Search Documents

By L. S. Darken

THE manufacture and treatment of metals comprises operations whose effectiveness depends in large measure upon diffusion phenomena. The significance of such phenomena has, for a few simple cases, long been understood, but in more complex cases it has not been adequately recognized. This paper presents a mathematical analysis of some of the cases in which diffusion leads to the formation of a new phase within the metal, and this analysis provides a basis for interpreting quantitatively many apparently diverse experimental observations recorded in the literature, some of which are outlined in the following pages. OBSERVATIONS RECORDED IN LITERATURE An outstanding instance is the general type of phenomenon in which diffusion of an element into an alloy is followed by a phase change, which most frequently is a reaction (precipitation) of the diffusing element with one or more components of the alloy to form a compound. Thus in certain alloys heated in contact with oxygen not only the usual oxide scale appears but, in addition, beneath the surface, a well-defined zone in which free oxide particles are dispersed with notable uniformity. This zone, commonly referred to as the subscale or zone of internal oxidation, is remarkable in that the visible boundary between it and the unaltered metal is usually sharp. Such a subscale, which appears to have been recognized first in oxidized copper alloys, has been described and studied by C. S. Smith,1 by Rhines,2 and by Rhines, Johnson and Anderson;3 but it appears also in other alloys when they are exposed to conditions that bring about the precipitation of some compound, not necessarily an oxide. Another clear case of this same kind is the diffusion of carbon into a steel containing an element such as molybdenum, chromium, vanadium or tungsten, whose carbide is less soluble in iron than iron carbide, the result being that some part of that element is precipitated as a dispersed carbide. A similar phenomenon may occur on the welding of two alloys each of which contains one of a pair of elements that react to form a compound or a new phase of any sort. But in addition to the precipitation of a compound formed from the diffusing element, other effects may result merely from the presence of the diffusing element. For instance, if homogeneous austenite, nearly saturated with respect to carbon, is heated in contact with silicon in the absence of oxygen, one would expect to find, behind the several iron-silicon phases analogous to a scale, a zone of austenite containing dispersed carbide, because of the fact that silicon decreases the solubility of carbon in iron. As still another example, oxidation of an alloy may result in diffusion toward the surface of one or more of the constituents; for instance, during oxidation of a steel containing an element such as copper, which is less prone to oxidation than iron, there is a notable enrichment of copper just beneath the scale-metal interface. As an example of a yet more

Jan 1, 1942

By H. W. Graham

AS these annual occasions in honor of Henry Marion Howe continue through the years: there is progressively less likelihood that the lecturer will have had personal knowledge of Dr. Howe. The present speaker is one of those who unfortunately had no opportunity to come under the inspiring presence of this great metallurgist. A review of Howe's work shows it to cover a comprehensive range of interests and to evidence an impressive richness of detail. Not only was Howe at home in the laboratory, but he was familiar with the processes of iron and steel making and had a real understanding of them. His writings include much that is descriptive of processes with a wealth of material that is becoming of increasing historical value. He recorded his studies of the theoretical aspects of processes and published at least two process classifications, one in 1890 that was lengthy and somewhat theoretical, and a second in 1906 that was more of a practical listing. Wide as Howe's field of interest was, it is significant of the circumstances of his time that he gave- little consideration to raw materials or to their effect on iron and steel making processes. In 1933, Waterhouse, Howe lecturer for that year, presented a descriptive summary of the major steel making processes, and in 1946 Joseph discussed the blast furnace process. Otherwise Howe lectures have not dealt with processes as major subjects. In today's lecture, with no effort to describe the mechanical arrangements of iron and steel making facilities, it is proposed to examine the essential technological elements of the processes, to explore the inter-relation of these elements, and particularly to seek recognition and understanding of those factors which determine why certain processes are or are not used. The discussion of this lecture will deal with the major well-known large tonnage processes, with only such attention to processes of minor tonnage and special character as may be warranted for explanation by contrast. Subject to the errors of generalization and the shortcomings of condensation involved in presentation limited to a single hour, it is proposed to examine broadly but intensively those operations which convert raw materials into steel. It is an innovation for a Howe lecturer to discuss the raw materials of the iron and steel industry, but the changing circumstances of passing years intensify the influence of raw materials on processes and require the metallurgist to be alert for the process adjustments that may become advisable or mandatory. For a half century the metallurgical processing of iron and steel has followed a surprisingly straight path, but this does not necessarily mean that there are no curves in the road ahead. Ages ago primitive man came to know iron in its metallic form, not only by the

Jan 1, 1948

By H. W. Graham

AS these annual occasions in honor of Henry Marion Howe continue through the years: there is progressively less likelihood that the lecturer will have had personal knowledge of Dr. Howe. The present speaker is one of those who unfortunately had no opportunity to come under the inspiring presence of this great metallurgist. A review of Howe's work shows it to cover a comprehensive range of interests and to evidence an impressive richness of detail. Not only was Howe at home in the laboratory, but he was familiar with the processes of iron and steel making and had a real understanding of them. His writings include much that is descriptive of processes with a wealth of material that is becoming of increasing historical value. He recorded his studies of the theoretical aspects of processes and published at least two process classifications, one in 1890 that was lengthy and somewhat theoretical, and a second in 1906 that was more of a practical listing. Wide as Howe's field of interest was, it is significant of the circumstances of his time that he gave- little consideration to raw materials or to their effect on iron and steel making processes. In 1933, Waterhouse, Howe lecturer for that year, presented a descriptive summary of the major steel making processes, and in 1946 Joseph discussed the blast furnace process. Otherwise Howe lectures have not dealt with processes as major subjects. In today's lecture, with no effort to describe the mechanical arrangements of iron and steel making facilities, it is proposed to examine the essential technological elements of the processes, to explore the inter-relation of these elements, and particularly to seek recognition and understanding of those factors which determine why certain processes are or are not used. The discussion of this lecture will deal with the major well-known large tonnage processes, with only such attention to processes of minor tonnage and special character as may be warranted for explanation by contrast. Subject to the errors of generalization and the shortcomings of condensation involved in presentation limited to a single hour, it is proposed to examine broadly but intensively those operations which convert raw materials into steel. It is an innovation for a Howe lecturer to discuss the raw materials of the iron and steel industry, but the changing circumstances of passing years intensify the influence of raw materials on processes and require the metallurgist to be alert for the process adjustments that may become advisable or mandatory. For a half century the metallurgical processing of iron and steel has followed a surprisingly straight path, but this does not necessarily mean that there are no curves in the road ahead. Ages ago primitive man came to know iron in its metallic form, not only by the

Jan 1, 1948

By Richard H. Jahns

GRANITIC pegmatite deposits are the chief source of commercial feldspar, sheet mica, beryllium, tantalum-columbium, and lithium minerals, and certain types of kaolin. They also have yielded significant quantities of cassiterite, gems, scrap mica, molybdenite, tungsten minerals, uranium-thorium and rare-earth minerals, and zircon, either directly or as the sources of placer deposits. The output from pegmatite mines in the United States is small as compared to other mineral products in terms of bulk or value, and much of it comprises minor metals and nonmetals. Nevertheless, pegmatite minerals play a vital part in domestic industrial economy, particularly in the ceramic and electrical industries. Numerous special purpose uses also are important, even though they require small quantities of raw materials. Never was United States dependence upon pegmatite mining more clearly emphasized than during World War 11, when greatly expanded demands and uncertainties of foreign sources of supply caused much concern. Such commodities as beryl, tantalite, and sheet muscovite remained high on the critical list for months at a time, and for some minerals there was a real struggle to achieve and maintain a favorable ratio of supply to demand. Satisfactory stock piles of certain sizes and qualities of sheet mica, for example, were not built up until late in 1944, when wartime requirements already had begun to level off or even to decrease. Production of all the strategic pegmatite minerals from domestic deposits during World War I1 constituted only 10 pct or less of the total domestic consumption of these minerals, but the importance of this contribution should not be minimized. Domestic production often represented the difference between increase and further reduction of existing stocks of commodities already in seriously short supply, and in the early stages of the war it was the only assured source if imports were cut off. During the recent war period, the U. S. Geological Survey carried on a program of pegmatite studies in the New England and Southeastern States, in the Black Hills area of South Dakota, in the Rocky Mountain region of Wyoming, Colorado, and New Mexico, and in various parts of Washington, Idaho, Utah, Nevada, Arizona, and California as shown in Fig. 1. Several papers and reports already have appeared as an outgrowth of this work,'-= and others are in preparation. This paper outlines some results of data obtained by the writer during the period 1942 to 1946, when he was engaged in studies of pegmatites in the Southeastern, Southwestern, and Rocky Mountain States. Beryllium Minerals Beryl is the present commercial source of beryllium metal and beryllium compounds, which are used in ceramics, in the preparation of X-ray tubes and fluorescent lamps and screens, in special processes of paint and textile manufacture, and in the optical systems of some electrical instruments. The metal also is used in nuclear physics, chiefly as a source of neutrons. Beryllium is alloyed with aluminum for certain light-metal uses and is a constituent of some nickel and iron alloys. Currently the chief demand, however, is for copper-base alloys, which are exceptionally resistant to fatigue and wear, are responsive to hardening treatments after

Jan 1, 1952

By John E. Hagni, Richard D. Hagni

ORE.ID, a microcomputer program, rapidly searches a database of the principal properties for 573 ore minerals. Searches may be performed on any or all of the following properties: mean Vickers hardness, Talmage hardness, mean reflectance, strength of anisotropism, and colors and tints of the mineral and its internal reflections. Data from the International Mineralogical Association - Commission on Ore Microscopy data card file have been used when available. The program displays the number and type of data matches for each mineral found, displays their chemical components, and allows the range to be narrowed or widened for each of the identification properties for repeated searches, if desired. ORE.ID is much more rapid, allows for the use of more identification properties, and involves more ore minerals than any previous identification system.

Jan 1, 1985

By J. J. Bean

Concentrating mixed sulfide-oxide copper ores by the leach-precipitation-flotation method is an old operation at the Miami Copper Co. The idea was conceived and the method developed at Miami by F. W. Maclennan and Harmon Keyes during the years 1929 to 1934, and it was these men who gave the term LPF to this process. Miami at that time had considerable reserves of mixed sulfide-oxide ore.* In the development of a suitable treatment method, it was natural that leaching of the oxides with acid and the precipita¬tion of copper from the resulting copper sulfate solution by iron was investigated. The separation… • The term oxide as used in this article includes the copper oxides, carbonates, and silicates.

Jan 12, 1960

By Donald R. Rathburn, Jung K. Mok

An historical review and a survey of current practice in the application of fine dry grinding in the iron ore industry are given. Both closed and open-circuit applications are reviewed, and the advantages, disadvantages, and process considerations for these two systems are discussed. The ground ore temperature rise, and the cool-ing of ground ore and mill ventilation are also discussed, along with the agglomerating characteristics of dry ground ore. Screening during the production of high-grade lump ore for blast-furnace burden, particularly from recently developed ore deposits in Australia, South America, and Africa, has resulted in large tonnages of fine iron ore. Certain owners have decided to stockpile these fines until some later date. Others have either sold these fines "as is" for agglomeration at the steel plant or have established their own pelletizing plants to produce a premium quality agglomerate. In almost all cases some grinding is required prior to pelletizing. Most of these ores occur in the weathered state which may result in difficulty in the thickening and/or filtering stages when ground in a wet system. The resulting filter cake would probably require partial drying to provide a product suitable for the subsequent balling operation; however the partial drying and subsequent material-handling steps often produce random agglomeration. Normally, these agglomerates will cause problems in the green ball formation process. Thus dry grinding has developed as a solution to this problem. Most of the dry iron ore grinding installations utilizing the standard-type rod or ball mill are grinding high-grade natural ores that do not require beneficiation. Although power consumed per ton of final product is 120% or greater in dry grinding as compared with wet grinding, the additional power required for dewatering and handling a wet ground product can easily exceed the initial power savings. Dry grinding of raw feed and clinker has been practiced in the cement industry for many decades but its major application to the iron ore industry has taken place only within the past ten years. The successful application of dry grinding to iron ore has required the solution of several unique design and operating problems. The purpose of this paper is to review recent developments in fine dry grinding of iron ore for pelletizing and to discuss the various designs and operating parameters involved.

Jan 1, 1971

Jan 1, 1970

By Cornelius J. Dwyer

It is possible to hold a very optimistic view of the future of the U.S. coal industry, and there are those in the coal industry who generally choose to do so. For example, a major coal company stated recently in its annual report, "Coal's prospects appear brighter today than at any period in the past." In order to continue in this state of euphoria, it is only necessary to remind oneself of the following "facts":

Jan 7, 1967

By T. S. Fuller

The tensile properties of steels at elevated temperatures have been studied by numerous investigatorsll primarily for the purpose of determining their suitability for structural uses. Tests with this objective have been confined largely to the temperature range of approximately 20" to 500' C., because of the rapidly decreasing tensile strength at the latter temperature. Tests have also been extended to higher temperatures2 for the purpose of determining the most suitable forging range. This temperature range is also of theoretical interest. The phenomenon if increased tensile strength and decreased ductility .in the so-called "blue-heat" range, approximately 200" to 300" C., is well known. It was suggested to the Bureau early in 1926 that a study of the properties of rail steels in this temperature range might prove of interest in relation to the studies of transverse-fissure failures in rails. There were available from another investigation3 several new rails from several different heats made to approximately the same specification requirements, the complete manufacturing histories of which were known. It was decided to determine, at least in the preliminary series of tests, only the ultimate tensile strength, elongation and reduction of area, because of the difficulty, time and cost involved in determining the proportional limit and yield point at elevated temperatures.

Jan 1, 1930

By William M. Brewer

History.—The history of gold-mining in Georgia and Alabama antedates the discovery of gold in California. A very large proportion of the gold used in the United States previous to 1849 was produced by these States. A great deal of this history is merely tradition, and no reliable statistics can be obtained ; yet a personal examination of the gold-fields of Georgia and Alabama indicates that tradition is as fairly reliable, with regard to the history of these gold-regions, as it is in any similar cases throughout the world. In Georgia, the history of gold-mining dates back to 1829, when the first gold-mining excitement in the United States occurred. In Alabama, the discovery of gold was made some years later through the work of prospectors, incited by the rich finds in the Georgia mining camps. The greatest product of gold in these States was between the years 1840 and 1849. In Lumpkin county, Ga., and Cleburne county, Ala., the districts from which the most of this gold was taken, the tailing-dumps are silent witnesses of the extensive operations which were carried on by the primitive and crude methods then known. It is no rare thing to see trees 12 to 15 inches in diameter, and even

Jan 1, 1896

By J. P. Sheeha, W. F. Craig, M. Baeyertz

The loss in toughness caused by phosphorus within commercial ranges was studied in AISI-SAE 1340 steel and in molybdenum modifications of this grade. The replacement of part of the manganese by molybdenum in amounts which maintain the hardenability of the standard 1340 grade was shown to counteract to a marked degree the detrimental effects of phosphorus. THIS paper deals with the effect of phosphorus on the toughness of 1340 steel and with the effect on toughness of replacing part of the manganese by molybdenum while retaining the same hardenability as that of 1340. In previous work1 a progressive decrease in toughness was observed when the phosphorus content of 5140 was raised from 0.020 to 0.036 pct; that is, from a moderate phosphorus level to one higher but yet within the AISI-SAE specification for this grade. The structural condition of the steel was tempered martensite. Toughness was evaluated by the transition temperature determined by V-notch Charpy tests. Replacement of a part of the chromium in 5140 by molybdenum provided a factor of safety against loss of toughness caused by phosphorus, especially where the steel was cooled slowly after tempering. Scope of the Study: In view of the improved tolerance for phosphorus obtained by replacing a part of the chromium in 5140 with molybdenum, it seemed desirable to investigate the possibility of obtaining similar improvement in 1340 by replacing part of the manganese with molybdenum. Heats were made at different phosphorus levels, in a series that began with 1340 and ended with steels containing 0.32 to 0.35 pct Mo with 0.82 and 0.90 pct Mn. The analyses of the heats are given in table I. In order to facilitate later discussion, the 1340 heats have been placed together in the order of increasing phosphorus content, and the molybdenum modifications have been grouped according to phosphorus

Jan 1, 1951

Jan 1, 1938

By D. M. Hausen

The amenability of a given vanadium ore to any given treatment depends largely on the mineralogic combinations of vanadium in the ore. Quantitative data on vanadium mineralogy provide not only an objective basis for selection of proper treatment, but also may eliminate many time-consuming amenability studies whose results are empirical, at best. Vanadium is distributed through the interstices of mineralized sandstone ores in the form of oxidized vanadates, reduced oxides, and silicates. Oxidized vanadates, e.g., carnotite, tyuyamunite, etc., are most readily beneficiated by simple acid leaching. Reduced oxides are more slowly solubilized, but relatively amenable to most acid treatments. The layered silicates, roscoelite, mixed layered mica-montmorillonite, and chlorite, are least amenable to most acid extractions, and constitute an assemblage of vanadium- bearing clays that are common to many sedimentary deposits. Vanadium is combined principally as layered silicates in the clay fractions of many sandstone ores. Mineralogic studies in this paper are largely confined to clay minerals, and to their amenability characteristics in low pH liquors.

Jan 1, 1985

By Lawrence B. Wright

THE Republic district, Washington, is of new interest because of the discovery of new gold-silver ore within a unique structural pattern. The camp was revived in 1937 following installation of a plant to treat low-grade disseminated ore at Knob Hill and further stimulation followed discovery of "cross vein" breccia ores in 1939. Previous writers 1-2 ascribed the quartz veins to a latite porphyry stock, but are in disagreement as to its precise location and extent. This study leads to the conclusion that the ores have a more profound parentage linked to a broad system of thrust faults and folds, the mechanical origin of which is related to a southward trending (Sanpoil) syncline connecting with the Lewis and Clark zone of shift described by Billingsley and Locke3 in 1939. The Republic anticline and a cross anticline recumbent against Cretaceous granodiorite, and involving some 4000 ft of Eocene andesite flows and early Miocene lake beds, localize the ores, mainly along the east flank, in a series of openings simulating drag folds and steeper than the folded flows. These broad structural features no doubt reach deeply into the basement rocks, where at appropriate crossings and junctions it is suggested that heat effects gave rise to oremaking materials, including, in this instance, intrusive breccias that later were mineralized, and comprising the broader bodies of new ores. The breccia ore is seen crosscutting the earlier narrow quartz veins with a welding of the two at junction areas by a second surge of ore minerals. The ore mined and developed since 1937 equals district production from 1896 to 1937. The ores are typified by cherty quartz, adularia and some barite, with fine pyrite and marcasite, polybasite, pyrargyrite, tetrahedrite and gold. Selenium is present, possibly with gold, as a normal selenide. The disseminated ores, as well as the vein and breccia ores, are localized principally in one 500-ft flow (Knob Hill andesite), which has been traced around the crest of the low northward-plunging Republic anticline. The gold-silver ratio in the earlier narrow veins is about 1 to 4 and in the disseminated and breccia ores, 1 to 7. The latter higher silver ratio is deemed to reflect the character of the second surge of mineralization. Sills and dikes of the Columbia River (Miocene) basalt cut the folded structure and ore, thus placing the mineralization in the middle Miocene.

Jan 1, 1947

By Myers, J. F.

The purpose of the mill tests reported herein, was to determine the relative power efficiency of fast and slow rod mill speeds on the ores of the Tennessee Copper Co. The tests were carried out at the lsabella Mill of the Tennessee Copper Co. under normal operating conditions. Every effort was made to keep the ore supply and other conditions constant, but it will be noted that some slight variation did occur. The open circuit 6 by 9 rod mill, and ore, used in these tests have been previously described.' Four motor drive pinions were available and the tests were performed in the following manner: each pinion was used to drive the mill for a period of one week. Constant sampling prevailed during the test run, and a composite sample for each speed test was made. Realizing that some slight liner wear took place during the four-week test-run, and that some slight variation of the ore may have taken place, a second and then a third series of four-week test- runs were made with the four different pinions. The screen analysis of each of the thee-week run samples at the various speeds were composited and the results are shown in Table 1. The authors feel that the 12 weeks of operation consumed during these test-runs would represent fairly the effect of each mill speed. The data of line 37 show that within the error of sampling and plant operation, the tons of minus 65-mesh material generated per horsepower hour was the same at all four speeds.

Jan 1, 1949

Jan 1, 1904

By S. A. Wookey

More than 90 per cent of the ore produced by stoping at McIntyre is mined by horizontal cut-and-fill methods. The remainder is mined by square set and fill. In the stopes on the upper levels, mill holes are spaced 80 ft. apart and usually it is feasible to mine the breast for the full distance between the mill holes in one operation and to break, clean out and fill without any support for the roof or walls, other than the odd crown bar or sprag. The ore is scraped to the mill holes by small (10 to 15 hp.) air-operated slusher hoists. No grizzlies are used over the chutes and care is taken to break up the big pieces beforehand. Fill usually is spread by tramming sand or waste in a one-ton car from the fill raise. Fill raises are driven parallel to the strike of the vein and are inclined at approximately 48°. In long stopes, where more than one fill raise is necessary, they are spaced about 300 ft. apart. It is sometimes necessary to stand square sets for a short distance each way under the brow of the fill raise. support needed increases and on the lower levels and in some wide stopes where closer support of the back is necessary, it has become standard practice to timber the stope with 12 by 12-in. timber. Rough timber sets consisting. of caps, tightly blocked to the back and supported on posts 7 ft. high, are placed at about 5 ft. intervals. These sets are generally salvaged from the lower breast before blasting and are used again on the upper slice after the fill has been placed. In general, two or three breasts may be broken down before mucking out and filling and the ground stands long enough to enable this to be done safely. On the lower levels and in certain wide stopes and in heavy ground, a more intermittent method must be used. Only one breast or even part of a breast can be blasted and the back must be timbered before the ore can be removed. In these cases, sill timbers 16 ft. long, supported at one end on posts from the fill and at the other end on pins inserted in holes drilled in the face, are used. Timber cribs 5 by 9 ft. built from the fill to the roof and tightly blocked to the back are used throughout the mine to reinforce both the timber sets and the square sets.

Jan 1, 1946

By Fred E. Beasley

Metallurgists have, in the last ten years, overcome many difficulties of high zinc in lead blast-furnace slags. This problem was brought to the front at the close of the war, by the price obtained for lead and the high cost of labor, fuel, and flux. The Port Pirie plant of the Broken Hill Associated Smelters, Australia, early in 1919 had increased the zinc oxide in its blast-furnace slags from 13.5 to 20 per cent., at the same time reducing the iron oxide in the slag from 33.5 to 25.6 per cent. These results were obtained by the addition of 10 to 12 per cent. granulated slag to the roaster charge, improved conditions of the crushing, mixing, and roasting of the constituents of the sinter. By experiments and improvements, the practice at this plant has developed a normal slag that carries 22 per cent. zinc oxide, and at times runs as high as 33 per cent. zinc oxide, with only slight furnace trouble. The granulated slag is used not only as a diluent to the sulfur in the roaster charge, but on account of its value as a slag-forming material and the physical properties it imparts to the finished sinter. The ore is mixed with flux and given a double roast. All the first roasting is by sintering with the Dwight & Lloyd machines. The final roasting is performed partly by Dwight & Lloyd machines and partly by H. & H. pots. The charge to the blast furnace consists chiefly of the final sinter, slag shells, siliceous and non-bearing sulfur lead ores. High blast and ore columns are the practice. The greatest care is taken to obtain in the final sinter as low a sulfur content as possible. Attracted by the success of the Port Pirie plant, The Consolidated Mining & Smelting Co. of Canada, at Trail, B. C., in 1920 treated its crushed primary sinter with about 15 per cent. granulated slag. The Trail smelter at this time was short of ore and a large part of the charge to the roasters consisted of the zinc-plant residue having the following analysis: 12 to 16 per cent. lead, 12 to 16 per cent. zinc, and 25 to 30 per cent. iron. The lead in the final sinter was low and the physical condition was so bad that all the sinter had to be screened before it could be charged to the blast furnace. Also it disintegrated on being trammed and dumped

Jan 1, 1925

By O. A. E. Jackson

Pebble milling has been practiced in the reduction works of South Africa gold mines for well over 50 years. Originally flint pebbles were imported from Denmark to grind stamp-mill amalgamation- process tailing, which contained a good deal of extractable gold, but local operators soon found that large pieces of ore could be used for the same purpose. The ore is a hard, tough conglomerate in which quartz pebbles are cemented together by a matrix of redeposited silica interspersed with pyrite crystals. The gold, rarely visible, occurs as fine particles mostly segregated at the interface of the pebble and matrix, although a small fraction occurs within the pyrite crystals. There is seldom any gold in the pebbles themselves.

Jan 11, 1959