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By Octavio G. Echavarria

HISTORY The Santander Mine is located on the western flank of the Central Andes of Peru, about 100 miles northeast of Lima, at an elevation of 15,000 ft. This complex sulphide orebody, whose predominant minerals are sphalerite and marmatite with recoverable amounts of galena and chalcopyrite, was discovered around 1920. In 1956 Compania Minerales Santander, a subsidiary of St. Joe Minerals Corp. acquired the property. Construction of the camps, concentrator and power facilities started in 1957. The mine, at first an open pit operation, and mill began production in January 1959. The initial capacity of the mill was around 120,000 short tons per year (stpy). Production has increased steadily to about 312,000 stpy at present. Production statistics are shown in Table 1. [ ]

Jan 1, 1970

By John A. Bonucci

AMAX Base Metals R&D, Inc. has developed technology for extracting and recovering platinum and palladium from spent automobile exhaust emission control catalyst. Our most promising route is a chloride-based hydrometallurgical flowsheet in which catalyst pellets or crushed monoliths are leached in HC1 with an oxidant at 95°C without agitation. Alumina co-dissolution can be limited by thermal pre-treatment of the catalyst. The leach solutions are treated by one of several precious metals recovery techniques to produce a high grade PGM concentrate. For the new generation of three-way catalytic converters which contain rhodium, an H2S04 preleach could selectively extract much of the rhodium while leaving the platinum and palladium behind. Capital and operating costs will be discussed.

Jan 1, 1984

By Rebecca Mae Summer

Increasing urbanization and industrial activity require increased supplies of sand and gravel. This means expanded surface mining and despoiled land near population centers. Highly competitive land use demands justify serious consideration of premining planning for multiple land use and reclamation concurrent with mining, 1-5 Formulating solutions to environmentally and economically sound uses requires a comprehensive approach based on properties of the natural resource base--geology, soils, and water. A study of sand and gravel mining within Pleistocene-Holocene fluvial deposits in Colorado County, Texas (Fig. I) illustrates how physical limitations imposed by the resource base are determined.6,7 Data from drillers logs of water wells, test boreholes, field observations, and laboratory analyses are used to evaluate these physical controls.

Jan 1, 1978

By Bruce A. Kennedy

The place of the young engineer in the mining industry has been the subject of a large number of keynote addresses, magazine articles, and papers in the past year. One of the best of these was the keynote address given by Mr. J. C. Kinnear, Jr. at the Fifth Annual Intermountain Minerals Conference in Vail. Colorado. Mr. Kinnear presented as part of his address the statistics of a Canadian survey Instigated to find out why young engineers and geologists are leaving the mining industry. The results of the survey showed four main reasons for leaving: 1) insufficient money 2) slow promotion 3) lack of association with senior engineers, as well as insufficient opportunity to keep abreast of technological development 4) geographic isolation

Jan 1, 1970

By J. E. Campbell, G. D. Calkins, N. M. Ewbank, M. Pobereskin, A. Wesner

GRINDING for size reduction affects the economics of many processes and products. It is essential as the first step in many industrial processes and is also a finishing step for materials with properties depending on particle size, such as talc, cement, and silica sand. Intermediate and fine grinding are vital operations in the U. S. cement industry, which is producing more than 250 million bbl of cement per year.1 Wear of the grinding media is a large part of the grinding operation cost. Problems encountered in grinding cement are so complex that evaluation of efficiency and economy of grinding media is difficult.2 It has been especially difficult to evaluate the relative effectiveness of different types of balls because there are no good testing techniques.

Jan 12, 1957

By John F. Barkley, J. W. Woomer, H. F. Yancey, H. B. Charmbury

The coal picture in 1955 was much brighter than in 1954, when the tonnage produced dropped to the 1939 level. Bituminous coal and lignite production are expected to approach 465 million tons, against 392 million tons in 1954, an increase of about 19 pct. On the other hand, the production of anthracite declined about 7 pct to some 25 million tons. There was marked improvement in coal consumption in all industrial lines except railroads. At the end of November 1955 the largest consumer, electric power utilities, had used about 126 million tons, an increase of some 22 million tons over the previous year. Coke-oven consumption increased about 19 million tons and coal coked in beehive ovens increased about 1.5 million tons, due to heavy coke

Feb 1, 1956

By J. Leland Myer

IN a precise study of Pennsylvania anthracites, the research on European. anthracites is of little value to us because of their different physical and chemical nature. Likewise, there can be little correlation with the physical properties of bituminous and lower rank coals. Although all high-rank coals are thought to have had a common origin, microscopic examination revealing essentially the same kinds of organisms in similar .states of preservation, the different physical properties apparently arise from the degree or kinds of metamorphism of these coals. Representative samples from the Pennsylvania deposits have been selected for analysis, together with graphitic anthracite, bituminous coal, and some of the common forms of carbon. A complete list, with descriptions, is shown in Table 1.

Jan 1, 1932

By AIME AIME

IN view of the approaching visit to Japan and the Imperial Steel Works at Yawata by our members, the following notes on present conditions in the industry there will be of interest. The data were collected by the representatives of the Bureau of Foreign and Domestic Commerce in Japan and are furnished here through the courtesy of the Department. In connection with the proposed suspension of both new and old Government undertakings and the general depression in building, which is expected to result from the retrenchment policy of the Government, some cuts in iron and steel prices have been made by dealers. It is expected that the Yawata Steel Works may reduce its round bar prices for November delivery by 1 yen.

Jan 1, 1929

The Pennsylvania State College, Mineral Industries Experiment Station, State College, Pa For publications address the Director The Pennsylvania State College through the Minerals Research Experiment Station has issued 10 Bulletins and three Technical Papers, from which the following have been selected as of greatest interest to mining engineers and geologists: Bulletin 1, An investigation of the properties of smitliing coals (1922), free; 2, Petrography of the Mica Pendotite Dike at Dixonville (1926), free; 4, The Helderberg Group from cen¬tral Pennsylvania to southwestern Virginia (1929), 25 cents, 5, Bentonite in Pennsylvania (1929), 10 cents, 6, Production data on Appalachian oil fields (1930), free; 8, Oil field waters of Pennsyl¬vania (1930), free; Technical Paper 2, Condition of water in coals of various ranks.

Jan 1, 1933

By William E. Bruce

In recent investigation of drilling processes, the U.S. Bureau of Mines measured the operating characteristics of two percussive drills. Basically, this entailed measuring maximum piston velocities while drilling. The maximum piston velocity is not necessarily the same as the striking velocity. The latter is usually somewhat lower1 because most commonly used drills provide an air cushion which slows the piston just before it comes in contact with the drill rod. Penetration rates for the two drills were determined in nine rock types, and the physical properties of the same nine rocks were measured and tabulated. Then the penetration rates were plotted against the individual properties to determine the general relationships on which methods for predicting drilling rates could be based.2

Jan 1, 1970

By George Holderer

THE relation between man-hours of labor and production may be correlated for any industry, and already it has been widely used in piece-work studies. It is not in general use as yet for recording labor efficiency of an enterprise or an industry. An exception to this is the Cement Institute, which tabulates the man-hours used in each operation and FIG. 1.-LABOR PRODUCTIVITY IN COPPER MINING. thus gets the total man-hours per barrel of cement. The writer knows of one steel company that keeps a complete record of man-hours for every operation from mining the ore to finishing the product. No doubt many others find the information useful, and such a study could be of value to the mineral industries.

Jan 1, 1935

By C. H. Reynolds, Robert C. Pruess

Late in 1954 exploratory drilling indicated a substantial orebody on the Rattlesnake claims of Woodmont Inc., a Continental Uranium Inc. subsidiary. Woodmont holdings are located about 35 miles southeast of Moab, Utah. Only a few miles north of Big Indian Valley and other Chinle-sand uraninite deposits, the claims are in an entirely different geologic environment. Detailed development drilling continued until the Deep North orebody was outlined, covering an area approximately 300 x 450 ft. All exploratory drilling and about 80 pct of development drilling was wet core. Chemical assays for each hole sample, applied at 1-ft intervals against the measured core length, were put into a conventional ore calculation formula. Forty-six holes were drilled to delineate the Deep North orebody.

Jun 1, 1956

By T. E. Scott, O. G. Koepke

DURING research currently in progress the need arose for interplanar angles and planar spacings to analyze crystallographic data obtained from hcp yttrium. In the absence of such existing information, a program was written in Fortran-11 language and processed on an IBM 7074 computer. The program and results have been assembled in report form to make them generally available.' Of the possible combinations of, only those most frequently encountered were employed. The ranges of h, k, and 1 involved were: However, not all combinations and permutations of the above appear in the tabulation because redundancies occur in several cases. Nevertheless, fifteen types of planes and all their equivalent planes have been included, giving a total of 109 sets of Miller-Bravais indices.

Jan 1, 1967

By A. Hellawell

Binary alloys of compositions intermediate between solid-solubility limits and eutectic compositions have been completely separated into primary phases and eutectic by freezing unidirec-tionally at very slow rates (10-6 to 10-5 cm per sec). The alloys examined were Pb-1 wt pct Ag, Al-20 wt pct Cu, and Al-42 wt pct Cu. The compositions and proportions were close to those expected from the phase diagrams and provided information about the solid/liquid interface at certain free zing rates. DURING the directional freezing of an alloy the solute distribution is controlled by the efficiency of mixing in the liquid,'" whereas diffusion in the solid state is of negligible importance. It is known3 that mixing by convection is very efficient, but complete segregation is only achieved at very slow freezing rates4-6 or with forced stirring in the liquid. ' Yue9 and Yue and clark10 have previously illus- trated partial separation of primary phases in alloys close to eutectic compositions. In the present work, taking binary alloys of compositions intermediate between the limits of solid solubility and eutectic compositions, it has been possible to achieve complete separation of the primary phases by directional freezing at very slow rates. METHODS AND RESULTS The alloys concerned were Pb-1 wt pct Ag, A1-20 wt pct Cu, and A1-42 wt pct Cu. As may be seen from the relevant diagrams,11 these alloys should segregate into approximately equal proportions of primary solid solutions and alloy of eutectic compositions. Specimens, -12 cm long and 1 cm wide, were frozen in horizontal tubes by withdrawal from a furnace. The lead alloy, prepared from materials of 99.999 pct purity, was sealed into evacuated Pyrex tubes and the aluminum alloy of similar purity contained in graphite boats under vacuum. The molten alloys were seeded with some 3 cm of solid to prevent irregular initial freezing rates and the last portions to freeze were ignored. At the slow freezing

Jan 1, 1965

By O. S. True, C. H. Herty

It is well known that manganese will desulfurize molten iron through the formation of manganese sulfide, which, being only slightly soluble in the metal, rises to and enters the slag where it remains as such (mixer slag) or is converted partly or wholly to calcium sulfide (basic open-hearth slag). The reaction by which manganese sulfide is formed is Mn + FeS = MnS + Fe. This reaction is generally considered to be reversible, although McCancel states that such is not the case. The experimental work was carried out to confirm the results of Roh12 as to the reversibility of the reaction. Six trials are herein considered. In each 200 gm. of electrolytic iron free from manganese and sulfur were melted in a pure zirconia crucible in a carbon resistance electric furnace. To the melted iron in runs 2, 3 and 4 metallic manganese and manganese sulfide were added to give 1, 2 and 4 per cent. manganese respectively, with 0.50 per cent, of sulfur in each. In runs 5, 6 and 7, metallic manganese and iron sulfide to give the same proportions of. manganese and sulphur as in runs 2, 3 and 4, were added. The melts were held molten in the furnace for an hour and then cast into small ingots. The results of these melts are as follows: Ingredients of Charge Analysis or InRot ManOaneBe, SulfUR, ManOaneBe. SULFUR, Run Material Charged PeR Cent. PeR Cent. Per Cent. PeR Cent. 2 MnS + Mn............... 1.0 0.452 0.636 0.367 3 MnS + Mn............... 2.0 0.50 1.57 0.310 4 MnS + Mn............... 4.0 0.50 2.81 0.230 5 FeS + Mn................ 1.0 0.50 0.647 0.397 6 FeS + Mn................ 2.0 0.50 1.45 0.374 7 FeS + Mn................ 4.0 0.50 2.73 0.195

Jan 1, 1925

By E. M. Murphy

Eight years ago the Hecla mine, a lead-silver producer, situated at Burke, Idaho, was producing ore from but two levels, the 300- and the 600-ft. All hoisting was done with a 12- by 16-in. slide-valve, double-reel, hoist. The hoist was being worked to its capacity and was unsuitable for hoisting from greater depths. As the work of opening a new level was about to be started, it became necessary to remodel the then-existing equipment or install a new hoist. The recent advent of electricity from Spokane had made available a cheaper power than steam. By a series of tests conducted throughout the Cæaur d'A1ene district, it was found that it cost $109 per year to generate a horse-power with steam. Electric power was to be had for $50 a horse-power per year. It was decided to substitute for the engines a motor-drive, of sufficient capacity to operate from the 900-ft. level, and ultimately install an entirely new hoist. After disconnecting the engines, installing a new shaft, and making a few minor changes, a 300-h-p., 2,300-volt, 514-rev. per min., variable-speed motor of the induction type was geared to the reel-shaft. The reels were supplied with 3/8- by 4-in. flat rope, and the duty of the hoist was about as follows: Cage, 1,700; ore, 2,600; car, 1,400; rope, 2,250; total, 7,950 pounds. The Bristol ammeter chart, Fig. 1, shows the combined current-consumption of the hoist- and mine-motors. The large intermittent load is clearly shown; this produced harmful fluctuations in the voltage of the long, lightly-loaded, 60,000-volt transmission-line from Spokane to the Cæmur d'A1enes. The power company received no compensation for the increased cost of producing power for this intermittent or fluctuating load. In order to protect its system from similar excessive

Jan 1, 1913

By Charles E. Lundin

Pressure-temperature-composition data were obtainedfor the Er-H system. Measurements werecar-ried out in the temperature range of 473° to 1223°K, the composition range of erbium to ErH,, and the pressure range of 10-5 to 760 Torr. Solubility relationships were established from these data throughout the system. Three solid-solution phases were delineated: metal solid solution, dihydride phase, and trihydride phase. The trihydride Phase decomposes at about 656°K and 1 atm pressure. The dihydride phase is stable to about 1023°K, but becomes more deficient in hydrogen above this temperature. The equilibrium decomposition pressure-temperature relationships in the two-phase regions, erbium solid solution plus dihydride and dihydride plus trihydride, were deter- The differential heats of reaction in these two regions are AH = - 52.6 * 0.3 and - 19.8 i 0.2 kcal per mole of Hz, respectively. The differential entropies of reaction are AS = - 35.2 * 0.3 and - 30.1 * 0.4 cal per mole HZ.deg, respectively. Relative partial molal and integral thermodynamic quuntities were calculated in the system to the dihydride phase. RARE earth metal-hydrogen systems have been the subject of general survey,1"4 and all have been found to form hydride phases. The heavy rare earths, of which erbium is a member, form dihydride and trihydride phases with different crystal structures, whereas the light rare earths form only a single-phase dihydride which expands without structure change, as hydrogen is added, to the trihydride composition. These materials are of interest primarily because of their theoretical properties, such as bonding, defect structure, and thermodynamic and electronic characteristics. Erbium has been studied in several previous investigations.5, 6 It was deemed desirable to more thoroughly and accurately define the system, both for the phase equilibria and the thermodynamic properties. I) EXPERIMENTAL PROCEDURE A Sieverts&apos; apparatus was employed to conduct the experimental measurements. Briefly, it consisted of a source of pure hydrogen, a precision gas-measuring buret, a heated reaction chamber, a mercury manometer, and two McLeod gages (a CVC, GM 100A and CVC, GM 110). Pure hydrogen was obtained by passing hydrogen through a heated Pd-Ag thimble. The hydrogen was analyzed and found to have only a trace of oxygen and nitrogen. A 100-ml precision gas buret graduated to 0.1-ml divisions was used to measure and admit hydrogen to the reaction chamber. The reaction unit consisted of a quartz tube surrounded by a nichrome-wound furnace. The furnace temperature was controlled by a recorder-controller to ±1°K. An independent measurement of the sample temperature in the quartz tube was made by means of a chromel-alumel thermocouple situated outside, but adjacent to, the quartz tube near the specimen. Pressure in the manometer range was measured to ±0.5 Torr and in the McLeod range (10-4 to 10 Torr) to ±3 pct. The hydrogen compositions in erbium were calculated in terms of hydrogen-to-erbium atomic ratio. These compositions were estimated to be ±0.01 H/Er. The erbium metal was obtained from the Lunex Co. in the form of sponge. The metal was nuclear grade with a purity of 99.9 pct +. The oxygen content was reported to be 340 ppm and the nitrogen not detectable. Metallographically the structure was almost free of second phase (<1 vol pct). A quantity of sponge was arc-melted for use as charge material. The solid material was compared with the sponge in the pressure-temperature-composition relationships. They were found to be identical. Therefore, sponge material was used henceforth, so that equilibrium could be attained more rapidly. The specimen size was about 0.2 grain for each loading of the reaction chamber. The procedure employed to obtain the pressure-temperature-composition data was to develop experimentally a family of isothermal curves of composition vs pressure. First, a specimen of erbium was wrapped in a tungsten foil capsule to prevent contact with the quartz tube. After loading the specimen, the system was evacuated to less than l0-6 Torr, flushed several times with high-purity hydrogen, and evacuated again ready for the start of the experiment. The furnace was then brought to the desired temperature. A measured amount of hydrogen was admitted into the chamber. Equilibrium was allowed to be attained, the pressure read, and the process then repeated many times until 1 atm of gas pressure was finally reached. Other isotherms were then developed in the same manner. The partial pressure plateaus were determined by another manner. In the solid solution-dihydride region a composition of approximately 1.0 H/Er was selected on the plateau. The temperature was varied throughout the range of interest. At each temperature level, equilibrium was achieved, the pressure read, and the next temperature attained. The temperature was cycled both up and down. In the dihydride-trihy-dride region, the plateaus were determined in the 473" to 651°K range only by heating to the desired temperature and not by both heating and cooling. The data were much more reproducible in this manner. Equilibrium required long periods of time. Specimens were initially hydrided to 2.8 H/Er, so that at the higher

Jan 1, 1969

By M. I. Jacobson, A. S. Yue, A. E. Vidoz, F. W. Crossman

An equation governing the concept of constitutional supercooling under the combined effect of concentration and temperature gradients was used to produce platelike Al-CuAl2 eutectic composites for mechanical properties studies. Compression specimens were prepared from a single-colony Al-CuA12 eutectic composite ingot, 2 in. in diam and 12 in. long. The specirrzens were cut such that the platelets were oriented parallel, 45 deg, and perpendicular to the compression direction. Since the ingot was of eutectic composition, The aluminum-rich matrix could dissolve 5. 7 wt pct Cu in solid solution, and therefore could be strengthened by precipitation hardening. Specimens were tested at room temperature and elevated temperatures in the unidirectionally solidified, solution-treated, and solution-treated plus aged conditions. The results were compared with those for the conventionally cast and extruded specimens. For the controlled material, the highest strengths were obtained with platelets oriented parallel to the compression axis. In the unidirectionally solidified condition, 0.2 pct offset yield strength was 32,000 psi; however, this was increased to 59,000 psi by solution treatment, and further increased to 90,500 psi by solution treatment and aging. The attainment of high compressive strengths in the Al-CuAl2 eutectic composites was interpreted in terms of the buckling of elastic CuAl2 platelets in the plastically deformed a aluminum matrix. SINCE the discovery of high-strength whiskers,&apos; scientists and engineers have made significant progress toward incorporating these whiskers into metallic matrices, forming composites for basic studies and structural application. The general procedure is to produce the whiskers first and then to bind them together with a ductile matrix. The production of whisker-reinforced composites requires tedious handling techniques,, particularly when it is desired to align the whiskers unidirectionally. Furthermore, the interfacial bond between the whisker and the matrix is frequently poor3 so that the resulting composite has strengths lower than expected. These disadvantages are generally true for any metallic composite produced by physically mixing the components. It is possible to eliminate these shortcomings by growing whiskers directly in the matrix material by eutectic solidification.4-8 In eutectic solidification, the matrix phase and a whisker phase are grown approximately simultaneously from a liquid of the same overall composition at the eutectic temperature. If the solidification process is controlled by varying the freezing rate, the temperature gradient, and the impurity content, platelike or filamentlike whiskers are produced parallel to the growth direction. The morphology of the grown-in reinforcement, i.e.. plates or rods, generally depends on the volume fraction9 of the dispersed phase present in the eutectic mixture. Since the unidirectional eutectic solidification is a one-step process, i.e., the liquid-solid transformation process, an excellent interfacial bond between the matrix and whisker is obtained. An additional advantage is that no special handling technique for whiskers is needed. In recent years, many investigators10-13 have studied the effects of growth variables on the micromorpholo-gies of binary eutectic alloys produced by controlled solidification. The study of their mechanical properties was initiated by Kraft and coworkers14-16 who found that the strength of cast A1-CuA12 eutectic alloy can be increased threefold by unidirectional solidification. In the A1-AL3Ni system, a strength of 50,000 lb per sq in, was reported for the unidirectionally solidified eutectic alloy, a value five times higher than for conventionally cast material. Thus, the unidirectionally solidified eutectics can be used as fiber-reinforced composite materials. In this paper, we shall first use an equation17 as a guide for the production of eutectic composites in general and the Al-33 wt pct Cu eutectic in particular. Experimental data supporting the theoretical prediction are given. Second, the compressive properties of the grown A1-33 wt pct Cu eutectic were thoroughly investigated in terms of platelet orientations, thermo-mechanical treatment, and temperature. The experimental data are interpreted in terms of a buckling model of fibers in elastic fiber-plastic matrix metallic composites. EXPERIMENTAL PROCEDURE Crystal Growth. The following experimental procedure was adopted for the production of controlled microstructures in the A1-33 wt pct Cu eutectic alloy. The controlled solidification was accomplished with a movable resistance-wound radiation furnace. Fig. 1 is a schematic drawing of the solidification apparatus. A water-cooled chiller was placed into a degassed high-purity graphite crucible containing the charge. Rubber stoppers wrapped with aluminum foil were used to seal both ends of the quartz tube through which a dried argon atmosphere was passed under a slight positive pressure. At both ends of the quartz tube, radiation shields were used to minimize heat loss. The quartz tube was held in place by two steel clamps and the furnace was drawn vertically by means of a steel cable against the steel truss which permits the furnace to move without touching the tube. The drive mechanism consisted of two pulleys, a counter weight.

Jan 1, 1969

CLEAR sunny skies that prevailed all through the 175th General Meeting of AIME were not the 1east of the details that resulted from the many months and man-hours of p1anning by the Southern California Local Section. Some 2600 persons left the 1953 Annual Meeting technically enlightened, having had a choice of over 300 papers presented by 400 authors to listen to, learn from, and criticize. During the meeting, Mike Haider turned over the Presidency of AIME for 1953 to Andrew (Drew) Fletcher.

Jan 4, 1953

By E. A. Gulbransen, W. S. Wysong, K. Andrew

The reaction of carbon in solid solution in a metal with the surface oxide fim on many metals may be inferred from thermo-dynamic calculations for high vacua and high temperature conditions. Holm has recently shown that oxide films may be removed from ferrous materials by heating in a vacuum at high temperatures and that carbon is the essential element in the reaction. considerable work has been described in the literature on the de-carburization reaction. Several general references may been 2,3,4 However, the nature of the mechanism involved in the decarburization is not well understood. Our interest in this reaction resulted from many attempts to degas and to reduce by pure and dry hydrogen the surface oxides on strips of various types Of chrome-nickel alloys. Some of the early experiments On the behavior Of &apos;3 pct chrome-iron in vacua of the order of 5 X lo&apos; mm and at a temperature Of 600°C have been reported.5 These experi-merits showed a &apos;low reaction with the residual Oxygen Or water vapor in the system and no reaction with hydrogen. This is in accord with thermodynamic data which would lead to the prediction that it is extremely difficult to maintain a hydrogen atmosphere at 600&apos; C pure enough to reduce Crz03 formed On the surface. The crystal structure of the superficial oxide film formed on 13 pct chrome- iron and Nichrome V has been investigated in the thin film range by Gulbransenr Phelps and Hickman,&apos; and shown to be "203. It Was surprising to us to note that when a specimen of Nichrome V containing approximately 80 pet nicke1 and 20 pet chromium was heated to 850°C in a high vacuum, the specimen lost weight. The rate Of weight loss was very temperature sensitive. A study of this reaction in vacua and in a hydrogen atmosphere is the subject of this communication. Type Reactions Let us consider the various reactions which may occur when a metal is heated in vacua, in a hydrogen atmosphere, or in an oxygen atmosphere. The number and kind of reactions will depend upon the chemical nature of the metal, its alloying constituents and the location of the alloying constituents. The metals used in this study are chrome-nickel alloys of the heater type, They consist essentially of chromium, nickel and iron, small amounts of carbon, silicon and manganese and traces of zirconium, calcium, aluminum and magnesium. The trace elements are added to improve the lifetime and other characteristics of the alloy when used as a heater. Seven of the more important reactions with which we are going to be concerned here are as follows: 1. Metal . (gas) F? metal + gas — degassing of the metal 2. zM(s) + y }i Oi(g) M MIOu(s) -oxidation

Jan 1, 1949