Search Documents

By W. L. Fink, M. S. Hunter, R. H. Brown

Early workers attempted to study the structure of alloys by measurement of equilibrium electrode potentials in aqueous solutions containing ions of the metals from which the alloy was made.' The method was subject to such limitations (e.g., the difficulty in attaining electrochemical equilibrium at low temperatures) that it has not been widely used by metallurgists. Recently, Seltz and co-workers have introduced a greatly improved method for studying alloys by measurement of equilibrium electrode potentials in molten salts.2"4 The mathematical treatment is the same, of course, as for equilibrium potentials of amalgams in aqueous solutions.5 This method will probably find extensive use, since it makes possible not only the determination of phase fields of equilibrium diagrams but also the determination of certain thermodynamic quantities which can be used advantageously in metallurgical calculations. However, the method presents difficulties. With many metallic and alloy electrodes, reversibility is not readily obtainable. Also, the difficulty of obtaining suitable material from which to make the cells is increased as the temperature is increased. Moreover, the necessity of carrying out measurements in a vacuum requires additional apparatus and introduces considerable difficulty, especially at the higher temperatures. Apparently, no consideration has been given heretofore to the metallurgical use of irreversible electrode potentials that exist when a specimen is immersed in a suitable aqueous solution at room temperature. The apparatus and the method required for such measurements are very simple, and if the results of such measurements could be demonstrated to be reproducible they might be very valuable in studying the structure of alloys. The method would not have the scope of that developed by Seltz and his co-workers because no thermodynamic quantities could be calculated from the data. However, the utility and the simplicity of the method might warrant extensive use for the determination of phase fields and similar applications. Theory of Irreversible Potentials A brief review of the theory of irreversible potentials will be given before showing how to interpret the potential readings in terms of alloy structure. It is known that heterogeneity of a metal surface in an electrolyte will produce points of different potentials, with the result that current flows between these points and electrochemical reactions occur. The points at which oxidation reactions are localized are known as anodes, and those at which reduction reactions are localized are known as cathodes.6, 7, 8 For the benefit of those who are not familiar with the terms anode and cathode as applied to a primary cell, the potential difference between anode and cathode of such a cell can be measured when

Jan 1, 1941

By M. S. Hunter, W. L. Fink, R. H. Brown

Early workers attempted to study the structure of alloys by measurement of equilibrium electrode potentials in aqueous solutions containing ions of the metals from which the alloy was made.' The method was subject to such limitations (e.g., the difficulty in attaining electrochemical equilibrium at low temperatures) that it has not been widely used by metallurgists. Recently, Seltz and co-workers have introduced a greatly improved method for studying alloys by measurement of equilibrium electrode potentials in molten salts.2"4 The mathematical treatment is the same, of course, as for equilibrium potentials of amalgams in aqueous solutions.5 This method will probably find extensive use, since it makes possible not only the determination of phase fields of equilibrium diagrams but also the determination of certain thermodynamic quantities which can be used advantageously in metallurgical calculations. However, the method presents difficulties. With many metallic and alloy electrodes, reversibility is not readily obtainable. Also, the difficulty of obtaining suitable material from which to make the cells is increased as the temperature is increased. Moreover, the necessity of carrying out measurements in a vacuum requires additional apparatus and introduces considerable difficulty, especially at the higher temperatures. Apparently, no consideration has been given heretofore to the metallurgical use of irreversible electrode potentials that exist when a specimen is immersed in a suitable aqueous solution at room temperature. The apparatus and the method required for such measurements are very simple, and if the results of such measurements could be demonstrated to be reproducible they might be very valuable in studying the structure of alloys. The method would not have the scope of that developed by Seltz and his co-workers because no thermodynamic quantities could be calculated from the data. However, the utility and the simplicity of the method might warrant extensive use for the determination of phase fields and similar applications. Theory of Irreversible Potentials A brief review of the theory of irreversible potentials will be given before showing how to interpret the potential readings in terms of alloy structure. It is known that heterogeneity of a metal surface in an electrolyte will produce points of different potentials, with the result that current flows between these points and electrochemical reactions occur. The points at which oxidation reactions are localized are known as anodes, and those at which reduction reactions are localized are known as cathodes.6, 7, 8 For the benefit of those who are not familiar with the terms anode and cathode as applied to a primary cell, the potential difference between anode and cathode of such a cell can be measured when

Jan 1, 1941

By C. R. Wohrman

A melt of pure electrolytic iron with about 0.4 per cent. sulfur and 7 per cent. manganese was prepared in connection with a study of inclusions in iron. The alloy darkened rapidly when etched with a 10 per cent, alcoholic solution of nitric acid, and microscopic examination revealed the presence of a semimartensitic, semi-Widmanstättian structure (Figs. 1 and 2) closely resembling the structures found by Benedicks in his artificially prepared "meteoric iron."' The structures found by Benedicks were readily explained by the presence in his alloy of the two well-known iron-nickel solid solutions, taenite and kamacite, and of their eutectoid (?) aggregate, plessite. By analogy, one would infer the existence of similar phases in the iron-manganese alloy just described, such an inference being strengthened by the similarity displayed in many ways by nickel and manganese in their effects on iron. Iron-manganese Alloys are Regarded as Homogeneous Heterogeneity of iron-manganese alloys has not been recognized heretofore, judging from the data of standard metallographic books and those of original papers. In fact, iron and manganese are quite generally regarded as completely miscible in the solid state. Dr. Rosenhain,2 for example, writes: Alloys of group (a), of which those of gold-silver, iron-manganese, and copper-nickel are examples, when allowed to crystallize sufficiently slowly to attain their condition of final equilibrium, present a microstructure exactly similar to that of a pure metal—the homogeneous character of the molten solution is in that case so completely maintained that the microscope cannot detect the presence of any second constituent. Guillet and Portevin3 refer to the iron-manganese system as an example of the "case of metals completely miscible in the solid state."

By Harry M. Bendler, W. A. Wood

Electron metallography has been applied to the study of the torsional fatigue of polycrystalline OFHC* copper. The development of slip bands, fis- sures, and microcracks has been followed as a function of strain amplitude and number of cycles. Those factors that have been found to be relevant to a geometrical theory of the fatigue process are described. From the point of view of this theory it is important to distinguish between the effects of cycling at large amplitudes and at small amplitudes (true fatigue deformation). EARLY investigations showed metal fatigue cracking is caused by continued reversal of a small plastic strain. Fundamental study of fatigue, therefore, has been largely concerned with the cumulative effects of these plastic reversals on the metal structure. In particular, recent work has shown that the plastic reversals produce slip movements that are finer than the slip movements produced by unidirectional increments of plastic strain; individual slip movements in fatigue, for instance, are too fine to see by optical microscopy.2 It has also been shown that the fine slip movements of fatigue tend to concentrate in bands and that in this way they can build up, after enough cycles, a progressive surface disturbance. It is this disturbance which, in effect, makes the slip movement visible. It is also in this disturbance that the first cracks appear to form. From this point of view, therefore, the problem of fatigue becomes one of finding why the fine slip movements should concentrate in bands and why the. bands should finally open into cracks. Thus far, study of the slip bands has been limited to the changes they produce at the surface only. These studies have given interesting results. Ewing and Humfrey3 many years ago showed that the bands in iron could extrude debris. Forsyth found that bands in aluminum alloys could extrude thin tongues of material. Thompson showed that, after lightly dissolving away the surface of copper specimens, some bands persisted as superficial cracks might, and that the life of a specimen under fatigue deformation might be prolonged by dissolving away the surface at intervals. Thus these and related results have suggested that the metal structure in fatigue bands may disintegrate and that this may happen long before obvious cracking. These surface studies, however, have not shown definitely how cracking may begin, for they do not show sufficiently what is happening in depth. However, some advance in this direction has been made recently by a new approach, summarized later, which reveals slip bands and their surface disturbances in section. In the work done thus far, the sections have been studied by optical microscopy only. In the present work they have also been studied by electron microscopy with extended results. This paper also describes some observations on the surface disturbances prior to sectioning. These observations are relevant to a suggested theory of fatigue cracking. REVERSED SLIP MOVEMENTS Slip movements in fatigue deformation must reverse direction in each cycle. The question arises: DO the "backward" and "forward" movements take

Jan 1, 1962

By E. M. MacKevett

The only source of uranium ore in Alaska that has been mined commercially is the Ross-Adams de- posit, a gently inclined, fusiform orebody in alkali granite in which uranothorite and uranoan thorianlte are the chief ore minerals. In mode of occurrence, apparent genetic association with the granite, and to a lesser extent in mineralogy, this type of deposit is uncommon. The mine is in the southern part of Prince of Wales Island (Fig. 1) at an altitude of about 950 ft on the southeast flank of Bokan Mountain. A steep unpaved road 1 ¾ miles long leads to the dock on the West Arm of Kendrick Bay, which can be reached by boat or seaplane from Ketchikan, some 35 miles to the northeast.

Jan 9, 1959

NEW MEMBERS. The following list comprises the names of those persons who became members during the month of September, 1913: Members. ANDERSON, ANDREW P., Min. Engr 908 Story Bldg., Los Angeles, Cal. ANDROS, STEPHEN 0., Min. Engr University of Illinois, Urbana, Ill. BECKETT, PERCY G., Min. Engr Globe, Ariz. BLAIR, THOMAS S., JR., Prest. Blair Engrg. Co 343 S. Dearborn St., Chicago, Ill. BOYLE, HARRY, Min. Engr S07 Lowman Bldg., Seattle, Wash. BRADEN, EUGENE B., Vice-Prest., Selby Smelting & Lead Co., Merchants Exchange Bldg., San Francisco, Cal. CHALMERS, JOHN W., Min. and Elec. Engr., Morro Velho, Villa Nova de Lima, Honorio Becalho Minas Geraes, Brazil, So. America.

Jan 10, 1913

By P. H. Mell

AMONG the minerals exhibited at the Atlanta Exhibition of 1881, soapstone, kaolin, and asbestos were well represented. The first two occur in large quantities, of very pure quality, throughout the South. The last is somewhat limited in amount, yet in certain localities it exists in masses sufficiently large to pay for working; in North Carolina, Georgia, and Alabama it has been mined with some profit. I would, in this paper, call special attention to the minerals soapstone and kaolin, because their many valuable qualities seem to have been al most entirely overlooked by our Southern manufacturers. Steatite, particularly, occurs in such large quantities, and generally in such close proximity to the great iron regions of Alabama and Georgia, that it is amazing that the iron companies will persist in sending abroad under. heavy expense for firebrick. It would require a much smaller sum of money to quarry this rock and place it at the various furnaces ; and the results obtained, I am sure, would prove its superiority over the majority of firebrick brought into this region. Soapstone, as well as kaolin, is found throughout the metamorphic regions of Alabama, Georgia, South Carolina, and North Carolina. Below-will be found seven analyses that I have made of this mineral, taken from various points in the four States above mentioned. I have also subjected these same specimens to severe fire-tests, and the results were very satisfactory. The tests were conducted in the following manner: Small portions of the compact variety were carefully weighed and placed in a Fletcher's new crucible furnace for gas, and subjected for half an hour to a heat that will in 12 minutes fuse iron. The only effect upon these specimens was a slight change in color .to a darker shade, a small loss in weight, due evidently to the evaporation of water, and, in one or two specimens, a slight degree of fusion on the sharp edges. The first specimen subjected to investigation was taken from a large outcropping in Tallapoosa County, Alabama. Specific gravity, 2.88 ; hardness, 1.9; color, blue gray. Composition Water, - 2.68 Silica, - 65.46 Iron oxide, - 2.10 Alumina, - 15.02 Magnesia, - 15.35 100.61

Jan 1, 1882

By Thomas Egleston

The process of lixiviating silver ores, which do or do not contain gold, by means of hyposnlphite of soda is likely to assume a very great importance in the West, the conditions being such that while it is applicable to very rich ores which do not contain lead enough to smelt, it is also equally applicable to many ores that are either too poor or too impure to be treated by any other process. Western ores are generally divided into four classes: those which contain copper enough to be smelted for copper, from which the gold and silver is extracted in the wet way, as is the practice of the Boston and Colorado works; those in which there is a large quantity of lead, which can be smelted for lead, and the gold and silver extracted from it; ores in which there is neither copper nor lead enough to allow of a process of smelting, but which can be treated in pans, these ores being " free milling " if they require no metallurgical treatment, or '(rebellious" if they have to be roasted with or without the addition of salt; and ores which do not contain enough either of lead or copper for smelting, which are poor both in silver and gold, contain large amounts of sulphur, arsenic, and antimony, and cannot be treated in many places in the West by any of these processes. Roasting with salt would convert the base metals as well as the silver into chlorides, and would give in the amalgamation a very base bullion, and the expense of the process would be SO great that the margin of profit would be very small, the reason being that for the ordinary process of pan-amalgamation, which is the only one suitable for ores containing small amounts of the base metals, and poor in silver and gold, the cost of a plant for milling is so large as not to justify the expense of treating such ores. The electrolytic processes which have been partially successful in Europe have not been tried 'here. While in the near future they will undoubtedly be used, it is hardly possible to consider them now.

Jan 1, 1884

By Thomas Harris

This paper. was written in conjunction with the work being undertaken by the Technical Committees on Classification of Coal, and an effort has been made to compile information relative to the use of coal for stationary steam generation in order to use this information to assist the Committee on Classification of Coal for the ultimate purpose of elimination of losses both by the' reduction of indivi-dual effort and waste in the consumption of material. Under the auspices of the National Association of Purchasing Agents, a questionnaire was drawn up to develop this information from stationary steam plants throughout the United States. in order to consolidate the information de-veloped from the many hundreds of boiler tests on coals consumed by various coal¬burning equipment. These questionnaires covered: 1. The company reporting, location and method of delivery to the plant. 2. Complete coal date, including description of coals used (with. sufficient space to- include first, second and third, preference) on--source of coal used,- complete-analysis and factors affecting choice of, coal used. 3. Plant data, divided into - A. Hand fired, B. Overfeed stokers,. . C. Underfeed stokers, D. Traveling grate stokers, E. Pulverized coal, and included complete description of furnace data, draft data, coal-burning rate, type of stoker, type of pulverizer, efficiency date and remarks.

Jan 1, 1933

By W. T. Allan

RAW bituminous coal has been in general use as a blast-furnace fuel in Scotland for the last century, and although its use has now been largely abandoned and it has been replaced by coke in the majority of the few furnaces which are at, present in blast in this country, coal-smelted pig iron is not yet a thing of the past; it is still being produced and mar-keted in competition with the more cheaply smelted product of the coke-fired furnace. Various factors have influenced this change in practice; the once plentiful deposits of coal of a suitable nature for the blast furnace are now not so easily obtainable; native blackband and clayband ironstones which are easily smelted in the coal-fired blast furnace, although still far from being exhausted, are not available except at a. cost that is somewhat higher than that of imported ores, making them unattractive to the ironmaster that is compelled by circumstances to smelt his iron at the lowest possible cost. Within the last 15 years overproduction of synthetic nitrogen has led to progressive reductions in the price of sulphate of ammonia, the recovery of which together with the other by-products before that time materially assisted in reducing the working costs of the coal-fired furnace. Now the sale of the by-products recovered yields a diminished profit. When the cost of the product is the only consideration the small, slow-smelting, coal-fired blast furnace cannot compare with its large, modern, coke-fired competitor. Other `considerations do not by any means all support the same side of the argument. In the smelting of pig iron to be used in the manufacture of steel where the quality of the final product depends so largely upon the control of the conversion process and so much less upon the physical quality of the pig iron used, the physical properties of the pig iron do not exert any appreciable influence upon the quality of the steel produced, therefore the methods employed in the smelting of the pig iron matter but little so long as the requisite chemical composi-tion is reached. On the other hand, in ironfounding where the simple melting of the pig iron, which is the only treatment it receives before being cast into its final form, does little or nothing to modify its original charac-

Jan 1, 1937

By L. A. Willey

IN 1953, a method for filtering a liquid phase from solid phases while in equilibrium at elevated temperatures was devised at the Alcoa Aluminum Research Laboratories. Since then, it has been applied to the investigation of liquid-solid equilibrium in metallic systems. In application, the method simplifies the centrifuge filt.ration procedure as developed by Scheil and described by Gebhardt Fig. 1 shows a sketch of the filtering apparatus located within a thermal analysis furnace. It consists of a stainless steel filter crucible A, into the bottom of which a porous carbon filter disk B, 1 3/4 in. diam by 1/4 in. thick, is sealed to the shoulder and rim with carbonaceous cement. The base of the filter crucible, machined to an angle, fits into a tapered seat at the mouth of a stainless steel vacuum chamber C. A connecting tube from the vacuum chamber to a vacuum line also serves as a means for supporting the apparatus from the base of the furnace. An alundum crucible D of 25 ml capacity is placed with- in the vacuum chamber below the filter for collecting the filtrate. Two thermocouples E, in stainless steel protection tubes, which extend from 1/16 to in. above the center of the filter, are mounted on the rim of the filter crucible. One thermocouple is used in differential connection with the furnace control thermocouple to regulate rates of heating and cooling. The other serves as a means for recording the temperature of the alloy prior to filtering. A suitable mold coating is used on exposed surfaces of stainless steel parts to guard against attack upon these parts as well as to avoid contamination of the alloy samples. A mold wash prepared from precipitated CaCO, is suitable for aluminum alloys. The porous carbon for the filter disks and the carbonaceous cement, grade 200 (graphite base), were obtained from the National Carbon Co. Porous car-bon, grade Nos. 10 to 60, has been employed. Grade No. 40, however, appeared to give the optimum advantages in operation. In operation, an alloy sample is remelted and heated to about 50°C above its liquidus temperature. At the same time, the filter apparatus is preheated to about the same temperature. The alloy then is cast into the filter crucible.

Jan 1, 1957

By Edgar Stansfield

ONE of the most striking features of the coal series passing from peat through brown coal, lignite, etc., up to anthracite is the gradual reduction of moisture content with the increased coalification of the original plant material. Thus drained peat from a bog may contain 90 per cent water, brown coal contain 50 per cent, lignite 30 per cent, while a bituminous coal may contain only 1 per cent moisture. Moisture, therefore, is one of the important factors to be considered in coal classification, especially with the lower rank coals. With bituminous and higher rank coals the moisture content is less satisfactory for classification; it may even pass a minimum value and then increase with increasing rank to anthracite and superanthracite. Coal in an undisturbed seam contains moisture which is an integral part of the coal, but it may also be wet with free, underground water percolating through the seam. Only the former must be considered in evaluating the moisture content of the coal for classification purposes; this will be called the "true moisture" of the coal. When the seam is mined and sampled the sample taken may show the true moisture; on the contrary, it may contain in addition free mine water or, especially in dry, well ventilated mines, it may contain less than the true moisture. Coal contains unstable organic compounds which may decompose, with the production of moisture, when the coal is exposed to air at ordinary temperatures, or is heated with or without exposure to air. The potential moisture of a coal therefore is higher than its actual moisture. The lower the rank of the coal, the greater its instability, as a rule, and the greater the care necessary to avoid oxidation or decomposition in any investigation of moisture content. The majority of coal workers have preferred, on account of the difficulty in evaluating the true moisture of a coal, and for other reasons, to classify coals by analyses calculated to the dry-coal basis. A number of workers familiar with lower rank coals have recently insisted that the classification of such coals can be satisfactory only if analyses on the moist-coal basis are employed. The moisture-holding capacity of coal is therefore intimately connected with coal classification, and in this paper a procedure is outlined for determining the true moisture of a coal.

Jan 1, 1932

By P. E. Senseny

INTRODUCTION Massive hydraulic fractures have been used since 1949 in the petroleum industry to enhance production rates and increase recoverable reserves. Currently, a research program, the Multi-Well Experiment, is underway to develop the understanding and technology to a1 low economic production of the large gas reserves of the low permeability, lenticular sandstone formations in the western U.S. (Atkinson, et al, 1981; Northrop and Sattler, 1983). Use of state- of-the-art hydraulic fracturing techniques is a part of this investigation. As a portion of an extensive core program in support of this experiment (Sattler, 1983), fracture toughness has been determined for 56 sandstone, shale, mudstone, or siltstone horizons from three wells in the Piceance Basin. The role of fracture toughness in hydraulic fracturing is not well understood because other factors, such as in situ stress, dominate fracture geometry and containment. Rubin (1983) concluded from analysis of his laboratory hydrofracture experiments that fracture toughness should be included in design and numerical simulation of hydraulic fractures. However, van Eekelen (1982) contends that the stress intensity at the crack front should be so much greater than the fracture toughness of the rock that toughness can have no importance. Generally, fracture toughness and other material properties, such as elastic moduli and permeability, are thought to be of secondary importance in determining fracture geometry and containment. In spite of this, there is a need to acquire a more quantitative understanding of their importance for accurate design and simulation calculations. Analysis of fracture geometry and containment data from hydraulic fracturing experiments carried out in formations where fracture toughness and other rock properties are

Jan 1, 1984

By Arthur Phillips, E. S. Davenport

The purpose of this paper is to present certain data and observations resulting from a series of experiments dealing with the heat treatment and microstructure of commercial white cast iron and its derivative, malleable iron. In planning the experimental work, particular pains were taken to secure for the tests white cast iron of "normal" composition; i.e., within the composition limits commonly prescribed by manufacturers of malleable castings. A review of the literature leads us to believe that much data of a fragmentary character treating of the graphitization of white cast iron have been of little value, mainly because of the diversity in chemical composition of the materials employed in the tests. Moreovcr, when feasible, annealing periods at least comparable to those of current practice have been adopted. We wish to acknowledge our indebtedness to the members of the research department of the Eastern Malleable Iron Co. for the white cast iron used in the test's and, particularly, for their active cooperation during the experimental stage of the work. In this paper the following subjects will be discussed in the order indicated: Data on the thermal critical points of white cast iron and malleable iron. Changes produced in tensile properties and microstrue.-ture of white cast iron by annealing at different temperatures within the, range, 760 to 1100° C. Relation of thickness of wall section of hard iron to microstructure and tensile properties of malleable iron obtained under normal annealing conditions. Notes on mechanics of graphitization of normal white cast iron as observed in specimens quenched after various periods of anneal at approximately 800" C.

Jan 1, 1922

By Arthur Phillips, E. S. Davenport

The purpose of this paper is to present certain data and observations resulting from a series of experiments dealing with the heat treatment and microstructure of commercial white cast iron and its derivative, malleable iron. In planning the experimental work, particular pains were taken to secure for the tests white cast iron of "normal" composition; i.e., within the composition limits commonly prescribed by manufacturers of malleable castings. A review of the literature leads us to believe that much data of a fragmentary character treating of the graphitization of white cast iron have been of little value, mainly because of the diversity in chemical composition of the materials employed in the tests. Moreovcr, when feasible, annealing periods at least comparable to those of current practice have been adopted. We wish to acknowledge our indebtedness to the members of the research department of the Eastern Malleable Iron Co. for the white cast iron used in the test's and, particularly, for their active cooperation during the experimental stage of the work. In this paper the following subjects will be discussed in the order indicated: Data on the thermal critical points of white cast iron and malleable iron. Changes produced in tensile properties and microstrue.-ture of white cast iron by annealing at different temperatures within the, range, 760 to 1100° C. Relation of thickness of wall section of hard iron to microstructure and tensile properties of malleable iron obtained under normal annealing conditions. Notes on mechanics of graphitization of normal white cast iron as observed in specimens quenched after various periods of anneal at approximately 800" C.

Jan 1, 1922

By C. W. Kovach, A. Moskowitz

Studies were undertaken to investigate the effects of manganese content on the machinability and other Properties of a free machining martensitic stainless steel (AISI Type 416). Machinability was found to be significantly improved in steels of high manganese content, and a direct relationship was obtained between machinability and steel Mn:S ratio. As the manganese content of the steel increases, the sulfide Phase present changes from CrS to (FeMn)Cr2S4 to (MnFeCr)S, and finally to MnS. The average sulfide inclusion hardness decreases through the same range of increasing manganese content. The mechanism for machinability improvement is discussed in terms of a soft ductile sulfide affecting deformation in the secondary shear zone. Type 416 containing relatively high manganese for improved machinability shows good general properties. The effects of increasing manganese content on mechanical properties, cold formability, and corrosion resistance are described. THE addition of sulfur is commonly used to improve the machinability of stainless steels. However, little attention has been paid in the past to the composition and characteristics of the sulfur-containing phase or phases present in these resulfurized steels. Recent information on the properties of sulfide phases, and their role in metal cutting, suggests that variations in these phases could have critical effects on machin-ability, as well as important effects on formability and other properties such as corrosion resistance. Manganese, chromium, and iron are strong sulfide forming elements present in stainless steels! of these, manganese has the greatest sulfide forming tendency and iron the least.1"1 The manganese content of resul-furized 13 pct Cr steels, often about 0.5 pct, can be insufficient or only barely sufficient to combine with the sulfur that is present; thus, the precise level of manganese can strongly influence the nature of the sulfide phase. Sulfide phases which may be present in stainless steels have been reported to include CrS, a spinel-type sulfide, chromium-rich manganese sul-fide, and manganese Sulfide.5,6 Detailed phase relationships for the Fel3Cr-Mn-S system have been reported by the present investigators,7 and a portion of this work will be referred to subsequently in this paper. Recent work by Kiessling6 and Chao et a1.8 has shown that sulfide phases can display wide variations in hardness, and may undergo considerable plastic deformation under isostatic loading.9-12 Early theories of metal cutting attributed the influence of sulfur to a lubricating effect. It is now apparent that the influence of the nonmetallic inclusions and their properties on crack initiation, deformation in the shear zones, and boundary films must also be considered in relation to the machining process. This paper presents the results of studies conducted to relate machinability to the various sulfide phases which occur in stainless steels. This work has led to the development of alloys with improved machinability, and has generated information on the effects of inclusions on metal cutting processes. Effects of sulfide inclusions and steel composition on other important metallurgical properties are also discussed. MATERIALS For drill machinability and inclusion studies, 10 lb laboratory heats were melted in an air induction furnace. These heats were made with sulfur contents be tween 0.10 and 0.50 pct and manganese contents be tween 0.05 and 3.0 pct. Residual elements were added to the heats in amounts typical for commercial steels. The typical compositional range covered by the heats is shown below: C Mn P S Si Ni Cr Mo Cu N 0.10 0.05 0.007 (M0 0.40 0.40 13.0 0.20 0.10 0.03 3.0 0750 The laboratory ingots were forged in the temperature range of 1800" to 2100°F to 3/4-in. sq bars, and all bars tempered to a hardness aim of 200 Bhn prior to testing. Because of differences in composition and tempering response, the tempered bars showed some variation in hardness (175 to 275 Bhn) as well as variations in delta ferrite content (0 to 50 pct). Composition, hardness, and delta ferrite content were considered in the analysis of the machinability data. Additional tests involving tool-life evaluation and determination of other properties were conducted on materials from commercially melted and processed 15-ton electric furnace heats. TESTS AND PROCEDURES Machinability of the laboratory heats was evaluated in a drill test. In this test, 1/4-in. diam holes, 0.4 in. deep, were drilled alternately in a test bar and in a standard bar for a total of four holes in each. This sequence was repeated three times using a freshly sharpened drill each time. The average time required to drill a hole in the test bar was compared to that for the standard bar. A drill machinability rating was assigned to the test bar relative to a rating of 100

Jan 1, 1970

(Members are urged to send in for this column any notes of interest concerning themselves or their fellow-members.) Members and guests who called at Institute headquarters during the period August 1, 1916 to September 10, 1916: C. L. Cantley, New Glasgow, N. S. H. M. La Follette, La Follette, Tenn. D. A. Cowell, Columbus, Ohio. Montrose L. Lee, Montevideo, Uruguay. Alexander Deussen, Houston, Texas. V. H. McNutt, Billings, Mont. Chas. E. Dutton, Goldfield, Nev. J. W. Maller, New York, N. Y. H. S. Emlaw, Grand Haven, Mich. Edwin W. Mills, Tul. Mi Chung, Chosen, J. M. Gillette, Swatsburg, N. Y. Korea. E. Gorilla, San Antonio, Texas. Francis R. Pine, Elizabeth N. J. Bertram Grant, Kingman, Arizona. Frank A. Ray, Columbus, Ohio. Ruger W. Hay, Bisbee, Arizona. John A. Rice, El Paso, Texas. C. F. Hendricks, Cobalt, Ontario. W. E. Rice, Ringwood Manor, N. J. Stanley C. Herold, San Jose, Cal. W. H. Staver, Lynchburg, Va. Lloyd Hoffman, Pottersville, N. J. Ralph H. Sweetser, Easton, Pa. Charles Hunter, London, England. Kirby Thomas, New York, N. Y. G. Jansen, Benkoelen, Sumatra. Henry Traphagen, Union Hill. T. H. Jenks, Oatman, Arizona. M. M. Valerius, Tulsa, Okla. Warren jenny, Chanaral, Chile. Wilfrid B. Wainewright, London, Eng. Walter A. Barrows, Jr., of Brainerd, Minn., has been elected president and general manager of the Thomas Iron Co., Easton, Pa., to succeed Ralph H. Sweetser, whose resignation of several months ago becomes

Jan 10, 1916

By George S. Koch

Since 1882, world zinc production has increased. In contrast, US zinc production rose until about 1915, but since then has remained nearly constant, with a slight tendency to decrease. Production from the Tri-State district, the largest early source of zinc in the US, has gone down steadily; this decline has been balanced by a growth in the rate of other districts. These changes in US production are due to economic, not geological, factors. Recent exploration has located large minable ore bodies: additional deposits will undoubtedly be found in the stratabound carbonate rock and volcanogenic environments. A statistical analysis of the exploration effort in the Middle Tennessee district indicates that new discoveries can be expected there. Thus, the US is in an early stage of the production cycle for zinc. Of major mining districts in the US, only the Tri-State is exhausted under current economic conditions; large zinc resources of low-grade material, which would repay mining at higher prices or improved technology, are known to exist in that district .

Jan 1, 1982

By Renato G. Bautista, Theodore D. Tiemann

A kinetic study of the hydrogen reduction of taconite from the Wisconsin Gogebic range was made over the temperature range from 500° to 1000°C on eleven size fractions from 4 to 150 mesh. Two stages of reduction were observed, a rapid initial reaction followed by a slower reaction presumably taking place at an internal receding FexO-Fe interface. Calculated mean activation energies for the two reactions were 7800 and 14,600 cal per mole respectively. In recent years there has been an increased interest in the direct reduction of iron oxide ores to metallic iron by means of gaseous reducing agents such as hydrogen and carbon monoxide.1,2 These investigations have been motivated by the desire to develop a process that will by-pass the blast furnace in the production of steel. The majority of these processes have been developed to produce metallic iron by direct reduction from high-grade iron oxide ores.3"5 Very little work has been done on the low-grade siliceous iron oxide ores.6"8 The work reported here is directed principally towards the fundamental aspect of the reduction reactions of siliceous iron oxide ores, since the practical aspects of the gaseous reductant process were discussed previously. The ore used in the investigation was obtained originally from the United States Bureau of Mines10 trench sample of the Yale member of the Wisconsin Gogebic range iron formation. The Yale taconite has an average analysis of 28.2 pct Fe and approximately 50 pct SiO2. Chemically, these nonmagnetic taconites contain on the average about 53 pct silica and 30 pct Fe. An average analysis calculated fron the USBM10 figures for a composite of the five members (Norrie, Plymouth, Pence, Pabst, and ale) of the iron formation is given in Table I. Mineralogically, based on previous X-ray diffraction and other studies, the principal minerals are hematite (Fe2O3), geothite (Fe2O3.H2O), and quartz (SiO2). Minor amounts of iron containing silicates, siderite (FeCO3) and magnetite (FeO. Fe2O3) are present.10,11 The iron minerals and the quartz are finely disseminated requiring extremely fine grinding for liberation. For the experimental work, the ore sample was screened into a number of size fractions, the analyses and densities of which are given in Table II. EXPERIMENTAL PROCEDURE The reduction experiments were carried out in a 24 in. by 2 in. ID nichrome-wound vertical-tube furnace mounted on a stand. A 1 1/2 in. OD zirconium-oxide combustion tube was used inside the furnace to contain the atmosphere. To the top of this combustion tube was joined a pyrex ground-glass joint to which was attached a glass bulb with a small (1.0 mm) opening at the center, and with two outlets controlled with a stopcock on each side. A pyrex-glass joint with connections to three stopcock joints for introducing hydrogen, nitrogen, and mixtures of hydrogen and nitrogen gas was joined to the tapered bottom of the combustion tube. The sized ore fractions were contained in a 1 in. diameter by 1 1/2 in. 150-mesh nickel screen basket. The basket was suspended in the furnace from a balance by means of a supporting nickel wire which hung freely inside the combustion tube. The furnace temperature was controlled by a Leeds and Northrup Speedomax Type G controller, connected to a chromel-alumel thermocouple placed

Jan 1, 1962

By Nicholas J. Grant, W. Michael Yim

The creep-rupture properties of nickel, in as-prestrained or prestrain-polygonized condition, were studied at 1300°F and 4000 psi, and also at 700°F and 26,000 psi. An improvement of strength was noted in both the as -prestrained and the prestrain-polygonized tests at each temperature. The as-prestrained tests, however, showed superior creep resistance to the prestrain-polygonized ones. From the results of X-ray and etch-pit studies, the strengthc gain was interpreted in terms of dislocation density and the stability of preformed substructures. COLD work is known to improve the strength properties of metals at low temperatures. At high temperatures, however, the strength improvement is often lost if gross structural changes, such as re-crystallization, take place prior to or during the test. Even in the absence of recrystallization, a prestrained metal may undergo structural changes— polygonization and the formation of well-defined subgrains—which importantly effect the resultant properties. The relationship between substructure and creep properties has received considerable attention in recent years. The work of wood1 indicated that the creep strength of aluminum and its alloys was closely related to the subgrain size. Hazlett and Hansen,2 and Ancker, Hazlett, and parker,3 working with nickel and nickel alloys, had shown that small amounts of prestrain at room temperature followed by a recovery anneal at 800°C (1470°F) improved the strength at both low and high temperatures. The strength gain was attributed to an increase in the number of subgrain boundaries as a result of the prestrain-polygonization treatment. More recently Coldren and Freeman4 studied the effect of substructures on the creep rate of nickel at 1550°F. Their conclusions indicated that the substructure size as measured by the number of boundaries was the factor that controlled the creep rate. In addition, the perfection of the subgrain boundary has been indicated to have an important role on the strength.' On the other hand, there are data which disagree with the above observations. Grant, Chaudhuri, Silver, and Ganow6 found no creep strength improvement by a prestraining treatment. In reviewing the role of subgrains on high-temperature creep, Shepard and Dorn7 concluded that the contribution of the subgrains to high-temperature creep strength was a minor one. Guard,8 in a recent study on poly-gonized nickel, has cast doubt on the validity of the postulate that subgrain size controls the creep rate. In the majority of the previous studies, the subgrain boundaries have been singled out as the most important factor in determining creep strength; however, there is no firm theoretical ground for the postulate that the subgrain boundaries act as effective barriers to dislocation motion.B910 Little effort has been directed toward the study of the relationship between creep strength and other structural variables, such as dislocation density, lattice strain,

Jan 1, 1963