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By Frederick N. Rhines, Robert F. Mehl

It has been shown elsewhere1 that the data on the rates of diffusion in solid metals are fragmentary and in many cases unacceptable. As a result, relatively little is known concerning the factors determining rates of diffusion and the variations in these rates with temperature. The first form of Fick's law (equation 1 below), in which the diffusion coefficient D is assumed invariant with composition, has been recognized for many years as only an approximation. The differential equation representing the second form of Fick's law (equation 4 below) has only recently been integrated by Matano,2 and unfortunately only in cases where a full diffusion-penetration curve (concentration-distance curve) has been obtained can the Matano solution be applied. The proper analysis of diffusion data is thus confined to the data of Grube and Jedele and of Jedele. 8 These data are essentially for one temperature alone and do not furnish any information on the variation of the activation heat of diffusion, Q, with concentration: no information exists on the variation of Q with concentration within a single solid solution field. 11 Much of the argument concerning the properties of metals that determine D and Q has been drawn from data in which variations of the quantities with concentration are unknown, for these data have been taken from experiments that could not furnish this information. Speculation concerning the properties of metals that may be effective in determining D and Q on the basis of data in which the chosen D and Q values are averages over wide concentration ranges of values at particular concentrations, ranges often of 100 per cent, is likely not to be fruitful.

Jan 1, 1938

This paper presents an overview of the strategy adopted to bring the Ballymoney opencut lignite deposit to an advanced stage of mine design and confidence. Certain aspects of the project differentiate it from the normal Australian experience. These include the thick overlying glacial drift, the proximity to established infrastructure and the wide fluctua- tions in annual lignite demand. The incorporation of these factors in the mine plan are discussed. The deposit area is located near the town of Ballymoney, in Northern Ireland. In July 1986, after winning an internationally competitive tender, Meekatharra Minerals Ltd commenced an exploration programme designed to delineate reserves to supply a 450 MW power station. In less than eighteen months, a complete evaluation was undertaken and a price submitted in December 1987 to the relevant authorities for the supply of lignite. Subsequently, UK government consultants and significant inter- national banks have endorsed the findings. The mining study commenced with the evaluation of various develop- ment strategies, followed by selection of the most viable mining method and equipment. The equipment selected will mine four million tonnes of lignite and eleven million cubic metres of waste each year. In year 15, the waste removal requirement increases to almost seventeen million cubic metres. This results in an average strip ratio over the mine life of three cubic metres of waste per tonne of lignite. The quality of the product delivered to the run of mine conveyor transfer point, based on maximum resource recovery, will include heat content of 8813 kJ/kg (3789 Btu/Ib), ash content of 28% and moisture content of 40%.

Jan 1, 1989

By C. Wieckert

Concentrated solar energy can be used as heat source for the production of metals. One of the most promising respective processes, the solar carbothermic production of Zn from ZnO, is investigated within the European research project SOLZINC, a cooperation of institutes and industries from France, Germany, Israel, Sweden and Switzerland. The solar produced Zn can be used as commodity or as an energy carrier for further processing on demand to electricity in Zn-air fuel cells/batteries or to generate hydrogen by reaction with steam. In both cases the Zn is oxidized to form ZnO, which can be recycled back to the solar plant. In these cyclic processes Zn acts as a means to store and eventually transport solar energy. Second product of the solar process step is a CO-rich offgas, which may e.g. drive a gas engine or may be shifted to hydrogen in a conventional reaction with steam. A pilot plant using 300kW concentrated solar power input has been constructed and operated successfully. 86mass-% of ZnO mixed with 14mass-% of charcoal are reacted to produce Zn and CO at a temperature of about 1200°C, yielding about 50 kg gaseous Zn per hour. Zn-dust with 95% purity is recovered from the offgas system that was designed to produce Zn for Zn-air fuel cells. Based on the results and findings from the pilot plant, a two tons Zn/h solar demonstration plant has been designed conceptually. Cost studies have been performed and scenarios for producing electricity or H2 via these ZnO/Zn-cyclic processes are evaluated.

Jan 1, 2006

By Frederick N. Rhines, Robert F. Mehl

IT has been shown elsewhere1 that the data on the rates of diffusion in solid metals are fragmentary and in many cases unacceptable. As a result, relatively little is known concerning the factors determining rates of diffusion and the variations in these rates with temperature. The first form of Fick's law (equation 1 below), ‡ in which the diffusion coefficient D is assumed invariant with composition, has been recognized for many years as only an approximation. The differential equation representing the second form of Fick's law (equation 4 below) has only recently been integrated by Matano,2 and unfortunately only in cases where a full diffusion-penetration curve (concentration-distance curve) has been obtained can the Matano solution be applied. The proper analysis of diffusion data is thus confined to the data of Grube and Zedele and of Zedele.§ These data are essentially for one temperature alone and do not furnish any information on the variation of the activation heat of diffusion, Q, with concentration: no information exists on the variation of Q with concentration within a singles olid solution field. 11 Much of the argument concerning the properties of metals that determine D and Q has been drawn from data in which variations of the quantities with concentration are unknown, for these data have been taken from experiments that could not furnish this information. Speculation concerning the properties of metals that may be effective in determining D and Q on the basis of data in which the chosen D and Q values are averages over wide concentration ranges of values at particular concentrations, ranges often of 100 per cent, is likely not to be fruitful.

Jan 1, 1938

By R. A. Harrington

THE structure of anodic films formed on aluminum and other metals under varied conditions is not well known despite the wide use of such films both as protective coatings and as the dielectric medium in elec-trolytic condensers. The present work was undertaken as a survey of the possibilities of electron diffraction in the investigation of anodic films, especially in comparing the properties of anodic films formed under dif-ferent sets of conditions and subjected to various subsequent treatments. In addition, an effort has been made to compare surface films formed on aluminum by anodic treatment with surface films formed by heating, immersion in chemicals, etc, The electron diffraction method in many cases has been successfully applied to the study of thin surface films. Its principal advantage is that it can be used without removing the films from the base material upon which they have been formed. The low penetrating power of electrons, in the "reflection" diffraction method which has been used in this work, prevents the appearance of diffraction patterns from substances at depths greater than about 100 Angstrom units (10-6 cm.). Different investigations of the structure of anodic films have shown widely varying results, depending on the methods used in preparing the films. Apparently under some conditions these films are crystalline and under other conditions they are amorphous, and it has been difficult to say which type of structure will be found in any particular case. Schmid and Wassermann's' X-ray diffraction patterns of eloxal? films show two broad, diffuse bands, which these investigators attribute to finely divided cubic y-Al2O3-§ Burgers, Claassen, and Zernicke3 obtained sharp X-ray

Jan 1, 1940

By Paul J. Barrett

The Bureau of Mines evaluated a sulfurous acid-sulfuric acid process for recovering alumina from clay, in which clay is leached. successively with sulfurous acid and sulfuric acid. The resulting aluminum sulfite and aluminum sulfate solutions are combined and heated to produce a basic aluminum sulfate and sulfur dioxide. Alumina is extracted from the basic aluminum sulfate as sodium aluminate by leaching with dilute sodium hydroxide. After desilication, sulfuric acid is used to precipitate alumina as alumina trihydrate, which is then calcined to alpha-alumina. The estimated fixed capital cost for a plant producing 1,000 tons per day of alumina is about $74 million on a 1971 basis. For comparison with previous alumina-from-clay evaluations, the estimated fixed capital cost for the plant is about $67 million on an M and S Chemical Equipment Index basis of 24.0.0, which is equivalent to a 1960 cost level. Because the operating cost is highly dependent on fuel and electric power costs, graphs are included to show the effect of these items on the operating cost. On a 1971 basis, with natural gas costing 35 cents per million Btu and operating labor costing $4 per hour, the estimated operating cost is about $100 per ton of alumina. On a 1960 basis, with labor costing $2.30 per hour and natural gas costing 25 cents per million Btu, the estimated operating cost is about $86 per ton of alumina.

Jan 1, 1973

By J. A. B. Forster

W. G. WOOLF*—The paper has a wealth of data that take careful, detailed study. As has been indicated the highlights can be only touched in the paper. The design and the arrangement of the rabble teeth as well as some of the other details of operation show a very careful study and a scientific approach to the problem which in most plants using hearth roasters are matters of trial and error with empirical conclusions and, perhaps too often, just arbitrary supervisory preferences which may be erroneous. Here the problem has been approached from a scientific angle which think well merits careful study. The ability to treat the tonnages they get through these furnaces think is made easier by reason of the high sulphide sulphur in the resulting calcines which the balance of the plant—the leaching and so on—can cope with. As indicated by Mr. Weldon in his dis- cussion earlier this morning, in most zinc plants an attempt is made to have as low a sulphide sulphur content in the roaster calcine as possible. But in the operation of the Risdon plants, they are able to cope with sulphide sulphur content up to 5 pct which is far beyond the amount of sulphide sulphur that can be handled elsewhere. I think the autogenous roasting is made easier because driving out the last percentages of sulphide sulphur brings on the necessity for extraneous heat, and that is further exemplified because even at Risdon the author shows the desirability of using some oil to better the operation, particularly for uniformity of roasting results and to obtain more regularity of furnace operation. A. A. CENTER*—Regarding the hard crusts in the beds of the furnace and autogenous roasting, the paper speaks of the former being due, at least to a considerable extent, to lead sulphide in the crusts. I wonder if the author has considered the hard crusts as being due in large part to zinc sulphate. While I was developing large zinc operations we ran into hard crusts which had to be dug up. I took several lumps which were so hard they showed the marks of the rabble teeth very plainly and kept them in my office for some weeks. A visitor came along one day, and as he was having similar troubles, I told him what we were doing about ours. I started to pick up one of these lumps and to my amazement the thing crumbled in my hands whereas originally it had been so hard it wore the rabbles down very rapidly in the furnace. I sent the sample to the laboratory and found that it analyzed very high in water-soluble zinc and sulphate-sulphur. The crumbling of the lumps was evidently due to the anhydrous zinc sulphate gradually taking on moisture from the air and forming crystalline zinc sulphate seven parts water. The increase in volume would, of course, result in disintegration of the lumps. As to getting a high tonnage in the autogenous roast, that is partly because of finishing at about 5 pct sulphide sulphur. It is a real job to get down to, say, ½ pct sulphide sulphur, which is what is usually desired, and still put through a good tonnage.

Jan 1, 1950

* Kennecott Copper Corp. gets Charles R. Cox as president on Jan. 1. Mr. Cox is resigning his position as president of Carnegie-Illinois to take the new post with Kennecott, left vacant by the death of Mr. Stannard in September. •The ECA signed a contract in December to advance X3,600,000 to Newmont Mining Corp. to aid development of lead and zinc mines in French Morocco. The funds are to be repaid in lead and zinc for the United States' stockpile over a period of seven years. The mines are owned by the Societe des Mines de Zellidja, with which organization Newmont is associated. • Under the direction of John M. Brooks, Jr., general manager, the Matahambra mine in Cuba, will probably produce sufficient tonnage to make 4 million lb of copper per month during 1950. The grade is presently running between 7 and 10 pet. •S. H. Ash reports that the fatality rate per million-man-hr for the anthracite industry for 1949, through November, is 0.78. This is 15 pct better than that achieved during 1948, which was the lowest fatal injury rate in coal mining history. The first full year on record without a major disaster was recorded in 1949 (p. 34). •The Atomic Energy Commission has authorized the production of 200 lb of uranium metal for use under AEC license in non-Commission research projects. •A national survey of projected 1950 purchases of new machine tools, machine tool accessories, materials handling equipment, etc., just completed by the American Society of Tool Engineers reveals that, of the companies reporting, 80 pct state that they plan to buy either more equipment or the same amount as in 1948. • Armour Research Foundation is conducting investigations for the use of clay and shale deposits to make lightweight aggregates. The material is heated until it expands and forms material suitable for mixing with cement which it is hoped will be lighter, stronger, have better insulating qualities and will lower the cost of concrete. •In the first six months of 1949 the bituminous coal miners' average hourly earnings were $1.94 -as compared with X1.392_ national average for all manufacturing. Average annual earnings of full-time employees in the bituminous coal mines in 1948 were $3387 as compared with $2809 for all industry. •LaSalle Business Bulletin reports: "year ends on a rising trend in industry and trade ... nearly record-breaking demand from almost all sources keeps business high... most indicators but little below postwar peak... forces keeping activity high arestill powerful--changes in general business conditions likely to be slow and moderate." •Office of Internal Trade of the Commerce Department requests that technical data significant to the national security which is to be sent outside of the United States be submitted to it for an official opinion on the desirability of transmitting such information. This voluntary compliance program is part of our national security control. • Blast furnace slag reduced to 12 to 16 mesh is being used for sanding track at the Mont Coal mines of Armco. The slag replaces silica sand which caused silicosis. It has proved so effective and cheap that tests are being made to use the slag for rock dusting.

Jan 1, 1950

By William Bogan, Mark Vaivoda, Richard Daniele

Many factors must be considered when performing engineering and construction work for a major minerals project. Dravo's Afton copper smelter in British Columbia illustrates some of the E&C factors considered when setting up this new operation. In March 1978, Afton Mines Ltd., a Tech Corp. subsidiary, began blister copper production at the world's first integrated copper ore mining, milling, and smelting operation to use Top Blow Rotary Converter (TBRC) process smelting technology. This key TBRC smelting element is licensed by INCO Ltd. to Dravo Corp. The TBRC process uses a single vessel of modular design. It rotates for mixing and provides complete processing capability, from concentrate through blister copper. The Afton facility is about 16 km west of Kamloops, a town in south-central British Columbia. To make its operation as economic as possible, Afton officials considered several options for the copper smelter, the first in modern times in the province. Inability to extract precious metals-primarily gold-from the concentrates ruled out hydro-metallurgical processes. The final choice was between a conventional electric furnace/ Peirce-Smith converter combination and the TBRC process. The TBRC process was chosen for its versatility in processing the various Afton concentrates and grades and its 40% lower capital cost compared to the electric furnace converter system. The TBRC smelter -including concentrate slurry receiving, drying, storage, smelting, off-gas cleaning, and copper casting-had an installed cost of about $25 million. In December 1974, a pilot program was conducted by Teck, Dravo, and INCO at INCO's Port Colborne, Ontario, research facility. The pilot program demonstrated the TBRC's ability to smelt, convert, and clean copper slags. After the successful pilot effort, Dravo performed additional research to find an effective fixation system for high grade, intermittent SO2 gases. Once the go-ahead was given, design and procurement for the Afton copper smelter was provided by the Denver Division, Dravo Engineers and Constructors. Commonwealth Construction, Vancouver, constructed all Afton facilities. Afton's single furnace smelter is designed to produce 25-kt/a blister copper in 363-408 kg cake form. The product is sold to England for electrolytic refining. The TBRC process is only one of several innovations proposed by Dravo and chosen by Afton to insure the most modern smelter in North America and meet all British Columbia's environmental restrictions. Conventional smelting methods use a separate furnace for each process step. The TBRC process employs but one furnace. The Afton TBRC vessel measures 6.4 m in length and 4.3 m in diameter. The furnace is supported on a set of motor-driven rollers. These permit the vessel to rotate at variable speeds to 40 rpm. Rotation provides good mixing, high reaction rates, and effective heat transfer from the refractory sides to the molten bath resulting in a low thermal gradient. The furnace can tilt through a full 360° for charging, firing, and pouring. Smelting at Afton is accomplished in sequential fashion. Flotation concentrate and limestone flux are initially charged to the hot, empty vessel. Using the water-cooled, oxy-fuel lance, the initial charge is smelted. Once sufficient molten bath is obtained and slagging completed, the metallic concentrate is charged. Materials are charged through the water-cooled, variable position additive chute mounted on the TBRC

Jan 10, 1980

By Kenneth A. Gutschick, Robert S. Boynton

Lime has become a general and loosely used term to denote almost any kind of calcareous material or finely divided form of limestone or dolomite, as well as burned forms of lime. However, according to Webster, lime is only calcined limestone (known as quicklime, unslaked lime, or calcium oxide). It also embraces the secondary product of quicklime, i.e., hydrated lime or slaked lime (calcium hydroxide). There are two basic types of limestone used for lime manufacture-high calcium and high magnesium (dolomitic). The dolomitic quicklimes and hydrated limes correspond to their "high calcium" counterparts. The only difference is that the dolomitic types are a combination of the elements calcium and magnesium, in varying percents, whereas high calicum limes contain less than 5% MgO down to 1/2%. In either case a pure form of limestone of at least 97% combined carbonate content is needed to make salable lime, barring a few exceptions. The calcination of both types is diagrammed chemically as follows: [ ] In the foregoing reversible reactions the limestone is burned (calcined) in lime kilns, with the carbon dioxide content of the stone expelled as a gas. The weight loss during calcination of pure high calcium limestone is 44%; with equimolecular dolomitic limestone, the weight loss is 48%. Since lime has a strong affinity for CO_, particularly if moisture is present, it will readily revert to its original carbonate form. This occurs when quicklime "air-slakes" and adsorbs CO.. from the air. Thus, quicklime is perishable and should be stored in dry, water-tight areas. Depending upon the type of kiln used and the physical structure of the stone, the size of the quicklime may range from sandlike granules to 8 in. lumps. However, pebble sizes ranging from 1/4 in. to 2 in. are the most common. Screened quicklime fines are also com¬pressed (pelletized) into 1 in. pellets. For some purposes ground or pulverized forms of quicklime are used, ranging from No. 10 mesh to dust. Generally a pebble of quicklime is about the same size as the pebble of limestone before calcination (perhaps shrinking slightly). A more stable form of lime is hydrated lime. This is obtained by adding water to quicklime, slaking it into a dry, fine, subsieve size white powder. Because its affinity for moisture has been satisfied, it is not vulnerable to further moisture like quicklime. However, it has the same strong affinity for CO_. The following reversible chemical reactions illustrate how hydrated lime when heated (or dehydrated) can revert to the original oxide form:

Jan 1, 1975

By J. R. Long, E. T. Hayes, D. C. Root, R. S. Dean

The U. S. Bureau of Mines has recently reported on the development of a process for preparing pure ductile titanium in substantial quantities1 and on the physical properties that may be attained in the metal, when consolidated by powder metallurgy methods and fabricated by certain hot and cold-working procedures.2 The high physical properties (Table I), combined with excellent corrosion resistance and light weight, will lead no doubt to appropriatc applications of the metal. In any application, methods of joining will be of considerable importance. The relatively high activity of the metal toward the common gases raises the question of weldability and conditions that might be required for successful welding. Since hydrogen, oxygen, and nitrogen embrittle the metal, it should be protected from these gases at elevated temperatures. This was demonstrated by a few preliminary trials of arc, gas, and resistance welding. In these trials only the resistance method proved to be immediately- applicable. While atomic: hydrogen welding of titanium may be successful in some instances, a considerable amount of development work will be required to prove its worth. In addition, it would be suited only to small assemblies that could be heated subsequently in a high vacuum to remove embrittling hydrogen. Heli-are methods likewise would be limited to small assemblies, which could be completely protected by a helium atmosphere. It was quite apparent that titanium required more protection than was afforded by the normal flow of helium gas used for welding magnesium and aluminum. The hot metal is attacked by oxygen and nitrogen, and the rapid diffusion of the oxide into the metal prevents the formation of a protective coating and requires the helium atmosphere to be maintained until the weld has cooled nearly to room temperature. The preliminary work indicated that titanium could be successfully spot-welded without deterioration of the metal and that the microstructures of the welds were normal, exhibiting good bonding, and no oxidation. The high resistivity of titanium (53 microhms per cu. cm.) suggested that it would behave somewhat like stainless steel and allow considerable latitude in the several welding variables. The results reported here are intended to give a general picture of the effects of varying welding current, welding time, and tip pressure on single spot welds made on several different thicknesses of titanium sheet. The work was undertaken to demonstrate the feasibility of welding titanium rather than as an exhaustive study of spot welding. There are, therefore, a number of factors that will require further investigation to establish the specific controls required for actual applications.

Jan 1, 1947

By D. K. Crampton, H. I. Burghoff, J. T. Stacy

The effect of cold-working upon electrical conductivity of copper and of copper alloys appears not to be generally known in detail. Although several papers on the subject have been presented, showing variable effects according to alloy composition, it is often assumed that the 2 to 3 per cent lowering of the conductivity of ordinary tough-pitch copper by severe cold-working is typical for copper alloys. Because of this situation it was decided to carry out the present work upon several types of copper, copper-zinc alloys over the commercial range of brasses, other binary alloys, and numerous age-hardening alloys in the quenched, and quenched and aged conditions. The large number of alloys investigated made it impossible to study every one in the detail it may have merited. Inasmuch as several interesting points that could not be satisfactorily explained came to light, further work is contemplated by the authors. It is usually considered that the normal effect of cold-work on ductile metals and unordered alloys is to decrease conductivity slightly. In alloys that are in the ordered state, as annealed or otherwise heat-treated, cold--working tends to disorder the structure, resulting in very marked lowering of conductivity. The random state of atomic arrangement produces lower con- ductivity than the ordered state for the same composition.1 Previous Work Previous work in the authors' laboratory has shown the electrical conductivity of several copper alloys to be decreased by greater amounts than might have been expected, in view of the general knowledge on the subject, when cold-worked. Guillet and Ballay2 investigated the influence of cold-work upon the resistivity of several metals and alloys, including copper and some copper alloys. The increase of resistivity due to severe working w is less than 4 per cent for all pure metals tested, while the increases for the alloys were generally higher. In the copper-zinc alloys, they found that the increase of resistance due to drawing increased with zinc content, and reported a 21.7 per cent increase of resistance for an alloy contaiiiing 67.9 per cent Cu as severely worked. Masima and Sachs3 studied the change in electrical resistance of three brass crystals when stretched in the tensile test, obtaining increases in resistance of the order of 3 per cent for 30 to 40 per cent reduction of area of the specimens. The resistance decreased again when the cold-worked crystals were subsequently annealed. Bardenheuer and Schmidt4 found that the conductivity of copper was decreased by 3 to 4 per cent when reduced 50 per cent by working. The conductivity of 72-28

Jan 1, 1941

By Michael B. Bever, Carl F. Floe

he possibility that carbon may be soluble in copper to a limited extent has bten recognized for over a century. The quantitative investigation of this problem, however, requires more sensitive techniques than have formerly been available. Three recent developments have made possible more accurate determinations: the vacuum-fusion method of analysis, the production of copper of high purity and the availability of high-purity refractories, particularly graphite. In addition to its obvious theoretical interest, the problem of carbon solubility in copper is of practical importance. In the production of copper and of high-copper alloys, carbonaceous covers are freauerltlv used. If even minute amounts of carbon are dissolved, insoluble carbon oxide gases will be formed when such metals are poured under oxidizing conditions. A mechanism of this kind could well be one of the principal causes of gas porosity in casting copper-base products. Review of Literature In 1823 Vivian1 raised the question as to whether copper by overpoling becomes "combined with a minute portion of carbon." Karsten2 asserted, in 1832, that carbon reduces the high-temperature strength of pure copper, so that when the carbon content has reached 0.2 per cent the metal will be brittle at a dark red heat. According to Karsten, carbon contents of 0.05 per cent make it difficult to hot-work copper. He also reported that the specific gravity of copper is 8.8969 and that it increases to 8.9258 if the copper is cemented with carbon and then melted. He emphasized the difficulty of determining analytically the small amounts of carbon present in copper. The metal was removed by wet methods and the residue considered as carbon. At Percy's request, Dick,3 in 1856, carried out various working tests on copper that had been ill prolonged contact with carbon, and found that the working properties of the metal had not been affected. He also attempted to determine the presence of carbon analytically. In one experiment the copper was dissolved and the residue was fused with litharge, and in another essentially a combustion analysis was made on a copper sample. In a final experiment, a sample was dissolved and the residue subsequently subjected to a combustion analysis. Indications of as much as 0.005 per cent carbon were found, but Dick considered his work inconclusive largely because of the possible interference of sulphur. Percy4 concluded, from Dick's experiments and from some experimental work of his own, that the solubility of carbon in copper had not been established with

Jan 1, 1946

The investment involved in any communication system represents a considerable sum. Even though it is desirable that the system work properly each and every time it is called into use, some failures are bound to occur. Most failures, however, and especially those that occur most frequently, are due to poor installation techniques. An extra hour spent at an installation site can save many maintenance trips and many frustrating hours of system troubleshooting. Typical faults likely to cause communication outrage are Pager phone systems Poor splices aggravated by corrosion. Strain relief not provided. Drip loop not provided. Incorrect branch connections. Overloading the circuit. Poor battery connections. Improper wire size or type. Lightning strikes. Improper placement of wire runs. Carrier phones Mounting transceiver near load resistors or other sources of heat. Tracks not electrically bonded. Cable abrasion due to poor mounting location. Disconnected battery. Poor mechanical installation. Each installation should be well planned. After an installation is completed, the technician should ask the question, "What can go wrong with this unit or line?" Remember the adage, "Whatever can go wrong, will." Preventive measures taken during installation will pay off in the long run. 6.2 Pager Phone Installation The pager phones used in many underground coal mines are battery-operated, party-line telephones with provisions for loudspeaker paging. The system is usually two-wire, nonpolarized, and operated by self-contained batteries. Many of the individual units are certified as permissible. 6.2.1 Mounting Pager phones are designed to be mounted on an upright support at the desired location. For convenience, the phone should be mounted 5 feet above the floor where there is no obstruction to using the handset or removing the cabinet front cover for servicing or battery replacement. In low-coal situations, a suitable height for installation should be selected convenient to the normal operator's position at the site selected. About 12 inches of free space on each side of the phone should be provided for cabinet access. The phone should be protected against direct exposure to dripping water and should not be allowed to rest in a puddle of water. The mounting location should be convenient to a work location and have a safe, unobstructed area for a worker to stand and use the phone. The phone must be in a location where the worker will not be in the path of moving vehicles or falling debris. Each telephone is normally well insulated, but it is still good practice to provide an insulating mat or dry planking for the user to stand on.

Jan 1, 1984

By P. J. Soltis

Direct as well as indirect evidence of a-phase ordering was found in a "near-a" type titanium alloy, Ti-8Al-1Mo-1V. The annealed alloy showed an anomalous decrease in second-stage creep rate at 950°F (510°C) and 47,500 psi. Anomalous increases were noted in initial yield stress after 500 hr creep exposure and in tensile strength after 1100 hr creep exposure. Debye-Scherrer X-ray diffraction patterns obtained on fine-grained polycrystalline speci-ment showed much line broadening and development of superlattice lines after 500 hr at 510° C. Examination with the light and electron microscopes failed to reveal phase changes in thermally exposed material, but detailed metallography is presented illustrating the plastic and fracture characteristics of the alloy. Electron-metallographic evidence is presented, however, which shows the nature of the nucleation and growth of ordered regions from the disordered a in annealed material. In the original phase diagram of the binary Ti-Al system constructed by Ogden et al.1 aluminum was shown to be soluble in a titanium over a wide temperature range at concentrations up to about 30 pct. Subsequently, a number of papers2-7 have appeared which indicate the existence of either intermetallic compounds and/or ordered phases in the a field up to 25 pct Al. In the most recent of these, Goldak and Gordon paw7 have determined unequivocally the ordered hexagonal D019 structure for Ti3Al in a 25 pct Al alloy. No superlattice lines were observed above 1112°F (600°C). Previously, the embrittle-ment encountered by Crossley and Carew4 in low- temperature heat treatments of binary Ti-Al alloys low in aluminum had been attributed to the appearance of a new phase in light micrographs. In the present work, direct as well as indirect evidence is presented showing the existence of a-phase ordering in what is essentially the binary Ti-8A1 alloy containing small percentages of the ß stabilizers molybdenum and vanadium, i.e., the "near-a" Ti-8Al-1Mo-1V alloy. Although Bohanek and Kessler8 have shown that this alloy has good stability at temperatures up to 1100°F (593°C), the present work shows instability at 950°F (510°C) where long exposure times were used. Light and electron microscopy proved very useful in revealing the mechanical behavior of ordered a and led to the conviction that ordered "near-a" alloys may have remarkably good properties and useful engineering applications.

Jan 1, 1965

By Robert Adams

Secondary or scrap materials appear at all stages in the industrial process and in a bewildering variety of forms, grades, and values. It is useful to begin analyzing them by dividing the broad concept of "Secondary Supply" into three parts First, the concept must encompass the stock, or pool, of secondary materials. In the process of satisfying his wants, man produces desired products from the materials and natural resources found around him. As long as the rate of production is greater than the rate of obsolescence of a given product, the total stock or pool of materials embodied in that product will increase in size This stock concept relating to secondary materials is directly analogous to the "resource" concept used for primary raw materials in the preceding chapter, and includes all materials embodied in existing products (Obviously, this excludes those materials which are destroyed in the consumption process, viz , fuel oil burned to provide heat.) Consumption of a primary material in a productive process tends to reduce the resource base of that primary material In direct contrast, however, the production or use of products increases the resource base of the secondary material. Thus, we find that a country which has no resource of a primary material can, by importing products that contain the material, build up a large enough stock to provide a basis for secondary recovery. The estimated growth of the pool of copper in use in the United States through 1967 is shown in Table 5.B.1.a The estimate of 39 3 million tons at the end of 1967 includes only technologically recoverable copper and is, therefore, somewhat less than the stock concept described previously, which does not distinguish between recoverable and unrecoverable material. Nevertheless, Table 5 B.1 does give an idea of how a nation's secondary resource of a material can grow over the years. A second aspect of the concept of secondary supply is the generation of secondary materials. This includes materials generated as scrap in production as well as the movement of a material out of the stock of existing products via wear, damage, or obsolescence The quantity of materials generated is usually either nearly or completely independent of the technologic capabilities and economic forces which prevail in the secondary recovery market.b The justifications for and the qualifications to this statement are considered later. The final aspect of the concept of secondary supply consists in the secondary recovery process It is at this point that the technologic and economic forces of the secondary recovery market become the controlling fac-

Jan 1, 1976

By J. R. Long, R. S. Dean, D. C. Root, E. T. Hayes

The U. S. Bureau of Mines has recently reported on the development of a process for preparing pure ductile titanium in substantial quantities1 and on the physical properties that may be attained in the metal, when consolidated by powder metallurgy methods and fabricated by certain hot and cold-working procedures.2 The high physical properties (Table I), combined with excellent corrosion resistance and light weight, will lead no doubt to appropriatc applications of the metal. In any application, methods of joining will be of considerable importance. The relatively high activity of the metal toward the common gases raises the question of weldability and conditions that might be required for successful welding. Since hydrogen, oxygen, and nitrogen embrittle the metal, it should be protected from these gases at elevated temperatures. This was demonstrated by a few preliminary trials of arc, gas, and resistance welding. In these trials only the resistance method proved to be immediately- applicable. While atomic: hydrogen welding of titanium may be successful in some instances, a considerable amount of development work will be required to prove its worth. In addition, it would be suited only to small assemblies that could be heated subsequently in a high vacuum to remove embrittling hydrogen. Heli-are methods likewise would be limited to small assemblies, which could be completely protected by a helium atmosphere. It was quite apparent that titanium required more protection than was afforded by the normal flow of helium gas used for welding magnesium and aluminum. The hot metal is attacked by oxygen and nitrogen, and the rapid diffusion of the oxide into the metal prevents the formation of a protective coating and requires the helium atmosphere to be maintained until the weld has cooled nearly to room temperature. The preliminary work indicated that titanium could be successfully spot-welded without deterioration of the metal and that the microstructures of the welds were normal, exhibiting good bonding, and no oxidation. The high resistivity of titanium (53 microhms per cu. cm.) suggested that it would behave somewhat like stainless steel and allow considerable latitude in the several welding variables. The results reported here are intended to give a general picture of the effects of varying welding current, welding time, and tip pressure on single spot welds made on several different thicknesses of titanium sheet. The work was undertaken to demonstrate the feasibility of welding titanium rather than as an exhaustive study of spot welding. There are, therefore, a number of factors that will require further investigation to establish the specific controls required for actual applications.

Jan 1, 1947

By Duane B. Jorgensen

The two calcium sulfate minerals, gypsum and anhydrite, occur in many parts of the world, and gypsum has long been of economic importance in the family of industrial minerals. Gypsum, the dihydrate form of calcium sulfate (CaSO, . 2H20) and anhydrite, the anhydrous form (CaSO,) are frequently found in close association, and it is seldom that a calcium sulfate deposit will consist exclusively of one mineral or the other. Although known gypsum deposits are extensive, anhydrite makes up the larger part of total calcium sulfate resources. Although it has very minor economic use, it is important to the understanding of gypsum deposits and is referred to frequently in the following discussion. Calcium sulfate is one of the principal constituents of evaporite deposits, and when pure, has the following composition: [ ] Deposits of pure gypsum or of pure anhydrite which are large enough to be considered commercial have not yet been found because of both the metastable relationship between the two minerals, and the presence of impurities such as calcium or magnesium carbonates, chlorides, other sulfate minerals, clay minerals, or silica. Most gypsum produced ranges from 80 to 95% pure and beneficiation is normally limited to selective mining or quarrying or upgrading by crushing and screening during mill processing. END USES The largest use for gypsum is based upon the unique property which calcium sulfate has of readily giving up, or taking on, water of crystallization. With the application of a moderate amount of heat in a process known as calcining, gypsum is converted to plaster of paris, the hemihydrate of calcium sulfate (CaSO4 ½ H2O), which when mixed with water will set or harden as the calcium sulfate returns to the stable dihydrate form. This semifinished product, usually called stucco, is then manufactured into a large variety of plasters, wallboard, and block for construction use, or into plasters for industrial applications. About 75% of the gypsum used in the United States is calcined for these purposes. Uses of uncalcined gypsum are principally as a retarder for portland cement, as a soil conditioner, as a mineral filler, and other minor industrial applications. About 25% of the gypsum mined in the United States goes into these markets; however, in other countries with building practices different from those in the United States and Canada, relative usage varies widely. Calcium sulfate deposits are the world's largest sulfur resources; minor quantities of gypsum and anhydrite have been used to produce sulfur or sulfur compounds. This use is accompanied by a unique site-specific set of economics because sulfur is generally available from non-gypsum sources at lower cost.

Jan 1, 1994

By John D. Sullivan, Edwin J. Rogers, Chester R. Austin

THE problem of making a building unit combining the necessary physical and mechanical properties and good thermal insulation has been foremost in the minds of architects and ceramic and construction engineers for many years. This paper presents the results of studies on thermally expanding shales or clays to produce light-weight cellular products suitable for making building units. An expanded clay block suitable for building purposes should be large enough so that substantial savings may be effected in labor costs in laying the wall. The permeability should be low and it should have sufficiently good "dry-wall" characteristics to permit exposing the exterior surface to the elements, and to permit plastering directly the inside wall surface. The thermal conductivity should be low and the mechanical properties should be adequate. Obviously, a unit possessing satisfactory qualities for constructing an outside wall would be satisfactory for interior walls and for back-up purposes. The results of studies on bloating various shales or clays[t] and the properties of the expanded products are reported. In another paper1 basic factors involved in bloating of clays are discussed. Manufacturers of ceramic products, particularly structural clay, may encounter bloating of the ware during burning, and precautions must be followed to avoid this phenomenon. About 1927 the C. F. Burgess Laboratories, Madison, Wis., while carrying on an investigation for the American Face Brick Research Corporation, conceived the idea of intentionally bloating clay while holding it in a restrained condition, with the hope of producing a unitary cellular mass. Work was carried on until about 1931, when studies were terminated because of business conditions. These studies were continued later by The Western Brick Co., Danville, Ill., which developed a process of "inwardly expansive bloating."2 The major purpose of the latter investigation was to produce back-up tile to compete with concrete blocks made from Haydite or cinder aggregate. Haydite is a light-weight aggregate formed by heating certain clays or shales rapidly in a rotary kiln. While the investigations at the C. F. Burgess Laboratories or at Western Brick Co. were not carried far enough to lead to the commercial production of material for the construction of walls, particularly outside walls, they showed that certain clays could be thermally expanded and that it was possible to produce a material of low permeability with a large percentage of the total voids or cells closed. Commencing in 1939, the Ozark Chemical Co. sponsored a research program at Battelle Memorial Institute for the purpose of determining whether it is technically feasible to make thermally expanded building units, and specifically to get answers to the following questions:

Jan 1, 1942

By L. D. Jaffe, J. H. Hollomon

THE effect of tempering temperature and time upon the properties of quenched steel is clearly a subject of great practical importance, as well as of considerable theoretical interest. It would be very desirable to be able to predict the properties of a quenched steel when given any selected tempering cycle, with a minimum of experimental work upon that heat or even type of steel. Two problems are involved: one consists of relating the structure obtained to the physical properties, and will not be discussed here; the other, with which this paper deals, involves the relations of time, temperature and composition with the structure obtained on tempering. Indentation hardness is perhaps the most convenient quantitative measure of the tempered structure, or of what might be called the "degree of tempering." Undoubtedly, it is not an exact measure, and in some cases (as when temper-brittleness occurs) pieces of the same quenched and tempered steel may have widely differing properties at the same hardness. However, hardness has the advantage of being simple to determine and is certainly the most widely used indication of the degree of tempering. Moreover, for fully quenched steels that are not temper-brittle and do not contain retained austenite when quenched, it appears that, in general, if the hardness of the steel is the same, the tensile and impact properties will also be identical, whether a high or a low tempering temperature is used. The tempering charts available in the metallurgical literature usually give the hardness as a function of tempering temperature for only one tempering time. However, in practice, tempering times frequently vary, and a method of converting tempering curves for one time to tempering curves for some other time would be very valuable. It is also advantageous, in determining the tempering treatment necessary for a given part, not to have to temper samples at several temperatures for the time used for the commercial tempering operation. A more satisfactory procedure would be to employ times of the order of 10 to 30 min., rather than 5 or 10 hr., and if possible to use only one temperature. Furthermore, it is frequently desirable, for reasons such as temper-brittleness,* to obtain a given hardness with short times at relatively high temperatures, and it would be convenient to be able to compute without tests the time required to produce this hardness. Remarkably few quantitative studies of the hardness of quenched steel tempered over wide ranges of temperature and time

Jan 1, 1945