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By J. Gurland

The wmk is concerned with the estimate of the degee of continuity of a particulate phase dispersed in a matrix. The first section is a verieu: of the parameters nzeasurable by quantitative rnetallogvaphy, namely the contact area and, under certain conditions, the number of contacts between particles of one phase. In the second section, the frequency of particle contacts is related to the degee of continuity of a randomly embedded phase orz the basis of the lattice-percolation model of Hamrnersley and others. THE extent of continuity of the constituent phases may greatly influence the structure-sensitive properties of phase mixtures, particularly if the phase properties differ significantly. An example from the literature1 is shown in Fig. 1. The marked decrease of the electrical resistivity of sintered silver-alumina bodies near 25 pct by volume of silver presumably occurs because the more conductive phase changes from a discontinuous to a continuous structure. Other example of electrical- and thermal-conductivity transitions are cited by kingery In view of these observations, a knowledge and understanding of the connectivity of the microstructure may be of considerable practical importance. This study is concerned with one aspect of the genera1 problem, namely the estimate of the degree of continuity of a particulate phase dispersed in an opaque matrix. The first section reviews the parameters measurable on a polished cross section by auantitative metallography, such as the contact area and under certain conditions, the number of contacts between particles of one phase. In the second section, an attempt is made to relate the frequency of particle contacts to the degree of continuity of a randomly embedded phase. For the purpose of this discussion, the aggregate has two constituents: the particulate phase and the matrix. The latter is considered to be homogeneous. The term "particle" is used with the meaning of "grain", i.e., a minute unit of matter which is usually a single crystal of a readily distinguishable substance within the confines of a simply connected boundary. While many of the concepts which are used here to describe the structural variables characterizing the microstructure of phase mixtures are qualitative and ill-defined, they are presented with the intent of stimulating further work of a more general and rigorous nature. I) PARTICLE CONTACT, CONTIGUITY, AND MEAN FREE PATH 1) Measurement of Contiguity. The fraction of the total internal surface of a phase a shared with particles of that same phase in a two-phase mixture of and $ is indicated by the contiguity ratio:3 whereis the area of the interface between o particles, and Sap is the area of the interface between a particles and matrix P, per unit volume of mixture. The contiguity ratio ranges from 0 to 1 as the distribution of the a phase changes from a completely dispersed to a completely agglomerated structure. The interfacial areas may be obtained from simple intercept measurements on a random plane, after Smith and Guttman where and N are the numbers of intercepts between a random line of unit length on a plane of polish and the interparticle and interphase interfaces, respectively. The equations are valid for any distribution of particle sizes and shapes.

Jan 1, 1967

By L. Himmel, R. F. Mehl, C. E. Birchenall

The rates of self-diffusion of iron in artifically prepared wustites of various compositions have been determined using the decrease in surface activity technique. Similar measurements are reported for artificial magnetites of nearly stoichiometric composition and for natural hematite single crystals. These data, together with appropriate thermodynamic data derived from the present study or from the literature, are used to calculate the rates of oxidation of iron and its oxides, taking as a basis the theoretical rate equations developed by Wagner. The calculations are compared with experimental rate constant data for these same reactions and are shown to provide essential confirmation for the Wagner theory. For the most part, the results are also consistent with the previously proposed transport mechanisms in the oxides of iron. WHEN a metal is exposed to an oxidizing atmosphere at elevated temperatures, a superficial oxide layer is formed which then thickens according to some characteristic rate law. Provided that the oxide layer is dense and continuous and does not present any paths for gaseous diffusion, continued growth must inevitably involve the migration of the reactants—either the metal or oxygen or both—through the lattice of the solid oxide. This is true whether the reaction rate is controlled by the diffusion process itself or by a slow step in a reaction at one of the interfaces. If the overall rate is limited by diffusion, and if the concentrations or thermodynamic activities of the reactants at the boundaries of the oxide layer are independent of time, the familiar parabolic rate law is observed. Under these conditions, Wagner1 has shown that the rate constant may be expressed in terms of the mobilities of the reacting components and the appropriate concentration or activity gradients which are established across the growing oxide layer. In presenting the phenomenological basis for the theory, Wagner has emphasized the role played by lattice defects in diffusion processes in oxides. The essential validity of this theory has been confirmed by experiment for a number of simple systems including the growth of Cu2O on copper.'-' One of the objectives of the present study has been to extend the Wagner approach to the more complex process of the oxidation of iron and its oxides, and particularly to wustite, which is normally the major constituent of the oxide scales formed on iron at temperatures above approximately 570°C. For this purpose the rates of self-diffusion of iron in w?stite, magnetite, and hematite have been measured by tracer techniques and the necessary thermodynamic data have been obtained from equilibrium studies involving the oxides and their atmospheres. These data have subsequently been used to test the underlying assumptions of the Wagner theory as well as the detailed mechanism of the scaling of iron previously proposed by Davies, Simnad, and Birchenall.5 Lengthy treatments of diffusion and conduction phenomena in ionic crystals have been published." * The latest, by Jost,8 also summarizes much of the existing experimental data. In general, however, the oxides of iron have not been considered specifically and hence a brief review of the available

Jan 1, 1954

By F. Keller

ALUMINUM alloys containing magnesium and silicon are susceptible to strengthening and hardening by suitable heat-treatments, and they constitute a class of alloys of considerable commercial importance. Generally, they contain these two elements in the proportions required for the formation of the intermetallic compound Mg2Si, or an excess of silicon; no commercial wrought alloys are made with an appreciable excess of magnesium. The reason for not having excess magnesium is obvious from the results given in this paper, since it is shown that excess magnesium results in a proportional decrease in the solubility of Mg2Si. This is the eighteenth1 of a series of papers from the Aluminum Research Laboratories dealing with the equilibrium relations in aluminum-alloy systems; most of the previous publications concerned binary aluminum-alloy systems; this is the fourth of a group pertaining to ternary aluminum-alloy systems. The work on this system was com-pleted in 1930, but the results were not published because of the pressure of other work. Hanson and Gaylor2, in 1921, presented the results of an extensive investigation of the aluminum-magnesium-silicon system. Their results indicated that an excess of magnesium over the amount required to form the compound Mg2Si caused a noticeable decrease in the solid solubility of Mg2Si in aluminum. A more recent investigation3 in these laboratories showed that the solid solubility of Mg2Si in aluminum was 1.85 per cent at 595° C. and decreased to 0.30 per cent at 300° C. The results of the latter investigation were used as the basis for the present work.

Jan 1, 1936

By Karl J. Dreher, Charles C. Hennig, Gregg A. Scott

INTRODUCTION Theodore Roosevelt Dam is a cyclopean-masonry, gravity-arch dam located on the Salt River northeast of Phoenix, Arizona. Construction of the dam began in 1903 and was completed in 1911. The dam is about 85 m high with a total reservoir capacity of about 1.7x109 m3. Raising the dam is now being considered to provide additional water storage and flood control. This paper describes preliminary analyses performed to assess foundation stability for increased loading resulting from raising the dam and reservoir water surface about 12 m. The foundation of Theodore Roosevelt Dam consists of variably metamorphosed limes tones, sands tones, mudstones, and shales. Bedding uniformly strikes nearly normal to the river (N 40º W) and dips upstream at 25 to 30º. The rock is cut by four prominent joint sets as indicated by the joint contour diagram shown in figure 1A. The diagram was developed from surf ace observations and vertical drill core oriented relative to the bedding. Sampling biases account for the differences in concentrations of various joint sets. However, field observations indicate that all sets are relatively prominent, planar, and continuous. SEEPAGE ANALYSES Consistent with practice at the time of construction, no foundation drainage was installed at Theodore Roosevelt Dam. Finite element seepage analyses were therefore performed to study the potential for large uplift pressures in the foundation. The dam has steep abutments and is curved in plan as shown in figure 1B. The effects of modeling the seepage two-dimensionally, radially symmetric about the dam's axis center, and three-dimensionally were therefore com-

Jan 1, 1982

By R. W. Nash, A. E. Schwaneke, V. R. Miller

The Bureau of Mines developed a detector for controlling sorting devices to separate the copper-bearing fragments from the barren portion of Michigan native copper and western prophyry copper ores. A successful sorter could be used to preconcentrate the ore and eliminate costly hoisting or hauling of waste. An induction balance unit was developed and used in sorting tests on crushed sized - 2.5 + 1. 3-cm (- 1 + 1/2- in.) ores from the Kingston (0.9% Cu) and Centennial (1.6% Cu) mines of Upper Michigan. Concentrates of 4.0% and 7.5% Cu, respectively, were obtained at recoveries of 85 and 80% of

Jan 8, 1978

By H. M. Chance M

The following tables have been compiled from the annual reports of the Inspectors of Mines, to determine the percentages of fatal and non-fatal casualties from roof-falls and explosions of fire-damp. As we cannot assume that every accident has teen recorded by the inspectors ; as many casualties terminating fatally after the lapse of a considerable period, are inevitably recorded as " non-fatal;" and as clerical errors may have crept into the compilation,* the figures of these tables cannot be considered absolutely correct, but the summary is sufficiently reliable to show the features I wish to differentiate. Under the heading " Miscellaneous" are included all accidents not directly attributable to explosions of fire-damp, roof-falls or fails of coal. Prominent among the numerous causes included under this head are premature or delayed explosion of blasts, accidental explosion of powder or cartridges, accidents from mine cam, falls in shafts, machine accidents, sliding of loose coal in pitching breasts, suffoca tion by choke-damp, etc., comprising in all 48 per cent. of the total number of casualties.

Jan 1, 1882

By Lawrence Burkhart, S. B. Joo

Axially unsymmetric ordered circulation patterns on the surface of a hemispherical constant volume drop with forced Internal motion were considered as a manifestation of hydrodynamic instability, which was affected by internal flow as well as by the properties of the interface A simplified mathematical model was analyzed In order to study the mechanism of onset of interfacial circulation from a non-circulatory basic state. Values of the critical Reynolds numbers were obtained when the basic state became a fully developed rotational flow and the values changed for different interfacial properties. The work describes a heretofore unreported surface flow pattern on drop surfaces From a practical point of new, any motion in the interface of a droplet can have a significant effect of mass transfer rates in solvent extraction processes Although surface motion in droplets actual processing equipment is very complex, continued study of the fundamental nature of such phenomena should ultimately lead to more effective equipment design procedures.

Jan 1, 1981

By Clemens Jones

An interesting paper by J. E. Merion and Edward Hart, in Volume I., No. 2, of the Journal of Analytical Chemistry, on the Decomposition of Blast-Furnace Cinder by Acid, describes a plan of sampling the cinder by means of a previously-heated iron bar thrust into the cinder car or into the cinder at the notch, and then allowed to cool, thus chilling the cinder which adheres to the bar, and rendering it decomposable by hydrochloric acid, of 1.12 sp. gr. A short series of results is given, from which the deduction follows that blast-furnace cinder " is decomposed perfectly when chilled." Where many silica determinations are to be made, this method, if reliable, would effect notable economy of time and reagents. The conversion of insoluble silicates by fusion with an alkaline carbonate, together with the subsequent solution, evaporation, drying, etc., is destined to remain the standard method. But all fusionmethods are time-consuming and expensive. Chilling appears to render the supplementary method available for all practical purposes, in the determination of silica in cinder. But, with a view of securing more evidence on the subject, and in view of the fact that uniform results were not obtained by employing this method, it was decided to test the method in the laboratory of the Thomas Iron Company where a large number of silica determinations are made. The experience met with may not be devoid of value, both theoretical and practical. Mr. Iles's paper, in the Chemical News, Volume L., 1881, doubtless suggested to several chemists, connected with iron metallurgical

Jan 1, 1888

By C. E. Lawall

ONE of the most important developments in the coal industry during 1940 was the continued uptrend in the production of bituminous coal. Estimated production for the year is 450,000,000 tons, with an additional production of anthracite of 50,000,000 tons making a total of approximately 500,000,000 tons. This is an increase of 12.5 per cent over 1939. Despite an estimated decrease of about 3.5 per cent in anthracite production, all of the major coal-producing states had increases in production for 9140. The national defense program, with the consequent increase in industrial activity, undoubtedly had an important effect on the increased demand for coal.

Jan 1, 1941

By Thomas P. Bispham

INTRODUCTION From the lender's point of view, the greatest period of risk in a project financing occurs during the construction phase. Therefore, most projects are supported during this phase by completion guarantees supplied by some credit-worthy entity; for example, the project sponsors in the case of a joint venture, such as that of W.R. Grace, Hanna Mining, and Liberty Capital; or by a strong contract with a utility or foreign importer/investor, such as the way North American Coal Corporation has structured many of its transactions. THE PROJECT LOAN REQUEST A project financing is a more complex form of term loan than one using an ongoing corporation's balance sheet as a credit base and, therefore, a potential lender will subject the loan request to a more rigorous analysis. To support this effort, the financial institution will require a more detailed information memorandum to evaluate the credit and technical risks of a project - especially since much of the necessary information is not otherwise available. (See also Gibbs and Sroka paper above in this Chapter) A well-prepared information memorandum will impress prospective lenders with the planning ability and general competence of management. Also, the process of preparing the memorandum will help management understand the true extent of the opportunities and limitations of its venture. Appendix A outlines the topics which comprise a complete information memorandum for a loan request. Of some interest to those seeking to sell a currently-operating mining venture, a similar information memorandum should be prepared i.e., covering the same topics discussed here, for the investment banker to use with potential purchasers. For that purpose, though, one might not want to prepare quite as much detail as for a lender. Appendix B outlines the elements of a reserve evaluation and feasibility study, often called the "Bankable Document." Usually, these studies are prepared by independent engineering consultants for use by potential borrowers and sellers. (Potential purchasers will often contract for a similar study for their use in evaluating an acquisition.) ELEMENTS OF A LOAN INFORMATION MEMORANDUM 1. Outline: The information memorandum should begin with a one-page outline covering such topics as: a. The borrower's name, address, and phone number. b. Principal contact at the borrower. c. Amount of the proposed financing. d. Desired pricing and structure of the proposed financing. This should include a description of the amount and source of equity in the proposed financing. e. Use of the proceeds and timing. 2. Summary: The most important information contained in the memorandum should be summarized in two pages. Note - If the borrower is a recently-formed single-purpose company, then elements 3, 4, and 5 will apply to the guarantors of completion and to the project sponsors. 3. The Borrower: This section is a brief biography of the borrower including such topics as date and state of incorporation, founder(s), lines of business, etc. 4. Capitalization: The borrower's current debt and equity position, including leases and trade debt, with amounts, terms, names, and addresses enumerated. Equity owners, and percentage ownership, should be identified. 5. Historical Financial Statements: If available, a minimum of five year's worth of complete historical financial statements

Jan 1, 1985

A. W. TRACY' AND D. H. THOMPSON (presented in written form).-Messrs. Ed¬munds, Anderson and Waring are to be commended for their excellent work in so painstakingly reducing to constants, the variables believed to be associated with these types of stress corrosion. An ammonia stress-cracking apparatus similar in many respects to the one described has been assembled. Certain aspects of its construction may be of interest. Tensile loading of the specimens, which are usually Y8-in. diameter wires, is accomplished by springs acting in compression in compact, portable, tubular assemblies weighing less than 10 lb. The lower end of each assembly contains the test specimen and is passed into the test chamber for exposure to the moist ammoniacal atmosphere. There is considerable convenience in being able to load the specimens in a portable unit, which may be warmed to prevent condensation, and then thrust instantaneously into the test chamber. Spring loading obviates the use of weights, but it has the disadvantage of allowing some relaxation of the load if the specimen elongates during corrosion. The maximum loss in load found so far was 20 per cent. The air supplied to the test chamber is humidified by passing it through thermo¬statically controlled water. The air is dispersed into fine bubbles by being forced through a porous ceramic filter at the bottom of a tank containing about 10 liters of water. The temperature of the water is controlled independently of the tempera¬ture of the test chamber. Thus, with the

Jan 1, 1945

By H. M. Chance

Asst. Geologist, Pennsylvania Geological Survey THE following tables have been compiled from the annual reports of the Inspectors of Mines, to determine the percentages of fatal and non-fatal casualties from roof-falls and explosions of fire-damp. As we cannot assume that every accident has been recorded by the inspectors; as many casualties terminating fatally after the lapse of a considerable period, are inevitably recorded as "non-fatal;" and as clerical errors may have crept into the compilation,* the figures of these tables cannot be considered absolutely correct, but the summary is sufficiently reliable to show the features I wish to differentiate. Under the heading a Miscellaneous" are included all accidents not directly attributable to explosions of fire-damp, roof-falls or falls of coal. Prominent among the numerous causes included under this head are premature or delayed explosion of blasts, accidental explosion of powder or cartridges, accidents from mine cars, falls in shafts, machine accidents, sliding of loose coal in pitching breasts, sltffouration by choke-damp, etc., comprising in all 48 per cent of the total number of casualties. * Compiled by Mr. Maxwell Chapman

Jan 1, 1882

By Franz R. Dykstra, R. F. Tatnall

A ferroalloy is defined as: "An alloy of iron with some element other than carbon used as a vehicle for introducing such an element into the manufacture of steel. The element may alloy with the steel by solution or, as the carbide, -neutralize the harmful impurities, by combining with them and separating from the steel as flux or slag before solidification."a The most commonly used ferroalloys are: ferromanganese, ferrochrome, ferrosilicon, ferrovanadium, ferromolybdenum, ferronickel, ferrotungsten, ferrocolumbium, and ferrophosphorus. Concern here is with the sources and markets of the major metallic alloying elements. The discussion is further restricted to those - ferroalloy ores, the principal use of which is in the production of steel. Phosphorus, silicon, and tungsten, for example, are ferroalloys of some economic significance, but other uses dwarf their alloying applications. Thus, this discussion will deal with the ores of managanese, chromium, nickel, molybdenum, vanadium, and columbium. As shown in Table 14.1B.1 ferroalloys serve to- facilitate processing and impart to the finished steel such characteristics as tensile strength, ductility, low-temperature impact, hardenability, high-temperature strength, corrosion resistance, toughness, and abrasion resistance. In the steel-making process, ferroalloys may be added in the charge, in the molten bath near the end of the finishing period, in the ladle, or in the molds. Timing of the addition depends on the effect of the addition on the temperature of the molten metal, the formation and elimination of reaction products, and the protection of subsequent additions from oxidation. MANGANESE General Approximately 95% of the manganese ore sold is consumed by the steel industry, either as ferromanganese or as manganese metal. Manganese is the universal alloy, without which good steel cannot be made. It serves as a scavenger, removing phosphorus, sulfur and, to a degree, oxygen from the melt. As an alloying material it makes steel hard, tough, and resistant to wear. Approximately 6 kg of manganese is required for every ton of common steel produced by United States steelmaking practice. The remaining 5 % of the manganese ore consumed consists of special or so-called "chemical" ores, including high-grade pyrolusite ores, electrochemically reactive "battery ores," and a number of special varieties, as well as those otherwise regarded as "metallurgical ores."

Jan 1, 1976

By W. O. Philbrook, K. Natesan

A mathematical model was derived for the temperature change in a particle undergoing heterogeneous chemical reaction and heal exchange with a stream of fluid. The model has been applied specifically to the exothermic oxidation of spherical particles of zinc sulfide. Very good agreement was obtained between the theoretical prediclion and experimental observation. It was found that at no stage of the reaction was the particle subjected to a state of thermal instability. In studies of gas-solid reactions, it is generally assumed that the gaseous and the solid phases are at the same temperature throughout the reaction period. This is not strictly true since most of the reactions are either exothermic or endothermic in nature. This paper deals only with heterogeneous gas-solid reactions of noncatalytic type. In the case of exothermic reactions (e.g., roasting of sulfides), there may result an increase in temperature of the particle due to the release of the heat of reaction, and this increase in temperature may enhance the reaction rate and thus cause further release of heat. Such a "spiralling" effect may lead to a thermally unstable situation within the particle. On the other hand, in the case of endothermic reactions (e.g., calcination of limestone), there may occur a decrease in temperature of the particle as the reaction proceeds, leading to a virtual "quenching" of the reaction front. A general discussion of autothermic processes with emphasis on properties and reactor design is given by Van Heerden. 1 Levesque and cubicciotti 2 observed self heating of the sample in the oxidation of thorium. Anous et al. 3 observed self cooling of the sample in their dehydration studies on chrome alum. Cannon and Denbigh, 4 and Ong et al.5 reported self heating of the sample in their studies of the kinetics of oxidation of zinc sulfide. A typical plot of heat generation and heat loss rates with reaction temperature is shown in Fig. 1.'14 The Sigmoid curve represents the heat generation rate while the straight lines represent the heat loss rate. The main objectives of this analysis are to estimate the temperature increase of a single particle undergoing an exothermic reaction and to study the possibility of a thermally unstable situation within the particle. Also, a study of the dependence of the tempera- ture increase on different process variables has been attempted. A "she ll-by-shell" method has been proposed to analyze the problem. The shells may be made as small as necessary, and equations may be set up for heat transfer by various mechanisms. Such equations will have to be solved for each shell, with the boundary conditions for ith shell being obtained from the (i - 1)th shell, using a high speed digital computer. The oxidation of spherical particles of zinc sulfide is considered for this analysis, but the treatment is general enough to be applicable to other reactions and particle shapes. The oxidation reaction can be written as AH =« -115 kcal/mole ZnS [1] Such a reaction has been found to proceed in a topo-chemical manner; i.e., as the reaction proceeds, a progressively thicker outer shell of zinc oxide is formed, while the inner core of unreacted sulfide decreases. It has been found experimentally, both in the present work and in the previous investigations,4-6 that the particle retains its original dimensions. Therefore, at any given time, the particle may be

Jan 1, 1970

By John Boardman

THE latest metal-mine accident report available for the United States is that of the Bureau of Mines for the calendar year 1919. Quoting from Table 20, p. 53, of that report, we find that there were 468 men killed, 7 permanently totally disabled, 321 permanently partially disabled, 7848 injured seriously (more than 14 days disability), and 23,330 of 1 to 14 days disability. We have no records to show what the average days lost per case of accident is, but the records for the Anaconda Copper Mining Co. show that, leaving out the fatalities and total permanent disabilities, and counting those in which the lost time was one or more days, the actual days lost due to accidents, for the Butte mines and shops for five years, 1917-1921, were as follows: Accident Statistics, Butte Mines and Shops of A. C. M. Co. Rate Shifts Days Lost Year Accidents Total Shifts 10,000 Shifts Days Lost Per Acci-dent 1917 2,661 3,169,720 8.395 26,734 10.05 1918 2,765 3,545,149 7.799 39,199 14.17 1919 1,381 1,853,143 7.452 22,797 16.50 1920 1,376 1,879,410 7.321 20,164 14.65 1921 376 776,461 4.842 8,287 22.03 Total... 8,559 11,223,883 7.625 117,981 13.80 In order to place an economic value. on this loss, we will assume that all the 468 fatalities and the 7 total permanently disabled in the United States were com-pensated for at the rate which applies in the State of Montana, that is, $5000 each, and that the 8169 serious accidents in the United States were compensated for at an average of $70 per case, thus bringing the estimated compensation paid by metal-mining companies in the United States to the enormous total of $2,946,830 for the year 1919. The figure of $70 per case was obtained by dividing the total amount paid by metal-mining companies under Plan No. 1 of the Montana Compensation Law, for the first five years of its operation, by the total number of serious accidents for those years.

Jan 9, 1922

By AIME AIME

CONVENTION plans for the A.I.M.E. Regional Meeting to be held on the Minnesota Iron Range Aug. 12 to 1.5 are being completed to give the visiting member?s from all parts of the country a wide variety of technical and recreational features. High spots of the social events are the official dinner, dance, luncheon and golf: and of course, special provision is being, made for the entertainment of visiting ladies. The technical sessions will fit in with scheduled trips to view all phases of mining, beneficiation and transportation of iron ore. Men from the West and Southwest will find much of interest in the detail of the mining operations. A trip to the steel plant of the

Jan 1, 1941

By G. S. Hume

RECENT developments in the Turner Valley gas and oil field, 40 mi. southwest of Calgary, Alberta, have indicated a large producing crude-oil area. Drilling be¬gan in Turner Valley in 1913 but no major developments took place until the fall of 1924, when Royalite No. 4 well at a depth of 3740 ft. in the upper part of the Paleozoic (Mississippian) limestone obtained a production - of 20,000 M cu. ft. of gas with a content of about one imperial gallon of naphtha (73° A.P.I.) per M cu. ft. This well produced as much as 600 bbl. of naphtha per day, and until abandonment in 1934 produced 911,313 bbl., which together with the gas sold was valued at about $5,000.000.

Jan 1, 1937

By G. G. Luther, C. E. Jackson

THE relationship between hardenability and weldability has been mentioned many times. The ease of making a hardness survey has led to its wide use as a criterion [ ] of weldability and with a given class or series of steels for which the ductility under weld heat-treatment is known the test is entirely suitable. However, in studying a new steel the hardness survey is of less value, since it is based on the assumption that there is a correlation between hardness and ductility. Several attempts have been made to derive indices for weldabilityl and hardenability from the chemical analysis. In most of these proposals the effects of the different elements were considered to be additive, but recently Grossmami2 proposed a novel method of calculating the hardenability of a steel from its chemical composition. In the [ ] method proposed, a steel is considered as having a base hardenability due to its carbon content and grain size, and this base hardenability is multiplied by a factor for each chemical element present, The final product is the hardenability. The purpose of the present study is to point out the possible relationship between hardenability and the effect of welding on hardness and ductility for a number of plain carbon and low-alloy steels. The composition of the 25 steels reported in this paper as determined by chemical analysis is given in Table I. To eliminate the effect of variations in finishing temperatures, the 1/2-in. plates were normalized after heating for one hour at 1650°F. in a controlled-atmosphere furnace.

Jan 1, 1942

By Howard Clarke, Cyril Stanley Smith, Clarence Zener

THE importance of cold-working in the fabrication of metals is in marked contrast with our ignorance as to the nature of the accompanying internal changes. The failure of the usual methods of testing to provide a consistent picture of these internal changes has given the incentive for the present program of investigating the effect of cold-working upon the internal friction of metals measured at small strain amplitudes. It has previously been shown1,2,3, that the internal friction introduced by cold-work is removed by annealing at comparatively low temperatures. In the present paper the following additional factors are investigated: (I) frequency of measurement, (2) amount of cold-work, (3) temperature of measurement. Special care was taken to minimize the internal friction due to causes other than cold-work. The present paper is purely experimental, the authors believing that any conclusions drawn from this work as to the nature of the internal changes accompanying cold-work would be premature." PREPARATIONS OF SPECIMENS In this study of cold-work it was desirable to eliminate as far as possible all other sources of internal friction. One disturbing source is the lack of temperature equilibrium between adjacent crystallites of a vibrating specimen.4 Temperature equilibrium is aided by small grain size and by the use of low-frequency vibrations. Unless unduly long specimens are used, low frequencies can be obtained only in transverse vibrations. But in transverse vibrations a second source of internal frictions is present, that arising from transverse thermal currents.5 The effect of these may be reduced by increasing the transverse dimensions. The grain size and transverse dimensions of the specimens were thus so chosen as to render the vibrations simultaneously nearly isothermal with respect to intercrystalline thermal currents, and nearly adiabatic with respect to transverse thermal currents. The material for this investigation was a 70-30 brass, part of the same lot of material that was used for some earlier studies on the effect of strain on proportional limit.10 It had the following composition: copper, 70.59 per cent; zinc, 29.39; lead, 0.01; iron, 0.01. This material was received from the brass mill in the form of 3/4-in. rod, cold-drawn to final size by a 65 per cent reduction of area from material that had been annealed to give a grain size of 0.060 mm. Rods of appropriate length were annealed for 2 hr. at 400°C. and cooled in air. The annealed rods (grain size, 0.012 mm.) were then stretched in a tensiontesting machine, using special grips10 to ensure axial application of the load. The rate

Jan 1, 1941

By Donald F. Taylor

TANTALUM and columbium are newcomers in the world of metals. Many of the metals described in this volume had been known and used for centuries before either tantalum or columbium was known to exist. The scarcity of the ores and the comparative difficulty of extraction delayed their technology until specialized methods of processing could be developed. HISTORY Early in the nineteenth century, 1801, Hatchett discovered a new oxide, which he called columbium oxide, and a year later, Ekeberg announced that he had found a new element, which he named tantalum. The preparation of the metal tantalum in impure form was first announced by Berzelius in 1824, but the actual production of ductile metal did not occur until 1903, when von Bolton, of Siemens and Halske, developed a process for the production of tantalum pure enough to be drawn into electric-lamp filament wire. The use of tantalum as a filament wire began to decline when ductile tungsten was introduced in 1909. In 1921, C. W. sake, of Fansteel Metallurgical Corporation, produced the first ingot of tantalum metal in America. The first ingot of columbium was produced in 1927 in the laboratory of the same company. There are several good reasons why tantalum and columbium are often mentioned together. They occur together in their important minerals, are similar in many of their properties, and are

Jan 1, 1953