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By Hiram Brown

The problem of stress corrosion has been discussed a great deal recently, but many factors have as yet not been clarified. There are many interpretations of the definition of the word, different corrosive media are used, and numerous methods of stressing are utilized. Some quarters believe that the inherent strength of the material under test is the determining factor of its resistance to stress corrosion, while others think that the natural corrosion resistance of the material is the determining factor. This paper is intended merely to set forth the limited experience we have had and to discuss some of the other stress-corrosion tests which have been made with light alloys.

Jan 1, 1945

By AIME

TO say that Milton Fies has been active in promoting the Southern Research Institute is a masterpiece of understatement. He is a director and trustee who was in on the ground floor when plans were first made for the Institute and since it became an actuality early in 1945 his interest and efforts continue. He talked about it at the last regional meeting of the Birmingham Section of the A.F.A. and has talked all over the South-and when he makes a speech he has really prepared it. He does not try to rival a political spellbinder, but his careful, concise English is always well thought out and to the point. Southern Research might be called his present hobby as it has been for the past two or three years. Another major interest has been his encouragement and training of engineering students. Active in the formation of the Student Chapter of the A.I.M.E. at the University of Alabama, for several years he saw to it that the students had a prominent engineer at each monthly meeting, usually taking them down to Tuscaloosa from Birmingham in his own automobile. He has also been keenly interested in the mining engineering activities at Tuscaloosa, both in the Bureau of Mines and the University.

Jan 1, 1946

By Charles H. Fulton

ONE of the events of note in mineral industry education circles during the year was the summer school for engineering teachers, devoted to mining and metallurgical engineering, which was conducted by the Society for the Promotion of Engineering Education in co¬operation with the University of Wisconsin. It was in charge of Prof. Harry P. Hammond, director of the summer school, and Prof. Richard S. McCaffery of the University of Wisconsin. It was attended by 63 people, and practically every educational institution offering mineral industry courses had representatives present. The session was successful and those in attendance spoke highly of the pro¬gram and results obtained. The Mineral Industry Education Division cooperated with the S.P.E.E. in this project. Prof. Hammond will discuss the purpose and results of this session at the February meeting.

Jan 1, 1934

By W. P. Sykes

SEVEN years ago, Dr. S. L. Hoyt1 presented a masterful discussion of the hard metal carbides and cemented tungsten carbide. His lecture summarized most of the data then available in the field; many of the details relating to the production, properties and structure of cemented tungsten carbide had never been previously published, for, in fact, this information was only then being acquired. During the intervening years, the cemented carbides have assumed a place of real importance in the commercial field, with an ever widening variety of applications due to constant improvement in the control of production technique and the unremitting search for new compositions that might better the performance of the alloys in one or another type of service. The most recent summary of production methods, properties and guides for the successful application of the cemented carbides appears in the 1936 edition of the Metals Handbook. Of necessity, much detailed information relating to structures and physical properties is not included in such a summary, and it is with such details that the present discussion is concerned.

Jan 1, 1938

By John Griffen

THEORY HYDRAULIC classification as explained by Rittinger and others was largely restricted to conditions wherein the free-falling velocities of the particles were conceived as governing the separations effected (see chapter 9). The laws governing classification under free-falling conditions have been summarized by Chapman and Mott as follows: 1 Nomenclature r represents, in a particle of irregular shape, the round-hole screen through which the particle would pass, or some other linear dimen¬sion of the particle equivalent to d, the diameter of a sphere. s, the specific gravity of the particle. 1, the specific gravity of the water used as a medium. K, a constant. W, the velocity of the water. In an Upward Current of Water 1. A particle will move upward if [W > KVr(s-1)] and, by suitably regulating the speed of the water current, the larger and heavier particles may be made to fall downward against the current, leaving the smaller, lighter particles in suspension in the current. 2. Particles such that [T1= s2-1] cannot be separated in an upward-current classifier with any one velocity of current. Coal particles having a specific gravity of 1.35 cannot be separated from refuse particles of 2.5 sp. gr. Unless 2.5-1 the ratio of diameters is less than [1.35-1 or 4.3 to 1,] and the raw coal must be screened to size limits within this ratio if they are to be separated. Cone¬-shaped vessels or vessels of other shapes that allow the use of&apos; different velocities of current at different points in the flow are used to modify this limitation. 3. During the initial stages of motion, coal particles ascend more rapidly than refuse particles of the same size. 4. A particle will ultimately fall if [W < KVr(s-1).] If particles of

Jan 1, 1950

Allan Gibb, Queensland, Australia (communication to the Secretary*):—It is gratifying that Mr. Edward Keller,&apos; who has clone so much work elucidating the principles of copper-metnllurgy, should have subjected only that portion of our investigation relating to magnetic iron oxide to anything like adverse criticism. Situated as we were on a rnining-camp, it was impossible to undertake work that would cover all the intricate possibilities connected with the materials commonly classed as matte. We therefore began the investigation on matte produced from ores that contained no other components than the sulphides of copper and iron that would be likely to enter into the composition of matte. We were, accordingly, free from ally possibility of magnetic iron oxide entering the matte, unless it were formed in the operation itself. The work done on this subject was incomplete, and the results thereof recorded as giving only negative evidence as to the absence of magnetic iron oxide. It would have been better to have left the matter open, as " not proven." The trend of the investigation was to account for the insufficiency of sulphur in matte to satisfy the requirements of ferrous and cuprous sulphides. So far as our deductions are correct, it was unnecessary to consider the (in our samples) somewhat doubtful constituent, magnetic iron oxide. The mattes that mere investigated were among those mentioned by Mr. Keller, " which scarcely show ally magnetic property." The samples showed no such property. There was no unaccountable variation in the specific gravity, which only varied, as would be expected, with the proportion of ferrous sulphide. I have had experience in smelting ores of which the gangue was a siliceous magnetite, both in blast- and rever-beratory furuace. The mattes so produced contained magnetic

Jan 1, 1908

By David Sinclair, Philip B. Bucky

The dimensions and shapes of mine structures may at present be determined by (1) field experience, (2) structural calculations, and (3) barodynamic tests. § None of these, however, provide information as to the stresses, their direction and distribution in a mine structure. For the design of pillars, the placing of openings relative to working places such as gangways, haulage levels, etc., this information is desirable. Photoelastic methods provide this and, while relatively new, their application in all engineering fields is assuming increasing importance. This paper, therefore, will present the method with a few applications to mining, and with sufficient reference for further study by the reader. PART I The Photoelastic Method The photoelastic method of stress measurement determines the stress distribution in a two-dimensional model by optical means. It makes use of the fact that when a piece of isotropic transparent material, such as glass, celluloid, or Bakelite, is stressed and viewed in polarized** light a picture is seen which indicates by its color bands of light, or fringes, the magnitude of the stresses, their direction and their distribution. General Explanation The stress at any point 0 in a structure (Fig. I), may be resolved into two components, P and Q, each a pure tension or compression, at right angles to each other, called principal stresses.&apos; To fully identify the stress, the values of P and Q and their directions or angle F must be known.

Jan 1, 1940

By David R. Mitchell

Many of the difficult operating problems of the preparation of coal for market, of sampling coal shipments and in the utilization of coal are caused by segregation in the coal mass. Segregation may be of two kinds: i.e., "size segregation," in which particles of the same size in a mass of coal containing a range of sizes collect together and "density segregation," in which particles of the same density or specific gravity in a mass of particles of varying density gather together. Mechanics of Segregation Size segregation cannot take place with closely sized coal. As the size range increases, the tendency for size segregation increases. Similarly, cleaned coal with particles of approximately the same specific gravity have very little tendency for density segregation. The wider the density range of particles and the more particles of different density, the greater the chances are for density segregation. The following discussion deals primarily with coal of a wide size range as screenings and of wide density differences as uncleaned or run-of-mine screenings. If a mass of coal containing particles of a wide size range is subject to the stream action of a moving current of water, the small particles are transported farther than the coarser. Particles of different density in a stream of moving water are subject to the laws of classification, the heavier settling out first. The familiar sluice box of the gold miner and the action of rivers and other streams in classifying material according to

Jan 1, 1938

By Bunting S. Crocker

EBBLE grinding at Lake Shore is not a temporary BlE wartime substitute. The tube milling plant, with a 1000 ton per day capacity, grinds a hard siliceous ore to 90 pct — 325 mesh. The plant, prior to using pebbles, was consuming 4.3 lb of 11/4-in. grinding balls per ton of ore, which amounted to 785 tons of balls per year. At September 1951 prices, $132.60 per ton, this steel cost amounted to $104,400 per year, or $0.285 per ton milled. By the Lake Shore method of substituting screened rock for this steel, all of this cost is saved. This is one of the major economies in Lake Shore mill practice. Regardless of the ultimate price of grinding balls, a change back to steel balls is not considered. The present pebble plant is more flexible than a steel ball plant and equally efficient. For example, if it is desired to change the size of grinding media, the pebble charge in any mill can be changed completely in 4 to 5 days, as against 76 days to change completely a 1-in. steel ball charge. To change pebble size it is necessary only to change two sets of screens and clean out the rock feed storage bin. This will take 8 to 10 days as against 3 to 4 months to clean out the customary supply of grinding balls kept on hand. Also it has not always been possible to purchase all desired sizes of balls at any price. In an analysis of savings effected by the use of the pebble mills, the flexibility of the Lake Shore grinding plant should be discussed, as it has a direct bearing on these savings. The plant has always used several units to handle tonnage rather than sending all the tonnage through a single unit. This principle may result in using small diameter mills, but no objection to that is seen. At no time has any advantage been found in cost per ton ground in large diameter mills. Both the capacity and the power of any mill varies as the diameter raised to the 2.6th power. Consequently large or small mills are equally efficient, and a plant, should be designed to use as many units or combination of units as is consistent with reasonable operating practice. Mills under 5 ft diam are harder to reline, etc. To define the case at Lake Shore, 2600 tons per day formerly were milled in seven 7x6-ft ball mills and twelve 5x16-ft (and two 6x16-ft) tube mills.* This gave an excellent test plant and an extremely efficient one. In this plant the ratio of ball mills to tube mills was 1:2. When the much cheaper pebble mills were substituted for the tube mills, this ratio was changed to one ball mill to four pebble mills to take the greatest possible advantage of the cheaper operating mill, i.e., the pebble mill. This flexibility without loss in efficiency has been an important item in the cost savings. It is interesting to note that the use of pebbles for fine grinding was proved first in the laboratory in a 12-in. ball mill. In fact, since 1934 all testing on — 8 mesh material has been done in this 12-in. mill. Scope of the Tests A paper on fine grinding at Lake Shore Mines was published in July 1940.&apos; This paper covered 7 years of intensive research on fine grinding as well as sizing methods and equipment, plant scale grinding tests on 5x16-ft tube mills with and without grate discharges both with 1-in. and -in. balls, the use of laboratory mills to evaluate plant changes, and several reports on classifiers and classification. In the following July the addendum report2 was added in which the idea of series-circuit grinding was introduced, and the results of running five stages of tube mills and bowl classifiers were shown. Since 1940, the ball milling end of the plant has been altered extensively as a result of tests on the use of 3-in. rods in 7x6-ft mills and the use of the Tyler repulping screen with from 7 to 14 mesh screens. These tests are lengthy and may be covered in a separate report later. The scope of this report is confined to ore ground by rod milling and ball milling until it passed through an 8 mesh Tyler Ty-rod screen. The —8 mesh screen undersize then was pumped to a primary bowl classifier in open circuit and the sands from the bowl sent to the primary pebble mills, see Fig. 1. In the pebble mill circuit the ore is ground to 90 pct —325 mesh (24 pct + 28 microns). In studying the flowsheet, attention should be paid to the efficiency of the classification equipment used. The Tyler repulping screen is an efficient machine on the 8 to 10 mesh separation, and the bowl classifier is equally efficient at the 325 mesh separation. Efficient classification is a necessity for series-circuit stage grinding. The ore is hard siliceous porphyry, 60 pct SiO,, 80 pct insoluble. Its grindability at different meshes has been shown near the top of the list in F. C. Bond&apos;s grindability tests.&apos; Lake Shore is not shown, but an adjacent mine with identical ore, Wright-Hargreaves, is. Reasons for the Changeover Since 1936 grinding balls have been rising steadily in price with no sign of stopping. For a mill that used 4.5 to 5.2 lb of grinding balls for every ton of ore ground this rise represented an alarming increase in grinding costs. In many cases the quality of the grinding balls fell off as the scrap steel became more difficult to obtain. The ratio of tube mills to ball mills increased with the use of the Tyler repulping screen in the ball mill circuit. Originally only 3.0 lb of balls per ton were used in the tube mills, and this

Jan 1, 1953

By H. Kahata, I. Iwasaki, Y. Takahasi

A combined process of segregation roasting-flota-tion or magnetic separation was developed to recover nickel from lateritic iron ores and oxidized nickel ores. An ore was mixed with a halide, such as sodium or calcium chloride, and a solid reductant, and roasted, whereby the nickel content was segregated out as discrete metallic particles. Either by magnetic separation, or by flotation using a sulfhydryl collector together with a heavy metal salt as an activator, the metallic nickel could be concentrated, Effects of such variables as the types and amounts of the halide and solid reductant addition and of the roasting conditions were extensively investigated. The concentration results on several types of ores from Japan, the Philippines, and New Caledonia are presented. Laterite is a residual product of rock decay in tropical and subtropical regions, and consists mainly of hydrated oxides of iron and alumina. Those derived from serpentine sometimes become enriched in nickel, cobalt, and chromium contents. Oxidized nickel ores are of the similar origin, but their nickel as well as silica contents are higher due to gamierite-type silicates. Apparently, nickel enrichment is more pronounced in the transition region between the surface layer of iron laterite and the underlying serpentine. Iron laterites often contain over 50% iron, and their reserve is reported to exceed 22 billion tons, corresponding approximately to 20% of the world iron ore reserve.1 It is readily apparent, therefore, why the iron laterites have attracted much attention of the steel industry as a potential source of iron ores. Numerous attempts to remove nickel and chromium as byproducts, have been reported in literature.&apos; Worldwide discoveries of high-grade iron ore deposits in recent years have inevitably lessened the interests in iron laterites. However, in view of the tremendous potential for their gross value and supplies of nickel, cobalt, chromium, and alumina along with iron, the problem remains as a challenge. Much of the chromium in laterites is present in the form of relatively coarse particles of chromite, and various classification methods have successfully been applied for its removal.2,3 The nickel, however, is intimately associated with limonite, and ordinary concentration techniques are totally ineffective. Much attention has, therefore, been given to hydro-metallurgical or pyrometallurgical means. Yet, all the known processes appear to have limitations either economically or for the use of products as iron raw materials due to a high residual content of nickel. Some attempts have been made to pre-roast laterites or oxidized nickel ores, particularly with sulfidizing agents, and to remove nickel either by magnetic separation,&apos; or by flotation.4 It is apparent that any such concentration process would require grain growth of nickel during roasting for effective separation. Oxidized copper ores are reported to be concentrated by the segregation roasting-flotation process,5 in which the ores are roasted with a chloridizing agent and a carbonaceous reductant in order to promote the growth of metallic copper through repeated cycles of copper chloride volatilization and its reduction on the solid reductant surfaces. Examination of a vapor pressure-temperature diagram of various metal chlorides indicates that a separation of nickel from iron may be effected by a similar process. In fact, the segregation roasting of laterites was reported to increase the extraction of nickel by the ammonia leach process, as compared to the ordinary reduction roasting.6 In the present article some of the preliminary experimental results of the segregation roasting, followed by either flotation or magnetic separation, on laterites and oxidized nickel ores are reported. The effects of various parameters in the roasting as well as in the concentration steps are discussed. MATERIALS AND METHODS An oxidized nickel ore from Thio, New Caledonia, and three laterites from Homonhon, the Philippines, Wakasa and Miyagawa, Japan, were selected for the

Jan 1, 1967

By T. F. Kassner

The dissolution kinetics of type 304 stainless steel in the Bi-Sn eutectic alloy have been investigated under the well-defined hydrodynamic conditions produced by the rotating-disc sample geometry. In addition, the mutual solubilities of iron, chromium, nickel, and manganese from 304 stainless steel in the eutectic alloy were determined over the temperature range 450" to 985°C. The convective -diffusion model for mass transport from a rotating disc was used to interpret the experinlental dissolution data. The dissolution process was found to be liquid-diffusion-controlled under specific conditions of temperature and Reynolds number. Liquid penetration into the 304 stainless steel resulted in a reduction of the di,ffusion-controlled mass flux and thus precluded the calculation of the diffusion coeficients of the four components from 304 stainless steel in the Bi-Sn eutectic alloy. The convective-diffusion model for diffusional limitations of electrode reactions and mass transport at the tationssurface of a rotating disc set forth by Levich 1,2 has found wide applicability in the investigation of electrochemical and dissolution phenomena in aqueous systems. Riddiford 3 and Rosner have reviewed the model and also include numerous references on work of this nature. More recently the rotating-disc system has been applied to the investigation of hetereogeneous reactions in liquid-metal systems. Shurygin and Kryuk 5 have measured the dissolution rates of carbon discs in molten Fe-C, Fe-Si, Fe-P, and Fe-Ni alloys. Shurygin and shantarin6 also studied the dissolution kinetics of iron, molybdenum, chromium, and tungsten, and the carbides of chromium and tungsten in Fe-C solutions with a rotating-disc sample geometry. In these systems it was possible to distinguish between diffusion and reaction control mainly through experimental confirmation of the velocity dependence of the dissolution rate predicted by the model. However in the absence of dependable solubility data and the virtual lack of diffusion data in these systems, a quantitative check of the magnitude and the temperature dependence of the rate was not possible. In many instances, estimates of the activation energy for solute diffusion and the diffusion coefficient based upon the experimental dissolution data are not credible. A recent study by this author7 has resulted in a critical test of the model in a liquid-metal system. The solution rates of tantalum discs in liquid tin were measured over a wide range of temperature and velocity conditions. In addition, the solubility and diffusion coefficient of tantalum in liquid tin were determined as a function of temperature. The latter data were used with the model to predict both the magnitude and the temperature dependence of the dissolution flux. In that work it was also deemed necessary to reevaluate the solution to the convective diffusion equation to incorporate the effect of the lower range of Schmidt numbers encountered in liquid-metal systems. Good agreement between the model and the experimental dissolution data in the region of diffusion control was obtained in the Ta-Sn system. The Bi-Sn eutectic alloy is used as a seal between the reactor head and the reactor vessel in the Experimental Breeder Reactor-11. The alloy is fused periodically prior to fuel-handling operations. In that connection, it was necessary to investigate the compatibility of the liquid alloy with the type 304 stainless-steel containment material. The results of a rotating-disc study in this multicomponent system are presented. EXPERIMENTAL METHOD The 5.08-cm-diam discs were machined from 0.317-cm-thick plate. Chemical analysis information for the type 304 SS material is given in Table I. The discs were ground flat on metallographic paper and given a final polish on Linde B abrasive. A thin support rod was threaded into the disc and the region around the threads was fused under an inert gas. The support rod was fitted with a quartz protection tube and then was attached to a supporting shaft which passed through a rotary push-pull vacuum seal. The disc and supporting shafts were dynamically balanced prior to insertion into the furnace tube. The apparatus is shown schematically in Fig. 1. The 58 pct Bi-42 pct Sn eutectic alloy melts were prepared from 99.995 pct pure Bi and Sn by fusing the components in a 7-cm-ID Pyrex crucible. The system in which the melts were made was evacuated to a pressure of 1 x 10-6 Torr and back-filled with purified argon several times before melting the charge. The ingot was reweighed and placed in a slightly larger-diameter Vycor crucible used in the dissolution runs. A run was started by lowering the disc into the liquid

Jan 1, 1968

By Paul Beck

WHILE the recrystallization properties of most of the practically important metals are known in considerable detail, those of lead are still relatively little known in spite of some valuable contributions in recent years. This condition probably is due to the difficulties involved in applying the usual methods of investigation. The microscopic method of discriminating between the elongated deformed grains of the familiar lenticular shape and the equiaxed recrys-tallized grains is not successful with fully refined lead: lenticular grains cannot be seen under the microscope with any amount of deformation whatever. The probable cause of this phenomenon was recognized long ago. With large deformation the time of recrystallization at room tem-perature is shorter than the period of preparation of the specimen for microscopic examination; with small deformation the deformed grains are not noticeably elongated in the first place. However, with small deformation the migration of the grain boundaries can be observed. The only systematic investigations yet published on the recrystallization of lead, those by R. S. Russell,1-3 make use of the conditions just described. Russell considered recrystallization completed when no further migration of boundaries could be observed. A serious objection to this method arises from the fact that there is no evidence to support the view that grain-boundary migration results only from recrystallization. If such migration does result from other sources after recrystallization is com-pleted-after the deformed grains have been replaced by new unde-formed grains-the "time of recrystallization" as determined by Russell may be too long. Furthermore, the method is subject to the above-mentioned limitation because of the unavoidable period of preparation of the sample. According to Russell, even with the fastest technique 5 min. elapsed before the deformed samples were ready for examination, and consequently no recrystallization time shorter than 5 min. could be measured.

Jan 1, 1939

By G. L. Tufford, R. L. Bleifuss

Low-grade manganiferous iron ores of Minnesota&apos;s Cuyuna Range, in general, do not respond to conventional mineral dressing techniques because of their fine-grained texture. Reducing these ores to magnetite with subsequent magnetic separation and flotation have not given satisfactory results because, in many instances, concentrate grade and manganese recovery are low. Metallization of iron and concurrent reduction of higher manganese oxides to MnO, as in the R-N process, followed by recovery of iron by magnetic separation and manganese by leaching, seems to be a technically feasible process. High-temperature x-ray diffraction studies show that solid-state reactions between iron and manganese, with the formation of intermediate iron-manganese oxides, occur during reduction and affect recovery of both iron and manganese from the final product. Solid state reactions also occur between FeO, MnO, and SiO, at temperatures as low as 900°C. The kinetics of these reactions are such that they become an important factor in the treatment of ores by the R-N process. These investigations suggest a temperature and gas composition cycle that would maximize both iron and manganese recovery. During the past ten years, iron ore shipments from the Cuyuna Range of Minnesota have decreased sharp1y. Because of adverse grade, structure, and cost, many Cuyuna ores are no longer competitive with high-grade foreign ores and domestic pellets. The low-grade manganiferous iron ores from the Cuyuna Range, in general, do not respond to conventional mineral dressing techniques because of their fine-grained texture. Reducing these ores to magnetite for subsequent magnetic separation and flotation has not given satisfactory results because concentrate grade and manganese recovery are often low. However, a technically feasible process appears to be metallization of the iron and concurrent reduction of manganese oxides to MnO with recovery of metallic iron by magnetic separation and extraction of manganese from the tailings by leaching. In 1962 the R-N Corp., with a grant from the Area Redevelopment Administration, conducted an amenability study of the metallization of manganiferous iron ore from the Cuyuna Range. The results of this preliminary investigation were sufficient to interest the Economic Development Administration in sponsoring further studies of the process with emphasis on secondary recovery of manganese from the nonmagnetic tailings. Inasmuch as the metallization process has considerable influence on the final form of the manganese - its texture and distribution between the magnetic concentrate and nonmagnetic tailings-the investigation included a study of metallization of the ore as well. Therefore, the investigation conducted at the Mines Experiment Station covered three interrelated phases: (1) laboratory R-N roasting studies and magnetic separation tests, (2) laboratory chemical extraction experiments of the nonmagnetic tailings, and (3) a mineralogical study of the crude ores and their various roast products. High-temperature x-ray diffraction investigation of the Fe-Mn-Si0,-0, system is the main topic of this paper and an extension of the mineralogical work. GENERAL GEOLOGY The Cuyuna Range is known for its complicated geologic structure, complex orebodies, and generally indifferent response to attempts at conventional beneficiation. Several geologists have made intensive studies of the Cuyuna Range, including Leithl (1907), ~darns&apos; (1910), Zapffe3 (1925), Grout and Wolff4 (1955), and schmidt5 (1963), whose study was the most comprehensive of all. The Range is covered with glacial deposits - till, out-wash, and lake sediments -up to 250 ft thick. Bedrock stratigraphic units of the Cuyuna Range consist of three tightly folded Precambrian sedimentary formations. The lower unit is the Mahnomen formation, composed of 2000 or more feet of argillite, slate, siltstone, and quartzite. The middle unit is the Trommald formation, which varies from 45 to 500 ft in thickness and comprises the major iron-bearing formation. The upper unit is the Rabbit Lake formation, consisting of over 2000 it of argillite, slate, and interbedded lenses of lean iron formation. In the central part of the Cuyuna Range, the units have been folded into a series of

Jan 1, 1969

By H. C. Schultz

CERTAIN local conditions were known to govern in large measure the successful adaptation of liquid-oxygen explosives to the large-scale blasting at Chuquicamata. The wide variation in hardness of the rock at this mine makes necessary the use of several types of explosives. A locally manufactured, relatively cheap black powder is used in blasting the softer waste and capping material, where a thorough displacement, breaks the ground sufficiently. Before the introduction of L. 0. X., an ammonia dynamite of about 65 per cent. strength was being used exclusively in the harder underlying orebody, where a strong disruptive as well as a displacement effect is required for breaking the ore. The L. 0. X., as developed for quarry work in the United States, has a practically pure carbon cartridge material, and the explosive has an extremely high rate of detonation, which should therefore cause it to usefully develop its full disruptive effect in hard ground. The individual blasts at Chuquicamata are large, black-powder shots which dislodge masses of rock averaging 250,000 tons each, and dynamite shots which dislodge masses averaging 80,000 tons each. It was desirable, therefore, to attempt to displace with L. 0. X. the faster, higher-cost ammonia dynamite used in the smaller blasts. It was not considered practical to attempt to displace the low-cost black powder with L. 0. X., as estimated costs showed no probable saving if this were accomplished. Since it was desirable to continue shooting relatively large blasts for effective operation, it was recognized that larger storage facilities than had been in use would be needed for the liquid oxygen. Because of the difficulty of transporting and discharging large storage containers of efficient design, the better plan appeared to be storage and discharge of the liquid at the place of manufacture, and transportation of the filled soaking boxes to the blast.

Jan 1, 1928

By C. E. Mills

STUDIES of ground movement and subsidence resulting from mining operations cover a broad field. It is also a very important consideration and one that eventually affects nearly every mining operation of any extent. The damage to surface buildings, removal of mine surface plants and replacements of main hoisting shafts must reach an astounding expenditure were these cost figures available over a period of years. Were the subject one of mathematical formula and dependent only on the angle of draw of the walls or country rocks, the problem would be relatively simple. Consideration must be given to depth and extent of workings; structural conditions of the orebodies and enclosing country rock; physical properties of these same rocks, including schistosity, bedding, jointing, slips, dikes, faults, and other structural weaknesses. The method of mining, extent of openings, supporting pillars, and amount of moisture or water underground are other pertinent factors. With such a large number of variable factors, it is apparent that the subject of subsidence is one that must be based largely on experience and results at other mines where conditions are somewhat comparable. In presenting this paper, it is the intent to describe the progressive results of past ground movements at the United Verde, to bring out physical conditions largely responsible for this movement, but to refrain from theorizing on the ultimate extent of subsidence resulting from future mining operations.

Jan 1, 1934

By George W. King

The yield strength of a dispersion-hardened W-3.8 vol pct Tho,alloy, in both the recovered and recrys-tallized condition, was investigated and cornpared with that ofrecrystallized pure tungsten over the temperature range of 325" to 2400°C. It is deduced that the Orowan mechanism is obeyed in the recrystallized alloy. In the recovered alloy, a further enhancement of the yield strength results from the retained substructure which is stable up to temperatures in excess of 2700°C. Temperature and strain rate cycling tests were also performed, and the apparent activation energy for the deformation process was derived. This activation energy, - 3 ev, for the recovered and also the recrystallized alloy was about the same as that for re crystallized pure tungsten. However, the activation volume of the recovered alloy, -10-2 cu cm, was about an order of magnitude lower than that of the recrystallized alloy or pure tungsten. This fact accounts for an enhancement oj- the temperature dependence of the yield stress of the recovered alloy. A dislocation velocity exponent of about 4 to 13 was deduced frorn the strain rate cycling tests , which is in good agreement with values reported for tungsten single crystals. VARIOUS theories have been developed to explain the enhanced yield strength of a metal containing a dispersed second phase of small hard particles. These theories are thoroughly reviewed by Kelly and Nicholson.&apos; The theoretical models can be separated into two types. The first type assumes direct interactions between moving dislocations and dispersoids. One of the most widely investigated models for this mechanism is the bowing out of dislocations between the dis-persoids and their subsequent pinching off in order to bypass the obstacles. This is the well-known Orowan mechanism.&apos; The second type is an indirect effect of the dispersion because of its ability to stabilize to high temperatures the substructure introduced by cold working. In this instance, the increment in the yield strength is expected to be inversely proportional to the square root of the subgrain diameter. In the present work, a quantitative study was made of the strengthening effect caused by a thoria dispersion in a recrystallized W-3.8 vol pct Thoz alloy over the temperature range 325" to 2400°C. The results are compared with the increment predicted for the Orowan mechanism based on the calculations by ~shb~.~ In addition, the alloy was tested in the recovered state so that any additional strengthening resulting from the substructure produced during fabrication could be measured. The respective contributions can be separated in this manner, provided that the particle size distribution of the dispersion remains the same in both the work-hardened and the recrystallized state. Particle size distribution measurements showed that this condition was met in the present work. I) EXPERIMENTAL PROCEDURES A) Material Production and Fabrication. The alloy investigated is essentially the same as that reported much earlier by ~effries,~ who also found the strength of tungsten to be improved by the thoria dispersion. The procedure for producing the alloy consisted of mechanically blending a thorium nitrate solution in proper concentration with tungsten oxide (WO3) powder, followed by hydrogen reduction to metal powder. After reduction, the dispersed second phase is present as thoria (Thoz). The pure tungsten powder used for comparison was produced in the same manner except that the thoria doping step was omitted. The powders were consolidated by cold pressing and self-resistance sintering in hydrogen. The resulting ingot had a cross section about 0.6 sq in. and a density about 93 pct of theoretical. The ingot was swaged to 0.174-in.-diam rod at temperatures varying from 1650°C initially to -1200°C near final rod sizes. Two intermediate recrystallization anneals were employed during fabrication. Analysis of the swaged rods is reported in Table I. B) Electron Microscopy Techniques. Carbon extraction rrPxcas prepared by a technique reported by ~00&apos; were used to quantitatively evaluate the thoria particle size and distribution. Electron nlicrographs of extraction replicas were taken at 20,000 times but were then enlarged two to three times in printing. The areas photographed were randomly selected. A Zeiss Particle Size Analyzer (Model TGZ3) was used to count and measure the sizes of all particles present on the print. About three thousand particles were counted in determining a distribution curve. Electron transmission microscopy was used to determine the effect of annealing on the substructures of the materials. Thin foils were produced by a two-stage thinning process. The rods were first ground on emery paper to ribbons about 10 mils thick and then a jet of 5 pct KOH was used to electrolytically reduce a portion of the cross section of the ribbon. Final perforation was achieved by immersing the specimen in a 5 pct KOH solution and electrolytically polishing at a current density of about 0.3 amp cm-&apos;. The foils were examined with a Hitachi HU-11A electron microscope. C) Tensile Testing. Tensile testing was performed in an Instron Testing Machine equipped with a radiation-type vacuum furnace which operates at about 1O"S torr at temperatures as high as 2400 °C. The same furnace was used for annealing the tensile specimens.

Jan 1, 1970

By S. D. Strauss

The marketing of nonferrous metals and of the ores and concentrates from which these metals are recovered is a fascinating trade, international in character, sensitive to every change in the economic tide, and complex in its organization. Each individual metal has its own marketing mechanism; no two are exactly alike. The differences sometimes are a matter of tradition rather than of necessity, but usually they have developed because of the very nature of the problems of producing or consuming the individual metal. This description, because of limitations of space, can do no more than indicate the major aspects of the trade and touch lightly on the marketing structure of each metal. The dictionary states that a market is a "meeting of people for selling and buying." In the case of nonferrous metals this meeting may occur on a half-dozen different occasions between the time the ore has been first mined and the time the refined metal is available for use by industry; or it may not occur at all until after the metal itself has been rolled, drawn, stamped, cast, or forged into a useful semifabricated shape. To illustrate: A Chilean miner may sell his small ore production to a custom mill, which produces concentrates that are sold to an ore dealer, who finances the shipments of the concentrates to a United States custom smelter, which buys these&apos; concentrates for conversion into blister, which is subsequently refined into electrolytic copper and sold. Conversely, much of the production of aluminum is in the hands of integrated concerns that mine bauxite, convert bauxite to alumina, smelt the alumina to produce aluminum, and then fabricate the aluminum into semifinished or even finished products before title to the material changes hands for the first time. Some nonferrous ores are not converted into metal at all but are sold by the miners or dealers directly b the ultimate consumers. A good example would be chrome ores used by the chemical industry. And of course a substantial part of the commerce in nonferrous metals is in scrap, which is the reconversion into useful form of metals that have long since been mined and smelted. Thus, one-third of all the lead used in the United

Jan 1, 1959

By Cyril Stanley Smith

Although alloys of copper and silicon were examined several years ago,&apos; and their excellent mechanical properties were shown, it was not until C. B. Jacobs 2 introduced manganese in small quantities to the alloys that they became of commercial importance. A few years ago The American Brass Company took over the patents and commenced to manufacture the alloy under the name "Everdur." The present study of the constitution of the ternary system was undertaken in order to reach a fuller understanding of the behavior of the alloy. Review of Previous WORK on the BinaRy Systems There have been no papers published dealing with the constitution of the ternary system, although some tests of the mechanical properties have been described," which indicate that there is a change in solubility with temperature. Copper-silicon System The copper-silicon system has been studied in detail by the author and is described in two papers published in 1928.V he portion of the diagram up to 8 per cent. silicon, as determined by this research, is reproduced in Fig. 1. The author&apos;s previous papers include a complete review of the work of other investigators and it is not necessary to deal further with this system here. Copper-manganese System The copper-manganese system has been investigated by several workers, notably Lewis,5 Wologdine,6 Sahmen7 and Schemtschuschny,

Jan 1, 1930

By James H. Courtright, Kenyon Richard

TOQUEPALA is a porphyry copper deposit in which mineralization is localized by a large breccia pipe formed in close genetic relation to intrusive rocks. The deposit is in southern Peru, 55 airline miles north of the small city of Tacna and the same distance inland from the port of 110. Quellaveco and Cuajone, geologically similar deposits, lie 12 and 19 miles north of Toquepala. Chuquicamata is 400 miles to the south. The deposit is high on the southwestern slope about 20 miles from the crest of the Cordillera Occidental of the Andes Chain. It lies in a mountainous desert where the steep southwesterly slope of the Andes is dissected by a succession of rapidly downcutting, deep canyons. Local topography is moderately rugged with a dendritic drainage pattern and an elevation of 8000 to 14,000 ft. Volcanic peaks along the crest of the Cordillera rise over 19,000 ft. Local precipitation, including a little snow, amounts to about 10 in. during January and February, but general runoff in the region is slight. Throughout southern Peru the springs and streams are widely separated. Crude canals irrigate small farms on terraced slopes along the streams and provide sparse subsistence to the semi-nomadic inhabitants. During the past decade, engineering and geological explorations of the region, as well as the mineral deposits themselves, have required construction of a network of several hundred miles of roads. Before this, roads extended only a few miles inland. Many areas still can be reached only by trail. Toquepala was briefly described in 19th century geographical literature as a copper deposit, and it received desultory attention from Chilean prospectors early in the present century. It was first recognized as a mineralized zone of possible real importance by geologist O.C. Schmedeman during an exploration trip for Cerro de Paso Copper Corp. in 1937. The discovery was late as compared to earlier recognition of Chuquicamata, Potrerillos, and Braden of Chile and Cerro Verde of southern Peru. This was due partly to the region&apos;s difficult accessibility but principally to the obscure character of the outcrop evidence of copper. From 1938 until 1942 Cerro de Pasco Copper Corp. partially explored the deposit by adits and diamond drillholes. This campaign was supplied by a 60-mule pack train continuously shuttling over a 30-mile trail. Northern Peru Mining & Smelting Co., a wholly owned subsidiary of American Smelting & Refining Co., undertook regional engineering stud- ies in 1945 and drill exploration in 1949. According to published data1 the deposit contains 400 million tons of open pit ore averaging a little over 1 pct Cu. It is currently undergoing large-scale development by Southern Peru Copper Corp., which is owned by American Smelting & Refining, Phelps Dodge, Cerro de Pasco, and Newmont Mining. Summary of Geology: The deposit is situated in a terrane composed of Mesozoic(?) and Tertiary volcanic rocks intruded by dioritic apophyses of the Andean Batholith. These formations are exposed in a northwesterly trending belt about 15 miles wide. Along the northeast they are unconformably overlain by Plio-Pleistocene pyroclastic rocks, which occupy much of the crest of the Andes, and along the southwest they are covered by the Moquegua formation of Pliocene(?) age. The mineralized area, oblong in shape and about 2 miles long, has been a locus of intense igneous activity. Several small intrusive bodies having irregular forms occur within and adjacent to a centrally located, large breccia pipe. The mushroom-shaped orebody consists of a flat-lying enriched zone of predominant chalcocite with a stem-like extension of hypogene chalcopyrite ore in depth within and around the pipe. This breccia pipe is relatively large and has been formed by repeated episodes of brecciation. Small satellitic pipes occur at random within a 2-mile radius of this central pipe. These too were individual sourceways of mineralization, although not always of ore grade. Within and around the zone of breccia pipes and mineralization there are a few faults and veins, but these are discontinuous random structures of minor significance. There are no regional or local systems of faults or other planar structures recognized which could account either for the mechanical development of the breccia pipes or for their localization as a group or as individuals. Hydrothermal alteration is pervasive in the zone of mineralization. Clay minerals appear to be abundant in places, but their percentages are undetermined. Quartz and sericite are the principal alteration products, and in many instances original rock textures are obliterated. The principal sulfides, hypogene pyrite and chalcopyrite and supergene chalcocite, occur mainly as vug fillings in the breccia and as small discrete grains scattered through all the altered rocks. Sulfide veinlets are relatively scarce. Sulfides are more abundant and alteration is more intense in certain rock units, such as the diorite and most of the breccias. Although the Toquepala mineral deposit is similar in most respects to the porphyry copper deposits of southwestern U. S., it most closely resembles the Braden deposit of Chile, as described by Lindgren

Jan 1, 1959

By A. R. Hendrickson, C. F. Smith

Hydrofluoric-hydrochloric acid mixtures have been successfully used to stimulate sandstone reservoirs for a number of years. Hydrofluoric acid (HF) has a specific reactivity with silica which makes it more effective than HCl for use in sandstone. Kinetics of the reactions of HF have been studied to determine the related effects of reservoir composition, temperature, acid concentration and pressure on the spending rate of HF. Secondary effects from by-product formation are noted and described. Predictions are made concerning the improvement in productivity resulting from HF treatment of skin damage. The kinetic order of HF reaction in sandstone was experimentally determined to be first order, i.e., the reaction rate is proportional to concentration. HF reacts faster on calcite than on clay, which, in turn, is faster than the reaction rate of HF on sand. Static conditions retard the HF reaction rate. As HF is forced into cores, there is a temporary reduction as a function of flow rate and acid concentration. Extensive deposition of calcium fluoride in acidized cores was not observed. Although some CaF, was defected, it was not considered a major source of damage in cores containing moderate amounts of carbonate. Other fluosilicates could be potentially more dangerous than CaF, in reducing permeabiliry. INTRODUCTION Hydrofluoric acid has been widely used in stimulation treatments since 1935, when mud acid was introduced to the petroleum industry. Originally, this hydrochloric-hydrofluoric acid mixture was intended to remove mud filter cake, but it has since been successfully applied to many other oilfield problems. Mud acid treatments have been unusually successful in sandstone reservoirs where hydrochloric acid is unreactive due to a lack of enough calcite in the formation. The relatively small amount of hydrofluoric acid present (2.1 per cent) reacts with sand grains, clays and traces of calcite which are generally present in sandstone reservoirs. Since hydrofluoric acid (HF) is the key to mud acid success, this research effort has been dedicated to gaining a more thorough understanding of the basic chemical and physical principles involved as HF reacts. Hydrofluoric acid&apos;s reactivity with silica makes it unique in application. Other mineral acids such as hydrochloric, sulfuric or nitric are unreactive with most silicious materials which comprise sandstone formations. A typical sandstone reservoir may contain 50 to 85 per cent silicon dioxide, more commonly called sand or quartz. Hydrofluoric acid reacts as follows: 4HF + SiO2 + SiFO + 2H2O The silicon tetrafluoride (SiF,) is a soluble gas, in some ways similar to CO2, and is capable of undergoing further reaction when held in solution by pressure. These reactions will be considered in detail later. Kinetics of the reactions of HF have been studied to determine the effect of reservoir composition, temperature and pressure on the spending of the acid. Secondary effects from by-product formation have been noted and described. The individual reactions of HF on quartz, glass and clay are reported. Mathematical correlations have been drawn, then applied to studies of HF spending in cores obtained from actual producing sandstone formations. The research reported herein is only the beginning of a continuing approach to better understanding and use of HF in petroleum reservoirs. THEORY AND DEFINITIONS Through the years, a concentrated effort has been made to understand the effects of many variables on hydrochloric acid (HCI) spending in limestone. Hendrickson el al., have given mathematical relationships for HC1 reactions which made possible the engineered approach to acidizing. The same variables—temperature, acid concentration, formation composition, pressure and permeability-porosity relationships—which affect HC1 behavior in limestone also govern HF behavior in sandstone. Insoluble by-products of HF reaction have been isolated and identified. Their effect on fluid flow has been measured under varying conditions in an attempt to evaluate the extent of possible damage and means of eliminating it. In general, HF follows the same reaction paths as HCI. It will react with limestone and dolomite with speed and ease. Thin sections of acidized cores show the reaction of HF with limestone or calcite faster than its reaction with either clay or sand. When HF reacts with calcite (CaCO,), theoretically, calcium fluoride (CaF2) is precipitated, and has been blamed as a major cause of reduced permeability. On the other hand, pH and pressure such as that encountered in an underground formation under acid treatment definitely retard CaF2 formation,&apos; so the whole question of CaF, deposition in wells is a subject for study.

Jan 1, 1966