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By W. C. Coffin

Fire-brick stoves have become a necessary part of the modern coke blast-furnace equipment, and are also superseding the cast-iron pipe stoves in anthracite- and charcoal-furnaces. The brick stoves in general use are of either the Cowper or Whitwell type, or modifications of these bearing the names of those who invented the alterations from the original types rather than any real departure from then]. All these stoves have approximately the same valve-equipment and follow the same line of operation. The waste gas from the furnace enters at one port and burns in a single combustion-chamber, and the heated products are drawn through the various passe; in the brickwork to a stack of proper height to create the necessary draught. The last passes of these stoves receive a very small percentage of the heat from the gas, owing to their extreme distance from the combustion-chamber; and this chamber also suffers great deterioration in the attempt to force the heat into the farthest passes. At best, about 70 per cent. of the heat taken up is held in the combustion-chamher and the first down-pass of the Whitwell stoves. Mr. Hugh Kennedy, Manager of the Isabella Furnaces, Pittsburgh, Pa., who has had a large experience with the fire-brick hotblast stoves, was so strongly impressed with the fact that but about thirty per cent of the brick of the average stove were doing proper duty as heat-agents, that, after careful study and experiment, he had three 20- by 60-feet stoves constructed with a view of more uniformly heating all the brick. In these the general lines of the Whitwell stove are followed, with the blast-connections unaltered, but gas is introduced at the bottom of each pass, and outlets are provided at the top, so that the gases have a direct natural draught in each pass and the highest heats are obtained at the bottom instead of the top. The natural tendency being toward the reverse condition, the brickwork soon acquires an almost uniform temperature.

Jan 1, 1893

[*DAVID THOMAB ...................... 1871 *R. W. RAYMOND .1872-1874 *A. L. HOLLEY ....................... 1876 *Asurn 8. H~WITT ................... 1876 *T.ST~RYHUNT ..................... 1877 *ECKLBY B. COXB .1878-1879 *WILLIAM P. BHINN .................. 1880]

Jan 1, 1946

By Richard J. Borg

The vapor pressure of Cd in equilibrium with CdSb in the presence of excess Sb has been measured using the Knudsen effusion method over the temperature range 276° to 379°C. The free energy of formation of CdSb is given by AF° = -1.58 + 1.53 x l0-4 T, kcal per mole. The enthalpy and entropy are obtained from the temperature coefficient of the .free energy. CADMIUM and antimony have almost imperceptible mutual solid solubility but form a single stable intermediate phase, CdSb. This phase, according to Han-sen,l extends from about 49.5 at. pct to 50 at. pct Cd at 300°C and has the orthorhombic structure. The free energy of formation of CdSb can be calculated from the vapor pressure of Cd for compositions which contain less than 49 at. pct Cd. The appropriate reaction and formulae are given by Eqs. [I] and [2]- CdSb(s, ~ Cd(g)-, +Sb(s) [1] Since Sb is in its standard state, Af - N,,AF'-,, = NcdRT In a,, = NcdRT InP/PO [2] In Eq. [2], P, is the vapor pressure of Cd in equilibrium with the alloy, and Po is the vapor pressure in equilibrium with pure solid Cd. It is implicit in this calculation that the free energy only slightly changes within the narrow limits of the single phase field. Thus, the value obtained from the antimony-rich boundary is truly representative of the stoi-chiometric compound. The results reported herein are obtained from a mixture near the eutectic composition, i.e. 59 at. pct Sb. Only two previous investigations" of the free energy of formation of CdSb have been made. Both relied upon the electromotive force method, and measurements were made over relatively narrow temperature ranges which strongly influences the reliability of the values of AH and aS. EXPERIMENTAL The eutectic composition is prepared by fusing reagent grade Cd and Sb by induction heating in vacuo with the starting materials held in a graphite crucible having a threaded lid. The material obtained from the initial melt is pulverized, sealed under high vacuum in a pyrex capsule, and annealed at 420°C for two weeks. X-ray analysis"gives the following lattize parameters: a = 6.436A, b = 8.230& and c = 8.498A using Cu Ka radiation with A = 1.54056. These values are in fair agreement with the result? previously reported by Al~in:4 i.e. a = 6.471A, b = 8.253A, and c = 8.526A. Vapor pressures are measured using an apparatus which has been described elsewhere,= however, with a single important modification. Knudsen effusion cells are made of pyrex with knife-edged orifices made by grinding the convex surface of the lid on #600 emery paper. Photographs taken at known magnifications using a Leitz metallograph enable the determination of the orifice area. Numerous calibration measurements of the vapor pressure of pure Cd give close agreement with values previously reported5,= thus indicating that no significant error can be ascribed to the substitution of glass cells for metal cells used in previous work. Because the vapor pressure of Cd is reliably established and because it is difficult to obtain Clausing factors for the glass cells, the final values used for the orifice areas are calculated from the calibration measurements of the vapor pressure of pure Cd. Effusion runs are started in an atmosphere of purified helium which is quickly evacuated as soon as the cell attains thermal equilibrium. Less than one minute is necessary to obtain high vacuum after evacuation begins, and the temperature seldom varies by more than 0.5oC from the value obtained prior to pumping out the helium. RESULTS The results of this investigation along with other pertinent data are tabulated in Table I. Fig. 2 is the familiar graph of log P against T-10 K. At least mean squares analysis of the data presented in Table I yields the following equation: log1DJP = 8.790 - 6472 x T"1 [3] The deviations of the individual measurements from the values calculated with Eq. 131 are given in column six of Table I; the average deviation is 4.0% of the calculated value. Although the partial molal properties change significantly with composition within the single phase region, the integral thermodynamic value should remain relatively constant. Hence the results of the following calculations, which use the data obtained for the eutectic composition, are probably representative of the equi-atomic compound. Eq. [4] describes the vapor pressure of pure Cd as a function of temperature and may be combined with Eq. [3] to

Jan 1, 1962

This report presents the comments of members of the Institute's Sub-committee on Physics of Mine Ventilation on the proposals of a special committee of the Institute of Mining Engineers (London). This report is as follows: THEORY OF MINE VENTILATION Abstract of a report submitted June 16, 1925, to the Council of The Institution of Mining Engineers by a Special Committee Laws of Flow of Aib The law of flow of air in mine galleries is, at present, expressed by two formulas differing slightly in shape but both derived from the original hydraulic formulas of Chezy and others. These formulas are: The Atlcinson Formula.—Pa = KsV2, which in transformation becomes a3 where P = pressure producing flow; K = coefficient of friction; s = surface of the mine galleries; V = velocity of flow; Q = rate of flow; a = area of mine galleries. This formula is especially applicable to mine galleries, but is unwieldy in application, as in many problems we are dealing with changes produced in the same set of airways when K, s, and a are assumed not to change, and the only variables are P and Q. Great uncertainty prevails as to the exact values to be assigned to the coefficient K in different types of airway, as different workers have given widely differing values. This formula assumes: (I) That resistance to flow is independent of the pressure within the gallery. (2) That changes in volume within the limits of pressure ordinarily met with may be neglected. (3) That changes in density and viscosity and mode of flow of the air may be neglected. (4) That the coefficient K is a constant. (5) That P is proportional to the square of the velocity. We cannot find any reliable experimental work leading us to conclude how far these assumptions are justifiable in mining practice. Equivalent Orifice Formula.—The fundamental form of this formula is Q = ~nA.\/2~11

Jan 1, 1927

By C. A. Heiland

The following summary is written for the benefit of the practical operator in the nonmetallic field who wishes to know what geophysics has done and may be expected to do in his line of work. His problem is quite different from that of the geophysicist who has operated with various or all methods and has followed the literature, and who is assumed to be familiar with the geologic possibilities and limitations of each method. This article is not written for the latter, although he may be interested in the four or five hitherto unpublished surveys described. To the operator, on the other hand, geophysics is only secondary. His problem is to determine which geophysical method is best suited to his special needs. If he wanted to know, however, which method could be used to locate a certain material of given physical properties, building stone, for instance, he would have to wade through a tremendous amount of geophysical literature, bibliographies and articles, before he could find what he wanted. Therefore, the purpose of this summary is to present the geological problems first and then to discuss the comparative merits of the geophysical methods that can be, or have been, applied. Choice of Geophysical Methods in Oil, Civil and Mining Engineering In the first two of these fields, the geological problems are not nearly so complex as in the metal and nonmetallic mining fields. The selection of the correct geophysical method in these fields is not nearly so difficult for the operator. For oil prospecting, his problems have been discussed exhaustively by E. DeGolyer.(1) † In civil engineering (foundation and ground-water work), the usefulness of electrical methods has been so well established that there is hardly any choice of other methods at present. The situation may be changed in the future with the perfection of the seismic reflection method for shallow depths. In the mining field the operator and often the geophysicist himself finds difficulty in determining which method is best suited for a given

Jan 1, 1934

By B. C. Mariacher

EXTRACTION of uranium from ores is being ac-complished by processes which. for the most part, subject the entire ore to acid or carbonate leaching. Ore deposits with a U 3 O 8 content below 0.10 pct U 3 O 8 are seldom considered suitable for treatment by leaching. A preliminary concentration that would enrich the uranium content of an ore by a simple, low cost process based on physical properties of the ore might result in some low grade deposits becoming commercial ores. In addition, the process might be employed in existing operations to reduce transportation and leaching costs and to increase capacity of existing leaching plants. A study to attempt the development of a preliminary concentration process for primary uranium ores was undertaken by the Colorado School of Mines Research Foundation under sponsorship of the U.S. Atomic Energy Commission. The objective of this work was to produce concentrates containing 0.25 pct U3O8 from the low grade ores tested. Ores Tested: The main effort was devoted to the low grade primary uranium ores from northwestern Saskatchewan. Samples were obtained from the Beaverlodge operation of the Eldorado Mining & Refining Ltd. Additional primary ores, obtained from deposits in Gilpin County, Colo., contained from 0.07 to 0.10 pct U3O8. Summary of Concentration Tests: The Beaverlodge ore was tested to determine amenability of the ore to concentration by magnetic, electrostatic, gravity, and scrubbing processes. None of these produced satisfactory results. Both gravity and magnetic processes produced fairly good concentrates when closely sized fractions of the ore were treated, but on the basis of treating the total ore, recovery was poor. Preparation of sized fractions and the low capacity of equipment for suitable concentration made these methods impractical. As flotation offered the advantage of treating the total ore without intermediate sizing, the main effort was in this direction. A flotation process was developed that fulfilled the concentration objectives as set by the AEC. Pilot plant testing was used to verify results obtained from laboratory batch testing. Mineralogy: A petrographic examination of the Beaverlodge ore included a study of polished sur- faces and identification of the radioactive mineral by autoradiograph and X-ray diffraction. Approximate quantitative mineral identification was as follows: quartz, 60 pct; orthoclase feldspar, 20 pct; chlorite, 10 pct; carbonates, 5 pct; and miscellaneous minerals, 5 pct. Included in this last group were plagioclase feldspar, pyrite, mica, chalcopyrite, pyroxene, sericite, magnetite, galena, and uraninite. The most general occurrence of uraninite was in the form of crusts and thin coatings on limonite-stained grains of pyrite, quartz, and pyrite-quartz intergrowth. At least 90 pct of the uraninite was still attached to other minerals in a 100 by 200-mesh size fraction. The uraninite crusts were as small as 10 to 20 µ diam, and 5 to 10 µ thick. The Flotation Process Petrographic examinations of the Beaverlodge ore had indicated the impracticability of attempting to concentrate the uranium by floating individual grains of uraninite. Liberation of the uraninite required grinding to sizes below those suitable for flotation. However, there was preferential association of the uraninite with some minerals while others were free of uraninite attachment. The approach to the development of a flotation process was, therefore, based upon an attempt to concentrate the uraninite by floating carrier minerals. The following paragraphs discuss the various stages of the process with regard to the factors tested and the conditions under which best results were obtained. Grinding: The most effective size range for flotation was —150 mesh + 13 µ. The —13 µ material in the final concentrate had a higher U3O8 content than the total ore, but not as high as the average concentrate; however, rejection of slimes before flotation was prohibitive because of the loss in uranium carried in the —13 µ fraction. Grinding techniques which contributed to a minimum production of fines, such as stage grinding, were then employed. Quartz and Silicate Depression: These minerals represented approximately 80 pct of the ore and were free to a large degree of uraninite attachment. Significant improvement in the grade of the concentrate was obtained by depression of these minerals with hydrofluoric acid or sodium fluoride. Promoter: Selective stage flotation of uraninite carrier minerals was simplified by development of a single promoter mixture. The mixture consisted of an emulsion of a fatty acid, fuel oil, and a petroleum sulfonate and was selected after a comprehensive series of tests. It contained three parts by weight of an oleic and linoleic acid such as Emersol 300,

Jan 1, 1957

By AIME AIME

THE Fall Meetings of the Institute of Metals Division and of the Iron and Steel Division were held in Cleveland from Tuesday, Oct. 20, to Thursday, Oct. 22, as a part of the National Metal Congress. The registration at the technical sessions was something over 450 and the attendance at the joint dinner of the two Divisions on Wednesday evening taxed the capacity of the dining room. The president of the British Institute of Metals, W. R. Barclay, consulting metallurgist to the Mond Nickel Co., Ltd.; of London, was in attendance at several of the technical sessions and was one of the after-dinner speakers at the banquet. He commented on the desirability of greater international amity and cooperation in these troubled times and of the role that technical societies, such as the A. I. M. E. and his own British Institute of Metals, can and indeed are playing in bringing this to pass, with their membership and contacts reaching to all parts of the world. He also referred to the new reciprocal membership arrangements in effect between the A.I.M.E. and the British Institute of Metals.

Jan 1, 1936

By AIME AIME

NATURE was in a smiling mood on December 18, 1883. On that day, Chester Alan Fulton, the sixty-first President of the American Institute of Mining and Metallurgical Engineers, was born, and she endowed him with every good quality within her reach - looks, physique, intelligence, and character. Brought up in the valley of the Hudson River, with the mighty Palisades which make it the "Rhine of America," he has lived up to his early promise - as a man, as an engineer and as a friend.

Jan 1, 1943

I. N. KNAPP, Ardmore, Pa. (written discussion *).-The writer would first call attention to the fact that the mid-Continent field was credited from 1900 to 1915 with a production of about 641,000,000 bbl. of oil with-out any burdensome water troubles being reported. In fact, the authors say the conditions were not acute until about two years ago when the unusual conditions in the deeper oil fields were first encountered. The writer disclaims any personal knowledge of the district mentioned but, from the experience he has gained in directing drilling in various fields by both the cable-tool and the rotary methods and also in plugging and cementing wells, he fails to see how the analysis of water trouble given in the paper under discussion could be of any practical assistance in solving the problems so vaguely outlined. Possibly it might induce academic discussion, if not limited to practical operating conditions. A recent bulletin of the Bureau of Mines gives definite and practical statements that can be easily understood by one skilled in the art of drilling wells and heading off water troubles. From an operating standpoint subsurface knowledge must be based on logs of completed wells. Absolutely no one can have such knowledge as that indicated in Fig. 1 of the paper in question without drilling wells, and no one can question such facts when disclosed by the drill. Under classification of water the paper states "This water (primary) cannot be exhausted from the sands, but its encroachment can often be checked and so directed that wells need not be abandoned, until most of the available oil is secured." This is a live question to the writer. A couple of years ago he had some wells drilled and found the conditions comparable with sands A and D of Fig. 1 with B and C left out; but nothing in the paper, so far as can be found, indicates how this water encroachment is or can be checked or directed particularly under the High heads named.

Jan 5, 1919

By H. M. Shepard

THE copper industry operated at high capacity throughout 1947, with no serious tie-ups in operation as was the case in 1946, when almost the entire industry was shut down by a four-month strike. Refined copper production in the United States averaged 94,250 tons for the first eleven months and deliveries to domestic consumers, including foreign copper for domestic consumption, averaged 114,000 tons per month. On April 29 the import duty of 4d per lb was suspended until March 31, 1949. Copper prices fluctuated considerably for a short time thereafter. Over the year the price of domestic electrolytic copper at refineries on the Atlantic seaboard advanced from 19.225¢ on Jan. 2 to 21.200d on Dec. 24.

Jan 1, 1948

By Frank F. Aplan

In looking into the crystal-ball scene of minerals beneficiation for 1970 and beyond, an impartial observer becomes con- fused as to what has been done and what is possible in the way of improvements. The mining official must balance the burden which is being shouldered by the mineral industry for maintaining our environment in its pristine state on one hand, with the solid advancements made in technology and cost savings on the other hand. Then the official wonders if this is really the criterion for judging overall performance today. As a prospective engineer, Dave Bolles sees it this way: "Specialization has caused many engineers to subordinate everything to doing their job the cheapest and fastest way. In the future this won't be enough. The engineer in the mineral industry will be responsible not only for mining, concentrating and smelting, but also for the resultant wastes- the mine dumps, the tailing dams and the slag piles." (See Drift on page 63).

Jan 1, 1971

By R. J. Marcotte, C. T. Eddy, R. J. Smith

THE objectives of the investigation herein reported were to determine: (I) the S-curves for certain selected cast steels, (2) whether or not the published S-curves for wrought steels are satisfactory for use on cast steels of similar composition, and (3) to prepare hardenability curves of the selected cast steels. In order to make the final comparisons between cast and wrought steel more completely tangible, it was deemed advisable not only to determine S-curves for the steels submitted in the cast condition but also to roll some of the cast-steel test bars and determine comparison S-curves on such wrought material. This procedure eliminates the composition variable and makes it possible to reveal the differences resulting from plastic deformation of the cast structure in addition to providing the comparison with published data on wrought steels. CAST STEELS The cast steels selected for the preparation of S-curves, or time-temperature transformation curves, were similar to S.A.E. series 1030, 2330, 4130 and 4330. Of these the 1030 was supplied by The Crucible Steel Casting Co., Cleveland, Ohio, and the other three by The Sawbrook Steel Castings Co., Lockland, Ohio. The steels were furnished in the as-cast condition. The manufacturers supplied the chemical analyses and the properties that could be obtained in the heat-treated condition-all of which is summarized in Table I. [ ] PROCEDURE The metallographic and dilatometric procedures and equipment were in general standard. The specific technique employed was described in a report of the Steel

Jan 1, 1945

By J. L. Lamont, W. Crafts

Studies of the effect of composition of steel on hardenability by Grossmann,' and as-quenched hardness by Field2 and by the authors, have made it possible to predict the results of quenching when the composition and cooling rate are known In order to extend the application of the hardenability calculation to the quenched and tempered condition in which steel is finally used, a survey has been made of the hardness changes caused by tempering. From this study a method has been developed for the prediction of hardness and tensile strength of steel in the tempered condition. The method of calculation was developed from Rockwell C hardness tests on quenched and tempered Jominy specimens and is expressed in Rockwell C hardness units. It is of an additive type in which the degree of softening from as-quenched hardness is estimated. Tem-pred properties may be calculated within about plus or minus 5 Rockwell C hardness or plus or minus 15,000 lb. per sq, in. tensile strength. This degree of accuracy is less than that necessary for the control of heat-treatment, but is adequate for the comparative evaluation and selection of alloy steels. The formula indicates that tempered hardness is primarily dependent on as-quenched hardness and, as in the hardening reaction, the progress of tempering is controlled mainly by the carbon content. Alloys tend to retard softening by a secondary hardening mechanism in which the alloy appears to migrate from ferrite to the carbide phase. The factors for the effects of alloys in tempering vary so much from the effects of alloys in hardening that different steels of equivalent hardenability may, after like heat-treatment, differ considerably in tensile strength. Procedure In developing the method for calculating tempered Rockwell C hardness, simple and complex steels were tested over a range from 0.08 to 0'65 per cent carbon and up to 2.68 per cent manganese, 2.18 silicon, 3.50 chromium, 4.94 nickel, and 1.06 molybdenum. The steels were made as small induction-furnace heats at the Union Carbide and Carbon Research Laboratories, Inc' The accuracy of the method was finally checked on a variety of carbon, low-alloy and high-alloy types of heat-treating steels produced under commercial conditions. The method was based on a study of tempered Jominy bars, and its validity was tested by correlation with the center hardness and tensile strength of oil-quenched and tempered bars from 1/2 to 4 in. in diameter. The method of calculation was derived from the differences in Rockwell C hardness between as-quenched and quenched and tempered Jominy specimens. Prenormalized Jominy hardenability speci-menS quenched from a normal temperature for austenitizatios were used to obtain a range of as-quenched Rockwell C

Jan 1, 1948

By W. Crafts, J. L. Lamont

Studies of the effect of composition of steel on hardenability by Grossmann,' and as-quenched hardness by Field2 and by the authors, have made it possible to predict the results of quenching when the composition and cooling rate are known In order to extend the application of the hardenability calculation to the quenched and tempered condition in which steel is finally used, a survey has been made of the hardness changes caused by tempering. From this study a method has been developed for the prediction of hardness and tensile strength of steel in the tempered condition. The method of calculation was developed from Rockwell C hardness tests on quenched and tempered Jominy specimens and is expressed in Rockwell C hardness units. It is of an additive type in which the degree of softening from as-quenched hardness is estimated. Tem-pred properties may be calculated within about plus or minus 5 Rockwell C hardness or plus or minus 15,000 lb. per sq, in. tensile strength. This degree of accuracy is less than that necessary for the control of heat-treatment, but is adequate for the comparative evaluation and selection of alloy steels. The formula indicates that tempered hardness is primarily dependent on as-quenched hardness and, as in the hardening reaction, the progress of tempering is controlled mainly by the carbon content. Alloys tend to retard softening by a secondary hardening mechanism in which the alloy appears to migrate from ferrite to the carbide phase. The factors for the effects of alloys in tempering vary so much from the effects of alloys in hardening that different steels of equivalent hardenability may, after like heat-treatment, differ considerably in tensile strength. Procedure In developing the method for calculating tempered Rockwell C hardness, simple and complex steels were tested over a range from 0.08 to 0'65 per cent carbon and up to 2.68 per cent manganese, 2.18 silicon, 3.50 chromium, 4.94 nickel, and 1.06 molybdenum. The steels were made as small induction-furnace heats at the Union Carbide and Carbon Research Laboratories, Inc' The accuracy of the method was finally checked on a variety of carbon, low-alloy and high-alloy types of heat-treating steels produced under commercial conditions. The method was based on a study of tempered Jominy bars, and its validity was tested by correlation with the center hardness and tensile strength of oil-quenched and tempered bars from 1/2 to 4 in. in diameter. The method of calculation was derived from the differences in Rockwell C hardness between as-quenched and quenched and tempered Jominy specimens. Prenormalized Jominy hardenability speci-menS quenched from a normal temperature for austenitizatios were used to obtain a range of as-quenched Rockwell C

Jan 1, 1948

By Edward Saibel

The object of this study is to investigate the effect of prior tensile strain on the fracture stress of a metal. This is done in a theoretical manner starting from the point of view developed by the author in his thermodynamic theory of the fracture of metals. The results are compared with experimental findings and a rational interpretation is given to work that shows the variation of fracture stress with prior tensile strain. Theory op Fracture In the thermodynamic theory of the fracture of metals developed earlier,' it was shown that a critical strain energy per unit volume exists. This is characteristic of the material and may be calculated from basic thermodynamic data. When the area under the flow curve reaches this characteristic value, fracture occurs. The general criterion for fracture is expressed in the form « ± u. = JLJW/V [r] where L, is the latent heat of melting of the unit volume, AV/V is the ratio of the change in volume of the unit volume to the original unit volume on passing from the solid to the liquid state, uo is an initial energy density, and J is a conversion factor, which changes energy from heat to mechanical units. As a first approximation, it will he assumed that the stress-strain curve is the straight line that extends from the point of maximum load onward, extrapolated back to the axis of zero strain, for example, line AC of Fig. I. If the point of intersection of the straight line with the axis of zero strain is represented by v., and the slope of the straight line is p, the analytic form of the flow curve is a = (To + pd [2] and the strain energy per unit volume evaluated from Jud6 becomes (u,6 + pa2/2). When this latter term reaches the critical value JLbVIV (designated hereafter by M), it is assumed that fracture occurs. This leads to the following expression for the fracture stress: a; = V«r.2 + iMp [3] The strain at fracture may be calculated from Eqs 2 and 3. It is assumed in this paper that the initial energy density is either zero or that it may be neglected. Furthermore, the complicated states of stress and of strain existing in the necked region of the tensile specimen after "necking" has occurred will also be neglected for the present, so that average conditions will be assumed to prevail. Flow and Fracture Curves LudwigZ attributed to materials two fundamental properties: (I) a resistance to flow and (2) a resistance to fracture. He reasoned that at each instant the

Jan 1, 1948

By Edward Saibel

The object of this study is to investigate the effect of prior tensile strain on the fracture stress of a metal. This is done in a theoretical manner starting from the point of view developed by the author in his thermodynamic theory of the fracture of metals. The results are compared with experimental findings and a rational interpretation is given to work that shows the variation of fracture stress with prior tensile strain. Theory op Fracture In the thermodynamic theory of the fracture of metals developed earlier,' it was shown that a critical strain energy per unit volume exists. This is characteristic of the material and may be calculated from basic thermodynamic data. When the area under the flow curve reaches this characteristic value, fracture occurs. The general criterion for fracture is expressed in the form « ± u. = JLJW/V [r] where L, is the latent heat of melting of the unit volume, AV/V is the ratio of the change in volume of the unit volume to the original unit volume on passing from the solid to the liquid state, uo is an initial energy density, and J is a conversion factor, which changes energy from heat to mechanical units. As a first approximation, it will he assumed that the stress-strain curve is the straight line that extends from the point of maximum load onward, extrapolated back to the axis of zero strain, for example, line AC of Fig. I. If the point of intersection of the straight line with the axis of zero strain is represented by v., and the slope of the straight line is p, the analytic form of the flow curve is a = (To + pd [2] and the strain energy per unit volume evaluated from Jud6 becomes (u,6 + pa2/2). When this latter term reaches the critical value JLbVIV (designated hereafter by M), it is assumed that fracture occurs. This leads to the following expression for the fracture stress: a; = V«r.2 + iMp [3] The strain at fracture may be calculated from Eqs 2 and 3. It is assumed in this paper that the initial energy density is either zero or that it may be neglected. Furthermore, the complicated states of stress and of strain existing in the necked region of the tensile specimen after "necking" has occurred will also be neglected for the present, so that average conditions will be assumed to prevail. Flow and Fracture Curves LudwigZ attributed to materials two fundamental properties: (I) a resistance to flow and (2) a resistance to fracture. He reasoned that at each instant the

Jan 1, 1948

By C. R. Hayward

THE CHAIRMAN (ALBERT SAUVEUR, Boston, Mass.).-I am sure we are indebted to Prof: Hayward for his addition to our knowledge of the influence of sulphur on steel. As he has said in this paper, sulphur has had many defenders in recent years. It seems to me, however, that, while it may be old school to believe in the detrimental action of sulphur, it is not yet old school to believe in segregation; that while it may be that 0.1 per cent. of sulphur has no very great effect on the physical properties of steel, a ladle analysis of 0.1 per cent. of sulphur may readily result in 0.2 or 0.3 per cent. sulphur being present in the segregated portion of the ingot, and that, it seems to me, might be a rather serious matter. J. S. UNGER, Pittsburgh, Pa.-Prof. Hayward has presented the results of an investigation along a line to which I have devoted considerable time and attention, and I am particularly pleased to note that his results are in accord with my own and further tend to prove the fact that the old, established prejudice against sulphur is based more on belief than actual facts. I have felt for years that tooo much stress was placed on the harmful influence of certain elements in steel such as sulphur, phosphorus, copper, etc., but it has only been within recent years that efforts have been made to, establish the truth. Practically all the investigations made to date have proven that these elements within reasonable limits are harmless and, in fact, that for certain purposes the addition of these elements is beneficial. In referring to copper, J. E. Stead, Vice-President of the British Iron and Steel Institute, said at their last meeting: "Even today one comes across steel specifications in which copper is barred, which can only be regarded as ail indication of ignorance, if not stupidity, of those who prescribe the composition of steel, for it has been long ago proved that copper in steel, instead of being an evil, is quite harmless, and is sometimes distinctly beneficial." Sulphur owes its evil name to the early days of the manufacture of steel. Chemical analyses were crude, and failure due to either poor raw materials or metallurgical treatment were many. Sulphur being a comparatively easy element to determine with reasonable accuracy, particular attention was called to the amount of sulphur, and the failure was attributed to it, without giving any consideration to other causes. A pre-

Jan 4, 1917

By R. Kossowsky, W. C. Johnston

CONSIDERABLE experimental data has been published in recent years on a few directionally solidified aluminum base eutectic alloys. The mechanical properties of A1-Al3Ni eutectic have been studied by Lemkey, Hertzberg, and Ford1',2 and Salkind et a1.3 where the alloy has been demonstrated to behave as a whisker reinforced composite with superior properties over many aluminum alloys. It has also been shown4 that aluminum reinforced with Al3Ni whiskers R. KOSSOWSKY, Member AIME, is Senior Metallurgist, Westing-house Research Laboratories, Pittsburgh, Pa. W. C. JOHNSTON, formerly with Westinghouse Research Laboratories, is Head, Department of Physics, George Mason College, University of Virginia, Fairfax, Va. Manuscript submitted March 28. 1969. IMD__________________ possesses excellent microstructural stability to 508°C. The effect of lamellar structure in A1-CuA12 eutectic was compared3 to the rod-like structure in the A1-Al3Ni eutectic, and was found to be better in low cycle fatigue. This was rationalized3 by postulating that a lamellar reinforcement was more efficient at blocking lateral plastic flow than a rod-like rein-forcement. The purpose of this study is to explore eutectic strengthening in other aluminum base alloys. The Al-Pd system5 forms a eutectic with aluminum and the intermetallic compound A13Pd at 25 wt pct Pd, and has a melting point of 615°C. A13Pd has an orthorhom-bic structure and transforms to hexagonal Pd2A13 at 785°C. Growth characteristics, compression yield strength, creep rupture, and microstructural stability of directionally solidified and as-cast alloys are investigated. Eutectic ingots having a nominal composition of 25 wt pct Pd were prepared by first compacting 1/2 in. diam by a in. high pellets from 99.99+ pct A1 and 99.99 pct Pd powders. The pellets were then levitation cast into 1/4 in. diam by 2 in. long copper molds. Directionally solidified bars were prepared by grinding the cast ingots to 0.195 in. diam, inserting them into alumina

Jan 1, 1970

By Charles W. Frey

SUCCESSFUL mining today means proper mechanization. Before any mine can begin production on a paying scale, some machinery must be installed. There must be pumps to remove water, fans and blowers to provide proper ventilation, elevators and hoists to raise materials, and a source of power to turn the countless wheels on which the world's mineral supply rolls from its earthhound source to the market. Only the prospector with his burro and the anthracite "bootlegger" continue to mine without mechanical aid, and with the recent years even these can be discounted, for the burro has given way to the Model T, and the "independent" coal miner must have a truck to haul his coal away. The few types of machinery mentioned above are but a beginning. The

Jan 1, 1938

By H. L. Luo, P. Duwez, C. C. Chao

BY rapidly cooling alloys from the liquid state, it is possible to obtain solid solutions beyond the equilibrium concentrations, provided that the components are miscible in the liquid state. Typical such cases include CU-Ag,1 Pt-Ag,2 CU-Rh,3 nickel-base alloys with silicon, germanium, and tin,4 and cobalt-base alloys with silicon, germanium, tin, aluminum, and gallium.5 In the present note it is shown that terminal solid solutions can be appreciably extended in A1-Mg alloys. The alloys whose compositions are given in Table I were prepared by induction melting in tantalum crucibles under an argon atmosphere. Both aluminum and magnesium were 99.99 pct pure. Weight losses after melting were less than 0.2 pct for the aluminum-rich alloys and less than 0.4 pct for the magnesium-rich alloys. From these weight losses it was estimated that the compositions of the ingots after melting were accurate within 0.3 at. pct for aluminum-rich alloys and within 0.5 at. pct for magnesium-rich alloys. As indicated in Table I, the compound AuCd10 in which there is an ionic contribution to the bonding. The authors thank Dr. J. H. Westbrook of the Research Laboratory, General Electric Co., for arranging the supply of materials and for his interest. This investigation was supported by the U.S. Atomic Energy Commission under Contract AT(30-1)-1002, Scope I. some of the alloys were also chemically analyzed and the results confirmed the limits of uncertainty based on weight losses. Rapid quenching from the liquid state was achieved by techniques previously described.8,7 The principle of these techniques consists of propelling a small globule of liquid alloy (about 20 mg) onto a copper substrate. The thin foils easily detached from the copper substrate were analyzed by X-ray diffraction using a Debye-Scherrer camera 114.6 mm in diameter and either nickel-filtered copper Ka or iron-filtered cobalt Ka radiation. Since the back-reflection doublets were resolved, the wavelengths used in the computatioas were CuKal = 1.54050A and CoKa1= 1.78892A. Lattice parameters were obtained by extrapolation of the Nelson-Riley function, and the tables compiled

Jan 1, 1964