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By Gieskieng, D. H.

Published tables of jaw crusher capacities are compiled for the most part from field performance data, interspersed with interpolations, extrapolations, various safety factors, and other modifications. Such a table attempts to balance and equalize field data from widely different materials, with differences of crushability, efficiency of feeding, sizing of the feed, and so on. The tests described in this paper were undertaken with the objectives of checking previously reported capacities; of studying the effects of various factors upon the capacity, including jaw plate curvature; and, if possible, of deriving a general capacity equation. Such an equation has been derived from the data obtained in these tests. It is given together with factors for its use. While more accuracy than is usually required may be obtained by careful application of the equation, it is of simple form and provides a convenient reference plane upon which the potential capacity of various crushers may be compared, and with which operating adjustments may be made on existing installations. The principal deviation in these tests from the usual approach consists of a laboratory technique which has been developed for the production of selected

Jan 1, 1949

By M. R. Geer, H. F. Yancey, P. S. Jacobsen

Two growing problems confront the preparation engineer—still further restrictions on stream pollution and a greater proportion of fine coal as more and more continuous miners come into use. The de-watering screens, centrifuges, and settling ponds that sufficed a few years ago must often be supplemented by more effective equipment, and in some instances the finest solids are now being recovered by vacuum filtration, once considered too costly in many coal washeries. Unfortunately not all slurries can be readily filtered. Some are virtually unfilter-able, and others do not permit the high cake rates needed to hold costs within reason. Often, however, these difficult slurries can be rendered filterable by flocculation. Starch and lime have long increased settling rate in thickeners and can also aid filtration. More recently there have been other flocculants, primarily synthetic polymers or gums. Reports of their great effectiveness prompted the U. S. Bureau of Mines to test their use in filtration as part of its program on recovering and cleaning fine coal. The object of the present work was to compare some of the newer flocculants with starch and lime and to test the reaction of different types of slurries to flocculation. Three natural slurries, three synthetic coal-clay mixtures, and five flocculants were tested, all with a laboratory filter leaf. Slurries and Flocculants Tested: First of the slurries was the thickener feed from the washed coal section of the Michel colliery of Crow's Nest Pass Co. Ltd., Michel, B.C. As shown by the screen and ash analyses in Table I, practically all this slurry was finer than 28 mesh, and about half the solids were finer than 200. Substantially all material coarser than 200 mesh was clean coal, but the ash content of 20.7 pct in the finest size indicates a moderate amount of impurity. This coal is medium-volatile bituminous in rank. Slurry was also obtained from the Black Diamond washery of Palmer Coking Coal Co., King County, Wash. This underflow of a 1/2-mm vibrating slurry screen is a waste product discharged to a settling pond. As shown by the data in Table I it contained about 20 pct material finer than 200 mesh, which analyzed 77.5 pct ash, indicating a high proportion of clay. The coarser sizes were also high in ash content because of the presence of bone and shale. Black Diamond coal is on the dividing line between bituminous and subbituminous rank. The third slurry, from the washery of Roslyn-Cascade Coal Co. in Kittitas County, Wash., was the underflow of a battery of 8-in. cyclones that is wasted with the coarser refuse from the plant. In both size and ash content this slurry was similar to the Black Diamond, but since it was a cyclone-underflow product, the fraction finer than 200 mesh undoubtedly contained a much smaller proportion of finely divided clay than was present in the Black Diamond slurry. The Roslyn-Cascade coal is high-volatile A bituminous in rank. Initially the slurry samples were stored in the laboratory at a concentration of 40 pct solids. A progressive change in filtration and flocculation characteristics during storage was noted, however, presumably because of progressive disintegration of the clay. After careful testing demonstrated that the slurry solids could be dried and then repulped without changing the original filtration characteristics, this procedure was adopted. The flocculants used were Separan 2610, Kylo 27, Jaguar MD-A, Idaho potato starch, and lime. The lime was used as a slurry, the Separan 2610 as a 0.10 pct aqueous solution, and the other flocculants as 0.50 pct aqueous solutions. The starch was causti-cized with sodium hydroxide before use. As some of the flocculants are reported to deteriorate on storage, new batches of flocculants were prepared every two days. Test Procedure: Fig. 1 diagrams the filter leaf apparatus employed. This consists of a test leaf having an effective area of 0.10 sq ft., a 60°, 8 1/2-in. diam cone to hold the slurry sample, a variable-speed electric stirrer, vacuum gage, bleed line for controlling vacuum, filtrate flask, moisture trap, and vacuum pump. Two filter cloths were selected—Saran SA 603, a monofilament, coarse-weave cloth, and polyethylene PO-801 HF, a monofilament, fine-weave cloth. The Saran was selected to provide maximum cake rate without regard to clarity of filtrate and the polyethylene to provide the best quality of filtrate without regard to cake rate. The test charge for the filtering vessel consisted of 800 g of solids (previously soaked for 24 hr) and

Jan 1, 1960

By R. G. Bowman

DISCUSSIONS of processes for the manufacture of white lead generally open with the statement that white lead is the oldest chemical pigment known to man. This fact is of more than historical interest; in the light of the present extensive use of white lead, ii indicates that the .compound possesses characteristics that make it unique among white pigments, and superior to all ;in its particular field. A greater variety of processes have been proposed for manufacturing white lead than for any other one chemical compound. Only a few of these processes have come into commercial use, however, and a large part of the present production here and abroad is made by the process used in ancient times. The outstanding disadvantages of the old process are that it is slow and laborious, affords no control of the product, and yields at best an impure material lacking in uniformity. Improved processes, sometimes classed all together as "quick processes," have had as their main object the shortening of the time required. Most of them accomplish this and some have yielded a superior product as well, but only two or three are now in use commercially. For centuries the manufacture and mixing of paints has been treated as an art, and the practice has been much influenced by tradition and precedent. There is a reluctance to abandon old materials for this purpose, and as few new uses for white lead have been developed, the adoption of the quick processes has been slow. The electrolytic production of white lead is not-new, a large number of processes and forms of apparatus have been proposed and patented within the past 25 years, all directed toward the, production of white lead, wholly or in part, by electrolysis. One or two of these processes were tried commercially but proved unsuccessful.

Jan 9, 1925

By John Gann

THE following investigation constitutes a brief resume of the more important binary magnesium alloys from the standpoint of metallographic technique, and the effect of heat treatment on structure and properties. The comparative newness of the subject justifies this procedure as a preface to a more detailed study of each individual series of alloys. The work was started with the idea of practical application in the industry rather than as a theoretical investigation. The alloy compositions studied were selected as those most likely to show whether heat treatment would produce beneficial results. Furthermore, it was considered satisfactory to use commercial 99.9 per cent. magnesium, the best commercial grade of alloying ingredients, and to limit the time of heat treatment at the expense of incomplete equilibrium. These facts must be kept in mind when examining the results obtained, and the conclusions drawn.

Jan 1, 1928

By S. S. Clarke

LATE in 1942, the increasing demand for zinc, coupled with the growing shortage of miners and the knowledge that some abandoned mines would have to be reopened for prospecting and development, led to considerable thought as to the possibilities of further mechanization in order to conserve man power. The ore bodies, locally termed "sheet ground," are an important ore bed in some mines and are in the lower part of Boone formation of the Mississippian Series. Some mines contain interbedded layers of nearly pure galena and sphalerite in horizontal sheets ranging in thickness from a thin seam to several inches and is persistent over large areas. This type of ore body offered the best opportunity for study and experiments. The use of jumbo drill carriers was advanced but some doubt was expressed as to the adaptability of jumbos as then in use to mine headings as compared to post and arm mounting (Fig I). Another consideration was the introduction of truck haulage when several mines were trackless. A drill frame, built to carry 2 4-in. drifters, was mounted on a truck chassis. This design proved a failure as it was not rigid and the resiliency of the tires and springs allowed too much play. Long screw jacks were then used to hold the truck firmly in place, but placing the jacks and securing the truck required more effort and time than setting up post drills, so the truck carrier was abandoned. The use of a bull dozer underground had been under consideration for some time to be used in "brunoing" the broken dirt from behind pillars and other inaccessable places so the slusher drags could load without double dragging the dirt. A dozer with hydraulic blade lift was purchased and R. I. Tuthill, Superintendent of Section 30 Mines, suggested that a long drill arm be substituted for the blade, and the drills mounted on the cross member. The hydraulic lift would permit drilling holes at any required spacing. The "cat" was very mobile and answered the problem of a trackless mine. The initial tests showed that the "cat" would make a good carrier, but the hydraulic controls Were not positive enough to keep the drills in alignment while drilling. The next step was to build a small hoist. This hoist was attached to the power take-off on the "cat" and by means of sheaves and a double line of 3/8-in. hoist cable, a positive control for raising and lowering the boom was obtained. To avoid serious injuries to the drillers should the cable break, a safety chain was fastened to the drill boom and hooked into a slot in the back of the "cat" frame. A different power unit was obtained for the "cat," as a state law prohibited the use of internal combustion engines in mines. A custom machine shop had just placed on the market a small hoist powered by a Model A Ford engine that had been very ingeniously converted to a slide valve engine using compressed air. To use this unit on a "cat," our master mechanic de-

Jan 1, 1947

By D. Harker, M. J. Murphy

The mechanism by which age-hardening takes .place is still not completely understood. The principal theories range from the extreme of "precipitaiion-hardening" to that of "order-hardening," with many intermediate gradations. In the hope of obtaining new data on which to base a choice among the many theories, the authors have made electron micrographs of formvar replicas taken from metallic specimens at various stages of age-hardening. The results so obtained on an alloy of 2 per cent beryllium in copper and one of 20 per cent molybdenum in iron will be described in the following pages, as well as the technique used in preparing the replicas. Preparation of Formvae. Replicas of Metallic Specimens This section is concerned with the techniques that have roved successful in preparing formvar replicas for studying the microstructure of metals with the electron microscope. Because of its simplicity and accuracy, the formvar replica1 method developed in the General Electric Research Laboratory has been used exclusively, since it is much simpler than the silica replica method of Heidenreich and Peck2 and produces as good results. The formvar method to be described requires a technique acquired only by practice, and no foolproof set of rules can be given. it is a rapid method and a replica can be obtained in less than five minutes under favorable conditions. This does not mean that perfect replicas can be produced every five minutes, but rather that one can well afford to take several strippings* in order to produce a replica of high quality. The metallographic technique required for replica work—very fine polishing and etching with very dilute solutions—is described here. It can be said, in general, that almost any surface that has been carefully prepared for a photomicrograph at 1000 or more diameters can be used to obtain a replica for the electron microscope. Preparation of Metallographic Specimens The preparation of the metallographic specimens is somewhat more exacting than that usually given to samples to be used for inspection under the light microscope. After much experimentation, it was concluded that the best method consists in polishing the metal through to the coarse cloth, then etching and repolishing on final cloth until the layer of distorted metal is removed. After this procedure has been completed, a dilute etch—to approximately the depth necessary for a micrograph at 1000 diameters—usually produces a sur-

Jan 1, 1945

By George J. Clark

One of the major problems of operation in the anthracite industry is the disposal and handling of refuse—not because of its complexity but because of the quantity and type of material involved. It is the purpose of this paper to describe the kinds of refuse, methods of disposal, quantities of material to be handled and equipment used, together with present day application at specific operations in the Northern, Eastern Middle, Western Middle and Southern anthracite fields. For the purpose of this paper, refuse is considered to be any material that has no present or foreseeable future value and that must be handled and disposed of in the process of mining and preparing anthracite for market. Included in this classification are tunnel rock, mine rock, cleaner plant refuse, breaker refuse, old timber, ashes and silt. Disposal Methods Old timber is disposed of either by burning or by depositing on the refuse bank. Burning is preferred because timber on the refuse bank is a potential fire hazard. Ashes are deposited on a separate bank, mixed with other refuse, or flushed into old mine workings. In many places, the latter practice has caused considerable difficulty in preparation of coal mined from these areas. In depositing ashes on the surface, it is wise to refrain from mixing them with material containing coal as such contamination may prevent reclamation of the coal in future years. Tunnel work, mine rock, cleaner plant and breaker refuse compose the bulk of the material to be disposed of and handled, and are referred to collectively as "refuse" in this paper. Waste material in or adjacent to the coal beds may be removed at the working face wherever possible. This can be done in flat or lightly pitching beds, and in the Northern field represents a sizable percentage of this type of refuse handled. In the other three coal fields, this method of disposal cannot often be used. Refuse not removed at the working face is taken to the surface and generally is deposited on banks; occasionally it is crushed and flushed into old mine workings. Breaker refuse often is used for constructing berms for silt-retention basins. Disposal Problems The problem of handling refuse is different for each operation, owing to topographical conditions, quantity of material to be handled, anticipated requirements and types of equipment in use elsewhere at the operation. Preparation plants with limited refuse-disposal areas, excessive grades to reach the required elevation and long hauls to disposal areas not readily accessible require the selection of equipment to best meet the conditions. The quantity of refuse to be handled from a given amount of raw material varies considerably throughout the four fields. In mine coal, this varies from a low

Jan 1, 1949

By C. O. Rison

HIGH explosives, particularly nitroglycerin, have been used in torpedoes for the purpose of shooting oil and gas wells for more than 60 years. The early history of the oil industry in Pennsylvania is not clear as to who actually torpedoed the first well, although in 1865 the Roberts Torpedo Co. procured a patent covering the process. Gunpowder was first used, although nitroglycerin was substituted shortly afterwards. Wells are shot for the purpose of increasing the flow of oil and gas A shot-hole in the producing horizon, with its contributory fissures and fractures, increases the area of and stimulates drainage into the hole. The shot-hole also acts as a collecting basin from which the oil is pumped. As a rule, hard or close-grained sands or limes are shot, other more or less porous and soft formations usually do not require shooting. and might be injured by blasting. Shooting is also resorted to in mechanical trouble such as straightening crooked holes, sidetracking pipe or tools, and for severing frozen strings of casing or drill pipe. Explosives arc also used sometimes to extinguish oil or gas-well fires although that work, which involves unusual conditions and methods, does not properly come within the classification of oil-well shooting. Some Factors to Be Considered in Shooting Wells Although nitroglycerin has been used extensively for more than half a century in shooting oil and gas wells, there is still a great deal of uncertainty as to the proper method of shooting or the amount of explosive required to produce best results in a particular formation. The possibility of shooting unproductive or cavey formations above or below the productive horizons, shooting into lower water, destroying casing seats, and the splitting or collapsing of casing strings, are factors that require consideration. The engineering departments of a number of the larger oil companies are making a study of methods of shooting, and the amounts of liquid nitroglycerin or other explosives required in shooting various productive

Jan 1, 1929

By S. Gstalder, J. Raynal

Consideration was given to simple tests which could be performed on rocks to give a measure of rock drillability. Various methods of breaking rocks were considered and the hardness test developed by Schreiner was selected for this study. The test involves application of an increasing load on the rock face through a flat-faced cylindrical punch until rupture occurs. Test results show that hardness is a good measure of the breaking strength of rocks. Useful relationships are shown to exist between hardness and other physical quantities such as specific disintegration, Young's modulus and sonic velocity. Specific disintegration (volume of rock broken per unit of work input) provides a possible means of comparing the effectiveness of other methods of rock breakage. The relationship between hardness and sonic velocity may be very significant for it may be possible to deduce rock drillability from sonic log data. provided that a mineralogical factor is taken into account. TO test further the results of the work, laboratory drilling tests were performed which closely simulated down-hole pressure conditions. Correlations of drilling results with rock hardness measurements were quite good. It was concluded that rock hardness, as measured in the laboratory or as deduced from sonic logs, could be used in relations for predicting rock drilling performance. INTRODUCTION Drillability of rocks cannot be defined in an absolute manner by a single quantity or measured by a single test. Resistance of rock to drilling depends to a large extent upon the means used for rock destruction. This complicates drillability classification of rocks for there may be as many classifications as there are methods of rock breakage without known functional relations between them. The objective of this work was to develop. in terms of rock destruction behavior, means of selecting the best drilling method for a given rock or the conditions for optimum output from a given drilling method. ANALYSIS OF ROCK DESTRUCTION TESTS Gauthier and Baron' have reviewed the many test methods which have been developed for determining the resistance of rocks to breakage. These include drilling tests, punch tests, scratch tests, resistance to shock, wear tests, etc. A standard drilling test might be to determine the time required to drill a standard depth (1/16 in.) in a rock using a bi-cone microbit (1 1/4-in. diameter) when a standard load (417 Ib) is applied at a standard speed of bit rotation (110 rpm). From the standpoint of similarity, the results of microbit drilling tests would seem to be most representative of the several methods suggested above. However, evaluation of drilling performance by this method is only qualitative and cannot be applied directly to actual drilling conditions. Punch tests basically measure rock hardness. Punches of various shapes and sizes, including small cones for Vickers' and Knoop's tests, the wedge for Epstein's test and the right circular cylinder for Schreiner's test, have been used. Results of these tests lead to a quantitative hardness classification which would seem to be related to the resistance of rock to bit-tooth penetration. Scratch tests are related to the resistance of rocks to abrasion such as would be encountered in drilling with diamonds. Either the width of the scratch obtained at a fixed load or the load required to give a scratch of a fixed width may be used to evaluate surface hardness of the rock. This should be related to the resistance of the rock to wear. The above tests, and probably many others. give relative measurements of the breakage or destruction characteristics of rocks. There is no direct relation between results of these tests and the drillability of rocks. Also, the tests each measure different quantities which have different dimensions and they do not permit direct comparison of numerical values. As one step in rectifying the above difficulties. it is proposed that the results of all test methods be expressed in terms of volume of rock destroyed per unit of work required; this is referred to as "specific disintegration". Test results may then be reported in a form which shows both a classification of rocks in regard to each method and a comparison of methods with regard to each rock. The disadvantage in using specific disintegration is the difficulty of measuring this quantity with accuracy. The volume of rock damage is difficult to measure. as is the true value of work input. Rock heterogeneity adds to the

Jan 1, 1967

By Herty, C. H.

Iron oxide (FeO) plays an extremely important part in the manufacture of iron and steel. In the three major processes- blast-furnace, open-hearth, and Bessemer converter-iron oxide is the chemically predominant compound and controls to a large ex- tent the operation of the furnaces and the composition and quality of their respective products. In order to emphasize the importance of iron oxide in each process, they will be considered individually in some detail. THE OPEN-HEARTH FURNACE. Iron oxide is introduced into the open-hearth furnace in four ways : 1. The scrap charged into the open hearth is oxidized by the furnace gases, the amount of oxide formed depending primarily on the amount and type of scrap charged. It has been found' that with large scrap, 1.7 Ib. of FeO is formed per 100 Ib. of scrap charged, whereas with scrap of medium size about 5.3 Ib. of FeO is formed per 100 Ib. of scrap charged, when the period between the charging of the scrap and the addition of hot metal is 3 hours. 2. The decomposition of the limestone sets free CO, by the reaction

Jan 1, 1957

By Charles S. Barrett

There is a road into the microscopic realm that has remained untraveled through all these years of intense activity with high-power optical and electron microscopy. The road is worthy of careful scouting by metallurgists and other investigators, for it leads into relatively new country and it makes some areas accessible that heretofore could be reached only by very indirect paths or by the use of imagination. And when the road passes through familiar territory it frequently permits a new view of commonplace things that should prove of value from time to time. An accepted way to interest people in new sights such as this is to present an illustrated travelogue. This I propose to do, using many pictures taken in my recent exploration of this road. In the manner of travelogues, I shall touch briefly upon a large number of different subjects in physical metallurgy and shall attempt to give an exhaustive treatment of none, for the objective is to provide a means for further research, to interest others in it, and to indicate what appears at the moment to be profitable directions for it to take. The method I shall present involves X-rays, but does not make use of the usual accompaniments of X-ray research such as reciprocal lattices, Fourier series, or the stereographic projection. The method is so simple in its fundamentals that it could have been developed 2o years ago, or perhaps even 30 years ago. It is well to have a destination for our travels, so that when we are through we shall have explored some region of importance, despite our preoccupation with the novel means of transportation and our interest in the sights to be seen along the way. So let us name the Cold-worked State as our destination, and make side trips into the territories known as Recovery, Recrystallization, and Precipitation-hardening. A great many investigations have been made of the nature of cold-worked metal, and a great variety of methods used, many of which are indirect, such as X-ray line intensities, X-ray line widths, calori-metric measurements, and magnetic measurements. Since comprehensive reviews of these investigations have been published in recent years, they need not be discussed here. The investigations that were the direct forerunners of the present work should be first mentioned. In 1931 I became interested in the structure of individual spots in X-ray diffraction patterns.l When a crystal is placed in the narrow pencil of X-rays in a Laue camera, the spots recorded on the film are not always uniformly black, but may have an internal structure. The meaning of this may be understood from Fig. I, which represents a narrow beam containing X-rays of many wave lengths (''general radiation") penetrating a crystal in the direction of the arrow and forming a pattern on the vertical film at the right.

Jan 1, 1945

I. MCLAUGHLIN, R. P.-Protecting California Oil Fields from Damage by Infiltrating Water. Discussed by M. E. Lombardi, A. F. L. Bell, A. C. McLaughlin, R. P. McLaughlin, William A. Williams, Mark L. Requa, C. D. Keen 2413 BEST, W. N.-Petroleum as Fuel Under Boilers and in Furnaces. Discussed by William A. Williams, Hennen Jennings, David T. Day, Mark L. Requa, A. F. L. Bell, W. N. Best 2420 JOHNSON, ROSWELL H.-Sliding Royalties for Oil and Gas Wells. Discussed by William A. Williams, A. C. McLaughlin, A. F. L. Bell, Roswell H. Johnson 2423 BELL, ARTHUR F. L.-Important Topping Plants of California. Discussed by William A. Williams, David T. Day, A. F. L. Bell 2426 LOMBARDI, M. E.-The Cost of Maintaining Production in California Oil Fields. Discussed by C. D. Keen, Mark L. Requa, H. M. Bacon, M. E. Lombardi 2427 HUNTLEY, L. G.-Oil, Gas, and Water Contents of Dakota Sand in Canada and United States, Discussed by E. W. Shaw 2428

Jan 12, 1915

By E. W. Lithgow, E. G. Williams, R. R. Holbrook, B. R. Wilson

The mineralogy and geochemistry of Pennsylvanian shales and underclays were studied to determine their suitability for lightweight aggregate and refractory ladle brick. Eighty percent of the variation in bloating of shales and clays was explained by the variation of Si02, A1203, and fluxes (Fe203, MgO, CaO, Na20, and K20); 60% by variation in quartz, kaolinite, illite, and chlorite. The best bloating was exhibited by marine shales, whereas freshwater shales and underclays experienced little or no expansion. Regional paleogeographic maps o f Pottsville and Allegheny shales permit bloating to be geographically predicted. It was found that clays meeting the specifications for refractory ladle bricks were obtained from underclays having over 34.5% mica, over 40% kaolinite and less than 15% quartz. Underclays of this composition are confined to the lower Allegheney outcropping along the near-margins of the coal basin. The best clay is that underlying the Lower Kittanning coal. Porosity of the first fired brick was found to be inversely correlated with reheat expansion.

Jan 1, 1975

By Maurice Grieves

The great majority of shafts constructed today are still excavated by drilling and blasting, a method which changed very little in over 100 years until the introduction of the mechanical lashing unit and cactus grab by the South Africans, which enabled muck to be removed as fast as massive hoisting systems could handle it and resulted in very rapid rates of sinking. Record breaking month's performances were achieved at -Hartebeestfontein No. 4 shaft, October 1960-337.1 m; Western Reefs No. 4 shaft, October 1961-340.7 m; and Buffelsfontein eastern twin shaft, March 1962-381.2m. The method was very labor-intensive, requiring a crew of over 60 workers at the shaft bottom during the drill cycle. Safety precautions were strict, but in the drive to achieve rapid advance, cases of personal injury were still somewhat high because of the large number of people engaged in this potentially hostile environment. The South African method, as it came to be referred to throughout the rest of the world, was adopted in the United Kingdom in the late 1950s in a modified form with greatly reduced manpower and nonsimultaneous sinking and lining, which was insisted on by the British Mines Inspectorate. In that instance, it was successfully used to sink the 7.3-m-diam concrete-lined shafts at Kellingley to 770 m depth, with rates of advance of over 90 m/month achieved, a British record at that time. During the sinking of the 1.15-km-deep twin shafts at Boulby potash mine in the UK in 1970, the method was again used, but for the first time ever in Britain exemptions from the mining code permitted the use of crash beams, crash doors, jack catches, and semi-simultaneous sinking and lining techniques. New British shaft sinking records of over 120 m/month were achieved in both shafts. Similar equipment and techniques were used in the early 1970s to sink several deep shafts in Canada, notably Creighton #7 and the Con zinc mine at Yellowknife in the NW Territories. Today, this equipment is standard for deep shafts in the US and the rest of the world. However, with the tremendous escalation in mining labor costs, the impact of health and safety legislation, and environmental regulations, coupled with a very real shortage of miners willing to work in this exposed situation it was apparent that an alternative to the labor-intensive conventional method of shaft construction had to be found. Recognizing the trend is inevitable, one or two major German shaft sinking contracting firms began to take a fresh look at full face boring techniques applied to tunnels and raise bored shafts. The results were most encouraging. Tunnel drivage techniques using moles had developed considerably from Colonel Beaumont's original channel tunnel machine circa 1880 to the superbly engineered Priestley machine selected to cut the British side in 1975 and the double shielded Robbins Grandori borer on the French side of the English Channel. Full face tunnel machines were being successfully used to drive uphill in inclined shafts in Austria and Switzerland. At Mapprag in Switzerland, the Demag mole drove the first (intentional) vertical transition and curve, and then went on to successfully complete the 730-m-long penstock shaft at an inclination of 35°. In Austria, the Wirth mole drove the Kaprun Glacier ski-lift railcar tunnel at record breaking rates of 457 m/MONTH (best 30 m/d) through green schist at an inclination of 29° for a distance of 3.35 km while the Hydro tunnel at Sarrelli in Switzerland was being driven by the Robbin's mole at an inclination of 35°. Simultaneously, extremely promising results were obtained using large assemblies of cutter discs on raise borer heads, such as the 4.87-m-diam X 460-m-deep shaft raised by Teton for Jim Walter Resources Inc. Bearing in mind that most mine shafts in the future (unless in exceptionally competent rock) will require some form of lining, and the trend will be toward deeper shafts as the more easily accessible mineral deposits become exhausted, it was seen that normal raise boring had definite limitations in vertical accuracy, in the limitation imposed by the drill string on the available torque that could be applied to the cutter head, and in the risk of collapse of the unsupported shaft rock wall in friable or jointed and fissured ground, since it is not possible to apply any form of temporary support until the permanent lining is being installed. A further problem was the economics of installing a subsequent lining, necessitating setting up a headgear and hoisting arrangement approaching in size that required for conventional drill and blast sinking and lining. Because of the economics, German contractors opted for a phased transition from drill and blast to the full face, rodless, out of the solid shaft mole, by starting off with a down-the-hole shaft boring machine -without a drillstring-but using a pilot hole to get rid of the muck.

Jan 1, 1982

By J. R. Finlay

The Cæur d'Alene silver-lead mining district of northern Idaho is probably best known to the general public as a seat of labor-troubles. So far as the writer is aware, little has been written and little is known about its geology and resources. People interested in lead-smelting are, of course, cognizant of the economic importance of the region, but they have not communicated much of their knowledge to the public. Exact figures as to the total output of the district are not obtainable, but the following estimates, covering the entire output of the 15 years during which the mines have been operated, are believed to be approximately correct: Group of Mines. Product. Wardner Group, including the Bunker Hill and Sul livan, Empire State-Idaho, Last Chance, Sierra Nevada, bur d'Alene Development Co... . $17,500,000 Cafion Creek Group, including the Gem, Frisco Con solidated, Granite, Standard, Mammoth, Hecla, Tiger-Poorman, Custer and Bell,.... 35,000,000 Mullan Group, including the Morning, You Like and Gold Hunter,........7,500,000 $60,000,000 This output covers the period of discovery and early struggles, and several periods of stagnation caused by strikes and other serious labor-troubles. In 1900 the output of the district was fully $10,000,000, and this figure would have been considerably increased in 1901 had not a curtailment of production been forced by the condition of the lead-market. In 1901 the product was about 150,000 tons of concentrates, with a gross. value of $8,250,000.

Jan 1, 1903

By T. T. Read

JAPAN'S iron and steel industry has always been closely connected with military strategy. Many years ago it became evident that the country's iron-ore resources were too small to support any extensive industry. As a result a belief in the imperative necessity of securing such resources has influenced Japan's political and economic policy in the Far East. Iron-ore developments in China are too well known to need repeating except to note that they have been rather unsatisfactory to both China and Japan. The ore deposit at Tayeh, in China, is not as large as was first believed and, though that and other sources of supply in China proper are now furnishing Japan a little more than a million tons of ore yearly, it cannot be counted upon as a large permanent source of supply. The deposit in Shantung proved so disappointing on further exploration that operations there have, so far as I know, long since ended. The operations at Pen-bsi-hu, in South Manchuria, which C. F. Wang de¬scribed in the A.I.M.E. TRANSACTIONS for 1918, Vol. 59, were reported to have yielded 84,000 tons of pig iron in 1928 and about 50,000 in 1935, so they seem to be going back.

Jan 1, 1937

By George C. Branner

STATE geological surveys have had an interesting development in this country. They first appeared more than a hundred years ago. The fact that they have persisted and are now an important part of most state governments indicates the basic need for state departments con-cerned with mineral problems. The number of state surveys in 1941 (43) is at an all-time high, as is the aggre¬gate appropriation for their support for the fiscal year 1940-'41 ($1,600,708). The first surveys, those of North and South Carolina (see Fig. 1), made their appearance in 1820-'30, but neither survived that period. During the next two decades surveys were created in twenty states, but only three survived. In fact, it was not until the decade 1900-'10, when eighteen surveys were created and only five abolished, that these agencies became firmly established.

Jan 1, 1941

Jan 1, 1896

By F. Weinberg

Lead single crystals have been deformed in tension over the temperature range of 4.2°K to the melting point. Changes in flow stress resulting from temperature cycling and strain rate cycling have been measured as a function of temperature for crystals of different orientations and purity. It was found that the flow stress ratio, after correcting for the temperature dependence of the shear modulus, decreased progressively with temperature above approximately 0.5Tm. The activation energy calculated from the high-temperature portion of the curve was found to be markedly higher than that of self-diffusion. For single glide crystals, the corrected flow stress showed an increase above 0.5 Tm before decreasitzg with temperature. This increase is attributed to static recovery occurrittg during temperature cycling. THE temperature dependence of the flow stress, based on temperature cycling and strain rate cycling, has been extensively investigated,' and on the basis of these results dislocation models of the work-hardening process have been proposed. In general, the flow stress is divided into two parts, ts, the short-range interaction term, which is only effective at low temperatures and which decreases with increasing temperature, and TG, the long-range stress term, which is independent of temperature after allowing for the temperature dependence of the shear modulus. The observations demonstrating that tG/µ is independent of temperature were generally carried out at low temperatures to minimize recovery effects. Several investigations have been reported on flow stress measurements at high temperatures2"5 which demonstrate that TG/µ does not remain constant at temperatures above 0.5Tm (where Tm is the melting temperature of the material in OK). Specifically, Hirsch and warrington3 carried out temperature cycling tests at two strain rates on single and polycrystalline aluminum up to 0.8 Tm and on polycrystalline copper. For aluminum they found that the flow stress ratio (the flow stress at temperature T2, divided by the flow stress at the reference temperature T1 in one temperature cycle) dropped progressively with increasing temperature above 0.5Tm. From the slopes of the high-temperature portions of the curves, they determined an activation energy for the deformation process of 1.6 ev (at best) which they considered was in agreement with the activation energy of self-diffusion, 1.35 ev. Calculations of the activation volume demonstrated that the deformation was not controlled by dislocation climb. They proposed a mechanism in which the rate-controlling process at high temperatures was due to the rate of move- ment of vacancies away from jogs, i.e., that of self-diffusion. Results of Lucke and Buhler4 on single crystals of aluminum confirmed this conclusion. They measured the critical resolved shear stress of aluminum over a wide range of temperature and strain rates. They found that the temperature dependence of the critical resolved shear stress was similar to that of the flow stress ratio, as determined by Hirsch and Warrington, and from their data calculated an activation energy for high-temperature deformation of 1.35 ev identical to that of self-diffusion. More recently Gallagher5 has carried out a detailed investigation of the temperature dependence of the flow stress ratio of copper, silver, and gold. In all cases, he found that the flow stress ratio, after adjusting for the shear modulus temperature change, drops at high temperatures. The activation energies he determined were found to be appreciably higher than the activation energy of self-diffusion of the material being considered. The flow stress ratio was found to be dependent on the orientation of the material, and, in addition, an anomalous increase in the flow stress ratio for copper, oriented for single glide, was observed above 0.5Tm. The purpose of the present investigation was to measure the critical resolved shear stress, the flow stress ratio, and the strain rate sensitivity of lead, primarily as a function of temperature. The results should indicate whether, following Lucke and Buhler, the critical resolved shear stress of lead has the same temperature dependence as the flow stress, and, following Hirsch and Warrington, whether the activation energy for high-temperature deformation in lead is the same as that of self-diffusion. Lead deforms as a normal fee material,6'7 is available in high-purity form, can readily be grown as single crystals, and, for this investigation, has the very considerable advantage of having a low melting point, 327°C. The observations of the critical resolved shear stress of lead have been published elsewhere.' EXPERIMENTAL PROCEDURE The experimental procedure was essentially the same as that used in the critical resolved shear stress measurements.' Single crystals of 99.999 pct (59) and 99.9999 pct (69) lead were deformed in tension with a table-model Instron in a silicone oil bath above room temperatures and in a cooled methyl alcohol or liquid-nitrogen bath below room temperatures. The test specimens were rectangular in section, 0.65 by 0.33 cm, and had a 5-cm gage length. The specimens were grown as single crystals with tapered ends, which fitted into matched tapered grips for testing. To obtain the flow stress between two temperatures, specimens were first deformed approximately 1.0 pct at the higher temperature. The test was then stopped, the load relaxed, the oil bath removed without disturbing the specimen, the grips and specimen cooled with a fan and then immersed in liquid nitro-

Jan 1, 1969

By R. A. Meussner, C. T. Fujii

Chromium solution in wustite depresses the oxygen activity in a nonideal manner and expands the lattice slightly. Gravimetric measurements of the equilibrium compositions of wustite containing 0.00 to 1.38 wt pct Cr define the oxygen potential (CO2-CO atm) and the limits of the phase field at 1000°C. These data extrapolate to a maximum solubility of 2 wt pct Cr. The lattice parameter data, room-temperature measurements of quenched samples, differ significantly from those in the literature. Both pure and chromium wus-tites contract at uniform and equal rates as the oxygen content (metal deficit) increases. The a. US metal deficit relationships are straight lines showing none of the curvature previously reported. At constant metal deficit, the a. expands by 0.002? on alloying with 0.4 to 0.5 wt pct Cr but is insensitive to further chromium additions: a small expansion rather than a marked contraction. These results require a modification of the accepted alloying mechanism. IN the high-temperature oxidation of Fe-Cr alloys in Ha-H,and CO2-CO atmospheres the vapor transfer of oxygen from the continuous wustite outer scale to the porous inner scale/alloy interface sustains the high oxidation rates.1"3 The driving force for this transport is the difference in the oxygen activity of the outer wustite and that at the inner scale/alloy interface. In pure CO2, as well as in CO2-CO atmospheres, carburization of the alloy accompanies this oxidation. Current efforts to evaluate the parameters controlling this carburization have shown that the process is not simple; i.e., the carbon concentration in the alloy initially increases rapidly, reaches a maximum, and then decreases slowly as the oxidation time is extended. This is the same pattern reported by McCoy for the more complex oxidation-carburization of stainless steels and an Fe-Cr alloy in CO2 at lower temperatures.4 These changes in the carburization process occur while the overall oxidation rate and the lattice parameters of the scale layers remain constant. If this invariance of the lattice parameter is assumed to indicate a constant scale composition and thus a constant oxygen potential, the carburization results are not easily explained. Electron microprobe traces across the thickness of these outer scales, however, have revealed distinct chromium gradients penetrating 10 to 50 µ from the inner surface where the chromium concentrations were estimated at a few tenths percent. The variation of the chromium cmcentration on the inner surface of the scale, and the resulting change of the oxygen activity, during the oxidation process is considered to be important in defining the carburization process. Thus, to gain an understanding of the complex oxidation-carburization proc- ess, it was necessary to measure the properties of wustite containing known amounts of chromium (chromium wustite). Although the general features of the Fe-Cr-0 equilibrium diagram between 900° and 1300°C have been fairly well established by Richards and white: Wood-house and White,6 Seybolt,7 and Katsura and Muan,8 there have been no detailed studies of the limits of the chromium wustite phase field or the properties of these alloyed wustites. The recent results of a limited study of chromium wustite by Levin and wagner9 indicate that more than 0.67 wt pct Cr is soluble in wustite above 850°C and that this alloying is accompanied by a substantial lattice contraction. This change in the lattice parameter was not evident in the X-ray diffraction patterns of wustite layers from the oxidation experiments;1,3 the lines were sharp even though a chromium gradient existed in the scale. The present paper describes gravimetric equilibrium experiments which delineate the boundaries of the chromium wustite single-phase field at 1000°C and define the changes in the oxygen activity and the lattice parameter of wustite as functions of chromium and oxygen contents. The lattice parameter data of chromium wustite obtained from these equilibrium and special quenching experiments differ considerably from those reported.9 Those for pure wustite show significant differences from the widely accepted data of Jette and Foote.10 Since the causes of these differences are not easily assignable, and since the literature contains many sets of data on wustite which if not in conflict are at best not in harmony, the experimental procedures are discussed in the present paper. EXPERIMENTAL Oxide Preparation. The specimens used in these studies were porous pellets compacted from high-purity (Fe,Cr)2O3 or Fe2O3 powders. These powders were prepared from electrolytic chromium (99.8 pct purity) and electrolytic iron purified by consumable-electrode, vacuum arc-melting processing (299.9 pct purity).11 The oxides were produced by standard analytical procedures: solution of the metals in acids (HC1, then HNO3 added), coprecipitation of the hydroxides (NHaOH), and filtering and washing these precipitates. Initial dehydration of the coprecipitated hydroxides was done in a porcelain evaporating dish heated by a Meker-type burner, final dehydration by firing in a recrystallized alumina crucible at 1000" to 1050°C for 20 hr in an electrically heated furnace. Spectrographic analysis detected the following impurities: silicon, 0.01 pct or less; aluminum, 0.001 pct to trace; manganese and copper, 0.0001 pct to none. Each of these levels is at least one order of magnitude lower than in commercially available CP grade ferric and chromic oxides. Fluorescence analy-

Jan 1, 1969