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By W. F. Mullen

WITH few exceptions, unit operations in the Pennsylvania slate industry in 1950 did not differ appreciably from production methods described by Behre1 and Bowles 2-4 several decades ago. Many traditionally picturesque but relatively inefficient hand operations continued to contribute to high operating costs in an industry in which the margin of profit, for various reasons, was admittedly low. As part of a general program in which the Pennsylvania State College has been assisting the slate industry to solve some of its problems, time and method studies were used in an effort to determine the bottlenecks of production flow. The results are as applicable to other stone industries as they are to slate.

Jan 12, 1951

By F. M. Lewis, J. E. Goodman

A larger, slow-speed, under-loaded ball mill and hydraulic classifier have almost doubled grinding efficiency at the lsabella mill. TENNESSEE Copper Co. operates two ore con-A centrators, the London and Isabella mills near Copperhill, Tenn. In 1948 and 1949 the small ball mills and rake classifiers in the London concentrator were replaced by one large ball mill and one hydraulic classifier. This new ball mill was designed oversize so that it could be operated at slower than normal speed. The proper operating conditions were established and the results published.' Later it was found that this mill operated more efficiently with a small ball charge." While this London grinding practice was being developed, the Isabella grinding circuit was not changed in any way. It remained a conventional two-stage rod mill—ball mill combination, the rod mill in open circuit and the ball mill in closed circuit with a rake classifier. Study of the data indicated that grinding cost could be lowered by converting to the London practice, but not enough would have been saved to warrant the expense of converting. No plan for improving this grinding operation could be developed. In 1953 this study was reopened when plans were made to increase the Isabella mill output from 1150 to 1500 tpd. At this time the grinding circuit consisted of a 6x12 rod mill followed by a 6x12 ball mill in closed circuit with a 6-ft rake classifier. Another 6x12 ball mill and 6-ft rake classifier would have been sufficient equipment and would have been the simplest and cheapest installation. However, this would have offered no improvement in grinding efficiency or operating cost. If, on the other hand, the grinding operation could be converted to the London practice, by installation of one large 101/2x9x9 tricone mill and a 10-ft hydroscillator,2 lower operating costs would justify the additional investment. Economics: Table I presents estimates for the two schemes for enlarging the Isabella mill. In the first scheme, column 1, one 6x12 ball mill and one 6-ft rake classifier were to be added. In the second scheme, column 2, the existing small ball mill and rake classifier were to be retired and one large mill and hydroscillator were to be installed. Estimated savings from the difference in operating costs made an attractive return on the additional investment for the large mill and hydroscillator. Actual costs of carrying out this plan are tabulated in column 3b. It will be seen that these costs follow the estimates in column 3a very Closely. The return on the additional investment is calculated from the difference in the operating cost in column 1 and the actual operating cost in column 3b. This too come very close to the estimate. Power and Steel: Power requirements and steel consumption for the rod mills and ball mills, both actual and estimated, are presented in Table 11.

Jan 1, 1958

By G. W. Healy, N. R. Griffing

The activity coefficient of sulfur in Cr-Fe-S melts was determined by measuring the values of Ph3Rh,in equilibrium with such melts. The results showed that chromium has a pronounced negative effect on the activity coefficient of sulfur, which up to about 20 pct Cr may be represented by the equation: log f; = - 0.019 pct Cr It was also found that the influence of chromium was not altered by the presence of appreciable amounts of carbon or silicon. The influence of alloying elements on the activity of sulfur in molten iron has been the subject of many investigations; however the effect of one important alloying element, chromium, has not been reported, and the object of the present investigation was to determine its effect on the activity coefficient of sulfur in liquid Fe-Cr-S alloys both in the absence and in the presence of carbon and/or silicon. EXPERIMENTAL PROCEDURE The general method employed consisted of passing mixtures of hydrogen and hydrogen sulfide over the sulfur-containing melt of interest and analyzing the outgoing gas to determine the equilibrium value of which resulted from the reaction shown in Eq. 111. H, (gas) + S (dissolved in melt) = H,S (gas) 111 The activity coefficient of sulfur, fs, was then calculated with Eq. [2] in which K, is the known equilibrium constant of Eq. [I] for dilute solutions of sulfur in iron. Raw materials used in the preparation of the charges included commercial grades of electrolytic iron and chromium and carbon-reduced, acid-treated silicon of 99.9 pct purity. Oxygen in the former presented no problem since it was removed by hydrogen in the normal course of an experiment. Carbon was added in the form of premelted iron-carbon and chromium-carbon master alloys. Sulfur was charged as iron sulfide prepared by first heating powdered iron and sulfur in air in an alumina dish until reaction occurred, and then deoxidizing by melting in a hydrogen atmosphere. Commercially bottled hydrogen and hydrogen sulfide were used after being passed through purification systems containing palladium, "Drierite," and magnesium perchlorate in the case of hydrogen, and "Drierite" alone in the case of hydrogen sulfide. Lamp-grade cylinder argon served as a flushing agent without further purification. Charges weighing from 300 to 500 g were placed in a high-purity alumina crucible of 0250-ml capacity and heated in an argon atmosphere in the induction-heated carbon-tube furnace illustrated in Fig. 1. During heating, a dry hydrogen atmosphere was substituted for argon in order that deoxidation of the charge and flushing out of argon would be accomplished sooner. After the charge melted, a Pt-Pt 10 pct Rh thermocouple contained in an alumina protection tube was immersed in the melt, and the desired melt temperature (usually 1600°C) was established. Higher temperatures up to 1760°C were required for some chromium-rich alloys because of their higher melting points, and in these cases a Pt 6 pct Rh-Pt 30 pct Rh thermocouple was used. The thermocouple output was fed to an automatic controller which provided straight line temperature

Jan 1, 1961

By W. Rostoker, H. Nichols

It has been demonstrated in previous work1'2 that wetting of aluminum alloys by liquid mercury can cause fracture to occur with substantial suppression of prior plastic flow. This has been interpreted as the action of a critical liquid species in reducing the cohesive strength of a stressed solid at sites of potential crack nucleation. In this way the critical transverse stress for fracture nucleation is reached at much lower stresses than is normally the case. The stresses for both fracture nucleation and fracture propagation are depressed by the same mechanism. In so doing the plastic-energy component of fracture energy is reduced to a level which is of the same order of magnitude as the surface, interfacial, or cleavage energy. Recent work2 has illustrated the influence of dispersed precipitates, cold work, and combinations of these on brittle fracture associated with plastic strains of the microyield order of magnitude. This has been rationalized in terms of the contribution of internal microstress fields to the stress magnifications at points of obstruction of active slip bands in a stressed metal. The presently reported studies on an Al-4-1/2 pct Mg alloy amplify this subject by introducing thermal-mechanical conditions which can produce strain aging. As amply demonstrated by Phillips, Swain, and borall, the tensile behavior of aluminum alloys containing magnesium reveals a yield-point elongation and successive discontinuous elongations over the whole plastic-strain range. This gives a stepped or serrated character to the stress-strain diagram. The yield-point elongation is not temperature-dependent. On the other hand, the discontinuous extensions in the plastic-strain range are gradually suppressed by lower temperatures of testing. At -78"C, only the yield-point elongation persists. The yield-point elongation itself can be suppressed by rapid quenching to room temperature from an annealing temperature of 500°C. The argument presented by Phillips et 1. and Cottre114 is that the yield-point elongation derives from surmounting at a critical stress the restraint to slip by grain boundaries which have been reinforced by appreciable magnesium-atom segregation. The serrated character of the plastic-strain range is the result of rapid strain aging during the test. This is made possible by the inevitable proximity of magnesium atoms to any dislocation line. In the Al-4-1/2 pct Mg alloy there is one magnesium atom for every twenty-two aluminum atoms and, with a coordination number of 12, a magnesium atom is on the average only about two atomic distances from any given lattice site. Rapid strain aging is therefore a reasonable expectation. A study of mercury embrittlement of the Al-4-1/2 pct Mg alloy (commercial designation 5083) provides an opportunity to relate the interplay of grain size, grain boundary restraint to slip and strain aging in the brittle-fracture process. One lot of commercial sheet material of 0.125-in. thickness was used for all of the tests. The specimen shape and test procedures used were the same as those described in a previous publication.2 A range of grain sizes between 0.0057 and 0.0125 mm was produced by various combinations of plastic prestrain and annealing. The coarsest grain was somewhat elongated in shape. In this case the measurement was taken in the direction transverse to the axis of tension as more meaningful to a brittle-fracture process. In the annealed condition, specimens wetted with mercury failed with zero permanent elongation at stresses slightly below the normal yield point, i.e., stresses at 0.05 to 0.2 pct strain. Since this occurs before yield-point elongation can begin, fracture derives from slip contained within individual grains and restrained from propagating across grain boundaries. No significant difference in wetted fracture stress was observed between specimens which had been water-quenched or furnace-cooled from the annealing temperatures. This signifies that the degree of magnesium segregation at grain boundaries

Jan 1, 1964

By Byron W. Cheever

At the meeting of the Institute held in St. Louis, in October, 1886 (Transactions, xv., 448), I presented a paper upon the above subject. From the well-known action of certain solvents on phosphide and phosphate of iron, the conclusion was then reached, founded on analyses, that phosphide and phosphate of iron must be present in all iron. But this conclusion was based upon the reactions obtained in the analyses of iron phosphide and phosphate, in which the phosphorus existed in conditions different from those found in commercial iron. In the former, the phosphorus is concentrated ; in the latter, diffused. This fact left a reasonable ground for doubting the existence of phosphoric acid in commercial irons. Some direct method was therefore sought which would prove its presence. After investigating the subject for some time, I came to

Jan 1, 1888

By M. Karfakis, K. Kim, R. V. de la Cruz

The in situ deformability of a closely jointed basalt rock mass was determined by two different methods: the NX-borehole jack method where displacements of opposing curved platens were related to applied hydraulic pressures, and the modified Goodman jack method where tangential strains on the borehole walls were related to induced tangential stresses. The modulus obtained by the modified Goodman jack method were much higher than those obtained by the NX-borehole jack method. To explain the discrepancy, the influence of fractures and test variables, such as depth, orientation, hole location, and applied pressure on the calculated modulus of the rock mass, were analyzed by factorial analysis. It was found that the orientations and measurement depths have statistically significant effects. The in situ deformability values obtained by nonlinear regression analysis were also found comparable with other measurements and empirically predicted values for the basalt rock mass.

Jan 1, 1984

This brief resume of events, transpiring in Mexico, culled front the daily New York newspapers, since the last Bulletin-went to press, does not indicate any degree of improvement in the situation. RECORDS OF 217 MEXICO KILLINGS SUBMITTED BY AMBASSADOR FLETCHER Henry P. Fletcher, the American Ambassador to Mexico, called as the first witness before the Rules Committee of the House which has begun a preliminary inquiry into conditions in Mexico, which, it, is believed, will lead to a thorough and far-reaching investigation by a joint Senate and House Committee of the entire Mexican problem, submitted a list of the names of Americans officially known to have been killed in Mexico, a majority of them murdered in cold blood, since the overthrow of Porfirio Diaz by Maderoin 1911. The list contains 217 names and in comparatively few instances do the records show that arrests were made by the particular Mexican faction that happened to be in power where the crime was committed. In only one instance, that of John B. McManus, who was killed in March, 1915, was reparation made. It is significant that McManus was killed by Zapatistas, and Zapata officials apologized for the crime and paid to Mrs. McManus a voluntary indemnity of $20,000 in gold. Of the 217 persons listed as victims of the Mexicans, .137 perished since Carranza came into power. The list, it was admitted, is not complete. It was evident, says the New York Times, that the Ambassador considered the situation very serious.

Jan 9, 1919

By E. S. Bardwell

TWENTY years ago, W. T. Burns, in his paper presented at the Butte Meeting of the Institute, discussed the general scheme then in use in the electrolytic copper refinery of the Anaconda Copper Mining. Co. at Great Falls, Mont., for removing impurities from tank-room electrolyte and controlling its acid content. Since then marked changes have taken place in copper-refinery practice at Great Falls. The electrolytic copper refinery in use in 1913 has been replaced by a new and entirely modern plant capable of producing up to 27,000,000 lb. of cathode copper per month. With the building of the new plant in 1916, the treatment of converter anodes was discontinued. At first the substitution of refined anodes for converter anodes resulted in a decrease in the impurity content of the anodes, but as time went on, changes in metallurgical practices at the smelter resulted in substantial increases in the impurity content of the anodes. The leaching of the silver slime to remove copper before shipment to Raritan for treatment further added to the purification problem. The fact that the scheme of purifying electrolyte which Mr. Burns described in his paper' has proved adequate for our needs under a wide variation of conditions speaks well for its essential soundness.

Jan 1, 1933

By B. H. Bergstrom, Will Mitchell, T. G. Kirkland, C. L. Sollenberger

In a previous article' the authors outlined a study I of the variables in rod milling and also reported data from a series of open circuit grinding tests on a massive limestone in a 30-in. x 4-ft end peripheral discharge rod mill. As a second part of the experimental program, an analysis is now presented for the 30-in. x 4-ft overflow rod mill grinding under identical conditions, except that discharge ports on the periphery of the mill shell have been sealed so that the products from the present series overflowed through a 9-in. diam opening in the center of the end plate. A variance analysis has been made of the combined data for the two experiments, and performances of the two mills are compared here. Included in the first report were descriptions of feed preparation, rod mill circuit, instrumentation and controls, and techniques used to evaluate data. Dependent and independent variables were defined, and variance analyses were made to test the relative significance of variables and to establish magnitude of error for the experiment. Significant data were plotted in various combinations, and conclusions were drawn from the graphs. The procedure and analysis in this series of tests follows the first tests and is not repeated.

Oct 1, 1955

By C. E. Birchenall, C L. McCabe

IN attempting to extend vapor pressure measurements of the type previously reported by Schadel and Birchenall1 for silver and by Schadel, Derge, and Birchenall' for silver-silicon to other systems, it was observed that the materials melted at indicated temperatures 10" to 15" below their accepted melting points. Further investigation revealed that the thermocouple readings were in error due to appreciable conduction losses along the reference thermocouple wires. If the wire diameter of the reference couple inserted into the Knudsen cell was reduced, the correction for the indicating couple changed in a manner tending to explain the melting behavior. When extrapolated to zero wire diameter from measurements with several reference thermocouples of different wire thickness, the melting point of silver then agreed with the indicated temperature at which silver chips were observed to coalesce into a sphere. Approximately the same calibration was given by observing the melting of small wires of silver or gold in the Knudsen cell connected in series with an ammeter, where the leads into the cell were very fine in order to minimize heat conduction. Unfortunately neither of these methods seemed to yield a sufficiently precise temperature calibration to match the apparent precision of the other aspects of the vapor pressure measurement. It was decided. therefore, to redetermine the vapor pressure of silver in another setup under conditions permitting precise temperature measurement. The vapor pressure of pure silver could then be used as an internal calibration of temperature in the older unit in making runs on alloys. This has been done; the present report is a correction to ref. 1. Experimental Procedure The apparatus, shown in Fig. 1, was very similar to that employed by Harteck,3 except that the orifice sizes were smaller and the residual pressure in the vacuum system was probably much lower. A small, sharp-edged hole, nearly circular in shape, was ground into the rounded end of a quartz tube. The orifice area was then measured by tracing the image at known magnification on graph paper and counting the squares enclosed. The silver specimen was sealed into the tube to make a Knudsen cell. A tantalum jacket surrounding the cell served to increase the uniformity of temperature. This assembly was placed in the bottom of a long quartz tube with an inside diameter of about 1 in., which was connected to the vacuum system through a ground joint sealed with picein wax well removed from the furnace. A thermocouple tube inserted through the top of the vacuum line reached into the tantalum jacket so that the thermocouple junction was immediately adjacent to the Knudsen cell except for the protection tube wall. A resistance furnace could be raised to cover the end of the quartz tube containing the cell in such a way that the cell was in the uniform temperature zone 13 in. from the end of the furnace. An ionization gage was included in the vacuum system in the cold lines of wide diameter, immediately beyond the ground joint. The vacuum system consisted of a mercury one-stage diffusion pump, backed by a Welch duo-seal mechanical pump. The pumps were separated from the reactor chamber by a dry ice trap. The ionization gage always read less than 10-5 mm Hg after initial outgassing and before each run was started. Each newly filled Knudsen cell was evacuated at high temperature overnight before the first weighing was made. The cell was returned to the system, heated for a measured time at constant temperature, cooled, and reweighed. The heating and cooling times were quite short since the hot furnace was raised to receive the reactor at the beginning of the run and removed again at the end. The tube heated or cooled quickly. The total mass loss was attributed entirely to effusion of silver vapor from the quartz cell, since empty quartz cells maintained constant mass through similar heating cycles. The vaporized silver condensed on the cold walls of the quartz tube extending above the furnace. Earlier studies in the induction heated unit had shown that the same vapor pressure was found for silver, whether the silver was in contact with the tantalum metal cell or with porcelain or quartz liners. The Pt-Pt-10 pct Rh thermocouple was calibrated against a secondary standard of the same material and found to agree with the published tables. Always operating in air at temperatures below 100O°C,

Jan 1, 1954

By J. T. Norton, A. L. Mowry

The monocarbides of the A subgroup elements in the fourth and fifth group of the periodic table in addition to being hard and refractory are of special interest in that they are isomorphous in crystalline structure. They are cubic with a sodium chloride type structure in which the metal atoms are essentially close packed in a face-centered cubic arrangement with the carbon atoms placed in the interstices between. Interstitial structures of this close packed type were first investigated systematically by Egg1 and he gave the rule for their formation, stating that the radius ratio of the nonmetal to the metal atom should not exceed the value of 0.59. The carbides of interest are those of titanium and zirconium of the fourth group and vanadium, columbium and tantalum of the fifth group. Table 1 shows the radius ratio using the Goldschmidt radii for 12 coordination for the metal atoms and the diamond radius for the carbon atom. It will be noted that while there is considerable variation in the size of the metal atom, in all cases the ratio is smaller than the limit of 0.59 placed by Hägg. It has been known for some time that these cubic carbides are soluble in one another, at least to some extent or, in other words, the metal atoms can be replaced, one by another without destroying the stability of the structure. Since the stability of these close packed interstitial substances appears to depend more upon geometry than upon the exact chemical nature of the atoms involved, it is of interest to examine the possibilities of replacement in these carbides in some detail. Hume-Rothery2 has pointed out the importance of the difference in size of solute and solvent atom as a factor in limiting the solubility in simple binary solid solutions. Largely on an empirical basis, he states that if the difference in size between solvent and solute atom is more than 14-15 pct of the solvent atom, the range of solubility is very restricted. The atom size was based on the distance of closest approach in the elements involved. While there is some question as to how one should calculate the size of the metal atom in the carbide structures, reference to Table 1 will show that zirconium is the largest and vanadium the smallest of the group and that the difference is about 15 pct. The Ti-Zr difference is about 9 pct and the others are smaller. Thus one would predict that if the size factor controls the solubility, all of the pairs except VC-ZrC would have wide or complete solubility whereas this latter pair is on the border line and might have restricted solubility. The purpose of the present investi- gation was to examine the solubility of the several pairs of carbides by heating them together until equilibrium was established and then examining the product by X rays. Previous Work Agte3 and his associates prepared various transition metal carbides and determined the melting points of binary mixtures. He concluded from the shapes of the melting point curves that there was extensive solubility in the case of the cubic carbides. Umanskii and his colleagues made an investigation of a number of pairs of the cubic carbides, using X rays and plotted lattice parameter vs. composition curves for the systems TaC-Tic, CbC-Tic, TaC-ZrC and CbC-ZrC. All pairs showed a continuous series of solid solutions. The first two pairs gave a linear relation while the latter two showed a negative deviation from Vegard's law. Kiefer and Nowotny, in a paper which became available after the present work was well advanced, investigated the binary pairs of the five cubic carbides by means of X rays. Relatively few points were obtained and results indicated that in some cases, at least, equilibrium was not reached at the temperatures used. The results indicated that solubility in the VC-ZrC system was not complete. All of the results of previous investigations indicated the desirability of a more detailed study. Materials The raw materials used were mono-carbides of titanium, zirconium, vanadium, columbium and tantalum and were the purest which could readily be obtained commercially. Spectrographic qualitative analysis showed that the CbC and TaC contained less than 1 pct

Jan 1, 1950

By P. A. Beck, Hsun Hu

It has been known for many years that in cold drawn polycrystalline aluminum the recrystallization texture is practically identical with the deformation texture.l,2,3 V. Goeler and Sachs4 stated that in cold rolled polycrystalline aluminum, too, the deformation texture is retained upon recrystallization. This behavior was interpreted by Dehlinger9 as an indication that each recrystallized grain inherits the orientation of the matrix in which it grew. However, Burgers and Basart showed6 that in deformed aluminum single crystals the orientation of the recrystallized grains strongly deviates from that of the matrix. Barrett demonstrated8 that even in deformed polycrystalline aggregates the local orientation within each deformed grain changes on recrystallization. No explanation has as yet been offered of how the aggregate texture can be retained, while the local texture is everywhere changing. According to Burgers and Louwerse6 the orientation change on recrystallization in compressed and rolled aluminum single crystals corresponds to a rotation around [112] axes lying in the active slip planes and perpendicular to active slip directions. This orientation change was rationalized by them on the assumption that the orientation of the recrystallized grains is determined by the orientation of the available nuclei, and that these nuclei are small fragments of the deformed crystal, rotated in the deformation process. Barrett pointed out,? however, that these assumptions were by no means proven, and that the total volume of material necessary for the nuclei is so small, that it must be available in any orien- tation whatever. It is, therefore, unlikely that an "oriented nucleation" theory could satisfactorily explain the orientation changes in recrystallization of a deformed crystal. Furthermore, in contradiction to Burgers and LOU-werse's conclusions, Barrett's results for the orientation change could be best expressed in terms of rotations around. [Ill] axes. Thus agreement is lacking not only in the interpretations but apparently even in the experimental results contributed by the various investigators. The orientation relationships on coarsening* in a highly oriented polycrystalline matrix were first investigated by Burgers and Basart.5 They produced a fine grained highly oriented matrix by the recrystallization of a compressed or rolled single crystal of aluminum, and studied the orientation relationships in three successive generations of crystals: the "deformation texture" in the single crystal, the recrystallization texture, and the coarsening texture. Burgers24 showed that the preferred orientation of each successive generation was almost always widely different from that of the preceding one, but that the coarse grains often approximately reverted to the orientation of their grandparent, the deformed single crystal. This observation, and the idea that the orientation of the coarse grains is determined by that of the available "nuclei," led to the concept that the coarse grains are nucleated by the remnants of the deformation texture.12,15 On the other hand, Bowles and Boas16 found, in a carefully conducted experiment, that in recrystallized fine grained copper of cube texture coarse grains grow in orientations which can be derived from the orientation of the recrystallized matrix by rotation around a [lll].] direction: the coarsening texture here does not appear to be related in any simple manner to the original rolling texture from which the cube texture had been obtained by recrystallization. It may be assumed that in a recrystallized material, even with a strong texture, there always are present some grains of practically any orientation. These may serve as "nuclei" for the coarse grains, provided that the conditions are favorable for their growth. The existence of a coarsening texture may be considered as an indication that grains with certain relative orientations with respect to the preferred orientation of their neighbors can grow much faster than others. This "oriented growth" theory was briefly suggested by van Arkel, as early as 1936,13 and it was mentioned by Burgers." Recently, C. G. Dunn produced direct

Jan 1, 1950

By N. Nakanishi, C. M. Wayman

The effect of small copper additions on the mar-tensitic transformation behavior in Au-47.5 at. pct Cd was studied by measuring electrical resistivity as a function of temperature. The transformation behavior was found to change and transformation start (M,) temperatures for both the ß to ß' and ß to ß' transformations were depressed substantially by the addition of small amounts of copper. Both M, temperatures were lowered approximately 70°C per at. pct Cu. Copper also had the effect of narrowing the transformation hysteresis region (resistivity us temperature), and for the alloy Au-47.5 Cd-1.5 Cu there was little or no hysteresis; in this alloy, the reverse transfmmation upon heating apparently occurs below the thermodynamic equilibrium temperature, To. THE ß phase in the Au-Cd system occurs at the electron/atom ratio 3/2, and is similar to other ß phases in alloys based on copper, silver, or gold. It is of the CsCl type, in which a considerable degree of long-range order persists to the melting temperature.' The phase boundaries of the ß phase are not known precisely below 300° C, but at room tem- perature the phase exists from approximately 46 to 52* at. pct Cd.2 At low temperatures, the ß phase transforms in a diffusionless (martensitic) manner. Alloys having a composition near 47.5 pct Cd transform upon slow cooling to an orthorhombic3 phase, ß', at - 60°C. Alloys having a composition near 49.0 pct Cd, transform at - 30°C into a phase, ß", which has been recently identified as trigonal.4 Alloys having compositions near 48.5 pct Cd will transform into both the 0' and 0" phases over a range of temperatures. The progress of transformations can be observed

Jan 1, 1963

By Newell G. Alford

At its meeting in the fall of 1937, the Executive Committee of the Coal Division considered the growing scarcity of young engineers entering coal mining with serious intentions. This scarcity was the cause of considerable alarm and a committee consisting of C. T. Hayden, E. A. Holbrook, C. E. Lawall and L. E. Young, with the writer as chairman, was appointed to gather factual data on the current trend. A questionnaire1 was designed and mailed to the heads of the 60 mineral technology schools listed by Prof. W. B. Plank in his article in September 1937.2 Replies were received from 46 institutions, not all from heads of coal-mining courses but all from men that at one time or another have had experience with some kind of coal-mining curricula and know current student impressions. Our committee is indebted to all of these gentlemen for their cooperation. Our committee hoped by this means to quickly reach the root of the trouble and make a set of comprehensive recommendations to the Coal Division for relieving the industry immediately from the growing dearth of youth who yearn for coal-mining careers, but the condition is more serious than at first diagnosed. We must now refer the question back to the Coal Division, with the recommendation that the Division get the industry's permission for still another major operation on its frame of mind. In addition to 10-year statistics on the first pay received by graduates in coal mining and other technical work, we requested enrollment data for 20 years from all schools with either mining engineering or mineral technology curricula. Nine leading questions were also plied, as shown in the Appendix. Every one of the answers was significant and interesting. Fortunately, we encountered positive frankness that was extremely helpful.

Jan 1, 1938

By Newell G. Alford

At its meeting in the fall of 1937, the Executive Committee of the Coal Division considered the growing scarcity of young engineers entering coal mining with serious intentions. This scarcity was the cause of considerable alarm and a committee consisting of C. T. Hayden, E. A. Holbrook, C. E. Lawall and L. E. Young, with the writer as chairman, was appointed to gather factual data on the current trend. A questionnaire1 was designed and mailed to the heads of the 60 mineral technology schools listed by Prof. W. B. Plank in his article in September 1937.2 Replies were received from 46 institutions, not all from heads of coal-mining courses but all from men that at one time or another have had experience with some kind of coal-mining curricula and know current student impressions. Our committee is indebted to all of these gentlemen for their cooperation. Our committee hoped by this means to quickly reach the root of the trouble and make a set of comprehensive recommendations to the Coal Division for relieving the industry immediately from the growing dearth of youth who yearn for coal-mining careers, but the condition is more serious than at first diagnosed. We must now refer the question back to the Coal Division, with the recommendation that the Division get the industry's permission for still another major operation on its frame of mind. In addition to 10-year statistics on the first pay received by graduates in coal mining and other technical work, we requested enrollment data for 20 years from all schools with either mining engineering or mineral technology curricula. Nine leading questions were also plied, as shown in the Appendix. Every one of the answers was significant and interesting. Fortunately, we encountered positive frankness that was extremely helpful.

Jan 1, 1938

By Samuel H. Dolbear

THE purpose of a technical report is to record facts, usually collected by investigation, and to interpret these facts in understandable language. The audience may range from a small shareholder without technical knowledge, to a highly trained engineer or geologist. If the client is a mining company with technically trained executives, the report writer's problem is relatively simple. The writer will then be appraised not only for his conclusions, but for clarity of language and organization of the report. If the writing is bad, the construction careless, and there is a failure to clearly convey to the reader the facts and the author's conclusions, the report is a failure and the writer may have damaged his professional character. Spoken words die quickly, written words may constitute a permanent record and if they are badly composed they may rise up to damn the author. "A good measure of an author's understanding of his subject is his ability to express it clearly in plain words." Good English Teachers in the fields of mineral technology have frequently complained that even in post-graduate groups there is an appalling indifference to their appeals for good English. Some have even noted a student's belief that the use of refined English is effeminate. If those with such immature beliefs could measure the pay-check damage arising from the use of "sloppy" language, they would realize that precision and refinement in English may be quite as important as technical accuracy. When the reader audience is without technical knowledge simplicity in treatment becomes especially important. If one is engaged in consulting work, in government service, or in any field where reports have public distribution, the language employed should be technically adequate but simple enough to be understood by non-technical readers. For example, one may use the term "visual" in place of "megascopic." Technical language can be so obscure that it cannot be understood even by highly-trained students. In the March-April (Vol. 47-No. 2) issue of Economic Geology, Nicholas Vanserg ridicules these extremes and quotes various paragraphs from published material, such for example: "However, lattice orientation unaccompanied by cognate dimensional orientation can never be attributable to growth from an isotropic blastetrix." "The temperature declines because of cessation of the exothermic chemical and mechanical equilibriopetal processes." These he calls "good geologese" and they are calculated not only to baffle the reader but to impress upon him the erudite character of the author. Revision In some cases, difficulty arises from the fact that the writer is too close to the subject and unconsciously assumes that his reader is equally familiar with the background of the report. It is difficult for the writer to regard his work objectively and to determine to what extent it is likely to be understood. Every important manuscript will gain in clarity if the author will have it reviewed by an informed reader. But the writer must not be oversensitive to criticism and should not treat his composition as perfect and beyond the possibility of improvement. The first draft of a report always requires revision, regardless of the care used or the ability of the writer. Three or four revisions are not uncommon. The first draft usually requires expansion in places, the deletion of non-essential material, and language changes to promote clarity of expression. This should be done by the author after a lapse of time, even if only overnight, in which his mind has been occupied on some other subject. Possible improvements are always more visible. The manuscript should be passed on to another reader for further suggestions. Organization of Material The engineer should study available reports and library references before going into the field. If the previous reports have been responsibly done and can be accepted as correct, then much field time can be saved. It is, of course, customary to make some on-the-ground checks to confirm earlier reports, particularly those relating to ore reserve which may have undergone changes. Report writing requires time and expense, but nevertheless, the basic reasons for conclusions should be presented even in the case of a worthless property, for it may prevent a duplication of the work. If the mine examined is obviously of no further interest, no useful purpose can be, served by preparing a report in detail. In one case an engineer travelled all the way to South America only to find that the mine had been grossly misrepresented and was valueless. His cabled report "Nonsense" is a case of over-simplification, but it served his company's purpose. The first step in report organization should be the selection of subjects. This should be done at the mine, and the data collected for each subject should be reviewed in considerable detail on the ground. Otherwise one may find that he has failed to collect some essential details not readily obtained after he has returned to headquarters. If the property to be described is undeveloped, then many of the subject titles are automatically eliminated. Usually no useful purpose is served by an attempt to calculate the cost of production under such circumstances, although the cost of exploration

Jan 1, 1952

By John F. Allan

This paper does not pretend to advance any facts or improvements not known to many members of the Institute, but is intended merely to give a few practical hints on preliminary tests, and to call attention to a possible enlarged field for the cyanide process in the treatment of some silver-ores, which merits investigation. Broadly considered, the choice of a process for the treatment of silver-ores in Mexico is confined to the following alternatives: (1) Concentration for treatment by smelting; (2) milling and pan-amalgamation; (3) the patio and Ortega process; [4) chloridizing roast and lixiviation; (5) chloridizing roast and cyaniding; and (6) cyaniding of the crude ore. These methods of treatment may also be combined, and cyaniding or concentration, or both, may be introduced, at what-ever stage it is found to be most advantageous. The characteristics of the ore (especially its gold-content) and local conditions, such as distance from railway, cost of fuel, amount of water available, vary so much that it is impossible to make general comparisons between the different processes, either as to extraction or cost. Concentration and subsequent smelting may be made very expensive by long-distance transportation of concentrates; pan-amalgamation is undoubtedly expensive; and the patio process is barred when the ore contains appreciable amounts of gold, by reason of its poor extraction of that metal; yet there are many ores for which each of these processes is especially adapted, and the expense of treatment is compensated by the results obtained.

Jan 1, 1905

By Blamey Stevens

(Butte Meeting, August, 1913.) THE following paper aims to make a full explanation of the phenomena of rock jointing. It may be unnecessary to give any general description of what are termed joints in rocks, but. Professor Geikie's clear and faithful generalizations are so illuminating that no excuse need be given for introducing the following and other quotations into this paper: "Almost all rocks are traversed-by vertical or highly inclined divisional planes termed joints. These have been regarded as clue in some way to contraction during consolidation (fissures of retreat) ; and this is no doubt their origin in innumerable cases. But, on the other hand, their frequent regularity and persistence across materials of very varying texture suggest rather the effects of internal pressure-and-movement within the crust."1 General Explanation.-In this paper I show that the phenomenon of jointing may to a large extent be accounted for by the pressure of the water contained in the pores of the rock. To understand this, each constituent grain of. the porous material may be considered to be separately compressed by the 'water which submerges it. As all the grains are held together by cohesion, the whole mass is contracted by this pressure. In an indefinitely extended mass, however, there must be a limit to the possible contraction without rupture, because the material is restrained from. moving freely by other material around its boundaries. The mass of rock thus becomes broken up. This phenomenon is known as " shrinkage " jointing. The terra "shrinkage" is an apt one, if it be understood that the shrinkage of the rock is often brought about by change of stress. Stresses.-The compressive component of water stress on the individual grains is evidently the same as that of the water with which it is in contact. This is so, both. before and after the jointing is formed. Before the jointing is formed there is, however, a tensile stress in one or more directions which keeps the material from contracting.

Jan 7, 1913

By D. O. Hobson, P. L. Rittenhouse

We have recently found that many lots of Zircaloy-2 and -4 tubing tested in tension deform to cross section shapes that are "polyhedral" rather than circular. The noncircular cross sections seem to result from a circumferential variation in plastic proper -ties and, therefore, in texture. We examined the diffracted X-ray intensity from (OOOl), {1010), {ll20}, and {1011} planes parallel to the tubing surface around the entire circumference. Tubing that deformed to a circular cross section showed <5 pct variation in diffraction intensity around the circumference from any of these planes. Greater intensity variations were found for all the tubing materials that developed non-circular cross sections during deformation. In each instance the number of intensity maxima and minima was consistent with the number of sides of the &apos;polyhedral" cross section. THE effects of crystallographic texture on the mechanical properties of zirconium, zirconium alloys, and other anisotropic hexagonal materials such as titanium and hafnium have been intensively studied. If the natural crystallographic anisotropy of these materials could be controlled by selected fabrication operations, a material could be produced with a texture, or preferred orientation, in which the maximum strength directions are in the stress directions of the structure. The permissible stress levels of the structure could then be increased. Rittenhouse and Pickle-simerl have shown that highly textured Zircaloy-2 plate can vary from 52,000 to 70,000 psi in tensile yield and from 62,700 to 122,000 psi in compressive yield strengths as a function of specimen orientation. Similar texture effects have been observed in Zircaloy tubing, whose mechanical properties differ depending upon whether the tubing has basal poles predominantly radial or tangential and upon the mode of testing. These same texture effects might be troublesome if the texture in the tubing is not uniform around the tube walls. This paper is concerned with the effects of nonuniform texture on the strain behavior of commercial Zircaloy tubing. BACKGROUND Previously, various lots of commercial Zircaloy tubing were tested under selected stress conditions as part of a program to determine the four quadrants of the yield locus. One of the testing procedures was uniaxial tension and it is the influence of texture variations on the tensile deformation behavior of the tubing that is of interest here. The effect of texture on the strain behavior in tubing is very apparent from a uni-axial tensile test.2 This behavior is illustrated schematically in Fig. 1 for three different tubing textures: 1) basal poles predominantly in the radial direction; 2) basal poles predominantly in the tangential direction, and 3) basal poles equally distributed between the radial and tangential directions. In the first example most of the grains are oriented for prism slip to operate to allow axial lengthening and diametral reduction of the tube. Reduction in wall thickness requires {1122} twinning, a more difficult operation than slip.* In the second example, the texture is such that *The singleCrystal analogy will be used quite often in this paper when strong texturesare being discussed. The textured material is assumed to react as if it were a single crystal aligned in the same orientation and under the same stress system as the predominant texture._____________________________________________ prism slip operates to give axial lengthening and wall thinning. Diametral reduction requires twinning and again should be more difficult to accomplish. A specimen with basal poles equally distributed between the radial and tangential directions should exhibit about equal diametral and wall strains.* Table I shows the *Diametral strain is accomplished by a combination of circumferential and longitudinal strains. But, for the purposes of this paper, it will be considered as a strain causing a change in the length of a specified diameter.__________ strain behavior of two lots of tubing with different textures. The first tube has a texture with basal poles equally distributed between the radial and the tangential directions. The ratio of true thickness strain to true diametral strain is almost unity. The second tube has a predominantly radial basal pole texture and it is apparent that most of the total strain has occurred by diameter reduction, just as one would predict. There is over three times as much diametral strain as thickness strain. RESULTS We found that specimens from certain lots of commercially fabricated tubing did not retain round cross sections during uniaxial testing. Instead, the speci-

Jan 1, 1970

By D. W. Lillie

It has been demonstrated that considerable bend ductility exists in bulk specimens of polycrystalline high-purity silicon. The possibility of hot-forming at 1200°C is suggested. EXCELLENT corrosion resistance in many media and low cross section for absorption of thermal neutrons (0.13 barn) would make silicon of interest to nuclear engineers were it not for extreme brittle-ness and the difficulty of fabrication by any reasonable means. The use of silicon for structural purposes also has been considered in view of its light weight and oxidation resistance. Johnson and Han-sen&apos; have investigated the properties of silicon-base alloys and concluded that there was no way of making pure silicon or silicon-rich alloys ductile at room temperature. In view of reports of appreciable ductility in germanium single crystals above 550°C&apos;." and some plastic deformation in single-crystal silicon above 900oC,&apos; the present investigation was undertaken to define more precisely the limits of high-temperature ductility in pure silicon. After this investigation was begun torsion ductility in both germanium and silicon was reported by Greiner." Through the courtesy of F. H. Horn, a small bar of cast extra high-purity silicon was obtained and small bend specimens were made from it by careful machining and grinding. All of the reported tests results were obtained from samples from this bar (bar No. 1) and one other of similar source (bar No. 2). No complete analysis was obtained but, based on analysis of similar semi-conductor grade material, metallic impurities were under 0.01 pct total. Vacuum-fusion analysis for oxygen showed a value of 0.0018 2 0.0003 pct for the first bar tested and metallographic analysis showed no evidence of a second phase. Bend tests were carried out on an Instron tensile machine using a bend fixture with a 1 -in. span loaded at the center. Supporting and loading bars were 0.250 in. round and the load was applied by downward motion of the pulling crosshead of the machine. Specimen thickness and width were approximately 0.10 in. and % in. respectively. Loading rate was controlled by holding crosshead motion constant at 0.02 ipm. In some cases a smaller specimen was used on a 5/8-in. span with a 0.129-in.-diam loading bar. The entire bend fixture was surrounded by a hinged furnace and all heating was done in air atmosphere. Temperature measurement was made with thermocouples fastened directly to the bend fixture within less than 1 in. from the specimen. Autographic stress-strain curves were recorded during each test, and breaking load, total deflection, and plastic strain could be obtained from these curves. Stress was calculated from the beam formula S = 3PL/2bh2, where P is the load in pounds, L the span in inches, b the specimen width in inches, and h the specimen thickness in inches. This formula is strictly correct only in the elastic range but has been used to calculate a nominal stress for convenience in the plastic range. The stress given is the maximum stress in the specimen. Results The results of the complete series of tests are shown in Table I. The first group of tests (specimens Nos. 1-6) showed the beginning of plastic flow at a test temperature of 900°C, so two additional tests (Nos. 8 and 9) were made at 950°C on small-size specimens from bar No. 2. Specimen No. 8 was tested in the as-machined condition, and No. 9 was heat-treated in hydrogen at 1300°C for 2 hr, cooled to 1200°C and held 1 hr, cooled to 1000°C and held 1 hr, cooled to 900°C and held 1 hr, and finally cooled to a low temperature before removal from the hydrogen. It is apparent that the heat-treatment had a significant effect on yield strength and ductility. In addition, the magnitude of the yield point was conslderably reduced in the heat-treated specimen as is shown m Fig. 1 by tracings of the stress-strain curves. After obtaining a furnace capable of reaching higher temperatures specimens Nos. 10 to 13 were tested at 1100 and 1200°C. Strain rate was increased by up to a factor of 10 to see whether the ductility observed was excessively strain sensitive. Specimen NO. 10, strained at 0.02 ipm and 1100oC, was still bending at a deflection of 0.322 in. when the load rate was increased to 0.2 ipm, resulting in immediate

Jan 1, 1959