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By N. S. Stoloff, R. G. Davis

It is concluded from an X-ray stztdy that the formation of the hcp Mg3Cd superlattice is a nuclea-tion and growth reaction. A two-phase, ordered-plus-disordered, region is observed between 153" nnd 141"C. A maximum in the flow stress is observed both at temperature and in quenched specimens within the two-phase region. The peak arises fro112 the extra energy required to create antiphase boundary upon cutting the ordered regions. Hardening during isothermal annealing in Mg3Cd has been shown to be similar to the domain hardening in Cu3Au-type alloys in that up to the maximum the structure is ordered domains growing into a short range ordered matrix. The hardening is due to a combination of short range order strengthening and the strengthening produced when antiphase boundary has to be created. In a recent study1 of the effect of long-range order upon the mechanical properties and deformation modes of hcp Mg3Cd a comparison was made be- tween quenched (disordered) and slow-cooled (fully ordered) specimens. The most striking observations were that the disordered alloy yields at a much higher stress than the ordered alloy, and that there is a change in slip mode from primarily (_0001) ba_sal slip in the disordered state to (0001), {1010}, {1122}, and {l011} slip in the ordered state. The main purpose of the present work is to extend these observations to determine whether MgsCd exhibits a peak in flow stress at an intermediate degree of order, or at a critical domain size, as do other orderedstems. However, disagreement exists about the Mg3Cd order transformation with respect to: 1) the location of the critical temperature for order, 165°C or 153"~,' and 2) how the degree of order varies with temperature. Welber et a1.5 concluded from specific heat measurements that the formation of Mg3Cd is a second-order reaction with the degree of order a continuous function of temperature, while Moore and Raynor concluded that it is neither a first-order reaction, with the degree of order a discontinuous function of temperature, nor a second-order reaction. Consequently it was considered necessary to undertake an X-ray investigation into the change in degree of order and structure in the

Jan 1, 1964

By M. C. Fuerstenau, A. M. Gaudin

Understanding the sedimentation of relatively thick suspensions depends on a knowledge of the concentration of the solids at various positions in the pulp and the times required for thickening. Flocculated kaolin slurries were studied with the transviewer, a device utilizing X-ray absorption in conjunction with a scanning mechanism. A mathematical model based on the Schuhmann size distribution in conjunction with Poiseuille's law yields experimental filtration rates as a hction of pulp density. These calculations show accord with the experimental results. Accurate predictions of sedimentation results depend upon determining the number and size of pores for given conditions, since the voidage of the suspension controls the volume of liquor that can pass through an element of suspension per unit time. A study on the sedimentation of flocculated kaolin slurries has indicated that their sedimentation takes place by two different processes, dependent on the initial concentration of solids in suspension. One process occurs in dilute suspensions (less than about 2 pct solids by volume) in which a multitude of relatively small flocs settle by hindered settling. In this case, maximal settling velocity is independent of container geometry.1 r2 The other process occurs in relatively concentrated suspensions (greater than about 2 pct solids by volume) in which the mass is considered to be settling as an aggregate network or as one large floc, defined as to size by the dimensions of the container. In this case, container geometry affects sedimentation results significantly. Furthermore, it seems that this single floc is in a state of compression from the beginning of settling, and that two phases of compression settling exist during sedimentation. The first occurs during the early stage of settling where liquid exudes easily and rapidly from the floc, while the second occurs in the compacting portion of the floc where water escapes more slowly and with much more difficulty. Sedimentation of relatively thick suspensions may then be thought to be a filtration phenomenon in which a pulp thickens by the filtration of its contained liquor through the aggregate network of pulp above it. This postulate has also been advanced by others.,4 To understand the sedimentation of relatively thick suspensions more fully, it was felt that knowledge of the concentration of solids at all positions in the

Jan 1, 1962

By Sheldon Rideout, E. L. Kamen, B. S. Lement, Paul A. Beck, W. D. Manly

The 1200°C isothermal sections of the following ternary phase diagrams were investigated: Cr-Co-Nil Cr-Co-Fe, Cr-Co-Mot and Cr-Ni-Mo. In all these systems the u phase was found to form extended solid solutions. Two new ternary phases of unknown structure were identified. The existence range of intermediate phases of transition elements was correlated with 3d electron vacancy concentrations. THE occurrence of extensive ternary d solid solutions in the Cr-Co-Ni and in the Cr-Co-Fe systems was described in a brief note.' More recently d- solid solutions were also found in the Cr-Fe-Mo system by two independent groups of investigators.2,3 The existence of binary d phases in the V-Co and V-Ni systems, predicted in ref. 1, was experimentally discovered recently by Duwez and Baen and independently by W. B. Pearson, J. W. Christian, and W. Hume-Rothery.5 Duwez and Baen stated two general conditions for the occurrence of the d phase in alloys of the transition elements: "(1) The atomic diameters of the two metals do not differ by more than 8 per cent. (2) One of the two metals has a body-centered cubic structure while the other is face-centered cubic, at least in one of its allotropic forms." In the course of an extensive research program conducted at this Laboratory under the sponsorship of the NACA, several ternary systems, containing d solid solutions and also certain new ternary phases, were investigated. The present report describes the investigated portions of the 1200°C isothermal sections of the following ternary phase diagrams: Cr- Co-Ni, Cr-Co-Fe, Cr-Co-Mo, and Cr-Ni-Mo. It was found that the range of existence of the d phase in these four ternary systems, as well as in one of two ternary systems which were investigated by others, can be fairly consistently described in terms of electron vacancy concentrations. This supports the suggestion of Sully and Heal" that the d phase is an electron compound. Experimental Procedure The ternary alloys were prepared by vacuum induction melting in zirconia and alumina crucibles. Lot analyses of the metals used are given in Table I. Specimens of all alloys were annealed at 1200°C in an atmosphere of purified 92 pct helium and 8 pct hydrogen mixture. Alloys consisting mainly of

Jan 1, 1952

By Goro Shimaoka, Kichizo Niwa

IN the past, the crystalline states of graphite in cast iron have been studied by many investigators. Recently several authors 1-4 have published interesting information on the crystal texture of the individual graphite grain, especially spherulites in nodular cast iron. In regard to the crystal structure of graphite, Lipson and Stokes0 howed by powder X-ray analysis that most of the crystals contain about 14 pct rhombohedra1 structure (ß-form) which differs from the hexagonal structure (a-form) in the sequence of layer stacking. Hoerni6 onfirmed the existence of the ß-form in a single crystal with electron diffraction by Kossel-Moellenstedt's method. Furthermore, Hoerni and Weigle7 found extra reflections in electron diffraction patterns, which are given by a unit cell twice as large as the usual one in the basal plane. Recently, Lukeshs observed graphite twinning and satellite reflections in his X-ray work and considered them as evidence for the existence of an orthorhombic superstructure. Owen and Street" and Matuyama" studied the structures of graphite crystals in several types of cast iron, using the X-ray powder method, and they showed that the graphite crystal contains a certain amount of the ß-form, an amount which varies with the sources of the cast iron used. The present study was made in order to secure structural information on graphitization in cast iron. Electron diffraction studies on the structure of single graphite flakes segregated from molten carbon or silicon-rich iron at 1200" to 1500°C are reported. Experimental Honkeiko pig iron (4.05 pct C, 1.59 pct Si, and 0.65 pct Mn) was used as the solvent of carbon or silicon. The pig iron was melted in an open furnace and a small quantity of metallic silicon was added to the melt at 1300°C. The melt was heated to 150O°C, and then retort black carbon or metallic silicon was added little by little. The components added to the bath contained approximately 5.0 pct C and 2.0 pct Si in the carbon-rich material, and 3.8 pct C and 5.4 pct Si in the silicon-rich iron. These two types were held at 1500°C and then cooled without graphitizing by cutting the heat sup-

Jan 1, 1958

By W. Edeburn, H. R. Fife

An extended study of dustproofing Freeport-seam coal has emphasized several fundamental features in the successful treating of bituminous coals. The extent of the exposed surface area and its absorption propcrties for the dust-retaining film were found to be the most critical factors affecting the efficiency of fly-dust prevention. From recently published screen data and specific surface-area measurements on United Kingdom coals, an approximation of the surface exposed by mine-run coal and by 1-in. slack was made. The total surface area exposed by an average tori of this mine-run coal was estimated at 3768 sq. yd., while a ton of 1-in. slack represents a total surface area of 8779 sq. yd. with no additions for porosity. It is important in coal treating to consider that in mine-run coal the fraction above 1/4 in. in size represents 79.5 per cent of the total weight, but only 4 per cent of the total surface, while the fraction below 150 mesh contains 47 per cent of the total surface and only 1.2 per cent of the total weight. Also, one should appreciate that, in a 1-in. slack, the domestic stoker fraction (1 in. to 8 mesh) contains 76.3 per cent of the weight and 8.2 per cent of the surface, while the fraction below 150 mesh represents 3.3 per cent by weight and 54.8 per cent by surface area. Wax extraction data on 1-in. to 0 slack from mine-run treated Freeport-searn coal showed that the coating was distributed uniformly as a function of exposed surface; hence, nonuniformly on a weight basis. This distribution of the coating on mine-run coal therefore limits the extent of treating that is desirable on bituminous coal at this point in the preparation. The treatment of Freeport mine-run coal before it reached the tipple gave a 70 to 80 per cent reduction of fly-dust in the tipple, a satisfactory treated commercial slack coal, and an indicated change in the trend of tipple degradation. The premium-treated domestic sizes required a supplemental treatment for complete dustproofness. The actual cost of the pretipple and supplemental treatments was very low per ton of coal treated, while the net or true cost was sufficiently

Jan 1, 1938

By R. B. Russell

The expansion coefficients of hexagonal (a) zirconium have been calculated from the lattice expansionparameters of both coefficientsofhexagonallow and high hafnium alloys in the range 0° to 600°C. It is found parametersofboththat the coefficients are straight-line functions of the temperature and that the effect of hafnium is to depress the mean coefficients by about 1 pct at room thattemperature and 9 pct at 600°C. The cubic (ß) form was stabilized so that its coefficient could be determined from 400' to 900°C. COEFFICIENTS of thermal expansion for hexagonal-close-packed (a) zirconium were determined up to 600°C (1112°F), without any interference from the effects of preferred orientation, by measurement of the lattice parameters obtained from a symmetrical back-reflection focusing X-ray camera. This paper combines the results for a 1.2 atomic pct hafnium alloy from an earlier report' with those for hafnium-free zirconium. The problem confronting the investigator is essentially that of getting sharp, high-angle diffraction lines which represent the material at a known constanl. temperature and chemical composition. In order to do this, it was necessary to use the proper X-ray emission wave length (Co K was chosen) and to have a fine-grained metal whose atomic spacings would be free from effects of cold work (the specimen was annealed) and to prevent a changing composition owing to gas absorption during the heating of the metal to temperature (the sample was heated in a vacuum). A summary of the effect of temperature on properties is listed in Table I which gives data for ordinary zirconium, as well as new values for the low hafnium metal. The coefficients of the linear thermal expansion that have been reported are given in Table 11. The discrepancies shown may be explained perhaps by the effect of preferred orientation, and McGeary and Lustman2 have done this successfully for sheet metal. The differences in texture cannot explain all the differences in expansion coefficient shown in Table II. liesults by the author agree most closely with those of Kroll.3 Chemical analysis of the high hafnium metal pre- viously reported1 showed that it was 98.22 atomic pct (97.40 wt pct) pure. The low hafnium metal was dehydrogenated Westinghouse crystal bar, designated SMZ-137A. Its analysis was as given in Table 111 (chemical analyses 5377, 5431, and 5432).

Jan 1, 1955

By W. Edeburn, H. R. Fife

An extended study of dustproofing Freeport-seam coal has emphasized several fundamental features in the successful treating of bituminous coals. The extent of the exposed surface area and its absorption propcrties for the dust-retaining film were found to be the most critical factors affecting the efficiency of fly-dust prevention. From recently published screen data and specific surface-area measurements on United Kingdom coals, an approximation of the surface exposed by mine-run coal and by 1-in. slack was made. The total surface area exposed by an average tori of this mine-run coal was estimated at 3768 sq. yd., while a ton of 1-in. slack represents a total surface area of 8779 sq. yd. with no additions for porosity. It is important in coal treating to consider that in mine-run coal the fraction above 1/4 in. in size represents 79.5 per cent of the total weight, but only 4 per cent of the total surface, while the fraction below 150 mesh contains 47 per cent of the total surface and only 1.2 per cent of the total weight. Also, one should appreciate that, in a 1-in. slack, the domestic stoker fraction (1 in. to 8 mesh) contains 76.3 per cent of the weight and 8.2 per cent of the surface, while the fraction below 150 mesh represents 3.3 per cent by weight and 54.8 per cent by surface area. Wax extraction data on 1-in. to 0 slack from mine-run treated Freeport-searn coal showed that the coating was distributed uniformly as a function of exposed surface; hence, nonuniformly on a weight basis. This distribution of the coating on mine-run coal therefore limits the extent of treating that is desirable on bituminous coal at this point in the preparation. The treatment of Freeport mine-run coal before it reached the tipple gave a 70 to 80 per cent reduction of fly-dust in the tipple, a satisfactory treated commercial slack coal, and an indicated change in the trend of tipple degradation. The premium-treated domestic sizes required a supplemental treatment for complete dustproofness. The actual cost of the pretipple and supplemental treatments was very low per ton of coal treated, while the net or true cost was sufficiently

Jan 1, 1938

By W. A. Ver Wiebe

The year 1938, with a production of 58,784,250 bbl. from 18,790 wells shows a slight recession from the high peak of oil production reached the previous year, when slightly over 68 million barrels of oil was marketed. The previous high peak had been reached in 1917 with a total of 45,451,000 bbl. Another still earlier peak was reached in 1904, during which year slightly less than 5 million barrels was produced and sold. The production of gas, on the other hand, probably reached a new peak during 1938 with a total of over 60 billion cubic feet. This peak, however, was not the highest peak, for during the year 1908 over 80 billion cubic feet was produced. Between these two high peaks the production dropped down to 16 billion cubic feet in the year 1921. The number of wells drilled during the year totals 1569. This figure is somewhat lower than the figure given in several trade journals because it does not include wells that were deepened or recompleted in a different geological horizon. Nearly three-fourths (or 1107) of the total number of wells were completed as commercial oil wells (915 in western and 192 wells in eastern Kansas). The commercial gas wells completed number 50, of which 4 are in eastern Kansas and 46 in western Kansas. The remaining 412 completions include 130 dry holes in eastern and 282 dry holes in western Kansas. Based on daily potential capacity, the new discoveries of the year accounted for 70,000 bbl. of new oil for eastern and 1,220,000 bbl. of new oil for western Kansas. It is interesting to note in this connection that the number of wells completed in the state rose gradualIy to a first peak in 1904, when 2782 were drilled. The number dropped off rapidly to 368 three years later, but rose to the second and highest peak in 1918 when 4671 wells were completed. In the period between 1904 and 1912 more gas wells than oil wells were completed. Between the high peak of 1918 and the somewhat lower peak in 1937, the low point was reached during 1931, with the completion of only 470 wells. In the matter of new pools discovered, Kansas again ranks high. The exact number depends somewhat upon the interpretation of a new area whether it should be called a new pool or a long extension of an

Jan 1, 1939

By George H. Ashley

The present critical state of the supply, distribution, and utilization of coal and the necessity for pooling and zoning coals calls renewed attention to the lack of any fully adequate classification of coal. In the past coals have been classified as anthracite, semianthracite, semibitumi-nous, bituminous, subbituminous coals, and lignite, and a few special types, such as splint coal and cannel coal. But under the term bituminous coal are included a great variety of coals differing markedly both physically and chemically. The term subbituminous coal covers as great a range of chemical differences. In order to distinguish these varieties of bituminous coals it has been customary to designate coal by names derived from the place where mined, or by the name of the bed from which it is mined. Thus, in the market reports, coals are quoted as Pocahontas coal, New River or Sewell coal, Moshannon coal, Ohio coal, Williamson County coal, Jellico coal, and so on indefinitely, no limit being set as to the boundaries of the area to which a given name is applied. Nor is there any scale by which the coal from one place may be compared with the coal from some other district or some other bed. On the one hand, coals from the same district may be quite distinct and sell at very different prices or coal from the same bed may differ greatly in different districts; on the other hand, coals from different states may be so similar physically and chemically that one could replace the other in practical use without any appreciable difference in service. The following classification, arrived at after a careful review of a large number of systems of classification and of all of the recognized characteristics of coal, brings together all coals that so nearly resemble each other physically, chemically, and in heating qualities that any coal of a given type could replace any other coal of the same type and grade in use. Thus, if coals A and B are classed as of the same type and grade they have, so far as known to the writer, approximately the same heating value when burned under the same conditions, and the same character, length of flame, and properties affecting transportation and stocking; and if of the same grade, approximately the same percentage of impurities.

Jan 1, 1920

By W. A. Ver Wiebe

The year 1938, with a production of 58,784,250 bbl. from 18,790 wells shows a slight recession from the high peak of oil production reached the previous year, when slightly over 68 million barrels of oil was marketed. The previous high peak had been reached in 1917 with a total of 45,451,000 bbl. Another still earlier peak was reached in 1904, during which year slightly less than 5 million barrels was produced and sold. The production of gas, on the other hand, probably reached a new peak during 1938 with a total of over 60 billion cubic feet. This peak, however, was not the highest peak, for during the year 1908 over 80 billion cubic feet was produced. Between these two high peaks the production dropped down to 16 billion cubic feet in the year 1921. The number of wells drilled during the year totals 1569. This figure is somewhat lower than the figure given in several trade journals because it does not include wells that were deepened or recompleted in a different geological horizon. Nearly three-fourths (or 1107) of the total number of wells were completed as commercial oil wells (915 in western and 192 wells in eastern Kansas). The commercial gas wells completed number 50, of which 4 are in eastern Kansas and 46 in western Kansas. The remaining 412 completions include 130 dry holes in eastern and 282 dry holes in western Kansas. Based on daily potential capacity, the new discoveries of the year accounted for 70,000 bbl. of new oil for eastern and 1,220,000 bbl. of new oil for western Kansas. It is interesting to note in this connection that the number of wells completed in the state rose gradualIy to a first peak in 1904, when 2782 were drilled. The number dropped off rapidly to 368 three years later, but rose to the second and highest peak in 1918 when 4671 wells were completed. In the period between 1904 and 1912 more gas wells than oil wells were completed. Between the high peak of 1918 and the somewhat lower peak in 1937, the low point was reached during 1931, with the completion of only 470 wells. In the matter of new pools discovered, Kansas again ranks high. The exact number depends somewhat upon the interpretation of a new area whether it should be called a new pool or a long extension of an

Jan 1, 1939

By J. W. Pamplin

SOME 40 miles east of Tampa is the center of the Florida pebble phosphate deposits. These are of Pliocene age and consist of several members of the Bone Valley formation.1 Physically the phosphate-bearing formation, locally called the "matrix," varies in thickness from nothing to about 25 ft., usually averages 10 ft., and consists mainly of clay, quartz and phosphate pebble, the latter particles varying in size from colloidal to one inch diameter. The pebbles range in color from dark gray, through white, to cream, and in hardness from that which must be broken with a hammer to that which can be scratched with the fingernail. They assay from 66 to 80 per cent bone phosphate of lime (called "B.P.L." in the trade) or tricalcium phosphate (Ca3P20s) and are secondary apatites. They form from 15 to 50 per cent by weight of the matrix, Over the matrix lies a varying thickness (5 to 40 ft.) of overburden composed of quartz and clay. Briefly, mining consists of two operations2 in open pits about 200 ft. wide by ½ mile or more in length. In the first step overburden is removed by large electric draglines at the rate of about 700 cu. yd. per hour. This is followed closely by hydraulic mining of the matrix at the rate of about 300 cu. yd. per hour. This matrix yardage is moved from an improvised sump in the floor of the pit to an ore-dressing plant, some-times a mile distant, by one, two or three "pit-cars" (pumping units) working on a 12-in. pipe line called the "rock line" to distinguish it from the high-pressure water line feeding the hydraulic giants, which is known as the "hydraulic line." This 700 yd. of overburden and 300 yd. of matrix-1000 yd. in all-amounts to about 1500 tons of material moved each hour. The over-burden is dumped into the mined-out pit alongside the pit being mined. The matrix moves to the ore-dressing plant at the rate of about 7 ½ long tons in 4000 gal. of water per minute-a ratio of approximately one to two by weight, or one to six by volume. This constitutes the "mill heads," but in the pebble district it is called the "matrix."

Jan 1, 1938

By A. H. Shoemaker

THE shutdown of Homestake by Government order L-208, with its consequent disruption of a very stable and trained working force, coupled with postwar inflation and the coincidence that a mining depth had been reached that posed problems of ventilation, access to exploration areas, and choice of mining methods that would be applicable to zones of greater rock pressures made a very searching analysis of every phase of Homestake's operations a necessity. Any changes to be made had not only to meet the problems of deeper mining but also had to provide greater efficiency so that the mine might operate at a substantial profit until such time as a gold price adjustment might be forthcoming that would offset post-1945 inflation. Geology and Mining Situation The Homestake mine lies in the northern Black Hills in an area of Pre-Cambrian rocks exposed by the erosion of the paleozoic formations which covered the Black Hills. The Pre-Cambrian rocks in the vicinity of Lead comprise metamorphosed sediments with a total thickness of about 20,000 ft. The oldest formation, the Poorman, is ankeritic carbonate schist. The next oldest, the Homestake formation, host rock for all Homestake orebodies, is a siliceous iron-magnesium carbonate schist. The younger formations are dom-inantly argillaceous with some quartzites. Tertiary intrusive rocks cut all formations. The Pre-Cambrian rocks have undergone extreme isoclinal folding. Superimposed on this intricate folding are zones of shear folding which cross the isoclinal folds at small angles. The Homestake orebodies are pipelike replacements of the Pre-Cambrian Homestake formation where certain cross folds intersect some earlier isoclinal folds. These orebodies plunge flatly to the southeast at variable angles locally as steep as 45". The orebodies are replacement areas where numerous vein quartz of irregular shape have formed with surrounding zones of chlorite alterations containing disseminated sulfides and metallic gold. Where the numerous individual quartz veins with the sulfide and gold-bearing alteration zones are close together, large irregular orebodies with a roughly elliptical plan outline result. These ore zones may be more than 200 ft wide and 700 ft long in plan area. They have followed down the plunge of certain severely folded structures with great persistence. Two vertical operating shafts, the Ross and Yates, serve the mine, one with rope capacity to reach the 4850 level, the other to the 5000 level.

Jan 1, 1959

By Wilber Stout

In Ohio, the annual output of coke made from native coals has averaged not more than 70,000 tons, or about enough to run a 200-ton blast furnace. Raw coal locally mined from the Sharon, or No. 1, bed was used for iron smelting in Mahoning furnace at Lowellville, Mahoning Co., as early as 1846. This practice was continued in the Youngstown district until the coal became scarce and the Connellsville coke more popular. At present, the Sharon bed contributes a part of the fuel for the production of ferrosilicon iron at Jackson, Jackson CO. About one-third native coal and two-thirds soft coal are used. In this state, coke, on a commercial basis, was first made in Jefferson County probably about 1861 or 1862. The coals used were the Steuben-ville Shaft, or Lower Freeport, and the Strip Vein or Middle Kittanning. The practice, however, was discontinued before 1880 because of the competition of superior foreign cokes. Beehive ovens, later built at Leetonia, Columbiana Co., were operated for only a few years; the coal used at this place is the Lower Kittanning or No. 5. In a desultory way, slack from the Pittsburgh coal has been coked at a few places in eastern Ohio, and attempts, either for experimental or for commercial purposes, have been made in other parts of the state. Small quantities of coke were made from the Upper Freeport coal at Salineville, Columbiana Co., and near Nelsonville, Hocking Co.; the results were poor. Tests were made of the Middle Kittanning coal near Zanesville, Muskingum Co., at Moxahala Furnace, Perry Co., and at Washington Furnace, Lawrence Co.; the cokes were all high in sulfur and ash. Attempts were made to coke the Clarion coal at Vinton Furnace, Vinton Co.; a small battery of molding ovens and a pile of high-sulfur coke yet remain to tell the story. The Pittsburgh coal was coked on a commercial scale at Utley and at Lathrop, Athens Co., but the operations were not successful and were soon abandoned. These failures and indifferent successes are not to be attributed to a lack of demand for a first-class coke, as Ohio has held a commanding place for many years in iron smelting; nor to a deficiency of coals, as the state has a vast reserve of such material. They are to be ascribed to the inferior quality of the native products offered to the trade. The cokes

Jan 1, 1920

By L. G. Austin, P. T. Luckie, R. R. Klimpel, R. S. C. Rogers

1. INTRODUCTION The Bond method(1.2) for sizing tumbling ball mills has been used successfully for many years. The primary purpose of the Bond calculation is to predict the mill size and mill power to give a desired capacity (Q tph) from a wet overflow ball mill in normal closed circuit operated with a circulation ratio of 2.5. The input to the calculation is the make-up feed size characterized by the 80%-passing size in micrometers (xG), the desired circuit product size characterized by the 80%-passing size (xQ), and an empirical grindability number (the standard Bond Work Index) determined by a standard test. A series of empirical correcting factors(2) are used to convert the results to open-circuit or dry grinding in grate discharge mills. The Bond method has two major engineering advantages: (i) it is very simple; (ii) experience has shown that it works for many circumstances, as a reasonable approximation, because it is based on direct conversion of test data to results measured on industrial mills. There are four main disadvantages of the Bond method. First, there will be a range of error for any specific mill and material and set of operating conditions because the method does not explicitly include several variables which are obviously important: (i) recycle ratio and classifier efficiency (ii) mixture of ball sizes in the mill (iii) variations of residence time distributions with mill geometry and slurry density (iv) lifter design (v) slurry rheology (vi) different underfilling or overfilling of the mill as flow rate is changed. Second, the Bond method explicitly assumes that specific grinding energy E is not a function of ball load, whereas industrial practice and laboratory tests(3) show that the specific grinding energy (to go from a specified feed to a specified product) is less for lower ball loadings than the ball loading for maximum mill capacity. Third, the method uses only the 80% passing size of circuit feed and product to characterize the size distributions, whereas mill capacity in general must depend on the shape of the feed size distribution and the product size distribution. The prime example of this is the use of the reverse closed circuit which removes some fraction of the make-up feed before it is

Jan 1, 1982

By Gerald Edmunds

The liquidus line on the phase diagram for temperature versus composition of a binary alloy system, representing the boundary between the homogeneous melt and the heterogeneous melt plus solid, besides showing the minimum casting temperature, is useful in determining eutectic compositions and the presence of phase changes such as peritectic transformations and intermetallic compound formation. The liquidus often is determined by the cooling curves of thermal analysis, but supercooling frequently occurs, so that the temperature values are low. An alternative method, the one employed here, consists of determining the composition of samples of the melts from heterogeneous alloys that are at equilibrium. With meticulous attention to fundamentals, this method is capable of yielding values limited in precision only by the temperature control and measurement and analyses. Apparatus By starting, on the one hand, with a supersaturated solution and allowing the excess solute to precipitate, and on the other hand with an undersaturated solution and allowing more of the solute to be dissolved, both processes being carried out at the same temperature, equilibrium may be said to have been approached from both directions; that is, from above and from below. If the analyses show the solutions to contain the same fraction of solute when equilibrium has been approached from above and from below, one is assured that equilibrium has been reached in both determinations. In order to carry out such determinations, it is necessary to have equipment for obtaining and maintaining the proper temperatures; for holding the melt, measuring its temperature, and stirring, sampling and analyzing it. The present work required temperatures from 420° to 900°C. The equipment consisted of: A furnace, which was a vertical alundum tube, 13/4-in. diameter inside and 18 in. long, wound with Nichrome resistance wire, surrounded by a 3-in. i.d. alundum tube wound for 5 in. of length near each end, for compensation of end losses. This muffle was contained in an iron shell with Transite end plates, the intervening space being packed with Sil-O-Cel. The outside dimensions of the furnace were 12 in. in diameter by 181/2 in. in height. Heating current was supplied by three independent variable-voltage transformers (Variac), one connected to each end compensator winding and manually controlled, and one connected to the main winding through a series resistance of 5 ohms. This resistance was short-circuited for

Jan 1, 1944

By W. H. Schacht

In the Lake Superior District, the air indoors must be heated continuously during eight months of the year and occasionally during the remaining months. Incident with mining in this district, therefor?, there is need for heating many of the buildings connected with these operations. In addition to the mine buildings, that is, shops, engine houses, offices, change houses, etc., such public buildings as schools, library, and theater, when close to the mines, are often supplied from the mine heating mains. At the Copper Range Company's mines, Champion, Trimountain and Baltic, the heating surface thus supplied from the mine mains is over 50,000 sq. ft. (4645 sq. m.) which requires a steam consumption, at times, of 18,000 Ib. (8165 kg.) per hour, or the equivalent of a rate of ovcr 50 tons of coal per day (were live steam used). This figure is based on a consumption of 1/3 Ib. per sq. ft. of heating surface during the coldest weather, and provided the system is not wasting steam by blowing it to the atmosphere or into the return line on account of leaky traps, which so often is the case. Under the latter conditions, steam consumptions of three to four times the above rate are not uncommon. This shows that the cost of heating is of enough importance to he given serious consideration, especially at this time of rising prices of fuel. The power and heating value of exhaust steam arc appreciated by most engineers, and its application for such purposes is general. At our stamp mills, the exhaust from the stamps is used to operate low-pressure turbines, thus reducing the former water rate per horsepower developed by more than 50 per cent. At the above-mentioned mines, electric motors have replaced the many small steam engines, so that this supply of exhaust steam has been practically eliminated. The larger engines are compound, triple, or quadruple condensing. The hoists, however, in all cases are simple and non-condensing and of two sizes, namely, 24 by 60 in. and 32 by 72 in. (61 by 152 cm. and 81 by 183 cm.). These hoists now offer the only available supply of exhaust steam; but as this flow is intermittent and varies from extreme violence to zero, the steam so discharged cannot be

Jan 1, 1922

By Gerald Edmunds

The liquidus line on the phase diagram for temperature versus composition of a binary alloy system, representing the boundary between the homogeneous melt and the heterogeneous melt plus solid, besides showing the minimum casting temperature, is useful in determining eutectic compositions and the presence of phase changes such as peritectic transformations and intermetallic compound formation. The liquidus often is determined by the cooling curves of thermal analysis, but supercooling frequently occurs, so that the temperature values are low. An alternative method, the one employed here, consists of determining the composition of samples of the melts from heterogeneous alloys that are at equilibrium. With meticulous attention to fundamentals, this method is capable of yielding values limited in precision only by the temperature control and measurement and analyses. Apparatus By starting, on the one hand, with a supersaturated solution and allowing the excess solute to precipitate, and on the other hand with an undersaturated solution and allowing more of the solute to be dissolved, both processes being carried out at the same temperature, equilibrium may be said to have been approached from both directions; that is, from above and from below. If the analyses show the solutions to contain the same fraction of solute when equilibrium has been approached from above and from below, one is assured that equilibrium has been reached in both determinations. In order to carry out such determinations, it is necessary to have equipment for obtaining and maintaining the proper temperatures; for holding the melt, measuring its temperature, and stirring, sampling and analyzing it. The present work required temperatures from 420° to 900°C. The equipment consisted of: A furnace, which was a vertical alundum tube, 13/4-in. diameter inside and 18 in. long, wound with Nichrome resistance wire, surrounded by a 3-in. i.d. alundum tube wound for 5 in. of length near each end, for compensation of end losses. This muffle was contained in an iron shell with Transite end plates, the intervening space being packed with Sil-O-Cel. The outside dimensions of the furnace were 12 in. in diameter by 181/2 in. in height. Heating current was supplied by three independent variable-voltage transformers (Variac), one connected to each end compensator winding and manually controlled, and one connected to the main winding through a series resistance of 5 ohms. This resistance was short-circuited for

Jan 1, 1944

By J. W. Pamplin

Some 40 miles east of Tampa is the center of the Florida pebble phosphate deposits. These are of Pliocene age and consist of several members of the Bone Valley formation.1 Physically the phosphate-bearing formation, locally called the "matrix," varies in thickness from nothing to about 25 ft., usually averages 10 ft., and consists mainly of clay, quartz and phosphate pebble, the latter particles varying in size from colloidal to one inch diameter. The pebbles range in color from dark gray, through white, to cream, and in hardness from that which must be broken with a hammer to that which can be scratched with the fingernail. They assay from 66 to 80 per cent bone phosphate of lime (called "B.P.L." in the trade) or tricalcium phosphate (Ca³P2O8) and are secondary apatites. They form from 15 to 50 per cent by weight of the matrix. Over the matrix lies a varying thickness (5 to 40 ft.) of overburden composed of quartz and clay. Briefly, mining consists of two operations2 in open pits about 200 ft. wide by 1/2 mile or more in length. In the first step overburden is removed by large electric draglines at the rate of about 700 cu. yd. per hour. This is followed closely by hydraulic mining of the matrix at the rate of about 300 cu. yd. per hour. This matrix yardage is moved from an improvised sump in the floor of the pit to an ore-dressing plant, sometimes a mile distant, by one, two or three "pit-cars" (pumping units) working on a 12-in. pipe line called the "rock line" to distinguish it from the high-pressure water line feeding the hydraulic giants, which is known as the "hydraulic line." This 700 yd. of overburden and 300 yd. of matrix—1000 yd. in all-amounts to about 1500 tons of material moved each hour. The overburden is dumped into the mined-out pit alongside the pit being mined. The matrix moves to the ore-dressing plant at the rate of about 7% long tons in 4000 gal. of water per minute—a ratio of approximately one to two by weight, or one to six by volume. This constitutes the "mill heads," but in the pebble district it is called the "matrix."

Jan 1, 1938

By Alexander R. Troiano, Eugene P. Klier

Since the very early work on quenched structures, where the products of the martensite transformation had been recognizedl this transformation has provoked much interest and study. Theoretically it was desirable to account for the extreme changes in physical properties resulting from the formation of martensite, as that information might lead to results of practical importance. Desirable information, therefore, was on the kinetics of transformation from austenite to martensite as well as on the physical constitution of the martensite. It has been known for years that certain steels quenched to room temperature will contain persistent austenite as well as martensite. Other important and now well-established features of the martensite reaction are the Progress of the reaction on cooling only and the independence of Ar" with cooling velocities exceeding the critical velocity. These facts have been experimentally determined by various methods and investigators. Notable among the early investigators were Tammann and Scheill and Wever and Engel.2 Unfor- tunately, all investigators did not fully interpret their results, which, coupled with several investigations that yielde. conflicting resultsl caused a state of confusion that was not clarified until quite recently. X-ray investigations of martensite in steels3-6 indicate it to be a supersaturated solid solution of carbon in alpha iron. This supersaturation is evident from the appearance of a body-centered tetragonal structure with the addition of sufficient carbon. The dimensions of this tetragonal structure are a linear function of the carbon content within the limits of accuracy of the determinations. Slight tempering of tetragonal martensite leads to the destructi,, of the tetragonal structure, which is converted to a body-centered cubic strutture. This phenomenon has precipitated a controversy concerning the nature and mechanism of the tempering of martensite The facts in the case have been outlined by Epstein7 and more recently by Antia, Fletcher, and Cohen.8 The significance of Ar" on theoretical grounds is not clear, however, although considerable study has been devoted to its determination. The precise position of Art' aS a function of carbon content was first stated by Greninger and Troiano9 for steels covering a range of approximately 0.7 to 1.8 per cent carbon. The effect of alloying elements on Ar" has recently been the subject matter of investigation by various methods.

Jan 1, 1945

By J. W. Pamplin

SOME 40 miles east of Tampa is the center of the Florida pebble phosphate deposits. These are of Pliocene age and consist of several members of the Bone Valley formation.' Physically the phosphate-bearing formation, locally called the “matrix," varies in thickness from nothing to about 25 ft., usually averages 10 ft., and consists mainly of clay, quartz and phosphate pebble, the latter particles varying in size from colloidal to one inch diameter. The pebbles range in color from dark gray, through white, to cream, and in hardness from that which must be broken with a hammer to that which can be scratched with the fingernail. They assay from 66 to 80 per cent bone phosphate of lime (called "B.P.L." in the trade) or tricalcium phosphate (Ca3P2O8) and are secondary apatites. They form from 15 to 50 per cent by weight of the matrix. Over the matrix lies a varying thickness (5 to 40 ft.) of overburden composed of quartz and clay. Briefly, mining consists of two operations2 in open pits about 200 ft. wide by ½ mile or more in length. In the first step overburden is removed by large electric draglines at the rate of about 700 cu. yd. per hour. This is followed closely by hydraulic mining of the matrix at the rate of about 300 cu. yd. per hour. This matrix yardage is moved from an improvised sump in the floor of the pit to an ore-dressing plant, some- times a mile distant, by one, two or three "pit-cars" (pumping units) working on a 12-in. pipe line called the "rock line" to distinguish it from the high-pressure water line feeding the hydraulic giants, which is known as the “hydraulic line." This 700 yd. of overburden and 300 yd. of matrix-1000 yd. in all- amounts to about 1500 tons of material moved each hour. The over- burden is dumped into the mined-out pit alongside the pit being mined. The matrix moves to the ore-dressing plant at the rate of about 7 ½ long tons in 4000 gal. of water per minute-a ratio of approximately one to two by weight, or one to six by volume. This constitutes the "mill heads," but in the pebble district it is called the "matrix."

Jan 1, 1938