Search Documents

By G. Sachs, B. B. Muvdi, E. P. Klier

IT is now generally i-ecognized that hydrogen is responsible for delayed failures encountered in high-strength steels,'.' and the hydrogen responsible for the embrittlement is introduced in the cathodic cleaning and plating operations to which these steels are subjected. Numerous test methods have been used in the past for the determination of brittleness in embrittled parts, namely tension? = notch-tension:' impact,' stress-rupture: a and bend tests.% * Several of these tests are not suitable for routine testing.

Jan 1, 1958

By P. R. Kalischer

IN the production of alloys by powder metallurgical processes it is often necessary or desirable to include one or more components that tend to form very stable oxides Included in this group of metals are aluminum, manganese, magnesium, silicon, and a few others In many cases it is not necessary for the sintered compact to have full density and the other physical characteristics of a cast alloy and in that event no undue precautions need be taken If, however, it s required that the sintered part be entirely homogeneous, and have maximum density and physical properties, some method must be found to reduce the surface films of oxide, which are always present on the metals, and for the metals mentioned above this is always extremely difficult, if not impossible Since the production of high-density alloys is of particular interest to powder metallurgists, some experiments were undertaken to devise methods of reducing the refractory oxides For this work, alloys of iron, nickel, and aluminum were chosen because aluminum oxide is one of the most stable oxides and because these alloys in the right compositions form excellent permanent magnets All of the pertinent properties of the magnets could be accurately and delicately measured by density measurements and magnetic tests of sufficient scope to give a complete demagnetization curve From such a curve the maximum coercive force, residual magnetism, and energy products could be obtained and compared with the same properties for a cast material Any lack of homogeneity, density, or solid diffusion would be immediately apparent as a decrease in the magnetic properties NATURE AND REMOVAL OF SURFACE BARRIERS The early work of the present investigation was based upon published processes In the published information it was claimed that by intimately mixing iron, nickel, and iron-aluminum alloy (50 per cent Fe, 50 per cent Al) powders, compressing such a mixture into the desired shape and size, and then sintering (heating to a temperature below the melting point of the component metals) in hydrogen at 1200ºC or higher, a sound, homogeneous article could be made having the desired physical size, shape, and strength, and good magnetic characteristics However, this early work showed clearly that something in the powder compress was inhibiting diffusion and the process was almost entirely unworkable In the initial phase of the investigation samples of iron powder, nickel powder, and iron-aluminum alloy powder were pressed into separate bars and sintered in hydrogen Both the iron and nickel powders sintered

Jan 1, 1941

By J. M. Gaines, C. H. Herty, M. W. Lightner, H. Freeman

Few subjects have attracted the attention of metallurgists more than oxygen in steel. From the days of Mushet and Ledebur interest in this subject has been increasing, and as additional knowledge has become available, the problem has naturally grown more complex. Instead of using the simple term "oxygen" we now distinguish between iron oxide, silicates of various kinds, oxysulfides, oxygen as gas and oxygen in solid solution in steel. There are five general methods for determining oxides in steel: hydrogen reduction; vacuum fusion; various wet-extraction methods, including electrolytic methods; methods depending on volatilization of the iron away from the oxides; and metallographic methods. For oxygen in solid steel each of these methods has both advantages and disadvantages. The hydrogen-reduction method is of no use on steels above about 0.20 per cent. carbon;' furthermore, it gives only FeO and possibly some MnO. The vacuum-fusion method2 is expensive and gives total oxygen, with the exception of some A12O3, and does not differentiate between the various oxides in which the oxygen exists. Most of the wet extraction methods3 give only the more insoluble oxides SiO2 and A12O3, though the iodine method gives MnO to an uncertain degree (information that may be more misleading than no information

Jan 1, 1930

By Carle Hayward

AT THE February, 1916, meeting of the Institute, a paper presented by Hayward and Raymond gave the results of a study on the effect of time in tempering medium-carbon steel, when the following conclusions were reached: It is not fair to consider the question settled when only three specimens were used for each treatment, but the results obtained indicate that for reheating quenched medium-carbon steel to temperatures below 500° it is only necessary to heat it through. Longer heating has little or no effect on the tensile strength, ductility, or hardness. At temperatures above 500°, increasing the time of treatment causes a slight falling off in hardness and tensile strength with a corresponding increase in ductility. In the discussion of the paper these conclusions were attacked and evidence presented that seemed to throw doubt on their accuracy. The authors, however, showed that this evidence was based on high-carbon or alloy steels and no facts regarding medium-carbon steel were presented. During this study the heat treatment was carried out in a small electric resistance furnace. It held nine specimens, but when these were placed in the furnace the temperature was lowered to such an extent that 30 to 40 min. were required to reach the desired heat. The authors pointed to this as a weak point in the investigation and it seemed wise to supplement the research by work on similar steel but using a different method of heating. This has been done and the results are given in the present paper. The Rhode Island Tool Co. cooperated by furnishing the steel and turning the tensile specimens.

Jan 1, 1922

By A. R. Troiano, E. A. Steigerwald, F. W. Schaller

The initiation of localized cracking in hydrogenated high strength steel was dependent on the developmeni of a critical hydrogen conceniration and relatively insensitive to the magnitude of the applied stress. The stress was believed to influence the deluyed failure process by providing the means for grouping the hydrogen. On the basis of an assumed distribution law the observed changes in the lower critical stress as a function of notch acuity, yield strength, and temperature were predictable over a significant range of these variables. THE phenomenological characteristics of delayed failure in high-strength steel have been comprehensively investigated and the behavior has been attributed to the strong embrittling action of hydrogen.1-3 Delayed failure or, as it is also termed, static fatigue, is the most sensitive means of detecting hydrogen embrittlement since it allows the maximum time for hydrogen diffusion during a test.3 The nature of delayed failure cail be aptly described by four parameters which are schematically depicted in Fig. 1. The upper critical stress corresponds to the rupture stress in a conventional notch tensile test. The lower critical stress or static fatigue limit is the stress below which no delayed failure will occur. The incubation period is the time required for the formation of the first crack and the fourth parameter is the failure time. An increase in hydrogen content, notch acuity, or strength level of the material increases the susceptibility for delayed failure by decreasing the lower critical stress, the incubation period, and the time to failure.lY3 A decrease in test temperature prolongs the incubation period in accordance with the lower diffusion rate of hydrogen, and also de-

Jan 1, 1961

By Clair Upthegrove, Elbert S. Rowland

THE widespread interest in the alloys of beryllium with copper is due principally to the fact that certain compositions show very favorable precipitation-hardening characteristics and are, in fact, the strongest nonferrous alloys known at the present time. Investigations have been conducted by Masing and Dahl and others on the physical characteristics of ternary beryllium alloys, in an attempt to produce precipitation-hardening effects with a smaller amount of beryllium than that required in the binary copper-beryllium alloys (2.0 to 2.5 per cent Be). The results of these investigations show that ternary alloys of beryllium with Cu-Sn, Cu-Al and Cu-Zn, among others, exhibit promising improvements in physical properties after precipitation-hardening treatment and, while the increases in properties obtained are not as high as those realized from the binary copper-beryllium alloys, excellent properties are: obtained with beryllium contents averaging about one-half the amount required in the binary alloys. This paper presents the results of an investigation of the equilibrium relations of certain alloys containing copper, tin and beryllium. The alpha-phase boundary of the ternary system is given for alloys containing from. 0 to 1 per cent beryllium. The equilibrium conditions beyond the alpha-phase boundary are presented for alloys containing up to 32 per cent tin and 1 per cent beryllium. The data were collected by means of

Jan 1, 1935

By C. D. Keen

IN the latter part of the summer of 1913 the Conservation Commission of the State of Louisiana, under presidency of M. L. Alexander, decided to stop the waste of natural gas going on at the "burning gas-well," located about 3/4 mile southeast of Oil City, La. On several occasions, both in newspapers and in reports, comment had been made on the condition of this well, its harmful effect on the Caddo gas field, and the considerable loss, estimated at several thousand dollars each month, caused by the escape of the valuable fuel. But nothing had been done to bring the well under control and prevent further waste of gas until the State Conservation Commission took the matter in hand. The gas fields of Louisiana are among the greatest in the country. So far most of the gas has been found in the Caddo field proper, although considerable development has been done in and around the city of Shreveport and near the town of Mansfield in DeSoto parish. To extend the life of the gas fields and to prevent the quick exhaustion of the supply of the natural fuel are matters of vital importance for this section of the country. Four gas companies have entered the Caddo field and supply the surrounding towns and cities with gas. The Arkansas Natural Gas Co. has pipe lines to Little Rock, Ark., and supplies gas to the following cities and towns in that State: Texarkana, Hope, Garland, Emmet, Prescott, Boughton, Beirne, Gurdon, Arkadelphia, Gum Springs, Malvern, Donaldson, Gifford, Perla,- Beaton, Beauxite, Mabelvale, Bryant, Sheridan, Pine Bluff, Little Rock, Argenta, Pulaski Heights, and Hot Springs. The Southwestern Gas & Electric Co. transports gas to Mooringsport, Blanchard, Caddo, Rodessa, Oil City, Vivian, Bloomburg, Hosston, Ida, Dixie, Belcher, and Shreveport. The Marshall Gas Co. supplies gas to the town of Marshall, Texas. The Louisiana Co. has a line to Shreveport.

Jan 3, 1914

By L. J. Buck

Lead smelting in the ore hearth, first practiced in Europe, whence the traditional name "Scotch hearth, and later developed in America to its present efficiency, is based upon the roast reduction process and is applicable to relatively high-grade galena concentrates. The roast reduction process embraces not only the roast reactions: 2PbS + 70 = PbO + PbSO4, + SO2 PbS + 2PbO = 3Pb + SO2 PbS + 2PbSO4 = Pb + 2PbO + 3SO2 but also, by reason of the addition of extraneous fuel, the reduction reaction: 2PbO + C = 2Pb + CO2 Thus in the ore hearth the roasting of lead sulphide, forming lead oxide and lead sulphate, the reaction of lead oxide and lead sulphate with lead sulphide producing lead, and the reduction of lead oxide by carbon producing lead, go on simultaneously. The Ore Hearth Function of the Ore Hearth.—The ore hearth, through the roast reduction process, provides for the extraction of lead and the immediate disposal of the smelting products—fume, hearth slag and lead, all of which are subsequently treated as follows: the fume is recovered in the flue system and baghouses, mixed with concentrates, and returned to the ore hearth in the form of ore mix; the hearth slag is smelted in a blast furnacc for the further recovery of lead; and the lead is refined and cast into a marketable product. Concentrates Amenable to Ore-hearth Smelting.—Only concentrates that are high in lead content, 70 per cent or more, are ordinarily considered amenable to ore-hearth smelting. Silica should not exceed 2 per cent and iron is allowable only to 4 per cent. These slag-forming constituents occlude both sulphide and mctallic lead, prevent the elimination of sulphur and decrease the lead extraction. Lime and magnesia are beneficial in that both favor a dry slag, promote elimination of sulphur, and prevent occlusions of metallic lead.

Jan 1, 1937

By Frederick N. Rhines, Robert F. Mehl

It has been shown elsewhere1 that the data on the rates of diffusion in solid metals are fragmentary and in many cases unacceptable. As a result, relatively little is known concerning the factors determining rates of diffusion and the variations in these rates with temperature. The first form of Fick's law (equation 1 below), in which the diffusion coefficient D is assumed invariant with composition, has been recognized for many years as only an approximation. The differential equation representing the second form of Fick's law (equation 4 below) has only recently been integrated by Matano,2 and unfortunately only in cases where a full diffusion-penetration curve (concentration-distance curve) has been obtained can the Matano solution be applied. The proper analysis of diffusion data is thus confined to the data of Grube and Jedele and of Jedele. 8 These data are essentially for one temperature alone and do not furnish any information on the variation of the activation heat of diffusion, Q, with concentration: no information exists on the variation of Q with concentration within a single solid solution field. 11 Much of the argument concerning the properties of metals that determine D and Q has been drawn from data in which variations of the quantities with concentration are unknown, for these data have been taken from experiments that could not furnish this information. Speculation concerning the properties of metals that may be effective in determining D and Q on the basis of data in which the chosen D and Q values are averages over wide concentration ranges of values at particular concentrations, ranges often of 100 per cent, is likely not to be fruitful.

Jan 1, 1938

By H. J. Hand

Statistical methods are becoming increasingly important for interpreting routine reports, or for analyzing special test data in industrial plants, such as steel plants. They have already become practically a necessity to the plant metallurgist. A paper by Chancellor, 1 written in 1933, gives many examples of the benefits the plant metallurgist can derive from the use of these methods. The present paper discusses applications of importance to many others who must analyze reports in the steel plant, as well as other examples of interest to metallurgists. Statistical Methods Logically Suited to Plant Problems.—Statistical methods are not new as a branch of mathematics. Until comparatively recently, however, practical applications were confined mainly to actuarial science, biology, and economics; fields in which an observed result is obviously influenced (and often determined) by a complicated set of variables more or less constantly tending to affect it. As pointed out by Daeves,2 a decade or more ago, problems in industry are basically similar to those in these other fields in that a given result is at least partly due to that chance combination of causes happening to be present at the time. When trying to do the same thing repeatedly, constant results are never attained; they vary about the desired result with more or less well defined mathematical regularity. Such a condition arises out of the great number of factors tending to affect the final result. If statistical methods are so valuable to the biologist or economist, why then should they not also be of great value to plant managers and engineers, and to all who must interpret reports from various sources in the industrial plant? Within the last few years, industry has become conscious of this situation, and the use of these methods has been rapidly expanding in such p1ants. Many Useful Statistical Devices Available.—Many statistical methods of attack are available for the analysis of plant data. It is the object of

Jan 1, 1938

By Edgar R. Kendall

A knowledge of the fundamental principles of locating, sampling, testing and evaluating materials is essential in prospecting for mineral aggregates. In this discussion, mineral aggregates will be considered sand, gravel, crushed stone and slag that are used as materials of construction. The quantity of mineral aggregates produced in the United States during the year 1935 for such purposes was roughly 165,000,000 tons, about 60 per cent of which was sand and gravel, 37 per cent crushed stone and 3 per cent crushed slag. The total value of this material was approximately $100,000,000. It is apparent therefore that the prospecting for suitable mineral aggregates is of considerable economic importance. In prospecting for mineral aggregates, the methods employed are the same whether the organization is large or small. In the large organization there may be available geologists for locating sources of supply, a land acquisition department to arrange for the necessary options or permits, engineers to do the sampling, a laboratory for testing, and a board of consulting materials engineers to make the final selection. Even small organizations must follow the same general procedure, though the responsibility for the selection of aggregates may rest with one man, who may or may not be an engineer, but who must depend entirely upon his own judgment. Locating the Supply The initial step in prospecting for mineral aggregates is the locating of suitable, adequate and economic sources of supply for the project in mind. Commercial plants in the vicinity should be investigated and a survey made of the existing structures that have been built of aggregates from these sources. If the structures are rather old and show no signs of deterioration, it is fairly good evidence that the aggregate is satisfactory. If materials of the proper quality can be obtained from commercial sources in sufficient quantity, and delivered to the job economically, it

Jan 1, 1942

By Frederick N. Rhines, Robert F. Mehl

It has been shown elsewhere1 that the data on the rates of diffusion in solid metals are fragmentary and in many cases unacceptable. As a result, relatively little is known concerning the factors determining rates of diffusion and the variations in these rates with temperature. The first form of Fick's law (equation 1 below), in which the diffusion coefficient D is assumed invariant with composition, has been recognized for many years as only an approximation. The differential equation representing the second form of Fick's law (equation 4 below) has only recently been integrated by Matano,2 and unfortunately only in cases where a full diffusion-penetration curve (concentration-distance curve) has been obtained can the Matano solution be applied. The proper analysis of diffusion data is thus confined to the data of Grube and Jedele and of Jedele. 8 These data are essentially for one temperature alone and do not furnish any information on the variation of the activation heat of diffusion, Q, with concentration: no information exists on the variation of Q with concentration within a single solid solution field. 11 Much of the argument concerning the properties of metals that determine D and Q has been drawn from data in which variations of the quantities with concentration are unknown, for these data have been taken from experiments that could not furnish this information. Speculation concerning the properties of metals that may be effective in determining D and Q on the basis of data in which the chosen D and Q values are averages over wide concentration ranges of values at particular concentrations, ranges often of 100 per cent, is likely not to be fruitful.

Jan 1, 1938

By Edgar R. Kendall

A knowledge of the fundamental principles of locating, sampling, testing and evaluating materials is essential in prospecting for mineral aggregates. In this discussion, mineral aggregates will be considered sand, gravel, crushed stone and slag that are used as materials of construction. The quantity of mineral aggregates produced in the United States during the year 1935 for such purposes was roughly 165,000,000 tons, about 60 per cent of which was sand and gravel, 37 per cent crushed stone and 3 per cent crushed slag. The total value of this material was approximately $100,000,000. It is apparent therefore that the prospecting for suitable mineral aggregates is of considerable economic importance. In prospecting for mineral aggregates, the methods employed are the same whether the organization is large or small. In the large organization there may be available geologists for locating sources of supply, a land acquisition department to arrange for the necessary options or permits, engineers to do the sampling, a laboratory for testing, and a board of consulting materials engineers to make the final selection. Even small organizations must follow the same general procedure, though the responsibility for the selection of aggregates may rest with one man, who may or may not be an engineer, but who must depend entirely upon his own judgment. Locating the Supply The initial step in prospecting for mineral aggregates is the locating of suitable, adequate and economic sources of supply for the project in mind. Commercial plants in the vicinity should be investigated and a survey made of the existing structures that have been built of aggregates from these sources. If the structures are rather old and show no signs of deterioration, it is fairly good evidence that the aggregate is satisfactory. If materials of the proper quality can be obtained from commercial sources in sufficient quantity, and delivered to the job economically, it

Jan 1, 1942

By H. J. Hand

Statistical methods are becoming increasingly important for interpreting routine reports, or for analyzing special test data in industrial plants, such as steel plants. They have already become practically a necessity to the plant metallurgist. A paper by Chancellor, 1 written in 1933, gives many examples of the benefits the plant metallurgist can derive from the use of these methods. The present paper discusses applications of importance to many others who must analyze reports in the steel plant, as well as other examples of interest to metallurgists. Statistical Methods Logically Suited to Plant Problems.—Statistical methods are not new as a branch of mathematics. Until comparatively recently, however, practical applications were confined mainly to actuarial science, biology, and economics; fields in which an observed result is obviously influenced (and often determined) by a complicated set of variables more or less constantly tending to affect it. As pointed out by Daeves,2 a decade or more ago, problems in industry are basically similar to those in these other fields in that a given result is at least partly due to that chance combination of causes happening to be present at the time. When trying to do the same thing repeatedly, constant results are never attained; they vary about the desired result with more or less well defined mathematical regularity. Such a condition arises out of the great number of factors tending to affect the final result. If statistical methods are so valuable to the biologist or economist, why then should they not also be of great value to plant managers and engineers, and to all who must interpret reports from various sources in the industrial plant? Within the last few years, industry has become conscious of this situation, and the use of these methods has been rapidly expanding in such p1ants. Many Useful Statistical Devices Available.—Many statistical methods of attack are available for the analysis of plant data. It is the object of

Jan 1, 1938

By L. G. Huntley

Discussion of the paper of L. G. HUNTLEY,. presented at the San Francisco meeting, September, 1915, and printed in Bulletin No. 102, June, 1915, pp. 1333 to 1349. E. W. SHAW, Washington, D. C. (communication to the Secretary*). -The comparatively great extent and uniform character of the Dakota sandstone make it of great interest to the student of rock pores and the movements of their fluid contents. However, compared with other sands in areas of carbonaceous rocks facts concerning it do not seem to be of such great direct importance to the producer for it has thus far yielded few important pools of oil or gas. Information concerning the sandstone is extensive but scattered, hence a general treatise regarding it-particularly its pores, the fluids they contain, and the movements of the fluids-has been much needed. I therefore feel that the. chief thing to be ,desired concerning Mr. Huntley's paper is that it were more extended, particularly as to the discussion of the data presented. The general structure map of the Dakota is of especial interest. Slight changes in wording seem to be desirable here and there in the paper. For example, at the beginning of the third paragraph one-wonders if flora instead of fauna were not intended. In Figs. 2, 3, 4, and 5 the vertical scale seems incorrect. Concerning the analyses of oil quoted it is noted that they "are given, as indicating what may be expected in different localities." This seems to need modification for the average analysis of oil from Powder River, which indicates for example that this oil begins to boil at 213°C. The fact is that the samples to which this figure refers were taken from seeps long exposed. to the air :find hence the underground Dakota oil of this district no doubt differs profoundly from that which the analysis indicates. The product of a well here would probably differ more in boiling point and other. respects from the samples analyzed than it would from almost any other petroleum in the world. The use of the word synclinorium does not conform to the original definition, but this may be pardonable because misuse of the term, though a different misuse, has become general. Synclinorium is an orographic term and cannot be correctly applied outside of mountain regions, for it is derived in part from the Greek word for mountain. It has, however, been widely used in a purely structural sense for compound syncline. The broad shallow syncline of the Dakota sandstone falls in neither category. Objection might also be made to the use of

Jan 12, 1915

By V. S. Gupt, W. H. Somerton

Rock may undergo great changes in physical properties when heated to high temperatures and then cooled, The temperature and intensity of reactions causing rock alterntiorl.s can he controlled by introducing certain chemicals during heat treament. Three typical outcrop sandsone samples were saturuted with common salt solutions, then heated to several maximum temperatures. After cooling, it was found that per-rrreuhilities had increased much more for salt-saturated samples than for samples not saturated with salt but heated to the same temperatures. This was only true, however. for samples heated above the melting points of the particrrlar salts. Potassium chloritle was particularly effective with Bandera sandstone. Samples saturated with potassium chlorirlr. solution and heated to 900C showed an 11-fold increa.se in perrrieahility. Samples without potasrirdrn chloritle but heated to the .same temperature. showed only a 2.7-jold incresre in permecahility. In application, it seems possible that injecting chemicalc into the formations from a wellbore followed by applying intensive borehole heating might promote reactions which would greatly improve permeability of the formalions. INTRODUCTION Great changes in the physical properties of rocks which have been heated to temperatures in the range of 600 to 800C have been reported earlier. Permeability increases of 50 per cent, and equivalent decreases in sonic velocity and breaking strength have been observed. Although there might be some suppression of certain reactions responsiblc for these changes when rock samples are heated under simulated reservoir pressure conditions. recent work has shown that these are more than offset by the increased importance of other reactions at high pressures. The reactions considered responsible for alteration of rock properties by heating include differential thermal expansion. dehydration, phase changes and dissociation of mineral constituents. Ceramists have long known that temperatures at which reactions occur can be raised or lowered by the presence of certain impurities in the sys. tcnl. Thus the possibility exists that by saturating rocks with appropriate solutions. desired reactions might be accelerated and unwanted reactions might be suppressec! when the rock is heated. Purpose of the present work was to investigate the effects of several common salts on the thermal alteration of sandstones. Types of reactions which might occur are reviewed and the findings of a number of thernlochemical alteration tests are presented. THEKMOCHEMICAL ALTERATION OF SANDSTONE MINERALS The most abundant constituent of most sandstones is quartz. Quartz can exist in at least eight different forms, but in the temperature range of immediate interest (to 900C) only two forms are of importance—alpha quartz below 573C and beta quartz above this temperature. Although the alpha-beta inversion of quartz is very important in thermal alteration of rocks. it is not particularly important here because the inversion temperature cannot be changed significantly by the presence of impurities or by the application of pressure. The transition temperature of quartz to tridynlite is 867C. but the transition is very sluggish. Tridymite is considered to be a metastable transition phase between two stable phases: quartz?cristobalite. However. the transition temperature for tridymite to cristobalite is 1,470C.4 The quartz-tridymite-cristobalite transition can be accelerated substantially by the presence of fluxing agents. Finely divided calcium, magnesium and titanium oxides accelerate the conversion while A12O may retard it. A Mixture of NaCl and CsCl reduces the temperature for cristobalite formation by as much as 420°C. Feldspars constitute the second most important mineral in sandstones. The melting points of feldspars range between 1,000 and 1,700°C depending upon the variety. No information available indicated any important role of fluxing agents in the thermal alteration of this group of minerals. Carbonate minerals are subject to dissociation at temperatures within the range of the present investigation. The dissociation of magnesite can start at a temperature of 373°C, but the reaction is sluggish and might not occur untll a temperature of 500°C or ,higher is reached. Dolomite dissociates in two stages at 500°C and 890°C, whereas calcite dissociation temperature is about 885C. Because CO2 is released in the dissociation of carbonates, ail such reactions are somewhat dependent upon CO2 partial pressure. In the absence of CO: in the surrounding atmosphere, the dissociation of calcite starts at 500°C.However. when 1 atm of CO surrounds the sample, the dissociation does not start until 900C. The other carbonates are apparently much less sensitive to a change in partial pressure of CO2. The aragonite calcite transformation can occur an!. where within the temperature range of 357 to 488°C. depending upon the presence of impurities such as barium. strontium. lead and perhaps zinc. The differential thermal analysis (DTA) curves of both magnesitc and dolomite vary with the presence of 'impuritics. The presence of iron in particular seems to affect the magnesitc DTA curve

Jan 1, 1966

By P. R. Kalischer

IN the production of alloys by powder metallurgical processes it is often necessary or desirable to include one or more components that tend to form very stable oxides. Included in this group of metals are aluminum, manganese, magnesium, silicon, and a few others. In many cases it is not necessary for the sintered compact to have full density and the other physical characteristics of a cast alloy and in that event no undue precautions need be taken. If, however, it is required that the sintered part be entirely homogeneous, and have maximum density and physical properties, some method must be found to reduce the surface films of oxide, which are always present on the metals, and for the metals mentioned above this is always extremely difficult, if not impossible. Since the production of high-density alloys is of particular interest to powder metallurgists, some experiments were undertaken to devise methods of reducing the refractory oxides. For this work, alloys of iron, nickel, and aluminum were chosen because aluminum oxide is one of the most stable oxides and because these alloys in the right compositions form excellent permanent magnets. All of the pertinent properties of the magnets could be accurately and delicately measured by density measurements and magnetic tests of sufficient scope to give a complete demagnetization curve. From such a curve the maximum coercive force, residual magnetism, and energy products could be obtained and compared with the same properties for a cast material. Any lack of homogeneity, density, or solid diffusion would be immediately apparent as a decrease in the magnetic properties. NATURE AND REMOVAL OF SURFACE BARRIERS The early work of the present investigation was based upon published processes.* In the published information it was claimed that by intimately mixing iron, nickel, and iron-aluminum alloy (50 per cent Fe, 50 per cent Al) powders, compressing such a mixture into the desired shape and size, and then sintering (heating to a temperature below the melting point of the component metals) in hydrogen at 1200°C. or higher, a sound, homogeneous article could be made having the desired physical size, shape, and strength, and good magnetic characteristics. However, this early work showed clearly that something in the powder compress was inhibiting diffusion and the process was almost entirely unworkable. In the initial phase of the investigation samples of iron powder, nickel powder, and iron-aluminum alloy powder were pressed into separate bars and sintered in hydrogen. Both the iron and nickel powders sintered

Jan 1, 1941

By B. Haimson, C. Fairhurst

A criterion is Proposed for the initiation of vertical hydraulic fracturing taking into consideration the three stress fields around the wellbore. These fields arise from (1) nonhydrostatic regional stresses in earth, (2) the difference between the fluid pressure in the wellbore and the formation fluid pressure and (3) the radial fluid flow through porous rock from the wellbore into the formation due to this pressure difference. The wellbore fluid pressure required to initiate a fracture (assuming elastic rock and a smooth wellbore wall) is a function of the porous elastic constants of the rock, the two unequal horizontal principal regional stresses, the tensile strength of the rock and the formation fluid pressure. A constant injection rate will extend the fracture to a point where equilibrium is reached and then, to keep the fracture open, the pressure required is a function of the porous elastic constants of the rock, the component of the regional stress normal to the plane of the fracture, the formation fluid pressure and the dimensions of the crack. The same expression may also be used to estimate the vertical fracture width, provided all other variables are known. The derived equations for the initiation and extension pressures in vertical fracturing may be employed to solve for the two horizontal, regional, principal stresses in the rock. INTRODUCTION Well stimulation by hydraulic fracturing is a common practice today in the petroleum industry. However, this stimulation process is not a guaranteed success; hence, the deep interest shown by the petroleum companies in better understanding the mechanism that brings about rock fracturing, fracture extension and productivity increase. Geologists and mining people became interested in hydraulic fracturing from a different point of view: the method may possibly be employed to determine the magnitude and direction of the principal stresses of great depth. Numerous articles in past years have dealt with the theory of hydraulic fracturing, but they all seem to underestimate the effect of stresses around the wellbore due to penetration of some of the injected fluid into the porous formation.1-4 Excellent papers on stresses in porous materials due to fluid flow have been published5,6 but no real attempt has been made to show the effect of these stresses in the form of a more complete criterion for vertical hydraulic fracturing initiation and extension. This paper is such an attempt. ASSUMPTIONS It is assumed that rock in the oil-bearing formation is elastic, porous, isotropic and homogeneous. The formation is under a nonhydrostatic state of regional stress with one of the principal regional stresses acting parallel to the vertical axis of the wellbore. This assumption is justified in areas where rock formations do not dip at steep angles and where the surface of the earth is relatively flat. This vertical principal regional stress equals the pressure of the overlying rock, i.e., S33 = —pD, where S33 is the total vertical principal stress (positive for tension), p is average density of the overlying material and D is the depth of the point where S33 is calculated. The wellbore wall in the formation is considered to be smooth and circular in cross-section. The fluid flow through the porous elastic rock obeys Darcy's law. The whole medium is looked upon as an infinitely long cylinder with its axis along the axis of the wellbore. The radius of the cylinder is also very large. Over the range of depth at which the oil-bearing formation occurs, it will be assumed that any horizontal cross-section of the cylinder is subjected to the same stress distribution, and likewise that it will deform in the same manner. STATE OF STRESS PRIOR TO DRILLING OF WELLBORE At a depth D from the earth surface within the oil-bearing strata, it is assumed that the following are 1References given at end of paper.

By J. Orkiszewski

A method i.s presented which can accurately predict, with a precision of about 10 percent, two-phase pressure drops in flowing and gas-lift production wells over a wide range of well conditions. The method is an extension of the work done by Grifith and Wallis and was found to be superior to five other published methods. The precision of the method was verified when its predicted values were compared against 148 measured pressure drops. The unique features of this method over most others are that liquid holdup is derived from observed physical phenomena, the pressure gradient is related to the geometrical distribution of the liquid and gas phase (flow regimes), and the method provides a good analogy of what happens inside the pipe. It takes less than a second to obtain a prediction on the IBM 7044 computer. INTRODUCTION The problem of accurately predicting pressure drops in flowing or gas-lift wells has given rise to many specialized solutions for limited conditions, but not to any generally accepted one for broad conditions. The reason for these many solutions is that the two-phase flow is complex and difficult to analyze even for the limited conditions studied. Under some conditions, the gas moves at a much higher velocity than the liquid. As a result, the down-hole flowing density of the gas-liquid mixture is greater than the corresponding density, corrected for down-hole temperature and pressure, that would be calculated from the produced gas-liquid ratio. Also, the liquid's velocity along the pipe wall can vary appreciably over a short distance and result in a variable friction loss. Under other conditions, the liquid is almost completely entrained in the gas and has very little effect on the wall friction loss. The difference in velocity and the geometry of the two phases strongly influence pressure drop. These factors provide the basis for categorizing two-phase flow. The generally accepted categories (flow regimes) of two-phase flow are bubble, slug, (slug-annular) transition and annular-mist They are ideally depicted in Fig. 1 and briefly described as follows. RUBBLE FLOW (FIG. 1A) The pipe is almost completely filled with the liquid and the free-gas phase is small. The gas is present as small bubbles, randomly distributed, whose diameters also vary randomly. The bubbles move at different velocities depending upon their respective diameters. The liquid moves up the pipe at a fairly uniform velocity and, except for its density, the gas phase has little effect on the pressure gradient. SLUG FLOW (FIG. 1R) In this regime, the gas phase is more pronounced. Although the liquid phase is still continuous, the gas bubbler coalesce and form stable bubbles of approximately the rame size and shape which are nearly the diameter of the pipe. They are separated by slugs of liquid. The bubble velocity is greater than that of the liquid and can be predicted in relation to the velocity of the liquid slug." There is a film of liquid around the gas bubble. The liquid velocity is not constant—whereas the liquid slug always moves upward (in the direction of bulk flow); the liquid in the film may move upward but possibly at a lower velocity, or it may move downward. These varying liquid velocities will result not only in varying wall friction losses, but also in a "liquid holdup" which will influence flowing density. At higher flow velocities, liquid can even be entrained in the gas bubbles. Both the gas and liquid phases have significant effects on the pressure gradient. TRANSITION FLOW (FIG. 1C) The change from a continuous liquid phase to a continuous gas phase occurs in this region. The liquid slug between the bubbles virtually disappears, and a significant amount of liquid becomes entrained in the gas phase. Although the effects of the liquid are significant, the gas phase is more predominant.

By T. C. M. Pillay, John Chipman

The Si-0 equilibrium in liquid iron was investigated in some detail by Gokcen and Chipman1 who reported equilibrium constants of the following reactions: In each case the thermodynamic equilibrium constant K was obtained by extrapolating K' to infinite dilution. Their results on reaction [I] were consistent with those of earlier observers, and there seems to be little doubt as to the approximate validity of the equilibrium product determined. On the other hand, the results on reactions [2] and [3] indicated unusual curvilinear relationships between the activity coefficients of silicon and of oxygen and the silicon concentration. Since a linear relation is observed in all other similar instances, it was concluded that some source of error had affected the gas-metal equilibrium relationships. Recently the authors undertook a restudy of these equilibria with the view especially to establishing the equilibrium constant of reaction [2]. Their experiments, however, were discontinued before a tbroughly satisfactory answer had been obtained and consequently have remained unpublished until the present time. Quite recently Matoba, Gunji, and Kuwana2 published the results of a very thorough study of these equilibria. It is the purpose of the present note to Compare these three sets of experimental data, a comparison which leads to Confirmation of the results of Matoba and coworkers. The experimental arrangements described by Dutilloy and Chipman were employed. A controlled mixture of Hz, H,0, and argon was led into the induction furnace over the surface of the Fe-Si melt contained in a silica crucible. On account of the slow approach to equilibrium, runs were continued for at least 8 hr and, in some cases, as much as 12 hr. Samples were taken by means of silica tubes at the start and during the final 4-hr period of each run. Out of twelve runs only seven appeared to have approached equilibrium with sufficient certainty to be reported here. The results of these experiments, all at 1600°c, are shown by the triangles in Fig. 1. Equilibrium was approached from both oxidizing and reducing conditions and the direction of approach is indicated by the shape of the triangle. Attempts to extend the study to higher silicon concentrations were unsuccessful on account of the transfer of silica from the metal bath to the upper portions of the crucible by means of a silicon-monoxide mechanism. Matoba, Gunji, and Kuwana used similar methods and approached equilibrium from both sides. Their results at three temperatures are shown by the solid lines of Fig. 1. A line corresponding to 1600 deg is interpolated from their equations and is shown by the dotted line. The results of Gokcen and Chipman at 1600 deg in the range 0.02 to 2.0 pct Si are also shown. At concentrations up to about 0.6 pct Si, these investigators approached equilibrium from both directions, and their results in this range appear to be trustworthy. Above 1 pct Si, however, all of their experiments involved oxidation only, as shown by a decrease in the silicon content of the bath. It now seems certain that they failed to reach equilibrium at these higher silicon concentrations and that the curvilinear relation shown by their results is incorrect. It is evident that their results in the lower silicon range are in good agreement with those of Matoba and coworkers. In fact, a straight line drawn through their results would parallel the dotted line and would differ from it by only 0.05 in log K. The new data also lie close to that line. It may thus be concluded that the three sets of data are in good agreement and that the equations proposed by Matoba and coworkers for reaction [2] are satisfactory . They take the limiting value of log K', at 0 pct Si as log K ,. The slope of each line gives the value

Jan 1, 1962