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By Richard McCaffery

THERE has been some discussion among blast-furnace operators regarding the relative merits of tuyeres of the converging type and tuyeres designed in an attempt to produce a diverging jet of air. An article1 on Progress in German Blast Furnace Practice indicates the interest in this subject abroad. This article illustrates a diverging type of tuyere which is shown here in Fig. 1A. The design appears to be rather poor as regards known properties of air flow. The adoption of this. tuyere, the article states, resulted in a decrease of blast pressure of about 4 lb. per sq. in. and an increase of the output of the furnace. If the improvements mentioned are due entirely to the change in tuyere design, the subject of tuyere design seemed worthy of investigation and this paper is a report of such work. Because of the gain in efficiency brought about by the use of a diverging tuyere in the German plant, it was thought desirable to investigate the shape of the air streams issuing from various-types of tuyeres to ascertain whether the gain was due to the tuyere itself or to the distribution of the air in the furnace. Since it is difficult to do experimental work on a full-sized furnace, or even on full-sized tuyeres, and because of the equipment available for the work, it was decided to carry out the work on scale models of tuyeres. Therefore, in this work, single tuyeres were used and the blast discharged into the atmosphere. The shape of the air stream was determined by means of a Pitot tube suitably supported in the air stream at various positions. The air was. furnished by a Roots blower driven by a 10-hp. direct-current motor having field control, and capable of discharging 250 cu. ft. per min. with a pressure on the discharge of 4 in. of mercury. A modern blast furnace with 21-ft. hearth requires about 50,000 cu. ft. per min. of free air at from 16 to 23 lb. per sq. in. pressure, depending upon the type of burden. This pressure is the total pressure required to force the air through the burden and through the tuyeres. Upon computation the pressure drop through the tuyeres is about 1 to 2 lb. per sq. in. By making the tuyeres to a one-fifth scale, and by using a pressure of 1.5 in. of mercury, the shape of the air streams should be

Jan 1, 1931

By J. F. Myers, S. E. Sharp

The safety data presented in this paper are based upon replies to a Questionnaire sent out to representative mining companics. The authors feel that it is a fair cross section of the milling industry, in that the 17 companies, of the United States and Canada, reporting on 22 mills, are scattered from the Hudson Bay to the Mexican border and from coast to coast. These data concern the accident records of the various plants from 1939 to 1944, inclusive and the six years are divided into two periods. The first period (1939, 1940 and 1941) represents something of a normal operating condition. The second period (1942, 1943 and 1944) represents the period of time that was most affected by war conditions. During the second period there was a high labor turnover, inexperienced workers were numerous, women replaced men in many kinds of work, a labor shortage existed more or less throughout the industry, and supervision was pushed for peak production. All of the companies reporting compiled their accident experiences for these six years in accordance with the standards set up by the American Standards Association (New York, N. Y.), consequently the tabu lated data presented herein are comparable. The authors of this paper feel that the industry as a whole is greatly indebted to the personnel of the companies that furnished these data, which make this study possible for presentation. This survey covers a total exposure of 74,528,880 man-hours, with 105,471 man-days of lost time from 870 accidents. Safety Records In Table I, the safety record is shown of the various mills reporting. The severity rate is usually conceded to be the most vital statistical figure in safety parlance, therefore the participating companies are listed in order of their severity rate for the combined six-year period, under size of organizatiori. The table also shows the frequency rate as well as the frequency-severity ratio (F/S). As noted in Table I, most of the companies suffered an increase in both severity and frequency rates during the second period; only six of the 22 enjoyed an improvement. From correspondence with the various plants, it seems that a few had very little labor shortage or turnover, and these were not greatly affected. A few plants, anticipating the situation, strengthened their training facilities and actually were able to show a better experience during the second period. This gives great credence to the value of organized training in any safety program. The frequency-severity ratio (F/S) shown in the last column of Table I offers

Jan 1, 1947

By S. E. Sharp, J. F. Myers

The safety data presented in this paper are based upon replies to a Questionnaire sent out to representative mining companics. The authors feel that it is a fair cross section of the milling industry, in that the 17 companies, of the United States and Canada, reporting on 22 mills, are scattered from the Hudson Bay to the Mexican border and from coast to coast. These data concern the accident records of the various plants from 1939 to 1944, inclusive and the six years are divided into two periods. The first period (1939, 1940 and 1941) represents something of a normal operating condition. The second period (1942, 1943 and 1944) represents the period of time that was most affected by war conditions. During the second period there was a high labor turnover, inexperienced workers were numerous, women replaced men in many kinds of work, a labor shortage existed more or less throughout the industry, and supervision was pushed for peak production. All of the companies reporting compiled their accident experiences for these six years in accordance with the standards set up by the American Standards Association (New York, N. Y.), consequently the tabu lated data presented herein are comparable. The authors of this paper feel that the industry as a whole is greatly indebted to the personnel of the companies that furnished these data, which make this study possible for presentation. This survey covers a total exposure of 74,528,880 man-hours, with 105,471 man-days of lost time from 870 accidents. Safety Records In Table I, the safety record is shown of the various mills reporting. The severity rate is usually conceded to be the most vital statistical figure in safety parlance, therefore the participating companies are listed in order of their severity rate for the combined six-year period, under size of organizatiori. The table also shows the frequency rate as well as the frequency-severity ratio (F/S). As noted in Table I, most of the companies suffered an increase in both severity and frequency rates during the second period; only six of the 22 enjoyed an improvement. From correspondence with the various plants, it seems that a few had very little labor shortage or turnover, and these were not greatly affected. A few plants, anticipating the situation, strengthened their training facilities and actually were able to show a better experience during the second period. This gives great credence to the value of organized training in any safety program. The frequency-severity ratio (F/S) shown in the last column of Table I offers

Jan 1, 1947

By Philip S. Morse

THE Australian lead-smelting plants began to use charges carrying high zinc percentages somewhat earlier than was common with American plants. When lead smelting first started in Australia the immense deposits of oxidized lead at Broken Hill were available but later these oxidized ores became exhausted and were replaced by sulfides. This was before the days of flotation and these sulfides when concentrated carried about 1 per cent. of zinc to 6 per cent. of lead. The works of the Sulphide Corpn. at Cockle Creek was perhaps the pioneer in high-zinc slags but the Port Pirie plant of the Proprietary Co. was a close and very able second and has continued the work to the present time. The Cockle Creek lead furnaces remained in operation until shortly after the war when most of the Broken Hill companies combined and took over the Port Pirie plant to treat their concentrates. As it was the practice both at Cockle Creek and Port Pirie to carry 20 per cent. or more of lead on the charge, it was found that under these conditions of large amounts of zinc in the charge, good roasting was absolutely necessary and matte production was unwise. The Hunting-ton-Heberlein system of roasting was introduced and later the Dwight & Lloyd process. In this way, by roasting the sulfide portions of the charge as thoroughly as possible and making no matte, a method of smelting was developed where the slag over long periods carried as high as 20 per cent. ZnO without serious furnace troubles, and slags carrying even up to 33 per cent. ZnO have been reported. The zinc slags were not very different in appearance from the ordinary slags produced in American practice except that they gave off more smoke and fume on tapping. The slag usually ran hot and freely, coming from the tap in a full stream. Normally there was little crust on the sides of the furnace and the tuyeres gave no trouble though they were always rather dark. At the works of the Sulphide Corpn. it was the custom, on account of the labor situation, to shut down the furnaces during the Christmas holidays, thus giving a campaign of about 12 months. The furnaces at the end of the run usually showed no crust on the sides, though crusts always occurred at the back and front ends. A furnace campaign of 22 to 23 months has been made at this plant where both sides of the

Jan 1, 1929

By H. J. Levinstein, H. J. Guggenheim

RbFeF3 is a transparent ferromagnet with a large faraday rotation which permits the direct observation of magnetic domain structures in bulk crystals. If the position of dislocations within the crystal were known a study of domain wall dislocation interactions would be possible. In this paper an etch pitting solution is described which gives a one-one correspondent between the etch pits and the dislocations intersecting the (100) surfaces of RbFeF3 crystals. In addition, RbFeF3 is shown to have sufficient plasticity so that known arrays of dislocaticms can be put into the crystal. It is concluded that RbFeF, is an ideal material for the investigation of domain wall dislocation interactions. THE influence of lattice defects on the motion of domain walls in ferromagnetic materials has been studied extensively both theoretically and experimentally.4 The experimental data obtained has been qualitative in nature due to the lack either of a quantitative knowledge of the magnetic domain array in the material or of the nature of the dislocation configuration in the material. At room temperature RbFeFJ has the cubic perovskite structure. It is ferromagnetic below 86°K.5,6 It is also transparent and has a large faraday rotation in the magnetic state.7 The domain structure of this material is observable in three dimensions in crystals which are millimeters in thickness.' Since RbFeF3 satisfies the requirements of having an easily visible three-dimensional magnetic domain structure, it was of interest to determine if the dislocation structure of the material could be determined and if the material was sufficiently plastic so that dislocations could be introduced into the as grown crystals. This is a report of the results of that investigation. EXPERIMENTAL PROCEDURE The crystals of RbFeFs used in this experiment were grown by a technique described elsewhere.5 In order to obtain flat strain-free surfaces, the samples were first cut to the crystal orientation desired and the surfaces were polished by employing standard metallographic techniques. The samples were then immersed in a solution of 1 to 3 g of KOH in 100 ml of water. This solution removes the damaged surface layers uniformly leaving a film on the surface of the sample. Etch pits are obtained by immersing the sample in an approximately 50-50 solution of 30 pct peroxide and concentrated acetic acid. The film formed during the KOH treatment turns deep red in color in the etching solution and flakes off the sample. The etching time required depends upon the pit size desired and

Jan 1, 1970

By J. C. Fisher, J. H. Hollomon, David Turnbull

Understanding of the diffusion problem has recently been furthered by the analysis of Birchenall and Meh1.l They pursued the problem of the variation of the diffusion coefficient with composition for non-ideal solid solutions. Their analysis follows the tradition of Wagner,l Jost, Dehlinger, and Darken & who assumed the net flux of diffusing material to be proportional to the gradient of a quantity related to free energy. The basic assumption in Birchenall and Mehl's formulation of the problem is that the net flux of diffusing material is proportional to a thermodynamic activity gradient. To estimate the applicability of the derived relations, they corrected the diffusion coefficients of carbon in austenite by utilizing Smith's6 activity data for carbon, and the diffusion coefficients for zinc in copper with activity data computed from the vapor pressure measurements of Har-greaves.' The corrected coefficients for carbon were virtually independent of carbon concentration. For the diffusion of zinc in copper a moderate variation of diffusion coefficient with concentration remained after the correction. The problem of diffusion can be formulated in another way than that used by Birchenall and Mehl. The method is that of chemical rate theory and has been used by Eyring and his coworkers8,9 as well as by Eyring and Zwolinskilo in a discussion to Birchenall and Mehl's paper. As yet the method has not been applied to substitu-tional solid solutions. On the basis of their assumptions, Eyring and Zwolinski derived a relation between the diffusion coefficient and activity that is identical with that of Dehlinger and Darken but which does not correct for the variation of the diffusion coefficient with concentration as well as does the relation derived by Birchenall and Mehl. It was thought that the theory of diffusion would be more complete if the inconsistency between the two analyses could be rationalized and if diffusion in substitu-tional alloys were analyzed on the basis of the concepts of the chemical rate theory. Chemical Rate Theory According to the theory of absolute reaction ratess the reaction +..... +X, Eq I is viewed as taking place in two steps. First the reactants A1, A², . . . A; combine to form an activated complex M with which they are in equilibrium: A1 + A1+ . . . + A=M. Eq 2 Second the activated complex decomposes to give the products XI, XZ, . . . Xi: M?X, + X²+ . . . +Xi Eq g It has been showns that the number of activated complexes decomposing per unit volume per unit time is given by the expressiont kT -h CM † The transmission coefficient has been taken as unity.

Jan 1, 1949

By David Turnbull, J. H. Hollomon, J. C. Fisher

Understanding of the diffusion problem has recently been furthered by the analysis of Birchenall and Meh1.l They pursued the problem of the variation of the diffusion coefficient with composition for non-ideal solid solutions. Their analysis follows the tradition of Wagner,l Jost, Dehlinger, and Darken & who assumed the net flux of diffusing material to be proportional to the gradient of a quantity related to free energy. The basic assumption in Birchenall and Mehl's formulation of the problem is that the net flux of diffusing material is proportional to a thermodynamic activity gradient. To estimate the applicability of the derived relations, they corrected the diffusion coefficients of carbon in austenite by utilizing Smith's6 activity data for carbon, and the diffusion coefficients for zinc in copper with activity data computed from the vapor pressure measurements of Har-greaves.' The corrected coefficients for carbon were virtually independent of carbon concentration. For the diffusion of zinc in copper a moderate variation of diffusion coefficient with concentration remained after the correction. The problem of diffusion can be formulated in another way than that used by Birchenall and Mehl. The method is that of chemical rate theory and has been used by Eyring and his coworkers8,9 as well as by Eyring and Zwolinskilo in a discussion to Birchenall and Mehl's paper. As yet the method has not been applied to substitu-tional solid solutions. On the basis of their assumptions, Eyring and Zwolinski derived a relation between the diffusion coefficient and activity that is identical with that of Dehlinger and Darken but which does not correct for the variation of the diffusion coefficient with concentration as well as does the relation derived by Birchenall and Mehl. It was thought that the theory of diffusion would be more complete if the inconsistency between the two analyses could be rationalized and if diffusion in substitu-tional alloys were analyzed on the basis of the concepts of the chemical rate theory. Chemical Rate Theory According to the theory of absolute reaction ratess the reaction +..... +X, Eq I is viewed as taking place in two steps. First the reactants A1, A², . . . A; combine to form an activated complex M with which they are in equilibrium: A1 + A1+ . . . + A=M. Eq 2 Second the activated complex decomposes to give the products XI, XZ, . . . Xi: M?X, + X²+ . . . +Xi Eq g It has been showns that the number of activated complexes decomposing per unit volume per unit time is given by the expressiont kT -h CM † The transmission coefficient has been taken as unity.

Jan 1, 1949

By Yves Dardel

INTRODUCTION SINCE the first determination of Dumas1 in 1880, many authors have tried to measure the solubility of hydrogen in solid aluminum, or at least the amount of dissolved gas in it. However, the interpretation of the results which have been obtained is still difficult. Sieverts,2 then Baukloh and Oesterlen,3 during their gassing experiments could not determine any solubility of hydrogen in solid aluminum. On the other hand, Portevin, Chaudron and Moreau,4 leaving the determination of the hydrogen solubility beyond the scope of their experiments, measured only the amount of gas that they could extract by high voltage positive ion bombardment and found up to 151 cm3 of gas per 100 g of metal. Winterhager,5 by repeated vacuum extraction during severe cold rolling, extracted up to 161 cm3 per 100 g. In both series of experiments, the extracted gas contained chiefly hydrogen with a small amount of nitrogen, carbon monoxide, carbon dioxide and methan. Later, Schmidt and von Schweinitz6 as well as Chaudron and Moreau7 showed the importance of the adsorbed layer of hydrogen, the extracted quantities being proportional to the surface and not to the weight of the sample, when its cleaning was not perfect. In earlier experiments, Steinhauser8 extracted from more massive samples nothing but a little amount (< 0. 5 cm3 per 100 g) of hydrogen, carbon monoxide and methane. Thus, according to these experiments the quantity of dissolved gas is probably very small and the effect of the surface could falsify the results of the extraction. However, owing to the care taken by Chaudron and his coworkers, it was clear that all the hydrogen extracted could not come from the superficial layer, or that the links which bound hydrogen to the surface were so strong that the usual method of cleaning could not destroy them. After the main parts of the experiments reported here had already been carried out, Eborall and Ransley9 published the results which they obtained with an analysor having an accuracy of 0.03 cm3 per 100 g, while that of the usual apparatus was only about 0.2 cm3 per 100 g. During all their experiments the adsorbed layer would have been a difficulty, for the value of the adsorbed hydrogen was approximately equal to that of the dissolved amount. [ ] Since always keeping the same adsorbed layer is very difficult, an error in the correction for the adsorption can be made when using the apparatus of Eborall and Ransley, as well as the earlier apparatus,

Jan 1, 1948

By J. T. Peters, N. Schapiro, R. J. Gray

Petrographic studies of coal have resulted in a better understanding of the origin and composition of coal and have added to the knowledge of how and why coals differ in their response to various prepamtion and utilization processes. Petrographic methods can now be used in scientific economic exploitation of coals. Because the United States Steel Corp. is one of the largest consumers of coal and coke, there is a continuing interest in the corporation in perfecting a better understanding of coal so that it can be utilized more effectively. Coal is a heterogeneous substance composed principally of plant material that has been altered by a complex geochemical process to form rock. The science of coal is anthracology. The ultimate aim of anthracology is determining the relationships and differences among coals. The fundamental aim is finding out why coals differ. The practical application is determining how the differences in coals affect their utilization properties. Coal, like other sedimentary rocks, consists of more than one material. Fig. 1, a photograph of a natural fracture and a polished surface of a lump of coal, displays heterogeneity in terms of the banded ingredients present. The earliest attempts to describe coal were based on its hardness and appearance. &apos; Thus, coal has been described as hard or soft, bright or dull, and banded or nonbanded. The variations in the hardness and physical appearance of the coal reflect differences in materials that constitute the coal. The banded nature, lustre, and texture depend upon the relative proportions of the various constituent materials. Even the earliest petrographic investigations of coal produced evidence of of the heterogeneity of the coal substance and shoul have destroyed the concept of the unit coal molecule. Coals (Fig. 2) that appear the same frequently consist of different microscopic materials and may behave differently during mining, pulverization, washing, or coking. In Fig. 3, the upper photograph shows a bright at-trital medium-volatile coal, and the micrograph at the right shows some of the materials that constitute the coal. The lower photograph shows a bright attrital low-volatile coal and the corresponding micrograph shows material of similar origin to those from the medium-volatile coal. Any petrographic description of a coal that has meaning in terms of its utilization begins with a microscopic examination. Numerous attempts have been made to describe coal on the basis of the materials that constitute the coal.2*3 Initial petrographic studies were directed towards the question of the origin of coals without any true basis for studying the metamorphic changes in the

Jan 1, 1962

By Ottey M. Bishop, William G. Peryam, Fred E. Johnson

THE Lepanto Consolidated Mining Company is the largest copper producer in the Philippines, and the only one that makes a concentrate valuable principally for its copper; also, it has the only productive copper mine situated at considerable distance from the sea, and is the only one in the islands operating its own smelter. The Lepanto mine is in the Municipal District of Mankayan, sub-province of Benguet, near the heart of the Mountain Province of Northern Luzon. It is 165 km. from its shipping point at San Fernando, Province of La Union, on the shore of the China Sea. Elevations at the property range from 3200 to 4500 ft. The climate is very mild; temperatures are seldom below 50° or above 80°F. Annual rainfall approaches 170 in. and is mainly confined to a rainy season lasting from May to October. The months from December to April, inclusive, are usually extremely dry. This climatic pecularity entails the problems of landslides on the roads during the rainy season and water shortage during the dry season. The Mountain Trail, an improved rocksurfaced toll road maintained by the Commonwealth Government, gives access to the property. The 105 km. over this road may be traveled in about 4 ½ hr. during the dry season. Very few sections of the road are straight for more than 100 meters, and about one third of it is a one-way road controlled by gates. All freight for the property is delivered by the Manila Railroad Company to Bauang, La Union, 45 km. west of Baguio and at sea level, where it is picked up by freight trucks and hauled via Baguio to Lepanto. Granulated matte is hauled in bulk from Lepanto in four-ton lots on freight trucks to the storage bins at San Fernando. Freight rates from Bauang to the property amount to [P]8.oo per ton, and from the property to San Fernando the rate is [P]16.00 per ton. The company pays the road toll, [P] 1.00 per truck, each way. THE CAMP The company maintains a modern camp, well separated from the mine and reduction plant. Comfortable and sanitary living quarters, water, and light, as well as free medical service are provided all employees. A hospital staffed by a doctor and two nurses takes care of all medical treatment. Considering recreational facilities of great importance, the company has provided two tennis courts, two basketball courts, and badminton courts for employees. Bowling alleys and a motion picture theater are operated by the company, the profits being expended for other recreational purposes. A moderate sized recreation hall serves for barrio dances, meetings,

Jan 1, 1942

By J. D. Mote, A. Rosen, J. E. Dorn

The effect of strain rate and temperature on the critical resolved shear stress for (1100) [1120] prismatic slip was determined for the intermediate hexagonal phase containing about 67 at. pct Ag and 33 at. pct Al. Whereas the flow stress increased only slightly as the test temperature was first decreased below room temperature, a rapid increase inflow stress was obtained with yet greater decreases in temperature from about 240" to 4°K. The effect of both temperature and strain rate on the flow stress over the low-temperature range could be completely rationalized in terms of the Peierls mechanism when the deformation is controlled by the rate of nucleation of pairs of kinks. A few years ago Mote, Tanaka, and Dorn1 observed that the critical resolved shear stress for prismatic slip of a 67 at. pct Ag plus 33 at. pct A1 hexagonal intermediate phase by the (1100)[1120] mode decreased precipitously as the test temperature was increased from 4" to about 160°K. Their results for both basal and prismatic slip are given in Fig. 1. It is obvious that only the flow stress for prismatic slip is strongly temperature-dependent, whereas the flow stress for basal slip is independent of temperature. If the temperature dependence of the flow stress were primarily due to interstitial impurities, it might be expected that they would influence the flow stress for basal slip as well. Since the activation volume at 115°K for prismatic slip was determined to be about 15b3, where b is the Burgers&apos; vector, this thermally activated deformation process was tentatively ascribed as being due to the Peierls mechanism. But the various analyses of the Peierls mechanism then available as formulated by Seeger2 and also by Lothe and Hirth3 did not agree well with the experimental data. Since that time a more realistic theory for the operation of the Peierls mechanism under conditions where the strain rate is determined by the rate of nucleation of pairs of kinks has been presented by Dorn and Rajnak.4 The present investigation was, therefore, undertaken in order to provide the essential data for a careful check on the agreement between this theory and the low-temperature deformation by prismatid slip of the above-mentioned Ag2A1 intermediate phase. EXPERIMENTAL TECHNIQUE Single-crystal specimens so oriented that the [1120] direction and the normal to the (1100) plane were at 45 * 2 deg to the tensile axis were grown from the congruent melting composition of about Ag2Al for the intermediate hexagonal phase by the

Jan 1, 1964

By T. V. Philip, R. E. Lenhart

When commercial silicon iron sheets of varying magnetic quality are isothermally annealed at high temperatures, extremely large grains develop in the material having good magnetic properties. These grains are of the (110) [001] orientation and are formed by secondary recrystallization. The primary driving force for this secondary recrystallization is grain boundary free energy. For the secondary grains, activation energies of 103 kcal per mole for nucleation, and of 75.5 kcal per mole for growth, were obtained. The activation energy for nucleation of the secondary grains is consistent with a model involving redistribution of a precipitate acting as the primary grain growth inhibitor. SINGLY oriented silicon iron sheet was first produced in 1935.1 The material as commercially produced today has a very highly developed preferred orientation or texture; up to 95 pct of the grains are crystallographically oriented with their (110) planes in the plane of the sheet and their [loo] directions parallel to the rolling direction. This texture, usually written as (110) [00l], is referred to as the "GOSS" or the "cube-on-edge" texture. Because the magnetic properties of this material are superior to those of the nonoriented sheets in the direction of rolling, the oriented silicon iron has acquired tremendous industrial importance especially in the manufacture of transformer cores and other electrical equipment. The commercially produced material is essentially an iron-silicon alloy containing about 3 1/4 pct Si with minor impurities totaling less than 0.15 pct. The silicon steel heat is melted in the open hearth or electric furnace. The ingots are hot rolled, with or without being slabbed, to strips of 0.100 to 0.080 in. thickness. They are then cold reduced to an intermediate thickness, recrystallized, cold reduced to final thickness, decarburized, and finally annealed at a high temperature. During this high-temperature anneal, extremely large grains with the cube-on-edge texture are produced in the sheet. Several papers have appeared in the literature2-10 relating to the production of the Goss-textured material. Most of these describe the textures produced on cold rolling and on subsequent annealing of single crystal or polycrystalline silicon iron. May and Turnbull11,12 have recently shown the necessity of a second-phase dispersed impurity in the material for the production of the Goss texture. However, none of these papers describes in detail the nucleation and growth kinetics of the (110) [001] grains during the final high-temperature anneal.* The present work, therefore, is an attempt to understand the nucleation and growth kinetics of the cube-on-edge grains in the silicon iron sheet during the final high-temperature anneal.

Jan 1, 1962

By Robert D. Pike

In November 1939, on behalf of the Harbison-Walker Refractories Co., the author undertook the study of the problem of utilizing the dolomite of northwestern Ohio for the manufacture of calcined magnesia suitable for use in refractories. Grateful acknowledgment is made of the unfailing assistance and encouragement throughout this work from the executive and technical staff of Harbison-Walker Refractories Company. The dolomite of the Niagara formation that is exposed or near the surface of a wide area in northwestern Ohio1 constitutes a vast supply of almost pure dolomite. It offers a virtually unlimited supply of cheap raw material of uniform dependable analysis for the manufacture of magnesia. A typical analysis of dolomite from the vicinity of Luckey, Ohio, follows: Stone Completely Calcined CaO(Sro)a............. 30.35 57.806 Mgo................... 21.55 41.050 SiO2. ................... 0.30 0.572 R2O3................... 0.30 0.572 Ignition loss............. 47.50 a SrO about 0.06 pct. Brines containing magnesium chloride or sea water can be reacted with calcined dolomite to produce magnesia.2&apos;3 In such reactions the MgCl2 of the brine supplies some of the magnesia and the amount of dolomite required is thereby reduced by an equivalent amount, but brines of commercial importance containing magnesium chloride are some distance away from the purest grades of the dolomite of northwestern Ohio. It was decided therefore to concentrate upon the development of a suitable process for separating the lime and magnesia of dolomite, depending upon the dolomite itself as the sole source of magnesia. This would make it possible to place a plant at the dolomite quarry, thus eliminating the cost of transporting the stone and also rendering the calcined magnesia available at a most convenient production point, considering the cost of delivery throughout the steel industry. The selection of a process depending solely upon the dolomite as a source of magnesia also necessarily entails production of the lime content of the dolomite as a by-product. It was recognized that if such a lime by-product could be produced in a suitable form, a plant location in northwestern Ohio would also be advantageous for marketing the lime. The problem, therefore, was the discovery and development of a low-cost process for separating the magnesia and lime of the dolomite of northwestern Ohio and producing each in a form relatively free from the other, and meeting the respective requirements of established markets. A satisfactory solution of this problem has been found, and it is the

Jan 1, 1948

By Robert D. Pike

In November 1939, on behalf of the Harbison-Walker Refractories Co., the author undertook the study of the problem of utilizing the dolomite of northwestern Ohio for the manufacture of calcined magnesia suitable for use in refractories. Grateful acknowledgment is made of the unfailing assistance and encouragement throughout this work from the executive and technical staff of Harbison-Walker Refractories Company. The dolomite of the Niagara formation that is exposed or near the surface of a wide area in northwestern Ohio1 constitutes a vast supply of almost pure dolomite. It offers a virtually unlimited supply of cheap raw material of uniform dependable analysis for the manufacture of magnesia. A typical analysis of dolomite from the vicinity of Luckey, Ohio, follows: Stone Completely Calcined CaO(Sro)a............. 30.35 57.806 Mgo................... 21.55 41.050 SiO2. ................... 0.30 0.572 R2O3................... 0.30 0.572 Ignition loss............. 47.50 a SrO about 0.06 pct. Brines containing magnesium chloride or sea water can be reacted with calcined dolomite to produce magnesia.2&apos;3 In such reactions the MgCl2 of the brine supplies some of the magnesia and the amount of dolomite required is thereby reduced by an equivalent amount, but brines of commercial importance containing magnesium chloride are some distance away from the purest grades of the dolomite of northwestern Ohio. It was decided therefore to concentrate upon the development of a suitable process for separating the lime and magnesia of dolomite, depending upon the dolomite itself as the sole source of magnesia. This would make it possible to place a plant at the dolomite quarry, thus eliminating the cost of transporting the stone and also rendering the calcined magnesia available at a most convenient production point, considering the cost of delivery throughout the steel industry. The selection of a process depending solely upon the dolomite as a source of magnesia also necessarily entails production of the lime content of the dolomite as a by-product. It was recognized that if such a lime by-product could be produced in a suitable form, a plant location in northwestern Ohio would also be advantageous for marketing the lime. The problem, therefore, was the discovery and development of a low-cost process for separating the magnesia and lime of the dolomite of northwestern Ohio and producing each in a form relatively free from the other, and meeting the respective requirements of established markets. A satisfactory solution of this problem has been found, and it is the

Jan 1, 1948

By Jeff Wilkinson, Brandon Walter

"A&N Electrical Cooperative provides electrical service to the counties of Accomack and Northampton along Virginia’s Eastern Shore and to Smith Island in Somerset County, Md.A&N recently worked to improve the efficiency of power distribution to a small island community and marina on Tangier Island in the Chesapeake Bay. This improvement consisted of upgrading the existing distribution substation with a new 25 kV 2-bay box distribution structure. Earth Contact Products (ECP) collaborated with PowerServices, Inc. (PSI) to design and install a helical foundation support system as part of the substation upgrade. Feasibility EvaluationThroughout the design process, A&Nworked with its partners PSI (design) andT&D Solutions (installation) to identifycost-effective alternatives. Foundationsystems considered included cast-in-placereinforced concrete caissons, precastconcrete foundations, driven steel piles and helical piles. In evaluating all of theoptions, the greatest concern was gettingthe material onto the island, followedclosely by the availability of the equipmentto install the foundations. Clearly, cost,more specifically the installed cost, was asignificant consideration and decisionfactor throughout the process.There were several limiting factors that had to be considered during the design process, the most significant of which was that all of the material had to be barged to the site. With traditional reinforced concrete deep foundations in mind, the cost for installing these piles was projected to be nearly $2,000/cu yd ($262/cu m) of installed concrete. Given that approximately 5 to 6 cu yd (3.8 to 4.6 cu m) of concrete would be required for this structure, the cost was significantly high for this project. What’s more, because the components of the concrete mix would have to be barged and then hand mixed on site, there was concern regarding both the time required to complete the piles and the quality of the installed concrete. For the driven pile alternative, the availability, or lack thereof, of equipment and material cost resulted in a total cost estimate that was more expensive than that of the concrete piling alternative. The high material cost for the piles, which was more than double than the cost of concrete, was due to the number and size of piles needed to resist the overturning moment. Ultimately, the team selected the helical pile alternative. The decision to a use helical pile foundation system was based on many factors, not the least of which was the remote location of the project site and the difficulties associated with getting material, equipment and construction personnel to the project site."

Jan 1, 2017

By R. J. Arsenault

The yield drop that occurs in tantalum, Cu-AZ. and Ag-Al was investigated as a function of strain rate and at several temperatures. From the strain-rate dependence of the yield drop an activation volume was calculated and found to agree with that obtained from differential strain-mte tests. The temperature dependence of the yield drop can he explained in terms of the parameter temperature divided by activation volume. The yield drop is attributed to the rapid multiplication of dislocations during their motion. THE yield-point or yield-drop (upper yield stress minus the lower yield stress) phenomenon has been the subject of numerous investigations1-9 in both bcc and fcc metals. Also, there is no dearth of theoretical explanations10-20 to account for the yield-point phenomenon. The present explanations can be divided into two categories: the concept of dislocation locking and subsequent unlocking and the concept of multiplication of dislocations due to their motion. The Vottrell10,11mechanism of locking and unlocking, as applied to bcc metals, is the best known of the three proposed locking mechanisms. The two additional mechanisms, short-range order (SRO)7,16,17 and Suzuki-type locking,14,15 have been employed to account for the existence of yield points in fcc metals. The experimental evidence supporting the locking of dislocations, especially in bcc metals, is well-established. The dependence of the yield point on interstitial concentrations,&apos; the kinetics of strain aging,2 and the observations by electron-transmission microscopy18 are some of these experimental results. The number of experimental observations supporting dislocation locking in fcc metals is not as extensive as in bcc metals. The unlocking of dislocations, which actually is supposed to account for the yield drop, is by no means well-established by experimental results for either bcc or fcc metals. The similar temperature dependence6 of the yielding and plastic flow is one of the experimental factors that cannot be explained in terms of the unlocking of dislocations. The mechanism based on the rapid multiplication of dislocations has been proposed by several investigators. 18-20 Johnston and Gilman19 have proposed a detailed model of yielding, which was later employed by Hahn21 to predict quantitatively the yield drop in iron. This mechanism was discussed in a previous paper22 and several limitations were pointed out. In the same paper it was shown that an activation volume could be obtained from the strain-rate dependence of the yield drop and that a correlation existed between the activation volumes obtained from the yield-drop tests and from differen-

Jan 1, 1964

By Kubik K

The objective of this paper was to determine if recent advances in numerical electromagnetic wave propagation modelling techniques could be used to study the propagation of GPS signals over arbitrary terrain. Specifically the effects of diffraction and multipath were to be modelled accurately for propagation over arbitrary terrain surfaces defined by a digital terrain model. Ideally the model was to be in three dimensions and cover an area of a few square kilometres with a simulation height of a few hundred metres. Simulations were to run on current technology PC&apos;s with run times less than a few hours. A relatively new technique that involves a numerical solution to the Parabolic Equations can be used to solve for two-dimensional propagation over any type of terrain. The PE provides a direct solution of Maxwell&apos;s wave equations by approximating the Helmholtz scalar wave equation. This technique does not rely on the study of individual ray paths as used in the Geometrical Theory of Diffraction (GTD). It was decided to develop a two dimensional Parabolic Equation code, using the Fourier Split/Step method that allowed propagation over arbitrary terrain (; ; ). The model boundary conditions assumed that the satellite transmission was a plane wave, and that the lower boundary was a perfect reflector. Propagation simulations from the model accurately provide the amplitude and phase of the propagated plane wave at all points within the model domain. The PE model was used to study the effects of diffraction and multipath caused by various types of terrain commonly found in an open cut mining environment. The study of diffraction errors was relatively simple, because we are simply concerned with amplitude of the signal as it diffracts about an obstacle. If the amplitude is above the level receivable by a GPS receiver then the diffraction error can be obtained from the geometry of the terrain obstacle. The study of multipath is more complex, as the computed phase from the PE model is ambiguous and the presence of multipath can only be inferred. Thus the absolute magnitude of the nmltipath error is not currently determinable, though the results of some new work is shown here. This paper shows that diffraction effects can cause significant errors in range. It also shows the effects that multipath has on the received amplitude of the signal and the received phase of the signal. A discussion is made of further work that is presently underway that will allow the direct determination of the multipath error by comparing the ambiguous phase with a reference phase.

Jan 1, 1997

THE ore treated is almost pure copper pyrites (chalcopyrite) in a gangue of quartz and quartz-felsite. Very little free iron sulphide (pyrite) occurs, and at the time of the erection of the flotation plant the stopes in the oxidized zone had been almostentirely depleted. This zone only extends to a shallow depth, and, below the l00-ft. level, the sulphide for the most part is clean and bright but in the crushed and brecciated parts of the ore channel, where surface water has circulated freely, the gangue is decomposed and kaolinized, and the copper sulphide badly tarnished. This class of ore gave considerable trouble at the mill, but unfortunately, was very limited in quantity. A sample of rich ore assayed-Copper, 21.2 %; iron, 24:.3 %; silica, 28.9 %; sulphur, 25.1%.The concentration in the original mill was effected by handpicking, jigging, and tabling. A considerable portion of the copper mineral arrives at the surface in the form of large lumps of very pure quality, eminently suitable for sorting out by hand.The rich ore is tipped over a grizzly at the shaft bins; the oversize hand-picked, and the undersize bagged direct.

Jan 1, 1912

By J. A. Hudson

"The paper begins with a brief summary of Professor Müller’s formation of the ISRM and the contents of the previous six Müller lectures with their emphases on rock fractures. The geological origin of fractures is described via a deformational spectrum diagram and a matrix characterising the consequences of a sequence of superimposed deformational events. The different fracture frequencies encountered along lines in all directions through a fractured rock mass are explained. The value of computer modelling and simulation is demonstrated through an example of the effects of fracture zones on the distribution of the in situ stress field. The need to establish the validity of computer programs, i.e., that the modelling/simulation, does actually represent the rock reality, is discussed with reference to the work of the DECOVALEX project. Finally, examples are given of the effects of rock fractures on engineering design and construction, from pre-split blasting to caverns.INTRODUCTIONIt is a great honour to have been chosen as the recipient of the ISRM 7th Müller Award and I am grateful to the representatives of the International Society for Rock Mechanics (ISRM) National Groups who voted for me. In addition, I am especially pleased because my working life in rock mechanics and rock engineering has been devoted to understanding the geometry and mechanical properties of rock fractures and rock masses—which were the key subjects that Professor Müller promoted. In the ISRM 50th Anniversary Commemorative Book, Hudson and Lamas (2012), Professor Charles Fairhurst notes that on 24 May 1962, i.e., the day before the constitutional meeting of the ISRM took place in Salzburg, a reporter asked Professor Müller, “Do we know the strength of rock?”, to which Professor Müller replied, “For rock tested in the laboratory, yes. For a rock mass, no. This is what we need to determine. This is why we need an International Society for Rock Mechanics”. Also, in his Opening Address at the 1st ISRM Congress in Lisbon, Professor Müller, as the then ISRM President stated,“Many experts agree with me that discontinuity and anisotropy are the most characteristic properties of the material rock and that the properties of jointed media depend much more upon the fabrics bond of the unit rock block system than upon the rock material. Therefore any theoretical investigation of that material has to go its own ways, in the same way as the construction material of soils years ago suggested to soil mechanics its own methods, which differ greatly from the way of thinking of technical mechanics”."

Jan 1, 2015

By L. W. T. Weitzel

"This paper reviews the Falconbridge- SMRQ’s Raglan project in northern Quebec and the process that was used in developing its current long-term mine plan. Challenges were many and not only limited to the longevity of the project, numerous ore deposits (both underground and open pit), and a 40 km property strike length. As a result of its remote northern location, other factors such as progressive reclamation, leachable mine waste, water treatment, and waste management were also part of the plan. A combination of modern planning tools were used to formulate the plan including DataMine, Mine 2-4D, AutoMod Simulation, and an Excel-based financial spreadsheet to bring the total plan together. The focus of the paper is to show the complexity of modern mine planning and associated economic modelling of mine processes. IntroductionThe Raglan project is located 1660 km directly north of Quebec at the northern tip of the Quebec Peninsula in Nunavik. The main property is 40 km in length stretching from the Donaldson airport area at the eastern edge of the property to East Lake at the western edge. The Deception Bay port is 90 km north of the main complex/mill situated at Katinniq which lies approximately in the middle of the property (Fig. 1). The mine processes 1 000 000 tpy of ore from both open pit and underground sources. The mill is forecasted this year to produce more than 150 000 t of concentrate grading more than 18% nickel. All personnel and critical cargo are transported to the site via a company-leased 737 jet from Rouyn-Noranda where the main administration office is located. The majority of cargo is shipped to the site via Deception Bay from Quebec and on the return trip, nickel concentrate is shipped back. From Quebec, the nickel concentrate is sent by rail to the Falconbridge smelter in Sudbury and on the reverse rail haul, nickel matte from the smelter is sent to Norway via Quebec."

Jan 1, 2003