Search Documents

By H. Landsberg

In a previous report1 it was pointed out that a successful attack on roof troubles has to be preceded by extensive scouting. As Lord Kelvin once said, scientific progress can be made only if accurate data are available: "unless you measure, you do not know." The Convergence Recorder For the observation of roof movements in mines the convergence recorder has shown that it will enable us to get some of the necessary information. Results with convergence recorders were first published by Winstanley and other English investigators for rapidly moving longwall faces. In their investigations the speed of work and the heavy overburden produced a considerable amount of absolute values of convergence in a short time. Under the conditions frequently encountered in our investigations in Central Pennsylvania, under shallow, overburden and in mines with slowly proceeding extraction, the movements observed were much less in absolute value, for an equal interval of time. This mas partly because the mines in which our studies were carried on frequently had idle days, sometimes four or five in succession. Therefore continuous records were not employed and a simple convergence gauge was built. In its first models, it consisted only of two telescoping tubes pressed against roof and floor by a coil spring. At the side of the lower tube a rule divided into 1/2-mm. divisions mas fixed and a knife-edge, which was attached to the upper tube, mas slid over the scale in case of convergence between roof and floor. While the larger motions could be read on this device, it seemed to be desirable to increase the accuracy by inserting between the two tubes a dial meter reading in 1/1000 in. Such a gauge was first built in April 1937 and installed for experimental purposes in a bituminous coal mine in Pennsylvania (Fig. I). It was read at least once daily, 24 hr. apart, and if feasible at shorter intervals. After several months of experience it can be said that this type of gauge answers the scientific as well as the practical needs. It is easier to handle than the recorder; no clock is used, there are no pen troubles. The price of

Jan 1, 1938

By H. Landsberg

In a previous report1 it was pointed out that a successful attack on roof troubles has to be preceded by extensive scouting. As Lord Kelvin once said, scientific progress can be made only if accurate data are available: "unless you measure, you do not know." The Convergence Recorder For the observation of roof movements in mines the convergence recorder has shown that it will enable us to get some of the necessary information. Results with convergence recorders were first published by Winstanley and other English investigators for rapidly moving longwall faces. In their investigations the speed of work and the heavy overburden produced a considerable amount of absolute values of convergence in a short time. Under the conditions frequently encountered in our investigations in Central Pennsylvania, under shallow, overburden and in mines with slowly proceeding extraction, the movements observed were much less in absolute value, for an equal interval of time. This mas partly because the mines in which our studies were carried on frequently had idle days, sometimes four or five in succession. Therefore continuous records were not employed and a simple convergence gauge was built. In its first models, it consisted only of two telescoping tubes pressed against roof and floor by a coil spring. At the side of the lower tube a rule divided into 1/2-mm. divisions mas fixed and a knife-edge, which was attached to the upper tube, mas slid over the scale in case of convergence between roof and floor. While the larger motions could be read on this device, it seemed to be desirable to increase the accuracy by inserting between the two tubes a dial meter reading in 1/1000 in. Such a gauge was first built in April 1937 and installed for experimental purposes in a bituminous coal mine in Pennsylvania (Fig. I). It was read at least once daily, 24 hr. apart, and if feasible at shorter intervals. After several months of experience it can be said that this type of gauge answers the scientific as well as the practical needs. It is easier to handle than the recorder; no clock is used, there are no pen troubles. The price of

Jan 1, 1938

ZAY JEFFRIES (communication to the Secretary*).-Having seen Mr. Ruder's micrographs of electrolytic iron, I am of the opinion that the tentative explanation offered verbally is correct. Mr. Ruder has informed me that both of the samples were cooled in the furnace. The structures as shown in Figs. Band C resulted from the last cooling through the temperature range near 900° C. Assuming that the rate of cooling through this range was the same in both cases, the differences in struc-ture of the gamma iron in the two samples must have ]:)]-ought about, in some way, the variations in grain size and grain shape shown in Mr. Ruder's micrographs. Even though there is practically no temperature gradient in muffle-furnace treatment during the "soaking" period, during both heating and cooling, there is a temperature gradient. Fig. B should normally have been fine-grained prior to the last cooling, due to the comparatively low maximum temperature to which it was heated (1,000° C.). On cooling through the allotropic change point at 900°, these small gamma grains, iii conjunction with the temperature gradient, should form an ideal condition for germination. Germinant grains should form near the surface of the sample (the-colder portions) and the small gamma grains would be progressively absorbed as they changed into non-gamma iron. The elongated grains in Fig. B, converging toward the axis of the piece of iron, indicate that germinant grains first formed near tine surface and advanced their boundaries toward the interior of the sample. The gamma grains in Fig. C, however, should have been large, prior to the last cooling, due to time high temperature treatment (1,250 to 1,300° C.). In other words, to use one of Prof. Howe's expressions, the crystalline organization should be very complete and the change from gamma to non-gamma iron on cooling would take place reluctantly. This resistance to change from gamma to non-gamma iron would probably be greater in the interior of the large grains than at their boundaries. Non-gamma iron centers or nuclei would probably form at a great many places, at the grain boundaries, thus masking the influence, to a large

Jan 6, 1917

By Henry F. Adams, Guy H. Ruggles

In this paper the authors aim to chronicle the experience and salient points brought out in changing flotation reagents at a concentrator which had probably been using a minimum amount of oil at a minimum cost per ton, to a more complicated system requiring a partial chemical control. The original oils were coal tar and pine oil. The new reagents are lime, xanthate and pine oil. It was found that there were no insurmountable difficulties and eventually the cost of the new reagents per ton of ore proved to be very little more than that of the old. Lime Plant When the question of handling lime came up there were two propositions open: (1) to handle the lime dry; (2) to handle it wet in the form of an emulsion. Granting that a dry lime feeder would function properly, delivering lime uniformly, the chief objection was the dust that would be raised when these feeders were being charged or operated, as the only possible location was on a gallery beneath which men were working. With this objection the handling of lime as an emulsion seemed to be the better scheme. The lime plant which was first installed was for experimental work on one section. This was gradually changed and developed until it was of sufficient size to accommodate 20 sections. The various changes will not be discussed and the following description deals only with the fully developed plant. Crude as it is, and perhaps somewhat expensive to operate, the lime-handling plant has been quite successful. Much has been learned which will pave the way for a better installation in the future. Burnt lime is received loose in standard gage box cars. This is the product of the kilns and has had no screening or sorting. A grab sample is taken from each car as it is unloaded. An average of the analyses of samples from 44 cars gave the following: Available CaO Total CaO, Oxide and Hy- MgO, Fe²O³ + Al²O³, Insoluble, Per Cent. drate, Per Cent. Per Cent. Per Cent. Pek Cent. 88.3 79.2 1.6 ' 1.3 2.2

Jan 1, 1928

By N. K. Chen, R. Maddin

Single crystals of molybdenum were extended at temperatures from 1300° to 2500°C. It was found that with increasing temperatures, the yield becomes more pronounced and the number of slip bands for equal amounts of elongation decreases. Slip at high temperatures fragments the structure. OTHER than the investigations on sodium and potassium by Andrade and Tsien,&apos; the researches of Steijn and Brick&apos; on a iron single crystals at low temperatures are about the only studies of the influence of temperature on glide of body-centered cubic single crystals. The effect of test temperature on glide has been rather widely investigated with hexagonal crystals" and less widely with face-centered cubic crystals. ~~ a result of these studies it can be said that, in general, the onset of plastic flow as measured by the initial rate of strain hardening becomes more abrupt with increasing temperature, and the value of the yield decreases with increasing temperature. Strain hardening, however, is markedly affected by changes in temperature except at very low and very high temperatures where the strain hardening rate becames constant. In the present investigation it is shown that temperature affects the glide of molybdenum single crystals in much the same manner as crystals of other classes, it., for comparable strains the number of slip bands decreases with increasing temperature; shear along the slip bands increases with increasing temperature; the yield becomes more pronounced with increasing temperature of test; and the strain hardening approaches a constant at very high temperatures. In addition, it is shown that, in agreement with the work of Tsien and Chow, Qlip occurs on (110) planes in <Ill> directions. It is further shown that slip at high temperatures fragments the structure into either irregular sized cells or bent atomic planes which are roughly aligned in crystallographic directions. Experimental Procedure Single crystals 3 mm in diameter by about 25 mm long were prepared using the technique previously described.&apos; The furnace in which the crystals were grown served as the extension apparatus for the tension tests. It consisted of a 4 in. water-cooled brass tube 20 in. long which was continuously evacuated at the bottom. Two water-cooled copper electrodes held the specimen by means of spherical collets secured in place in the electrodes by set screws. These electrodes served also to transmit power and stress to the specimen. The lower electrode was clamped to a stand, while the upper electrode was fastened to one side of a lever arm flexibly supported at the top through a slightly offset pinion. A metal bellows operating elastically was attached to the upper electrode to affect a vacuum seal and allow freedom of motion. The level of the arm was adjusted by rotating a graduated nut. Rotation of the electrode was prevented by a key fitted into a groove. After the specimen was mounted and the vacuum secured, the lever arm was adjusted so that the bellows was at its relaxed position. This insured that the total weight of the specimen, the upper electrode, and the downpull of the vacuum were balanced by the horizontal beam. Since the specimen was heated by its own resistance, expansion of the specimen proceeded freely by this arrangement. During the time of heating the specimen, the beam was maintained in a horizontal position by turning the nut at the top. By graduating the lever arm and using a known dead weight on the lever arm to supply a tensile stress, the graduated nut could be read to 0.0001 in. extension. Since

Jan 1, 1955

By Clarence W. Dunham

BECAUSE of the earthquakes that occur at Chuquicamata, the design of the smelter stacks constituted the most difficult structural problem of the entire sulphide ore project. Slight tremors occur almost daily and shocks of moderate magnitude are not uncommon. Naturally, the operation of the smelter depends upon the safety of these stacks, and their resistance to earthquakes was the critical feature of their design. Adequate data of the magnitudes of past shocks at Chuquicamata were not available. However, considering the information that was obtained from experiences in other parts of Chile, a period of one to two seconds was adopted as a basis for the design. To complicate the problem further, the stacks had to provide for operations under a wide variety of conditions ranging from the possibility of running one reverberatory furnace and two converters initially to perhaps five or six furnaces and eight or ten converters simultaneously in the completed plant. No one could tell for certain just what the ultimate capacity might have to be because the plans permitted a large extension beyond the first installation if this became necessary. Studies of the stacks were made for many conditions. At first it was thought that one stack 600 or 650 ft high should be used initially for both the furnaces and converters, with a second similar stack to be built for the future extension. This height would provide adequate draft in the rarified atmosphere at the plant&apos;s elevation of 10,000 ft. It would also disperse the gases high in the air. Preliminary studies of this large stack showed that such a structure was possible if made of steel but it would be exceedingly costly. Furthermore, the effects of the tendency for the top to whip under the action of earthquakes might be serious, and the design had to be based upon assumptions which might not be trustworthy. Such a tall stack was finally abandoned in favor of a larger number of smaller ones. Initially, one stack will service the first three or four furnaces. Another will handle the gases from four or five converters. The smelter has been located in such a position that the prevailing winds carry the fumes away from the remainder of the plant. A height of 300 ft for the stacks was finally selected. The top diameter is approximately 24 ft 9 in. clear inside of the lining. The converter stack is located upon a hill alongside the smelter. This provides an effective increase in height because its base is approximately 66 ft above the yard level. The base of the reverberatory stack is at the latter elevation. Stacks made of reinforced concrete or of steel were investigated, and so were many shapes for them. As these studies progressed, the lightness of a steel structure, and the ductility of the metal itself, led to the decision to use steel for the main part of the stacks. The fact that serious damage to one of the stacks would cause the plant to shut down, caused special studies to be made of the stress conditions that might exist around the breeching which had to be nearly 15 ft wide and 40 ft or more high where it joined the stack. This height was necessary in order to provide adequate transition from the horizontal flow of the gases to the vertical direction without undue eddies. This opening constituted a serious source of weakness in the structure. If made with sufficiently strong reinforcement around its edges, there would be a hard spot in the structure that might cause trouble because of shaft vibrations.

Jan 1, 1952

By Harry L. Brown, Philip E. Armstrong

Young&apos;s modulus doto ore presented for W, Mo. Ta. V, Cr. Ni, Ti, and Zr as a function of temperature up to about 0.7 of the melting points. A plot of reduced temperature us reduced modulus produces a general correlation except for titanium and zirconium. Young&apos;s modudlus data for some representatiue commercial graphites are given up to 2400°C. All results were obtained from longitudinal resonance-frequency measzrrements of 4-in. long samples, corrected for simultaneously measured thermal expansion. Comparison of poly crystalline and single-crystal tungsten behavior indicates that all the observed modulus values are frequencv -dependent at the higher temperatures. STATIC measurements of elastic properties of materials at elevated temperatures are extremely difficult to make since the elastic behavior is obscured by relatively large first-stage creep effects. Dynamic methods which avoid this difficulty by utilizing the measurement of the resonance frequency of a simple vibrational mode have been described in the 1iterature.l-3 The authors have extended the operating temperature range of this type of measurement to above 2000°C and have described the equipment elsewhere.~ The Young&apos;s modulus data presented here were obtained with this equipment, using samples about 4 in. long and 1/4 in. diam, supported horizontally at the center and excited to the fundamental longitudinal resonance frequency. Young&apos;s modulus was calculated by the formula: E = 4f2f2p where E = Young&apos;s modulus, / = frequency, 1 = length, and p = density. Dilatometric data were obtained simultaneously by optical measurements of the change of length of the sample. For the metals tested, an attempt was made to obtain modulus values that would be representative of the pure, strain-free, randomly oriented material. All of the graphites studied exhibited a high degree of elastic anisotropy, while the method assumes an isotropic homogeneous material. However , when the values for Young&apos;s modulus obtained for AUC graphite were compared with those taken from static measurements at room temperature they were found to be only about 4 pet higher. This is excellent agreement considering the low precision of modulus calculations from stress-strain curves. The difficulty in using data of apparent Young&apos;s modulus for anisotropic materials arises when the attempt is made to use these data and shear-modulus data to obtain Poisson&apos;s ratio. The results are usually meaningless and sometimes absurd.&apos; RESULTS Table I lists the sources, impurity content, thermal history, and dilatometric constants of the metal samples that were investigated. All the metal samples were tested under a vacuum of 1 to 5 x 10-5 Torr. Where our dilatometric data agreed with previously published data, the table lists the previous values and the literature reference. Where no reference is given, the constants were determined from our dilatometric data. Table II presents the modulus data in units of millions of psi as a function of temperature in degrees centigrade. The numbers were obtained from curves fitted to the experimental data. For some types of calculations, such as those attempting to correlate creep data, the slope of the modulus curve is of interest, and this information also is reported in Table 11. It is always tempting to try to fit physical-property data into some general pattern and then use this pattern to predict the behavior of other similar materials. The general pattern for an elastic modulus of a metal seems to be a linear deoro- with increasing temperature Over the range between 0.1 and 0.4 of the melting temperature, then a progressive1y decreasing value up to the melting point. Metals appear to retain finite moduli

Jan 1, 1964

By A. Stanley, J. C. Mead

The MacIntyre Development of the National Lead Co. is located at Tahawus, N. Y. The operations involve the mining and concentrating of a titaniferous iron ore to produce an ilmenite concentrate and a magnetite concentrate. Construction of the MacIntyre plant was commenced during the summer of 1941,when world conditions threatened to cut off the supply of Indian ilmenite. An open pit mining operation was developed and the crushing and milling equipment put in operation in July 1942. A general description of the operation was given in the Adirondack Issue of Mining and Metallurgy for November 1943. The metallurgy of the mill operation was described by Mr. Frank R. Milliken,* Plant Manager, National Lead Company, MacIntyre Development, and presented at the AIME New York Meeting, February 1948. The magnetite concentrate produced in the milling operation was too fine (minus 20 mesh) to be used directly in iron blast furnace operation, and most of the magnetite had to be stockpiled in 1942 and 1943. In 1943, the Defense Plant Corp. built a Greenawalt sintering plant at Tahawus, N. Y., to put the magnetite concentrate in a more suitable form for use in the iron blast furnace. The Greenawalt sintering plant consists of three 10 by 25 ft sintering pans designed to produce 1800 gross tons of sinter per 24 hr. The vacuum to each pan is produced by two Greenawalt fans in series, pulling approximately 30,000 cu ft of air per minute at 50 in. water gauge vacuum. The plant started operation in August 1944. The present plant production averages 25 tons per operating pan hour (approximately 224 lb per operating hour per square foot of grate area) of plus 1 in. sinter. Raw feed to the plant consists of 61 pct magnetite, 4 pct anthracite coal culm, and 35 pct minus 1 in. return fines which are conveyed to a pug mill where the materials are mixed thoroughly and water added to give the mixture 5.5 to 6 pct moisture. The mixed prepared feed is conveyed to two 4 by 10 ft vibrating screens where the minus 1 in. plus 5/8 in. return fines are screened out and discharged into a surge bin for use as a hearth layer. The minus % in. prepared feed is discharged into another surge bin for use as prepared feed. A charge car, electrically operated, having a capacity of one charge of prepared feed and several charges of hearth layer, lays a thin layer of plus 5/8 in. return fines and 9 1/2 in. depth of prepared feed into the pans. A fluffing roll and a vibrator on the car fluffs and spreads the prepared feed into the pans. An ignition car, electrically operated, ignites the top of the bed with a 30 sec flash burn. The 9 1/2 in. bed sinters in approximately 13 min. Dumping the pan, and recharging and igniting the bed requires 2 min. To improve the quality of the ilmenite concentrate produced in the mill and to reduce the amount of titanium dioxide lost in the mill tailings and in the magnetite product, extensive research work and pilot plant operations have been done on grinding the crude ore to minus 65 mesh size (rather than to minus 20 mesh) and concentrating it by a combination of magnetic separation (for magnetite recovery) and flotation (for ilmenite recovery). These tests have proved successful in increasing ilmenite recovery and grade. With the development of the ilmenite flotation process to a stage where a full scale flotation plant was in the design stage, the problem arose of handling the 65 mesh magnetite concentrate that would be produced. In order to study and solve the problems of handling and sintering the 65 mesh magnetite in the sinter plant, a pilot sinter plant was plus from John E. Greenawalt. The effect of using 65 mesh magnetite in the sintering operations was then studied on the 2.4 sq ft test pan, operating under conditions as similar to the large plant as could be set up in the laboratory. A series of tests were run in the test pan on present sinter plant feed that had been mixed in the plant pug mill. An average production and an average quality of sinter produced in this series

Jan 1, 1950

By Stewart L. Toleman, Robert H. Hafner, Irvin R. Kramer

In his paper on the calculation of harden-ability from chemical composition, Gross-mannl discussed the effect of most of the alloying elements used commercially. The purpose of the work reported in this paper was to determine the effect of several other elements on hardenability—arsenic, antimony, beryllium, cobalt, columbium, germanium, tellurium, tin, aluminum, and titanium—and to extend the range of composition of some of the elements studied by Grossmann—chromium, copper, manganese, molybdenum, nickel and silicon. Experimental Methods To determine the effect on hardenability, suitable amounts of the alloying elements were added to experimental heats and the hardenability determined by means of end-quenched hardenability specimens. The steels were melted in a high-frequency induction furnace with a basic crucible, using ingot iron as a base for some of the heats and S.A.E. 1015 for others. The alloying additions were made as ferroalloys or as metal, depending on the alloying element. Hundred-pound heats were split and poured into square, tapered, cast-iron ingot molds with hot tops. Aluminum was not used as a deoxidizer in most of the heats. The ingots were homogenized for 12 hr. at 1260°C. (23oo°F.) and forged into rounds of I½ -in. diameter. These bars were normalized twice from 840°C. (I55o°F.) before machining into Jominy bars. mined in most Cases by samples taken from the end-quench hardenability spedmen. AS suggested by Crafts,2 acid-soluble (8

Jan 1, 1944

By Robert H. Hafner, Irvin R. Kramer, Stewart L. Toleman

In his paper on the calculation of harden-ability from chemical composition, Gross-mannl discussed the effect of most of the alloying elements used commercially. The purpose of the work reported in this paper was to determine the effect of several other elements on hardenability—arsenic, antimony, beryllium, cobalt, columbium, germanium, tellurium, tin, aluminum, and titanium—and to extend the range of composition of some of the elements studied by Grossmann—chromium, copper, manganese, molybdenum, nickel and silicon. Experimental Methods To determine the effect on hardenability, suitable amounts of the alloying elements were added to experimental heats and the hardenability determined by means of end-quenched hardenability specimens. The steels were melted in a high-frequency induction furnace with a basic crucible, using ingot iron as a base for some of the heats and S.A.E. 1015 for others. The alloying additions were made as ferroalloys or as metal, depending on the alloying element. Hundred-pound heats were split and poured into square, tapered, cast-iron ingot molds with hot tops. Aluminum was not used as a deoxidizer in most of the heats. The ingots were homogenized for 12 hr. at 1260°C. (23oo°F.) and forged into rounds of I½ -in. diameter. These bars were normalized twice from 840°C. (I55o°F.) before machining into Jominy bars. mined in most Cases by samples taken from the end-quench hardenability spedmen. AS suggested by Crafts,2 acid-soluble (8

Jan 1, 1944

By C. G. Dunn

This note describes a method for revealing micro-structures in tantalum through an {hkl} effect which was found during a study involving amorphous and crystalline tantalum oxides. Three steps are involved. First, an amorphous film of Ta2O5 is formed anodically1 on the surfaces of the tantalum. The amount needed depents on the thickness of the substrate tantalum; 1600Å of oxide, however, is generally satisfactory in the 1/2 -mil (12 µ) to 3-mil thickness range. The film at this point is uniform in color. Second, the anodized specimen is heated to 800°C in. vacuo during a period of a few minutes and held at temperature for 5 min. During such a treatment some oxygen leaves the oxide through dissolution into the substrate tantalum (e.g., at 10-8 Torr oxide films thinner than about 800 completely disappear on 5-mil strip). Considerable crystallization of the amorphous oxide also occurs adjacent to the metal/oxide interface but not throughout the oxide thickness. The thickness of oxide needed as a residue is not too critical; values between 500 and 1000Å (optical estimate&apos;) may be most useful. (The presence of a residual oxide layer after the heat treatment usually is not apparent; in fact, in most instances the surfaces have a metallic appearance. This can be the case also for thicker residual films needed in the detection of a crystalline oxide phase by surface X-ray diffraction—e.g., if the initial oxide film is 3000Å thick, enough crystalline oxide is formed for X-ray detection.) The third step eliminates the metallic appearance at the surface and reveals (or produces) a varied colored film of tantalum oxide. Two methods can be used and both will be illustrated. If the specimen is dipped in 48 pct HF for a few seconds, the tantalum is found to be covered with a multicolored oxide. Moreover the colors correlate with the grain structure of the substrate tantalum through an orientation dependence of the type illustrated in Fig. 1, where results of an orientation analysis by the Laue X-ray method have been plotted. Other film conditions would have provided a different set of colors for the same orientations. Any such correlation, however, provides a basis for a qualitative assessment of the distribution of orientations in a large sample. The cold-rolled structure of tantalum foil produced by a recrystallization anneal and a cold-rolling reduction of 95 pct is not easily obtained by usual metal-lographic methods.&apos; The structure, however, is easily revealed by the present technique, Fig. 2. The alternative third step is to reanodize the specimen. The optical nature of the final anodic film depends on the presence of the crystalline oxide phase; color variations indicate optical thickness variations in the film. As the reanodization voltage is increased from zero, straw and light brown colors appear (as usual), followed now by variations in color from grain to grain depending on {hkl} orientation. Suitable end points, which are determined by voltage and time, are easily established. Fig. 3, for example, shows the grain structure developed in 5-mil tantalum strip during a 30-min re-crystallization and grap-growth anneal at 1800°C. An anodic film of 1600Å thickness was added prior to the special 800°C anneal. Reanodization was done at constant current density (near 0.2 ma per sq cm) in an aqueous solution of H3PO4 (0.01 pct) and was terminated after the initial brown colors were replaced by a deep blue at approximately 30 v. Although good grain contrast can be obtained with bright field illumination, even greater contrast for black and white micrographs may be obtained with polarized light, as in Fig. 3.

Jan 1, 1967

By G. S. Cole, H. Biloni, G. F. Bolling

An experimental investigation of sovlze low .melting point alloys sJtows that a substvucture of isolated depressions can be the first manvestation of constitutional supercooling on solid-liquid interjaces veuealed by decanting. Electron-tni cvop vobe and wletallo gvaplic esanzinations, in tlze bulk belzind the interjace, oj the segregation associated with these isolated areas substantiate tlzei&apos;v depressed nature, since a solute of ko < 1 is enriched, and a solute of ko > 1 depleted. In contrast, the pox structuve, a set of projections often veported in the literature, leaves no trace oj. segvegation. These obserl;atims, accovlrpanied by a brief review of recent literature, point to inconsistencies between experirrental obsevvation and the idea that the fornzation of a projection is a causal step in the development of a cellular substructure. An argument is presented to show instead how it is plausible for substantial depvessiom to form in the pvesence of constitutional supercooling at dislocations threading the solid-liquid interjace. THE development of constitutional supercooling during growth from the melt leads to the formation of the cellular solidification substructure. This well-founded association between structure and instability has been basic in understanding cellular substructure and micro segregation; however, the initial formation of structure seems unclear. Rutter and Chalmers,&apos; in definitive experiments and theory, noted that in the presence of constitutional a planar interface might break down: "resulting in the formation of a small projection on an initially plane or uniformly curved interface." That is, the breakdown from a planar to a cellular interface was implied to be initiated via a projection into the unstable liquid. Later, Walton et (11. found that a structure of isolated projections, termed "pox", appeared at solid-liquid interfaces decanted under growth conditions near the onset of constitutional supercooling; the pox were taken as the indication of the instability promoted by the supercooling. Tiller and Rutter4 in their extensive work studied the shape transitions at decanted interfaces which were generally observed to proceed as— pox, "irregular cells", elongated cells, regular (hexagonal) cells, and so forth. The pox varied in size from lo-&apos; to 1CT4 cm, and tended to disappear as cells increased in number and regularity, but as noted,4 the first real array of cells did not seem to be a development from the pox. In fact these authors implied a lack of connection because they stated that the pox are denser on "irregular cells", and as cell boundaries increase in number (i.e., the cells become smaller) there is less need for the pox which do dis- appear. Thereafter, most authors dealing with either experiment or theory have accepted the reality of pox and have used them as a criterion for the onset of constitutional supercooling. In contrast, Spittle, Hunt, and smiths have now suggested that pox are irrelevant artifacts comprised of such things as entrapped oxide. This proposal invokes the observations of weinberg6 and chadwick7 each of whom have shown that the act of decanting leaves a residual liquid on a decanted interface; the remnant solid layer of the order 10 p may thus contain particles that might have been transported from the external surfaces, or elsewhere, during decanting. With the incentive of this suggestion,= some further experiments and a reexamination of the literature have been conducted, in order to question the validity of pox as evidence of an instability and to examine the initial development of the cellular substructure. 1) EXPERIMENTS Single crystals of zone-refined tin (-99.9999 pct) were grown from the melt in a controlled fashion with various, small concentration additions of lead and antimony, for which ko < 1 and > 1, respectively. The crystals were decanted at conditions near the onset of constitutional supercooling and were thus appropriate for observation of slight perturbations. It was possible to observe two types of small departure from smooth or "planar" interfaces in both cases of lead or antimony additions. Some were projections and others, if in regular array of any type, were depressions. The crystals were etched with suitable reagents progressively dissolving the decanted interface surface; projections left no record, but depressions were continuously associated with spotlike areas contrasting with the rest of the interface. Traverses were made with the beam of an electron microprobe across the regions of contrast; with lead addition the persistent spots were lead-rich, and with antimony addition the persistent spots were antimony-poor. This is consistent only with a dominant role for depressions, because if the projections had left spots but were incorrectly catalogued, a reversed observation should have been made; that is, the Pb(ko < 1) should have been depleted and the Sb(ko > 1) enriched. In the work of Cole and inegard, and elewhere, regular arrays of structure associated with the initial stage of instability have been shown, in photographs and represented as pox or projections. We believe this to be erroneous, by inference, since whenever a regular array was observed, in the present examination, it consisted of depressions, regardless of the nature of the solute, ko 1. Fig. 1 is reproduced8 as an ideal example of the possible optical illusion involved; the observer can satisfy himself from the distribution of illuminated areas that the markings are depressions. Fig. 2 from the present investigation is an interference photograph of an interface similar to that in Fig.

Jan 1, 1967

By W. Bonfield

The microstrain characteristics of a polycrystal-line Cu 1.9 wt pet Be precipitation-hardening alloy have been determined for various conditions of aging. The friction stress remained constant for all the conditions investigated, whereas the microscopic yield stress (the stress to produce a plastic strain of 2 x 10-8 in. per in.) and the three-stage stress-strain curve in the microstrain region were sensitive to changes in dislocation and precipitate distribution. Correlations between the measurements of microplasticity and electron-nzicroscope observations of substructure are considered. ALTHOUGH the macroscopic mechanical properties of Cu 1.5 to 2.0 wt pet Be precipitation-harden ing alloys were established&apos; in some detail, there has been no previous investigation of the nature of microyield-ing in these alloys. This paper describes a high-sensitivity extensometer determination of microplasticity in polycrystalline Cu 1.9 wt pet Be, in which the friction stress, the microscopic yield stress (the stress to produce a plastic strain of 2 x 10-6 in. per in.), and the rate of strain hardening in the micro-strain region were measured for various conditions of precipitation. The structural changes accompanying aging in this alloy were examined using transmission electron microscopy, a study which differed from previous investigations as, in order to minimize grain boundary precipitation effects,&apos; the solution-treated alloy was cold-rolled to 40 pet reduction prior to aging. Hence the extent of recovery and recrystalliza-tion, as well as the variation of precipitate morphology and distribution, were assessed. From these results possible correlations between the microstrain characteristics and the observed precipitate and dislocation structure are considered. EXPERIMENTAL PROCEDURE The material investigated was a commercial copper beryllium alloy (Berylco 25), which had a com- position of 1.9 wt pet Be and 0.2 wt pet Co. The alloy was solution-treated at 800°C, quenched in water, and then cold-rolled to 40 pct reduction. Tensile specimens of gage length 1 in. and rectangular cross section of 0.18 by 0.06 in. were prepared from the solution-treated, cold-rolled material and aged for 15 min, 2, 24, and 100 hr at 315°C and 24 hr at 425°C to produce a range of precipitate structure. The hardness values associated with these conditions are listed in Table I. It can be seen that a maximum value is obtained after 2 hr at 315oC, which decreases with continued time at temperature to a minimum after 24 hr at 425°C. For comparison some as-solution-treated specimens were also aged for 2 hr at 315°C. The specimens heat-treated to a given condition were examined in two ways. First, the nature and distribution of the precipitate and dislocation structure was characterized using transmission electron microscopy. Thin foils were obtained from the specimens by electrolytic polishing in a 30 pet nitric acid-alcohol solution at -20oC, and were examined in an RCA EMU 3 electron microscope. Second, the mi-croplastic behavior of the specimens was measured with a Tuckerman strain gage, using the load-unload technique previously described2, 3 to determine the friction stress, the microscopic yield stress, and the variation of plastic microstrain with stress. RESULTS 1) Structural Changes During Aging. a) Annealing Processes. The solution-treated, cold-rolled Cu 1.9 wt pet Be had an irregular dislocation-cell structure,

Jan 1, 1968

By DR. DOUGLAS

Discussion of the Paper of Dr. Douglas, presented at the Toronto Meeting of the Institute, July, 1907 (Trans., xxxviii., 455 to 471). EDGAR HALL, Silverspur, Queensland, Australia (communication to the Secretary*) :-Dr. Douglas has written on this subject before, and his influence has had a powerful effect on the side of freedom among the younger generation of engineers. Moreover, it is not the first time that he has attributed the decline of the copper-smelting industry in Swansea to the secrecy maintained by the firms there engaged in smelting-operations. In this latter statement I think his conclusions are open to criticism. Whether the firms referred to have suffered by their secrecy is their own business-I. bold no brief for them ; but that the decline of the copper-industry at Swansea was inevitable seems to me to be proved conclusively by Dr. Douglas&apos;s own writings. In his paper on The Copper Situation,1 Dr. Douglas says "In comparing iron and copper mining, . . . it must be remembered that 2 tons of average iron ore from the most prolific source now available will make 1 ton of metal; whereas from 33 to 75 tons (say an average of 50 tons) of copper ore must be mined to produce 1 ton of copper." And further: "Last year&apos;s production of iron was made from approximately 50,000,000 tons of ore. Our copper mines, to yield a production of 900,000,000 pounds, must have handled approximately 22,000,000 tons of ore, or nearly half the quantity raised from our iron mines." Is not this the key to the whole situation ? In transporting the 50,000,000 tons of iron-ore, 25,000,000 tons of the metal iron were carried so much nearer to the market, but the transportation of 22,000,000 tons of copper-ore would have carried only 450,000 tons of the metal copper nearer to its ultimate destination. The small percentage of copper available in its ores makes

Sep 1, 1908

By Robert J. Linney

IN the latter part of the year 1943, it was decided to experiment with diamond-drill blast holes in the Old Bed magnetite mine at the Mineville mines of the Republic Steel Corporation, in sections of the ore body where vertical dimensions were large and where development for sublevel bench stopes had already been done. Other possibilities of application for this drilling method were in the reclamation of old floors and pillars in the pitching folds of the Lower Old Bed ore body and in the reclamation of large vertical pillars in the " 21 " Bonanza-Joker ore body. The cross sections and views of the two ore bodies will show the conditions to which the diamond-drill method has been applied. The Lower Old Bed magnetite ore body is lenticular and dips approximately 30° toward the southwest and strikes generally southeast and northwest. An intensely folded structure, which pitches generally on an axis approximately at right angles to the strike, is continuous from the uppermost old workings down to the present bottom of the mine, and probably continues with depth. On successively lower levels this folded structure becomes greater in vertical dimensions and the two folds are closer together in a horizontal dimension. As shown in Fig. 1, this folded structure gives to parts of the ore body considerable vertical dimensions, which provide areas that were developed for sublevel bench stoping above a slushing drift, as shown in Fig. 2. It was in one of these previously developed sublevel bench stopes, No. 26 on the 1185-ft. level, that the diamond-drill blast-hole method was applied for mining the upper sublevel. The lower sublevel was underhand-bench-drilled to the finger raises of the scram drift below. The roof of this stoping area began to break and spall on the lower sublevel, causing the roof to become inclined. Along the hanging wall of the stope this reached an elevation about half way between the two sublevels. A smooth schistose seam in the hanging wall causes the ore to break away freely. Therefore, if bench mining had been carried on in the upper sublevel, a dangerous condition of poorly supported benches would have resulted. When the drillers were slashing across the sublevel to footwall and hanging wall to make a bench, spalling roof of the opening below would probably have carried away part of the bench, and would have left a dangerous place in which to continue underhand benching. A 6 by 8-ft. raise had been driven between the lower stope and the upper sublevel about 200 ft. from a manway. It was decided to use this raise for a starting cut and to arrange holes as shown in Fig. 3, so that a slot would be opened across the ore body between the footwall and hanging wall. This slot would then be used for the purpose of breaking into the ore; by blasting vertical rings of holes drilled at right angles to the axis of the pitching folds as nearly as possible. Layouts of this slot drilling and the rings adjacent are

Jan 1, 1945

By Frederick Laist

I AM APPRECIATIVE of the honor you have done me in electing me to membership in your Society. I value the contacts with men of imagination and ideals which this implies. I am grateful for the recognition of such small contributions as I may have made, or helped to make, to the vast fund of scientific and engineering knowledge. We like to think, as we grow older, that our lives have not been purely parasitical, and that through our efforts some forward step, however small, has been taken toward improving conditions under which we live and do our work. In these days of industrial depression, we hear much criticism of our "machine age." Modern engineering, mass production, the complexity of our lives, all come in for some share of blame. The farmer is said to have been spoiled by the tractor and the gang plow, the factory worker has become a slave of the assembly conveyor, the scientific worker is no longer free but has sacrificed much of his individuality to the research organization of which he is a part. We wonder whether our work as engineers has been worth while and whether our striving after more efficient ways of doing things has been a curse to mankind rather than the boon we thought we were conferring.

Jan 1, 1932

By R. M. S. B. Horta, W. T. Roberts, D. V. Wilson

Evaluation of results obtained by the Harris method for inverse pole figures is discussed. Two existing analyses and a new approach are compared. In the most frequently used analysis, different reflections are accorded equal weight. A second method involves area-weighting of reflections, mainly to take account of nonuniformity of Pole distribution. In the new method, reflections are weighted according to their multiplicity factors. Intensity ratios obtained from a sample of steel sheet by the three methods are compared. INVERSE pole figures offer a convenient method of depicting the proportions of material with various orientations referred to a unique specimen axis. The technique was first applied to fiber textures, but it is now frequently used as a description of texture in sheet metal, the unique axis in this case usually being the sheet normal. The Harris method&apos; for the determination of inverse pole figures has the great merit of simplicity. It suffers certain intrinsic limitations, but provided that these are borne in mind, the results allow useful conclusions to be drawn regarding the effects of texture components on certain mechanical properties. Much thought has been given to alternative methods of texture description, aimed at eliminating the ambiguity in the simpler methods.2"6 Refinements in the method of description are obtained at the price of increasing complexity, and it seems clear that a simple method, such as that of Harris, will continue to find application. The original derivation by Harris1 has been corrected by Morris7 and later by Mueller, Chernock, and Beck.2 Since the latter reference is more accessible, it is referred to more frequently than the work of Morris. Most users of the inverse pole figure method present their results on the basis of the treatment by Mueller et al., and it is the purpose of the present communication to comment on this treatment and to suggest a simple modification to the method of presentation which enhances the meaningfulness of the results. It will be convenient first to summarize the Mueller analysis as follows: The intensity Ihkl of a hkl reflection from a textured specimen is: Ihkl=CI0AL\Fhkl\2NhklPhkl [1] where C is a constant for a given sample I, is the intensity of the incident beam A is an absorption factor. With usual diffrac-tometer geometry and a flat specimen, A is inversely proportional to the density of the specimen. L is the Lorenz polarization factor Fhkl is the structure factor for the hkl reflection Nhkl is the multiplicity factor phkl is the fraction of crystals in the polycrystal-line aggregate with any particular (nkl) plane parallel to the surface. The corresponding equation for a specimen with randomly oriented grains is lR,hkl=CRl°ARL\fnkl\2Nnklk [2] the subscripts R indicating the factors that are different for the random sample, which will, in general, have a density different from that of the textured one. The intensity ratio is hkl , c A Phkl [3] IR,hkl CR AR PR The constants are eliminated by summing over all the measured reflections ^iRMi °R AR PR ljPkkl and from Eqs. [3] and [4] T IR,hkl The only unknown in Eq. [5] is Yj phkl and before this can be evaluated, it is necessary to adopt some form of normalizing procedure. Mueller et al. assume that when a large number, n, of reflections is used, the average value of p as defined by Eq. [6] below will be unity ? = £j**l3l [6] and the final result of their analysis follows: hkl Pkkl = i I&Jf~ [7] ±y* Ihkl ^ in,hki The normalizing procedure used by Mueller et al. involves an unrealistic assumption since it gives equal weight to each of the hkl reflections. Other normalizing procedures can now be examined with a view to selecting a more appropriate one. For an infinite number of reflections, the function p can be averaged over a continuous range of orientations covering the complete solid angle 4p by the integral relation: p =1 jp(a)dQ = l [8] This is the only exact procedure, but in practice a

Jan 1, 1970

By S. F. Reiter

The paper presents isothermal recrystallization curves for 0.08 and 0.15 pct C steel at subcritical temperatures following small amounts of plastic deformation. The effects of deformation, temperature, and aging on nucleation and growth rates ore described. The free energy of activation for grain boundary migration in steel is given. SEVERAL excellent reviews of the literature have appeared concerning the recrystallization of metals.&apos;-&apos; The present investigation follows the approach advanced by Mehl, Stanley, and Anderson,6-7 in which the rate of recrystallization was analyzed in terms of N, the rate of nucleation, and G, the rate of growth of recrystallization nuclei. Two lots of low carbon, capped steel of the analysis given in Table I were studied. Each lot consisted of a 150 lb coil which had been hot rolled to 0.083 in. and then cold rolled to 0.042 in. at the mill. Strips 0.930 in. wide were sheared perpendicular to the rolling direction. Both steels were normalized before studying their recrystallization characteristics. The strips were cleaned, painted with a magnesia-acetone paste, and made into packs of equal weight, wrapped in 0.002 in. copper foil. The packs were placed in a salt bath at 900°C for 30 min and air cooled. A relief anneal followed in a second salt bath for 15 min at 650°C. The relief anneal was found necessary from early tests in which a longer incubation period and slower rate of recrystallization were observed in relief-annealed lot A steel than in similar material which was strained and recrystallized directly after being normalized. This effect, which indicates the presence of transformation and/or cooling stresses in steel air cooled from above the A, temperature, has also been observed by Samuels8 and Masing.9 Figs. 1 and 2 show the microstructure of lot A and B materials and illustrate the rather uniform No. 8 ASTM grain size produced by this heat treatment. Winlock and Leiter10 observed that strip specimens which had their sharp edges removed elongated more uniformly than those which were not polished. Similarly, when the sheared edges were removed on a belt grinder, it was found in the present investigation that such samples recrystallized more uniformly than did unpolished strips. Therefore, all strips were carefully rounded prior to their extension. The approximate strain limits for the production of large recrystallized grains are from 6 to 12 pct extension." It was found that for the purpose of this investigation, 8 and 9 pct elongation were suitable deformations. The strain rate employed was 0.01 in. per in. per min and produced a yield point elongation of 4 pct. Winlock and Leiter found that mild steel of No. 8 ASTM grain size gave the same yield point elongation when extended at 0.012 in. per in. per min. All of the lot A and B strips extended in tension developed a straight, stretcher strain line at each grip when the upper yield point was reached. The lines were parallel and made an angle of 55" with the edge of the strip. They approached each other with increasing strain and met near the center of the sample at the end of the yield point elongation. Immediately thereafter, a small drop in load was observed and then the load increased in a regular manner with increasing extension. The grips were initially 8 in. apart. After extension, the 6 in. gage length was carefully cut into 1 in. samples. The remainder of the strip was discarded. After a flash pickle in hot 50-50 hydrochloric acid, six samples, each of which had been taken from a different strip, were placed in a basket and submerged in a lead pot for isothermal recrystallization. Although no recovery effect was observed, strain aging did occur after extension. Therefore, samples were always recrystallized within 24 hr after their cold deformation. After recrystallization, the samples were etched with a solution comprised of one part by volume of nitric acid with three parts of water. Bromide printing paper was exposed directly at low magnifications and later used with a mask to measure the desired quantities. First, the average diameter of the largest grain visible in each sample was determined using dividers. Next, the number of recrystallized grains per unit area was counted and recorded as n. Then, for each sample, the combined area of the recrystallized grains was measured by transcribing the grain outlines to standard graph paper. Many determinations of the area of the recrystallized grains were repeated five times and indicated a standard error that was not greater than 25 pct. The average area for six samples was divided by the area of the mask to yield the percentage recrystallized. Recrystallization of 0.08 Pct C Steel The progress of recrystallization at 670°C after 8 pct elongation of lot A steel is shown in Fig. 3, a through f. The shapes of the growing crystals are approximately equiaxed, as is assumed in the

Jan 1, 1953

By AIME AIME

L. C. GRATON, professor of geology in Harvard University, addressed the New York Section on April 24 on-his impressions of the Rand. His beautifully clear and concise address was delivered without notes, so that what follows is merely a resume of the principal points made. The world is apparently coming to the end of ore discoveries easily made, yet we need metals at a steadily increasing rate. If surface discoveries are to decline, then we must find other ores or use less metals. The probable chances of finding ore are greater in the centers of big production than in new districts, as proved statistically. It is unsafe to say that a field is worked out. Therefore, deep mining holds possibilities and is an interesting study that will progressively gain in importance. The origin of the gold in the banket of the Rand has been a geologic football for a long time. Of the various theories, two have survived: 1. Infiltration into permeable conglomerate beds from deep-seated sources; 2. the placer hypothesis, which holds that gravel beds originally had the gold in them. At present, the second theory is accepted by the majority, as a result of the studies by the Union Geological Survey and by E: F. Mellor which were published about fifteen years ago.

Jan 1, 1929

By C. B. Murray

Our experience from time immemorial has been that the furnace sampler and analyst usually find one or two, and sometimes more, points less iron than the Lake Superior shippers, but, fortunately, their contracts are iron bound…

Jan 1, 1915