Search Documents

By AIME AIME

WTHIN the next month all members of the Institute will be given an opportunity to vote for a new President, two Vice-Presidents, and five Directors. All of the candidates nominated by the official committee are well known to certain groups of the Institute membership but a brief record of their professional lives will be given here for the information of those that will vote. Not since 1927, when Everette DeGolyer guided the destinies of the Institute, has a member of the Petroleum Division been a candidate for President. John Meston Lovejoy has been a Director since 1930, and a Vice-President as well for the last year: In the three years 1932-4 lie was also chairman of the Admissions Committee. Dir. Lovejoy graduated from the Columbia School of Mines in 1911, just before lie was 22 years old, and began his professional career as a copper miner at Chuquicamata. Chile. Silver and gold mining later claimed his % attention, and it was not until 1914 that lie gut into the oil business, as geologist for the Standard Oil Co. of N. Y. This took hint to China and he later worked for the company in Wyoming. In 1917 lie joined the Army where lie rose to be captain of Field Artillery. Upon his return to the United States he went to work for the Amerada Petroleum Co., of which he later became vice-president and general manager, with headquarters in Tulsa. Since coining to New York he has been president of the Petroleum Bond & Share Cu.. and is currently president of the Seaboard Oil Co.

Jan 1, 1935

By Elmer W. Pehrson

The term "survival" in the title means the preservation of a society in which men are free from the political and economic restraints that characterize totalitarian systems, be they communist, socialist or facist. It means the ability to withstand the enemy's offensives in the fields of propaganda, commercial competition and, if necessary, war. The temptation to substitute "victory" for "survival" is great but a realistic appraisal of the creeping socialism and demagoguery that pervade our time indicates that we may have to be content with survival in status quo. "Mineral strength" means assurance that adequate supplies will be available to meet all the contingencies of cold and hot wars. The overall mineral position of the U. S. viewed in the light of these premises is far from secure. It is true that we are the leading producing and consuming nation of the world, but the Soviet Union is gaining and the Sino-Soviet Bloc confronts us with a sobering potential. The emergence of the Common Market in Europe as an economic and political unit places a third independent entity into the competition. Our total mineral output continues on an up- ward trend but the reverse is true in certain strategic commodities. Moreover, consumption is moving ahead faster than production so that there is increasing dependence on imports which has significant adverse geopolitical connotations. There is widespread belief that our resources can at least maintain present levels of self-sufficiency during this critical period in world history, but social dreamers, the labor monopoly, and trade and taxation policies have discouraged aggressive activity in exploration and development, and access to essential foreign sources is threatened by a variety of circumstances. Our stockpiles, belatedly built up to achieve minimum protection against shortages in time of war, are under. political attack and threatened with partial destruction on the basis of what are at best uncertain assumptions regarding the new: look of global warfare.

Jan 11, 1962

By Jay R. Burns

Two magnesium sand-casting alloys are commonly favored in the United States. These are referred to as H and C alloys (Dow Chemical Co.) or AM265 and AM260 alloys (American Magnesium Corporation). Both are of an aluminum-zinc-manganese type. H alloy contains 6 per cent aluminum and 3 per cent zinc and is characterized by relatively good toughness. C alloy contains g per cent aluminum and 2 per cent zinc and is employed where high yield strength and pressure tightness are required. Examination of magnesium castings poured in Europe and England,1,2 however, demonstrates that H and C alloys are replaced by A8 and AZ91, respectively. That is, A8 represents a magnesium alloy having superior toughness while AZ91 is suitable for high yield strength and pressure-tight applications. The basic difference between the American and European alloys is that the foreign alloys employ a somewhat higher aluminum content and less zinc than is found in H and C alloys. The mechanical properties of the alloys, when divided into high and low-aluminum groups, are quite similar, as determined from separately cast foundry-control type test bars.3 In this paper the decrease of mechanical properties caused by any given amount of microporosity is measured for H, C, A8, and AZ91 alloys. The relative susceptibility of each of the four alloys to microporosity is also determined. Typical mechanical properties and nominal chemical analyses are reported in Table I. [ ] The apparent similarities between the two alloys in each group have led to considerable discussion as to the relative merits of each of the compositions.2 Popular points for comparison between the alloys have been the relative susceptibility of each of the four alloys to microporosity5 and the effect of this microporosity on their mechanical properties. It is primarily intended, in this paper, to show the

Jan 1, 1946

By John Birkinbine

A RETROSPECT of the growth of the production of pig-iron for the past half century would be the history of the invention and introduction of heated blast as applied to the smelting of iron ores. As the apparatus employed was improved in conception and construction, the economical operation of the furnaces to which it was attached was the more marked, and the production correspondingly increased. To compare the original iron box placed over a coal fire with the modern hot-blast stove, with its combustion-chamber, gas-burners, and air-regulators, would be as unfavorable to the former as to contrast the product of the little Blauöfen with the yield of the improved furnaces of to-day. But, as these little Blauöfen were the germs from which the larger plants have grown, so from the crude apparatus invented and applied by Neilson has grown, in the face of great opposition, the more economical hot-blast stoves now in use. It is not surprising that an innovation like heated blast should have received a large amount of attention from metallurgists, nor that men of recognized ability should formerly have been found both among its champions and opponents, but it is remarkable that, at the present day, with the results of careful research and thorough experiment compiled in convenient shape for perusal, there are iron¬masters who still consider it economy to allow the products of combustion to escape into the atmosphere, rather than utilize them in heating the blast, because of a supposed injury to the quality of the product. In the present state of knowledge and practice, it is proper to express as an axiom, that a well-constructed hot-blast apparatus is essential to the economic operation of an iron-producing plant. Of the interpretation of proper construction there is of necessity a variety of opinions, and, with the view of solving the problem, the apparatus for heating blast has from time to time assumed various forms. Boxes, cylinders, and pipes, placed horizontally, vertically, inclined, or in circles and spirals, have been tried ; there have been pistol-shaped pipes, double pipes, divided or diaphragm pipes, siphon pipes, and as much variety in the mains, connections, flues, and setting. It is probable that, to the introduction of the bell and hopper in

Jan 1, 1876

By G. K. Engelhart

EFFECTIVE use of rotary kiln waste gases to preheat dry pulverized materials has been demonstrated in full-scale operation at the Allentown Portland Cement Co. plant, Evansville, Pa. Pulverized raw materials are preheated in suspension in the gas stream in a multi-stage counterflow process which draws the gases through a series of cyclone collectors. Upon entering the first cyclone stage the material, continuously delivered and suspended in the gas stream, is successively collected and resuspended until it discharges through the kiln feed pipe. Gas and material contact time is thus prolonged, providing a high degree of heat recuperation with a very low temperature differential between gas and material at the final stage. The suspension preheater, developed by Klockner-Humboldt-Deutz AG of Cologne, Germany, was first installed at the Norddeutsche Huette plant, Oslebshausen, Germany. Similar preheaters are now in operation at three other German cement plants. The first American installation, at the Allentown Portland Cement Co. plant, was designed and manufactured by Fuller Co. of Catasauqua, Pa., Humboldt's licensee for the United States, Canada, and Mexico.

Jan 4, 1954

By Douglas Baker

Zinc concentrates assaying approximately 54% zinc and 30% sulfur are roasted in a suspension type roaster to yield a zinc oxide calcine assaying about 65% zinc and 0.40% sulfur. This calcine is the feed material to the sulfuric acid leaching section of an Electrolytic Zinc Plant. The SO2 gases resulting from the elimination of sulfur from the concentrates are passed through a waste heat boiler for the generation of high pressure steam, cleaned by a baghouse, and delivered to the humidifying tower of a sulfuric acid plant system. The gases are then treated in a mist precipitator for final fume removal and then converted to sulfur trioxide in a three pass contact system using vanadium pentoxide catalyst for the manufacture of sulfuric acid. Waste heat steam is used to power the steam turbine which drives the acid plant blower.

Jan 1, 1970

By Robert Sisselman

Central Sweden's Grängesberg underground iron ore mine, which accounts for more than three million tons of pellet product annually, is experiencing a major changeover to continuous block-caving. The newly-adopted method, complete with a total revamping of mining equipment, will be fully operational by 1975. For the past 15 years, Sweden's Grängesberg mine has been mined using two different methods. Those ore thicknesses of 117 ft or greater (they comprise about 70% of the total area) are worked by block-caving techniques with cross-cutting carried out on each 195-ft working level, and loading at the foot wall on each 58-78-ft level. Sub-level caving is carried out in all ore sections less than 117 ft thick.

Jan 1, 1974

By NILS DANIELSEN

THE name of Swedish charcoal iron will probably bring to the memory of many old consumers an extremely tough and ductile iron which was formerly used in considerable quantities for common blacksmith purposes. To-day very little of this iron goes to such kind of work. Swedish charcoal iron is merely a speciality which is chosen whenever its remark¬able properties can be utilized. By giving a rough sketch of the manufacturing process of Swedish charcoal iron, the character of the iron, its weak as well as its strong points will more easily be understood. Swedish charcoal iron is a wrought iron also known in the United States under the name of Norway iron and Swedish Lancashire iron. The name Norway iron seems to have been attached to the product for the reason that in the earlier days it was generally brought into the States by Norwegian ships. However no iron of this kind is now made in Norway. The reason for the name Swedish Lancashire iron is that the manufac¬turing process emanated from Lancashier in England, the method being generally adopted in Sweden in the years 1831-1850. Today this iron is, with the exception of one plant in the United States, made in no place in the world outside of Sweden.

Jan 1, 1924

By H. L. Hazen

The uranium mill at Gunnison, Colorado, started crushing ore Dec. 31,1957, and has now been operating four months. The acid leached ore is washed by counter-current decantation through a system of four classifiers and four thickeners and most of the dissolved uranium reports in the overflow from the first washing thickener. This uranium is extracted from the aqueous pregnant solution by solvent extraction using di-2-ethyl hexyl phosphoric acid and tri-butyl phosphate dissolved in a high-flash-point kerosene as the extracting organic. The pregnant organic is then stripped with soda ash solution. The uranium bearing soda ash solution is filtered to remove insoluble carbonates and any sediment reaching that part of the circuit. The clarified carbonate pregnant solution is then acidified to 3 pH, heated to 180°F to drive off the last traces of CO2, and the uranium finally precipitated as yellow cake with MgO.

Jan 11, 1958

By W. B. Hall, Joy D. Lewis

Mine-run ore is received at Vitro in gondola cars and fed directly to a Cedar Rapids impact crusher. Following screening, the undersize travels through a recently installed three-stage sampling plant where successive cuts are executed by conventional Geary-Jennings type cutters to produce a final sample of 1 lb per ton of raw ore fed. Crushed ore is transported to one of three storage silos or to stockpile, depending upon grade and type of amen- ability. This permits the blending of a mill feed with some degree of consistency. Final grinding is accomplished in one of two closed circuit ball mill-classifier systems allowing simultaneous processing of two basic types of ores. High acid consumers may be leached separately in the required environment. Part of the free acid remaining can then be utilized by an ore stream entering later whose component ores require much less free acid for leaching.

Jan 11, 1958

By L. D. Lash

The key to successful liquid-liquid extraction is the solvent. First, and most important, it must be highly selective for the metal desired and yet reject other metal ions present; second, the ideal sol- vent is completely insoluble in the aqueous feed liquor; third, it has rapid phase separation and will not form emulsions; and, fourth, low cost is desirable, since losses occur even though the solvent is recycled. For this application a solvent known as DDPA (dodecyl phosphoric acid) was chosen since it closely met these requirements. DDPA is a long-chain alkyl phosphate developed for AEC by Oak Ridge National Laboratories, Dow Chemical Co., and the U. S. Bureau of Mines. The long chain contributes to low solubility in the aqueous phase and to high extracting power from acidic sulfate solutions, whereas the alkyl phosphates generally exhibit high selectivity for uranium solutions.

Jan 11, 1958

By William G. Schultz

Sylvite’s potash mine probably ranks as one of the most highly mechanized and automated mining operations in the world. Employing, on a normal 10-hr production shift, one supervisor and a crew of seven operators, Sylvite is able to mine at an average rate in excess of 600 tph. The ore is produced by two Marietta miners weighing 258 tons, making them the largest and heaviest piece of equipment ever taken underground. The ore produced by these two Marietta miners is conveyed to the shaft area, cycled through a 15,000 ton storage system and hoisted to surface completely automatically. The operation of all equipment in the mine can be monitored and controlled from a central control panel located underground.

Jan 7, 1972

By C. E. Jackson, E. C. Nelson, A. L. Christenson

Much information regarding the transfornlatio~lal characteristics of a steel as it cools in a known manner from the austenitic state can be obtained from dilatometric studies. This method has received more arid more attention because of its great flexibility, accuracy, and ease of interpretation. 'The method is entirely applicable to any rate of heating and cooling although the experumental procrdures for high rates of cooling have offered some difficulties. This paper presents a description of equipment employing cooling rates up to 500 °C. per secorld and the results of dilatometric observations on six commercial steels are included. French and Klopsch1 studied the cooling transformations of a serirs OF carbon steel, using the thermal arrest method. This was followed by the systematic investigatiol1 of Esser and co-workers on the effect of carhon2 and other alloying additions. in which the transforlnation temperature\ were determined by magnetic induction measurements indicated by a string galranoineter. Emphasis was placed on determining Ar' trailsformations and the critical cooling rates for these steels. The maglietic measurements wrere used in an effort to obtain more accurate data at higher cooling rates. Measurements of thermal arrest were made also to check the validity of the magnetic indications, and good correlation was found between the two, although Esser's,Ar' temperature measurements on iron-carbon alloys were about 200°F. lower than the measurements made by Fresnch and Klopsch. A notable contril~ution by Esser was the introduction gas quenching. wever and Rose4 used a moving-coil galranometcr in the study of the .Ar and Ar" of iron-carbon alloys by the thermal arrest method and obtained somewhat lover Ar" temperatures than those observed by Esser below I per cent carbon and considerably higher ahove. They concluded that the cooling rate had little influcncc on the Ar" temperatures above 0.4 per cent carbon, although Esser had observed a decrease in the -4r" temperature with increasing cooling rate with similar steels. Digges determined the .Ar" temperature4 for a scries of high-purity iron-carbon alloys, and close agreement with his results was obtained by Greninger. The thermal arrest method. together with metallographic observation used in both these studies, represents the latest investigations of this type. Any investigation by thermal analyses is dependent on the heat of reaction and the specific heat of the

Jan 1, 1945

By L. A. Willey

Although the interierometric method for the determination of length changes was devised by Fizeau more than three quarters of a century ago, it has not achieved the widespread use in the metallurgical field that its precision and simplicity would seem to warrant. The interferometer and the basic principle are both very simple. When optically plane surfaces held at a very slight angle to each other are illuminated by monochromatic light, rectilinear, equally spaced interference fringes arc formed. Each fringe corresponds to a defiuitc thikness of the wedge formed by the optical flat.;. The difference in wedge thickness between two consecutive fringes is cqual to one half the wave length of the illuminating light. Instruments for vicwing the intertero~ncter have passed through a number of modifications. Outstanding among the improvements were those Abbe. in 1884. His improved instrument permitted micrometric mcasurements to the order of one-hundredth of the width of an interference fringe (i.e., lengths were measured to the order of one two-hulldredth of the mave length of light ). It also permitted the consecutive use of light of several wave lengths. which made possible the determination of the order number of any fringe and therefore the absolute thickness of the wedge at any point. The Abbe dilatometer and methods of measuretment, including corrections to he applied for the change of index of refraction with change in tempcrature and barometric pressure in an air wedge, have been thoroughly described by Pulfrich.' Pulfrich2 made further improvements in the interference measuring apparatus. His instrument embodied all the features of the Abbe dilatometer but was made more versatile by its complete mechanical separation from the interferorneter. The introduction of an Amici prism in the piece permitted the simultaneous observ tion of the whole set of fringe systems developed in the interferometer from the visible light of a geisler tulle. .Also, the introduction of a direct-vision, reflecting prism made it possible to set the fringes parallel to the two vertical fiducial line. of the instrument without the necessity of rotating the interierometcr. Interferometric methods employed ill this country have been developed and dcscribed by Priest, Pelers and Cragoe," Austin,5 Merritt,= Saunders,? and Nix and MaNair. Since none of these authors used the type of instrument that was employed in the present investigation, they Will not be discussed here. This paper will be limited to the description of the interfernmetric apparatus and method used at the Aluminum Research Laboratories and to the presentation of data so obtained. Apparatus and Procedure A general view of the dilatometer, not including equipment for controlling and

Jan 1, 1945

By N. A. Zeigler

GRaphitization phenomena occurring in solid cast iron have principally been studied from the angle of the reactions taking place during annealing of white castings in the manufacturing of malleable iron. The selected bibliography at the end of this paper presents the high spots of the published information in this field. Graph-itization of gray iron upon reheating has received much less attention, primarily because only on rare occasions is this material subjected to any kind of industrial heat-treating. Moreovcr, articles made from gray iron are seldom used commercially at temperatures when any graphitization can take place. When used in such conditions, it is assumed that the articles can be replaced at frequent intervals, which can be afforded because of the low cost of gray iron. However, there is at least one commercial process in which articles made from gray iron, during their manufacturing processing, are subjectcd to rather high temperatures; that is, manufacturing of cast-iron enamelware, which is glazed at about 1600° to 1700°F. (870' to 930°C.) From practical experience, it has been found that one of the convenient and economical compositions of gray iron suitable for enameling is, in round figures, as follows: Si, 2.50 per cent; Mn, 0.35; S, 0.07; P, 0.80; T.C., 3.35; C.C., 0.70. Since this iron usually is cast into thin-walled sections, the percentage of com- bined carbon in it is relatively high. Upon heating in the enameling furnaces, this combined carbon graphitizes, which causes permanent dimensional changes of the articles. Obviously, from practical considerations, it is desirable to maintain these dimensional changes as constant as possible. In the course of experimentation with this iron, two series of experimental heats were prepared in which the manganese to sulphur ratio of the standard cupola metal was offset by ladle additions of: (I) progressively larger amounts of sulphur, and (2) progressively larger amounts of manganese. Each one of these ladle charges was cast into experimental plates 8 by 4 in. and about 5/16 in. thick. All told, 13 ladle charges were thus treated. All of them are listed in Table I, together with their chemical analyses. It may be noted that the manganese to sulphur ratio in these samples ranges between 1.2 and 30.2. Every one of these compositions was subjected to thermal allalysis, using an automatic, self-recording differential dila-tometer. The specimens used in this instrument are 50 mm. long and 4 mm. in diameter. During the dilatometer cycle they are kept under a vacuum of about 3 microns. Each one of them was subjected to a thermal cycle by heating it to I830°F. (1000°C.) in 3 hr. and cooling to room temperaturc in 5 hr. Figs. I, 2 and 3 present three automatically recorded dilatometer curves for irons: Serial No. I (normal composition), Serial No. 6 (high sulphur), and Serial No. 13 (high manganese). All three of these figures are

Jan 1, 1945

By P. W. Bridgman

Flow and fracture are admittedly complicated phenomena of which we are yet only partially masters. There is not even nni-.persal agreement as to the details of the language best adapted merely to describe the phenomena, to say nothing of any theory. Certain points of view, however, are widely held, and there are certain general expectations as to what sort of procedures will prove permissible. A complete description of any situation involving fracture would demand a complete history of all the variables in the control of the experimenter. The experimenter endeavors so to choose his independent variables that they are adequate to determine completely the situation in the sense that when an experiment is repeated on the same initial material and with the independent variables running through the same sequence, all the other measurable properties of the system will also run through the same course. It is, I think, the universal conviction that when we are dealing with phenomena of flow and fracture, the most important of the necessary variables are the external forces acting on the various parts of the body; when the force history repeats, with certain obvious restrictions such as that temperature must be constant and non-mechanical forces, such as magnetic field, must be small enough to be ineffective, then the history of all measurable properties will repeat; in particular the alteration of geometrical shape due to flow will run through the same course, and when fracture comes, the character of the fracture will be reproduced. Complete mastery of merely the descriptive aspects of flow and fracture would demand the ability to predict the entire course of flow and complete characterization of the final fracture for every possible combination of forces, varying in time in all possible ways, when applied to bodies of all possible shapes. This full situation is obviously of prohibitive complexity. The first stage in reduction to manageable simplicity is to resolve the total situation into the sum of contributions made by small elements. Our thesis is that if each of the elements is adequately characterized, the behavior of the whole system is fixed. The element is usually taken of a simple geometrical shape, suggested by the mathematics best adapted to the particular situation. The forces acting across the faces of the elements are ultimately determined by the forces acting across the free faces of the whole system. The detailed process of finding the precise forces on the faces of all the elements in terms of the external forces involves the use of a special mathematical invention, the stress, a constructional quantity consisting of six components. The stress at any point in the body is determined by both the external force system and by the physical properties of the body at all points; quite different stresses prevail at the interior of bodies of the same shape under the same external forces in the elastic and plastic ranges. The forces on the faces of any element are, however, uniquely determined by the stress system at the element. Our fundamental thesis

Jan 1, 1945

By L. R. Jackson

It is convenient to have a consistent system of notation that will allow the representation of the entire range of complex stresses from hydrostatic compression to hydrostatic tension on plastic flow in a single diagram. Such a system is provided by making use of the fact that any complex stress system can be resolved into a hydrostatic tension or compression and a pure shear. Consider a stress system having the principal stresses This system can be resolved into a new system consisting of the three components and three pure shears. If Sm is positive, the net stress effect is hydrostatic tension; if it is negative, the effect is hydrostatic compression. In order to produce a systematic notation, a quantity that will be referred to as the "triaxial ratio" will be defined by the equation _ Sm Tr = Sm - Sm is given by Eq. I and Sl is the absolute magnitude of the largest principal stress without regard to sign. Table I lists the triaxial ratios for various common systems. Table i.—Triaxid Ratios for Various CommonSyslems Triaxial Ratio Stress System Tr Hydrostatic compression — SI - —St - -S³............................... -1 Torsion or shear -SI - S². S² = O..... O Simple tension SI. SI = SI = 0......... +0.33 Biaxial tension SI = S² S³ - 0......... +0.66 Hydrostatic tension +SI - +S³ = +S³. +1.00 Representation of Strains Strains will be plotted as "true" strains according to the system proposed by Ludwik.1

Jan 1, 1945

By M. Gensamer

It has been suggested by a number of people that it would be worth while for some one to attempt to summarize or condense the proceedings of this symposium. This task has fallen to me as organizer and co-chairman. Its difficulty will be appreciated by anyone who attempts to read the whole proceedings. It is therefore with trepidation that I offer the following digest. In recent years there has been a renewal of interest in America on this subject of the cohesive strength of materials, and a growing appreciation of the need for a better theory of cohesion failure. The theories of elastic action and plastic action are well developed, particularly the former. The theory of plastic action is still in the course of development, but it is well along. Plastic action is terminated by cohesion failure and what is needed is a theory that will tell us when to expect the cohesion failure. In the past it has generally been assumed that cohesion failure will occur when a critical value of the maximum tensile stress has been reached. Many experiments have shown that this is not strictly true, and this symposium concerns itself with the failures of this simple hypothesis, and with the efforts that have been made to devise a more satisfactory theory. The most active contributor in recent years to knowledge in this field is Dr. McAdam, and he was asked to open the symposium with a summary or condensation of his papers and views. Undoubtedly it is presumptuous to attempt a still greater condensation, but perhaps it will be useful, because even his contribution to this symposium contains no summary, no concise statement of just what his contribution has been. Dr. McAdam makes two main points The first is that the cohesive strength is not a single valued quantity, but that it is a function of all three principal stresses and hence must be represented diagrammati-cally by a surface in a three-dimensional figure, Dr. McAdam has attempted so to delineate the cohesion limit, basing his

Jan 1, 1945

By D. J. McAdam

As shown in three recent papers by the author, in two papers by McAdam and Mebs, and in a paper by McAdam, Mebs, and Geil," the technical cohesive strength of a metal, in any particular state as regards mechanical treatment and heat-treatment, cannot be represented by a single stress value, but must be represented by a diagram with the principal stressest as coordinates. Each point on the boundary of such a diagram represents a technical cohesion limit. The technical cohesive strength thus comprises an infinite number of technical cohesion limits, each representing fracture under a specific stress combination. Moreover, neither the yield strength1 nor the ultimate strength can be represented completely by a single stress value, but must be represented by a diagram with the principal stresses as coordinates. All combinations of the principal stresses may be classified in three groups as illustrated by Fig. I. Fig. Ia shows three typical stress combinations with no two principal stresses equal. The magnitude of each principal stress is indicated qualitatively by the length of the arrow. Arrows pointing away from the cube indicate tensile stresses; arrows pointing toward the cube indicate compressive stresses. Typical stress combinations with two principal stresses equal are illustrated in Figs. rb and Ic. Such stress combinations would be produced by subjecting a cylinder to combinations of uniform axial and radial stresses. The uniform radial stress may be resolved into two equal principal stresses. with the mutually perpendicular directions rotatable around the axis of the cylinder. Fig. ib shows stress combinations with Sz equal to The greatest principal stress is in the axial direction, and the stress combination tends to cause either absolute or relative increase in length.* Fig. u shows stress combinations with S2 equal to St. The greatest principal stress is in the radial direction, and the combination tends to cause either absolute or relative decrease in length. The complete representation of either technical cohesive strength, yield strength, or ultimate strength generally requires a three-dimensional diagram. When two of the principal stresses are kept equal, however, the strength of a metal may be represented by a two-dimensional diagram with the coordinates representing the axial and radial stresses.6-II In this paper, attention will be confined almost entirely to stress combinations with two of the prin-

Jan 1, 1945

By Norman P. Goss

What would appear to be a very simple process on paper has proved to be overrun with a multitude of unseen difficulties. For more than 70 years attempts have been made to cast metals in a continuous manner, but it has been only within the last Io years that some degree of success has been achieved.1 Historical Development Bessemer's Experiments—Method I Bessemer was the first to try to cast molten metal in a continuous manner. His method is fully described in U. S. Patent No. 49053, issued in 1865. The patent drawing is shown in Fig. I. In this method the molten metal was poured between a pair of rolls of large diameter, which were cooled by water sprays. Means were provided to prevent moisture from coming into direct coptact with the molten metal. The width of the strip was controlled by the flanges. On paper this should work to perfection, but it is beset with many difficulties still awaiting solution. Bessemer failed to reduce his invention to commercial practice. About 1890 Bessemer's method was revived by Norton and associates (U. S. Patent No. 441375). They formed the Fluid Metal Rolling Co. at Maywood, Ill., and spent $250,000 in endeavoring to develop the technique for this simple method. Finally they had to abandon it. Naturally, they did carry the technical development far beyond anything Bessemer had done, but even so it was far from being a useful commercial success. In recent years it has undergone further development by C. W. Hazelett (U. S. Patent No. 2058447), who has succeeded in obtaining long lengths of copper, brass, aluminum, and even stainless steel. He introduced many' ingenious devices but the greatest obstacle still remained—the disintegration of the roll surface when the surface is heated and chilled in rapid succession. Difficulty is also experienced in maintaining a uniform supply of molten metal to the rolls. The patents pertaining to this method would indicate these to be the major obstacles. Experimental work by Mellen—Method 2 A departure from the method introduced by Bessemer, was tried by Grenville Mellen, of East Orange, K. J., sometime between 1914 and 1920, who obtained a number of patents.2 His method is illustrated in Fig. 2. This method failed to make an impression upon the art; however, it is of value in pointing out the difficulties the inventor ran into and the way in which he tried to meet them. The split mold sections form two endless chains. When going through the center of the apparatus, these sections engage each other to form a complete mold. As the engaged mold section moves downward at a constant speed, molten metal is teemed into it. As this is going on, another set of cooperating mold sections move into position on top of the one being filled. The molten metal is teemed into the mold through a silica tube. According to the teachings of this patent, the level of molten

Jan 1, 1945