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By Alden B. Greninger

Many recent contributions in the field of theoretical metallography have been concerned with crystallographic definitions or descriptions of various phenomena. The lattice orientation of the crystal being studied must be known before such definitions can be made. Practically all the metallic crystals used do not have crystal faces—other than the unknown "plane of polish"; hence resort must be had to other means of determining orientations. Some use has been made of etch-figures, slip bands, optical properties, etc., for this purpose; but for accurate results, and because of the fewer restrictions to their use, the various X-ray methods have been the most satisfactory.' The methods that have been used may be divided into two general classes: (1) oscillation methods, and (2) transmission Laue methods.² The disadvantages of these methods are numerous, chief among them being the time required to determine a complete orientation. No method proposed so far is wholly satisfactory for determining the orientation of a small macrograin within a polycrystalline aggregate.

Jan 1, 1935

By Alden B. Greninger

Many recent contributions in the field of theoretical metallography have been concerned with crystallographic definitions or descriptions of various phenomena. The lattice orientation of the crystal being studied must be known before such definitions can be made. Practically all the metallic crystals used do not have crystal faces—other than the unknown "plane of polish"; hence resort must be had to other means of determining orientations. Some use has been made of etch-figures, slip bands, optical properties, etc., for this purpose; but for accurate results, and because of the fewer restrictions to their use, the various X-ray methods have been the most satisfactory.' The methods that have been used may be divided into two general classes: (1) oscillation methods, and (2) transmission Laue methods.² The disadvantages of these methods are numerous, chief among them being the time required to determine a complete orientation. No method proposed so far is wholly satisfactory for determining the orientation of a small macrograin within a polycrystalline aggregate.

Jan 1, 1935

By K. E. Gray

The status of rock mechanics as applied to petroleum production might be termed, "Rock Mechanics-A New Name for Old Problems." The petroleum industry's efforts, from its earliest days, have been concerned with rocks, hopefully containing hydrocarbon accumulations in economic quantities. Geophysical and geological studies, wildcat and development drilling procedures, well bore mechanics and reservoir engineering operations, and certain aspects of production operations involve rock mechanics in various ways. Stress states and temperatures of interest range from low values in surface or near-surface activities, to very high values encountered at depths now exceeding 25,000 ft; deeper and deeper drilling will continue to increase this range. Time scales vary from a few microseconds in wave propagation measurements and some aspects of rock behavior during drilling, to seconds, minutes or hours for other drilling and well bore mechanics problems, to several years during which the efficient and economical depletion of reservoir systems is achieved. Subsurface sedimentary formations contain various fluids, of course, and reservoir fluid movement commonly involves three-dimensional, three-phase (oil, gas, and water) fluid flow. Many extremely difficult problems in rock mechanics arise for the Petroleum Engineer because of fluid movement (or lack of desired movement) in a well bore or reservoir. The discussion to follow illustrates just a few of the many topics in rock mechanics of significance to the petroleum industry. Time precludes anything other than a superficial treatment of the topics mentioned. A great deal of work has been carried out by various research groups in the petroleum field and significant efforts are continuing, as a review of the technical literature will reveal.

Jan 1, 1968

By Strathmore R. B. Cooke, Thomas E. Bam

The paper discusses the mineralogy, structure, and strength of magnetite pellets fired in air and in a neutral atmosphere at various temperatures. The information obtained from this investigation is used to explain the origin of the structures occurring in pellets produced by pilot-plant operation. MUCH experimental work has been performed on i-VL the mechanism of agglomeration and pelletiz-ing of moist ore and concentrates and on the process of firing agglomerates, but except for the work of Tigerschiold and Ilmonil much of the published information is empirical, and the literature contains no information concerning the structure of fired pellets. Results of a preliminary study of the micro-structures occurring in pellets produced both in the laboratory and on a pilot-plant scale are presented in this paper. Most of the results were obtained from pellets prepared from Mesabi magnetic taconite, but through the courtesy of the staffs of the Minnesota Mines Experiment Station and the Bethlehem Steel Co., fired pellets produced from limonite and hematite ores and from Lebanon magnetite have also been examined. The work has been restricted almost entirely to pellets produced without additives, the exceptions being those in which coal was added to the filter cake before rolling. Schwartz has described the microstructures occurring in ore sinters produced under reducing conditions.' Many of the structures and constituents he describes are common to fired pellets, but the constituents normally occur in markedly different proportions. His statement that "in all satisfactory sinter the amount of hematite is small, perhaps not over 2 or 3 per cent" is inapplicable to pellets produced by pilot plant operation or by any process in which air is not deliberately excluded. Pilot plant pellets contain over 90 pct by weight of hematite, and those produced in the smaller furnaces of the Minnesota Mines Experiment Station contain more than 80 pct of that constituent. Preparation of Specimens It is difficult to examine unfired pellets microscopically because of their insufficient coherency to withstand sectioning and polishing. Fired pellets sometimes lack coherency and frequently contain holes which are troublesome during polishing. Impregnation of both air-dried and fired pellets is readily accomplished by the use of methyl metha-crylate monomer." The dry pellets are covered in a test tube with excess monomer, to which a small amount of accelerator has been added. When the test tube is placed in a cooling bath and evacuated with an aspirator, most of the entrapped air is removed, and disruption of weak pellets by boiling of the monomer is reduced to a minimum. Polymerization is then effected by immersion of the test tube in a water-bath at about 45"C, this temperature being held for 4 or 5 days. The test tube may then be broken away from the solidified mass and the pellets sectioned by a carborundum wheel or a diamond saw. Where time is important, impregnation is carried out at a higher temperature by Meyer's method.' Air-dried pellets must be impregnated with especial care; otherwise swelling occurs and the solids are displaced. It is more important to be certain that the monomer forms a reasonably complete network throughout the specimen than that all entrained air is removed, and for this reason the vacuum technique may be omitted. Impregnated agglomerated products and pellets are extremely coherent, section well, and may be polished either by hand or by machine. Hand polishing is not satisfactory for the examination of conditions existing at the boundaries of grains, and for this machine polishing must be used. The Graton-Vanderwilt machine gives excellent results, provided that pressure on the specimen is considerably in excess of that recommended by the manufacturer. Mineralogy of Fired Pellets Only two opaque iron minerals, magnetite and hematite, have been recognized in pellets. The complete identity of, these artificial minerals with their corresponding natural counterparts is shown by their mineralographic characteristics and their X-ray structures. Wiistite has not been found. Slag is the most common transparent constituent of fired pellets. Occasionally conditions have been appropriate for the crystallization of fayalite from the slag, and at other times another crystalline sil-

Jan 1, 1953

By Strathmore R. B. Cooke, Thomas E. Bam

The paper discusses the mineralogy, structure, and strength of magnetite pellets fired in air and in a neutral atmosphere at various temperatures. The information obtained from this investigation is used to explain the origin of the structures occurring in pellets produced by pilot-plant operation. MUCH experimental work has been performed on i-VL the mechanism of agglomeration and pelletiz-ing of moist ore and concentrates and on the process of firing agglomerates, but except for the work of Tigerschiold and Ilmonil much of the published information is empirical, and the literature contains no information concerning the structure of fired pellets. Results of a preliminary study of the micro-structures occurring in pellets produced both in the laboratory and on a pilot-plant scale are presented in this paper. Most of the results were obtained from pellets prepared from Mesabi magnetic taconite, but through the courtesy of the staffs of the Minnesota Mines Experiment Station and the Bethlehem Steel Co., fired pellets produced from limonite and hematite ores and from Lebanon magnetite have also been examined. The work has been restricted almost entirely to pellets produced without additives, the exceptions being those in which coal was added to the filter cake before rolling. Schwartz has described the microstructures occurring in ore sinters produced under reducing conditions.' Many of the structures and constituents he describes are common to fired pellets, but the constituents normally occur in markedly different proportions. His statement that "in all satisfactory sinter the amount of hematite is small, perhaps not over 2 or 3 per cent" is inapplicable to pellets produced by pilot plant operation or by any process in which air is not deliberately excluded. Pilot plant pellets contain over 90 pct by weight of hematite, and those produced in the smaller furnaces of the Minnesota Mines Experiment Station contain more than 80 pct of that constituent. Preparation of Specimens It is difficult to examine unfired pellets microscopically because of their insufficient coherency to withstand sectioning and polishing. Fired pellets sometimes lack coherency and frequently contain holes which are troublesome during polishing. Impregnation of both air-dried and fired pellets is readily accomplished by the use of methyl metha-crylate monomer." The dry pellets are covered in a test tube with excess monomer, to which a small amount of accelerator has been added. When the test tube is placed in a cooling bath and evacuated with an aspirator, most of the entrapped air is removed, and disruption of weak pellets by boiling of the monomer is reduced to a minimum. Polymerization is then effected by immersion of the test tube in a water-bath at about 45"C, this temperature being held for 4 or 5 days. The test tube may then be broken away from the solidified mass and the pellets sectioned by a carborundum wheel or a diamond saw. Where time is important, impregnation is carried out at a higher temperature by Meyer's method.' Air-dried pellets must be impregnated with especial care; otherwise swelling occurs and the solids are displaced. It is more important to be certain that the monomer forms a reasonably complete network throughout the specimen than that all entrained air is removed, and for this reason the vacuum technique may be omitted. Impregnated agglomerated products and pellets are extremely coherent, section well, and may be polished either by hand or by machine. Hand polishing is not satisfactory for the examination of conditions existing at the boundaries of grains, and for this machine polishing must be used. The Graton-Vanderwilt machine gives excellent results, provided that pressure on the specimen is considerably in excess of that recommended by the manufacturer. Mineralogy of Fired Pellets Only two opaque iron minerals, magnetite and hematite, have been recognized in pellets. The complete identity of, these artificial minerals with their corresponding natural counterparts is shown by their mineralographic characteristics and their X-ray structures. Wiistite has not been found. Slag is the most common transparent constituent of fired pellets. Occasionally conditions have been appropriate for the crystallization of fayalite from the slag, and at other times another crystalline sil-

Jan 1, 1953

By W. Rostoker, A. Siede

THE venerable problem of hydrogen embrittlement of ferritic iron lacks as yet a complete explanation. Possibly part of the difficulty has been the exclusive preoccupation with the total ductility prior to fracture. In the past few years it has been noted at least twice1,2 that hydrogen charged into iron has the ability to depress the upper yield point and, at room temperature, to eliminate completely the discontinuous yield phenomenon. Cracknell and Petchl rationalize that the depression of the yield stress is an example of the behavior of inhomogeneous stresses. Their explanation requires that microcracks exist in the annealed metal, and that hydrogen collect in these cavities under high hydrostatic pressure. The hydrostatic pressure of hydrogen generates localized tensile stresses in the iron which, with external loading, reach the critical stress for yield prematurely. The local plastic zones will spread across the specimen before the Lüders bands can be generated, and the yield-point elongation phenomenon is eliminated. This viewpoint will be discussed in succeeding paragraphs. Rogers,2 on the other hand, represents the depression of the initial flow stress as a result of the interaction of hydrogen with dislocations. He submits two alternative modes of interaction. In the

Jan 1, 1959

By P. K. Koh

Chi phase (body-centered cubic, a = 8.89A) was found in as-cast 23 pct Cr-10 pct Mo-Fe alloy as well as in heat-treated 316, 316L, 317, and modified 446 stainless steels. Chi phase resembles sigma phase in its metastability, chemical composition, and brittleness. Microstructure and some of physical properties of chi phase were developed. MOLYBDENUM has been established as a desirable alloying element for the enhancement of corrosion resistance in Cr-Ni steels and creep and rupture strength in high temperature alloys. On the debit side, however, the molybdenum addition has been known to stimulate u formation. When the molybdenum-bearing steels were subjected to prolonged heating at elevated temperatures, losses of corrosion resistance and/or ductility have been observed. Andrews1,2 first found the existence of a new phase among the anodic FeC13 extracts from type 316 stainless steel solution treated and then reheated from 800" to 1100°C. This phase was designated x and was identified by diffraction patterns as of body-centered cubic structure with a value equal to 8.89? and similar to that of a manganese. He found that the x phase in this steel always coexisted with s phase, but failed to distinguish one from the other by metallographic technique. No definite conclusion was drawn regarding the equilibrium temperature ranges of these two phases. The appearance of Andrew's work recalled an un- explained structure observed several years ago at the Allegheny Ludlum Research Laboratories during the investigation of an experimental alloy containing 25 pct Cr, 10 pct Mo, and balance Fe. X-ray diffraction patterns on the as-cast material revealed the presence of a body-centered cubic phase having a lattice parameter of 8.89?. The structure was sufficiently similar to that of y chromium that for a time it was thought that the structure might be caused by the presence of some undissolved electrolytic chromium particles. The alloy as-cast was so brittle that it shattered after the slightest hot reduction by hammer cogging. This paper gives the results of some metallographic and X-ray diffraction studies on x phase as found in several experimental alloys as well as a few molybdenum-bearing commercial stainless steels. The analyses of materials studied were as shown in Table I. Experimental Procedure Metallography: Solid specimens were polished mechanically and etched in boiling 50 pct HC1 solution in order to best delineate x and s phases in the alloys studied. X-Ray Diffraction: The difficulty of satisfactorily developing diffraction lines for s phase in solid specimens has been previously reported by Bindari, Koh, and Zmeskal.V or this reason all specimens used in this investigation were subjected to anodic

Jan 1, 1954

By E. Gregory, C. G. Goetzel

The outstanding elevated temperature properties of materials made from sintered aluminum powder have been well established in recent years.1,2 and considerable investigation has been carried out on the structures which appear to be responsible for this type of strengthening.2,3 The maximum operating temperature of such materials is severely limited, however, by the low melting point of the aluminum matrix; and, therefore, considerable interest was aroused in methods of introducing the

Jan 1, 1959

By V. Apraxine, J. Lakaye, J. J. Saquet, P. Troch

Union Minière du Haut-Katanga owns concessions for extracting copper and associated metals in the high plateau region of Katanga. The concession is about 188 miles long by 44 miles wide and has three principal areas: Southern area-The Prince Leopold mine is an underground operation from which a copper-zinc sulfide ore is extracted. The mine and associated concentrator are at Kipushi. Copper concentrates are smelted and converted to blister copper at the Lubumbashi smelter at Elizabethville.

Jan 12, 1962

By J. E. Flinn, J. M. Welch, R. L. Miller

Introduction Two samples of an iron-enriched basalt (IEB)-a silicate-based fused-cast ceramic waste form-containing components that simulate Three Mile Island Unit 2 core debris were tested for uranium recovery (Miller et al., 1984). This material is highly refractory towards leaching by ground water. The uranium content is high (15.1%) and the U-235 content (2.57%, only

Jan 1, 1986

By Henry Rawdon

THE RELATION between the course, or path, of the fracture of metals and alloys, produced in service or as a result of certain laboratory tests, and the crystalline units of which such materials are composed is of utmost importance. The fracture of normal material is, in general, intracrystalline, i.e., it consists of a break across the grains rather than of a separation between them. An intercrystalline fracture indicates either that the metal is of very inferior quality or that the break occurred under very unusual conditions, e.g., at a very high temperature. The usual mechanical tests, when applied to metals of the type that breaks with an intercrystalline fracture, merely measure the coherence of adjacent grains for one another and reveal little as to the real properties of the metal itself. Even such a soft plastic substance as lead, under suitable conditions, may be rendered so weak and brittle that the metal can be easily crumbled into powder by the fingers although the constituent grains have lost none of the intrinsic properties of lead. Various erroneous explanations of this behavior of lead have appeared in the scientific literature, the change being described usually as an allotropic one. The importance, in an industrial sense, of a proper explanation of this type of the corrosion of lead justifies the description of the type of metal deterioration that follows.

Jan 2, 1920

By T. E. Godson

AS this is the age of reform, a uniform mining law for North America is a moot subject for discussion at this meeting of the Institute. The question is one of peculiarly technical and, in many respects, local character. We all appreciate the value of the metal-producing industries and recognize the necessity and importance of a well-considered and evenly balanced mining law as a branch of our jurisprudence either for the Provinces or the Dominion as a whole. Mining has taken its place as a forempst industry and legislation that seeks to control and govern it is the concern of not only the active miner but the citizens of the state. A law that, through its charitable measures brings into being the prospector, the pathfinder and superstructure of all mining activity and industry! protects his interests, safeguards invested capital, and encourages and enforces development, possesses at least the salient requirements of a businesslike Act. The manner of doing so is, I think, one of local and internal concern. May I be permitted to say without presumption that of the five mining codes, or Acts, that we have in the Dominion of Canada born and bred within the Provinces of British Columbia, Ontario, Quebec, New Brunswick, and Nova Scotia, some of them could be materially improved. In many respects they do not measure up to the times; they were no -doubt creations of merit at the date of their .birth but they have not been clothed in seasonable raiment as the years passed by. It is a stern fundamental principle that all natural resources are the inalienable property of the crown. If it is mineral land, then it follows for the protection of the state and the direct advancement of the occupant that the land should be developed as such. The method or machincry by which this must be accomplished is a matter of detail, not of principle. If the right to possession as a licensee depends on discovery, it is not inconsistent with the duty the crown owes to the state that a grant in fee should pass to the discoverer if there is imposed, after patent issues, a requirement of continuous work or the alternative of an acreage tax sufficiently burdensome to make it unprofitable that the land should be held in an undeveloped state. If this requirement is recognized, the mental distinction between a grant and lease ceases to exist. A

Jan 1, 1920

IN welcoming the attending members of the Ameri-can Zinc Institute's Ninth Annual Meeting to St. Louis on April 18, the president of the Chamber of Commerce stressed the notable progress that had been made during nine years, marked by many price de-pressions and internal dissensions, while controversies between miners and smeltermen threatened to wreck the organization, prices dropped, and consumption grew languid for want of organized publicity and research. The reports and recommendations of Percy B. Butler, chairman of the Adjustment Committee, and F. C. Wallower, chairman of the Galvanizing Committee, might well be adopted as the institute's objectives. In reply to the speeches of welcome to St. Louis, Arthur Thacher reminded the delegates that the cor-ner stone of progress in the mineral industries was laid by the formation of the American Institute of Mining Engineers in Wilkes-Barre, Pa., in 1871, and the dedication of that organization to the exchange of ideas and methods of the winning of metals and non-metals from their crude state. The activities of the American Zinc Institute constitute, he said, a valuable phase of that work. Mr. Thacher forecast the treat-ment of 1 per cent zinc ore. After the reading of the report of the board of directors, in which Scott Turner and Louis Boschern were named as honorary members of the institute, a survey of world zinc conditions by A. J. M. Sharpe of London was presented. He held pres-ent conditions in China responsible for much of the present depression in zinc. World stocks on, April 1, 1927, were estimated as 52,900 metric tons. Adolph Boldt's paper on "Solidarity in Industry" was followed by a survey of the Tri-State district by Otto Ruhl, who emphasized the importance to the dis-trict of the organization of the Tri-State section of the A.I.M.E., which already has 135 members and asso¬ciates. He also mentioned .that flotation in the Tri¬State field is adding 1500 tons of concentrate to the weekly production. "Mining Economics" was the subject of Julian D. Conover, secretary of the Tri-State Zinc and Lead Ore Producers Association. He gave a detailed report on the costs of mining and milling in the district.

Jan 5, 1927

By Arthur Notman

IN VIEW of the wide publicity given to the charges by the Couzens Committee of the United States Senate of discrimination by the Bureau of Internal Revenue in favor of the copper companies, it becomes a matter of interest to consider the basis for these charges. The point to be determined is whether they rest on a foundation of fact or are purely and simply matters of opinion. The whole question boils down to the purpose of the Tax Law as applied to mines, which is to afford the same protection to them as provided for all other taxpayers, namely: that they were to be allowed to pay back as depletion to their owners the values of their properties as they existed or were estimated to exist on May 1, 1913, free from tax. To determine these valuations it was? necessary to select from a wide range of possibilities a set of values for a number of essential factors.

Jan 1, 1925

By Henry E. Wood

In my opinion, the concentration of minerals by flotation is the most interesting problem in ore-dressing, and will command eventually far more consideration than it has at present. For many ores it furnishes a complete method of concentration absolutely independent of specific gravity, and thus simplifies the milling of many difficult combinations. Not having to recognize the influence of specific gravity, we are also able to dispense with some of the complications resulting from classifying-conditions. Where flotation cannot be used for a complete separation of the minerals from the gangue, it will be found, in nearly all cases, to save those portions which are generally lost by reason of their fine state of division. For this reason, it should be looked upon mainly as an aid to general concentration, although there are many ores so well adapted to flotation that more than 90 per cent. of the valuable metals can be recovered from them in one operation by this process. In presenting the results of my investigations in flotation, I have endeavored to theorize as little as possible. That side of the subject has been extensively discussed by others. My earliest work with flotation was done in 1895, when I used various oils, grease, soap, etc., with results that were remarkable. I did not realize then that with water alone equally good separations could be made. Up to 1906, my endeavors were confined to attempts to keep the concentrates on the tables well wetted and away from exposure to the air. In common with others, I observed that when there mas any obstruction in the wash-water on the table of sufficient size to divert the water to either side, the concentrates collected, and, on exposure to the air, would promptly float away. This convinced me that the sulphides were all good "swimmers," and that if,

Jan 1, 1913

By George A. Packard

THE experiments here described were made under my supervision while temporarily acting as head of the Department of Metallurgy at the Missouri School of Mines, at Rolla. The work was done by Messrs. W. E. Brown, W. C. Richards, and F. L. L. Wilson, and the description of the results forms a portion of a thesis presented for the degree of Bachelor of Science. These results are submitted because I have seen no description of the application of pot roasting to the treatment of a copper-concentrate. This work followed that already described in the discussion of the ' Lime-Roasting of a Galena-Concentrate,"' and was similarly occasioned by the lack of a furnace of the reverberatory type in which the copper-concentrates could be smelted. The material for the tests was a mixture of three lots available. The first consisted of 8-mm. jig-concentrates and the second of 0.5 mm. table-concentrates, from the San Juan district, Colo. Both contained pyrite, chalcopyrite and galena. The third was a lot of copper-ore, found in the laboratory, which had been crushed through 8-mm. screen, and had at some previous time, before the laboratory roasting-furnace was torn down, received a partial roasting. The analyses of these ores are given in Table I. In order to determine the applicability of pot-roasting as to each lot of ore, and the effect of varying proportions of lime, six preliminary tests were made in a " size N " Battersea crucible, 9 in. high by 6 in. in diameter at top, with a 5/8 in. hole bored through the bottom. The crucible was set in the upturned elbow of a 2-in. pipe, the joint being luted with clay; and air was obtained from a receiver supplied by a compressor. The

Jan 1, 1908

A meeting of the Board of Directors was held in the Council Room of the U. S. Bureau of Mines, Interior Building, Washington, D. C., on Friday, June 21, 1918, at 4 p. m. Twelve members of the Board, the Secretary of the Institute, and nine guests were present. Upon the petition of 28 members of the Institute residing in or near Washington, D. C., a Washington Section was authorized. A committee was appointed to nominate officers and prepare a set of by-laws. The report of the Treasurer was presented in writing, accepted, and ordered filed. Thirty-nine members, 12 associates and 8 junior associates were elected. Two members were reinstated. One resignation was accepted. The dues of 64 members were suspended on account of their being on active war duty.

Jan 8, 1918

By Hertha R. Freche

The diffusion of magnesium and silicon from the core into the high-purity coating of Alclad sheet is important commercially, and led to the use of a duplex product for the study of diffusion by means of spectro-graphic analysis of successive layers. It has been found that in the duplex materials the diffusion of magncsium from an undersaturated aluminum-magnesium alloy into its high-purity aluminum coating is approximately of the same order of magnitude as the diffusion of silicon from a saturated aluminum-silicon alloy into its high-purity aluminum coating. However, if magnesium and silicon are both present in the alloy in the ratio of Mg2Si, they appear to diffuse in the approximate ratio of this compound. Finally, if the alloy contains silicon in excess of the amount required by magnesium silicide, the amount of diffused silicon in the high-purity aluminum coating will also be in excess. The interdiffusion of metals in the solid state is of both scientific and technical interest, because it is helpful in the study of the alloy structure and in the solution of problems pertaining to the strength and surface condition of the fabricated product. W. C. Roberts-Austenlt carried out the first quantitative determination of the coefficient of diffusion of gold into lead. This classical experiment was followed by a series of investigations on the diffusion of metals and nonmetals in iron and steel and in nonferrous metals and alloys. Recently the diffusion of copper in coated strong aluminum alloys was investigated by A. Burkhardt2. This appeared to be the first published investigation on the diffusion of metals into aluminum. The present investigation was the direct result of a technical question in connection with alloy fabrication and is a summary of some preliminary work pertaining to the diffusion of magnesium and silicon into aluminum. The results necessarily will be subject to some variations, since this is the first attempt to evaluate the coefficients of diffusion of magnesium and silicon into aluminum according to this method of procedure. This

Jan 1, 1936

By Eli T. Conner

(Wilkes-Barre Meeting, June, 1911.) My connection, under a commission from the Councils and Board of School Control of the city of Scranton, Pa., with a recent investigation of mine-caves and the resultant damages to surface-improvements, has led to the preparation, at the invitation of our Secretary, of the present paper. It is notorious that there are, in the anthracite-fields, frequent subsidences of the surface, due to the removal of the coal beneath. No particular attention is paid to such occurrences, unless they happen to injure surface-improvements. Many caves have happened in Scranton and its vicinity, which have excited but little remark, since they have generally caused no serious damage. In August, 1909, a cave occurred in the Hyde Park section of the city, generally known as the West Side, which nearly destroyed school-house No. 16 and considerable adjacent property. 'Fortunately, there were no pupils in the building at the time; but the thought of the possible result, bad the usual number of pupils and teachers been present, aroused the public to the gravity of the situation; and the School Board employed engineers to investigate the case. Two reports were made by separate sets of engineers, which differed in some particulars. These differences were pointed out in the public press and magnified, and the consequent agitation of the subject was taken tip and greatly exaggerated by some of the metropolitan newspapers, giving to uninformed people the very erroneous impression that the whole city of Scranton was in danger of sinking into the bowels of the earth. All this tended to affect the credit of the city and to depress real-estate values. The matter was considered at a joint meeting of the Board of Trade, the Councils, and the School Board. The Hon. J. Ben. Dimmick, a former Mayor, suggested that it

Sep 1, 1911

By R. Silverman, H. Blumenthal

It was found that despite the similarity of chemical analyses of different titanium carbides used as base materials for cermets, the physical properties, especially transverse-rupture strengths, of test bars were different. Hence this metallographic study attempts to link physical properties to micro-structures. It is shown that microstructure, grain shape, and grain growth are functions of three interrelated factors: 1—powder production procedure, 2—surface conditioning of the particles, and 3—impurities either contained in the original powder or acquired during ball milling. An explanation is offered for the "coring effect," long observed, but heretofore of unknown origin. The explanation is based on assumption of an oxide film and on chemical analyses which substantiate these findings. TITANIUM carbide has become in recent years a material of great interest in the high temperature field. Consequently, many manufacturers in the United States and Europe are producing titanium carbide for cermet applications as well as for additions to the well known tungsten carbide tools. All present commercial processes of titanium carbide production utilize the chemical reaction of titanium dioxide and carbon to form as nearly as possible stoichiometric Tic. This reaction is carried out in three ways: 1—in a menstruum of molten metal,' 2—in the solid state, either in a protective atmosphere2 or in vacuum;" or 3—in an are-melting operation. In spite of the fact that the pure carbides obtained in these operations are almost identical chemically, the physical properties vary considerably when they are combined with a binder (Ni, Co) to form cermets. This fact led the authors to examine metal-lographically nickel-bonded titanium carbide in order to find the possible reasons for this behavior. Materials and Methods Five different titanium carbides were used in this investigation. They are identified in Table I. The first four materials were used in the as-received condition. Material E, received in lumps, was crushed to —100 mesh and carried through a flotation process in order to bring its graphite content in line with the other products. A Galagher flotation cell was used with pine oil as frothing agent. The chemical analyses of the investigated materials are given in Table 11. The binder used was carbonyl nickel of 9 to 14 microns particle size, supplied by A. D. Mackay. The materials were ball milled at a ball to charge ratio of 6:1 using procedures described under "Experiments and Results." All particle sizes mentioned are averages determined with a Fisher Sub-sieve Sizer. Test bars (lx0.40x0.16 in.) were prepared by 1—hot pressing to 85 to 95 pct of theoretical density at pressures between 1 and 1½ tsi and temperatures from 1600" to 1800°C, 2-—-cold presssing after 3 pct camphor had been added, or 3—wet pressing, both 2 and 3 at pressures between 5 and 10 tsi. All pressed bars were sintered in a vacuum of 105 to 10-6 mm Hg for 2 hr at 1350 °C. Transverse-rupture strengths were determined by breaking on a Baldwin Universal Testing Machine over a 9/16 in. span. Densities were measured by water displacement. The preparation of the specimens for micrographs was done according to Silverman and Doshna Luscz." All magnifications are at X1000. A sodium picrate electrolytic etch was used. Experiments and Results The influence of ball-milling procedure, ball-milling medium, pressing procedure, and sintering procedure on the microstructure of 80/20 — TiC/Ni were investigated. Ball Milling of Materials A, B, and C in a Steel Mill: Figs. 1 and 2 show microstructures of hot-pressed and vacuum-sintered test bars of materials A and B after the respective materials had been ball milled to 2.1 microns particle size in a steel mill and mixed with 20 pct Ni binder. Material A (Fig. 1) shows considerable grain growth. Also evident is a tendency of the carbide grains to coalesce. The density is 98 pct and the low transverse-rupture strength of 111,000 psi is probably caused by many large grains and an unfavorable packing factor. Almost all grains show a slight indication of "coring." Material B (Fig. 2), although showing grain growth, still has many small particles and a better distribution of binder and carbide due to the relative absence of the coalescing tendency. "Coring" can be observed in almost all grains. The high transverse-rupture strength of 179,000 psi and the density of 100 pct are believed to be due to the many small grains completely surrounded by the binder phase. There is also a preference to form spherical grains with material A, while most grains of material B preserve their angular shapes. Material C, of which no picture is given, stays between A and B in every respect. Rounding of some grains can be observed as well as coring, but the latter to a lesser degree than with material B. Its densification is good and the transverse-rupture strength obtained is 142,000 psi. Ball Milling of Materials A, B, C, and E in a WC Mill: When the Tic powders were ball milled to 2 microns particle size in a we mill, then ball-mill mixed with 20 pct Ni binder, hot pressed, and vacuum

Jan 1, 1956