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By Ira B. Joralemon

Neighboring mines, like men who live in the same environment, often assume similar characteristics. In the Bridge River area of the Lillooet district in central British Columbia there is a remarkable exception to this rule. The Pioneer mine has a simple fissure over 3000 ft. long, with no faults of more than a few feet and with only minor variations in width; the Bralorne mine, 2½ miles away at the other end of the same intrusion, has developed one of the most intricate vein and fault systems in the West. Hinged faults displace the main vein for hundreds of feet, and sometimes become valuable veins themselves. The width of ore varies in a few yards from 2 to 60 ft. Changes in grade of ore are just as abrupt. The rocks that follow the veins or are cut by them often grade into one another or into the ore with no definite contacts. Although the complexity of the structure has left many problems unsolved, the development has indicated a fascinating geological pattern. The Bralorne is in the eastern portion of the Coast Range, 55 miles by spectacular mountain road from the Pacific Great Eastern Railway station of Bridge River. The adit tunnel runs easterly from Cadwallader Creek, a tributary of Bridge River that flows into the Fraser River. Steep mountains rise from 3300 ft. elevation above sea level at the creek to peaks and ridges at 8000 to 9000 ft. altitude. The lower slopes are heavily wooded while above 5000 ft. bare rocks, glaciers and snow-fields extend far above timber line. See Fig. 1. Story of the Bralorne The Lorne claim, staked in 1897, was one of the earliest lode locations in the Bridge River district. At that time it was 70 miles by steep and treacherous trail from the railway. For the next 15 years Arthur Noel, Will Haylmore and other local prospectors mined the small, irregular, oxidized quartz veins to a maximum depth of 200 ft., and treated the ore in arrastres and later a five-stamp mill. The total production to 1912 was only $55,000. Noel and associates later formed the Lorne Amalgamated Mines Co., which they worked in a desultory way until 1925. Increasing sulfide and arsenide content in the veins

Jan 1, 1935

Neighboring mines, like men who live in the same environment, often assume similar characteristics. In the Bridge River area of the Lillooet district in central British Columbia there is a remarkable exception to this rule. The Pioneer mine has a simple fissure over 3000 ft. long, with no faults of more than a few feet and with only minor variations in width; the Bralorne mine, 2½ miles away at the other end of the same intrusion, has developed one of the most intricate vein and fault systems in the West. Hinged faults displace the main vein for hundreds of feet, and sometimes become valuable veins themselves. The width of ore varies in a few yards from 2 to 60 ft. Changes in grade of ore are just as abrupt. The rocks that follow the veins or are cut by them often grade into one another or into the ore with no definite contacts. Although the complexity of the structure has left many problems unsolved, the development has indicated a fascinating geological pattern. The Bralorne is in the eastern portion of the Coast Range, 55 miles by spectacular mountain road from the Pacific Great Eastern Railway station of Bridge River. The adit tunnel runs easterly from Cadwallader Creek, a tributary of Bridge River that flows into the Fraser River. Steep mountains rise from 3300 ft. elevation above sea level at the creek to peaks and ridges at 8000 to 9000 ft. altitude. The lower slopes are heavily wooded while above 5000 ft. bare rocks, glaciers and snow-fields extend far above timber line. See Fig. 1. Story of the Bralorne The Lorne claim, staked in 1897, was one of the earliest lode locations in the Bridge River district. At that time it was 70 miles by steep and treacherous trail from the railway. For the next 15 years Arthur Noel, Will Haylmore and other local prospectors mined the small, irregular, oxidized quartz veins to a maximum depth of 200 ft., and treated the ore in arrastres and later a five-stamp mill. The total production to 1912 was only $55,000. Noel and associates later formed the Lorne Amalgamated Mines Co., which they worked in a desultory way until 1925. Increasing sulfide and arsenide content in the veins

Jan 1, 1935

By Ira B. Joralemon

Neighboring mines, like men who live in the same environment, often assume similar characteristics. In the Bridge River area of the Lillooet district in central British Columbia there is a remarkable exception to this rule. The Pioneer mine has a simple fissure over 3000 ft. long, with no faults of more than a few feet and with only minor variations in width; the Bralorne mine, 2½ miles away at the other end of the same intrusion, has developed one of the most intricate vein and fault systems in the West. Hinged faults displace the main vein for hundreds of feet, and sometimes become valuable veins themselves. The width of ore varies in a few yards from 2 to 60 ft. Changes in grade of ore are just as abrupt. The rocks that follow the veins or are cut by them often grade into one another or into the ore with no definite contacts. Although the complexity of the structure has left many problems unsolved, the development has indicated a fascinating geological pattern. The Bralorne is in the eastern portion of the Coast Range, 55 miles by spectacular mountain road from the Pacific Great Eastern Railway station of Bridge River. The adit tunnel runs easterly from Cadwallader Creek, a tributary of Bridge River that flows into the Fraser River. Steep mountains rise from 3300 ft. elevation above sea level at the creek to peaks and ridges at 8000 to 9000 ft. altitude. The lower slopes are heavily wooded while above 5000 ft. bare rocks, glaciers and snow-fields extend far above timber line. See Fig. 1. Story of the Bralorne The Lorne claim, staked in 1897, was one of the earliest lode locations in the Bridge River district. At that time it was 70 miles by steep and treacherous trail from the railway. For the next 15 years Arthur Noel, Will Haylmore and other local prospectors mined the small, irregular, oxidized quartz veins to a maximum depth of 200 ft., and treated the ore in arrastres and later a five-stamp mill. The total production to 1912 was only $55,000. Noel and associates later formed the Lorne Amalgamated Mines Co., which they worked in a desultory way until 1925. Increasing sulfide and arsenide content in the veins

Jan 1, 1935

By Herbert Clark Hoover, Lou Henry Hoover

QUALITIES which the perfect miner should possess and the arguments which are urged for and against the arts of mining and metallurgy, as well as the people occupied in the industry, I have sufficiently discussed in the first Book. Now I have determined to give more ample information concerning the miners. In the first place, it is indispensable that they should worship God with reverence, and that they understand the matters of which I am going to speak, and that they take good care that each individual performs his duties efficiently and diligently. It is decreed by Divine Providence that those who know what they ought to do and then take care to do it properly, for the most part meet with good fortune in all they undertake; on the other hand, misfortune overtakes the indolent and those who are careless in their work. No person indeed can, without peat and sustained effort and labour, store in his mind the knowledge of every portion of the metallic arts which are involved in operating mines. If. a man has the means of paying the necessary expense, he hires as many men as he needs, and sends them to the various works. Thus formerly Sosias, the Thracian, sent into the silver mines a thousand slaves whom he had hired from the Athenian Nicias, the son of Niceratus1. But if a man cannot afford the expenditure he chooses of the various kinds of mining that work which he himself can most easily and efficiently do. Of these kinds, the two most important are the making prospect trenches and the washing of the sands of rivers, for out of these sands are often collected gold dust, or certain black stones from which tin is smelted, or even gems are sometimes found in them ; the trenching occasionally lays bare at the grass-roots veins which are found rich in metals. If therefore by skill or by luck, such sands or veins shall fall into his hands, he will be able to establish his fortune without expenditure, and from poverty rise to wealth. If on the contrary, his hopes are not realised, then he can desist from washing or digging. When anyone, in an endeavour to increase his fortune, meets the expenditure of a mine alone, it is of great importance that he should attend to his works and personally superintend everything that he has ordered to be done. For this reason, he should either have his dwelling at the mine,

Jan 1, 1950

By W. A. Wood, W. H. Reimann, K. R. Sargant

A study is made of the microstructural changes produced in armco and pure iron subjected to alternating torsion at amplitudes above and below the knee of the S/N curve. The aim was to identify the basic mechanisms of fatigue and to find why they should give rise to a sharp S/N knee in contrast to the type of S/N curve shown by fcc metals. It is found that the basic structural change above the knee in the iron is a pronounced cell formation in the grains, which determines irregular micro-cracks, and below the knee a dispersion of fine slip that determines a dispersed pore formation in the grains. Comparison of these changes with those in fcc metals similarly tested shows that they do not include an intermediate structural change, a concentrating of slip in narrow bands with associated slip-band cracking, that characterizes the fcc metals and accounts for their different type of S/N curve. RECENT conferences on basic mechanisms of fatigue emphasize that fatigue damage takes many forms: for example, cracking in slip bands (Thompson1), at grain boundaries and inclusions (Hempel'), at precipitation zones in alloys (Han-stock, Forsythe), or at surface notch-peak effects, both hypothetical (Mott, cottrel16) and observed (Wood). Evidently it is not easy to see in this diversity a basic mechanism. At the same time the contributions suggest that some reconciliation may be possible if distinctions are drawn between three phases of the fatigue process: initiation of damage at nuclei, distribution of these nuclei, and the final macroscopic crack system. In initiation, the relevant features appear to be that nuclei may appear early, at least by 1/100th to 1/1000th of the life of a test specimen; that they may do so at many independent centers, appearing according to some observationsa as pores or voids; and that they are not necessarily self-propagating, damage spreading rather by their multiplication. In distribution, the relevant feature appears to be that they form preferentially in zones where the microstructure becomes abnormally strained (as defined more closely below). Now in these two phases the basic fatigue process should be systematic. But, at the same time, the "abnormal strains" in particular set the stage for considerable diversity in the final phase of macroscopic cracking, for where zones of abnormal strain develop will depend on what kind of fatigue deformation is applied and what kind of prior processing the test material has had. On this view it seems desirable to know what in

Jan 1, 1964

By Terry E. Perkins, Len Marnewecke

Installation of a relatively simple, low-cost analog mill control system at Amax Lead Co. of Missouri's Buick concentrator has paid off handsomely. The system, which provides the capability of handling mill circuit upsets and ore changes while maintaining a desired particle size, is expected to generate annually a return on investment of several times its capital cost. In addition, the system stresses simplicity of field instrumentation and control strategy, leading to better operator acceptance and understanding, and its capital cost makes it very attractive for the specific installation when compared to more complex schemes using mass flow measurement and computers for calculating circulating load to infer particle size. This system has the advantage of utilizing an actual measurement for control, rather than a difficult-to-maintain inferred value.

Jan 2, 1978

By S. R. Balajee, I. Iwasaki

The interaction between British gum 9084 and dode-cylammonium chloride (DAC) at quartz and hematite surfaces was established from coadsorption studies and streaming potential measurements. The cationic DAC interacts with the somewhat anionic British gum 9084, leading to the formation and adsorption of a binary complex of DAC-British Gum 9084 at the interface. The parallel ability to depress quartz along with hematite as a result of the interaction between DAC and British gum appears to be the main reason for the ineffective depressant action of starches and starch derivatives in the cationic flotation of iron ores. Amines are not particularly selective collectors for the flotation' of siliceous gangue from iron ores and, therefore, a suitable iron oxide depressant is needed for a satisfactory separation. Various starches and their derivatives have been extensively tested with oxidized iron ores,'-3 and it has been empirically established that British gums and dextrins are preferable. However, for the flotation upgrading of magnetite-taconite concentrates from 8 or 8.5% Si O2 to about 5% Si 02, British gums, which have been used so successfully on oxidized iron ores, have been found to have no effect and oftentimes are actually deleterious.4 In previous articles,5-7, starches were shown by adsorption measurements, flotation tests, and floccula-tion tests to interact with calcium ions in solution, and it was thought that a study on the interaction between starches and dodecylammonium ions would be able to shed some light on the anomalous flotation behavior described above. In fact, starches are known to interact markedly with paraffin-chain-type surface active agents and, thereby, to precipitate the starch or inhibit the iodine-starch reaction.8 From X-ray diffraction studies and viscosity measurements, the formation of a helical complex between mylose and a surface active agent has been postulated.9 The interaction with other types of hydrophilic colloids, such as synthetic polymers and proteins, has also been investigated and is usually explained in terms of van der Waals' force interaction and/or ion-ion interaction. In the present investigation, the interaction of British gum and dode cylammonium chloride on quartz and hematite was studied by adsorption and streaming potential measurements in an attempt to establish the mutual adsorption behavior of British gum and dode-cylammonium chloride on mineral surfaces and to clarify the anomalous depressant activity of British gum in the cationic flotation of iron ores. All the measurements were carried out at a natural pH of near 7 because dodecylammonium chloride gives maximum selectivity of flotation separation at this pH2 and to avoid any third parameter in the system. EXPERIMENTAL MATERIALS AND METHODS Minerals: The quartz and hematite samples used for the adsorption tests were prepared as described in a previous paper,"J except that the specific surfaces of the samples were increased to 5,860 and 16,000 Sq cm per gm, respectively. For the streaming potential measurements, the 48165-mesh fractions screened out of the original samples were etched with hydrochloric acid, washed repeatedly with water, and stored under water in Pyrex bottles. Reagents:DodecyIammonium chloride (DAC) was prepared1 1 by bubbling dry hydrogen chloride gas through a benzene solution of high-purity dodecylamine supplied by Armour and Co. British gum 9084, received from Corn Products Co., was solubilized by first dispersing it in water to produce a 0.05% solution and then homogenizing it in a blender for 5 min. Distilled water was used in the preparation of the samples and the solutions and for all test work. Adsorption Measurements: The procedure for the adsorption density determinations was also the same as that described in the previous paper.1° The residual concentrations of the British gum and the DAC in the supernatant solution were analyzed colorimetrically by the phenol-sulf uric-acid and amine-picrate methods, respectively. The validity of the mine-picrate method for the colorimetric analysis of DAC in the presence of British gum and the analysis of British gum in presence of DAC were checked by establishing calibration curves between optical density and concentration. Streaming Potential Measurements: The cell assembly for the streaming potential measurements was similar to that described by Fuerstenau.' The streaming potential

Jan 1, 1970

By R. J. Colony

The failure, or disintegration, of concrete in structures, even when the cement, sand, and coarse aggregate used have passed satisfactorily all tests and inspections, is not uncommon. Such failures occur even when proper methods of mixing and placing have been used and where weather conditions were correct. In these cases, the origin of the trouble must be sought in the cement; therefore some additional mode of determining the quality of cement must be employed. The problem is to find a simple, usable, easily applied method that will supplement the standard tests. The solution of this problem involves a knowledge of the chemical composition of Portland cements, also of their constitution (or componental composition), as the behavior of a cement, when gaged, is dependent on the physical and chemical characters of the compounds of which it is composed, the proportions existing between them, and the fineness of grinding. It is likewise essential to know the character, behavior, and composition of the hydration products of Portland cement. The most promising method of attack makes use of chemical, mechanical, and petrographic methods. Chemical, by determining quantitatively not only the usual constituents, but the carbon dioxide and water. Mechanical, by determining the fineness with the air analyzer,' which separates into fractions of various grain dimensions all of that portion which in the ordinary sieve test passes the 200-mesh sieve and constitutes at least 75 per cent. of the total cement. These fractions may be further studied chemically and petrographically and micrometric measurements can be made of the grains. Petrographic, by the method of immersion, and by making thin sections from test pats of both neat cements and standard mortars. Normal Portland cement is composed of mechanical mixtures of definite chemical compounds having constant chemical and physical properties. In the order of their cementing qualities these are: Tri-

Jan 1, 1922

By Willis H. Carrier

Particular interest in the ventilation of deep mines, especially those in South Africa, has been created by a very complete system of cooling of the world's deepest mine, the Turf shaft of the Robinson Deep in Johannesburg. The writer visited this mine in January, 1936, and again in 1937. During these visits and subsequently, a considerable part of the theory involved in rock cooling in tunnels was developed and this has been checked by practical observations of the rates of rock cooling made within mines. The purpose of this paper is to set forth the method of attack of the mine problem. The cooling or air conditioning of mines by the use of mechanical refrigeration was not wholly newl-5 when the Robinson Deep installation was made. The first mine to be cooled was the Morro Velho mine, in Brazil. The first installation in this mine was put into operation in December 1920, the refrigerant being ammonia.5 The surface cooling gave considerable benefit but it proved inadequate as greater depths were reached, therefore in 1929 two centrifugal refrigerating machines were installed at the 6000-ft. level. These were used in conjunction with the surface cooling system to furnish additional cooling at the lower levels. This later installation used Carrene as a refrigerant. This nonflammable refrigerant, having a boiling point of 104" at sea level, insured reasonable safety, since all parts of the machine operated at subatmospheric pressure. Very favorable reports have been received on the effectiveness of this installation, but no recent data are available. An interesting feature of that plant is that the condenser water is cooled by spraying it into the exhaust air from the mine at the base of the ventilation upcast, which permits the water to be cooled within a few degrees of the wet-bulb temperature of the air entering the upcast, and the only water that has to be supplied for condensing purposes is that lost by evaporation, or about 0.5 per cent of the volume circulating through the condenser. This plan affords an ideal means for the removal of the heat load from the refrigerating system, and of course also from the mine itself. In many mines, however, especially those in South Africa, there is no

Jan 1, 1940

By Willis H. Carrier

Particular interest in the ventilation of deep mines, especially those in South Africa, has been created by a very complete system of cooling of the world's deepest mine, the Turf shaft of the Robinson Deep in Johannesburg. The writer visited this mine in January, 1936, and again in 1937. During these visits and subsequently, a considerable part of the theory involved in rock cooling in tunnels was developed and this has been checked by practical observations of the rates of rock cooling made within mines. The purpose of this paper is to set forth the method of attack of the mine problem. The cooling or air conditioning of mines by the use of mechanical refrigeration was not wholly newl-5 when the Robinson Deep installation was made. The first mine to be cooled was the Morro Velho mine, in Brazil. The first installation in this mine was put into operation in December 1920, the refrigerant being ammonia.5 The surface cooling gave considerable benefit but it proved inadequate as greater depths were reached, therefore in 1929 two centrifugal refrigerating machines were installed at the 6000-ft. level. These were used in conjunction with the surface cooling system to furnish additional cooling at the lower levels. This later installation used Carrene as a refrigerant. This nonflammable refrigerant, having a boiling point of 104" at sea level, insured reasonable safety, since all parts of the machine operated at subatmospheric pressure. Very favorable reports have been received on the effectiveness of this installation, but no recent data are available. An interesting feature of that plant is that the condenser water is cooled by spraying it into the exhaust air from the mine at the base of the ventilation upcast, which permits the water to be cooled within a few degrees of the wet-bulb temperature of the air entering the upcast, and the only water that has to be supplied for condensing purposes is that lost by evaporation, or about 0.5 per cent of the volume circulating through the condenser. This plan affords an ideal means for the removal of the heat load from the refrigerating system, and of course also from the mine itself. In many mines, however, especially those in South Africa, there is no

Jan 1, 1940

By M. C. Udy, P. C. Rosenthal

The use of minute boron additions to steel has been given considerable attention in recent years. Comparisons made between boron-free and boron-containing heats of otherwise identical analysis have indicated, beyond a doubt, the potent effect of boron for increasing hardenability. The actual hardenability increase has been expressed as a multiplying factor, or in terms of the percentage of other alloying elements boron might replace. The present study presents the results of a systematic survey of the use of boron as an addition to two types of alloyed steels and as a replacement for various percentages of molybdenum in these steels. Both cast and wrought steels of the two basic compositions were prepared. Molybdenum, because of its scarcity at the time the investigation was started, was selected as the element to be replaced by boron. Attention was also given to the effects of boron on other properties of the steels, particularly their notched-bar toughness, to investigate other advantages or limitations of this element as an alloy addition. Experimental Work Steels Investigated The two basic compositions used in this survey of boron as a replacement for molybdenum are given in Table I. The cast steels were higher than the wrought steels in silicon content to improve the casting quality. Table i.—Nominal Composition of the Two Base Alloy Steels composition. Per Cent. steel Mn Si Ni Cr Xi-Cr-Mo Wrought 0.28-0.70-0.15-o.45—o.45-0.32 0.90 0.25 0.55 0.55 Cast 0.28-0.70-0.35-0.45-o.45- 0.32 0.90 0.45 0.55 0.55 hln-&lo Wrought 0.28-I .go-o.0.15-0.32 1.70 0.15 Cast o. 28- I.40- 0.35- 0.31 1.70 0.45 a Sulphur was 0.040 per cent maximum and phosphorus 0.030 per cent maximum. Each of these base steels, both cast and wrought, was made with molybdenum contents of o, 0.10, 0.20, 0.30, or 0.40 per cent, the total comprising 20 steels. In addition, each of these 20 compositions was prepared with boron additions in amounts of o.oo15, 0.003, and 0.006 per cent as ferroboron; and in amounts of 0.002 and 0.005 per cent as two commercial intensifier alloys, designated alloys A and B. The boron-treated steels totaled 100, and the entire series 120. Test Procedure Each steel was melted as an individual heat in a 50-lb., magnesia-lined induction furnace. Ingot iron scrap or mixtures of ingot iron and steel. scrap were used for melting stock. Deoxidation was carried out in the furnace with 0.10 per cent aluminum. The aluminum addition was

Jan 1, 1948

By M. C. Udy, P. C. Rosenthal

The use of minute boron additions to steel has been given considerable attention in recent years. Comparisons made between boron-free and boron-containing heats of otherwise identical analysis have indicated, beyond a doubt, the potent effect of boron for increasing hardenability. The actual hardenability increase has been expressed as a multiplying factor, or in terms of the percentage of other alloying elements boron might replace. The present study presents the results of a systematic survey of the use of boron as an addition to two types of alloyed steels and as a replacement for various percentages of molybdenum in these steels. Both cast and wrought steels of the two basic compositions were prepared. Molybdenum, because of its scarcity at the time the investigation was started, was selected as the element to be replaced by boron. Attention was also given to the effects of boron on other properties of the steels, particularly their notched-bar toughness, to investigate other advantages or limitations of this element as an alloy addition. Experimental Work Steels Investigated The two basic compositions used in this survey of boron as a replacement for molybdenum are given in Table I. The cast steels were higher than the wrought steels in silicon content to improve the casting quality. Table i.—Nominal Composition of the Two Base Alloy Steels composition. Per Cent. steel Mn Si Ni Cr Xi-Cr-Mo Wrought 0.28-0.70-0.15-o.45—o.45-0.32 0.90 0.25 0.55 0.55 Cast 0.28-0.70-0.35-0.45-o.45- 0.32 0.90 0.45 0.55 0.55 hln-&lo Wrought 0.28-I .go-o.0.15-0.32 1.70 0.15 Cast o. 28- I.40- 0.35- 0.31 1.70 0.45 a Sulphur was 0.040 per cent maximum and phosphorus 0.030 per cent maximum. Each of these base steels, both cast and wrought, was made with molybdenum contents of o, 0.10, 0.20, 0.30, or 0.40 per cent, the total comprising 20 steels. In addition, each of these 20 compositions was prepared with boron additions in amounts of o.oo15, 0.003, and 0.006 per cent as ferroboron; and in amounts of 0.002 and 0.005 per cent as two commercial intensifier alloys, designated alloys A and B. The boron-treated steels totaled 100, and the entire series 120. Test Procedure Each steel was melted as an individual heat in a 50-lb., magnesia-lined induction furnace. Ingot iron scrap or mixtures of ingot iron and steel. scrap were used for melting stock. Deoxidation was carried out in the furnace with 0.10 per cent aluminum. The aluminum addition was

Jan 1, 1948

By Jack Haptonstall

INTRODUCTION The mines of western central Mexico historically contributed a profusion of gold and silver for the treasury of Spain and later provided sources for financing the Mexican War for Independence and the Mexican Revolution. The western coastal and barranca (cliff) tribes were hunters and extremely hostile, and the Spaniards were not able to penetrate many of the rich districts of their rugged homeland until the mid-1700's. This was more than 200 years after Cortez began the Inquisition by defeating the Aztecs and their allies in a decisive battle in the great city of Tenochtitlan (present day Mexico City). The Spaniards had a voracious appetite for silver and gold, and it was inevitable that they would finally subdue the natives and commence mining activities. Described in this paper are some of the precious metal mining activities in the southern half of the State of Sinaloa and the western half of the State of Durango (Figure l), and specifically those mining activities in the area controlled by the company with which the author was associated for 14 years, Minas de San Luis, S. A. de C. V., the parent company of which is now Industrias Luis Min, S. A. GENERAL DESCRIPTION Geography, Logistics and Climate The most spectacular of the physiographic provinces, the western Sierra Madre Occidental is the cliff or "barranca" province, the

Jan 1, 1983

By C. P. McCormack

The Cuyuna manganiferous iron ores can be a principal source of manganese for the iron and steel industry in the United States, provided metallurgical methods as a whole are adjusted so as to use run-of-mine ore. The use of manganese in steelmaking is growing. Increasing amounts of impurities in raw materials call for more manganese, a constant cheap supply of which is wanted. There are few deposits of ore in the United States carrying over 35 per cent. manganese that can be mined and marketed at a profit in normal times. We are largely dependent on foreign ores. The small domestic deposits should rightly be held in reserve for an emergency, such as a war, when importation might cease. Even the production from lean ores, concentrated it may be, might not carry us through a protracted stringency. The Cuyuna district is, therefore, during normal times capable of supplying a large total of manganese. The ores are iron ores containing 5 to 25 per cent. of manganese with the inverse range of 52 to 28 per cent, of iron. The manganese costs no more per unit in the ore than the iron, because cost of mining, largely by open-pit methods, is not affected by the manganese content. The manganese units should, perhaps, command a higher price, but as their value is contingent on metallurgical practice, a higher price may be justified only when a shortage in manganese occurs. Manganiferous iron ores can never entirely supplant straight manganese ores though methods are employed that will permit them to do so partly. For the manufacture of ferromanganese, ores carrying above 42 per cent. manganese are needed. Ores with manganese running between 20 and 42 per cent. are used for making spiegeleisen. But established practice in certain plants, based on the admixture of manganiferous iron ores to straight iron ores has greatly lessened the consumption of high-priced, scarce, manganese alloys with good results. The substitution of manganiferous ores for ferro and spiegel affects the manufacture of basic iron and its conversion into basic open-hearth

Jan 1, 1925

INTRODUCTION In the preceding chapters we have discussed the various elements of mineral economic analysis, their interrelationships, and the most accepted and advanced techniques by which these elements are manipulated to provide the decision maker quantitative measurements for judging alternate investment opportunities. Regardless of how carefully the economic evaluation is made, and how comprehensive the study of economic parameters has been, uncertainty still remains a significant factor in the outcome of the analysis. The investor or money manager is acutely aware of the uncertainty factor. Many of the economic parameters are functions of economic forecasts and value estimates that can- not be known with any degree of certainty. The postulated DCF-ROR is based upon certain estimates representing "best guess" values, and a single point parameter DCF-ROR analysis represents a combination of "best guesses." The wise decision maker looks at such an analysis and asks the "what if" questions. What if the production cost is 10% higher than the estimate? What if there is an overrun in construction costs? What if the mineral price falls lower than expected? What will be the effect of a higher royalty rate? Many more such questions may arise in trying to assess the total risk involved in funding a mineral project. Prior to the advent of the computer it was difficult to answer all such anticipated questions because of the many laborious calculations involved. Now, with the aid of the computer, most of these questions can be answered by the analyst at the same time the original computations are made by using the process of sensitivity analysis. Sensitivity analysis shows the effect of critical parameter changes upon the DCF-ROR or other profitability measure. When probability of occurrence can be associated with the various parameter value levels, sensitivity analysis becomes probabilistic analysis, and the risk factor can be quantitized in terms of total probability. SENSITIVITY ANALYSIS The determination of the sensitivity of the profitability index (usually the DCF-ROR) to changes in the various economic parameters, taking them one at a time, is called sensitivity analysis. The analysis may be performed for any number of parameters involved in the DCF-ROR computation. Generally, in mineral evaluations the most sensitive and most tested parameters are: the metal or mineral price, the operating cost, the annual production grade, and the initial capital invest-

Jan 1, 1980

By F. C. Hull

The grain size of a metal or alloy is one of the most important factors determining its properties. In steels, for example, grain size affects hardenability, toughness and machinability; in brasses, grain size is related to hardness and deep-drawing quality. In the field of heat-resistant alloys, grain size has a marked effect on ductility, creep and endurance strength. In order to determine these effects, as well as to control the properties of materials, many accurate and rapid measurements of grain size must be made. This paper presents a new and improved method for the estimation of grain size. Usual Methods OF EvaluatiNg Grain Size A frequetly used method of estimating grain size is that of comparing the image of a polished and etched specimen on the ground-glass screen of a metallographic microscope with standard grain-size charts. Several types of standards are available for use with different classes of microstructures. Geometric Grids.—The Metals Handbook' has a series of hexagonal grids ranging in size from ASTM No. I to 8. Idealized Grain Networks.—Idealized grain.boundary networks for ASTM grain sizes I to 8 are included in the American Society for Testing Materials Tentative Standard E 19 - 39 T, standard Micrographs & Metals Handbook and ASTM Tentative Standard E19-3gT contain micrographs of hypo-eutectoid and hypereutectoid steels ranging in grain size from No. I to 8. The grain size of annealed brass (diameter of the average grain in millimeters) is obtained by comparison with 10 micrographs of varying. grain size in ASTM Tentative Standard E 2-39 T. A handicap to accurate evaluation of grain size by this method is the fact that it is difficult to compare photographs in a dimly lighted room with the image on the ground-glass screen, or, if the general illumination is increased so that the printed standards may be clearly seen, the contrast of the image of the unknown is decreased. It is easier to estimate grain size by comparing a micrograph of the unknown with the grain-size standards. However, photographing every specimen on which the grain size is desired is too costly in time and materials to be practicable. For hardened steels, the Shepherd or Jernkontoret fracture grain-size standards are very accurate and useful, but this method obviously cannot be applied to ductile alloys such as brass, stainless steels and austenitic heat-resistant alloys. Jeffries' method for grain-size measurements consists of counting the number

Jan 1, 1948

By F. C. Hull

The grain size of a metal or alloy is one of the most important factors determining its properties. In steels, for example, grain size affects hardenability, toughness and machinability; in brasses, grain size is related to hardness and deep-drawing quality. In the field of heat-resistant alloys, grain size has a marked effect on ductility, creep and endurance strength. In order to determine these effects, as well as to control the properties of materials, many accurate and rapid measurements of grain size must be made. This paper presents a new and improved method for the estimation of grain size. Usual Methods OF EvaluatiNg Grain Size A frequetly used method of estimating grain size is that of comparing the image of a polished and etched specimen on the ground-glass screen of a metallographic microscope with standard grain-size charts. Several types of standards are available for use with different classes of microstructures. Geometric Grids.—The Metals Handbook' has a series of hexagonal grids ranging in size from ASTM No. I to 8. Idealized Grain Networks.—Idealized grain.boundary networks for ASTM grain sizes I to 8 are included in the American Society for Testing Materials Tentative Standard E 19 - 39 T, standard Micrographs & Metals Handbook and ASTM Tentative Standard E19-3gT contain micrographs of hypo-eutectoid and hypereutectoid steels ranging in grain size from No. I to 8. The grain size of annealed brass (diameter of the average grain in millimeters) is obtained by comparison with 10 micrographs of varying. grain size in ASTM Tentative Standard E 2-39 T. A handicap to accurate evaluation of grain size by this method is the fact that it is difficult to compare photographs in a dimly lighted room with the image on the ground-glass screen, or, if the general illumination is increased so that the printed standards may be clearly seen, the contrast of the image of the unknown is decreased. It is easier to estimate grain size by comparing a micrograph of the unknown with the grain-size standards. However, photographing every specimen on which the grain size is desired is too costly in time and materials to be practicable. For hardened steels, the Shepherd or Jernkontoret fracture grain-size standards are very accurate and useful, but this method obviously cannot be applied to ductile alloys such as brass, stainless steels and austenitic heat-resistant alloys. Jeffries' method for grain-size measurements consists of counting the number

Jan 1, 1948

By J. Gurland

The effects of variations of carbon content on the constitution and properties of sintered WC-Co alloys were studied. The grain growth of tungsten carbide during sintering was measured and it was shown that it takes place mainly by solution and reprecipitation of the carbide in and from the binder at the sintering temperature. It was found that the decomposition of W3C03C by carburization during sintering is responsible for the formation of very large grains. THE properties of sintered WC-Co alloys are critically dependent upon their final composition and structure. Slight changes of cobalt and carbon contents and small variations of grain size result in marked changes of mechanical properties and performance of products. Previous investigators have studied the microstructure as a function of composition' and have dealt with the influence of cobalt upon properties.' The present work is concerned with the effect of carbon content upon constitution, microstructure, and grain growth during sintering, as well as upon the physical properties of sintered compacts. Phase Boundaries at the Sintering Temperature The WC-Co section through the ternary diagram W-Co-C has been studied by Wyman and Kelley,' Takeda,V andford and Trent," and Rautala and Norton." Two phases, namely WC and a cobalt-rich solid solution (P), appear in the sintered structure if the carbon composition corresponds very nearly to the theoretical carbon content of WC (6.12 pct C). But small deviations from the ideal carbon content will bring about the occurrence of either graphite or the double carbide W,Co3C (7) . The 7 phase was long believed to be metastable, this conclusion being based mainly on the work of Takeda. More recent studies have shown that it is a stable phase of the ternary system,"5 but the actual phase boundaries have not been established and there has been some discussion as to whether or not the 7 phase occurs at some stage of sintering in the fully carburized alloys." In view of this uncertainty it was thought advisable to undertake an investigation of the phases present during the sintering of WC-Co alloys. Commercially available tungsten, cobalt, and carbon powders were used in the present study. A typical analysis of impurities in a sintered compact is reported in Table I. The desired carbon compositions were attained by varying the amount of carbon added to the tungsten during carburization and controlling the composition during sintering by packing the compacts into beds of mixed alundum-carbon powders of suitably selected ratios. The alloys were sintered in a hydrogen tube furnace at 1400°C, then brought to equilibrium at the temperature under investigation and quenched in water. The high temperature phases were identified by metallographic and X-ray diffraction techniques. The samples were etched with a 10 pct solution of alkaline potassium ferricyanide. The phase boundaries, established by metallo-graphic examination, are shown in Fig. 1, which is a vertical section through the ternary diagram at 16 pct Co. The temperatures of the invariant planes, at 1298" and 1357°C were established by Rautala and Norton. The vertical section shows that the three-phase field, WC + 7 + L, extends into the two-phase field, WC + L, but does not include the stoichiometric composition of WC. In practice this means that the 7

Jan 1, 1955

By Bernhard Blumenthal

A melting process was developed by which high purity electrolytic uranium crystals can be converted into sound ingots without serious contamination. Careful preparation of the crystals, melting in a high vacuum, and directional solidification led to a metal of better than 99.993 wt pct purity. The metallographic examination showed a substantially clean metal with only residual amounts of a second phase which responded to heat treatment. The density of high purity uranium is 19.05 g per cu cm. FOR the study of the fundamental properties of uranium and its alloys, a base metal of high purity is needed, and an investigation was started at Argonne several years ago to examine various methods of preparing high purity uranium. Early success was achieved by the fused salt electrolysis process in preparing high purity metal in crystal form,' and the problem became that of melting the crystals into ingots without contamination. The electrolytic crystals contained a few ppm of heavy metals, less than 15 ppm C, and large quantities of potassium and lithium in the form of trapped fused salt electrolyte. On melting in vacuo in magnesia or urania crucibles, the metal picked up considerable quantities of carbon and some iron, copper, and silicon but lost most of the potassium and lithium. It was not metallographically clean, and much research work was necessary to determine the optimum melting conditions for minimum contamination. This work has resulted in the development of a melting procedure by which sound ingots can be prepared with only a limited contamination by carbon. In the section entitled "Melting of the Electrolytic Metal," the equipment and processes that have been developed for melting the electrolytic crystals are described in detail. The "Metallography" section is devoted to the metallography of high purity uranium, and the section "Density of High Purity Uranium" contains the first property measurement on high purity uranium—a density determination. Melting of the Electrolytic Metal Apparatus—Melting and Vacuum Equipment: Uranium may be melted in either resistance or induction-type electric furnaces. Resistance heating was found to be preferable to induction heating for melting down the electrolytic crystals, for several reasons: Although induction heating permits fast heating, this advantage cannot be utilized when crucibles with limited thermal shock resistance are used. Temperature control of induction-heated melts is poor, and the stirring effect increases the rate of contamination of the melt from the crucible, slag, or the furnace atmosphere; liquation and controlled solidification are difficult to carry out. Because of these objections, resistance heating was chosen. A 10 kw Globar resistance furnace of low heat capacity permitted uniform heating of a uranium charge to its melting point in 45 min. The furnace was insulated with a removable aluminum shield so that, after melting and removal of the shield, the furnace could be quickly cooled to room temperature. The furnace was equipped with an apparatus for directional solidification; see Fig. la. The crucible was suspended in the center of the furnace; and when the melting was complete, the crucible was slowly lowered into the cold end of the furnace tube. Solidification took place upward from the bottom; and when the rate of lowering was small, a sound ingot free from sink holes and shrinkage cavities was produced. To remove the large quantities of gas contained in the electrolytic crystals, melting in a high vacuum is mandatory. While, from the standpoint of contamination, melting in a highly purified argon atmosphere appeared feasible, lithium and potassium removal proved less efficient under such conditions. Also, a vacuum-melted ingot has a cleaner surface than one melted in an inert atmosphere. The vacuum system must be of very high pumping speed and leak tight so that a vacuum of less than 2x10-7 mm Hg is attainable when the system is pumped down cold. The system must have a high pumping speed, so that the pressure maximum which may rise to 1x10-4 mm during heating can be quickly reduced

Jan 1, 1956

By E. P. Mathewson

W. W. (Pop) Adams' contribution is short and to the point. "I went to Pueblo about March, 1881, and started working for the Pueblo Smelting & Refining Co. in the sampling room, going from there to the assay and chemical departments, and ending in charge of the lead refinery on the night shift. I was there about two years, returning to California in 1883. The plant was under the management of Mather and Geist, plus Charley Ballard; Herman Schlapp was the metallurgist. Herman Schlapp's name remains prominently in my recollection of Pueblo for his never-failing kindness and charity to the young men who were trying to learn the Pb. game. John Allen, Walter Koehler, George Westcott, Charley Molson, and Alfred de Ropp were there with me. Schlapp and Koehler I have never seen since I left Pueblo; the others I have met often. , Alfred de Ropp I have often met-here, as he was manager of the Selby Smelting & Lead Co. of San Francisco, for years. 'He tells me that I gave him the rudiments. of American profanity at Pueblo; an apt pupil, for since then, by his own efforts, he has added largely to his vocabulary..

Jan 12, 1923