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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 Arthur Hixson

ALTHOUGH a few engineers have recognized the problem of the mechanism of filtration it has never been studied in a quantitative way. A background for a better understanding will be afforded by a survey of certain fundamental principles of filtration. In recent years, authorities have become practically unanimous in saying that the actual filtering should be done, not by the cloth itself, but by a layer of solid particles deposited upon it. Thus, a cloth may be used in which the openings are considerably larger than the particles to be filtered, provided that groups of particles form an arch or bridge over each opening. This can be accomplished if the initial pressure is so low that the arch will not be broken while it is still thin. According to Wright,1 the chief advantage of this method of filtration is that the open-weave cloth does not become clogged as easily as does one of closer weave, where the fine particles often work their way into the interior of the cloth and become caught there. If the character of the material to be filtered is such that it will not form a good film, then it becomes advantageous to use "filter aids" for pre-coating the cloth with a desirable layer of solids, and the coating need be only of a very slight thickness for good results. Until the film is formed, the first runnings of the filtrate may be cloudy, often necessitating refiltering this portion. A factor which has considerable effect on the performance of filters is the concentration of solids in the pulp. According to Wright, a. high concentration of solids gives a porous cake, since the flow is then slower than with- a thin pulp. The porosity of the cake is also affected by the pressure: a high initial pressure tends to compact the cake, and the same effect results from fluctuations of pressure. In his studies of the relation between pore size and particle size, Hatschek2 observed that the particles in a pulp tend to arrange themselves with maximum cross-section parallel to the direction of flow and that this is more marked at the higher velocities. Thus, at high pressure and high velocity, a certain pulp

Jan 2, 1926

By Wilbur Nelson

IN 1839,1 Gerard, Troost, the first, State Geologist of Tennessee, reported the occurrence of zinc ores in East Tennessee, in connection with the iron ores at Embreeville; in 1844,2 he refers to the zinc deposits of East Tennessee, especially the apparently rich deposits occurring, in Jefferson and Claiborne Counties, while his ninth annual report is a ,description of the zinc deposits of Jefferson County and a description of the most improved processes by which zinc is extracted from its ores. Although. Tennessee has long known of the occurrence of its zinc deposits and has recognized their value, only during the last few years have these ores been successfully worked. As far as can be learned, prior to the systematic development of the Mascot district in 1911, no large-scale or successful operation of any of the zinc deposits was carried on. But in that year, after several companies had made considerable progress in developing the Mascot area and had proved. a relatively extensive body of low-grade sulfide ore, the American Zinc Co. entered the field. It introduced modern methods of prospecting and mining the ore and from the first was successful. Too great credit cannot be given this company for its pioneer work in a previously unimportant field. Throughout the history of its operations, the American Zinc Co. has confined its efforts to underground mining of the sulfide ore, sphalerite. This company has found that successful results in zinc mining in East Tennessee can be achieved only by expending large sums in prospecting and blocking out bodies of pay ore in sufficient magnitude for large-scale operations. At Mascot are located the mines of the American Zinc Co. of Tennessee, the mines being situated along the Southern Railway in the Holston River Valley, Knox County, about 13 miles northeast of Knoxville. Considerable mining and prospecting had been done by several companies prior to the acquisition of this property by the, American Zinc Co. Previous to 1900 only open pits, which were worked for oxidized ores, were operated. and the production was small. In 1900 the

Jan 10, 1924

By J. Laskowski

J. Laskowski (Associate Professor, Dept, of Mineral Processing and Coal Preparation, Silesian University of Technology, Gliwice, Poland) -Referring to the papers by J. A. L. Campbell and S. C. Sun, I must say that I am very pleased to see that type of work, because it is the only way to progress towards an understanding of flotation mechanisms. All those interested in the science of the surface chemistry of coals would find these papers a valuable contribution to the literature. In their extensive research, the authors attempt to synthesize their findings into a theory of coal flotation. To do this, the zeta potential of bituminous coals and their lithotypes, as well as that of an anthracite coal, was measured and H+ and OH- ions were found to be potential determining ions. The measured ZPC of bituminous coals was at a pH range from 3.5 to 4.6 and for the anthracites between 2.0 and 4.5. The authors have pointed out that since the hydrophobicity is pH-controlled, the flotation mechanism should also be. The Campbell and Sun papers confirm a good many of the conclusions on surface properties of coals reported in recent years. It is noteworthy to point out that the ZPC found in the paper on bituminous coals was approximately pH 4, similar to the ZPC for the anthracite coal. In fact, we have been investigating different coals from low to high ranks. Thus, the plot of the pH for ZPC against rank could be derived and this curve-an electrocapillary one-indicates a pH near which the hydrophobicity of the coal surface should be at maximum. This can be proved by so-called salt flotation, which, in a sense, can be treated as method of surface charge measurement. It is obvious that the salt flotation experiment is possible when the native hydrophobicity of the mineral surface is high, e.g., when the solid surface does not have an orienting influence on an adjacent water layer and the hydration layers are controlled by the electrical double-layer potential. The addition of electrolyte or a change of pH which decreases the thickness of the stabilizing double-layer "opens up" the hydrophobic surface micro-area mosaic. Thereby the surface becomes hydrophobic and particles become floatable. The orienting influence of surface on hydration layer increases even after very slight oxidation and flotation is affected by it. It seems that such an explanation agrees reasonably well with those of Campbell and Sun.

Jan 1, 1972

Without having asked for it, the writer has apparently been drawn into the discussion regarding relative hoisting capacities which was started by Woodward Iron, egged on by Joe Haller of Cleveland-Cliffs [Mining Engineering, August p. 642] and Axel Kjelgaard [November p. 919], who took exception to Mr. Haller's remarks of tonnage hoisted and avers that they do better in Sweden. It does not appear to the writer that Mr. Haller was inclined to refer to the tonnage hoisted at Cleveland-Cliffs in a manner to imply that they claimed any hoisting record, but rather as a statement that they had hoisted a certain amount of ore during the year 1950. Mr. Haller has been in the mining game long enough to appreciate what Mr. Kjelgaard did not apparently take into consideration, that length of haul, shifts hoisted, nature of ore, method of loading and the many other factors which influence the hoisting cycle make a comparison of tonnages hoisted of two given mines almost an impossibility. Mr. Cheyette sent you .a copy of his letter to Bob Manegold relative to the capacities of the Orient #2 mine. There are several mines around the Country which constantly set up records about which little or nothing at all is ever heard. We cite the Snow Hill Coal Co. mine at Terre Haute, Ind., which has an automatic Nordberg hoist and which hoists 12 tons per trip or 700 tons per hr from 700 ft. This is a counter-weighted installation and a complete cycle is made every 62 seconds or 58 trips per hr. Another mine, The Potash Company of America mine at Carlsbad, N. Mex., has a Nordberg automatic hoist, hoisting eight tons per trip from 1150 ft on a one minute cycle. The materials hoisted in these two mines are ideal for automatic hoisting-they are free flowing so that no hang up is anticipated and hoisting is continuous. Multiplying out the above figures you will find that it is possible to hoist 11,000 tons in two shifts at Snow Hill or over 3 million tons in 300 days per year and over 2 million tons at Potash. Other mines have records which can be pointed to with pride. When a record for one year is established, it doesn't stand too long as here in America the ambition of all the men connected with the operation forces them on to larger tonnages. T. C. WIEDENHOEFER MANAGER MINE HOIST DEPARTMENT NORDBERG MANUFACTNRING CO. MILWAUKEE, WIS.

Jan 1, 1952

By D. F. Haley

The molybdenite deposits at Climax, Colo., have recently attracted considerable notice, because of their great size, as compared with other known deposits of the same mineral. Climax station, on the Colorado Southern narrow-gage railway, was at one time the Fremont Pass station on the Denver & Rio Grande. It is 141/2 miles northeast of Leadville, and exactly on the divide between the headwaters of the Arkansas and Blue Rivers. Climax station is 11,300 ft. (3444 m.) above sea level. The working tunnel of the molybdenum mine is about 1 mile from the railroad, and 900 ft. above it, at an elevation of 12,200 feet. The climatic conditions are severe, and snow can be expected during any month of the year. Winter sets in not later than Nov. 1, the snowfall is very heavy, and the ground remains covered with snow until June 1, and sometimes even later. From June 1 to Oct. 1, there is much rain and a little snow falls in the late afternoon nearly every day. In October, 1917, there was one of the biggest snowstorms and blizzards of the year. Being just on the divide, constant strong winds blow the fine, dry snow with such force that, during most of the winter, outside work of any kind is accomplished under most trying conditions. Within a few miles of Climax, some of the richest gold placers of Colorado occur. One of them, McNulty Gulch, was just across on the northeastern flank of Bartlett mountain. This mountain, therefore, was well prospected, and the presence of a bluish mineral and a yellowish one resembling sulfur was known to the old prospectors. They thought for many years that the blue mineral was graphite, and it is difficult to say when it first became definitely known that it was molybdenite. Claims had been staked as early as 1896, but it is evident that the prospectors at that time were looking for gold. In 1902, several claims were acquired by H. Leal, who drove a tunnel about 900 ft. (274 m.) long, probably to intersect a fault, which shows on the surface, and was thought to be a possible gold carrier. Gold was not found in paying quantities, but throughout its length the tunnel passed through a fractured silicified granite, showing a fairly uniform distribution of a fine-grained bluish mineral, which was finally determined as molybdenite. For several

Jan 1, 1920

By W. L. Chu

It was observed that chromized coatings on low carbon steel could be embrittled by cooling slowly through the 475°C range. A higher chromium coating was more susceptible to embrittlement than a lower chromium coating. Coating structure and composition could be correlated with the chromizing process and prior carbon content of the steel. IT was recently observed that during the fabrication of rectangular tubings made with chromized thin gage 1010 steel, a high percentage of these parts were fractured readily in a brittle manner under the light impact-forming load employed. Ensuing investigation indicated the cause for such brittle failures to be the so-called 475°C embrittlement of the chromized coatings. The experimental work and results are briefly reported. Rectangular tube sections of normalized AISI C1010 steel, which had a cross-section of 0.5x1.5 in. and a wall thickness of 0.030 in., were chromized to yield coatings having several ranges of thickness, varying from 0.0005 to 0.002 in. Essentially, the chromizing process is similar to that described by Samuel and Lockington,' which consists of heating the parts in a sealed container at about 955°C for 4 hr in intimate contact with a chromizing mixture* samples in a hydraulic press, and the other employed a simple beam bending test of the flat sides of the tubing walls. Neither, however, was able to differentiate the relative brittleness of samples known to include both the brittle and tough types, since the impact-brittle samples were found to deform readily in a manner similar to the tough ones. Both the tough and brittle samples were studied by reflection microscopy. Observation showed that the microstructures of the steel cores were similar in content and distribution of inclusions as well as in the ferritic grain size. Results of Filar micrometer measurements showed that coating thicknesses+ of the brittle samples averaged 0.0007 in., whereas those of the tough samples averaged 0.0016 in. The micrographs of Fig. 2 illustrate the structural differences between coatings of both types of samples. By dissolving the steel cores in nitric acid, coatings of both the brittle and tough samples were isolated. Simple bending tests showed that coatings of the brittle samples cracked readily at about 90" bend, whereas those of the tough samples could be bent nearly 180° without cracking. The coatings as well as the steel cores were analyzed for carbon and

Jan 1, 1956

By Hans E. Gustafsson

INTRODUCTION The Kiirunavaara iron ore mine is situated in northern Sweden about 150 km north of the Arctic Circle. The ore body has a sheetlike shape, stretches about 4000 m N-S dipping 60°E and has an average width of 85 m. The ore body is known to a depth of more than 1500 m. Mining at present has reached a depth of about 500 m. The mineral is a magnetite containing 66-68% Fe. The ore body was originally mined as an open pit from 1900-1957. From then on the mining method has been sublevel caving. Production for the last few years has been 20-25 million tons /year. Sublevel caving is a mining method with many merits. One of the most valuable is the ability of using a high degree of mechanization. Today, 25 years after sublevel caving was introduced at Kiirunavaara, the advantages of the method have been more or less exhausted, and the disadvantages are more obvious as the rock pressure increases with depth. One of the disadvantages is the high degree of waste rock in the hoisted ore. Today the waste rock content is about 25% by weight of which 20% comes from the caved rock. Second, we are calculating a relatively high loss of ore (20%). Third, selectivity is unsatisfactory when mining different grades of ore. Field testing sublevel shrinkage caving (MSTM) is primarily aimed at lowering the content of waste rock compared to sublevel caving. ECONOMIC TARGET A simple calculation shows that if the waste rock content can be lowered from 25 to 15% the operational costs of mining will be lowered by about 40 million SEK/year (US $9 million) at a production level of 20 million tons/ year. A 15% waste content is the target of the field test. In the long range a decrease in waste rock dilution will mean lower investment costs for deeper levels. DESCRIPTION OF THE MSTM MINING METHOD One reason for decision to carry out the field test was that with MSTM the development drifts from sublevel caving could be utilized and thus the project could start without delay. The only additional development work needed was the loading level. Fig. 2 shows a profile through the MSTM area 66-68% Fe. and Fig. 3 shows the loading level.

Jan 1, 1981

By J. B. Cohen

In an investigation of the microstructure of shock-loaded metal specimens1 C. S. Smith found that there was little distortion of grain boundaries or change in external dimensions, although the hardness corresponded to that produced by severe rolling. Furthermore, the hardness of individual grains was independent of the deformation structures present; grains with no markings were as hard as those heavily populated with markings. These markings which resemble twins do not appear in copper until high shock-loads of the order of 200 kb are applied. It appears that due to the high velocity of a shock wave and its sharp front, heavy deformation takes place on a submicroscopic scale. In this work an attempt was made to examine this deformation, particularly at a load below which macroecopic markings appear. The broadening of 200 and 400 diffraction peaks was examined from the face of a poly crystalline sample normal to the direction of the shock wave. These peaks were chosen because the elastic constants in copper are such that residual strains would be greatest in the <100> directions; hence, the strain-broadening contribution to these peaks would be large in comparison to other sets. Also the broadening due to stacking faults and microtwins would be greatest with this set.2 A complete Fourier analysis of these peaks was made, as described by warren,&apos; using the Stokes correction with peaks from an annealed sample.3 With the aid of the U. S. Army Ordnance Corps EDVAC computer and a curve matching program, sixty sine and sixty cosine coefficients were obtained for each peak. The last of these was about 1.5 pct or less of the largest coefficient, indicating good representation. Transverse sections from a 1.5 in. rod of as-drawn electrolytic tough-pitch copper were reduced in cross-sectional area about 50 pct by cross rolling. Disks 1.5 in. in diam were recrystallized at 275 °C for 30 min and then at 300°C for the same time. The faces were polished and deeply etched in nitric acid to remove 25 mils. The grain size was 0.02 mm. Laue back-reflection patterns indicated the sample was well recrystallized. The two diffraction peaks from this sample were recorded on a Norelco diffractometer using filtered copper radiation. Peak intensities were kept less than 600 cps to assure linearity of the counter and circuitry. This sample was then placed between two rods of the same material and diameter. The top rod was 2.25 in. long and the bottom rod 1 in. long. (In

Jan 1, 1961

I AM sure, that you understand that of all the things created by the most high God Himself or by Nature at His command, not one-even though it be an atom or the smallest worm-has been produced without some particular gift. And if we do not always discern this in every thing, the cause lies in our defective vision, in our little knowledge, and in our lack of careful thought concerning the necessity of seeking hidden things. Certainly those things that have such inner powers, like herbs, fruits, roots, animals, precious stones, metals, or other stones, can be understood only through oft-repeated experience. [37] Others do not need so much knowledge and belief for their, powers are obvious and shown to us at all times by their effects. They reveal themselves to us through the sense of sight by their splendor and variety of colors, through the sense of smell by their odors, through the sense of hearing by the melody of the harmonious or unpleasantly discordant repercussions. of the air. They likewise manifest themselves by. their softness or harshness. As you see, all those things, according to. their limits, are conveyed .by the ordinary senses to the mind, by whose distinctions all their species, both harmful and beneficial, are discerned. Then they are reviewed by the judgment in all their degrees of perfection and imperfection, so that whoever seeks them with careful study or with experience often finds them. Now, in order to shorten this discourse, since I wished to speak to you of lodestone and its properties, I tell you that it is one of those things that show their apparent effects to our sight by a particular virtue hidden in such a way that its cause, as far as I know, has never been known to the very wise natural speculators who have spoken on every other subject. Thus one who considers its actions carefully must surely marvel, for it appears that Nature has put into this stone a certain spirit of vivacity, so that it seems to have-I would like to say-hands, although they are not seen. For I see that it not only attracts iron but also takes hold of it and keeps it attached to itself. This action is certainly great enough to bear certain witness to the virtues possessed by other created things that do not manifest their powers to the external senses. In order not to prolong this discussion, I tell you the following. This stone is found in various places and of different colors and properties. The

Jan 1, 1942

By John Philip Zannaras

John Philip Zannaras (Registered Professional Engineer, Congress, Ariz.)- The authors show in their [Fig. 4] the cumulative results of grinding with two sizes of bails, one 30 mm and the other 20 mm. The Gaudin-Meloy probability for breakage for a single fall used by the authors in their paper is given by their [Eq. 6]. Another form of [Eq. 6] is given by Gaudin-Meloy in their paper as follows: [ ] From the definition of A given by Gaudin-Meloy it is obvious that A30 is greater than A., it therefore follows from the foregoing equation that according to the Gaudin-Meloy formula the probability of breakage for a single fall of all the balls in the 20-mm experiment was more than 2.25 times the probability of breakage in a single fall of all the 30-mm balls which is contradicted by the authors&apos; experimental evidence in [Fig. 4] in which is shown that much more grinding took place with the 30-mm balls. In fact the authors present convincing evidence that the Gaudin-Meloy work is erroneous because their work is based only on a geometric configuration and on ambiguous and uncertain definition of A and disregards the fact that the distribution of fracture depends on other important and indispensable factors including the intensity of stress caused on the feed grain by the balls. That there is an immense and chaotic variation of stresses caused on the feed grains by the balls is shown by a formula, derived by this writer and published in 1955. The derivation of this formula is given in the Appendix of this discussion; it contains the variables in the operation of ball mills and is based on the science of mechanics-not on probabilities. [ ] where T is the unit stress in pounds per square inch produced by the moving load, h is the height in feet through which P has fallen, E is the modulus of elasticity of the rock, P is weight of one ball, and L is the size of the grain (assumed to be a cube of side L). It will be shown by this writer&apos;s formula that when a 30-mm ball strikes any size of feed grain it will cause 1.837 times higher stress than the 20-mm ball when striking the same size grain. It will be shown that when the 30-mm ball or the 20-mm ball strikes a feed grain of 0.1 mm it will cause 90 times more stress on the grain than when it strikes a 2-mm grain.

Jan 1, 1974

By Leonard D. Jaffe, Donald C. Buffum

THE importance of temper brittleness in alloy steels has long been realized in Europe, In the United States recognition of its importance has developed within the last several years. Many brittle failures encountered in parts made of alloy steel are undoubtedly attributable, wholly or in part, to temper brittleness. These failures have occurred particularly at low temperatures, under shock loading, and in the presence of notches, restraints and combined stresses. It has been almost universally accepted that plain carbon steels are not susceptible to temper brittleness. As a result, considerable effort has been expended in attempts to discover the manner in which alloying elements introduce temper brittleness. It is desired to raise the possibility that plain carbon steels are not only susceptible to temper brittleness, but are much more susceptible than alloy steels, in the sense that they embrittle much more rapidly. It is suggested that previous views, (that plain carbon steels are not susceptible), are based upon an erroneous interpretation of the experimental results. INTERPRETATION OF PREVIOUS DATA For many years the standard criterion for susceptibility of a steel to temper brittleness consisted of comparison of the energy absorption, in a notched-bar impact test at room temperature, of specimens that had received two heat treatments.1 One specimen (or group of specimens) was quenched, tempered, and quenched from the temper. The other specimen (or group) differed only in having received an embrittlement treatment, which might consist of a slow cool from the tempering temperature, or of an isothermal hold in the range 450-550°C subsequent to quenching from the temper. If the energy absorption of the specimen receiving the embrittlement treatment was lower than that of the specimen not given this treatment, it was said that the steel was susceptible to temper brittleness, If the energy absorptions were the same, it was said that the steel was not susceptible. Several investigators2,3 found that plain carbon steels showed negligible difference in energy absorption in such tests (at least when their manganese content was below 0.60 pct), and concluded that plain carbon steels are not susceptible to temper brittleness. Recently the deficiencies of the criterion mentioned above have been pointed out.4-6 The criterion now generally used for susceptibility to temper brittleness retains the heat treatments used in the earlier scheme, but instead of the notched-bar impact tests being made only at room temperature, they are made over a range of temperatures, covering the transition from ductile to brittle fracture, If the transition temperature of the specimens receiving the embrittlement treatment is higher than those

Jan 1, 1948

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 C. Fairhurst, A. M. Starfield

As a practicing mining engineer, I face many rock mechanics&apos; problems daily and would like to mention one or two examples to illustrate the current gap between laboratory investigations and actual field problems. I would like to endorse Dr. Obert&apos;s suggestion that more field measurements and observations should be undertaken. There is an ever-increasing body of data beginning with Hast&apos;s results in Sweden,l then measurements at Elliot Lake, Canada, and so on, including our own measurements at White Pine, which clearly indicate that the horizontal stresses underground are often at least as large as the vertical stresses. Visual obsenation of the deformation of roof and pillars (including failure due to horizontal compression) also demonstrates that the horizontal stresses are often most important. Yet almost every laboratory investigation begins with the assumption that the only stresses acting are vertical. Roof spans in layered formations. for example, are calculated on the assumption that the rock behaves as a gravity loaded beam. This is all too often unrealistic. Roof bolts are also often considered to be simply means of suspending the gravity loaded beams. As Dr. Reed has mentioned they are probably, in fact, acting to restrain a beam which is attempting to buckle due to lateral pressure. The fact that moisture can reduce the strengths of some rocks as much as 50 percent has been known for many years. In the mine me are almost always faced with wet rock, yet no one has investigated ways in which this wakening effect can be overcome. as, for example, by waterproofing the rock. C. Fairhurst, University of Minnesota I would like to mention that we have found,2 from stress-relief determinations, that appreciable (over 1000 lb per sq in.) horizontal pressures occur also at the surface in granites quarried in central Minnesota. Whilst I agree that more field measurements are desirable, it is important to point out that most university research is undertaken by graduate students who must attend classes daily. Their research is therefore restricted to the laboratory. A.M. Starfield, University of Minnesota No one denies the importance of obtaining: data from field measurements. It is equally important, however, that field measurements be guided by theory. Much time and money can be wasted by indiscriminate measurement. An example of the value of theory in interpreting measurements is given in Dr. Obert&apos;s comments on the time dependent strain observed in a salt mine. He anticipated that the stress at the wall of the opening would change with time because salt is viscoelastic rather than elastic. It can be shown from theory that if an excavation in a viscoelastic medium is unsupported, then the stress at the wall does

Jan 1, 1967

By Terkel Rosenqvist

Few subjects in iron metallurgy and steelmaking have caused so much discussion and have resulted in so many divergent and partly contradictory statements as the theory of the distribution of sulphur between molten iron and slag. An interesting survey of the different points of view is given by Grant and Chipman.1 Grant and Chipman themselves conclude in their paper that, at least in the open hearth and electric steel furnaces, the governing reaction is a simple distribution like: FeS steel ? FeS alas [Ia] and MnS steel ? MnS alas [Ib] They conclude that no significant reaction takes place according to the more classical scheme: FeS steel + CaO slag ? FeOslag + CaS slag [2a] This is the reaction which is regarded by most investigators as the primary sulphur reaction in the blast furnaces, where it is accompanied by the reaction with carbon: FeO slag + C ? Fe + CO [2b] The writer suggests an alternative to the reactions mentioned above. It is the opinion of the writer that the a priori assumption of defined molecular compounds being present in molten steel as well as in molten slag, has retarded rather than promoted a solution of the sulphur problem. As for the constituents of molten steel, it is taking too much for granted to mention the presence of FeS and MnS. If this infers that the melt contains diatomic molecules, the statement must be made that at least such molecules do not exist in the solid state at room temperature. Solid FeS crystallizes in the nickel-arsenide structure, and MnS (high temperature form) in the sodium-chloride structure. In these structures the sulphur is surrounded by six metal neighbors, and no molecular groups can be isolated. When sulphur is dissolved in molten steel, it is expected to maintain the same coordination number as in the solid state. We know that sulphur in steel has a certain chemical potential and a chemical activity which can be expressed by the reaction: S steel + H2 ? H2S where the activity A. is proportional to the ratio PH2S/Ph2. We know also that this activity is influenced by the presence of other constituents. For instance, there is reason to assume that carbon and silicon increase the sulphur activity and manganese decreases it. However, the exact relationship here is scarcely known, and further investigations are needed. Concerning the molten slags, if anything should be assumed a priori it would be that they are composed of ionic rather than molecular parts. There are indications of this in that solid silicates form ionic structures, and molten slags show high electric conductivity and can be electrolyzed.2 It has been claimed by Taylor and Chipman3 that their activity investigations

Jan 1, 1949

By Terkel Rosenqvist

Few subjects in iron metallurgy and steelmaking have caused so much discussion and have resulted in so many divergent and partly contradictory statements as the theory of the distribution of sulphur between molten iron and slag. An interesting survey of the different points of view is given by Grant and Chipman.1 Grant and Chipman themselves conclude in their paper that, at least in the open hearth and electric steel furnaces, the governing reaction is a simple distribution like: FeS steel ? FeS alas [Ia] and MnS steel ? MnS alas [Ib] They conclude that no significant reaction takes place according to the more classical scheme: FeS steel + CaO slag ? FeOslag + CaS slag [2a] This is the reaction which is regarded by most investigators as the primary sulphur reaction in the blast furnaces, where it is accompanied by the reaction with carbon: FeO slag + C ? Fe + CO [2b] The writer suggests an alternative to the reactions mentioned above. It is the opinion of the writer that the a priori assumption of defined molecular compounds being present in molten steel as well as in molten slag, has retarded rather than promoted a solution of the sulphur problem. As for the constituents of molten steel, it is taking too much for granted to mention the presence of FeS and MnS. If this infers that the melt contains diatomic molecules, the statement must be made that at least such molecules do not exist in the solid state at room temperature. Solid FeS crystallizes in the nickel-arsenide structure, and MnS (high temperature form) in the sodium-chloride structure. In these structures the sulphur is surrounded by six metal neighbors, and no molecular groups can be isolated. When sulphur is dissolved in molten steel, it is expected to maintain the same coordination number as in the solid state. We know that sulphur in steel has a certain chemical potential and a chemical activity which can be expressed by the reaction: S steel + H2 ? H2S where the activity A. is proportional to the ratio PH2S/Ph2. We know also that this activity is influenced by the presence of other constituents. For instance, there is reason to assume that carbon and silicon increase the sulphur activity and manganese decreases it. However, the exact relationship here is scarcely known, and further investigations are needed. Concerning the molten slags, if anything should be assumed a priori it would be that they are composed of ionic rather than molecular parts. There are indications of this in that solid silicates form ionic structures, and molten slags show high electric conductivity and can be electrolyzed.2 It has been claimed by Taylor and Chipman3 that their activity investigations

Jan 1, 1949

Manganese Resources in Relation to Domestic Consumption Discussion of paper by JOHN V. W. REYNDERS, presented at the Cleveland Meeting and issued, as Pamphlet No. 1656-C, with MINING AND METALLURGY, May, 1927. A. G. BETTS, Kinderhook, N. Y. (written discussion).-When a business concern hires an office boy, it takes on the first bright-appearing young chap to apply and pays him the prevailing rate of wages. One of the chief tasks the .office boy is supposed to be competent to perform, is to clean out the office. The manager of the business is highly competent in many lines, but for some reason lacks the ability to keep the office clean. To the steel man, it would seem that manganese is the office boy, and it is purchased just as found and offered to the purchasing agent. The steel mill is competent to perform many functions on a grand scale and with wonderful efficiency, but it is unable to make real steel. It is the function of the office boy, manganese, to do this. It is open to serious doubt if steel mill operators have ever taken seriously the metallurgy of the preparation of crude manganese. It has merely been found that some usable crude manganese may be obtained by running certain manganese ores through an iron furnace when not busy on anything else, or remote from iron ore, or with a lining that is about gone. It is, however, an entirely unwarranted assumption that the metallurgy of manganese has been worked out, or that the supplies of usable raw ore must be limited to materials of some specified analysis. There was a time when ores of copper, lead and zinc, for example, had to be rich and of specified analysis, to be usable, but the commercial raw materials of today bear little resemblance to such ores of the past. The discussions of manganese that I have seen are based on the assumption that the metallurgy of manganese is fully established and that the only usable manganese raw materials are of the kind used today. These discussions contain another error, not so much of statement, but of implication-that the tonnages of manganese materials in the United States are so much in this state and so much in that. When it requires a period of years and the expenditure of millions of dollars for a competent mining company to explore thoroughly a few acres of mining ground, is it not absurd to say that there are so many hundred tons of manganese ore in a certain state? This fact is not apt to be known fully in 10,000, years. I do not charge the mining engineers. who are on record, of making misstatements, because they merely say that so much

Jan 5, 1927

By J. C. Uy, A. A. Burr

IN the primary solid solutions of zirconium-base alloys, there is a striking regularity of the effect of solute valence on the stabilization of the allotropic phases.1 The valences derived by pauling2 are for elements as they are bonded in the solid metallic state. Effects of variations in isotopes, alloying elements, and allotropes on their valences are difficult to determine and such data are presently unavailable. Pauling&apos;s values are somewhat empirical and approximate, but if some definite correlations can be found between those values and experimental observations, this will lend support to the tacit assumption that the possible variations in valence mentioned above are small. Pauling has amassed a large amount of evidence of such correlations. It is the purpose of this technical note to show another application of the Pauling valences and to offer a possible explanation for this observation. The relationship between the Pauling metallic valence of the solute and the stabilization of allotropic phases in zirconium is shown in Table I, which has been compiled from available data in the literature3 plus the results of work done at Rens-selaer Polvtechnic Institute.&apos; The chemical valences are included for comparison. It can be seen that a solute whose metallic valence is lower than that of the solvent tends to stabilize the a phase while one whose metallic valence is higher than that of the solvent tends to stabilize the 0 phase. It should be noted that, inasmuch as the Pauling valences are periodic with atomic number, this is tantamount to saying that the elements in groups I-A, 11-A, III-A, III-B, IV-B, V-B, and VI-B are a stabilizers while those in groups IV-A, V-A, VI-A, VII-A, VIII-A, I-B, and 11-B are ß stabilizers. The chemical valences do not show such consistency. Although the zirconium-rich end of the Zr-Au diagram is not available, it call be expected that gold, having a metallic valence of 5.56, would stabilize the ß phase. At absolute zero, the Fermi energy level is the criterion of equilibrium, i.e., the structure having the lower Fermi level will be more stable. Conse- quently, allotropic transformation occurs in a metal when thermal excitation raises the Fermi level to a point at which the atoms can be better accomodated by a different structure which yields a lower Fermi level.4-6 Thus in allotropic transformation, a change in structure occurs as a result of the change in the energies of the bonding electrons. Since the Pauling valence is the number of bonding electrons per atom, and these are the only electrons whose energies are affected by thermal excitation,* it can be inferred that the introduction of a solute which has a higher Pauling valence than that of the solvent raises the initial Fermi level; consequently, the transformation temperature is lowered. The converse is also true. The fact that at the transformation temperatures this statement is still fairly valid implies that the contribution due to the difference in specific heat terms of the two allotropes is comparatively small.

Jan 1, 1962

This issue presents the first of several articles making up the Bump Symposium, which was held at the 1958 Annual Meeting of AIME. Other Symposium papers will appear in the September issue of Mining Engineering. THE term mountain bump describes the sudden rupture of one or more coal pillars under excessive stress. These bursts occur with varying degrees of violence and sometimes include adjacent strata, especially the bottom rock. Many failures do not develop enough violence to be dangerous and are regarded as an aid to coal production, but severe occurrences are accompanied by tons of flying coal, dense clouds of dust, and excessive gas emission. Such bursts sometimes throw heavy machinery several feet. Major factors to be considered in the problem are the nature of the strata above and below the seam and the depth of cover. Bumps are classified as to their nature, extent of damage, and point of occurrence, e. g., face bump, coal bump, high side bump, low side pavement bump, and district bump. The problem is extremely complex, and it cannot be over-emphasized that preventive measures, if they are to be successful, must be based on a thorough study of conditions in the individual mine. In western Canada, for example, the McGillivray mine, operating in a 9-ft seam at 2000 ft, has experienced severe bumps, but there have been no occurrences in the International mine, which operates in the same coal seam at 2400 ft, where the coal averages 17 ft thick. Differences in conditions governing the operation of these two mines are described in one of the following articles (see page 883). Again, most bumps in coal mines take place along pillar extraction lines, but at the Sunnyside mine in Utah they also occur a long way from active workings and sometimes in virgin territory. It is usual, too, for such failures to occur under fairly deep cover. But at Sunnyside, to cite only one instance, there have been disturbances along the main fault zone under less than 500 ft of cover. All too often conditions favorable to bumps are revealed only by actual mining—at Springhill No. 2 mine, drilling in roof and pavement strata disclosed a 60-ft sandstone bed after operations had started— and where extraction has advanced too far for preventive measures to be incorporated in the mining plan, districts have had to be abandoned. But in an era when premium ores are being rapidly depleted in the face of rising demands, abandonment is not easily justified. There must be systematic planning to eliminate coal mine bumps, insofar as this is possible. As in the Gary district of West Virginia (see page 888) much has been accomplished by planned operations based on known factors in bump control. But even this is not enough. Precise instrumentation is needed to indicate where bumps are likely to occur, and in both the U. S. and Canada stress analysis studies are being carried out with this object in view. These pages reveal the progress being made.

Jan 1, 1959

By William R. Patterson

ACCORDING to the phase diagram for the Mn-Ni system,&apos; the high-temperature, fcc y-manganese solid solution is stabilized to below room temperature, in the range approximately 22 to 28 wt pct Ni. However, pearson2 cites evidence in the literature showing that for manganese contents greater than about 75 wt pct the quenched phase in Mn-Ni alloys is fct. This is in keeping with zener&apos;s3 suggestion that in manganese-rich alloys the fcc high-temperature phase undergoes a diffusionless or martensitic transformation to a fct structure upon quenching. Work by Basinski and christian4 on manganese-rich compositions in the similar alloy system Mn-Cu established that in alloys of greater than about 82 wt pct Mn the y-manganese phase underwent a fee fct martensitic transformation upon quenching to room temperature. Striking evidence for this martensitic transformation was the highly twinned or banded microstructure, an example of which is shown in Fig. 1. Similar microstructures have also been found in quenched Mn-Cr5 and Mn-Au6 alloys. In the present investigation, we attempted to obtain similar evidence of a fcc — fct martensitic transformation in manganese-rich Mn-Ni alloys. Manganese alloys in the range 10 to 30 wt pct Ni were prepared by arc-melting, under argon, at atmospheric pressure. The alloys all were 50 g in size, and negligible weight loss occurred during melting. The starting materials were electrolytic manganese and nickel, both of 99.9+ pct purity. The alloys were subsequently homogenized 48 hr at 1750°F, hot-rolled 50 pct at 1700°F, annealed 2 hr at 1700°F, and water-quenched to room temperature. All heat treatment was done in purified argon. Both X-ray and metallographic techniques were used to examine the structures of the quenched alloys. X-ray diffractometer studies were conducted on powder specimens obtained from filings rean-nealed 2 hr at 1700°F in argon and water-quenched. Identification of the intensity peaks from the diffractometer counter traces showed that below about 10 to 12 pct Ni the y phase decomposed partially upon quenching to give an a- + ?-manganese structure. In the range approximately 12 to 25 pct Ni, the structure was found to be fct ? manganese with a c/a ratio approaching 1.0 at 25 pct Ni. Beyond approximately 25 pct Ni, the structure remained fcc. These results, including lattice-parameter determinations, are given in Table I. Metallographic examination. was carried out on specimens polished and etched after quenching, and also on polished specimens reannealed and quenched. In the first case, the distinctive twinning or banding so prevalent in Mn-Cu alloys was sought, while in the second, the surface relief effect generally regarded as being truly characteristic of a martensitic transformation was sought. The microstructure of representative alloys in the range 12 to 25 pct Ni is shown in Fig. 2. The structure of the Mn-15 pct Ni

Jan 1, 1965