Search Documents

By Ronald W. Utley

INTRODUCTION The ''Do's and Don'ts" of installing equipment in a comminution circuit begin during the study stage of a proposed project, continue through preliminary engineering, detail engineering, procurement, the actual placement of equipment at the job site, and end with turnover to the owner. Equipment supplied for a modern comminution circuit will be high quality, rugged machinery designed according to appropriate manufacturing standards for long hours of trouble-free service. However, certain precautions and procedures must be observed in plant design and layout, equipment handling, installing and servicing in order to obtain optimum performance. This chapter contains general installation "DO'S and Don'ts" for the major equipment in the circuit. •Primary Gyratory Crushers •Rock Breakers (Hammer) •Belt Conveyors •Apron Feeders •Weigh Belt Scales •Secondary Crushers •Vibrating Screens •Grinding Mills •Mill Liners •Open Gear Sets •Speed Reducers •Electric Motors •Cyclones •Slurry Pumps Some questions will not be covered in this chapter, or may not be applicable to the actual equipment purchased, as requirements do vary from manufacturer to manufacturer. Additional specific information can be obtained by contacting the manufacturer's local representative or the factory. All inquiries should be accompanied by the following information: •Unit size and type of equipment •Manufacturer's shop order number (after order placement) •Serial number (after manufacture) DO'S 8 DON'TS FOR INSTALLATION OF ALL COMMINUTION CIRCUIT EQUIPMENT Installation By Design DO obtain tables of weights and clearances from manufacturer. DO obtain WR2 forces from manufacturer to determine that the foundation is adequate. DO determine compression strength of foundation soil and/or rock. DO obtain manufacturer's recommended typical foundation drawings. If substantial alteration to manufacturer's drawings is required, check with the manufacturer before proceeding.

Jan 1, 1982

By G. E. Goodspeed

THE Cornucopia gold quartz veins form a parallel vein system traversing metamorphic and granodioritic rocks. Field and petrographic evidence suggests that metasomatism has played an important role both in the emplacement of the granodiorite and in the formation of the veins. Structurally the veins appear to be related to the major tectonic features of the Wallowa Mountains and to be narrow shear zones rather than filled fissures. Petrographic studies indicate a complex history of formation starting from initial alteration along fractures or joints followed by recurrent fracturing and a quartz-forming stage, and closing with continued shearing and microbrecciation, which permitted the upward percolation of the later ore- forming solutions. The precipitation of ore minerals from these solutions formed ore shoots. Postmineral effects include the injection of Tertiary basaltic dikes, a slight amount of cross faulting, and some movement along the planes of the veins as well as oxidation.

Jan 1, 1939

By Waldemar Lindgren

Jan 1, 1905

By C. E. Abbott

The Birmingham district, Alabama, is distinctive in the proximity to one another of its deposits of iron ore, coal and flux. These three basic requisites for the making of iron and steel are found within a radius of 10 miles. Both dolomite and limestone are produced, the former for blast-furnace flux and the latter for basic open-hearth operations. The Tennessee Coal, Iron and Railroad Co., a subsidiary of the United States Steel Corporation, operates a limestone mine at Muscoda, near Bessemer, 12 miles southwest of Birmingham, served by its own railroad transportation system. The mine has a capacity of 130 tons per hour. Average analyses of a recent month's production arc as follows: Fe²zO³ SiO² Al²O³ CaCO³ MgCO³ Lump, percent............................. 0.51 0.22 98.63 0.14 Crushed and washed, per cent,................ 0.70 0.26 98.36 0.18 Lump stone, 2 1/2 to 755 in., is used in open-hearth operations at Fairfield Steel Works. Fine crushed and washed stone, 1% to 0.063 in., is calcined at the lime-burning plant and used for lime charges at the Ensley open hearths. Geology The district's deposits of hematite ore occur in the Clinton formation, and the limestone beds mined are stratigraphically 330 ft. above the ore beds worked. A cross section on the center line of the mine is shown in Fig. 1. This limestone formation, 130 ft. thick, is in the Warsaw horizon of the Lower Mississippian. It lies above 100 ft. of Fort Payne chert, which is immediately above the Clinton formation, and is composcd of layers of chert and cherty limestone, approximately 50 per cent of the material being pure chert. The chert is extremely hard, and the cost of driving raises through it is very high. Both iron ore and limestone deposits lie on the southwest limb of the Jones Valley anticline, the formations dipping from 15' to 32' to the southeast. The iron-ore seam outcrops along the crest of Red Mountain, a ridge with northeast-southwest trend rising 200 to 300 ft. above Jones and Shades valleys at the

Jan 1, 1938

By C. E. Abbott

The Birmingham district, Alabama, is distinctive in the proximity to one another of its deposits of iron ore, coal and flux. These three basic requisites for the making of iron and steel are found within a radius of 10 miles. Both dolomite and limestone are produced, the former for blast-furnace flux and the latter for basic open-hearth operations. The Tennessee Coal, Iron and Railroad Co., a subsidiary of the United States Steel Corporation, operates a limestone mine at Muscoda, near Bessemer, 12 miles southwest of Birmingham, served by its own railroad transportation system. The mine has a capacity of 130 tons per hour. Average analyses of a recent month's production arc as follows: Fe²zO³ SiO² Al²O³ CaCO³ MgCO³ Lump, percent............................. 0.51 0.22 98.63 0.14 Crushed and washed, per cent,................ 0.70 0.26 98.36 0.18 Lump stone, 2 1/2 to 755 in., is used in open-hearth operations at Fairfield Steel Works. Fine crushed and washed stone, 1% to 0.063 in., is calcined at the lime-burning plant and used for lime charges at the Ensley open hearths. Geology The district's deposits of hematite ore occur in the Clinton formation, and the limestone beds mined are stratigraphically 330 ft. above the ore beds worked. A cross section on the center line of the mine is shown in Fig. 1. This limestone formation, 130 ft. thick, is in the Warsaw horizon of the Lower Mississippian. It lies above 100 ft. of Fort Payne chert, which is immediately above the Clinton formation, and is composcd of layers of chert and cherty limestone, approximately 50 per cent of the material being pure chert. The chert is extremely hard, and the cost of driving raises through it is very high. Both iron ore and limestone deposits lie on the southwest limb of the Jones Valley anticline, the formations dipping from 15' to 32' to the southeast. The iron-ore seam outcrops along the crest of Red Mountain, a ridge with northeast-southwest trend rising 200 to 300 ft. above Jones and Shades valleys at the

Jan 1, 1938

TO THE BOARD OF DIRECTORS AND MEMBERS OF THE AMERICAN INSTITUTE OF MINING AND METALLURGICAL ENGINEERS GENTLEMEN: Submitted herewith are the report of the Treasurer for the year 1945 and reports for the same year of the following standing committees: Membership, Admissions, Papers and Publications, Mining and ' Metallurgy (Magazine), and Library. To these reports you are referred for additional details. Membership Membership, counting all categories other than Student Associateship, continues the upward trend of the last 10 years, reaching a total, as shown in Table 1, of 12,081. The net gain of 406 would

Jan 1, 1944

Discussion of the paper of G. K. Burgess and J. J. Crowe, presented at the New York Meeting, October, 1913, and printed in Bulletin No. 82, October, 1913, pp. 2537 to 2591. HENRY M. Howe, New York, N. Y. :-I think we can hardly rate the importance of the entry of the Bureau of Standards into our field. There is no body in the world that is better fitted to undertake this work than that Bureau, and it is work which really calls for the aid of some national organization. The skill and care with which this work has been done speaks for itself. It is very striking that within a very few months the distinguished English investigator, Professor Carpenter, of whom I spoke before, thought that he had disproved the existence of beta iron by proving that the A2 retardation which Professor Burgess has now demonstrated did not occur. Dr. Burgess's demonstration of the existence of. this retardation makes the existence of beta iron very probable, in my opinion. Osmond used to call beta iron " decipuum." You knew of its existence as you know of the existence of certain planets, only by the perturbation which it caused. Certain phenomena could not be explained, except by assuming the existence of a third allotropic form, beta iron. The evidence that you got was always evasive and susceptible of other explanations, except that which we have to-day, which it seems to me is not capable of other explanation. Professor Carpenter proceeded in the same way that Dr. Burgess has, by taking the heating and cooling curves of exceedingly pure iron, and thought that he had shown that there was no thermal change, no absorption or evolution of heat at the supposed A2 point, and hence that the A2 point did not exist. This he did by a piece of reasoning which I think seems to most of us rather surprising. That is to say, if of ten witnesses, three have seen a thing and seven have not, the evidence of the seven who have not is set aside, and that of the three who have seen stands. In Dr. Carpenter's own experiments under certain conditions he found the A2 change, the heat evolution., under certain others he did not. That is like the three witnesses who saw and the seven who did not see. You can arrange your test so that this change will not become visible or so that it is masked. But though an existent change can be masked a non-existent one cannot be shown. So that the reasoning seemed to me wholly fallacious.

Jan 12, 1913

By Stephen E. Merritt, John W. Straton, T. Carl Shelton

Surveying and mapping are used to locate and visually portray objects, lines, or areas in relation to a reference point or line. The actual making of the measurements to locate the objects and points falls under surveying while mapping is concerned with putting the survey information into a graphical form. Generally, the type or class of proposed survey depends on the precision required. Some surveys may need only approximate measurements which can be obtained by simply pacing or by using an ordinary measuring tape; others may require much accuracy, thus calling for the use of an engineer's transit or theodolite along with a graduated steel tape for horizontal measurements, or a level and a graduated rod for measuring vertical distances. Mapping is likewise dependent on accuracy requirements. For example, a general layout showing the relative position of surface facilities may not call for a large scale of dimension or great precision whereas for detailed work, a large scale plus care in plotting points and drawing lines and curves are important factors. SURVEYING METHODS There are many kinds or types of surveying methods. Some examples include : land surveying for determining boundaries of land areas ; route surveying for locating roads, highways, right-of-ways, and haulways; city surveying for laying out lots, streets, and alleys; and mining surveying for projecting mine openings and locating mining operations. See Fig. 1. There are other types of surveying than those named, but in general, the type of method to be used will depend on the purpose for which the survey is to be made.

Jan 1, 1981

By G. P. Conard, E. H. Rennhack

The creep behavior of hot-rolled, hypoeutectic Zn-Ti alloys was investigated in the temperature range from 0.43 to 0.53 TM. Secondary flow was found to originate primarily from strain-induced gvain growth where grain boundary )nigvation served to relieve the strain energy of distortion introduced by slip, grain boundary sliding, and subgvain formation. The extent to which this recovery mechanism operated was determined by the ratio of grain width to the spacing between planar fibers of TiZn,, compound particles generated in these alloys during rolling. When this ratio was unity, creep resistance demonstrated a marked improvement. In this condition, which was fulfilled by annealing following rolling, structural stability was enhanced with decreasing grain size below the equicohesive temperature (-0.5Tm), while the reverse was true above this temperature. TITANIUM concentrations approaching the eutectic composition of 0.23 wt pctl have been shown to promote a significant increase in the creep resistance of rolled zinc,2 The alloying effect created with titanium is somewhat unique; a structure closely resembling that of a fiber-reinforced metal composite can be developed which selectively modifies creep strength in preference to other mechanical properties. In an earlier investigation,~ the present authors found that, while the fiber network, composed of individual TiZn,, compound particles, had a distinct influence on rolled texture, the crystallographic variations produced were of minor importance with respect to creep. Rather, creep resistance seemingly increased when the grain size appeared to coincide with the in-terfiber spacing. The work described here was undertaken to explore this effect in greater detail. EXPERIMENTAL PROCEDURE Three zinc-base alloys containing 0.05, 0.12, and 0.16 wt pct Ti were prepared from CP zinc and iodide titanium in the form of 4 by 2 by f in. chill-cast ingots. The melting and casting procedures for these alloys have been detailed el~ewhere.~ Individual ingots of each alloy were hot-rolled at 200°C (392°F) to total reductions of 10, 25, 50, 75, and 90 pct in from one to five passes, respectively, employing a 10-min reheat prior to each rolling pass. With grain, tensile-type creep specimens with a 1-in.-long, -in.-wide gage section were machined from the rolled strips for test purposes. Annealing studies to explore the influence of grain size on secondary creep flow were carried out at 400°C (752°F) in argon for times extending up to 60 min. The grain-size effect was evaluated in terms of average grain width and length values statistically derived from lineal intersection measurements.4 A similar method was applied in establishing the average interfiber spacing, i.e., average perpendicular distance between adjacent planar fibers. The creep characteristics of the alloys were investigated by means of constant-load and constant-stress creep tests. The former tests were conducted at 25°C (77°F) under an initial stress of 10,000 psi, while the latter were performed in the range from 25°C (77°F) to 90°C (194°F) at stress levels varying from 8000 to 22,000 psi. Total specimen strain, as determined with Budd HE-1161-B strain gages, was in excess of 0.10. Maintenance of constant stress was achieved through periodic load reductions made at 0.01 strain intervals to compensate for the attendant incremental reduction in specimen cross-sectional area. The maximum indicated error in the applied stress at these strain intervals was less than 3.0 pct. RESULTS AND DISCUSSION Constant-Load Creep. In an effort to clarify the in-terrelation between interfiber spacing and grain size with respect to the creep resistance of the Zn-Ti alloys, their separate effects on secondary creep rate were determined as a function of titanium content and rolling reduction. These results are set forth in Figs. 1 and 2, respectively. The average grain diameter plotted in Fig. 2 was resolved from average grain width and length values. No data are presented for reductions of less than 50 pct because of the inability to obtain consistent measurements on these strips. The curves of Fig. 1 indicated that, for a given titanium content, a decrease in interfiber spacing, as produced with increasing reduction, promoted a decrease in creep rate. Depending on titanium content, however, wide variations in creep rate occurred at the same interfiber spacing suggesting that interfiber spacing, by itself, has little or no influence on creep resistance. Grain size, on the other hand, decreased progressively with both increasing rolling reduction and titanium content, the effect of which led to a pronounced decrease in creep rate, particularly when the average grain diameter became smaller than 3.0 x 10"4 in., Fig. 2. The continuity of this relationship tended to support the view that grain size rather than interfiber spacing was predominant in controlling secondary creep. Annealing Effect. The observed dependence of creep flow on grain size suggested that a further contribution to creep resistance would result when the alloys were annealed to effect a coincidence between grain width and interfiber spacing, see Fig. 3(b). ~eiides creating an immediate barrier to grain boundary movement, annealing offered the possibility of providing increased structural stability by eliminating many high-energy, mobile grain boundaries.= To test this hypothesis, specimens from the Zn-0.16 Ti strips reduced 75 and

Jan 1, 1967

By James E. Lawver, James L. Wright

This paper describes the design of a cell used to measure the electrical conductivity, or the reciprocal resistivity, of granular materials. It also establishes a quantitative relationship between the electrical conductivity and the electrical separation of selected mineral samples. It is estimated' that the free world produces about 13 million tons of mineral concentrates a year by electrostatic or electrodynamic methods. At least 95% of these concentrates are produced by corona discharge type machines that separate minerals by exploiting the differences in their electrical conductivity. But, what is meant by the electrical conductivity of a mineral? How large a difference in the electrical conductivity of two mineral species is necessary to effect a separation? Just what is the role of conductivity in electrical separations with regard to capacity and selectivity? There is a considerable amount of information in the literature on both the mechanisms of conduction and the values of the electrical conductivity of pure single-crystal mineral specimens. In addition, some insight into the role of mineral conductivity can be obtained by referring to a Bureau of Mines publication' in which 95 minerals have been grouped as conductors or insulators as a function of temperature. The classification was made on the basis of the percent of weight that reported as "conductors" in an electrical separator. But, as is often the case in the mineral industry, practical application leads theory — and there is little useful information in the literature giving any kind of quantitative relationship between electrical conductivity and electrical separations. The problem is a bit complex because electrical conductivity per se — which can be rather easily measured on large, single grains — is not sufficiently informative to permit quantitative predictions of the separability of the mineral system. Practical "high-tension"* separations are made at such feed rates that the band of minerals on the rotor is multilayered in thickness. Thus, the effective conductivities of minerals as seen by a high-tension machine include particle-to-particle contact resistance, which is often a controlling factor in making a separation. This is particularly true when the mineral grains are coated with slime or with a dielectric surface film. From a high-tension separation viewpoint, one is actually concerned with the time required for corona-charged grains to lose enough charge so that the centrifugal force acting on the particles exceeds the image force holding the grains to the rotor. This calculation requires a knowledge of the effective mineral conductivity s. (The conductivity of the metal rotor is sufficiently greater than that of the minerals so that it need not be considered in charge decay calculations.) The charge density at time t can be approximated by the relaxation equation.3 where t 5 charge density at time t r, - charge density when t = 0 cr e total electrical conductivity £ = permittivity The time required for the charge density to fall to l/e of its initial value is called the relaxation time and is numerically equal to €/n. AS defined here, u is the conductivity of an element of homogeneous grains making contact with each other and with a grounded rotor. This paper deals with the design of a conductivity cell used to measure a, or its reciprocal p, the electrical resistivity. CELL DESIGN Initial test work was performed with a cell recommended by ASTM.4 Since the reproducibility with the ASTM cell was not satisfactory, it was decided to

Jan 1, 1970

By Jack Parker

There are some simple theoretical approaches to pillar design but they leave much to be desired. There are also more complex theoretical approaches, but at this time the most realistic approach is to go into the mines and observe and measure how real pillars are performing under real conditions; to allow the information thus gathered to ferment in our minds - then to project the behaviour of those pillars into our new designs and mining techniques, probably with no formulas at all. Examples, from half-a-dozen different mines, show how a simple- minded approach, through observation and measurement, led to changes in pillar design which often contradicted the textbook but made very significant contributions to mining safety, efficiency and costs. The good news is that we know a lot more about pillar design than we realize. We have, between us, looked at millions of pillars of all kinds, under all conditions, but we have overlooked what they are trying to tell us. We can take problem situations and turn them into opportunities and, in that way, become better stewards of the resources which have been given to us.

Jan 1, 1983

By D. J. Reed

Concord coal mine near Bessemer, Ala., built, owned, and operated by Tennessee Coal & Iron Div., U. S. Steel Corp., produces only a metallurgical grade for use as coke in blast furnaces of the division at the Fairfield and Ensley works. Capacity of the operation is approximately 800 tph, half of which is delivered to the coke and coal chemical plant at Fairfield after beneficiation to metallurgical grade coal. The remaining portion of the mine run is rock and refuse removed during preparation. Concord mine coal is hoisted to the surface coal preparation plant by an underground slope conveyor. The slope conveyor is 2449 ft long and has a lift of 729 ft. At time of installation the Concord mine slope conveyor was the largest single conveyor unit ever made with respect to belt horsepower and total lift. After several years it became necessary to determine the cause of slope conveyor cover wear.

Nov 1, 1956

GENTLEMEN Submitted herewith are the report of the Treasurer for the year 1938 and reports for the same year of the following standing committees: Admissions, Membership, Papers and Publications, Mining and Metal¬lurgy (Magazine), Library, Speakers for Local Sections and Student Societies, and Student Relations. To these reports members are referred for further details. Membership.-The end of the year 1938 saw Institute membership at an all-time peak: 12,474, made up of 2898 Student Associates and 9576 members of other classifications. The next highest level had been reached at the end of 1921 when corresponding figures were: total, 10,329; student members, 1450; all other classifications, 8879. The net gain for the year was 1495, of which 751 were Student Associates and 744 in the other categories. Two factors contribute to the growth of membership: (1) the enrolment of new members; and (2) the retention of members already on the roll as reflected in a relatively small number of resignations and suspensions for nonpayment of dues. For the first, much credit goes properly to the general Membership Committee that functioned for a second year under the chairmanship of Clyde E. Williams. With the cooperation of Institute members in general, to whom Mr. Williams expresses appreciation in his report, the Committee has been successful in acquainting eligible nonmembers with the purposes, activities and advantages of the Institute. The result has been the receipt during the year of 1162 applications, exclusive of Student Associates. This compares with 1212 during 1937 and 1266 during 1936. However, in considering this modest decline, account must be taken of the somewhat less prosperous conditions prevailing in the mineral industries and, consequently, among engineers engaged ?in those industries.

Jan 1, 1939

By W. A. Backofen, D. Lee

The deformation of textured sheet of titanium and several of its all-a (hcp) alloys was investigated with two kinds of experiments: tension testing along different directions in the plane of the sheet, and combined-stress loading along the principal axes of anisotropy (the rolling and transverse directions). Texture and plastic anisotropy were evaluated with pole figures and by measurement, as a function of orientation, of the tensile transverse-strain ratio, or R parameter. The results as a whole can be rationalized qualitatively with the present understanding of deformation mechanisms in titanium. Quantitative agreement between the orientation dependence of tensile yield strength and the Predictions of continuum ANISOTROPY in the properties of engineering materials is more the rule than the exception because anisotropy in structure is so common, and the one generally follows the other. Two broad categories of structural anisotropy are represented by mechanical fibering and crystallographic texture. The former is important in many aspects of fracture.' The latter has more significance for yielding and plastic deformation, theory, using the R measurements, was relatively poor. However, in tension-tension quadrants of the yield-locus diagrams, the difference between theory and experiment was hardly more than 10 pct. The maximum texture-hardening effect was found in a 4Al-1/4O2 alloy to be nearly 50 pct. In the compression-compression quadrant, {1012} deformation twinning prevented the locus from expanding much beyond the Position predicted for isotropic material. With increasing temperature the trend in R was downwards, approaching unity (isotropy) near the a-transus temperature; an accompanying development was large amounts of neck-free extension. which are of special concern in this paper. The tendency has been to view crystallographic texture more as a liability or curio than as an asset. The prominent exception is found in silicon-ferrite sheet for power-transformer cores, which is processed to develop a new optimum texture for high electrical efficiency. Yet it should be possible to find other examples, involving other kinds of properties. More specifically, there is good analytical reason to expect improved combined-stress yielding resistance in suitably textured material,2,3 and it has now been shown by experiment that texture hardening or softening is a potentially useful phenomenon in certain engineering devices and processes.'-I To date, work has included measurements of the transverse (width to thickness) strain ratios in the

Jan 1, 1967

By A. B. Kinzel

IT is with sincere appreciation and a deep sense of responsibility that I accept the honor of delivering the Howe Memorial Lecture. In our time metallurgical research has delved into phenomena ever more complex in character, so that much of this work must be done by organized teams. We, of the Union Carbide and Carbon Research Laboratories and the Electro Metallurgical Co., are truly a team and the lecture which is to follow is due largely to a few of the outstanding members of that team here cited and well known to you in their own right: John Lamont, whose work deserves special recognition, Walter Crafts, William Forgeng, William Binder, Robert Fowler, and David Swan. Thus it is a fitting pleasure to accept this honor for the research institution which I represent. Henry Marion Howe was truly inspirational and his breadth of view was such that he could use either the method of rigid proof or implied mechanism to further the broad understanding. But perhaps his outstanding characteristic was his sound judgment and his ability to weigh observations. The following is replete with observations and judgment as to their implication. We would like to feel that it is the type of dissertation which Howe, himself, would have enjoyed. Chromium carbides in stainless steel have, in a sense, been a key to the progress of the stainless steel industry. Brearley's first stainless steel, containing approximately 0.30 pct C, was successful because it differed from previous Fe-Cr alloys in that the carbides were present in such amount and form as to provide the stainless and cutting properties. Again, the 12 pct Cr die steels with a carbon content of 1.5 pct or more achieved their properties by virtue of the form and distribution of the chromium carbides. In the straight chromium steels with from 12 to 25 pct Cr, chromium carbide amount and distribution are once more the determinants with respect to physical properties and corrosion resistance. In each of the cases just cited the role of the carbide is in essence similar to that of iron carbide in carbon steel and this story is so well known that we need not dwell on it. In the austenitic stainless steels, the chromium carbide plays only a minor positive role with respect to mechanical properties, and for corrosion resistance the objective is to achieve maximum homogeneity. Thus the tendency has been to ever lower the carbon and correlatively the chromium carbide content of the austenitic steels. Today stainless steels with carbon less than 0.03 pct are beginning to find their true place, and this is being aided in major degree by our Company's introduction of a new type of ferrochromium having negligible carbon. The role of carbon in these austenitic steels has long been recognized, and a truly enormous amount of research has been devoted to the subject. Much has been learned about corrosion resistance, but the attack on the problem from the point of view of carbide precipitation and the nature thereof has left much to be understood. Because of its fundamental importance to the future of stainless steels, further study of the mechanism of carbide formation in austenitic steels is of interest. In the 18-8 Cr-Ni steels, which are typical of the austenitic class of steel, carbon is soluble in the aus-tenite to the extent of approximately 0.15 pct at 1832°F (1000°C). The solubility becomes less with decreasing temperature, so that at 1652°F (900°C) the solubility limit is approximately 0.06 pct, at 1472°F (800°C) it is about 0.03 pct, and at 932°F (500°C) it is approximately 0.01 pct. Obviously this is the ideal situation for the classical precipitation phenomenon. It is true that, in a sense, 18-8 austenite resulting from annealing is in a metastable state, and the phenomenon of ferritic precipitation from this austenite should be considered. However, in a so-called fully austenitic 18-8 steel this is secondary with respect to the carbides and can be neglected. A wide variety of chromium carbides is known. Only one chromium carbide, Cr,,C,,, frequently referred to as Cr,C, has been found in unmodified low carbon 18-8 steel. This, fortunately, simplifies the study of the precipitation phenomena. For this study an A.I.S.I. type 304 stainless steel of commercial quality was selected. Analysis showed C 0.07 pct, Mn 0.49 pct, Si 0.33 pct, Ni 9.34 pct, Cr 18.91 pct, and N 0.033 pct. As expected with this composition the steel was homogeneous after annealing except for a few pools of ferrite, which were disregarded in that their location was not coincident with subsequent carbide precipitation areas. On corrosion testing the steel was normal and typical of good commercial quality. Specimens 1/2xlx4 in. were annealed and subjected to precipitation heat treatment for 100 hr at 100" temperature intervals from 1000° to 1500°F and for ten selected intervals ranging from 5 min to 64 hr at 1300°F. These blocks were then cut into small pieces for metallographic studies. The first problem

Jan 1, 1953

By Enid C. Plante, K. L. Sutherland

Practical metallurgists are unanimous in stating that oxidation of mined sulphide ore adversely affects separation of the constituent minerals under standard conditions in a mill. Frequently, the need for different operating conditions in different plants is attributed either to the extent of oxidation of the mineral surfaces or to soluble oxidation products. The investigations reported in this paper study the effect of oxidation on the primary condition necessary for flotation, namely that of adhesion of an air bubble to the mineral. Oxidation Products from Sulphide Minerals Weinig and Carpenter1 state that the relative rates of oxidation of some sulphides are: FeAsS > FeS2 > CuFeS2 > ZnS > pbS > Cu2S tetrahedrite. They also show that oxidation is rapid at first, that sulphides of older geological formations are more stable than those of recent date and that mixtures oxidize more rapidly than any one mineral alone. The more rapid oxidation of mixtures is borne out by results of Gottschalk and Buehler2 who found that PbS, zns and cus oxidized 8 to 20 times faster when pyrite was present. Only the end products of oxidation, sulphate and the metal ion, were identified in these tests. Gaudin3 states that pyrite is difficult to oxidize in the laboratory. Winchell,4 using pyrite containing 99.98 pct FeS2, allowed water to percolate through a bed of this ground material. At the end of three months only a trace of Fe+++and So4- were found. Even after 10 months the quantity of Fe+++ was only 7.8 mg and SO4- 25.5 mg per liter of percolating solution. Car-michael5 confirmed Winchell's results on the slow oxidation of pyrite. Usually the oxidation of sulphide surfaces has been conducted in neutral or acid solutions, the acidity being caused by the oxidation products. Eliseev and Nagir-nyaka found that treatment of pure pyrite with lime gave only thiosulphate, but considered it possible that thiosulphate was obtained not by oxidation of the pyrite itself, but by oxidation of calcium disul-hide. Mitrofanov7 suggested that thiO~ulphate was formed by the following process: oxidation of sulphide to give free sulphur (this frequently happens with marcasite), followed by oxidation of the sulphur to sulphur dioxide and reaction of the sulphur dioxide with sulphur to give thiosulphate. Ferric and ferrous hydroxides, or similar compounds, were shown to be present. The Research Staff of the United Verde Copper Co.8 treated ore from the United verde mine with lime. Thiosulphate, sulphide and polysulphides were stated to be

Jan 1, 1949

By W. G. Whildin

This paper will be confined to a discussion of the methods in use in the property of the Lehigh Coal and Navigation Co. in the Panther Creek valley.

Jan 1, 1915

By J. D. Rice, H. H. Rachford, G. H. Bruce, D. W. Peaceman

The problem of unsteady-state gas flow through porous media leads to a second-order non-linear partial differential equation for which no analytical solution has been found. In this paper a stable numerical procedure is developed for solving the equation for production of gas at constant rate from linear and radial systems. An electronic digital computer is used to perform the numerical integration using an implicit form of an approximating difference equation. Solutions are presented in graphical form for various values of dimension-less parameters. The solutions are compared with the laboratory study of gas depletion in a linear system. INTRODUCTION Production of fluids from porous rock reservoirs is essentially a transient process. Transient gradients develop as soon as production begins, and further withdrawals continue to cause disturbances which propagate throughout the reservoir, each adding in some way to the prior ones. A correct mathematical analysis of this behavior is complicated by the fact that the transient or unsteady-state flow of compressible fluids must be described by difficult second-order partial differential equations. As a practical matter, three distinctly different cases arise: 1. Flow of single-phase liquid 2. Flow of gases 3. Multiphase flow The first of these has been found to give a linear second-order equation similar to the well-known heat flow equation. where 7 is fluid density, 8 is time, and a a constant for the system, provided d 7 = r cdp, where the compressibility, c, is constant over the range of pressure, p, considered. Solutions of Equation (1) for both linear and radial flow are available in several forms.2'3' On the other hand. the second case, which is the flow of gas, gives a non-linear second-order equation, the solution of which is not known. Although a number of approximate solutions have been proposed, each is limited in value by the associated simplifying assumptions. Inasmuch as the analysis of transient flow is limited to liquid systems, a solution of the second case is necessary if further progress is to be made in studying underground fluid movement. For this reason a solution of Equation (2) was undertaken by means of numerical integration of approximating difference equations. BASIC DIFFERENTIAL EQUATION Equation (2; is derived by combining the equation of continuity, the perfect gas law, and Darcy's law to give the basic differential equation Strictly speaking, the fluids present in a gas reservoir are not perfect gases. Furthermore, there are indications that over certain velocity ranges, Darcy's law is not applicable. It would not be practicable. however, to attempt to obtain numerical solutions which would take into account all the possible variations from these laws which could occur in actual systems. The

Jan 1, 1953

By E. P. Whelan

A recent investigation1 into the origin of "ghost boundaries" in dilute Cd-Mg alloys has indicated the persistence of a segregated solidification substructure in spite of a homogenizing treatment designed to remove such segregation. Although no grain growth experiments have been reported on these segregated alloys, the homogenizing treatment used in grain growth studies on other dilute alloys2-7 is similar in

Jan 1, 1968

By Sarat C. Rubra

Geographically, British India includes India or Hindustan proper, Burma, and a part of Beluchistan. In ancient times India occupied a very important position anlong the producers of minerals and metals; in fact, as late as the middle of the seventeenth century, it contributed a very considerable quota of the mineral and metal supplies of the world. The branches of the industry worthy of special note are gold, silver, lead, antimony, copper, iron, diamonds and other precious stones. The famous " Damascus steel" was originally manufactured in India, Damascus being only a mart; and it is interesting to note that even at the present time this product is still made in India. Prior to the discovery of diamonds in Brazil in 1728, India was the sole producer of this important mineral; and while no diamond-mines are now systematically worked, fine specimens are occasionally reported to be found in river-beds and in alluvial diggings. For ages, nearly all of the minerals of present commercial value have been produced and worked in India, and many of the deposits may still play an important part in the world's mining and mineral history. Despite the patient work of the ancient Indians, the limited knowledge they possessed of pumping and ventilation precluded the possibility of attaining any great depth in mining. Under special conditions, shafts have been sunk to 600 ft., but the average depth was much less. As a result of this limitation, the ancient miners confinecl their work to the available ores in sight, leaving large bodies of ore intact, which can be profitably worked with modern methods of mining. As an evidence of this statement may be mentioned the mines of the Kolar gold-fields in Mysore, which have reached in some shafts a. depth exceeding 2,400 ft. Traces of ancient work in these

Jan 1, 1904