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By Elliot P. Rexford

IN the early days of concrete construction, the question of quality of sand or gravel to be used as aggregate in concrete was given little or no consideration. If the construction engineer had sufficient quantity for his structure within a reasonable distance, he was contented and gave no thought to the possibility that the material might have adverse physical, chemical, or thermal properties which could cause future deterioration of his concrete and possible failure of his structure. Today a very different situation exists. With the building of larger and larger concrete structures, with a longer and longer life expectancy, the quality of the aggregate material has become of major importance. Even in small concrete structures aggregate quality cannot be passed off lightly and the quality of the aggregate must be such as to give the anticipated life without costly maintenance. The first question to arise in the selection of an aggregate is what makes a sand or gravel suitable or unsuitable for use in concrete, and how can its quality be judged. No one rock type can be depended upon to furnish sound durable material in all instances. Granitic rocks, for example, make very satisfactory aggregates in some cases, but they are among the most unsuitable of materials when they are fractured, weathered, or highly micaceous. Limestones make excellent concrete aggregates on the one hand, and on the other they may be unsound and lack durability if they contain appreciable clay, they may have a harmful chemical reaction with the cement if they contain amorphous silica, or they may have thermal characteristics which make them highly unsuitable for use in concrete. Each rock, gravel, or sand must be proved on its own merits for the particular job under consideration. The selection of suitable aggregate materials may be divided into two major phases, the geological phase which is carried on largely in the field, and the testing phase which of course is a laboratory problem; both are important. Very often the geological phase alone is sufficient for the selection of satisfactory aggregates for minor structures but for major structures both phases must be thoroughly investigated. Geological Phase In the southwest part of the country nearly every major rock type, igneous, metamorphic, and sedimentary, may be found with all imaginable intermediate phases and in all imaginable stages of alteration. Frequently very different rock types, different as to geological age, composition, and condition occur very close together. Alluvium and stream-bed sands and gravels will consist of many different rock types and even ledge rocks may vary radically as to texture and composition within the area of a quarry site. Some of the rocks make suitable aggregate materials whereas others are highly deleterious in concrete. Too often the good and the bad occur together and more than ordinary caution is required in aggregate selection. Aggregate Sources: Concrete aggregates are usually obtained from stream-bed sands and gravels or from ledge rocks. Each has certain favorable and unfavorable characteristics and it is sometimes necessary to investigate both types to determine the most suitable source for a specific structure. Stream Beds: The predominant sources of aggregate materials in southern California and Arizona are stream beds. Vast quantities of sands and gravels are brought from the mountain ranges by the rivers during times of flood but most of these streams are dry a large part of the time and hence these deposits make easily accessible sources of aggregate materials. From many standpoints stream-bed materials make very acceptable aggregates. The gravel pebbles and the sand grains are

Jan 1, 1951

By Andrew Mayer

Early in 1942 National Lead Co. was requested by the War Production Board to construct and operate a plant for the Government to produce magnesium by the ferrosilicon process which had been developed by Dr. E. M. Pidgeon in the laboratories of the Canadian National Research Council. A contract with the Defense PlantCorporation was concluded in May 1942 and Magnesium Reduction Co., a wholly owned subsidiary of National Lead Co., was formed to carry out this project. The capacity of the plant was rated at I0,000,000 lb. of magnesium per year, equivalent to an average production of about 14 tons per day. The Process The process, in brief, is as follows: The raw materials are dolomite and ferro-silicon, 75 per cent grade. The dolomite is calcined, the calcine and ferrosilicon are ground and mixed and the mixture is briquetted. The briquets are charged into tubular retorts of chrome-nickel steel set horizontally in a furnace with the open ends projecting outside the front wall. The retorts are then closed and evacuated. Magnesium is liberated according to then reaction 2(MgOl CaO) + Si = 2Mg + zCaO, Si% It is distilled from the charge and con- densed on a removable sleeve in the throat of the retort. Sodium and potassium, if present, are also liberated, distilled and condensed on a "sodium condenser" in the end of the retort. At the expiration of the distillation period the retorts are discharged and the cycle of operations is repeated. For the rated daily capacity of 14 tons of magnesium there are required approximately 170 tons of dolomite, equivalent to about 85 tons of calcine, and 16.5 tons of ferrosilicon. The retort residue, a bulky powder which at present is waste, amounts to about 87 tons. Choosing the Site The investigation to select the location of the plant was conducted by the Research Laboratories of National Lead Co. This work included geologic and economic surveys of a number of districts, examination of dolomite samples by chemical, spectrographic and petrographic methods and large-scale tests of dolomite from several of the more promising localities. in the last-named tests 2-ton samples were put through the ferrosilicon process in the pilot plant of the Canadian National Research Council, under the guidance of Dr. Pidgeon. The conclusions drawn from the investigation, in regard to the quality of dolomite to be used in the ferrosilicon process, were: First, the dolomite should contain not less than 21 per cent MgO and not more than 2 per cent acid-insoluble material. Second, the dolomite should

Jan 1, 1944

By Dennis H. Laubscher

INTRODUCTION The selection of mass mining methods is the situation facing not only planners of new operations, but also those involved with cur- rent operations, including the eventual change from open-pit to underground. Increasing ground control problems on many mines, plus a better understanding of dilution and ore loss problems have meant a review of current mining methods and support techniques. Experiments are only successful if conducted in the right mining environment and on the right scale. Mining personnel have been known for their conservatism and will tend to persevere with an established method rather than change; often, hidden costs will obscure the correct economic assessment. An established mining sequence is not necessarily correct in the long term. However, recommendations to change are usually met with opposition because of inconvenience, temporary production problems and the desire for a trouble-free guarantee. In any planning exercise, care must be taken that time and money are not wasted in trying to achieve the unattainable. During the decision-making period, production personnel must be involved, and, if possible, they should visit similar omrations to that proposed. Co-operative production personnel will help ensure success. Descriptions of mining methods are available in technical papers and books, and it is not intended to discuss this aspect, but, rather, the various factors which must be recognised before arriving at a final selection. In another paper presented at this Conference (Heslop and Laubscher, 1981) factors affecting ore recovery and dilution are discussed in greater detail for various cave mining methods. PRELIMINARY CONSIDERATIONS Comprehensive Geological Data. Geological information is available during the exploration stage, but, often, core from exploration drilling is not analysed with the selection of a mining method in mind. Drilling costs are high, therefore the maximum benefits must be derived from this operation. Holes which have not intersected ore may provide data on possible shaft sites, and 35 mm colour slides of core, sound logging and geomechanics classification, will provide a record which can be used with confidence at a later date. Intersections of the various rock types should be kept for future study; for example, is weathering likely to be a problem, bearing in mind that this can be accelerated in the warm, humid atmosphere of an underground mine. The accumulation of data required to select a mining method starts with initial geological work in the target area, whether this be surface mapping or a diamond drill hole. Publications. As technical papers, reports and books are used in the selection of mining methods, an appeal is made to authors to describe the geological environment so that readers can relate to their own conditions. Not enough emphasis is given to the problems experienced and the techniques employed to overcome them. Follow-up papers are seldom written and we should be prepared to discuss our failures. Diagrams are often misleading, as the ideal and not actual situations are depicted. The caved ore/waste interface is not a straight line, and whereas this may not be significant in a diagram of a 200-117 draw height, it certainly is in sub-level caving with draw zones only 1 - 2 m width but up to 20 m high. SUMMARY OF FACTORS AFFECTING THE SELECTION OF UNDERGROUND MASS MINING METHODS (a) Regional rock stresses and mining geometry. (b) The geomechanics rock mass classification of the orebody and surrounding rock mass. (c) Ratio of the surface area of the ore/unpay interface to the contained ore which determines ore losses and dilution. (d) The cavability and fragmentation data of the ore and hangingwall. (e) The mineral distribution in the orebody and its dilution zone.

Jan 1, 1981

J. E. Stead, Middlesborough, England (communication to the author): Prof. Howe's valuable paper on cast-iron brings forward most prominently the correct explanation of the part played by combined carbon in pearlite and cementite, in determining the strength and hardness of cast-iron. On a previous occasioil I have shown that castings made by melting a white Cleveland iron and glazed iron, one containing 1.5 and the other from 4 to 5 per cent. of silicon, and each about 3 per cent. of carbon, were stronger than those made of ordinary foundry-iron; the difference in the final castings being a differ-

Jan 1, 1902

By Edwin R. Phelps, Charles W. Porterfield

BACKGROUND OF SURFACE MINING Surface mining refers to the process of removing the material (over- burden) overlying a coal seam and exposing the coal so that it can be loaded out and conveyed by trucks or other methods to the preparation plant or other facility. Surface mining has not always been important in the coal industry. In the early 1900s, almost all of the coal mined in the United States was mined by underground methods. In 1900, about 192 Mt (212 million st) of bituminous coal were mined and less than 1% was mined by surface methods. The development and use of larger equipment has allowed surface mining to gain prominence throughout the years. Table 1 shows the total production of coal by mining method in the United States for ten-year periods since 1920 and indicates the growth of surface-mined coal production. Surface mining will undoubtedly continue to account for a large percentage of the coal production in the US for many years because: 1) The capacity of surface mining excavators has continued to in- crease. Today, mining companies are using shovels (see Fig. 1) which are able to move up to 137.6 m3 (180 cu yd) in each bite and draglines (see Fig. 2) which move up to 168.2 m3 (220 cu yd) in each bucketful. 2) Increasing tonnage from the thick western coal seams is being produced by surface mining methods. 3) Surface mining has normally had lower costs and a better safety record than underground mining. 4) Surface mining normally recovers a much higher percentage of the coal reserve than can be recovered by underground mining. 5) Some coal measures can best be extracted by surface mining

Jan 1, 1981

The First Conference of the Powder Metallurgy Committee convened in the East Foyer of the Hotel Waldorf-Astoria, New York City, at 9:45 a.m., on Feb. 21, 1944, Mr. John Wulff, General Chairman, presiding. THE CHAIRMAN.-In behalf of the American Institute of Mining and Metallurgical Engineers I welcome all members and guests to this conference on Powder Metallurgy. We hope that this meeting will give expert and novice in the field a chance for discussion. Unfortunately, the subject has been overemphasized by some, and, of late, severely criticized by others. We have here today powder producers, fabricators, and engineers of different viewpoints, who can make the meeting a success. Such success depends not only on the caliber of the papers presented but more so on the discussion. To give you time for a free exchange of views, the papers have been shortened purposely. With the hope that you will all benefit by this conference, I shall turn the meeting over to the Chairmen of the morning session, Mr. Roland P. Koehring, of Moraine Products Division of General Motors, and Dr. R. K. Waring, of the New Jersey Zinc Company. SESSION ON DESIGN FACTORS IN POWDER METALLURGY R. P. Koehring and R. K. Waring presiding The opening paper of the session was presented by Mr. Fred P. Peters, as follows:

Jan 1, 1945

By Wittenau, E.

OPERATION of a pilot mill of 100 tons' daily capacity during 1930 and 1931 proved that the copper minerals of the Colorado and Clay sections of the Morenci ore body could be successfully concentrated by the flotation process. Economic conditions caused postponement of further testing work until late in 1938 when the former No. 6 Concentrator at Morenci was converted into an experimental mill of 1500 tons' daily capacity which was known as the Test Concentrator. The Test Concentrator began continuous operation on April 3. 1939, using such crushing and grinding equipment of the No. 6 Concentrator as was appropriate. Modern classifiers and certain flotation machines were installed and later other types of flotation machines, a large grate-type grinding mill. mechanical screens, a short-head cone crusher, and a disk filter were added to the test equipment. Operation was uninterrupted until Dec. 31, 1941.

Jan 1, 1942

By C. Pin, J. Bruce Wagner

In order to demonstrate the role of defect chemistry in the solid state to a process-metallurgy reaction, laboratory experiments were carried aut to remove copper from liquid lead using lead sulfide which had been doped to provide definite concentrations of cation vacancies. The removal of copper decreases in the order: bismuth- or antimony-doped PbS, undoped PbS or tin-doped PbS, and silver-doped PbS. The data are explained using the simple mass -action law and in terms of the exceedingly rapid interstitial diffusion of coppw in PbS to vacant cation sites. Results are in agree-ment with thermodynamic predictions and certain industrial practices that copper may be removed from lead below the limit of its coexistence with pure Cu,S and pure PbS. The role of defects in solids has been exploited in semiconductors and many device applications, in explaining tarnish formation, dissolution rates, and mechanical properties. The application of these principles to many process-metallurgical problems has not received as much attention. It was the purpose of this study to illustrate the role of defect structures of solids in a process-metallurgical application. When lead is refined, the ore, galena (PbS), is reduced by a series of operations to liquid lead (lead bullion) containing impurities such as copper, bismuth, antimony, arsenic, and silver depending on the original composition, the fluxes added, and the particular type of operation, see Fig. 1. In order to produce a pure lead, a series of refining operations are carried out. A typical lead-bullion analysis before drossing is shown in Table I. Copper is removed first as its presence increases the zinc consumption during the desilverizing process. For preliminary copper removal the lead bullion is brought to a temperature of 440°C in a kettle of 60 metric tons capacity. Some tar (or sawdust or resins) is usually added and the kettle is cooled slowly to 400°C while the liquid is stirred. A solid phase, called a dross, floats on top of the liquid and the particles of the solid phase adhere to the tar. This "hot dross" is collected. It contains mostly lead and copper which are partly oxidized and/or sulfurized if the lead bullion contains some sulfur.*

Jan 1, 1963

By L. E. Young

MUCH has been said and written on this subject and probably little new can be said. However, the point of view of the operating company changes from time to time, and more stress may be laid upon a subject today than was done some years ago, and it is with this changing point of view that the following observations are presented: The writer wishes to limit the discussion to views of a company mining bituminous coal, particularly to what the production department expects of the college grad¬uate. In an editorial in MINING AND METALLURGY for February, 1929, entitled "Is. Mining Engineering Passing?" it is stated that: It is not by accident that mining engineering courses have been general rather than special and form even today the only general engineering courses widely offered and followed by engineering students.'* * * even in this age of specialization, the mining engineers remain a body characterized particularly by broad knowledge.

Jan 1, 1929

Organization Place Date 1919 American Railway Engineering Association Chicago, 111. Mar. 18-20 Society of Industrial Engineers New York, N. Y. Mar. 18-21 American Electrochemical Society New York, N. Y. Apr. 3-5 National Foreign Trade Council Chicago, Ill. Apr. 24-26 American Iron and Steel Institute New York, N. Y. May American Institute of Electrical Engineers Lake Placid, N. Y. June

Jan 3, 1919

By R. H. Hiltz

Three titanium alloys, known to provide a mechanically unstable p structure after quenching, were selected as material for a study of the Origin and nature of stress-induced transformation. Data from hardness and tensile tests were used to study the initiation of marten site and the effect of the transfornation and transformation products on the mechanical properties of B titanium, particularly the stress-strain relationships. With the exception that the materials investigated showed a natural aging reaction in the P condition, their behavior is analogous to that of' stress-transforming stainless steels. The transformation starts after initial yielding and is essentially complete just prior to .maximum loading. Once initiated, the martensite itself is capable of propagating the transformation. The deforn-ing materials show low strength, high ductility, and a high strain-hardening exponent. In metallic systems which undergo a diffusionless transformation on cooling, it is possible to produce a similar transformatiorl by plastic deformation under special conditions. Dewez' in delineating Ms temperatures for the titanium-rich end of most titanium binary systems:, established the point of intersection of Ms with room temperature for those particular alloys. Alloy compositions which would quench to mechanically unstable p were established from these data. The first investigation into the possibility of stress-induced transformation occurring in titanium met with little success. It was concluded that such a transformation in titanium was possible only under very special conditions. Continued effort in this direction, however, showed certain Ti-Mo binaries to be highly susceptible to this phenomenon. This fact was utilized by Liu to study the habit planes of martensite and by Machlin and wenig5 to study the effects of stress and plastic deformation on the P to a prime transformation in titanium alloys. The first investigation of the mechanical properties of these alloys was conducted by Holden and his coworkers at Battelle Memorial Institute.' The potentiality of the alloys i3s sheet-forming material was recognized, and the data reappeared in a survey of this type of titanium material.? The initial optimism was tempered by the difficulties in obtaining homogeneous 2i-Mo alloys in commercial-size ingots. The increasing need for good sheet-forming material kept investigation in this direction active, resulting in the development of a commercial alloy of this type.' This study was undertaken to obtain a clearer picture of the mechanism of stress-induced transformation in titanium. MATERIALS AND TEST PROCEDURE Three alloys were selected for this investigation: one a Ti-Mo alloy; another a Ti-Cr-Mo alloy, known to deform martensitically; and the third, a Ti-V alloy with an Ms below room temperature and an Md above room temperature, but known to contain w phase in the quenched condition. The compositions of these alloys are given in Table I. These alloys were cast as 5-lb experimental ingots, employing skull melting. The ingots were hot-forged into 1-in.-round bars. Two 72-in.-thick slices were cut from each bar for hardness testing; the remainder was cut into 0.252-in. tensile blanks. The tensile blanks and one hardness disc from each bar were heated in salt to a temperature 100°F above the 0 transus, held 2/2 hr, and brine quenched. X-ray analysis showed the pieces to be 100 pct 8.* *Omega cannot be distinguished from p by the technique employed. Tensile blanks were machined to size after this treatment. TO prevent transformation due to machining stresses, the shoulders and gage length were ground. True stress-true strain curves were

Jan 1, 1960

By Luc Delaey, Horace Pops

The structure and morphology of thermoelastic and burst type martensitic phases that form upon cooling in Cu-Zn-Si p phase alloys have been studied by transmission electron microscopy. The martensitic phases are composed of a lamellar mixture of two close-packed structures with different stacking sequence, namely ABCBCACAB (orthorhombic) and ABC (fcc). Striations within thermoelastic martensite are most likely produced during interaction with impinging burst-type martensite and not as a consequence of secondary shears. In a study of the martensitic transformation in ternary Cu-Zn based 0 phase alloys1 the dependence of the martensitic transformation temperature, M,, with composition shows variations for elements within a constant valence subgroup and between different subgroups. Such variations are not reflected in a change in habit plane, which is approximately the same for each ternary alloy, namely in the vicinity of (2, 11, 12 Ip. The fact that the habit plane remained constant, despite large differences in M, temperature and electron concentration, suggested2 that the crystal structures of the martensitic phases could be nearly the same. Crystal structures of ternary Cu-Zn based martensites have been determined recently for alloys containing the three-valent elements gallium3, 4 and aluminm. The present studies have been made to examine the structures and morphology of the martensitic phase in ternary Cu-Zn based alloys containing a four-valent element, silicon. I) PROCEDURE Two alloys were prepared by melting and casting weighed quantities of the component high-purity metals in sealed quartz tubes under half an atmosphere of argon. They were subsequently remelted by levitation under a protective atmosphere of argon. After allowing for losses of zinc as determined by the difference in weight before and after casting, the compositions in atomic percent of both alloys were established to be Cu-33.5 Zn-1.8 Si and Cu-27 Zn-5.0 Si. These alloys were homogenized in the P-phase field for 2 days at 800" C. Bulk samples consisted of a martensite phase at room temperature, the M, temperature being approximately 30' and 200" for the 1.8 and the 5 pct Si alloys, respectively. Thin disks were cut from the ingots using a spark machine, and they were heated for 5 min at 800' and quenched into water in order to obtain martensite. These slices were thinned chemically at room temperature in a solution consisting of 40 parts HN03, 50 part H3PO4, and 10 parts HC1 and thinned further electrolytically by the Window technique, using a voltage of 15 to 25 v and a mixture of 1 part HN03 and 2 parts methanol, which was kept at a temperature near -30° c. Foils were examined by transmission electron microscopy using a Philips EM 200 electron microscope. 11) RESULTS AND DISCUSSION 1) Structure and Morphology. Fig. 1 shows the martensitic phase in the alloy containing 1.8 at. pct Si. This phase is composed of contiguous platelets, each containing striations. The direction of the striations changes at the boundary between individual platelets. These internal markings resemble the striations that are usually identified as stacking faults, as for example in Cu-A1 martensites6-a or the lamellar mixture of two close-packed phases in Cu-Zn-Ga marten-sites.3p '9 lo In the present alloys, selected-area diffraction experiments have been obtained in order to determine the nature of the striations. Figs. 2(a), (61, and (c) are electron diffraction patterns of an area inside a single martensite plate. Fig. 2(a) contains diffraction spots which correspond to two close-packed structures with different stacking sequences, namely ABCBCACAB (orthorhombic) and ABC (fcc). Spots belonging only to the fcc structure are indicated by arrows. By tilting the foil either the orthorhombic structure, Fig. 2(b), or the cubic structure shown in Fig. 2(c) may be obtained. When the foil is oriented so that only the diffraction spots of the orthorhornbic structure are present, bright-field illumination shows small lamellae, as seen in Fig. 3. In this figure the lamellae that belong to the fcc structure are bright bands inside the dark extinction contours of the orthorhombic structure. The boundaries of the lamellae are parallel to the basal planes of the orthorhombic structure and to the {Ill} planes of the cubic structure, the close-packed directions of both structures being parallel. The 5 pct Si alloy shows similar features as those described for the 1.8 at. pct Si alloy.

Jan 1, 1969

By Alan Stanley

The MacIntyre Development of the National Lead Co. is located at Tahawus, N. Y. The operations involve the mining and concentrating of a titaniferous iron ore to produce an ilmenite concentrate and a magnetite concentrate. Construction of the MacIntyre plant was commenced during the summer of 1941, when world conditions threatened to cut off the supply of Indian ilmenite. An open pit mining operation was developed and the crushing and milling equipment put in operation in July 1942. A general description of the operation was given in the Adirondack Issue of Mining and Metallurgy for November 1943. The metallurgy of the mill operation was described by Mr. Frank R. Milliken,* Plant Manager, National Lead Company, MacIntyre Development, and presented at the AIME New York Meeting, February 1948.

Jan 1, 1949

By Eugene Guccione

It would be extremely difficult and unfair to compare the United States to Australia when wondering about which of the two countries offers the best opportunities for running a mining operation. However, if somebody would ask "Where is the best place to mine outside the US?"-I'd answer without reservations: Australia. Some of my Australian mining friends will disagree with me for my giving their country such a high rating. And they'll probably accuse me of being an optimist by telling me, as one of them did, that "the difference between an optimist and a pessimist is that the pessimist is better informed."

Jan 1, 1977

By A. M. Ribe

Briefly stated, the mission of the traffic manager (currently called a transportation services manager) is to enable his firm to utilize to its best economic advantage the various systems and modes of transportation available to it to bring in its raw materials and ship out its finished products. The function of the transportation services manager is perhaps of more relative importance in industrial minerals operations than in industry and trade generally.

Jan 1, 1970

By D. E. Thomas

Oxidation rate constants were determined for Cu-Pd and Cu-Pt alloys as a function of alloy composition and temperature. Reaction products were identified. Relationship between oxidation rate constants and diffusion constants in the reaction zones is discussed. THE mechanism of oxidation of alloys is consider--'¦ ably more complex and not so well understood as that of pure metals. The oxidation of a one-phase binary alloy of which one component is a noble metal should logically be the simplest case of alloy oxidation, for in this case one is concerned presumably only with the oxidation of the base metal and the diffusion process by which it reaches the reaction site. This had led a number of investigators to study such systems. Probably the earliest work was that of Tammann and Rienacker' on the tarnishing of Cu-Au alloys at temperatures up to 300°C. These alloys oxidize according to the logarithmic law, that is, the film thickness is proportional to the logarithm of the time. The rate of film formation was found to decrease with increasing gold content. Raub and Engel² investigated the oxidation of Au-Cu, Cu-Pd, Au-Ag-Cu, Au-Pd-Cu, and Ag-Pd-Cu alloys at 750°C in air. These alloy systems form a continuous series of solid solutions at the temperature of oxidation with the exception of those containing silver. Au-Cu alloys oxidize parabolically, the rate constant decreasing slowly with increasing gold content up to about 15 atomic pct* Au, and more rapidly thereafter. An alloy with 14 pct Cu forms only a very thin layer of CuO on the surface and probably also a subscale.† Alloys containing more than 14 pct Cu have scales consisting of CuO and subscales of Cu,O embedded in nearly pure gold. The Cu-Pd alloys obey the parabolic law except for slight deviations for alloys containing 53 and 84 pct Cu. The overall oxidation rate decreases rather smoothly with increasing palladium content. A scale consisting of a thin layer of CuO and a thick layer of Cu²O and a subscale of Cu²O embedded in nearly pure palladium was observed for alloys containing 84, 53, and 30 pct Cu. An alloy with 19 pct Cu formed only a subscale of CuO embedded in nearly pure palladium, and an 8 pct Cu alloy formed only a thin film which was presumed to be PdO. The ternary alloys considered by Raub and Engel oxidized in much the same way as did the binaries. Wagner and Grunewald³ found that Ni-Au alloys, oxidized at 900°C in oxygen, formed a scale of NiO and a subscale containing NiO and gold. The overall oxidation rate increases with increasing gold content, passes through a maximum and then decreases to zero for pure gold. The fact that gold increases the oxidation rate was attributed to "pores" in the scale. Kubaschewski' investigated the air oxidation of alloys of platinum or gold with up to 10 pct Cu or Ni at temperatures in the range 300" to 1550°C. Parabolic behavior was noted for all alloys except Au-Ni, with rates decreasing in the order Au-Cu, Au-Ni, Pt-Ni, Pt-Cu. The diffusion coefficients for the latter three systems are known, and they decrease in the same order. However, activation energies for the oxidation of these alloys do not agree with the activation energies for diffusion in the respective alloy systems. Kubaschewski and Goldbeck7 nvestigated the oxidation of Ni-Pt alloys in air at temperatures of 600"

Jan 1, 1952

By I. S. Levy, J. L. Brimhall, B. Mastel

Specimens of' Hastelloy X-280, a low-cobalt version of the solid-solution- hardened nickel-base alloy Hastelloy X, were given a series of thermomechanical treatttzents. They were then Lensile-tested at room temperature and 1350°F. The Microstructures of the specimens tested at 1350°F were studied by electron Microscopy. Microscopy showed that dislocation tangling, caused by the cold working, mas still in evidence after aging-for 24 hr to temperatures as high as 1550oF. (Cr, Mo)23 C6, (Fe, Mo)6 C'. as well us an unidentifiable phase precipitale due to the combination of the thermomechanical treatments and subsequent tensile strain. The room -temperature and 1350°F tensile properties show a general increase ill strength and decreccse in ductility with increusing cold-work level. This is due to the dislocation taangling-. PerLurbatiot~s to this general trend occur- due to solid-solution weakening at the higher cold-work levels as a direct result of the preciplitation reactions. THE requirements for corrosion resistance and high-temperature strength place nickel-base alloys among the more promising materials for advanced nuclear reactor applications. However, when these alloys are irradiated at service temperatures, they generally suffer severe embrittlement'" and reduction in rupture life.3 Certain experimental treatments resulted in improvements in the tensile and stress-rupture properties of Hastelloy X-280, a solution-hardened nickel-base alloy.' To provide a basis for understanding these improvements, unirradiated tensile specimens were examined by electron microscopy. The results are reported in this paper. EXPERIMENTAL DETAILS Material. Hastelloy X-280, a low-cobalt version of Hastelloy X, is a member of the solution-hardened class of nickel-base alloys. The Hastelloy X-280 was obtained from 4- and 1-in: thick plates in the mill -annealed condition. Table I gives the chemical composition of the material as reported by the National Spectrographic Laboratories. ~x~erimental Treatments. Plates of suitable size, 12 by 3 by 1 in., or by + in., were cut under a water jet from the stock material and examined ultrasonic -ally for homogeneity of grain size and absence of voids. The acceptable plates were solution-treated at 2150°Ffor 1 hr and air-cooled. These plates were then reduced in thickness by cold rolling 0, 10, 15: or 20 pct along the original rolling direction. The plates were machined into buttonhead tensile specimens with a gage diameter of 0.125 in., with a gage length of 1.125 in., and with their tensile axes parallel to the rolling direction. The specimens were examined for quality of finish with a penetrant dye, ultra son ically checked for voids, and finally given a dimensional tolerance check with an optical comparator. The acceptable specimens were aged for 24 hr at either 1000" or 1500 F and air-cooled. These specimens were then held at 540°F in a water loop for approximately 18 days to qualify as controls for similar specimens irradiated under the same conditions of time, temperature, water chemistry, and flow rate. Table U summarizes the treatments. These treatments were investigated to establish whether prior precipitation and stabilization of carbide phases at strain sites within the matrix could reduce the amount of carbides available for precipitation at grain boundaries during service. Tensile-Test Conditions. Specimens were tested to fracture at room temperature or 1350 F in air on an Instron tensile-testing machine at a crosshead speed of 0.05 in. per min. The time for the furnace to reach equilibrium at 1350°F was approximately 30 min; soak time prior to testing was 15 min; and test duration was approximately 5 min.

Jan 1, 1968

By M. K. Foster

Ten horizontal retort zinc blocks of a modified Hegeler design are in operation at Nueva Rosita, Coahuila, Mexico, and produce approximately 170 t of spelter daily, or 62 000 t/year. A block consists of two furnaces of 448 retorts each, making 8960 retorts as the plant complement. Each furnace block is fired with natural gas and air maintaining the combustion mixture in the furnace always slightly reducing. No attempt to recover energy through waste heat boilers is made. The spelter moves to market by rail and truck either in palletized bundles weighing approximately 1060 kg, as loose slabs weighing 26.5 kg each, or as 1088 kg ingots. At present 46% of the metal is exported and 54% is consumed domestically in Mexico. The present day trend toward equalized or alloyed spelter, as well as special shaped castings results in sales of 35% of the entire plant's production. Sulfuric acid is also produced by the Contact Process using vanadium pentoxide as the catalyst. The plant is basically a Monsanto contact system, producing approximately 68 t of 100% sulfuric acid daily. Both 98.5% sulfuric acid and 20% oleum are available. All of the acid made is consumed in Mexico. Shipments are made in 26,900 dm3 tank cars.

Jan 1, 1970

By R. Sporcic, P. J. Mudra

During the past year personnel of the Roof Control Research Group of the Bureau of Mines designed and developed encapsulated hydraulic cells for measuring pressure changes in coal in situ. Preliminary results from feasibility tests in progress in the laboratory and field indicate that the cells respond favorably to changes in pressures associated with a coal-mining environment. The ultimate objective is to use these cells to obtain engineering information relating to coal bump or coal outburst phenomena. Mining research has experienced a remarkable growth during the past decade and from all indications should surge forward at even a greater pace in the future. This increased interest in mining research has been brought about by the ever-multiplying number of technical problems being encountered by the mining industry in its effort to produce pay-dirt tonnages safely and economically from greater underground and surface pit depths. Among the various divisions in the field of mining research, the study of ground stress has received a large part of the overall attention. Numerous technical papers have been written with regard to ground stress conditions around mine openings and yet the total usable knowledge concerning this subject is extremely limited. Research teams around the world are endeavoring to bridge the gap between theoretical and laboratory approaches and the solution to design problems in the field. The problem of ground stress is not a new one for the coal mining industry. Operators in both eastern and western coal fields of the United States as well as in many foreign countries have long been plagued with a number of ground stress problems, one of which is commonly referred to as the coal-mine bump. This term or phenomenon has been aptly defined by earlier investigators as the violent and sudden failure of coal and adjacent rock. Direct results of such failures have been the loss of human lives and thou- sands upon thousands of dollars of sustained mine damages. In an effort to alleviate the magnitude and frequency of these failures, mine operators have employed and are presently employing various corrective techniques. These include: Inducing failure in heavily stressed areas by augering large-diameter holes into stressed pillars, using extensively yield-able steel arches in both long-term haulage and short-term face entries, backfilling unused or abandoned entries with mine waste to gain additional support, and using systematic pillar coal panel extraction techniques including mechanized longwall mining. The Health and Safety Activity of the Bureau of Mines has for a number of years contributed considerable time, funds, and talent in an effort to define better the ground stress problems associated with coal-mine bumps. As a part of this investigative program, in situ ground pressures are presently being studied in coal mines located in West Virginia and Utah. The description and development of the device being used to measure these pressures is the specific topic of this paper. CHOICE OF INSTRUMENTATION After consideration and evaluation of the various instruments and techniques that are being used by researchers in the field of rock mechanics to detetmine in situ stresses, a simple hydraulic system was selected for detailed investigation. Aside from simplicity, a hydraulic system is relatively inexpensive and also eliminates the need for electricity in its installation and operation. The hydraulic device referred to is, in essence, a simple unidirectional pressure-measuring cell. Hydraulic cells, which had been used for measurement of pressures in hard rock, were investigated but found not entirely suitable for use in coal, particularly since they involved (1) preparation and emplacement of cement grout at the test site, and (2) a waiting period before the cells became operational. At the outset, it was decided that certain design parameters be established. The cell should be simple and inexpensive, constructed of materials readily obtainable and easily built in the laboratory or field by unskilled labor. It was further decided that it was desirable to encapsulate the cell in a suitable mate-

Jan 1, 1963

By C. P. Miller

In order to determine the usefulness of geochemical and biogeochemical prospecting for nickel, ten localities representing several types of nickel occurrences were selected as sites from which to collect plant and soil samples. This report covers the investigations in two of the areas. After a brief geologic description of the areas, the author presents details of the experimental tests and resulting data. Conclusions drawn from the studies led to several general guides for further prospecting. In a study of the usefulness of geochemical and biogeochemical prospecting for nickel made about three years ago, approximately ten localities, representing several different types of nickel occurrences, were sampled and about 1500 samples of plant and soil were collected. This report will cover briefly the data and results for two areas, and a summary of guides for prospecting. DESCRIPTION OF AREAS SAMPLED One locality is the Red Flats nickel prospect in Curry County, Ore., about six miles southeast of Goldbeach, and the other is the Little Rocky Creek prospect in Stillwater County, southcentral Montana, just southeast of the Benbow chromite mine. The Oregon area is a lateritic-type nickel deposit formed on a nickel-rich serpentinite peridotite complex, similar to the Josephine intrusion in southwestern Oregon. The Montana area is a nickel prospect in norite, peridotite, and related rocks of the Stillwater igneous complex. The Stillwater complex is a series of layered basic and ultrabasic rocks, with a layer of norite-gabbro at the base and a series of peridotites and gabbros above. The nickel in the Oregon deposit occurs in both the peridotite and the overlying soil. A deep lateritic soil is developed locally on the peridotite and serpentinite and constitutes the ore. The average nickel content of the lateritic soil is less than 1 pct, whereas the nickel content of the weathered peridotite is about 1 to 1.5 pct. The nickel occurs as garnierite (Mg, Fe, Ni, Mn)3 (OH)4 (SiA1)2O5 in the soil and in the olivine and pyroxene in the peridotite where it probably substitutes for Fe2+ or Mg2+ in the silicate lattices. Nickel is found in three distinct ways in the Still-water rocks: 1) it is in the olivine and pyroxene minerals in norite, harzburgite, etc.; 2) it occurs as widely disseminated grains of pentlandite-pyr-rhotite, which tend to be concentrated in the lower norite band; and 3) it occurs as discrete bodies of pentlandite-pyrrhotite and chalcopyrite which are localized in the norite zone, close to the contact with the underlying rocks. The nickel content of the norite is probably less than 1 pct, and the nickel content of the pods and lenses within the norite is about 1 pct. PROSPECTING APPROACH Although the areas are different geologically, the approach in prospecting them is fundamentally the same. The procedure is twofold: 1) a rapid reconnaissance survey to outline an area of high nickel content, and 2) a more detailed survey to outline zones of possible ore grade within the area of high nickel. The possible ore at Red Flats is concentrated in the lateritic soil, whereas at Little Rocky Creek it is in the sulfide pods. Both types are surrounded by an area of relatively high nickel content. CHEMICAL ANALYSIS Chemical analyses of nickel were made by a di-methylglyoxime colorimetric test, similar to the standard test for nickel, utilizing concentrated sul-furic acid for extraction. The lower limit of detection for nickel in soil by the method used was about 10 ppm and for nickel in plants about 5 ppm. The relative deviation was about 25 pct. SOIL PROSPECTING General Statements: A summary of the approximate average parts per million of nickel in soil, as compiled from the literature and from my study, is given in Table I. Selected references are given at the end of the paper. Few of the investigators reported the type of extraction or analysis, so the data given may not be strictly comparable to mine, which were made with a sulfuric acid extraction. Any nickel concentration greater than these average values might be considered anomalous, although each area must be studied in relation to the surrounding rocks. Method of Soil Sampling: The soil samples were taken in a zone from 1 in. to 1 ft below the humus layer, and within a 15-ft radius around a station.

Jan 1, 1961