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By A. B. Kinzel

Precise knowledge regarding the effect of heat treatment on the properties of steel has made possible the detailed specifications and instructions covering optimum heat-treating temperatures and practices that are in current use. A distinct contrast is presented by the metallurgical treatment of steel adjacent to a fusion weld, as such steel is subjected to each temperature from room temperature to fusion temperature, and cooled at a rate that is not generally controllable but is predetermined by the nature of the assembly to be welded, the kind of welding used, and the surrounding conditions. This is true regardless of the type of fusion welding: oxyacetylene, electric arc, thermit or flash resistance. Therefore it seemed desirable to investigate the effect of this metallurgical treatment on the characteristics of carbon steels commonly used for welding, by a detailed study of metal subjected to each temperature range; i.e., each heat-affected zone. Oxyacetylene welding was chosen for the investigation because of the experimental facility of accurately segregating and studying each temperature zone. The nature of the zones produced by other types of welding is the same. The difference is primarily a matter of dimensions of each of the temperature zones involved. The advantages and disadvantages of the extent of the zone are of prime moment, and are discussed after the presentation of the detailed zone study. No mention is made of the fused metal proper, as this has been the subject of much published research and the nature of the solidified metal is fairly .ell known. General Method The scheme of procedure in the work herein reported involved the testing of the metal of each temperature zone adjacent to the weld in so

Jan 1, 1935

By Voyle R. McFarland, Robert A. Burmeister, David A. Stevenson

The distribution of lead between phases in the Ag-Sb-Te system was studied using microautoradio -graphy. Two compositions were investigated, both containing an intermediate phase Known as silver antimony telluride as the major phase, and one containing AgzTe and the other SbzTes as the minor phase. For both compositions, two thermal treatments were used: nonequilibrium solidification from the melt and long equilibration anneals of the as-solidified structure. For each composition, lead was segregated in the minor phase of the as-solidified structure, but was distributed in the matrix after anneal. The electrical resistivity and carrier type were insensitive to the distribution of lead in the two-phase structure. ThERE has been considerable interest in the Ag-Sb-Te system because of its thermoelectric properties. The major interest has been in compositions on the vertical section between AgzTe and SbzTes, particularly the 50 mole pct SbzTes composition AgSbTez (compositions are conveniently expressed as mole percent SbzTes along the AgzTe-SbzTes section). One of the major problems in the proper evaluation and utilization of this material is the inability to control the electrical properties through impurity additions: all alloys prepared to date have been p-type, even with the addition of large amounts of impurities. It has been shown Wit all the compositions previously studied contain an intermediate phase of the NaCl st'ructure as a major phase (denoted by b) and a second phase, either AgzTe or SbzTe3, as a minor phase.'-3 One explanation for the unusual electrical behavior of this material is that the impurity additions have a higher solubility in the second phase than in the matrix; the impurity would segregate to the second phase, leaving the bulk matrix essentially free of impurity.4 In order to investigate this mechanism with a specific impurity element, the distribution of lead between the two phases was determined using autoradiography. Lead 210 was chosen because of the suitability of its 0.029 mev 0 particle for autoradiography and also because of the interest in lead as an impurity in this system.5'6 EXPERIMENTAL PROCEDURE Two compositions were taken from the vertical section between AgzTe and SbzTes, 50 mole pet SbzTes (Viz. AgSbTez) and 75 mole pct SbzTes, in which AgzTe and SbzTes appear, respectively, as the minor phase. Lead containing radioactive lead (pb210) was added to the above compositions to provide a concentration of 0.1 wt pct Pb. The material was placed in a graphite crucible in a quartz tube which was then evacuated and sealed. The samples were melted and solidified by cooling at a rate of 8°C per min and then removed and prepared for microa~toradiography. After autoradiographic examination of these samples, they were again encapsulated and annealed in an isothermal bath at 300°C for a number of days and prepared for examination. An alternate method of preparation employed a zone-melting furnace; the molten zone traversed the sample at a rate of 1.2 cm per hr and the solid was maintained at a temperature of 500°C both before and after solidification. This treatment had the same effect as solidification at a slow rate followed by an anneal for several hours at 500°C. In order to obtain the best resolution, thin sections of the alloy were prepared by hand lapping to a thickness of approximately 20 p. Other samples were prepared for examination by lapping a flat surface on the bulk sample. The resolution, although somewhat better in the former procedure, was adequate in both instances and the majority of the samples were treated in the latter fashion. A piece of autoradiographic film (Kodak Experimental SP 764 Autoradiographic Permeable Base Safety Stripping Film) was stripped from its backing, care being taken to avoid fogging due to static-electrical discharge. A small amount of water was placed on the sample, the film applied emulsion side down on the surface of the sample, and the sample and the film dipped into water in order to assure smooth contact. After drying, the film was exposed for 2 to 5 days, the period of time selected to give the best resolution. The film was developed on the specimen and fixed and washed in place. Two major factors must be considered in establishing the reliability of an autoradiograph: the in-

Jan 1, 1964

By J. W. Pugh, J. D. Nisbet

F. B. Foley—The use of data published by Wever and Jellinghaus in 1931 to fix boundaries of the sigma phase in the Fe-Cr system, in the face of the author's own references to the suggestions of Bradley and Goldschmidt, Aborn and Bain, and Hougardy that the phase is much more extensive, and the very much more accurate work, which weighs heavily in favor of these suggestions, of Cook and Jones, published in 1943 and evidently disregarded by the authors, makes their derived ternary diagram, especially fig. 15 for 400°C, quite inaccurate on the Fe-Cr side and affects the extent of phase boundaries in the most controversial and important part of this ternary system. In commercial Fe-Ni-Cr alloys the occurrence of sigma has been observed time and time again at lower chromium contents than that of the 24 pct Cr, 16 pct Ni, 60 pct Fe alloy which is the lowest permitted by fig. 15 of practically carbonless metal. Newel1 reports sigma in 27 pct Cr-Fe even with some carbon present to be one of the greatest detriments to its extensive application, whereas Pugh and Nisbet set a low limit of 36 pct Cr for sigma in the binary Fe-Cr system. J. J. Heger—The diagrams presented by the authors do not agree with observations made on commercial Fe-Cr and Fe-Cr-Ni alloys, nor do they agree with two recent investigations made on the Fe-Cr and the Fe-Cr-Fe systems. I refer first to the investigation made by Cook and Jones1' on the sigma region of the Fe-Cr system. On the basis of their results which were published in 1943, Cook and Jones established new boundary limits for the sigma and the alpha plus sigma regions. These new limits have been accepted and are incorporated in the Fe-Cr diagram that appears in the 1948 edition of the Metals Handbook. This diagram is shown here as fig. 34. As will be noted, the boundary limits of the alpha plus sigma region in this diagram extend to much lower chromium contents than do those in the diagram presented by the authors in fig. 2. These new limits indicate that sigma phase should form in an Fe-Cr alloy containing 26 pct Cr, and experience with commercial alloys confirms this finding. Indeed, recent studies on a commercial Fe-Cr alloy containing 17 pct Cr have shown sigma phase to be stable in this alloy at 550°C. I recognize that the authors' work did not include studies on the sigma region; however, I believe this is a serious omission because sigma phase may profoundly affect the physical properties of these alloys and should be evaluated in any investigation which attempts to relate physical properties to the equilibrium diagram. The second investigation to which I refer is that made on the Fe-Cr-Ni system by Rees, Burns, and Cook,'' who used pure alloys and employed heating 17 W. P. Rees, B. D. Burns, and A. 3. Cook: Journal Iron and Steel Institute. (July 1949) 162, Part 3. p. 325. times that extend to 200 days. These investigators published their results in July 1949 and from these results constructed isothermal sections at 800" and 650°C. The isothermal section at 650°C is shown here as fig. 35. This diagram indicates sigma phase should form in a pure 18 pct Cr-8 pct Ni alloy. Although sigma phase has not been observed after 10,000 hr at 1200°F in commercial 18-8 alloys containing carbon and nitrogen, it has been observed under the same conditions in 18-8 alloys modified with titanium and columbium, both of which serve to reduce the effect of carbon and nitrogen. This section and the one at 800°C suggest that the constant iron sections which are presented by the authors, should be considerably altered, if they are to represent an accurate picture of the system. A few of the suggested alterations are as follows: In fig. 9, the section at 50 pct Fe, the gamma plus sigma region should be widened, not narrowed at 800" and 650°C. In fig. 10, the section at 60 pct Fe, the gamma plus sigma region should be widened at 800° and 650°C. In fig. 11, the section at 70 pct Fe, an alpha plus sigma, an alpha plus gamma plus sigma, and a gamma plus sigma region should be added. In fig. 12, the section at 80 pct Fe, the alpha plus gamma region should be widened at 800°C. In fig. 13, the section at 90 pct Fe, the alpha plus gamma region should be widened at 650° and 800°C. Undoubtedly, the chief reason for the discrepancies between the authors' data and those of Rees, Burns, and Cook is that the authors did not employ long enough heating times to allow for transformation. In this connection, I wish to warn that transformations in these alloys, particularly transformations at temperatures below 800°C, are extremely sluggish and may require a year or more to approach completion. Therefore, unless extremely long heating times are employed or steps are taken to accelerate these transformations by such means as mechanical working, the results will not yield an accurate picture of the alloy system. Certainly, an accurate picture is needed for the development of better high-temperature materials. E. J. Dulis-The purpose of this work is not clear. If an improvement of the ternary equilibrium diagram of the Fe-Cr-Ni system was wanted, it seems logical that testing techniques superior to those previously used would be a prime requirement. To approach equilibrium in this system, long holding times are needed; a fact established long ago but apparently ignored by the present authors, who used the continuous heating and cooling tests in equilibrium studies. A publication on the same system by Bradley and Goldschmidt6 was criticized by Monypenny in a

Jan 1, 1951

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'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 Jonathan S. Jackson, Bruce P. Ream

Leach water management is one of the few areas in dump leaching subject to operator control. As such, it is of considerable importance. Theoretical considerations indicate that high leach solution application rates are inefficient in washing solubilized copper from dumps. The high rates cause unnecessary dilution of copper values, raising unit recovery costs. Use of excessive amounts of leach solution also cools dumps, resulting in reduced leaching rates. This paper reviews leach solution application methods and details the results of field tests run to determine the benefits and feasibility of low versus high application rate techniques of applying water to dump surfaces.

Jan 1, 1980

By Ross C. Anderson, William I. Weisman

THE manufacture of anhydrous sodium sulphate or salt cake from natural deposits in the United States has been in general somewhat of a marginal undertaking. Competition from foreign sources and from large quantities of byproduct sodium sulphate produced domestically in the manufacture of hydro-chloric acid and other chemicals has existed and continues.

Jan 7, 1953

By C. K. Stoddard, R. G. Knickerbocker, E. T. Leidigh, R. R. Lloyd, K. L. Mattingly

DURING July 1941, a study was initiated at the Boulder City Experiment Station of the Bureau of Mines on proposed methods for the production of magnesium metal. The major emphasis was placed upon development of a process that required minimum reliance upon the sale or utilization of by-products to meet economic competition from processes already in operation. It was felt that only through the development of such a process could the nation's vast resources of dolomite and low-grade magnesite that are contiguous to large blocks of firm power be properly utilized. During the course of exploratory tests on electrolytic and electrothermic processes, it was noted that fused magnesium chloride would dissolve appreciable quantities of magnesium oxide in the presence of small amounts of boric oxide. The use of such a solution in an electrolytic cell employing a graphite anode and a steel cathode caused the deposition of magnesium at the cathode and the evolution of carbon oxides at the anode with minimal amounts of chlorine The original results were sufficiently encouraging to justify further investigation on an enlarged scale, since the process seemed to present advantages over other proposed processes 1.2 for the direct use of magnesium oxide in a fused chloride electrolyte. When work on a larger scale was initiated it was found that the addition of boric oxide to the electrolyte resulted in dispersion of metal and constantly decreasing current efficiency. However, by this time solubility studies had shown that magnesium oxide was sufficiently soluble in magnesium chloride melts containing no boric oxide to effect the same anode reactions, and development work was continued. Over two years of development work have been carried out, and considerable work remains to be done. It is desired to emphasize the fact that many of the difficulties met require a long period of continuous operation before they become serious enough to affect operation of the cell. ACKNOWLEDGMENTS This paper is one of many reporting on various aspects of the Bureau of Mines' program initiated in August 1939 by passage of the Strategic Minerals Act the scope of which was greatly expanded by subsequent legislation. Some of these papers are published as war minerals reports. others as bulletins, technical papers, reports of investigations

Jan 1, 1945

By C. Carlson, W. Muir

The oxygen demand of the complex lead-zinc-iron feed at the Cyprus Anvil concentrator was determined dependent on the cyanide ion concentration of the pulp. By redistribution of the cyanide added to the grinding circuit in direct proportion to the amount of surface area created, a more activated flotation feed is obtained. Monitoring the oxygen demand of the flotation feed and grinding mill discharges has proved useful in diagnosing metallurgical problems in day-to-day operation.

Jan 1, 1976

By Roy P. Full, Robert M. Grantham

Regional structural adjustments in early Tertiary time resulted in the development of the Republic graben, a major down-dropped block that is from 6 to 10 miles in width and more than fifty miles in length. The graben became the center of extensive volcanic activity during Eocene and Oligocene time, resulting in a thick sequence of water-laid tuffaceous sediments, volcanic flows, and associated intrusives. A younger series of sediments, pyroclastics, and flows were deposited in structural depressions within the graben following the period of widespread volcanic activity. The Republic mining district is located along one of the major intragraben structural zones, where continuing subsidence during the period of volcanic activity resulted in an increased thickness of flows and associated flow breccias and pyroclastics. Intrusive masses in part healed early graben-forming faults, but later subsidence reopened old faults and created new fracture zones which later became the control for the gold-quartz veins. Considerable block adjustment along the subsidence area is evidenced by the structural pattern in the mines, and telescoped vein structures indicate north-south compressional stresses and east-west graben-forming tensional stresses prior to and during the emplacement of the veins. The veins, varying from a few feet to more than 50 feet in width, are filled primarily by fine-grained quartz, commonly chalcedonic or porcelain-like in appearance. Finely laminated dark-gray to black concentric banding within the veins generally distinguishes the better-grade ore zones, which contain finely disseminated sulfides and ore minerals that include principally electrum, stephanite, naumannite, and native silver.

Jan 1, 1968

State of California, Division of Mines, Ferry bldg., San Francisco, Calif. Walter W. Bradley, State Mineralogist. A list of publications available will be sent upon request. Bulletin 77 is a list of publications complete from 1880 to 1917 and contains synopses It is sent free. Bulletin 105, California mineral production and directory of mineral producers for 1930, brings the complete list up to date, sent free on request The Division of Mines issues principally (1) A series of Reports, (2) Bulletins, (3) Preliminary Reports, and (4) maps. The Reports were first issued biennially, later annually, and for the past few years they have taken the form of quarterly reports. The yearly subscription price for the quarterly reports is $1, payable in advance Reports and separate chapters available are Report 2, First Biennial (1892), $1, 14 (1913-1914), Chapter on mines and mineral resources of Colusa, Glenn, Lake, Mann, Napa, Solano, Sonoma, and Yolo counties, 50 cents, 15 (1915?1916), Mines and mineral resources of Butte, Lassen, Modoc, Sutter and Tehama counties, 50 cents, and Mines and mineral resources of Monterey, San Benito, San Luis Obispo, Santa Barbara and Ventura counties, 65 cents, 16 (1917-1918), Nevada County, 75 cents, Plumas County, 50 cents, Sierra County, 50 cents; 17 (1920), Mining in California during 1920, $1 75, 18 (1922), Mining m California, chapters for Aug , Sept , Oct , Dec , free, 19 (1923), Mining in California, chapters for Jan , Feb , Mar, Sept , free, 20 (1924), Quarterly chapters on mining in California (except July, out of print), 25 cents, 21 (1925), Quarterly chapters containing county reports- Jan (Sarcramento, Monterey, Orange) 25 cents, April (Calaveras, Merced, San Joaquin, Stanislaus, Ventura), 25 cents, July (Del Norte, Humboldt, San Diego) 25 cents, Oct (Siskiyou, San Luis Obispo, Santa Barbara), 25 cents; 22 (1926), Quarterly county reports: Jan. (Santa Cruz, Trinity), 25 cents, April (Shasta, San Benito, Imperial), 25 cents, July (Mann, Sonoma) and Copper in California, 25 cents, Oct (El Dorado, Inyo) Minarets District, 25 cents, 23 (1927), Quarterly county reports- Jan (Contra Costa), 25 cents, April (Aniador, Solano) Bibliography of clay

Jan 1, 1933

By H. W. Gillett

Many of the parts of motor cars, aircraft, etc., that require strong light construction, hence must be made of high-quality steel, are stressed to the maximum limit only in a very small volume. In parts subject to bending stress a line or even a point may take the maximum stress. A series of endurance tests under repeated bending in progress in the U. S. Bureau of Mines laboratories, like similar tests by other investigators, has shown the great difference in life of sister bars of the same stecl, handled in the same way and tested at the same nominal stress. It is known that a surface notch or scratch greatly increases the local stress over the nominal calculated stress; internal notches, such as those formed by inclusions or sonims, probably have a similar effect. From the tetss made by the Bureau of Mines, the cleanliness of the steel at the dangerous section, or point of maximum stress, seems to be one of the most important factors in determining the life of the piece. The more localized the stress, the more does chance, rather than the average properties, dctermine the life of the steel. The usual test, a tension test of a bar taken longitudinally, is not sensitive to the local drop in strength (or tendency to increase the true local stress over the nominal) because of inclusions, which probably have a more injurious effect in hard heat-treated steels, such as must be used when great strength is sought, than in softer steels. Users of steel who make transverse tests find surprisingly low ductility on transverse bars of dirty steel, though the longitudinal tests may be good. Bending tests, reverse bending tests, and notch-bar impact tests,

Jan 1, 1923

Discussion of the paper of Woolsey McA. Johnson, presented at the Butte meeting, August, 1913, and printed in Bulletin No. 79, July, 1913, pp. 1137 to 1145. F. L. GRAMMER, Leesburg, Va. (communication to the Secretary *):-Mr. Johnson's paper must interest by suggestion those connected with the " burning " of lime, the production of cement, and the smelting of iron. All iron men know how quickly the impalpable purple ore of wet origin reduces compared to finely ground red hematites of approximately identical composition obtained from Lake lump ores. Most housekeepers appreciate that the several forms of carbon-charcoal, coke, and anthracite, not to include graphite and diamond -have different temperatures of ignition. The temperature usually rises with the density and hardness. Some of the scientific bureaus of the government might appropriately conduct some tests along lines suggested by Mr. Johnson's article. We are unable to say whether the topic lies within the spheres of activity of the Bureau of Mines, the Bureau of Soils (Agricultural Department), the Geological Survey, or the Bureau of Standards. The calcining qualities of limestone is a topic too wide for individual effort and is of wide enough interest to merit government or State activity. It is of interest, as aforesaid, to burners of lime, cement manufacturers, and smelters. The chemical composition of a limestone does not tell all the story -if over 1-in. size lumps. The limestones of Annville and Myerstown, Pa., break at a tap; those on the Hudson above Poughkeepsie .act like "nigger heads." The manager of lime kilns near Lake Champlain told me his fuel consumption was high compared to that at other points. Yet the Hudson and Annville stones were both of greatest purity, being rivaled by only the marble at Rutland, Vt., or some stones near Martinsburg, W. Va. A local kiln operator says the conglomerate or pudding limestones of Loudoun county, Va., act very differently in the kiln from the more normal limestone deposits nearby. The tilted and twisted bedding in the anthracite region tells the story of hard coal origin. We might therefore expect that the limestones of greater geological age or depth or metamorphism

Jan 11, 1913

By L. Adler

A relatively simple and effective technique is proposed to deal with the failure of geologic masses containing weakness planes. This technique, termed irextended" rupture envelope, provides a means to clearly distinguish rock and soil from fractured rock and, on a theoretical level, considers a matrix-inclusion system. It may also constitute the link between Mohr's and Griffith's failure theories. Included in the article are five sample problems concerning site location, structural design, strengthening the plane of weakness, changing the magnitudes of major and minor principal stresses and changing the orientations of major and minor principal stresses. Engineers trying to solve design problems in rock and soil mechanics have often assumed an iso-tropic and homogeneous medium. For naturally occurring geologic masses this assumption has always been viewed with regret. The following analysis which deals with the effects of plane anisotropy on failure presents a solution to this. The planes of weakness are joints, faults, bedding planes, fracture and cleavage (natural and induced), foliation and schistosity. The physical properties of these weakness planes include an undulating surface, frictional resistance, discontinuous extent, filling material, tightness and presence of water to cause a hydrostatic pore pressure. All of these properties relating to failure can be summarized in Mohr's rupture envelope for the plane of weakness. This, along with the geometrical orientation, strike and dip, of the plane of weakness produces what is termed an irextended" rupture envelope. MOHR'S STRESS CIRCLE AND RUPTURE ENVELOPE The significant features of these concepts are listed below.' 1) A point on the u - r coordinate plane represents the normal and tangential stress components on a reference area in the material. This area can have any orientation. (Fig. la)

Jan 1, 1963

By James H. Bechtold

The yield strength of annealed tungsten was found to have a strain rate exponent 12 times as great as that of low carbon steel. The effects of temperature and strain rate could be correlated through the Zener-Hollomon parameter with a heat of activation associated with yielding of 32,000 cal per g-atom. This heat of activation is independent of strain although both the temperature and strain rate dependence of the yield strength vary with strain. MOST metals have mechanical properties that are relatively insensitive to strain rate, especially at temperatures below that at which creep is important. In iron and molybdenum," however, relatively large strain rate effects are observed in the temperature range where the rapid increase in yield strength occurs which leads to the ductile to brittle transition. In this temperature range Zener and Hollomon' have suggested that the effects of strain rate and temperature T on the yield strength could be correlated through a single parameter, P, in the following manner where Q is a heat of activation characteristic of the metal and associated with some unspecified relaxation process. They also observed that if the temperature is restricted to a relatively narrow range— below room temperature for steel—that the logarithm of the yield strength could be expressed as a linear function of the logarithm of P. From this relation the logarithm of stress should be a linear function of the logarithm of the strain rate at constant temperature: where r will be referred to herein as the strain rate exponent. At a constant strain rate the logarithm of stress should be a linear function of l/T, ay(e = C) ~ eT [4] where q = Qr [5] and is referred to herein as the temperature exponent. These equations have been found to relate the effects of temperature and strain rate on the yield strength of molybdenum in the temperature range wherein the ductile to brittle transition occurs, —75° to +150°C.2 Bechtold and Shewmon3 have shown recently that the ductile to brittle transition in annealed tungsten occurs in the temperature range +150° to +350°C. In this temperature range the yield strength in-

Jan 1, 1957

Jan 1, 1930

A High-speed Dilatometer and the Transformational Behavior of Six Steels in Cooling. By Arthur L. Christenson, Edward C. Nelson and Clarence E. Jackson. (With discussion).................................606 Dilatometric Studies of the Graphitization of Cast Iron. By N. A. Ziegler. With discussion) 627 An Interferometer Type of Dilatometer and Some Typical Results. By- L. '4. WIlley and W. L. Fink. (With discussion).........................642 The meeting was held in the Pine Room of the Statler Hotel, Cleveland, Ohio, on Tuesday afternoon, October 17, 1944. The chairmen were F. M. Walters, Jr. and Howard Scott. Introduction F. M. Walters, Jr.—The principal advantages of the dilatometric method perhaps are two, as compared with the method of thermal analysis. One is that the dilatometric method can be applied with a large variety of rates of heating and cooling, whereas thermal analysis—that is, the study of the transformational characteristics by means of heat evolution—is limited to the rates of heating and cooling that reveal the evolution of heat. The dilatometer can be used for the study Of reactions at zero rates of heating and cooling; that is, isothermal reactions. As you will hear this afternoon, the rates have been pushed up as far as 500°C. a second. The other advantage is that the dilatometric method shows that a two-phase region is a two-phase region, whereas the thermal analysis merely reveals the temperature at which the rates of heat evolution are greatest.

Jan 1, 1945

By H. Rumfelt

Surface excavators for mining coal and such non- metallic minerals as quarry stone, gypsum, phosphate and the like have advanced tremendously in the last 50 years, and their advancement has paralleled that of excavators used in the construction industry during the same period. Up to a certain stage, the construction industry led the way with this development and even pioneered in how the equipment was used. Afterwards, however, new mining machinery and related operating techniques progressed along a different path than their construction counterparts because of the different demands of the two industries. The word "stage" as used above quite generally connotes a transition period, possibly of several years' duration, during which mining development followed the construction industry. Later, mining branched out and responded to its own needs. Most readers are familiar with the events which led to the development of the power shovel. The first dredge was recorded as having been used in England in the latter 1700's and was no doubt developed along the lines of some notes written in the late 1400's by Leonardo da Vinci.

Jan 1, 1971

As knowledgeable men in the industry know, a mineral occurrence is found through prospecting but an ore deposit is "made" -made through, first, imaginative and effective exploration; thence through efficient engineering, sales and management. There are two main phases of exploration-reconnaissance and target investigation-each of which can be further divided into two additional stages (see accompanying table). The search for a new ore deposit within a known and geologically mapped mining district involves only the last two stages, whereas the search for a new orebody in a virgin geologic environment involves at least three stages and often the full sequence. Of course, some of the exploration stages may be bypassed depending on available results of previous mineral surveys and/or exploration by individuals, business concerns, and governments.

Jan 10, 1967

By D. U. Deere

The title of this chapter is "Indexing Rock for Machine Tunneling" or, a simplified approach to a very difficult problem. I do not think that we can divorce the considerations for conventional tunneling from that of the requirements in terms of geologic information that is necessary for machine tunneling. Experience has shown that in conventional tunneling, the rate of progress achieved in driving a tunnel and the cost involved can be almost directly related to the general rock quality and to the water conditions actually encountered. The very method selected for driving the tunnel or perhaps adapted during the construction period, that is, full-face, top-heading and bench, or multiple-drift, is largely determined by the degree of severity of the adverse geological features. The amount and type of support required to stabilize the rock behind the advancing face are also directly related to the ground conditions. The support may range from bald-headed to rock bolts placed as needed- perhaps pattern rock bolting, light steel sets, all the way to closely spaced heavy steel sets with full lagging and invert struts. At times crown bars, spiling, and breast boarding must be used to advance the face. Shotcrcte applied immediately to the arch and upper walls is a fairly recent advance in providing both temporary and permanent support. Ground-water inflows can further reduce the rate of advance, causing stability problems and reducing the overall efficiency of the mining crew. Required pumping may also be very expensive depending on the grade of the tunnel and the amount of water. And in shafts, of course, there is the pumping problem. To offset the adverse effect of the ground-water inflows, one must often resort to grouting ahead of the face. But this very operation which helps cut down the water inflow also increases greatly the time required for mining, and of course, there is additional cost involved in the actual operation. The conditions described above do not occur uniformly throughout the rock mass but rather they are concentrated

Jan 1, 1970

T. T. READ, Secretary of the Committee on Industrial Organization, presents the following very interesting monthly ad interim report: Reports from London are to the effect that 750 housing schemes for workers, involving the erection of 128,000 new dwellings, have been submitted to the Local Government Board. Birmingham alone needs 14,000 new houses, and the Housing and Town Planning Committee of the City Council considers that 5000 new houses must be built each year for the next 20 years. Nine hundred acres of land has been acquired, on which to build 10 to 12 houses per acre for the next two years. The town of Dudley, which built 300 modern dwellings in 1915-1916, submitted schemes for another 500 houses. There is a shortage of building materials required, specially brick. Financial assistance has been received for reopening brick yards that were closed during the war. W. E. Dickson, vice president of the Midvale Steel & Ordnance Co., is reported in the daily press as stating that his corporation is planning to spend $8,000,000 in improving its plant and assisting its employees in building their own homes. The company will advance 90 per cent. of the cost of the house and extend payments over a period of 12 years. Methods of work employed in building 256 houses at Quincy, Mass., for the workers of the Fore River shipyards are described, by Joseph Meltzer, in the Engineering News Record for May 29, 1919. The approximate cost was about $3500 per house, not including water supply, sewers, streets, and sidewalks. "Comparative Costs of Tenantry and Home-Owning;" "A Plain Talk on Helping Home-builders;" and "More Plain Talk on Home Building" are the titles of three publications of the Information and Education Service of the Department of Labor. These publications should be' of a good deal of service in convincing employees that it is to their interest to own their homes rather than to live in rented houses. The same Service has issued pamphlets discussing the cost of materials.

Jan 7, 1919