Search Documents

By H. A. Kortmann, K. Koch, B. M. Grover, O. P. Burghardt

Addition of lime, especially when treating a hematite feed, sometimes results in swelling and a severe loss in strength during reduction in the temperature range 900° to 1100°C and in grain disintegration in the temperature range 400° to 600°C in a weakly reducing atmosphere. Swelling and/or grain disintegration of pellets is often the reason for trouble in blast furnace operation, resulting in a decrease in the rate of smelting. Following a brief description of the test procedures employed (measurements of swelling, pressure-reduction-softening and grain disintegration), some results are given which were arrived at when testing pellets from industrial plants. Results of systematic tests are presented, where the effect of the quantity and quality of the gangue upon the behavior during reduction of pellets is illustrated. Varying amounts of quartz and limestone were added to a high-grade hematite ore and, then, pellets produced in a pot grate. The relationships of the behavior of the fired pellets during reduction are presented, among others, in the ternary system CaO-FeOn-SiOP. Finally, an attempt is made to explain the reasons for swelling, loss in strength, and grain disintegration.

Jan 1, 1974

By James J. Bailey

Percussive drills have been in commercial use for many decades. Until relatively recently there was little serious effort to analyze the stresses in such devices in any detail. Within the last few years such analyses have been developed and have been reported by a number of authors.1-4 We present here an investigation of the impact systems of a family of conventional down-hole drills with optimization the objective. We have assumed that maximum drilling speed was the quality most desired and that this was to be achieved within conventional practice. In fact the methods that are demonstrated in principle below can readily be adapted to other percussive devices, whether conventional or not, and to other constraints. SOME PERFORMANCE PARAMETERS FOR PERCUSSIVE DRILLS Consider a percussive drill with an air motor operating with the following parameters: p-supply air pressure a-effective piston area W-piston mass S-piston stroke If we consider a simple (constant pressure) cycle, the following relationships can be derived. The blow frequency [N~ pa lie WS 377]

Jan 1, 1968

By H. K. Shearer

The principal events in the oil history of south Arkansas, north Louisiana and Mississippi in 1930 have been: In Arkansas, very little activity, except for discovery of deep oil production at Urbana, and completion of the first oil well in Miller County. In Louisiana, continued development of the Zwolle area, bringing production up to about 10,000 bbl. per day; practically complete development of the Carterville oil-producing area; discovery and drilling of the rather disappointing Holly area, and discovery of Trinity gas production at Sugar Creek, Claiborne Parish and Rodessa, Caddo Parish. In Mississippi, discovery of the Jackson gas field, in Hinds and Rankin counties. Proration of oil runs was not put in effect in these areas during 1930, because the natural decline of the older fields brought production below the demands of local markets. The only effect of the oversupply and low price of oil was the curtailment of some drilling which might otherwise have been done. Drilling in Arkansas reached the lowest stage since the discovery of oil, with less than 100 completions. Louisiana showed some increase in drilling over 1928 and 1929, but almost half of the wells were drilled primarily for gas rather than oil. As no review on north Louisiana production has been prepared since 1927, and there was none on south Arkansas for 1928, the developments of the three years, 1928, 1929 and 1930 are here briefly discussed.

Jan 1, 1931

By William Fink

ALTHOUGH age-hardening in an aluminum-base alloy containing magnesium was observed by Alfred Wilm1 as early as 1911, it was not until 1919 that a theory of the mechanism of age-hardening was proposed. Merica, Waltenberg and Scott,2 studying the age-hardening character-istics of Duralumin at the National Bureau of Standards, came to the conclusion that age-hardening of this alloy is caused by the precipitation of CuAl2, which is less soluble at the aging temperature than at the solu¬tion heat-treating temperature. It was postulated that the initially precipitated particles were of fine colloidal dimensions but that they gradually grew in size. Maximum hardness was assumed to be attained when the particles reached a critical size. This theory was at first received skeptically, since it was a widely accepted view at that time that the solid solution state should represent the hardest state of an alloy. Shortly thereafter, Jeffries and Archer proposed their well-known "slip interference theory."3 They suggested that age-hardening was accomplished by the precipitated particles acting as keys interfering with slip along crystallographic glide planes. They showed that this mechanical theory led directly to the assumption that maximum harden-ing would be produced by particles of a critical size, which they suggested would have a diameter approximately 10 times that of the aluminum atom. This contribution amplified and explained so rationally the age-hardening theory of Merica, Waltenberg and Scott that wide accept-ance resulted.

Jan 1, 1939

By A. Boltax

The effect of cold work on the electrical and magnetic properties of solution-treated and aged Cu-Fe alloys was studied. The electrical resistivity of solution-treated and of aged Cu-1.7 wt pct Fe samples increased by up to 25 and 140 pct, respectively, follozcing a 55 pct reduction of area. The principle contributions to the increase of resistivity of the solution-treated and aged samfiles are examined. Measurements of the .saturation induction, coercive force, and stacking fault Probability are also reported. 1 HIS paper is the second in a series which examine the behavior of the electrical and magnetic prop- erties of Cu-Fe alloys. The first paper1 was primarily concerned with the effects of thermal treatment whereas the present paper examines the effects of cold work on solution-treated and aged Cu-Fe alloys. The effects of cold work on the transformation of the coherent fcc iron precipitate to the ferromagnetic form2 and the coercive force and remanence3 have already been described, but the unusually large increases in resistivity (up to 220 pct) which occlir with cold work have not been reported previously. EXPERIMENTAL METHOD The methods used for alloy preparation, heat treatment, and electrical and magnetic measurements are described elsewhere.1 The specimens, initially 4-in. lengths of 0.0625-in. diam wire, were cold worked by swaging in hardened steel dies. Following each reduction, the samples were etched lightly in hydrochloric acid to remove surface con-

Jan 1, 1962

By Dennis A. Clark, Brent Larsson

Tunnelling today is a lot more than drilling and blasting. The developments in drilling and blasting technique have made it pos¬sible to save costs both by increasing the advance per round and optimizing the demands on the final contour. Increasing the hole depth by using longer feeds and bigger dril¬ling rigs make the drilling time shorter compared to the set up time. It is important that the deeper holes are followed up by using a suitable cut. The most common cut in Sweden today is a parallel hole cut with one or more large holes; with a diameter corresponding to the hole depth and wanted advance per round. It is often specified that smooth blasting is to be carried out with a specific drill hole spacing. It is extremely rare, however, for specifications to be issued concerning the alignment of the raw of holes closest to the contour holes. It is very easy to ruin the effect of smooth blasting altogether by firing the rest of the round carelessly with an excessively high charge distribution. The drilling and blasting of the contour holes and the line of holes closest to the contour holes is therefore an extremely important part of any underground work. Accuracy and care in connection with the drilling of contour holes is also extremely important since it is possible to reduce the amount of overbreak, the result being more rapid mucking out, smoother and more durable surfaces and also less consumption of concrete for lining purposes.

Jan 1, 1983

By Nick Barton

Simple methods for estimating the shear strength of rock joints and waste rock are reviewed. For the case of rock joints, the methods are based on a quantitative characterization of the joint roughness and the joint wall strength. Size-effects are found to reduce the peak strength of large joint samples to values below the ultimate or so-called "residual" values measured in the laboratory. Tilt tests and surface profiling on natural size blocks within the jointed rock mass are recommended for obtaining scale-free properties. The joint parameters obtained can be used to model complete strength-displacement-dilation behavior if this level of input is required. Large scale tilt tests can be performed with advantage on both rock joints and waste rock. The behavior of these two materials is surprisingly similar. Both are influenced by the size-effects on the compression strength of the rock, and both have similar log-linear relationships between effective normal stress and the peak drained friction angles. The resulting high values of friction near the toe or close to a slope face in either material can be misleading.

Jan 1, 1983

By James R. Jones

The concern for air pollution goes back centuries as will be seen from this quotation: "Strife and coal, it seems, have a hand-in-hand historical relationship. It was thought by some . . . in the Middle Ages that burning coal filled the air with dangerous poisons. So great was the concern that in 1306 King Edward I of England passed the first and unquestionably the harshest, air pollution legislation edict that history will record. His proclamation declared the use of coal an act punishable by death." As related to coal mining the air pollution problem is primarily that of its customer when using the fuel. Thus the major impact relates to markets for coal rather than the actual mining operation itself. In the vicinity of the coal mine the problem is principally related to fugitive dust from roads, transfer facilities, loading facilities, crushers. etc., and particulate matter (dust or fly ash) from thermal dryers and air cleaning tables. FUGITIVE DUST Most state air pollution regulatory agencies now have rules and regulations requiring control of fugitive dust. This refers to dust generated from normal processing operations. A typical air pollution control agency regulation reads as follows: "Fugitive Dust" "No person shall cause, suffer, allow, or permit any material to be handled, transported, or stored; or a building, its appurtenances, or a road to be used, constructed, altered, repaired, or demolished without taking reasonable precautions to prevent particulate matter from becom-

Jan 1, 1973

By J. J. Brown

Wilkes-Barre Meeting, Julie, runs., THE ore-hearth was the earliest type of furnace used in smelting Mississippi Valley lead-ores, which are very pure, and low in silver-content. The first smelters made no attempts to recover lead from the smoke; and since about 15 per cent. of the lead -in the charge escaped in this manner, early practice with the hearth was decidedly wasteful. At most of the large smelting-plants blast-furnaces with auxiliary roasters were substituted for the hearths long ago. But, upon the introduction of the Lewis and Bartlett bag-process for collecting fume, the ore-hearth was used by companies engaged in the manufacture -of pigments, simply on account of the large percentage of fume made by it. In fact, the extraction of lead was kept down by the use of hot blast and other devices. During recent years, however, several smelting companies have realized that the preliminary roasting of galena for the blast-furnace is not economical, and have, therefore, replaced the roasting-furnace with a modification. of the old Scotch hearth, in which a large percentage of the lead in a charge is recovered directly as pig-lead, while the remainder passes partly into fume and partly into slag low enough in sulphur to be charged into the blast-furnace without further treatment. The results obtained have proved so satisfactory, both As to recovery and operating-expense, that one eminent metallurgist has predicted the universal use of the ore-hearth on non-argentiferous ores. The-ore-hearth, thus employed as an adjunct to a blast-furnace plant, is rather a desulphurizer than a smelting-furnace proper,-the chief object being to make a blue slag suitable for the cupola-furnace. Hence, no special care is taken to obtain from it a large lead-extraction. * Head of Department of Ore Dressing and Metallurgy, Oklahoma School of Mines and Metallurgy, Wilburton, Okla.

May 1, 1911

By Norman Gerald

THE lack of a continuous operating balance in petroleum refining, which is analyzed in this paper, is by no means a feature solely of this division of the oil industry. Serious disequilibria of a capital as well as an operating nature exist both in the producing and marketing departments, while problems in the former and to some degree the latter are complicated by political involvements. Attention has previously been directed to the unstabilizing influence of present proration formulas in stimulating unnec-essary drilling.1 While equilibrium in petroleum refining operations has been fairly well maintained in the past decade, examination of departures may prove fruitful. Economic analysis is the application of time and motion study to the functioning of management, rather than labor. Properly applied it may reveal changes in policies that would increase the utility of the properties and facilities of the industry for stockholders, employees and the public, while contributing a stabilizing influence to the general economy. The study of economic equilibrium is essentially one of measurement and interpretation, requiring adequate data and the development of a tech-nique of analysis that employs statistical and mathematical methods as a supplement to the broad descriptive phase of economics. Economic equilibrium in petroleum refining is a dual concept. It embraces both the over-all balance between total storage and total demand for major products and the internal balance between the demands and inventories of the various products. The latter is the more complex of the two for it is concerned with proportionating the supplies of the several products stemming from the joint source to the demands for the individual products which are subject to wide variations. All the products are essentially nondurable goods, and they are used both by producers and consumers but in varying proportions. Motor fuel is very largely a consumer's good, while residual fuel oil is almost entirely a producer's good, the other products falling between these extremes. The peculiar-

Jan 1, 1939

By Alan Morris

BRASS rod for use in automatic screw machines is one of the major products of the brass mills. A large tonnage is consumed each year in the manufacture of an endless variety of finished articles and parts for assembly into other products. The machines that do this work have been developed to a high degree of efficiency, and their manufacturers are still striving for higher production speeds. This development has brought with it a demand for brass rod to meet the increasingly difficult machining conditions. This paper is a report of the results of tests undertaken in an effort to obtain a measure of the effects of such variables as lead content, microstructure and cold work on the machinability of brass rod. It is realized that the term "machinability" has never been well defined. Power, finish and tool life all should have a place in such a. definition. In practice it is sometimes found necessary to sacrifice some of these in order to obtain a rod that will not tend to throw up a burr, or will give a burr which is easily tumbled off. Again a specially stiff rod may be necessary because of long overhang from the chuck or a rod of special characteristics is needed to take a given broaching operation without chattering. It is only through an understanding of the effect of basic mill operations on the machinability of the rod that such problems as these may be solved most economically. It is hoped that this paper, together with the discussion it may evoke, will prove to be a basis for such an understanding.

Jan 1, 1932

By Pierre J. Goossens

The coastal Cordillera around the Panama basin is made up of a Cu-rich tholeiitic volcanic belt representing either immature, late Mesozoic, island arc, or oceanic ridge. The same belt is exposed (uplifted) along the western slope of the Cordillera Occidental of Ecuador and Colombia. Ni-lateritic, Cr-podiform, and Pt-(Au) placer deposits are formed there after or within ultramafic bodies of oceanic association. Younger calc-alkaline igneous activity provided the mechanism for porphyry copper and associated ore formation. This Cu (+Mo) mineralization occurs along a narrow belt exposed by the erosion of the volcanic cap. Ag-Pb-Zn(-Au) and Hg volcanogenic mineralizations occur within the calc-alkaline belt, but slightly eastward and only above the copper belt. To the east and in the Venezuelan Andes, Paleozoic and older sediments, volcanics, and metamorphics contain volcanogenic massive sulfide, Pb-Zn, Au, and Cu sedimentary and vein deposits, and sedimentary iron ore and phosphate. The Cenozoic Cu, Ni-Pt-Cr and a portion of Ag-Pb-Zn, Hg, and Au mineralizations occur within or just above the oceanic basement whereas the eastern- most Cenozoic Ag-Pb-Zn mineralizations occur within and above a pre-Cenozoic sialic basement. This continental crust is the northern extension of the Peru-Chilean Andes where no oceanic crust has been preserved, however. Cenozoic metallogeny and subduction relationships are unclear in the Northern Andes. Yet strong structural volcanogenic ore controls exists apparently due to deep strike-slip movement between two plates.

Jan 1, 1977

By Chase Palmer, Edson S. Bastin

While the reducing action of organic matter, of ferrous sulphate, and of hydrogen sulphide has frequently been invoked to account for the deposition of native gold and silver from ore-forming solutions, the high efficiency in this respect of certain of the metallic minerals which form the ore itself has not been suffciently recognized. If a little finely powdered chalcocite is placed in a test-tube arid 2 or 3 cc. of a dilute solution of gold chloride are poured over it, two or three shakes of the tube suffice to remove all the gold from the solution. The color of the solution changes from yellow to pale green, showing that copper is dissolved simultaneously with the precipitation of metallic gold. If a piece of chalcocite is hung in a dilute aqueous solution of silver sulphate (1/40 normal), a coating of silver begins immediately to form on the mineral, and within a few moments a beautiful silver tree has developed, similar to that formed when metallic zinc is immersed in a similar solution. When similar experiments are conducted with other sulphides and with certain arsenides and sulph-arsenides, especially those known to be commonly associated with native silver in ore deposits, it is found that these minerals differ greatly in their efficiency as precipitants, especially in their effect on silver solutions. The tests made with most of the minerals were qualitatipe only, but the reactions of a silver sulphate solution on chalcocite and niccolite were submitted to quantitative study to determine the nature of the reactions involved. Quantitative studies of the reactions with other minerals are now in progress

Jan 1, 1914

By M. J. Marcinkowski, R. M. Fisher

The flow stress-grain size relationship has been determined at room temperature in both a disordered and a fully ordered FeCo for plastic strains up to 30 pct. The results are in agreement with a Hall-Petch relation of the type given by Of =a,+kd-1/2 where of is the flour stress and a, increases mono-tonically with increasing strain to a maximum value which is much higher for the ordered than for the disordered alloy. The slope, k, is found to increase FOLLOWING the original work of Halll and petch relating the effect of grain size to the lower yield stress of iron and steel, it has been generally found that the yield stress oy.s. of polycrystalline metals with strain to a maximum and then decrease for both ordered and disordered alloys. However, k for the ordered alloy is in general higher than that for the disordered alloy and the critical strain for k max somewhat larger. All of these observations can be satisfactorily accounted for quantitatively and in some cases semiquantitatively by using a slip band-grain boundary intersection model, and by taking note of the fact that, in general, moss slip, while quite common in the disordered alloy, is extremely difficult in the ordered alloy. obeys a relation of the form oy.s.=a0+kd-1/2 [1] where a, and k are constants and d is the mean grain diameter. For convenience, and in accord with prevailing custom, Eq. [I] will be referred to simply as the Petch relation. Tjerkstra3 and Armstrong, Codd, Douthwaite, and petch4 showed that the flow stress af of iron or steel measured at strains of up to at least 20 pct also obeyed a relationship of the type given by Eq. (11. The latter investigators have also shown that Eq. [I] applies to fcc and hcp metals and alloys.

Jan 1, 1965

By D. L. Pentz

The use of "probability" methods in slope stability analysis has been practised by geotechnical engineers for some time. This paper questions whether the term probability has been properly used since in many cases the term is used in a classical statistical manner only to describe frequency distributions of data. This paper proposes a definition of the term probability which includes the engineers' subjective state of confidence for all critical parameters. Such parameters may include the slope stability model, undetected structural features, strength, groundwater pressure distribution, and geological framework. This process does not make a "better" analysis but it does force the geotechnical engineer to state his opinion in such a manner that others can understand and if necessary, criticize the assumptions. Further, this technique forces the question, "What impact would failure of a slope have on the production schedule or costs of a mine?" The level of risk taken in adopting a particular slope design strategy in a mine is not a question of what Factor of Safety should be selected but, rather, what trade-offs result from steeper slopes and the associated costs of failure. This paper also presents several simple probabilistic techniques which, though widely used in other fields have been all but ignored in geotechnical slope stability analyses. These include the use of stratified sampling to optimize Monte Carlo uncertainty approaches, and the use of simple functional approximations rather than complex stability models in probabilistic analysis. The author presents a case example of this technique and discusses the results in comparison with more traditional methods.

Jan 1, 1983

By WALTER B. JONES

PIG iron was first produced in Alabama in 1818 from limonite or brown ore and since then much of this ore has come from the so-called mineral district of northern Alabama, especially along the Cretaceous-Paleozoic contact. For many years the Russellville district in Franklin County, where the first blast furnace was erected, produced more than 100,000 tons of brown ore annually. Limonite has been reported at many places in the Coastal Plain region, where the formations are of Mesozoic and Cenozoic age, but these scattered deposits were never considered to be of much commercial importance. However, in the last three years a considerable quantity of this ore has been scraped up and shipped, particularly from the city of Greenville in Butler County.

Jan 1, 1938

By James Douglas

Though liberality is not supposed to be a prominent trait of the Scottish character, Canada owes to a Scotchman, Sir Wm. Macdonald, more than to any other of its people, not only wise ideas, but pecuniary help towards extending education: and another Scotchman, in New York, has sumptuously housed under one roof three branches of the engineering fraternity, of which we are one. Having thus created us members of the same family—for the metaphorical meaning of house and kinship is identical—Mr. Carnegie expresses more emphatically than even he could in words, that, by aff'ording facilities for closest intercourse, he invites the mechanical, electrical and mining engineers to participate in the freest interchange of idea and experience, and to correlate and combine the results of their studies and activities; and, being members of the same household, to banish reserve and secrecy. And now we, the members of the American Institute of Mining Engineers, meet as though we were at home in a neighboring country. For whether we meet in Canada, in England, or elsewhere, the Institute is always received as though no political or geographical divisions separated its members from those of congenial associations in the land of its host. In truth, the title which we have assumed claims for the sphere of our activities the whole American continent, regardless of such trifling details as boundary-lines. The fact that we meet to communicate each other's experience, to discuss our difficulties, and to seek each other's aid in solving the intricate problems that so often present themselves in the course of our professional life, is an acknowledgment of our individual helplessness; and therefore an argument for united effort. But no effort can be of any value if there is an underlying suspicion

Jan 1, 1908

By H. L. Hopkins, OHIO, L. W. Kemph, CLEVEL AND, E. V. Ivanso

A balanced system of internal stress is set up in any metallic structure by plastic deformation below the annealing temperature. The internaI stress induced by cold rolling or other fabricating processes is generally recognized and its magnitude is known to be, within certain limits, a function of the degree of cold deformation. The plastic deformation that may accompany rapid cooling from elevated temperatures may not materially change the form of the product. The internal stresses so induced are not, therefore, so evident and nonrecognition of their presence has at times led to engineering failures. The heat treatment of aluminum alloys is a relatively new art and little information is available regarding the magnitude of stresses induced during the commercial heat treatment of aluminum alloy products. As the industrial use of aluminum increases, it is inevitable that products of increasingly large volume will be required. It has become necessary in the present commercial utilization of aluminum to heat-treat castings and forgings weighing hundreds of pounds. One of the factors governing the magnitude of internal stresses arising from rapid cooling from elevated temperatures is that of the size of the structure being treated. Some of the other factors are: cooling rate, elastic properties of the alloy, thermal expansivity, thermal conductivity, and the presence or absence of phase changes. Practically all aluminum alloys have a high coefficient of thermal expansion and some are capable of developing relatively high elastic limits. On the other hand, all commercial aluminum alloys have relatively high thermal conductivities, no invariant phase changes, and the quenching temperatures are comparatively low. In the absence of invariant phase changes involving change in the type of crystallographic lattice, the fundamental basis for the development of internal stress

Jan 1, 1934

By J. A. Ede

THE object of the writer is to call attention to a rather unique aggregation of economic products distributed over a line of succeeding formations about 3 mi. long, to be seen within a few miles of La Salle, Ill. Fig. 1 is an ideal section of the stratification exposed and exploited along a distance of 3 1/5 mi. in a southwesterly direction from the quarry of the Utica Hydraulic Cement Co. located near the historic site of Kaskaskia village to the Oglesby, shaft at Oglesby. No attempt has been made to cover the whole field, special mention only being made (with the exception of two places) of the operations found along the course or parallel to the direction assumed in the ideal section. I have used Fig. 2, after J. H. Bent and De Witt Kelly, to locate the relation of the La Salle anticline to the coal mines of this district and to show the operation of No. 1 and 3 mines of the Illinois Zinc Co.

Jan 9, 1919

By R. W. Gurry, L. S. Darken

The solubility of cementite in austenite is computed by thermodynamic methods from the observed solubility of graphite. It is found that the solubility of cementite is greater than that of graphite in the entire austenite temperature range. Thus the prior discrepancy between this portion of the phase diagram and the observed metastability of cementite is partially resolved. FOR several years it has been apparent that a serious discrepancy exists in certain observations pertaining to the Fe-C system. Direct experimental data indicate: 1-That the curve representing the solubility of graphite in austenite'" crosses that for cementite4 at about 945°C as shown in Fig. 1. 2— That graphite and austenite saturated therewith are stable1 relative to cementite at all temperatures between the eutectoid, about 723°C, and the eutectic, about 1153°C. These observations are mutually incompatible in view of a well-known consequence of the second law of thermodynamics, namely, that the stable phase (presumably graphite at all temperatures) has a lower solubility than the metastable phase (presumably cementite). Hence either 1 or 2 above must be in error; either the measured solubility of graphite or of cementite, or the observation as to the stability of graphite, is in error. Our present purposes are: 1—To collate the available data on cementite and prepare a table of HO — HO° and of (Fa— HO°)/T. This tabular method seems the best and most convenient way to represent the heat and free energy of formation. 2—To determine whether the measured solubilities of cementite and graphite in austenite are in accord with the above table and the measured thermodynamic properties of austenite, in order to resolve, if possible, the existing paradox of these two solubilities. Enthalpy of Cementite The enthalpy of cementite at 273 °K, H279 — HOcem, was computed by integration of the low temperature heat capacity as measured by Seltz, McDonald, and Wells" 68" to 298 °K) and as given by the Debye functions recommended by them (0" to 68°K); the result is included in Table I. At higher temperature HCem — H,,"" is given by Kelley who used the data of Naeser7 (298" to 1037°K) and of Umino8,9 (273° to 1923°K). We have recalculated Hcem — H273 cem from the data of UminoO in the following way. In the equilibrated alloy at temperature the weight fraction of cementite Pct c -Pct cr is PctC -PctCr designated f(C), and the

Jan 1, 1952