steel alone, as frequently given in the literature cannot suffice for judging the success of the reaction unless special details are given regarding the sulphur charge and the amount of slag."' We were not however very successful in getting values for Schenck's "n" that agreed with (S) arrived at by our direct analysis. [S] In addition to Schenck's work much attention was given to V value. The formula selected for V was: (SCaO) — 1.57 (2 P2O5) (S SiO2) After plotting many charges a curve was obtained, based upon the relationship between the percentage sulphur in the finished steel and V value, Fig. 1. For a long time this was used as standard with about a 60 to 70 pct success on producer-gas fired furnaces, if all uprising scrap was used and no bought scrap used. An inspection of this curve shows clearly that it is not a quantitative manufacturing process, and that it was not sure enough to go to the trouble and expense of doing stage analysis for P,O,,

Jan 1, 1952

By Susan B. Leiter

That oxygen in copper has been a source of trouble is well known and that that trouble has been real in the commercial world has been shown by Fuller.' Moore and Beckinsale's paper2 at the annual meeting of the Institute of Metals in London, 1921, called forth considerable discussion. Prof. T. Turner expressed the opinion that it was not necessary to have cuprous oxide present in sufficiently large quantities to form either globules or seams in order to produce a bad effect if the copper were gassed. This brought up the question of the solubility of oxygen in copper and the authors desired to know whether there were any evidence of such solubility, because their experience was that whenever there was any oxygen in copper it was present in the form of free cuprous oxide, which was practically always in the form of globules. Later Hanson, Marryat, and Ford3 stated that 'for all practical purposes cuprous oxide may be regarded as insoluble in copper. However, they found particles of the eutectic to coalesce to form much larger particles. They suggested that cuprous oxide was actually slightly soluble in copper, for it was difficult otherwise to understand the mechanism by which such coalescence could take place. W. E. Ruder, in discussing that paper, said that his experiments had led him to conclude that a slight solubility must exist to allow for the ready coalescence of oxide particles, but conductivity tests convinced him that that solubility was very small. Nevertheless, there appeared to be a state of admixture of oxide with copper that closely resembled a colloidal mixture which at first was mistaken for a true solution and which usually existed at the grain boundaries. The purpose of this paper is to give the results of some investigations, begun in September, 1921, which would seem to show that although cuprous oxide may be only slightly soluble: (1) this solubility is sufficient

Jan 1, 1926

By John T. Eash

DURING the course of the war the supply of tin in this country has steadily decreased and a continued effort has been made since the beginning of the emergency to use alloys that are either tin free or contain appreciably lower quantities of it. Even with the use of emergency materials, the tin supply has become particularly acute, and it is estimated that after recovery of the far eastern mines probably one to two years will be required before our normal annual supply is attained. One of the major tin-consuming fields is the bronze industry. Recommendations were made several years ago by the War Production Board toward the use of bronzes of lower tin content and manganese bronze and yellow brass for the customarily used tin-bronze alloys. The substitution of 88-5-5-2 copper-nickel-tin-zinc for composition G received considerable attention before the war, and consequently this alloy and modifications of it have been adopted for some current structural and pressure castings requiring high mechanical properties. Another of the commonly used bronzes is the 10 per cent tin, 10 per cent lead copper alloy for heavy-duty bearings. It has been known for some time that about 2.5 per cent nickel could be substituted for an equal amount of tin with retention of equivalent casting and tensile properties; however, it was desirable that a still greater conservation of tin be made. Consequently the present paper deals with the development of an alloy of low tin content that could be used for bearings. SELECTION OF COMPOSITION While the final criterion of the suitability of an alloy for a bearing must 0f course be determined by practical applications where all the ramifications of service conditions are encountered, certain short cuts in the initial selection of compositions are necessary to avoid an extensive and time-consuming investigation. The present program has been to match certain metallurgical properties of the 80-10-10 bronze that have been shown by previous investigations to be related to good bearing qualities. Such properties as microstructure, hardness, compressive yield strength, ductility, and castability have been considered, and certain simple wear tests have been made. Of the readily assessed characteristics desired in a good bearing alloy, one can be certain that a uniform distribution of lead is required in a leaded bronze. It has generally been found that segregation of lead is one of the chief difficulties with this type of material. Tin has a powerful effect on lead distribution, and with 10 per cent present produces a random distribution of chunky particles, such as are shown in Fig. I. In addition, the tin bronze contains the hard alpha + delta eutectoid constituent distributed through-

Jan 1, 1945

By L. D. Jaffe, M. R. Norton, J. H. Hollomon

In the practical heat-treatment of steel the decomposition of austenite usually occurs during cooling rather than at constant temperature. Nevertheless, the course of this decomposition has generally been studied only isothermally. Isothermal studies are not only simpler experimentally, but have the great theoretical advantage that one of the variables, temperature, is constant. It is the purpose of this paper to outline the principles that govern the relations between isothermal and anisothermalt‡ decomposition of austenite, to present and systematize the available experimental information, and to indicate the gaps in the existing knowledge. Some of the experimental information is the result of new work.§ Most of it is derived from scattered data in the literature. Many of these data were obtained incidentally in the course of research on other subjects and their significance has not been pointed out and perhaps not understood. It is hoped that this paper will aid future planning of more extensive research on anisothermal decomposition. Method In order to study the relations between isothermal and anisothermal decomposition, it appears fruitful to view anisothermal decomposition as taking place at a series of constant temperatures1 (except for the martensite reaction, which does not occur isothermally to an appreciable extent). When the time the steel is at each temperature is finite, the over-all amount of the reaction is considered to be the sum of the amounts occurring at each of the successive temperatures. During continuous cooling or heating, the time the steel is at each temperature and the difference between successive temperatures can be considered to approach zero. The over-all amount of transformation will then be given by integration over the range of temperatures involved. This point of view is advantageous in that it considers anisothermal transformation to be a series of isothermal transformations. The problem thus becomes one of determining the effect of partial decomposition at any given temperature upon subsequent decomposition at another temperature. Single Anisothermal Reaction Consider a phase brought to a temperature at which it is unstable, held there until it has partially transformed, and then brought to another temperature at

Jan 1, 1947

By A. M. Gaudin, C. S. Chang

IN general, fatty acids or their alkali salts do not cause clean quartz to float. However, the presence of multivalent ions, such as the alkaline-earth metal ions and heavy-metal ions, can activate quartz and thus make it respond to soap flotation. The mechanism of activation and soap flotation of quartz has been studied.1-4 The problem was attacked by making flotation tests rather than by careful adsorption measurements on suspensions of ground quartz in solutions containing the activator and the collector. Attempts have been made to determine the adsorption of barium ion and calcium ion on quartz. The results have only qualitative value as the analytical methods were not adequately precise. Artificial radioactivity and progress in radioactivity detection have introduced a new analytical tool, which can have a sensitivity several orders of magnitude greater than that of other methods.5-6 In the experimental work described in this paper the radioactive tracers, barium 140 and carbon 14, were employed. Lauric acid was synthesized, having a radioactive carbon atom and was used with Ba140 to study the adsorption of barium and laurate ions from aqueous solution on ground quartz. Flotation tests, using the vacuum flotation technique,4 were run in conjunction with the adsorption experiments. The object of this investigation was to understand better the reaction mechanism of barium activation and soap flotation of quartz. Methods and Materials Quartz Sample Preparation: Lumps of hand picked quartz, washed free of stains, were reduced in size to -20 mesh in laboratory crushers. The product was boiled in concentrated hydrochloric acid to remove the abraded iron. The cleaned product then was ground dry in a laboratory porcelain mill, using siliceous pebbles, to pass through a 200 mesh screen. The ground product was deslimed by sedimentation at 37 microns. This -200 mesh +400 mesh material was subjected again to boiling with concentrated hydrochloric acid, followed by washing with distilled water and further desliming. The cycle was repeated until no trace of iron could be detected in the wash liquor. During the final washing, the pH of the wash water was checked to insure the complete removal of the acid from the mineral. The quartz then' was rinsed with conductivity water. The resulting product was dried in a drying oven and stored in mason jars. The impurities (spectrographic) were as follows: Al, 0.01 to 0.001 pct; Li, Mg, Mn,, Na, each less than 0.001 pct; Fe and Cu not detected. The specific surface of the quartz sample was determined by the krypton gas adsorption method.7 The average of two measurements was 881 sq cm per g. The calculated specific surface for 37/74 micron quartz particles, using a surface factor of 1.96,8 is 900 sq cm per g. This is in good agreement with the measured value of 881 sq cm per g. Beta-Counting Method: The radioactive isotope of barium used in the experimental work was barium 140. It has a sufficiently long half-life, 12.8 days, emits high-energy beta particles (up to 1.0

Jan 1, 1952

By B. M. Larsen, T. E. Brower

Introduction and Summary By "thermochemical factors" we refer to those variables which affect the net heat which must be put into the bath in order to make a heat of steel from any given set of charge materials. This is admittedly only one phase of the production rate problem. The whole problem includes also consideration of rate of charging, flame radiation intensity, rate of optimum fuel input obtainable without undue damage to the furnace structure and any variations in conditions such as stirring, slag volume or viscosity which affect the rate at which heat can flow down and away from those exposed surfaces where the heat is first received from the flame. Because a given type of charge in a shop is often considered as being nearly constant in both physical and chemical characteristics from one heat to another, and because such a state of affairs may be thought of as resulting in a reasonably constant net heat requirement, this requirement is usually neglected as an invariable, inevitable matter, about which nothing can be done. With normally variable charge, and variable percentages of limestone and cold pig, however, the net heat requirement can be subject to very appreciable change; it may also be affected by such things as the currently popular procedure of blowing oxygen into the bath. To bring the general problem of production rate into better perspective, therefore, it seems worthwhile to try to evaluate the net bath heat requirement and the amount by which it may change through variation in different factors. Because our calculated values of net heat are admittedly uncertain, we have tried to check them in part by statistical data on actual production rates over rather large groups of commercial heats. The results of calculation of net heat requirements in a wide range of actual commercial practices may first be summarized briefly. We find a wide range between the extremes of different practices, as would be expected, with duplex practice (essentially blown metal plus hot metal) having essentially a zero net heat requirement, an all-cold charge practice somewhat over I million Btu per ton of steel and a high hot metal practice about 0.75 million Btu per ton. Over the commercial range of scrap plus hot metal practice, increasing the percentage of hot metal from 40 to 78 pct, with other factors nearly constant, decreased the net heat by only some 5-10 pct. The net heat is increased by about 1.2 pct for each I pct of the metallic charge present as cold pig. Calculated values of oxygen supplied by air varied from about 25 up to 60 lb per ton of steel, and in a 60 pct hot metal practice, an increase from 32 to 52 Ib oxygen from air decreased the calculated net heat from 0.88 to 0.74 million Btu per ton. Use of pure cold oxygen to substitute for about one half of the total charge ore (about 28 Ib oxygen replacing 145 Ib ore per ton of steel) decreased the

Jan 1, 1949

By E. C. Harder

CERTAIN typical characteristics of bauxites, ores of aluminum permit their classification into a number of categories, each of which has special features that enable grouping within it deposits from widely scattered bauxite fields. There may be local variations in conditions that have introduced differences of lesser importance between similar deposits in different fields, resulting perhaps from the influence of factors other than those that have produced the distinguishing features of each of the different groups, but in general the similarity between the deposits in each group is sufficiently striking to make the grouping indicated of interest. Several factors and conditions enter into the decomposition process that results in the development of bauxites and laterites and affects their character. The principal conditions favoring optimum bauxitization are: (1) pres- ence of rocks with easily soluble minerals yielding residues rich in alumina; (2) effective rock porosity, enabling easy access and free circulation of water; (3) normal to abundant rainfall alternating with dry periods; (4) vegetation, including bacteria, advantageously distributed; (5) available sources of appropriate solution and precipitation agencies; (6) a tropical or at least a warm climate; (7) low to moderate topographic relief, allowing free movement of the water table but a minimum of erosion; and (8) long quiet periods in earth history. Assuming that all of these factors are operating to a greater or less degree, it seems that the one that affects most the physical character of the resulting bauxite or laterite deposits is the chemical and mineralogical composition of the rocks that by their decay yield the bauxite deposits. This factor is used in the classification followed in this paper. In the process of weathering of ordinary silicate and carbonate rocks of the earth's crust, whether of igneous or sedimentary origin, it is the minerals of the alkalies that yield most readily to attack. The alkaline earth compounds also offer no great resistance, particularly the carbonates. Thus, among the rock-forming elements, those producing the most insoluble compounds are aluminum, iron, and silicon, together with certain ones of less importance, such as titanium, manganese, and phosphorus. In normal weathering processes such as prevail in temperate regions, the common minerals of rock decay are

Jan 1, 1952

By Comfort Adams

WHEN this country went into the war, but two concerns, The Bethlehem Steel Co. and The Midvale Steel and Ordnance Co., knew how to make steel fit for great cannons and at these concerns there were relatively few men who knew the whole art. Fortunately, certain of these men put their knowledge at the service of the Government, and proceeded to instruct the metallurgists at the arsenals and at various steel works. The then chairman of the Engineering Division of the National Research Council, Doctor Howe, suggested that this work might be facilitated, and the number of effective gun-steel makers thereby increased, if a detailed description of the best practice could be written, giving the reasons for the various steps, and issued with the endorsement of a committee composed of those who were evidently the most competent authorities. It was thought that something would be gained by clarification of the subject, and something by the eminent authority' of the members of the committee. To that end, the Engineering Division appointed-a committee, consisting of the gentlemen whose names follow, to mention only those who retained their connection with it. At, this time there were serious difficulties in the manufacture for the Government, of aircraft and high-speed engine crankshafts, of certain ordnance forgings, and of shells for both the Army and Navy. This Committee was asked to study and report upon these, with a view to betterment of practice. There were indications that the source of some of the difficulties went back to the melting of the steel and the production of the ingot. Hence, the committee first studied steel melting and ingot production, in order to guide the wartime manufacturers to an even larger percentage of useful production from the steel initially melted.

Jan 1, 1922

By Arthur F. Taggart

PROGRESS in a technical art is of several kinds. It springs .from many diverse sources. It comprises invention, mechanical improvement, operating advance, analytical study, education. Invention is, by definition, a relatively great, essentially individual step, taken quickly. Operating advance is the slow, cumulated march of practice; in contrast, it moves at the pace of the tortoise, but over, the years its effects rival and, in some cases, surpass those of invention. Mechanical improvement- is a usual concomitant of the reduction of invention. to operating practice; thereafter it is a primary tool of operating advance. Analytical study is the process of mental digestion of the fruits of invention and practice. Its purpose is to render these into a form assimilable by the art as a whole, and by the perennial crop of would be practitioners. Education, disseminating the results of such study, consolidates and maintains the positions gained. Thus, slowly at first, but continuously accelerating, the tide of progress grows- to flood. Such growth, in mathematical parlance, is expressible in the general form y = mxn, where x is time, n is some positive number greater than one, m is another positive number, and y is the state of the action at instant x. When n is 2, the readers will recognize the graph of the equation as one branch of the familiar square parabola, whose property it is to become parallel to the y-axis; i.e., to move at an infinite rate, in that never-never

Jan 1, 1947

By William Fink

THE investigation of the phase relations of high-purity aluminum-base alloys is a part of the fundamental research program of the laboratories of the Aluminum Company of America. The results of a number of binary and ternary systems have previously been published in the transactions of this society. The aluminum end of the binary aluminum-titanium system has been studied. This system has received relatively little attention. To the authors' knowledge, there are two previous papers on this subject. E. van Erckelens1 determined the constitutional diagram reproduced in Fig. 1. .According, to this diagram, the liquids represents the separation of TiAl4 (Ti = 30.7 per cent.). He concluded that this is the composition of the compound, because in his work the eutectic horizontal terminated at 30.7 per cent. titanium and the metallographic examination of a sample of this composition revealed only one phase. According to the constitutional diagram developed by W. Manchot and A. Leber,2 reproduced in Fig. 2 from data given in their article, the liquidus represents the separation of the compound TiAl3 (Ti = 37.2 per cent. ). The composition of the compound was derived in a manner similar to that utilized by van Erckelens. Moreover, Manchot and Leber confirmed the composition of the compound by analysis of the constituent left as a residue after dissolving the alloys in weak sodium hydroxide solution. Although these are the only publications describing the constitution of the system, other investigators have studied the composition of the titanium compound. L. Wöhler3 says that there is a compound TiAl3 which was later confirmed by W. Manchot and P. Richter4 and by

Jan 1, 1931

By L. D. Ricketts

' In recent years the metallurgical field of the copper industry has expanded greatly, the copper ores have become lean add diverse in charactcr, and we are obliged to treat such ores on a very large scale. On the commercial side, the operating and consulting staffs of the great mining companies have been enlarged and organized, and no great capital expenditure is decided upon until it has been investigated and recommended by a highly organized force of specialists as a committee. I believe that in the scientific field and in the most valuable proceedings of our -various societies the old idea of one-man point of view and one-man treatment of principle and detail together has been splendidly developed and should continue, but for the advancement of our art we should deliberately discuss subjects among ourselves in order to do away with the idiosyncrasies of the individual and to gain a composite view reprcscnting the best thoughts of many men. In the development of new ideas leading to the introduction of new methods, the societies could enlarge their present great field of usefulness if such discussion be had, and in my opinion further great good could be done if a number of men of different qualifications and experience would join in preparing a joint book, each dealing with his particular problem, but consulting the other men. In this way individualism would be preserved and various processes would be described, and if properly reviewed the paper would be palpably capable of analysis, and the student would have at his command the associated efforts of a group of qualified engineers. I have neither the time nor the qualifications to make an investigation and study in detail of hydro-metallurgical processes, but for some years I have foreseen the development of such processes, and I have a deep interest in the subject and have given some of its phases careful consideration from a long-distance viewpoint. I have assisted in directing many experiments and in reviewing the merits of many processes, and am glad to make some introductory remarks with the understanding that other gentlemen present will freely and candidly enter into the discussion and help to fill out the few bare bones that I can uncover.

Jan 1, 1916

By H. S. Kalish, F. J. Dunkerley

Introduction and Previous Work THE determination of the low temperature tensile properties of tin and tin-lead alloys was initiated as part of an extensive research program on the phasial equilibria of tin binary systems below 13.2°C and the property changes associated therewith. A survey of the literature revealed that, although some room temperature tensile data were available for tin and a few tin-lead alloys, there existed no survey report of the low tcmPerature tensile properties of these alloys. Accordingly, the tensile data for tin and a series of pure tin alloys containing from 0.01 to 50 pet lead were measured at eleven temperatures horn — 196 to +20°C and are presented here in survey form. In addition to the importance of these tensile data as a preliminary to certain fundamental research, this information promises also to be of commercial importance because of the extensive use now being made of tin-lead solders in refrigeration and gas liquefaction equipment. Occasional failures of the solders in low temperature service have been attributed by some metallurgists to low temperature embrittlement, while others hold that failure results from the transformation of the tin-rich phase of the solder from the solid white (beta) to the powdered gray (alpha) form. From the data previously available in the literature, neither of these explanations can be completely corroborated. cohen and van Lieshout have estab-lished the beta to alpha tin transformation at 13,2°C and have shown that strain accelerates the transformation. Further, they showed that although I pct lead retarded the transformation, it was not eliminated. It will be pertinent, then, to note whether the beta to alpha transformation of the tin.rich phase will occur in a short-time tensile 'test. polanyi and schmid2 studied the tensile properties of tin single crystals at — 185°~ and report that tin is britlle at this tem-perature. In 1946, Kostenets3 reported that pure tin was brittle at —Ig6 and — 253°~, while lead remained ductile at both these temperatures. He also studied the tensile properties of tin-lead alloys containing from 10 to 75 pet lead at —253, —196 and + I~OC. The ultimate tensile strength increased more than two times in going from room temperature to — I96°C and about three times that value on further cooling to — 253 C- All the alloys were brittle at — 196'C except those containing more than 75 pct lead. Even at — 253'C, the 75 pct lead alloy retained 36 pet elongation in a 30 mm-ga. length. Creep is also an important phenomenon

Jan 1, 1949

By R. E. Hobart

The development of the Hauto power plant and the claims made by various engineers that electricity was more economical than steam for power purposes in and about the mines, led the Lehigh Coal and Navigation Co., in 1911, to conduct a test to ascertain the consumption of power used by a large steam hoisting engine. The question being one on which no reliable information could be found, and the opinion of various engineers differing to such an extent, it was decided that a test under actual operating conditions was necessary. This was arranged for at one of the collieries. The engine selected was 2 30 by 60-in. (76.2 by 152.4-cm.) piston-valve engine of modern type, and comparatively new. The boiler plant from which the hoist received its power was about 600 ft. (182 m.) from the engine, the latter being fed by a 10-in. (25.4-cm.) steam line insulated with magnesia pipe covering. Two batteries of the boiler plant, aggregating 1200 hp., were cut off and fed into a separate steam line leading direct to the hoist engine. Steam auxiliaries, consisting of feed-water pump and blowers, were fed by the boilers in test, and their consumption charged against the hoist. A barrel weighing device was installed, as it was felt that this would be the most accurate way of determining the consumption of water. The fuel, No. 3 buckwheat, was carefully weighed, and every precaution was taken to make the test accurate in every particular. The test was run for 1 week, or a total of 168 hr. A record was kept of the number of trips hoisted or lowered, and continuous indicator cards were taken. One particular set of cards was taken with the hoist operating balanced, and also with the hoist operating with no counterweight other than the empty cage, the coal in the car being weighed. The speed of the hoist was taken by means of a graphic recording instrument which registered the number of revolutions every 5 sec. From this record, speed-time curves were plotted.

Jan 1, 1918

By G. R. M. Del Giudice, A. F. Taggart, Othon A. Ziehl

In a previous paper1 in which one of the authors collaborated, it was postulated that All dissolved reagents which, in flotation pulps, either by action on the to-be-floated or on the not-to-be-floated particles affect their floatability, junction by reason of chemical reactions of well recognized types between the reagent and the particle affected. This generalization, apparently, like many pioneer structures, had for certain observers a flimsy appearance, and these, judging its stability rather by the number than by the character of its foundation posts, have attempted variously to overthrow it, either by the frontal attack of general denial, or by the flanking movement involved in assuming that those cases in which the facts were unknown or unproved were, therefore, discordant. But as time has passed and further evidence on the question has accumulated, it has become apparent that the results of verifiable experiments add stone by stone to the substructure of the hypothesis, and that the super-tructure has lost nothing in weathering. The present paper constitutes an examination of the opposing positions in the light of the more recent evidence developed. It will clarify the discussion if, at this point, we state more fully the implications of the disputed hypothesis. In the first place, it is explicitly limited to reagents that are dissolved in the water of the flotation pulp. Next, it refers only to such of these dissolved reagents as act on the solid particles in the pulp to affect their floatability. This includes the collectors, activators, and certain depressors and gangue-control reagrnts, but not the pure frothers, and not, necessarily, conditioners whose function seems to be merely that of pH control, although in certain cases it has been demonstrated that such control has the effect of regulating the primary reaction of the collector, depressor, or the like. Finally, there is no limitation as to the nature of the chemical reaction postulated.

Jan 1, 1935

By F. H. Parsons

At the time that converting or bessemerizing of copper matte first began to be practiced by the smelters in the copper industry, converters were lined by tamping the flux, usually siliceous ore, into the steel shell. About 1910, practice in several plants had demonstrated the superiority of a basic lining of nonfluxing material and the addition of flux through the mouth of the converter. Adoption of the new method by nearly the entire industry followed. Basic linings are made of refractory "magnesite" brick manufactured, usually, from imported dead-burned magnesite. Either the linings are laid up in the shell dry or the bricks arc bonded with some mortar dictated by the preference of the user. Foreign, usually Austrian, magnesite was the main source of supply for these bricks, although there were domestic sources, but it was not until costs began to rise a few years after the first use of basic linings that these domestic sources were investigated to any great extent. Exigencies created by the World War necessitated the use of the domestic magnesite during this period, but the brick manufacturers reverted to the use of the foreign product after the war, because the impurities therein made a brick with a better fire bond than the purer domestic magnesite. Therefore the domestic product became available at a favorable price for any metallurgical process that permitted its use. The United Verde converting practice using magnesite linings has resulted in a high consumption of magnesite because of the zinc content of the low-grade matte. It was realized that the cost of these linings represented a large portion of the cost of converting, and an investigation was started to find means by which these costs might be lowered. In the neighboring state of California rather pure magnesite was being mined and treated for the market. The product, however, was purposely made to simulate the dead-burned grain magnesite product from foreign sources by the addition of fluxing impurities before burning. It was learned that this dead-burned California grain magnesite could be laid down in Arizona at a price one-third that of the same tonnage of "magnesite" brick manufactured from foreign magnesite. It was also learned that at least one California producer was ready to supply the market with periclase, which was a grain magnesia produced by burning the

Jan 1, 1934

By W. L. Eaton, S. H. Ash

A barrier pillar in the anthracite region of Pennsylvania is a portion of the bed that is left unmined along the property line or lines of adjoining mining properties, or between mines, or between parts of mines. Barrier pillars perform important functions in anthracite-mining operations. Their principal function is to act as dams to prevent water that accumulates in a mine from suddenly breaking into an adjacent mine or into adjacent mine workings and causing loss of life, property, or both. More than 83 billion gal of water is impounded in II; underground water pools in anthracite mines.1,2 These pools are confined by a system of barrier pillars which separate adjacent mines. The principal factor that threatens to cut short the life of the anthracite industry, to curtail production, and to affect the economic structure of the people and business dependent on anthracite for their livelihood is the inundation of anthracite mines.l,2,4,13,29 To obtain a clear picture of the anthracite mine-water problem, it is necessary to understand the part played by the barrier pillars that separate adjoining mines. Purpose of Report The purpose of this report is to show the methods of determining the size of barrier pillars in the anthracite region, to present the hazards that exist because of the lack of sound engineering being applied to the size of many existent barrier pillars, and to suggest a method whereby barrier pillars can perform the function for which they are intended. The Barrier-pillar Problem Article 111, section '10, of the Anthracite Mining Laws of Pennsylvania reads thus: It shall be obligatory on the owners of adjoining coal properties to leave, or cause to be left, a pillar of coal in each seam or vein of coal worked by them, along the line of adjoining property, of such width that, taken in connection with the pillar to be left by the adjoining property owner, will be a sufficient barrier for the safety of the employees of either mine in case the other should be abandoned and allowed to fill with water; such width of pillar to be determined by the engineers of the adjoining property owners together with the inspector of the district in which the mine is situated, and the surveys of the face of the workings along such pillar shall be made in duplicate and must practically agree. A copy of such duplicate surveys, certified to, must be filed with the owners of the adjoining properties and with the inspector of the district in which the mine or property is situated. Mining practices with regard to barrier pillars have varied greatly since mining began. In many anthracite mines the barrier pillars have been weakened or punctured. As a consequence, the condition

Jan 1, 1949

By Roberts H. Richards

It is nearly twenty years since Dr. Raymond, then U. S. Commissioner of Mining Statistics, wrote the first paper (so far as I have been informed) upon the education of tile mining engineer, as a distinct profession for American youth. At that time nearly all the prominent mining engineers in the country had studied in one or more of the foreign schools, or had reached their high standing through years of experience in the school of life. The paper mentioned five schools in the United States in which some attention was paid to the teaching of mining engineering, but as four of them had barely graduated their first classes, their influence had not begun to make itself widely felt. Two years later the American Institute of Mining Engineers was formed, and it has been a most potent factor in the problem of "disseminating information on mining and metallurgical subjects," so potent that the need of a national school of mines as headquarters for information as well as for instruction is no longer urged. The number of schools also increased, and in 1876 Abram S. Hewitt, in his Presidential address on "A Century of Mining and Metallurgy in the United States,'' gave a list of fourteen. In 1876 the series of discussions, led by Holley's admirable paper, brought the whole subject of technical education before the country. These discussions, while mostly devoted to the engineering professions in general, touched upon the question of mining and metallurgicel training to some extent. Since that time several papers, inspired by the publication of that series of discussions, have appeared in our Transactions, and several notable addresses have been delivered at the opening or at the commencement exercises of various schools. But nothing directly bearing upon the curriculum of the mining and metallurgical schools has ever appeared in our annual volumes. As education is one of the many-sided subjects which cannot be discussed too often, I have ventured to bring it up again. There have been so many good things said upon the subject that one would only need to use the scissors and paste-brush judici

Jan 1, 1887

By T. M. Morris

THE rate of flotation of solid particles determines the percentage recovery of these particles which can be obtained during a given time interval. It is an established fact that the recovery is greatest in the fine sand size range and falls off on either side of this size range. It is also a fact that the history of the development of concentrating devices has been marked by a desire to recover the small particles: tables were developed to treat material too fine to recover in jigs; flotation recovers material too fine to be recovered on tables. As our ores become more complex and require finer grinding, a greater proportion is in the slow-floating size range. It is therefore of economic importance that the effect of size of particle upon rate of flotation be studied. Many studies have been made along this line. The present investigation attempts to quantify the rate of flotation by means of a rate equation, and then compares the effect of size upon the rate of flotation. It was found that the flotation rate constant increases with increase in diameter of particle in the size range smaller than the optimum size particle. The flotation rate constant decreases with an increase in diameter of particle in the size range coarser than the optimum size particle. This suggested two different actions taking place, and these are discussed. Suggestions for further work in order to improve the flotation rate of both fine and coarse particles are made. The usual method of expressing rate is to plot cumulative percent recovery vs time. If we knew the equation of this kind of curve we could replot it as a straight line, and the slope of the line would be an index of the magnitude of the flotation rate. It is easier to compare straight lines than curves. The basis used for obtaining the equation of the recovery vs time curve is the law of mass action. This law states that the "rate of a chemical reaction is proportional to the 'active masses' of the reacting substances present at any given time." This, of course, implies a constant temperature. We can modify this for our use by using the term flotation reaction instead of chemical reaction and the term floatable particle instead of active masses. dC Thus----— kc [1] where C denotes concentration of particles, t denotes time, k denotes a proportionality constant. If the exponent of C is 1, then we have a first order rate reaction. If the exponent of C is 2, then we have a second order rate reaction. For a first order rate reaction, we obtain, after integration, where k is again a proportionality constant and has the dimension of the reciprocal of time. C, is the original concentration or weight or percentage of floatable particles. C, is the concentration or weight or percentage of floatable particles remaining in the flotation cell after time t. If all particles of the mineral to be floated were capable of floating we could take C, as 100 and C, would be 100 - R, where R is the cumulative percentage recovery of mineral at time t. But it is not usual for all of the particles to be capable of floating, because of surface oxidation, etc. Therefore, we must introduce a factor x which is the percentage of un-floatable mineral. Hence the first order equation is It has been proposed by various workers1-' that this equation describes the flotation rate. More recently N. Arbiter4 states that a second order rate equation fits the recovery vs time curve more closely than does a first order rate equation. Morris- as discussed the evidence presented for this statement. It has been concluded that the first

Jan 1, 1953

SEC. 1. The membership of the Institute shall comprise seven classes, namely: 1. Members; 2. Honorary Members; 3. Senior Members; 4. Associates; 5. Junior Members; 6. Rocky Mountain Members; 7. Junior Foreign Affiliates. All shall be equally entitled to the privileges of membership, excepting that no member of any class whose residence shall be outside of the United States of America, except those residing in Mexico and Canada, shall be entitled to vote. SEC. 2. Members: A person to be eligible for election or transfer into the class of Member must be at least 27 years of age and must have had at least six years' employ¬ment in the practice of engineering, mining, geology, metallurgy, or chemistry, during at least three years of which he must have held positions of responsibility in one or more of these fields. This shall not apply to Rocky Mountain members. SEC. 3. Honorary Members: Each candidate for Honorary Membership must be recommended by at least ten Members and must be elected by ballot at a meeting of the Board of Directors by the unanimous vote of the Directors present; provided, how¬ever, that the number of Honorary Members shall at no time exceed twenty. Such election shall automatically act as a transfer of such member from any other class of membership to which he may belong. SEC. 4. -Senior Members: The Directors may in their discretion place on the Honor Roll of Senior Members and transfer from any other class of membership other than Honorary Membership the name of any Member or Associate who has reached the age of seventy years and who has paid dues for thirty years, and for good reasons in special cases may vary the age or number of years. SEC. 5. Junior Members: A person to be eligible for election to the class of Junior Member must be qualified through education or experience to hold a subordinate position in engineering, mining, metallurgical, geological or chemical work. He shall be not more than 33 years of age at the time of election. SEC. 6. Associates: A person eligible for election or transfer into the class of Associate shall be one, who, in the opinion of the Committee on Admissions and the Board of Directors, is suitable for such election or transfer by reason of his interest in or connection with mining, geology, metallurgy, or chemistry. SEC. 7. Rocky Mountain Members: Membership in a special class of life member¬ships without annual or other dues and without right to receive the printed literature distributed to other members or the right and privilege of wearing the official badge of technical members, is given to all members of the Rocky Mountain Club at the time of consolidation. These special Rocky Mountain memberships shall be claimable by any member of the Rocky Mountain Club, not already a member of the Institute, availing himself of the privilege within ninety days after mailing of notice to him, by the Secretary of the Institute. SEC. 8. Junior Foreign Afliate: Upon appropriate action by the Board of Direc¬tors and with its approval, members in good standing of any technical society having its headquarters outside of the United States of America, Canada, or Mexico,

Jan 1, 1937