Search Documents

By Leonard Grimshaw

THE idea of bonding two dissimilar ferrous metals, and making use of both, is an old one. Tips have been brazed onto tool shanks for many years. The bonding of larger pieces to form whole bars and sheets has also been accomplished, but has received little attention in the technical literature, although a number of patents have been issued covering various methods for its accomplishment. There are three main motives behind the manufacture of composite steels. One is that the physical properties of one steel may supplement those of another; a useful, but at the same time, hard, brittle steel may be backed by a soft ductile one, or a stainless steel may be backed by a steel possessing greater strength. Another motive is direct lowering of cost; an expensive steel may be backed by a less expensive one, bringing down the cost of the piece as a whole. The third motive is an indirect lowering of cost, as when a useful steel is backed by a steel that is easier to machine, so that machining cost on a finished product is lowered considerably. Often more than one of these motives lead to a decision to use a com-posite steel.

Jan 1, 1936

By J. T. Lapsley, I. I. Cornet, A. E. Flanigan, R. Hultgren, J. E. Dorn

WITH the greatly expanding use of magnesium during the war, it appeared necessary to the War Metallurgy Committee that procedures of heat treating common magnesium casting alloys be investigated systematically. Accordingly, the National Defense Research Committee of the Office of Scientific Research and Development placed a research contract with the University of California, supervised by the War Metallurgy Committee. Research on the solution heat treatment and aging of magnesium alloy AZ92, (formerly ASTM No. 17; also known as Dowmetal C or AM260) which was done under "Restricted" Project NRC-21, in 1942-1943, and reported, in detail in a final report to the OSRD on September 3, 1943, is the basis of this paper, which has been released for publication by the OSRD. American experience with magnesium alloys prior to World War II was limited, although some of these alloys had been in commercial use since 1909. Requirements of the aircraft industry for light alloys made it imperative to understand and utilize the advantageous strength-weight properties of magnesium castings. Magnesium casting alloys are commonly solution heat treated to increase their ultimate tensile strength and ductility; this treatment may be followed by an age hardening at elevated temperatures, which raises the tensile yield strength but diminishes the ductility. In the present investigation, AZ92 was studied to determine the effects on properties of various solution heat treatment and aging schedules. The principles of heat treatment of magnesium alloys are the same as for other non-ferrous alloys. The alloy studied, AZ92, has a nominal composition of 9 pct aluminum, 2 pct zinc, and minor constituents. Fig I shows, by the projection of isothermal sections on the concentration plane, the solubility surface1 of the ternary magnesium-rich solid solutions as determined by X ray analysis. From this figure it may be seen that above approximately 375°C (707°F), AZ92 alloy is a single phase alloy at equilibrium; below this temperature the equilibrium condition is a. two phase alloy. The beta constituent which precipitates from the solid solution exerts a hardening effect. Because the zinc concentration is only 2 pct, and because of its solubility relations, AZ92 resembles a binary alloy of magnesium with aluminum. The solubility curve1 of Fig 2 shows how rapidly the solubility of the beta phase decreases with decreasing temperatures. Unlike many aluminum alloys, magnesium alloys do not age harden at room temperatures; precipitation hardening of AZ92 alloy is performed at about 177°C (350°F). At this temperature about 3 pct aluminum

Jan 1, 1947

By J. V. W. REYNDERS

NOT only is your toastmaster silver-tongued in his references 'to myself, but he is also quite in the habit of "saying it in silver." I have analyzed with some care his statistics of the world's silver production, which have been distributed here along with the menu, although frankly from the point of view of most of us, the distribution rather than the production of silver is of immediate concern. Unlike the performers by whom we have been entertained between courses, the rest of us on the program will have to do without costume or musical accompaniment, which as my friend Rains can testify puts an artist under severe strain. I am entitled by right of office and of precedent to receive your attention for ten minutes. The Governor, who appears on the program as a speaker; however, has asked me for five minutes of my time, and Senator Thomas has insinuated that he would appreciate one-half of the remainder, wherefore, I must ask your close attention to the very brief remarks that I am able to make under such restricted circumstances. To begin with, I want you to believe that I am approaching the task set by your toastmaster with misgivings. In looking over the Institute records relating to the Salt Lake City meeting of 1914 for some precedent as to what I ought to say, I found but one reference-and that of the following indefinite char¬acter-" and Friday night there was a hilarious banquet to 350 members and guests."

Jan 1, 1925

By E. Houdremont

THE different influences exerted by the various alloying elements in iron and iron-carbon alloys give rise to a great number of complexities, which are difficult to grasp. It is important therefore to study any sys-tematic relations that may exist between the effects exerted by the various alloying elements, in order to obtain a general classification and thus a clearer conception of the nature of alloy steels. A systematic survey of the alloys of iron, based on an investigation of the binary equilibrium diagrams, was recently published by Wever. Although his work deals little with properties of importance in works practice, its purpose being rather to point out the theoretical agreement among the types of binary equilibrium diagrams and the position of the alloying elements in the periodic system (atomic radii, etc.), the classifica-tion proposed nevertheless also suggests relationships among the proper-ties of the alloys in question, even though the alloys may contain carbon in addition to iron and the alloying element. Wever divided the alloys of iron into one group exhibiting an open or enlarged gamma field and another exhibiting a closed or restricted gamma field, with both groups capable of further subdivision depending upon whether a continuous series of solid solutions is formed, or, owing to the separation of compounds, etc., only a limited series. Thus all alloying elements which with iron form a closed gamma field, a "gamma loop," produce alloys that beyond the composition correspond-ing to the greatest extent of the gamma loop are composed of ferrite alone at all temperatures. Alloys of this composition accordingly are not susceptible to ordinary heat treatment because of the lack of tran-formations. Steels. of this class may thus be divided into steels that contain less than the critical amount of alloying element, and are subject

Jan 1, 1934

By J. W. Rutter, K. T. Aust

The temperature dependence of the rate of grain boundary migration was measured in bicrystals of zone-refined lead containing from 20 to less than 1 ppm by wezght of tin. The apparent activation energy in the temperature range from 320" to 200oC is markedly dependent upon the solute tin concentration and upon the orientation relationship of the grains adjacent to the grain boundavy. The quantitative experimental observat~ons are compared with the predictions of various theories of grain boundary migration. In previous work.&apos;?&apos; the mobility of individual grain boundaries was studied as a function of impurity concentration and type of boundary. Grain boundary migration occurred at the expense of dislocation arrays which were introduced into the specimen during solidification. Boundary mobility in zone-refined lead at 300°C was markedly decreased by small additions of tin. 0.004 wt pct being sufficient to decrease the rate of grain boundary migration by a factor of 1000. The mobility of grain boundaries having polar orientation relationships near 38 and 22 deg about <Ill>, and 28 deg about <100>, was much less sensitive to tin concentration in the range studied. As a result, these boundaries have relatively high mobilities. The present paper is a continuation of the above study. Data are now presented on the temperature dependence of the motion of individual grain boundaries in zone-refined lead as a function of solute tin concentration and orientation relationship of adjacent grains at the grain boundary. The experimental observations are compared with the predictions of a number of theories of grain boundary migration3-8 which, prior to the present experimental investigation, could not be critically evaluated. EXPERIMENTAL PROCEDURE The striation or lineage structure of melt-grown single crystals of zone-refined lead, containing various additions of tin, was utilized to provide a driving force for grain boundary migration, as previously described.1,2 Each grain boundary under study separated the striated single crystal from another grain which was introduced by localized plastic deformation and recrystallization of a small region of the sample. The speed of migration of grain boundaries in dilute alloys of tin in zone-refined lead was investigated as a function of 1) tin concentration from < 0.0001 to 0.002 wt pct, 2) temperature in the range of 200" to 320°C, and 3) orientation relationship of the adjacent grains at the grain boundary. The substructure driving energy available for grain boundary migration was estimated to be about 4000 ergs per cu cm, within a factor of two, from specimen to specimen.&apos; The specimen dimensions, and growth and alloying procedures for the preparation of striated single crystals of lead of known tin composition, were as described previously.&apos; Each bicrystal was carefully wrapped in aluminum foil, and annealed in a well-stirred salt bath consisting of 50 pct NaNO2 and 50 pct KNO3, for known periods of time at a series of constant temperatures (*2°C). The grain boundary positions, before and after each anneal, were determined by etching lightly in a solution of 5 pct nitric acid in methyl alcohol, in order to follow the motion of the boundary and determine its rate of migration. Thus, the rate of motion of the grain boundary in a single specimen was measured at various temperatures. The above procedure was carried out for each grain boundary in seventeen different bicrystal specimens.

Jan 1, 1960

By Y. S. Bonillas

Page I. Introduction.......................... 286 II. Physiography.......................... 286 : 111. Introductory Geology...................... 287 IV. Rocks of the District ...................... 288 (A) Sedimentary Rocks..................... 288 Pinal Schist ........................ 288 Bolsa Quarteite....................... 289 Abrigo Limestone...................... 290 Capping Quartzite..................... 291 Martin Limestone...................... 292 Escabrosa Limestone .................... 295 Naco Limestone....................... 296 Cretaceous Deposits..................... 296 Glance Conglomerate................... 296 Morita. Mural and Cintura Formations........... 297 (B) Igneous Rocks........................297. Pre-Cambrian Granite.................. 297 Pre-Cretaceous Granite Porphyry............. 298 Rhyolite........................301 Other Dikc Rocks.................... 301 V. Structural Geology........................ 304 General Structure of Mule Mountains............. 304 Fault Blocks and Other Divisions............. 304 Igneous Rocks...................... 312 Copper Queen Block..................... 313 Fault Blocks...................... 313 Intrusions....................... 315 Don Luis Block....................... 315 Intrusions and Orebodies................. 316 VI. Geologic History......................... 316 VII. Metamorphism and Mineralization................. 318 General Metamorphism.................... 318

Jan 1, 1917

By R. U. Fitting, A. C. Bulnes

Field experience with limestone and sandstone production indicates the existence of wide differences between the reservoir behavior of these two types of formation. Little attention appears to have been given to the separate study of the flow of fluids and the retention of fluids in limestones. This paper presents data and arguments to demonstrate the existence of a difference between the two types of formation, and urges the separate intensive investigation of limestone reservoirs. AH experimental data presented pertain to dolomitic limestone formations in west Texas and New Mexico. Two kinds of Porous media are recognized— intergranular and intermediate. Intergranular rocks are those in which the porosity and permeability are determined by the geometrical properties and the sorting of the sedimentary units; intermediate rocks, those in which there is no direct relationship between grain properties and the porosity and permeability. Limestones in general are intermediate media. The partial relationship between porosity and permeability of any class of Porous media is represelried by an area of .finite extent and definite shape on the permeability-porosity plane. The horizontal and vertical variations of porosity and of permeability in limestone and sandstone formations are discussed and compared. Comparisons are made of connate-water content, the relative permeability-saturation relationship, and capillary phenomena in the two kinds of rocks. A number of tentative conclusions are drawn relative to the reservoir properties of lime- stones; in particular, (I) dolomitic limestones are oil bearing and apparently are oil productive in zones of permeability less than 0.1 millidarcyj and (2) primary depletion (by gas expansion) oil saturations may be lower in dolomitic limestones than in sandstones. Introduction It is well known that the reservoir performance of limestones displays numerous irregularities when compared with that of sandstones, and that the departures from "normal" behavior of limestones are more frequent and generally more marked than in sandstones. This is particularly true of fractured limestones and those that have undergone considerable development of secondary porosity&apos; A review of the literature of production research published during the past 15 years reveals a startling absence of theoretical and experimental investigations directed specifically toward explaining and predicting the performance of limestone reservoirs, even. though such problems as the prediction of water encroachment and the estimation of ultimate recoveries continue at the "inspired guess" stage. By far the greater part of the experimental data reported pertain to measurements on sandstone core samples, while the theoretical studies, almost without exception, are developed from the assumption of an ideal porous medium and therefore seldom are applicable to limestone formations. The chief cause of this situation appears to be the common belief that, to all practical intents and purposes, sandstones and the majority of producing limestone formations

Jan 1, 1945

By J. L. LeBlanc, R. L. Lewis

This study presents an analysis of annular backpressure variations associated with controlled gas kicks and their pronounced effect on casing .strings and exposed under lying formations. A mathematical model describing the volumetric behavior of an extraneous gas as it is transported from reservoir to .surface conditions under changing temperatures and pressures has been programmed in a Kingston FORTRAN II language for digital computer analysis. The gases under investigation typify Gulf Coast reservoir gases within a 0.6 to 0.7 .specific gravity range. The program output has been substantiated by actual field cases. of gas kicks encountered in Gulf Coart we1l.s. The development of empirical equations for calculating suitable gamy deviation factors for unique temperatures and pressures was incorporated in the program to provide realistic solution.. An output listing of annular backpressures and corresponding equivalent fluid densities resulting at a predetermined critical depth (casing setting depth) and total depth for selected .stages of circulation is provided in a chronological .sequence. Additional information including reservoir pressure and temperature, kill rnrid density, produced gas or surface volume of the expanded gas intro vion, drill pipe and annular volumes can he obtained from the model. This paper illustrates that a precise knowledge of the volumetric behavior of extraneous gases in annular flow and its effect on equivalent fluid densities at a critical depth is significant and should receive .serious consideration in controlling threatened blowouts and in the design of drilling programs. Surface pressures in excess of formation limitations are a threat to zones of lost circula/ion and are potentially injurious to productive intervals. A knowledge of annular backpressure and equivalent fluid density profiles for probable gas kicks aids in a technological accomplishment of drilling programs and provides a .sale tolerance in the event a threatened blowout is encountered. Introduction Drilling operations are frequently interrupted when the drill bit penetrates permeable gas sands with reservoir CtfuJ manuscript was received in Society of Petroleum Engineers ofice Am. 1 1967. Revised manuscript received JuIy 7. 1968. Paper (SPE 1860) kae presented at SPE 42nd Annual Fall Meeting held in Houston. Tex., Oct 1-4, 1967. @ Copyright 1968 American Institute of Mining, Metallurgical, and Petroleum Engineem, Inc. pressures greater than that exerted by the drilling fluid. The differential pressures resulting permit an extraneous influx of gas into the wellbore. A suspension in drilling progress is necessary to restore fluid equilibrium throughout the system. Whether formation gas kicks originate unintentionally or by design, the prospect of a threatened or actual blowout exists and a method assuring a safe and effective well control procedure must be observed. A significant contribution to well control technology was advanced by Records et a1.l in 1962. Using the concept of transmitting a constant equivalent formation pressure at the point of intrusion, Records et al. introduced a calculation technique providing the annular backpressures encountered in a well control environment as a func tion of the volumetric behavior of a 0.6 specific gravity natural gas. In essence, the procedure outlined an annular backpressure schedule in terms of fluid volume circulated at different stages of a well control operation. A number of other publications2-&apos; proposing various techniques for controlling gas intrusions in a wellbore achieve pressure control essentially through maintenance of a constant bottom-hole pressure by surface choke adjustments. The subsequent pressure effects induced in the annulus unfortunately receive little emphasis. Due to the tedious and repetitive nature of annular backpressure computations, a theoretical solution by digital computer is introduced for predicting annular backpressure and equivalent fluid density profiles associated with controlled gas kicks. We point out the effects of volumetric behavior of extraneous gases in annular flow and related field phenomena on equivalent fluid densities at a critical depth. The investigation indicated that equivalent fluid densities at a critical depth are of significance and should receive consideration in the control of threatened blowouts and in the design of drilling programs. Theoretical Considerations The mechanism of vertical gas flow through an annulus is governed by the PVT properties of the fluid, the pressure distribution within the system, the fluid flow rates and the geometry of flow. Due to the numerous variables involved in this type of problem, certain assumptions were imposed in deriving the mathematical model and in establishing the solutions. Two gases, characterized by specific gravities of 0.6 and 0.7, were selected to typify Gulf Coast reservoir fluids. The gas intrustion entered the wellbore as an immiscible &apos;References given at end of paper. JOURNAL OF PETROLEUM TECHNOLOGY

Jan 1, 1969

By NATHANIEI HERZ

(Cleveland Meeting, October, 1912.) THE formula very frequently used for computing the economical size of pipe to transmit compressed air is that of D&apos;Arcy, as follows: d5(p1-p2)/w1l D-c w11 Where, D = the volume of compressed air delivered in cubic feet per minute,-at the final pressure. c = an experimental coefficient determined for the various sizes of pipe. d = the diameter of the pipe in inches. 1 = the length of the pipe in feet. P1 = the initial gauge-pressure in pounds per square inch. p2= the final gauge-pressure in pounds per square inch. W1 = the density of the air, or the weight in pounds per cubic foot at the initial pressure, p,. The most common case is that in which the given quantities are: the quantity of air required, the length of the pipe, and the initial pressure. The method of solution is to assume a pressure-loss and to compute the remaining factor, c/d5, thus giving the size of pipe corresponding to the assumed loss of pressure. It is always desirable to try two or more pressure-drops, in order to find the combination that is most satisfactory, since often a small change in the size of pipe will reduce or increase the loss of pressure several pounds. An alternative method is to assume a size of pipe and calculate the corresponding pressure-drop. Each method involves a series of tedious calculations to arrive at the most economical solution, and also requires the use of tables giving the constant, c, the actual diameters corresponding to the nominal pipe-sizes, the density of the air, w1, and often, for convenience, a table giving the

Dec 1, 1912

By Harold B. Fell

MANY oil producers are in disagreement with the idea held by some that an increase in the price of crude oil would be unlikely to stimulate much production and that we will be obliged to draw upon foreign sources of petroleum to supplement our domestic production as the years go by. Supporting our con trary opinion are numerous facts and figures. The most recent official estimate of the maximum efficient rate of production from the oil wells of the United States is 5,271,000 bbl per day. The Economics Advisory Committee of the Interstate Oil Compact Commission estimates, assuming certain supplies from imports and from natural gasoline and benzol, that crude oil require-

Jan 1, 1947

By Robert E. Goodwin

There are four main requirements to be considered in selecting a wire rope that will provide the best service. A proper choice is made by correctly estimating the relative importance of each of these requirements and choosing a rope with qualities that will best enable it to withstand the combination of destructive forces expected under continued service. A Good Rope Choice Matches Strength with Stress A wire rope should be (1) strong enough to sup- port the maximum load anticipated with a proper safety factor, (2) able to withstand bending and to resist bending fatigue without failure of the wires, (3) able to withstand surface abuse such as abrasion, pounding, and wire scrubbing, and (4) able to take abuse such as crushing and distortion.

Jan 5, 1969

By Sam F. Harrison

The National Board of Boiler and Pressure Vessel Inspectors again sends out this recommendation: If you have an air compressor that is mounted directly on the air tank, get it off. Characteristically, small- to intermediate-sized air receivers are thin-walled vessels, and as such are prone to failure when subjected to external loading. Many of these vessels, if not a great majority, are bought by a distributor of air compressor systems, who provides the compressor, motor, switchgear and other accoutrements-all of which are very frequently mounted on a base which is then welded to the shell of the receiver. These welds at the points of attachment transmit external loading to the tank in the form of weight and vibration, frequently resulting in stress-induced cracks.

Jan 3, 1978

By K. P. Stricker, H. Keddeinis, K. Grebe

Recent investigations by Mannesmann Research have shown that disintegration of sinter with widely varying quality levels is subject to a much more complex set of influences than was previously assumed. It was confirmed that disintegration at temperatures between 300° and 600°C (570°and 1,110°F) is triggered by the degradation of hematite. The specific tendency of hematite to disintegrate is, however, not constant: sinters containing the same amount of hematite can show widely differing disintegration tendencies, depending on structural homogeneity, porosity, and gangue quantity. Sinters with heterogeneous structures transmit stress to the hematite phase and this favors disintegration. Another factor is the brittleness of the glassy silicate phase, which can be influenced even by small modifications of minor gangue constituents.

Jan 1, 1984

By Kenneth A. Gutschick, Robert S. Boynton

Lime has become a general and loosely used term to denote almost any kind of calcareous material or finely divided form of limestone or dolomite, as well as burned forms of lime. However, according to Webster, lime is only calcined limestone (known as quicklime, unslaked lime, or calcium oxide). It also embraces the secondary product of quicklime, i.e., hydrated lime or slaked lime (calcium hydroxide). There are two basic types of limestone used for lime manufacture-high calcium and high magnesium (dolomitic). The dolomitic quicklimes and hydrated limes correspond to their "high calcium" counterparts. The only difference is that the dolomitic types are a combination of the elements calcium and magnesium, in varying percents, whereas high calicum limes contain less than 5% MgO down to 1/2%. In either case a pure form of limestone of at least 97% combined carbonate content is needed to make salable lime, barring a few exceptions. The calcination of both types is diagrammed chemically as follows: [ ] In the foregoing reversible reactions the limestone is burned (calcined) in lime kilns, with the carbon dioxide content of the stone expelled as a gas. The weight loss during calcination of pure high calcium limestone is 44%; with equimolecular dolomitic limestone, the weight loss is 48%. Since lime has a strong affinity for CO_, particularly if moisture is present, it will readily revert to its original carbonate form. This occurs when quicklime "air-slakes" and adsorbs CO.. from the air. Thus, quicklime is perishable and should be stored in dry, water-tight areas. Depending upon the type of kiln used and the physical structure of the stone, the size of the quicklime may range from sandlike granules to 8 in. lumps. However, pebble sizes ranging from 1/4 in. to 2 in. are the most common. Screened quicklime fines are also com¬pressed (pelletized) into 1 in. pellets. For some purposes ground or pulverized forms of quicklime are used, ranging from No. 10 mesh to dust. Generally a pebble of quicklime is about the same size as the pebble of limestone before calcination (perhaps shrinking slightly). A more stable form of lime is hydrated lime. This is obtained by adding water to quicklime, slaking it into a dry, fine, subsieve size white powder. Because its affinity for moisture has been satisfied, it is not vulnerable to further moisture like quicklime. However, it has the same strong affinity for CO_. The following reversible chemical reactions illustrate how hydrated lime when heated (or dehydrated) can revert to the original oxide form:

Jan 1, 1975

By Charles Will Wright

THE economy as well as the living standards of a country depends largely upon adequate supplies of raw materials at reasonable prices. Geological and climatic conditions responsible for the occurrence of commercial minerals and the growth of raw agricultural and forest products are so varied in different parts of the world that no country can be self-sufficient. The world is rapidly shrinking because of improvement in transportation facilities, but populations are steadily increasing and so are the needs for a greater production of raw materials and for their more equitable distribution. Too many barriers between nations prevent free access to the main sources of supply of the raw materials vital to neighboring nations and it is just such barriers that are often the cause of friction and even war. The International Trade Organization is doing a commendable job in helping to. break down barriers and to reduce friction, and we should now find ways to facilitate access to these sources of supply and encourage more efficient and greater production of the raw materials so urgently needed throughout the world. This cannot be done by individual selfish governmental agencies, influenced as they are by politics, nor by socialistic governments attempting to nationalize industries. It can be done efficiently only by the free individual through private enterprise properly protected against adverse governmental action. This protection can be supplied by the World Bank.

Jan 1, 1948

By Henry Wurtz

Jan 1, 1880

By Max W. Ball

Our ever-increasing use of minerals has been the outstanding fact in our American economic development. The rise in our standard of living in the past century is without equal in human history. Nowhere in time or place has the man who works lived so well, or the man who cannot work been so well cared for. We live in a new world, even the poorest of us, that our forebears of 1849 could not have dreamed. That new world has come mainly from our use of minerals. Our per capita use of nonmineral products has grown too, but by only a modest amount. Food consumption per person has grown about 15 per cent in the past fifty years; lumber use per person ,has fallen 56 per cent and that of wood for fuel 65 per cent. Of all the products of field and forest, our use, per capita, may have increased by one fifth during the present century. In contrast, our per capita use of minerals has multiplied several times. Each of us uses 2% times as much steel and 16% times as much petroleum as our fathers used in 1900. In less than half a century our per capita consumption of all minerals has probably risen by 200 to 250 &apos;per cent. Man once built with wood; today he builds mainly with brick and stone and steel. Once he traveled by the power of hay and oats; today he travels by the power of coal and oil. Rubber made from minerals is already better for some uses than rubber tapped from trees; before long it will be better for most and perhaps all uses. Even our ladies&apos; graceful legs are clad in mineral fiber, where once animal or vegetable fiber would have covered them. Our high standard of living is a product of the machine.. The machine is made of minerals. The machine is driven by minerals. The machine age is a mineral age.

Jan 1, 1949

By W. L. Penberthy, H. J. Ramey

Experimental work on the combustion oil recovery process has consisted of both laboratory and field studies. Although field experiments are the ultimate test of any oil recovery process, they are costly, time consuming and difficult to analyze quantitatively. Laboratory combustion tube experiments can be opertzted far more rapidly and cheaply, but are subject to scaling and interpretation problems. This paper points out some important design problems, operational criteria and considerations in2portunt to interpretation of results. An analytical hcut model of movement of a burning front axiully along a cylinder with heat loss through an annular insulation was developed. The result was used to identify steady-state temperatrrre distributions both ahead of and behind the burning front, with and without heat loss. Results indicate potential operating limitations on the minimum burning front rielocity (or air flux) which may be used for any given combustion tube. Results also enable estimating the effective thermal diffusivity and over-all heat loss from experimental data and thickness of the brnning zone. Resu lts of operation of a combustion tube constructed recently verify this preliminary theory in the region immediately ahead of and behind the burning front surprisinRly well. INTRODUCTION Many field and laboratory studies of the forward combustion oil recovery process have been conducted since the early publications of Kuhn and Kochl and Grant and Szasz2 in 1953 and 1954. In view of the complex and costly nature of this type of investigation, it is not surprising that no complete theory of the nature of the forward combustion Drocess is yet available. However, gross effects are understood well enough that reasonable design procedures are available for planning field operations. Nelson and McNeil 3,4 have published two comprehensive papers concerning design procedures. One major consideration in planning field operations is the fuel concentration at the burning front. Fuel concentration controls air requirements — an important cost factor in forward combustion. Although fuel concentration can be estimated from field test results by various methods, results are subject to great uncertainty in view of natural limitations on experimental observations. Nelson and hlcNeil4 recommend that fuel concentration be determined from laboratory combustion tube studies. Fuel concentration is only one of many important factors which can be studied by combustion tube experimentation. An obvious goal of imporrance must be development of a comprehensive theory of the forward combustion process. If a theory of this process can be established which matches controlled laboratory experimentation, it should be possible to apply this theory to field operating conditions with some confidence. Laboratory combustion tube studies have already yielded important information concerning the combustion process. However, details concerning the design, construction and operation of combustion tubes are rare. Combustion tubes used by various investigators vary in size, length and mode of operation. Therefore, one purpose of this paper is to present considerations important to design, construction and operation of a combustion tube. In regard to previous combustion tube studies, attention is called to Refs. 1 through 9. These references describe a wide variety of equipment types and present a great deal of pertinent experimental data. In general, combustion tubes usually consist of thin-walled stainless steel tubes containing an oil sand pack mounted within a pressure jacket. Provisions have often been made to heat the tube ex tern a lly by separately controlled heaters to reduce heat losses. This step usually permits operation at low air fluxes (air rate per square foot burning front surface) similar to those encountered in field operations. Burning is usually conducted from the air inlet end of the tube to the outflow end. The tube orientation used has been vertical or horizontal. For vertical tubes, burning has been conducted vertically downwards. As a result of laboratory studies, many of the

Jan 1, 1967

By W. S. Potter

The proportions of manganese and carbon in manganese steel are familiar to all…

Jan 1, 1915

By M. C. Flemings, G. E. Nereo

General expressions are given to describe macro-segregation in castings and ingots which results from mass flow of solute-rich liquid to feed solidification and thermal contractions. Analytical solutions are given for solidification with planar isotherms (unidirectional and bidirectional heat flow). These solutions describe inverse segregation and centerline segregation. Numerical examples are given for A1-4.5 pct Cu alloy. In 1540, Vannoccio Biringuccio published one of the first references to macrosegregation, describing the problem of exudation and inverse segregation in the manufacture of bronze gun barrels.&apos; Since then, a great many studies of macrosegregation have been reported. Recent work of particular engineering interest includes that of Marburg 2 and others:" on centerline segregation and other types of segregation in large steel ingots, and work of Adams,5 Scheil, 6 and Kirkaldy and youdelis7 on inverse segregation in nonferrous ingots. In most studies on this subject, the various types of macrosegregation have been treated as separate phenomena. For example, quite different mechanisms have been proposed for formation of centerline segregation, negative cone of segregation, inverse segregation, banding, and so forth. In this, and in several papers to follow, it is proposed that these as well as other types of macrosegregation result from the same basic mechanism and can be quantitatively described by the same basic equation. It has often been suggested that some types of segregation (such as centerline segregation and banding) occur as a result of buildup of solute at the tips of growing dendrites.2-4 ,8-10 As example, banding can be induced in centrifugal castings by mechanical vibration, and Northcott 10 suggests this might be due to the influence of the vibration on the boundary layer at the dendrite tips of the growing dendrites. However, in view of the extremely small boundary layer known to exist at the tips of the dendrites,11,12 any interpretation of macrosegregation based on this boundary layer is clearly incorrect. Note that experiment has shown that significant buildup of solute does not occur at dendrite tips in ingot solidification, but even if such buildup occurred the thickness of the enriched zone would only be the order of D/U where D is liquid diffusion coefficient and U is dendrite tip velocity. For usual casting or ingot solidification this solute-enriched layer is 10"3 cm, far too small to account, for example, for centerline segregation.11&apos;12 It has also been suggested that convection in the bulk liquid (ahead of the advancing dendrites) might cause segregation by sweeping away the solute-rich boundary layer in front of the dendrites.3 However, since there is no significant boundary layer, this explanation must be incorrect. The convection might directly cause segregation by penetrating between the dendrite arms, and presumably in a rimming steel ingot it is sufficiently vigorous to cause some segregation in this way. Centerline segregation, however, cannot be interpreted as resulting from this convection since a sharply segregated zone is usually found near the centerline, with the bulk of the ingot being nearly of nominal composition. If convection in the bulk liquid were the direct cause, a gradual change in ingot composition over the entire cross section would be expected. It is known that sudden changes in convection of the bulk liquid during solidification can result in banding,14 but it is not clear that the banding results directly from the effect of convection on solute distribution. Changes in convection also affect thermal conditions in the liquid-solid region of a solidifying ingot. It will be seen later in this paper, and in a paper to follow, that macrosegregation is strongly influenced by these thermal changes. Recognizing that in some cases of ingot solidification (as in solidification of rimming steels) convection in the bulk liquid may have a direct effect on solute distribution, we neglect it in this paper and in the several to follow. We then derive general expressions describing macrosegregation which results from the mechanism of interdendritic flow of solute-rich liquid

Jan 1, 1968