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OUTSTANDING symbol of the machine age, the steam shovel needs no introduction. Few individuals there are, in the United States at least, that have not watched with fascination the almost human motion, the more than human strength, the rhythm of the whole steam-shovel cycle of crowding, digging, swinging, dumping, swinging, and crowding again. A mass of steel with some copper and other metals, fed with water and coal, guided by a single alert and dexterous operator, or perhaps two, does the work that would require 50 to 500 men or even more. The largest shovels working in the copper mines have loaded into waiting railway cars as much as 10,000 tons of ore in a single 8-hour shift. With no equipment but hand shovels, it would, in fact, be impossible to duplicate the work with any number of men; first, because they would be in each other's way, and second, because the steam shovel can lift single pieces of rock weighing 5 or 10 tons with effortless ease. Of recent years, internal-combustion engines and electric motors have displaced steam as a motive power in many instances; and of course the detailed design of the shovels has been improved immensely. Whereas the largest dippers used 30 years ago had a capacity of 3 ½ to 4 cu. yd., today the 350-ton shovel used at Chino has an 8-yd. dipper, as has the 320-ton shovel at Chuquicamata. Incidentally, for stripping at coal mines a shovel having an 18-yd. dipper is in use. However, the principle of operation of the modern shovel, regardless of the size and type of motive power, is essentially the same as that of the earlier shovels. It is fair to say that the indispensable of open-cut mining is the steam shovel, or, to be more precise, if perhaps less picturesque, the power shovel. Somehow the electric shovel seems to lack the glamour that

Jan 1, 1933

By A. J. Bartlett

Island Creek conditions are generally referred to as ideal; yet, as at all other properties, there are all known hazards of coal mining. The hardest of these hazards to combat is the human element. The basic thought in the minds of the management of these properties is to produce coal with the utmost safety, and it has impressed upon its supervisory force that it does not want a ton of coal unless it can be produced safely. This company has instituted a mine inspection department, which reports direct to the general manager, arid all matters pertaining to safety come under the direction of this department. Through the medium of the inspection department, the management is kept in touch with the actual conditions existing in general at all mines. Inspections are made regularly arid continuously; that is, at all times while the mine!: are in operation some sections of some mines are being examined. These inspections cover all active and inactive workings. Miners are contacted in their working places and other employees at their respective, work. A thorough check is made to see that the state mining laws are complied with and that company safety rules arc being observed. Night shifts receive the same attention as day shifts. All violations and dangerous practices are brought to the attention of the plant supervisory force with suggestions and recommendations; major hazards of emergency nature are taken up immediately with the management. Periodical inspections are also made of all tipples, preparation plants, dumping and hoisting equipment, to see that all machinery is properly guarded, and walkways and platforms properly fenced; conditions of equipmcnt and mechanical defects are also reported. Reports of inspection are written in letter form and in such a manner as to give the management a picture of the existing conditions at the time of inspection. Copies of inspection reports are forwarded to the superintendents with the general manager'? comments. It has been said, "There is nothing under God's heaven that justifies. your creation or your citizenship but this gospel: ' That the next greatest

Jan 1, 1938

By W. S. Hyler, L. W. Berger, R. I. Jaffee

Hydrogen additions of 390 ppm to A-55 titanium and 368 ppm to Ti-8 pet Mn have no deleterious Hydrogenadditionseffect on the unnotched and notched rotating-beam fatigue properties of these materials. 'These amounts of hydrogen, however, are sufficient to cause severe notch-impact thesematerials.embrittlement in A-55 titanium and pronounced loss of tensile ductility in Ti-8 pet Mn. The lack of embrittling effect in fatigue in the latter alloy is consistent with the postulated strain-aging mechanism of hydrogen embrittlement in a-ß alloys. There is a significant strain-agingincrease in the unnotched endurance limit of A-55 titanium with the addition of hydrogen. This increase may be explained as the result of internal heating effects which would dissolve the hydride and cause solid-solution strengthening. TITANIUM and its alloys may be seriously embrittled by relatively small amounts of hydrogen. The form which this embrittlement takes has been shown to vary with alloy type. The a alloys, for example, suffer most strongly from loss of notch-bend impact toughness' when sufficient hydrogen is added, and this effect has generally been associated with the presence of hydride phase in the micro-structure. In a-ß alloys, on the other hand, hydrogen is most detrimental to tensile ductility in slow-speed tests,2-1 and the embrittlement may be detected in a most convincing manner by means of rupture tests at room temperature. This particular kind of embrittlement has not been associated with a change in microstructure, but has been classified rather generally as associated with a strain-aging type of mechanism.' In the present paper, the effect of an embrittling amount of hydrogen on the rotating-beam fatigue properties of both an a and an a-ß titanium alloy is covered. For this study, annealed commercially pure (A-55) titanium was chosen as an a alloy, and equilibrated and stabilized Ti-8 pet Mn as representative of a typical a-ß alloy. Nominal hydrogen levels of 20 and 400 ppm were evaluated, the latter amount having been shown previously to be severely detrimental to the impact toughness of commercially pure titanium and to cause pronounced strain-aging embrittlement in the Ti-8 pet Mn alloy. The only report of the effect of hydrogen on the fatigue properties of titanium is given by Anderson et al.,° in which a push-pull type of fatigue test was conducted on as-received commercial-purity titanium sheet. Much scatter was found in the results, but generally the presence of hydrides slightly decreased the fatigue strength of unnotched specimens in the longitudinal direction. The results of notched tests were masked too greatly by scatter to be significant. Experimental Procedure Preparation of Materials—Analyses of the A-55 titanium and the Ti-8 pet Mn alloy used in this investigation are given in Table I, which indicates the 8 pet Mn alloy to be more nearly a 6 pet Mn alloy. This alloy will be referred to as Ti-8 pet Mn, however, since this is the commercially designated composition. Both alloys were received in the form of5/8-in. diam rod and, after suitable surface preparation, 5-in. lengths were vacuum annealed at 820°C. Half of the rods for each material were then hydrogenated at 820°C to a nominal hydrogen content of 400 ppm. The hydrogenated and vacuum-annealed A-55 rods were hot swaged at 700°C from 5/8-in. diam to 1/4-in. diam, and then annealed 1 hr at 800°C and air cooled prior to preparation into test specimens. Fabrication of the Ti-8 pet Mn alloy was by hot swaging to 3/8-in. diam at 760" and then 1/4-in. diam at 704°C. This material was then annealed 1 hr at 704", followed by furnace cooling to 593"C, and finally air cooling to room temperature. Evaluation—In order to examine more completely the effects of hydrogen on the particular materials studied, slow-speed tensile and notch-bend impact properties were determined in addition to fatigue data. Tensile specimens were of the standard ASTM type with a reduced section of 1/8-in. diam and a gage length of 1/2 in. A subsize cylindrical Izod specimen was used for impact tests. These specimens had a 45" notch with a 0.005-in. radius and a 0.150-in. root diam, and the stress concentration factor of this notch in bending was Kr = 3. Both the ten-

Jan 1, 1959

THE morning session on non-metallic minerals was opened briefly by the chairman, Oliver Bowles, giving the usual instructions and then turning immediately to the introduction of the speakers. "Min-ing and Preparation of the St. Peter Sandstone in' Arkansas" by D. D. Dunkin was first presented by W. M. Weigel, mining technologist for the Missouri Pacific R. R. The paper covered a discussion of the geology of the sandstone, correlating it with the sand-stones at Klondike, Mo., and at Ottawa, III. Its physical appearance, structural characteristics and thickness; the mining methods, blasting, loading, haulage and classification were taken up. A series of slides aided in clarifying the details. The discussion consisted of questioning Mr. Weigel on operating details. The second paper, "Geology and Mining of Diaspore and Flint Fire-Clays of Missouri," written by H. S. McQueen, geologist with the Missouri Bureau of Geology and Mines, and C. R. Forbes, professor of mining, Missouri School of Mines and Metallurgy, was presented by Mr. Forbes. It thoroughly covered the geology, stressing the peculiar sink formations in which all diaspore clay deposits of the region occur. The crudeness of the mining methods was mentioned and believed justifiable because of the small size of the indi-vidual deposits. It was stated that the diaspore and flint clay deposits of Missouri were confined to an area 60 mi. square and it was found in a survey that the average deposit had dimensions comparable to the fol-lowing: 100 ft. long, 75 ft. wide and 50 ft. deep. The largest deposit found was 800 ft. long. 500 ft. wide and 20 ft. deep. It is estimated that the known reserve of clays is from 750.000 to 1,500,000 tons. Mr. Forbes stressed the fact that in mining clays the major problem is entirely one of sorting. This is done under the supervision of a pit foreman trained to make this classification by eye. The mine-run clays are sepa-rated into diaspore clay ranging in alumina content from 70 to about 85 per cent, first grade Burly clay 00 to 70 per cent, and Flint clay 52 to 60 per cent. Discussion of the paper consisted in questioning Pro-fessor Forbes on labor. cost, haulage, drilling, and geology.

Jan 3, 1928

By T. N. Williamson

6.3-1. Historical Development. Rotary drilling has been used in surface mining for many years. Its principal use is for primary blasthole drilling. In this use, holes in the range from 4 to 15 in. in diameter are drilled in overburden and massive ore bodies for large initial blasting operation. With properly designed shot patterns and loading, secondary blasting is seldom required. The use of rotary drilling with diamond bits for exploration is discussed in Chapter 3.1. Small rotary drillholes of approximately 2-in. diameter are employed as blastholes to shatter uncovered coal seams, but this is a minor part of surface mining drilling operations. Another minor use of rotary drills in surface mining is for placing wire saw poles in dimension stone quarries, usually accomplished with large-diameter calyx or steel shot drills. Primary blasthole drilling by the rotary method was performed with drag bits until 1949 (19). Its use in mining was only in soft formations, so that rotary drills prior to that time were found principally in overburden drilling for the surface mining of coal. In 1949 it was found that air circulation to remove cuttings resulted in increased penetration rate and prolonged life for the rolling-cutter type of bits. Prior to that time, and since their introduction in oil well drilling in 1907, water had been used for circulation with these bits. The dependence on water to clean the hole had delayed the acceptance of bits with rolling cutters in mines because of water haulage and freezing problems as well as the loss of water through cracks in the formation. After rolling cutters were introduced, subsequent improvements in tools made rotary drilling adaptable to harder formations (18). This system is now used in the hardest formations encountered in mining. 6.3-2. Principles of Operation. ENERGY. Rotary drills attack rock with energy supplied to the bit by a rotating drill stem, and infrequently by

Jan 1, 1968

By R. T. Moolick, John E. Neill, O&apos

In selecting a particular stripping method the ultimate aim is the removal of material at the least possible cost. Accomplishment of this goal requires the careful consideration of many factors including geologic and topographic information, proximity of the stripping operation to waste disposal areas, possible problems of land reclamation, types of suitable equipment available, and auxiliary equipment requirements. 4.2-1. Selection of Stripping Methods. The size of an orebody and the distribution of values within that orebody normally will limit the variety of economical stripping methods which need to be considered. Much may depend upon the selectivity required in the mining due to the relationship between ore and overburden, as well as the character of the overburden itself. The following factors concerning the geologic nature and environment of an orebody, as well as the production requirements, must be determined before any selection of equipment is made: 1. The size of the orebody and distribution of the values within that orebody. Is the ore massive or scattered, bedded or disseminated, thick or thin? 2. The nature of the overburden to be removed. Is it a hard dense rock, bedded rock (thick or thin), friable material, earth, sand, elay, marsh, etc.? 3. The character and significance of geologic structures (fractures, faults, shear zones, etc.) associated with the ore occurrence. Are there water bearing formations with resulting water disposal problems? 4. In considering the nature of the overburden, including its alteration products, the physical or chemical conditions which, when combined with anticipated climatic conditions, may render certain equipment inoperable during unfavorable seasons.

Jan 1, 1968

By R. I. Jaffee, F. C. Holden, H. R. Ogden, A. G. Imgram

The tensile and notch tensile properties of four refractory metals (molybdenum, tungsten, niobium (columbium), and tantalum) and one alloy (Mo-0.5Ti) were investigated. All the materials were evaluated in bar form, and the molybdenum and Mo-0.5Ti also were studied in sheet form. The notch sensitivity of each material was evaluated on the basis of several criteria, including the notch-unnotch strength ratio, the ductility transition, and the fracture transitions. USE of refractory metals as structural materials in aircraft and space vehicles may subject them to low-as well as high-temperature environments. At elevated temperatures, the usefulness of a material usually is limited either by strength considerations

Jan 1, 1962

By George R. Cowan

A number of studies hare been reported of the effects produced in metals subjected to deformation by shock waves with maximum pressures ranging from tens to hundreds of kilobars. On the basis of the equations for the flow of mass, momentum, and energy through a stationary shock front, the macroscopic stress-strain curve for the resulting shock deformation can be calculated within narrow limits from the experimentally determined Hugoniol curve. In relatively weak shocks which are preceded by an elastic wave, the stress rises above the clastic limit only as plastic deformation proceeds cold thus the shock has a long toe. In strong shocks that override the elastic wave a high stress is applied without prior plastic deformation. A more important effect of increasing the shock pressure is the generation of shear stresses, called supercrilical shear stresses, that exceed the strength of the perfect lattice. A change in the mechanism of deformation is expected to result from the onset of supercritical shear. The shock disordering of ordered Cu3Au in strong shocks appears to be an example of such a change. It is suggested that the formation of fine twins in copper and nickel and the formation of structures which enable visible twins to be formed in the rarefaction ware, observed in copper and presumably in disordered Cu3 Au, are related to the occurrence of supercritical shear in shock dcformation. In recent years several studies1,2 have been made of the changes in structural and mechanical properties of metals produced by the passage through the metals of strong shock-compression waves ranging from about 50 to 800 kbar pressure. Recent work involving dynamic measurements of the shock compression "Hugoniot" curves 3-8 of many metals has developed techniques and provided data required to obtain the shock pressure and the (transient! plastic deformation produced in the shock-conlpression experirnents.9 Shock deformation has been found to be much more effective than slow deformation in changing the mechanical properties of metals, when the two are compared on the basis of equal plasti strain, Holtzman and Cowan9 made quantitative estimates of the shearing stress occurring in a shock front in a metal by assuming that the shearing stress is similar to that occurring in a shock front in a viscous, heat-conducting fluid, with the addition of a yield stress. Taylor's solution9 for a weak shock was used to estimate pairs of values of shearing stress and thickness of the shock front obtained by assumed choices of the ratio of effective kinetic viscosity to thermal diffusivity. It was noted from these values that. unless the shock front is extremely thin. heat conduction has slight effect, and the shearing stress is nearly independent of the mechanism of deformation. This mechanism does, however, determine the thickness of the shock front and the rate of strain. Furthermore, since the maximum possible shearing stress occurring in shocks of moderate strength does not greatly exceed the shear stress occurring in conventional slow deformation, the mechanism of deformation is not expected to be qualitatively different. The greater effectiveness of shock deformation in changing the mechanical properties of metals can be attributed partly to the fact that dislocations, when driven by near-conventional stresses, cannot keep up with the shock front, thus necessitating a higher dislocation density than required for an equivalent slow strain. The fast uni-axial strain occurring in the thin shock front would also be expected to cause a larger number of dislocation intersections to occur. In the upper range of shock pressures that have been studied the estimated values of the shearing stress exceeded the estimated shear strength of a perfect crystal. Under these circumstances it is reasonable to expect that the mechanism of deformation might be considerably different from that involved in slow deformation. Except for the observation by smith1 of twins in shocked copper, the effects of shock waves on metals did not show any obvious or large changes in properties that would indicate the onset of a change in the mechanism of deformation. The recent investigation of the effect of shock waves on ordered and disordered specimens of Cu3Au by Beardmore, Holtzman, and ever" showed a spectacular decrease in the amount of long-range order retained by initially ordered Cu3Au when the shock pressure was raised from 290 to 370 kbar. Since Dr. Holtzman and I suspected that this behavior probably was due to the onset of a shearing stress in the shock front in Cu3Au which exceeded the limiting shear strength of the perfect crystal. it was considered appropriate to examine directly the shock-front equations for a solid. and to obtain a sound estimate of the shearing stress occurring in the front using equation of state data obtained from shock studies. In this paper an estimate is made of the

Jan 1, 1965

By Bartlett W. Paulding

Since its introduction to the petroleum industry in 1949 by Clark,1 hydraulic fracturing or "hydrafracing" has developed into a widely respected and useful technique for increasing production from petroleum reservoirs. Even then, Clark described production increases of from 6 to 100 barrels of oil per day (bopd). Since that time, others have described treatments in which production increased from 12 to 456 bopd, from only a show to 40 bopd;2 from 48 to 219 bopd; 3 from 500 to 1400 bopd and from a show to 192 bopd.4 Although representative of only a few of many successful hydraulic fracturing operational6 these increases in production attest to the past and potential value of the hydrafracing technique to the petroleum industry. The technique has received a considerable amount of theoretical and experimental attention.1, 5-20 Unfortunately, however, the degree of general understanding of the mechanics of hydraulic fracturing is still inadequate to solve many recurring problems. The practicing engineer is plagued with difficulties in predicting such factors as: (1) the required pressure and viscosity of the fracturing fluid to not only induce the fracture but to control the extent of its growth, (2) the strength characteristics and amount of proppant to include in the fluid so that the fracture is held open once the fluid pressure is decreased, and (3) the volume of the reservoir influenced by the induced fractures and the resulting increase in production. A major cause of these difficulties is the uncertainty associated with determining the orientation of the hydraulically induced fractures. One's natural conclusion in considering the problem is that the orientation of the fracture would depend on several variables, as, for example, the relationship between the viscosity and injection rate of the fluid and the

Jan 1, 1968

By Clifford S. Wilson

ScReened pipe is designed with the view of restraining the fine, free-running sands of the production zone from entering oil wells. Its successful use is dependent on a number of factors. The nature and effects of some of these factors can be determined through experiment and observation, but some of the elements that have a distinct bearing on the use of screened pipe can be evaluated only by estimate. The important subsurface conditions which affect the use of screened pipe are: 1. Depth of production zone. 2. Extent of production zone. 3. Reservoir pressure. 4. Character and relative quantity of oil and gas. 5. Character of sediments: a. Cossolidation of beds. b. Variation in beds. c. Grain-size gradation of sands. d. Free-running characteristics of sand from different levels. Aside from the use of mechanical equipment and tools, the measures to be taken in the installation of screened pipe involve: 1. Size of liner. 2. Length of liner. 3. Design and mesh of screen. 4. Portion of liner to be screened. 5. Manner of setting liner. 6. Preparation of or washing of the well before or during the setting of the screen. 7. Manner of bringing in the well. 8. Manner of flowing the well. Values applicable to the actual subsurface conditions that exist at any well can only be approximated. The accuracy of the estimate will be measured by the amount and quality of the evidence at hand and the personal factor of ability to interpret the evidence fairly, whether

Jan 1, 1933

By William H. Shockley

Though China has been widely explored by mining engineers during the past dozen years, comparatively little has been published concerning its mineral resources. The few moilographs scattered through the transactions of various societies contain far less information than the private reports made to the numerous syndicates which have sent out engineers. The best general account of the geolopy and mineral resources of China is to be found in the works of von Richthofen,' a remarkably gifted observer. The observations recorded here in this paper were made in the service of the Pekin Syndicate (which has kindly given me permission to publish them), during the first months of 1898, among the coal- and iron-fields of southeastern Shansi. This is one of the largest anthracite-regions known, the area being

Jan 1, 1904

By Joseph A. Holmes, Henry Kreisinger

At the Mining Experiment Station of the U. S. Geological Survey, in Pittsburg, an investigation of the process of combustion is being carried on in a specially-designed furnace having an unusually long combustion-chamber. This work is conducted by a con~mittee consisti~lg of 11. Kreisinger, mechanical engineer; Dr. J. C. W. Frazer, chemist; and Dr..J. K. Clement, physicist. The problem, essentially one of physical chemistry, is estremely interesting to all who are concerned in the burning of coal or the construction of furnaces. The main object of these experiments is to ascertain the relation between the amount of' the volatile combustible driven from the coal and the combustion-spaces necessary to burn it completely. Our best steam-coals vary from 15 to 45 per cent. in volatile matter and from 40 to 75 per cent. of fixed combtistible. The greater part of the latter is burned on the grate: but the volatile combustible leaves the freshly-charsed coal and must be burned in the combustion-space. If this space is not large enough, the volatile combustible mill leave the furnace only partly burnecl, and the result will be a considerable heat-loss and a smoky stack. Strictly speaking, the factor which determines the completeness of combustion of the volatile matter, after it has been mixed with a certain amount of air, is the length of time the mixture is allowed to remain in the combustion-space; but this length of time depends on the extent of the space itself. Let us suppose, for instance, that, when a given coal is burned at a certain standard rate, the volume of the volatile combustible driven oft' per second is 10 cu. ft. Adding, say, 10 cu. ft. of air, the volume of the resulting burning mixture is increased to 20 cu. ft. If the combustion-space is 30 cu. ft., the burning mixture will stay in it,

Jan 1, 1911

By H. J. French

Within the past few years, particularly because of the rapid growth of the airplane industry during the war, considerable attention has been paid to the manufacture of light-wall cold-drawn seamless and welded steel tubing for structural purposes. While the manufacture of such tubing is not, in itself, a difficult matter, some difficulties have been encountered in producing the same under specifications requiring definite physical properties. It is the purpose of this paper to describe the methods of manufacture and the properties that may be obtained by such methods for tubing coming within about 1/2 to 2 in. (12.7 to 50.8 mm.) outside diameter and 10 to 22 Birmingham wire gage (0.134 to 0.028 in. wall thickness). Such tubing is largely used as structural material in the aircraft industry, and it is of the utmost importance that the physical and chemical properties should be known, and also that the various factors entering into the manufacture should be under such control as to allow these properties to be varied and held within definite limits. In general, tubing may be divided into four classes: namely, specialty tubing, such as riveted-sheet or plate, lock jointed, etc.; brazed tubing; welded tubing; and seamless tubing. Welded tubing may be divided into hot product, such as lap welded and butt welded, and cold product, such as acetylene and electric welded. Seamless tubing may be hot rolled or cold drawn. Specialty Tubing The first two classes present mainly mechanical or structural engineering problems. A simple form of tube is made by riveting together the overlapping edges of rolled sheets or plates formed into a cylinder. Because of the nature of its construction, such a tube is necessarily limited to relatively large sizes. Lock-jointed tubing is produced by passing low-carbon strip through a forming machine having suitable rolls and dies, its manufacture is almost entirely a question of design of the forming machine and its satisfactory operation. The chief application of such tubing is in the manufacture of bedsteads.

Jan 1, 1920

By L. D. Jaffe Hollomon, Hollomon John H.

For many steel parts it is desired to obtain the maximum toughness consistent with the strength required by the mechanical design. It is generally recognized that the greatest toughness at any given strength is found in steels having a tempered martensitic structure.' and is virtually independent of the composition of the steel2 (except for carbon). The choice of the composition of a steel for the parts in question should be based, therefore, on hardenability considerations and on manufacturing facility and economy. In a recent paper3 the concept of hardenability was discussed and a somewhat new approach to the problem was suggested. The hardenability was defined in terms of the cooling conditions (speed of cooling) required to avoid the pearlite and the bainite reactions. Since all the alloying elements do not have the same effects on the two reactions, the bainitic and pearl-itic hardenabilities must be considered separately. In order to design a steel for a given part, it is necessary to design a composition that has both sufficient pearlitic and sufficient bainitic hardenability. However, this requirement does not fix the combination of alloying elements to be used; an infinite number of steels would have the required hardenabilities. Other considerations limit the choice. For example, decreasing the carbon content increases the toughness at a given hardness, and for this reason low-carbon steels are often desired. Limitations or requirements of refining, casting, or forming practices often affect the level of some of the alloying elements. Price considerations enter. Frequently, however, it is very desirable to minimize the tendency toward quench-cracking while maintaining the necessary hardenability. This paper is concerned with suggesting a method for choosing compositions that will have the required hardenability together with minimum tendency toward quench-cracking. Quench Cracking Since only the case in which the entire part will transform to martensite in the particular quench employed is being considered, the analysis of the quench-cracking problem is somewhat simplified. Quench-cracking arises from the temperature gradients existing throughout the piece during cooling. Because of these temperature gradients, the contraction arising from the decreasing temperature and the expansion arising from the austenite-martensite reaction do not occur uniformly over the parts, and stresses are set up that tend to cause cracking. The temperature gradients can be reduced by decreasing the severity of quench. This, however, requires that the hardenability be correspondingly increased by increasing the carbon or alloy content. An

Jan 1, 1947

By Hollomon John H., L. D. Jaffe Hollomon

For many steel parts it is desired to obtain the maximum toughness consistent with the strength required by the mechanical design. It is generally recognized that the greatest toughness at any given strength is found in steels having a tempered martensitic structure.' and is virtually independent of the composition of the steel2 (except for carbon). The choice of the composition of a steel for the parts in question should be based, therefore, on hardenability considerations and on manufacturing facility and economy. In a recent paper3 the concept of hardenability was discussed and a somewhat new approach to the problem was suggested. The hardenability was defined in terms of the cooling conditions (speed of cooling) required to avoid the pearlite and the bainite reactions. Since all the alloying elements do not have the same effects on the two reactions, the bainitic and pearl-itic hardenabilities must be considered separately. In order to design a steel for a given part, it is necessary to design a composition that has both sufficient pearlitic and sufficient bainitic hardenability. However, this requirement does not fix the combination of alloying elements to be used; an infinite number of steels would have the required hardenabilities. Other considerations limit the choice. For example, decreasing the carbon content increases the toughness at a given hardness, and for this reason low-carbon steels are often desired. Limitations or requirements of refining, casting, or forming practices often affect the level of some of the alloying elements. Price considerations enter. Frequently, however, it is very desirable to minimize the tendency toward quench-cracking while maintaining the necessary hardenability. This paper is concerned with suggesting a method for choosing compositions that will have the required hardenability together with minimum tendency toward quench-cracking. Quench Cracking Since only the case in which the entire part will transform to martensite in the particular quench employed is being considered, the analysis of the quench-cracking problem is somewhat simplified. Quench-cracking arises from the temperature gradients existing throughout the piece during cooling. Because of these temperature gradients, the contraction arising from the decreasing temperature and the expansion arising from the austenite-martensite reaction do not occur uniformly over the parts, and stresses are set up that tend to cause cracking. The temperature gradients can be reduced by decreasing the severity of quench. This, however, requires that the hardenability be correspondingly increased by increasing the carbon or alloy content. An

Jan 1, 1947

By D. H. Baldwin, R. E. Reed-Hill

Six compositions of polycrystalline ZY-0 alloys, containing up to 4.2 at. pct 0, were tested in tension between 77° and 600° K. The data obtained from each of the compositions corresponded closely to a rela-ion between yield stress and absolute temperature of the form In s/so = BT, where oo is the yield stress extrapolated to zero degrees and B is a constant. In agreement with others who have observed this relationship, it is shown that the activation energy may be expressed as Ho In so/s. In the present specimens Ho is approximately 18,000 cal per mole and is apparently independent of temperature and composition inside the limits of the investigation. It is also demonstrated that this form of activation energy cowesponds to a strain rate sensitivity parameter RT/Ho. Oxygen was also noted to have an effect upon the operative deformation mechanisms. With increasing oxygen concentration there was an increased tendency to observe both nonbasal slip and cross-slip phenomena. Oxygen does not seriously inhibit twinning more than it does slip. Twins were observed in all specimens tested. It is becoming increasingly evident that interstitial atoms in solid solution are able to interact strongly with mobile dislocations. Stein, Low, and seybolt,&apos; have shown that, if the carbon concentration in bcc iron is lowered below the solubility limit, its flow stress temperature dependence is markedly reduced. This suggests that carbon atoms in interstitial solid solution may be responsible for the pronounced temperature dependence of the flow stress normally observed in iron. This view has recently been challenged by Leslie and sober2 who observed a strong flow stress temperature dependence in iron to which a trace of titanium had been added in order to remove carbon atoms from solution. Since the interstitial concentration must be reduced below approximately 1 ppm in order to produce a pronounced effect on the flow stress temperature dependence,&apos; studies of the effect of interstitials on the flow stress in iron necessarily involve serious experimental difficulties in alloy preparation. There are other metals, however, in which strong effects of interstitial solutes upon both the flow stress and its temperature dependence are observed. Of particular significance is zirconium which, according to Domagala and Mcpherson, 3 is capable of dissolving 28.6 at. pct O. The O-Zr alloy system is an almost ideal system for studying the interaction of interstitial atoms with deformation modes since it is possible to form alloys capable of study over an extensive range of compositions. Mills has made such a study using single crystals oriented primarily for single prismatic slip4 and has found an effect of oxygen concentration on the flow stress temperature dependence analogous to that observed in iron due to carbon by Stein, Low, and Seybolt. The present paper is specifically concerned with the effect of oxygen on deformation in polycrystalline zirconium. Although plastic flow in this type of specimen is much more complex than that reported for the single-crystal work, and involves both slip (on several different types of planes) and mechanical twinning, the results of this investigation are in general agreement with the single-crystal observations concerning the effect of oxygen on the temperature dependence of the flow stress. In addition, they also demonstrate that oxygen affects the acting deformation systems. This is in contrast to single-crystal results4 that showed only single slip on a prism plane. EXPERIMENTAL PROCEDURE Material. High-purity hot-rolled zirconium strip, 0.2 in. thick by 4 in. wide, of 0.10-mm average grain diameter, was used for forming alloys. It was obtained from the Carborundum Metals Co., Akron, N.Y., whose analysis indicated the major impurities were, in wt ppm: Hf, 540, C, 145; Fe, 100; and 0, <80. The plate texture was similar to a wire texture, with basal planes generally parallel to the rolling direction and basal poles randomly distributed about the rolling direction. The heat treatments described below did not appreciably alter the basic texture. specimen Preparation. Small threaded-end tensile specimens were machined from the plate with axes perpendicular to the rolling direction. These transverse specimens had gage sections 1 in. long by 0.060 in. in diam. The small gage section diameter was dictated by the fact that the alloys were formed by dif-

Jan 1, 1969

By W. F. Hosford, E. W. Kelley

By testing polycrystalline specimens from textured plates which had Previously been used to provide materials for growing single crystals, it has been possible to relate the plastic anisotropy of textured materials to the deformation behavior of single crystals. The deformation studies have been conducted at room temperature on textured polycrystalline magnesium and binary Mg-Th and Mg-Li alloys. Variously oriented specimens of the textured materials were deformed in plane-strain compression and in uniaxial tension and compression. The stress-strain curves are similar in their general jorm of anisotropy and stress levels to those obtained on single crystals of the same alloys. The degree of anisotropy is lower, however, in the polycrystalline materials and correlates with the intensity of the basal texture. Yield loci for the textured materials appear reasonable in terms of the deformation mechanisms, and deviate sharply from the form predicted by the Hill analysis for aniso-tropic material. A N earlier study1 of single crystals has shown that magnesium and magnesium alloys with thorium and with lithium deform at room temperature primarily by basal slip, {10i2) twinning, and (1011) banding. The (10i1) banding mode is a combination of {10ll) twinning followed by (1012) twinning and basal slip within the doubly twinned material.2, 3 Magnesium with lithium can also deform by {1010)(1210) prism slip.1&apos;4&apos;5 Still other deformation modes have been reported for magnesium6-11 but these are considered to play a minor role in room-temperature deformation. In a polycrystalline material, plastic deformation must occur in the individual grains through the operation of one or more of the various deformation modes. Because the critical shear stress for basal slip is very low compared to the activation stresses for the other deformation modes,&apos; basal slip accounts for much of the deformation in the polycrystalline aggregate. However, since there are only two mutually independent basal slip systems, and because five independent systems must be active for an arbitrary shape change in any material,&apos;&apos; modes other than basal slip must account for some of the strain. The deformation of textured magnesium, like that of other hcp metals, must be controlled by the same mechanisms observed in single crystals. In strongly textured material, the form of the anisotropy should be similar to that of single crystals, and the degree of anisotropy should depend on the intensity of the texture. EXPERIMENTAL PROCEDURE The anisotropy of deformation was investigated through the use of plane-strain compression tests, as well as uniaxial tension and compression tests. Materials. Test specimens were cut from the three textured plates of magnesium which had previously been used to provide material for single crystals.&apos; These plates, furnished by Dow Chemical Co., had been reduced about 80 pct during the process of being hot-rolled to their final 1/4-in. thicknesses. The plates had the three respective compositions, pure magnesium, Mg-0.5 wt pct Th (0.49 pct Th by spectro-graphic analysis), and Mg-4 wt pct Li (3.84 pct Li by chemical analysis). Impurities other than iron were less than 0.0005 pct Al, 0.01 pct Ca, 0.001 pct Cu, 0.0006 pct Mn, 0.001 pct Ni, 0.003 pct Pb, 0.001 pct Si, 0.001 pct Sn, and 0.01 pct Zn. Iron was 0.001 pct in the pure magnesium, 0.002 pct in the Mg-0.5 pct Th, and 0.014 pct in the Mg-4 pct Li. The textures of the three plates were determined by X-ray diffraction utilizing only the reflection technique out to an angle of 50 deg from the sheet normal. The resulting basal pole figures are presented in Figs. 1, 3, and 5. Grain sizes in the plates were ASTM number 4 in the pure magnesium and number 7 in each of the alloys. Plane-Strain Compression Tests. Plane-strain compression specimens approximately $ in. thick by 4 in. wide by $ in. long were prepared for each of the three compositions. These specimens were prepared in a manner similar to that used for the single-crystal specimens of the earlier study.&apos; All polycrystalline specimens were stress-relieved at 500°F for hr as the final step in their preparation for testing. The testing procedure was identical to that used for the single crystals, involving compression in a channel and using 2-mil Teflon film as a lubricant. The specimens were tested in six orientations of interest, these being the six combinations of the rolling, transverse, and thickness directions of the material serving as loading, extension, and constraint directions in the plane-strain compression test. Each of the six orientations was assigned a two-letter identifying code. These are combinations of the letters (thickness direction), R (rolling direction), and T (transverse direction) with the first letter signifying the loading direction and the second letter the extension direction. For example, ZR specimens were compressed in the thickness direction while extension was permitted to operate in the rolling direction of the textured material. To facilitate comparison of the present work with that of the single-crystal study1 the orientations used for single crystals are given in Table I along with the polycrystalline orientations that most nearly correspond. To insure reproducibility, at least three duplicate

Jan 1, 1969

By Howard Pyle

CORE analysis is a recent development in the field of petroleum technology. The earliest work on this subject was done in connection with evaluating and planning secondary oil recovery by water-flooding. Present-day analysis of sands of flush fields requires new and independent interpretations of the data provided by cored material. Particular attention is being paid to the development of rapid, routine methods for measuring physical characteristics of sandstone, such as permeability, porosity and grain size, as well as the sand&apos;s fluid content. Permeability may be defined as the fluid-passing capacity of a rock. For a sandstone to be permeable it must be possible to pass a measurable quantity of fluid through the material in a finite period of time. The common unit of permeability is the darcy, which may be defined as the rate of viscous flow, in milliliters per second, of a fluid of one centipoise viscosity through a porous medium having a cross section of one square centimeter, under a pressure gradient of one atmosphere (76.0 cm. Hg) per centimeter.1 For convenience the subunit millidarcy, or one-thou-sandth darcy, is often used. Porosity is defined as the fluid-containing capacity of a rock and is usually expressed as a percentage ratio of the total pore volume to the rock or bulk volume. Since measurement of only the effective or communicating pore volume is often made, porosities are distinguished as total or effective.2,3 Net effective porosity is defined as the net pore volume available for oil and gas. Oil and water content of sand is measured and expressed either as the percentage saturation of the total pores or of the bulk rock. The oil content may also be expressed as the percentage saturation of the net effective pores. In connection with water-flooding, methods of core analysis were developed to furnish data that could be used in determining the quantity of recoverable oil,4-6 and the probable rates at which various sands or divisions of a sand open to the wells would take water or produce oil. In flush fields, the analytical data are used to predict the productivity of a cored interval. They indicate the presence of oil, gas and water and may

Jan 1, 1939

By D. R. Uhlmann, T. P. Seward, O. Chalmers

A magnetic field has been used to damp out liquid convection during the solidification of castings. Ingots of Al-2 pct Cu were poured from various sperheats (10" to 65°C) into a room-temperature graphite mold located between the poles of an electromagnet. The effect on ingot structure of varying the strength and time of application of the magnetic field was investigated, and the results are interpreted in light 01- current theories of ingot structure. In the solidification of alloy systems, thermal gradients in the melt and differences in density of the constituents are expected to produce convective motion in the liquid. The thermal convection caused by temperature gradients should be present during the freezing of both alloys and pure materials, while the solute convection caused by density differences should be of concern only for alloys. The possible influence of this natural convection on the structure of castings has been discussed by Ruddle,&apos; Chalmers, and Tiller. More recently, an experimental investigation of such effects was carried out by Cole and Bolling. These workers took stationary molds containing lead- and tin-based alloys and. using a brine solution. quenched them from various superheats above their respective liquidus temperatures. When grids were placed across the mold diameter to suppress convection, the grid region was later observed to contain a larger percentage of columnar grains than other parts of the casting or than similar castings poured without the grids present. From thermocouple measurements, they found the temperature in the grid region to be higher than that in the region outside the grids throughout the freezing process, and concluded that convection should be an important mode of heat transfer in normal castings. In addition to such convection arising from thermal gradients or differences in density of the constituents, a further source of convective motion, which we shall call "momentum convection", may be particularly important in small (laboratory-size) castings. By this term we refer to the convective motion produced in the initial pouring process, a motion which is damped out as the linear momentum and angular momentum of the liquid are dissipated. Besides these sources of convection, which are present to some extent in all castings. external influences may also be effective in producing convective motion. Examples of such "forced" convection which have been discussed in the literature include stirring the melt, shaking the mold, rotating the mold, and so forth The purpose of the present study was to examine the effect of convection on the structure of castings poured into a cold mold. In this work, a magnetic field was employed to damp out the convective motions within the liquid, and hence control the extent of con- The effect of a magnetic field on convective currents in a conducting liquid is to induce eddy currents which oppose and damp out the convective motion. vection. The technique of magnetic damping was previously used by Utech and F1emings" in their study of convective effects on impurity banding and other substructure in alloy crystals grown unidirectionally from the melt. In their investigation, fields as small as 200 gauss were found to be effective in damping the convection currents which influence the banding. I) EXPERIMENTAL TECHNIQUE In the present study, alloys of A1-2 wt pct Cu were poured into a room-temperature graphite mold. The mold, in the shape of a circular cylinder, 2 in. ID, 2-3/4 in. OD, 5 in. inside height, and 5-1/2 in. outside

Jan 1, 1967

By M. C. Flemings, P. J. Ahearn

Dendvite morphology of unidirectionally solidified Sn-12 pct Bi alloy was determined with the aid of X-ray and macroetch techniques. Columnar growth direction (growth direction of primary arms) in this alloy is [110]; secondary arms grow in the [lii], [111), and [112] directions. Interstices between [112] dendrite arms fill in during early stages of solidification so that well-defined (110) planes are seen in the final structure (parallel to the heat-flozo direction). Similarly, interslices betweex the [111] secondary arrlls fill in to form (112) planes, and interstices between [1111 ] arms fill in to form (112) planes. DENDRITE morphology in alloys is conveniently studied in unidirectionally solidified castings. In this type of solidification, heat is extracted from a single chill surface of the casting while other surfaces are insulated. Solidification progresses from the chill and results in cast grains that are columnar with the long axis of the grain perpendicular to the chill. Dendrite morphology is conveniently studied by examination of etched surfaces parallel and perpendicular to the chill, as previously described.&apos;" Experimental studies on the growth direction for tin are in general agreement. The major growth direction is [110]:-&apos; although this is altered somewhat by supercooling. In one study, tin dendrites pulled from a supercooled melt had a growth orientation 12 deg away from the [110] direction toward the [002] direction.&apos; This orientation could be changed back to the [110] or close to the [110] direction by changing the tempera- ture gradient in the melt. In a study using autoradio-graphic techniques, (111) directions were shown to be directions of preferred growth in addition to the [110) direction.7 PROCEDURE The samples employed in this study were cut from 12 pct Bi-88 pct Sn castings, 1.5 in. in diam and 3.5 in. tall. The casting procedure consisted of heating the charge to 390°C and then pouring the molten alloy directly into a gypsum sleeve mounted on a massive copper chill. Specimens were cut from the ingot, mounted, polished, and etched with Taffs reagent [FeC13 .6H2O, 2 g; HC1, 5 cu cm;H20, 30 cu cm; CzHaOH (95 pct), 60 cu cm].&apos; The dendritic pattern was clearly visible after etching. Photomicrographs at about 8 and 35 times were taken on surfaces parallel and perpendicular to the chill. Laue back-reflection patterns were obtained from three different columnar grains in a singIe polished face 2 in. from the chill. The cut face was polished and positioned in the beam of a Laue camera, so that diffraction occurred from a single dendritic grain. The resulting diffraction pattern was interpreted to determine crystal log raphic orientation in relation to the heat-flow direction and in relation to microstruc-ture of the given grain. RESULTS Fig. 1 shows a horizontal and vertical section of the columnar structure, at low magnification. Light regions are rich in tin, and darker regions tin-poor; the primary phase is tin-rich a phase. The two sections shown were taken orthogonally from the same metallographic specimen. It is readily seen from Fig. 1 that the dendrites have

Jan 1, 1968