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By George S. Miller

Now that low-carbon steel is manufactured successfully in large quantities by the Bessemer process, and threatens to displace wroughtiron for nearly all purposes, it becomes interesting to find how its Specific gravity compares with that of wrought-iron. The general name "steel" is retained in this paper to designate that metal made by the Bessemer process, which might be more properly called " ingot iron." But the former name seems to be quite firmly established in the iron trade. This steel offers many inducements to the manufacturer of architectural iron, by reason of its hornogencity, and the large masses in which it may be readily moulded. The steel from which these determinations have been made, was produced in four-ton heats and cast into ingots of about 3100 Ibs. weight, having an average section 14'' by 14". These ingots were rolled in a blooming-mill to a section about 24" by 14", cut into slabs and rolled in a plate-mill to a plate .065" to .165" thick, and about 1411 in width. The specific gravity was obtained from pieces of this plate. The metal showed by analysis .10 to .12 per cent. carbon,.33 to .45 manganese,.060 to .072 sulphur,.075 to .082 phosphorus, and .010 silicon. The samples were not annealed, but were brought to a bright surface with a file. All figures given are averages of not less than three determinations on separate pieces from the same plate. The variation in the figures from which the averages were made in no case exceeded .015.

Jan 1, 1886

By Niels Hansen

Dispersion-strengthened sintered aluminum products are normally manufactured from surface-oxidized aluminum powder, SAP,' or from atomized aluminum powder.' The powder-blending technique consisting in mechanical mixing of the constituents has been used in the manufacture of numerous dispersion-strengthening alloys, but has never been successfully applied to aluminum alloys. This technique may, however, be applicable if it is possible to produce an unagglomerated mixture of the constituents in the form of fine powders, and the present study was initiated to test this assumption in the aluminum/aluminum oxide system.3 Table I lists the two grades of aluminum powder and the aluminum oxide powder used in the manufacture of the alloys. MD 105 A is an aluminum powder with an average grain size less than 5 IJ., which is isolated from the MD 105 powder by centrifugal separation in cyclohexanol. The aluminum powders and the aluminum oxide were blended in a high-speed blender and then subjected to cold compaction and hot compaction at 550" to 600°C. Subsequently the compacts were hot-extruded with an extrusion ratio of 15 to 1. The alloys were evaluated by tensile testing at room temperature and at 400°C, microscopic examination, and heat treatment at 500°C followed by tensile testing at room temperature. For the purpose of comparison, a commercial SAP quality supplied by Swiss Aluminium Ltd. was tested in the same manner. The tensile data at room temperature and at 400°C are plotted in Figs. 1, 2, and 3 as a function of the weight percent of oxide. The oxide content

Jan 1, 1964

By C. W. Sherman, J. Chipman, H. I. Elvander

THE pronounced and usually deleterious effects of sulphur on all ferrous metals and the resultant necessity for its control in metallurgical processes have stimulated many investigations of the system iron-sulphur. The data required for thermodynamic study of the behavior of sulphur in molten iron and steel include the activity and free energy of the dissolved sulphur and its heat of solution. Such data are also of theoretical interest since there is all too little information available concerning solutions of nonmetallic solutes in metallic solvents. It was the purpose of this investigation to attack the problem very directly by a study of equilibrium at several temperatures in the reaction H2 (gas) + S = H2S (gas) [1] K1 = PH2S /PH2 as where the sulphur is present in the liquid iron in amounts up to several percent by weight. Such a method of attack is not new since several careful studies have already been reported. It is planned, however, to extend the study to other metallic solvents and particularly to determine the effects of the various alloying elements on the activity of sulphur in liquid iron. This paper presents the results on molten iron-sulphur alloys containing up to 4 pct sulphur in the temperature range 1530°-1730°C. Literature Review The significant researches on dilute molten solutions of sulphur in iron include those of Chipman

Jan 1, 1951

By T. Egleston

The importance of making analyses of gases in furnaces which are used for metallurgical purposes is every day growing more and more evident. It is the only method of understanding the reactions that take place in the furnace, and of economically conducting the operations both with regard to the fuel used and the reactions which take place on the bodies to be subjected to the influence of the heat and gases. As a knowledge of the composition of gases is becoming every day more necessary to the proper conduct of furnace operations, it seems desirable that furnace managers should generally know that the analysis of gas for commercial purposes is neither difficult, tedious, or expensive, and that it does not necessarily imply the use of corrections requiring difficult instrumental observations and long and tedious mathematical calculations. Any method, therefore, which will tend to render these analyses simple will also tend to having them made and repeated as frequently as the analyses of the ores and other materials charged in the furnace. They should be made even more frequently, as their composition is affected by any change in the condition of the furnace, and a knowledge of their composition will give a ready clue to the unseen and otherwise not easily detected changes which are taking place. The only practicable method of making industrial analyses of gas is that of measuring volumes in graduated tubes. The methods by

By J. A. M. van Liempt

SINCE the discovery, of von Laue, that a crystal forms a natural grating for X-rays, our knowledge of the structure of solids has gone forward with rapid strides. This progress is not only of purely scientific interest, but has also yielded direct technological results. One of the most valuable results is the broadening of our knowledge of the structure of pure metals and alloys. To promote these studies it is often desirable to have at our disposal pieces of metal consisting of one single crystal. As is so often the case in the natural sciences, we obtain the best results by making our earliest experiments on pure, simple materials and avoiding unnecessary complications. The Cryogen Laboratory at Leyden followed this method with much success, because the work was done at such low temperatures that the heat movement of the atoms was almost' absent. Similarly we can simplify the studies of metals by leaving out of consideration the influence of the grain boundaries and the mutual influence of the crystals by using unicrystalline instead of polycrystal-line metal. Methods of making single crystals have been scientifically studied during the past few years. Some methods were already known in the arts, but these have been improved and new methods have been developed. The methods for making metallic single crystals may be divided into the following groups: A. From the liquid state B. From the gaseous state C. Electrolytically D. By recrystallization in the solid state

Jan 1, 1927

By P. Gordon, A. S. Iyer

IN a paper on the mechanical behavior of heat-treated steel, N. H. Polakowski' put forward arguments to the effect that the stored energy resulting from the deformation of metals should be reduced during the inital stages of subsequent deformation carried out under conditions which produce work softening. At the time (1957) the only energy measurements available as indirect evidence on this point were the results of M. M. Degtyarev,2 some of which Polakowski reproduced in his Fig. 6, and which are again reproduced here in Fig. 1. The solid lines in the upper part of Fig. 1 are Degtyarev's, the dashed Lines Polakowski's prediction of the true trend of the stored energy in copper samples pre-strained in tension and then given various amounts of subsequent compression. The accuracy of this prediction has been borne out by some experiments carried out on American Smelting and Refining Co. copper (99.999' percent Cu) by the present authors. Bars of this copper about 0.4 in. in diam and 12 in. long were prepared by vacuum melting and casting, followed by cold forging and swaging in several stages of about 40 pct reduction in area with intermediate recrystallization anneals. After the final anneal one bar was deformed in tension to 30 pct elongation; the gage length was then cut into several samples which were given axial compressions of various amounts. The hardness of

Jan 1, 1960

By William C. Buell

As used in connection with open-hearth or other high-temperature operations, "insulation" refers to a multitude of substances, natural or manufactured, that have the one principal property of preventing the flow of heat by conduction to a greater degree than refractories can prevent it, the principal properties of the latter being resistance to temperature and/or chemical action. The term "control" as commonly applied to the mechanization of management functions is inappropriate without qualification, for without some degree of control of every operation we could produce no steel worthy of the name. Although grouped together in this paper, insulation and control in open-hearth furnaces have little, if any, interrelationship, therefore the paper is made up of two distinct parts. INSULATION OF OPEN-HEARTH FURNACES More than ten years ago the writer proposed the insulation of an acid open-hearth furnace system below the charging floor, and it was accomplished, with gratifying results. Possibly that was the first time the insulation of regenerators and slag pockets of any open-hearth furnace was undertaken, but shortly thereafter such insulation became general, and when the six groups of 15D-ton furnaces' were built in 1929-1930, they were completely insulated below the charging floor. While the practice was accepted at least five years ago, it was not well understood, however, as indicated by the following incident which occurred in connection with an installation made in 1929. After the

Jan 1, 1935

By T. PH. D. Egleston

THE importance of making analyses of gases in furnaces which are used for metallurgical purposes is every day growing more and more evident. It is the only method of understanding the reactions that take place in the furnace, and of economically conducting the operations both with regard to the fuel used and the reactions which take place on the bodies to be subjected to the influence of the heat and gases. As a knowledge of the composition of gases is becoming every day more necessary to the proper conduct of furnace operations, it seems desirable that furnace managers should generally know that the analysis of gas for commercial purposes is neither difficult, tedious, or expensive, and that it does not necessarily imply the use of corrections requiring difficult instrumental observations and long and tedious mathematical calculations. Any method, therefore, which will tend to render these analyses simple will also tend to having them made and repeated as frequently as the analyses of the ores and other materials charged in the furnace. They should be made even more frequently, as their composition is affected by any change in the condition of the furnace, and a knowledge of their composition will give a ready clue to the unseen and otherwise not easily detected changes which are taking place. The only practicable method of making industrial analyses of gas is that of measuring volumes in graduated tubes. The methods by

Jan 1, 1877

By R. Gatewood

The solution here offered is at once simple and important in its direct and indirect bearings. According to the principles of surface-tension, which will be found sufficiently enlarged upon for present purposes in Clerk Maxwell's excellent little treatise on The Theory of Heat, a mechanical mixture of liquids will frequently of itself divide into groups, consisting of liquids mixing among themselves but withdrawing from the other liquids. The following simple and familiar illustration will suffice: " If we mix water with alcohol, the liquids diffuse into each other. If we now attempt to mix oil with the alcohol and water, the two liquids separate from each other of themselves, and in the act of separation sufficient force is brought into play to set in motion considerable masses of the fluids." Maxwell goes on to show that this relative energy is one of arrangement, depending on the nature of the fluids and the area of the surface of contact, the act of separation tending to reduce this surface to a minimum consistent with equilibrium; that this surface-tension exists between a solid and touching fluid, either liquid or gaseous, being of one sign or the other, in the case of a liquid, according as it tends to draw itself up into a drop on its surface or to spread and wet the solid. After considering various cases, lie states that which particularly interests us, thus : " When a solid body is in contact with two fluids, then, if the

Jan 1, 1885

By H. C. Rolseth, R. H. Kohler

Jet channeling made its entry into the granite industry in 1955 and quickly gained acceptance as an economical method of quarrying. Developed by the Linde Division of Union Carbide Corp., this method employs a small rocket-jet burner with a high-temperature, high-velocity exhaust flame that causes granite to disintegrate. It can thus make continuous vertical cuts to free large blocks from granite formations. The Thermal Spalling Process The effect of a thermal device on rock depends upon the rock's spallability. In simplest terms, spalling is the decrepitation resulting from differential expansion of rock crystals due to thermally induced stresses.1 the individual rock properties influencing the spalling characteristic are so numerous and their interaction is so complex that it has so far been impossible to predict with accuracy the reaction of any particular rock to a high-temperature source of heat. Perhaps computers will eventually make such predictions possible, but for the present it is necessary to impose the thermal shock conditions on a sample of the rock to establish its spalling characteristics. The properties most favorable to a high degree of spallability are: (1) Large linear thermal expansion at temperatures below 700º C. (2) High thermal diffusivity at temperatures below 400º C. (3) Equigranular interlocking structure with little or no fine-grained clay or mica alteration products. (4) No significant amounts of soft, low-melting, or elastic minerals or materials which yield after thermal decomposition.

Jan 7, 1969

By J. H. Slater

THERE is nothing particularly new about the use of sinter in a blast-furnace burden. For many years flue dust has been sintered at the various blast-furnace plants to put it in a form that could be recharged to the furnace with some assurance that it would stay in the second time. This paper is not a compilation of scientific data but only an attempt to give our experience with sinter. There are some unexplained discrepancies in the tests given here, such as the flue dust produced and iron tonnages, but the results given are the results that were obtained. Sinter is not the cure-all for blast-furnace problems. A good coke is still the most important factor in good furnace operation. However, good sinter is a big help. As flue dust is produced under varying operating conditions and fluctuates greatly in carbon content, it is difficult to produce from flue dust alone a uniform sinter, which will give satisfactory blast-furnace results. Sinter made from flue dust alone will change in character with every carbon variation. Almost invariably flue dust con-tains carbon in excess of the amount necessary to make good sinter, and this excess must be burned out, This, of course, necessitates reduction of the speed of the sintering machine and thus a decrease in tonnage, An alternative is to dilute with a carbon-free material to use up the excess carbon. High-carbon material when sintered results in a very dense, undesirable prod-uct, since the excess heat melts the charge into a hard, nonporous mass, and tends to form refractory silicates.

Jan 1, 1940

By R. D. Nelson

The purpose of this technical note is to briefly present some data on a phenomenon—recrystallization with concurrent deformation—that has been found to occur in a plutonium. This phenomenon is unusual because a plutonium is considered brittle, not easily deformed, and not easily recrystallized; the a phase is simple monoclinic having 8 atoms per unit cell and it is stable below about 115°C. The properties of the recrystallized metal were different from the as-cast metal. Even though a plutonium is difficult to deform, Ianniello successfully rolled it' and he also observed some recrystallization at 120°C.2 Pavlick and Hanson3 detected some recovery at 109°C but they observed no recrystallization. Gardner4 and Bronisz5 studied the compression properties up to 100°C but they did not report having seen recrystallization. In the present deformation studies of electrorefined plutonium pronounced recrystallization took place concurrently with plastic deformation in compression between 24" and 115°C. The metal contained less than 300 ppm total impurities with the major impurities being 100 ppm Am, 30 ppm C, 40 ppm W, and 25 ppm U; all other impurities totaled less than 100 ppm. The compression specimens were machined to dimensions of 1.2 cm long and 0.8 cm diam from as-cast rods having a density of 19.65 g per cu cm. They were heated to the test temperature in a high-temperature silicone fluid that was evacuated to 10-4 Torr. With this procedure the specimens oxidized a negligible amount, and the temperature was maintained within ±0.2°C for times up to 3 weeks. Deformation and recrystallization

Jan 1, 1969

By F. C. Newton

REFINERS of lead by the Parkes process have always been solicitous of recovering the zinc used in the desilverization, and justly so, as the loss in zinc constitutes one of the heavy costs in this method of refining. Part of this loss is due to the absorption of zinc by lead, and in the present state of knowledge is not recoverable as metallic zinc. The remainder of the zinc, which finds its way into the precious-metal-bearing crust, is recoverable and naturally engages the operators' most exacting attention. Careful elimination of the impurities in base bullion has enabled the refiner to produce a zinc crust better adapted to retorting, which reflects favorably in the zinc recovery; and to produce a richer crust, thereby lowering the zincking cost, as the increased efficiency of the zinc results in less of it being in circulation. It is obvious that if the ratio of concentration be increased, a lessening of the amount of crust formed will ensue, throwing less work on the retorts and diminishing the amount of retort metal sent to the cupels, thus making an actual money saving in all these operations. In the effort to obtain a rich crust, the metallurgist has increased the heat to a considerable degree, upon the assumption that at the higher temperature the zinc-silver alloy could be squeezed free from the adhering lead. A further possibility for improvement suggested itself in the freezing-point curve of Prof. H. C. Carpenter, upon zinc and silver. Study of this curve disclosed the existence of a definite chemical compound, . Zn3Ag2, with a freezing point of 665° C., a promising compound for practical application.

Jan 2, 1915

By N. W. Shed

The specifications for bridge-steel are usually not severe. The main difficulty is to secure a material which will roll easily, without showing signs of cracking on the corners of the blooms or on the flanges of the beams. In many mills sulphur has been deemed the most harmful constituent in this respect. It has been thought hazardous.to roll steel containing over 0.07 per cent. of sulphur. Yet, in making steel for the Phoenix Iron Company, I have produced from stock running as high as 0.13 per cent. of sulphur a material which rolled very satisfactorily. It is reasonable to infer that the injurious effect of sulphur can be neutralized, to a great extent, by proper treatment in the open-hearth furnace; and the following notes from my usual practice here may be of interest to those obliged to use high-sulphur stock. The steel made at Phoenixville in the 20-ton furnaces has about the following composition : Per cent. Carbon,...0.15 to 0.20 Manganese,.........0.50 to 0.60 Sulphur,..........0.11 to 0.13 Phosphorus,.: .0.04 to 0.06 Silicon,.......... 0.01 to 0.02 The best running heats were made with a small amount of pigiron. In using large proportions of pig the quantity of ore is also increased. This not only cuts the bottom, but also lengthens the time required to bring the charge down. Up to 50 per cent. of pig may be used, but 25 per cent. is much better. A 40,000-pound charge, containing 10,000 pounds of pig and 30,000 pounds of Bessemer butts or beam-scrap, works very well.

Jan 1, 1890

This discussion of the paper of Chester W. Washburne should have been printed following the remarks of H. A. Wheeler, in Bulletin No. 100, April, 1915, pp. 835 and 836, but was inadvertently omitted. ROSWELL H. JOHNSON:-There is one reason why the hydrostatic interpretation of gas pressure is not wholly acceptable. As we go clown in the sands we seem to get excesses of gas. Particularly in this field it becomes excessive in quantity relative to the amount of water in the sand. If this holds in other fields as well it must mean that there has been an ascension of water, because these sedimentaries when laid down, were filled with connate water. If we do get an ascension of connate water, produced by some such phenomena as its expansion by heat or by the formation of new gas by pressure upon organic materials at great depth, we can hardly expect the pressure to be controlled merely hydrostatically. * In reply to Mr. Wheeler's inquiry as to gas wells with pressure higher than hydrostatic pressure, I would cite the original wells given by Orton on which he based the hydrostatic theory. He used in his calculation a head of 600 ft. above tide, assuming the outcrop of the Manitoulin Islands to be in Lake Superior, whereas the Trenton does not outcrop at Lake Superior. The Manitoulin Islands are in Lake Huron, the level of which is 580 ft. above tide. No allowance is made for the lower density of the fresher water near the outcrop, the weight taken for the whole column being the water of high density found at the wells.

Jan 5, 1915

By M. A. Quader, D. Kuhlmann-Wilsdorf, R. A. Dodd

STACKING fault tetrahedra were first observed in quenched and aged pure gold by Silcox and Hirsch1 and identified as defects originating in the collapse of vacancy discs on {111} planes. It was supposed that sessile loops are the first product of the collapse, and that by a dislocation dissociation/glide sequence these are converted into tetrahedra. Although the tetrahedra can be mechanistically accounted for in this way, recent investigations indicate that their growth occurs by the absorption of individual vacancies on small nuclei involving perhaps as few as six vacancies.2-7 Besides stacking fault tetrahedra, triangular and crystallographic shaped Frank loops, although fewer in number, have always been observed in quenched and aged gold.19798 It is not known definitely whether these loops form from collapsed tetrahedra. The fact that the Frank loops are usually larger than the accompanying tetrahedra might indicate that the loops grow independently by absorbing vacancies, but this does not rule out the possibility of the collapse of tetrahedra into loops under all circumstances. Silcox and Hirsch1 have actually observed under the electron microscope tetrahedra collapsing into loops, probably due to stresses set up by the heating of the specimen by the electron beam. The energy residing in the stacking faults of a tetrahedron is proportional to the square of the edge length, while the energy of a triangular perfect dislocation loop depends on its edge length, L, as const L ln(L/ro). Therefore, beyond some critical size tetrahedra must become unstable with respect to collapse into triangular loops.1,3,8-11 However, it seems that in the absence of strong stresses tetrahedra usually decay by the

Jan 1, 1969

By W. H. Fitch

HAVING been asked to make some remarks after the reading of Mr. Dyrssen's paper, I regret that a test started some months ago has not yet been completed, but some of the things which I can tell you at this time seem interesting and shed a little different light on the idea of a recuperator. The device referred to is becoming more than. a recuperator, largely taking the place of a regenerator. I assume there is familiarity with the sketches that I presented in October, 1926, before the Engineers' Society of Western Pennsylvania, describing our re-cuperator combination with checker chambers, and I have additional ones to show at this time. The follow-ing remarks will deal with modifications that have been made. At that time I suggested the gases leaving the regenerators at, say, 1400°, be reduced to 500° F. The opinion of the operating men consulted since that time is that, under the best operating conditions, the tem-perature may be 750° to 800° F. after the recuperator and on entering the stack. While the lowest final temperature of the gases en-tering the stack is important from the economic stand-point of fuel burning, and operating in general, it is not the whole story. The method of getting the heat out of the checkers is important. It is believed by many with whom we have talked that a better way is by a combination of checkers and a carborundum re- cuperator of the type described as it will stand all tem-peratures met in practice and might be called a super-refractory.

Jan 1, 1928

By William R. Webster

At the Florida meeting of the Institute, in March, 1895, I presented a Note on a Proposed Scheme for the Study of the Physics of Cast-Iron,1 giving an outline which, for convenience of reference, I here repeat. Suggested Lines for DiScuSsion and IvestiGation. I.—Correspondence between chemical composition and melting-point, fluidity, shrinkage, fracture, chill, micro-structure, and other physical properties. II.—Influence of: 1. Cupola-mixture, use of steel and other scrap, oxidized or clean material, 2. Manner of melting, flux, etc., 3. Casting-temperature, A. Fracture. 4. Manner of handling melted metal and B. Micro-structure. method of casting, C. Physical properties. 5. Size and form of casting, D. Shrinkage. 6 Kind of mold, green sand (under dif- on E. Chill. ferent conditions of ramming, amount F. Residual strew of moisture, and skin-dried), dry sand, G. Condition and quan- loam, and chills, tity of carbon and 7. Rate and mode of cooling castings, other elements. 8. Manner and temperature of heating for annealing, 9. Additions of nickel or aluminum, III. —-Segregation as affected by : 1. Composition ; 2. Casting-temperature; 3. Rate of cooling ; 4. Size and shape of casting. IV. —Blow-holes, their volume and position as affected by: 1. Composition; 2. Casting-temperature; 3. Casting-pressure ; 4. Rate of cooling; 5. Size and ehape of casting ; 6. Special additions. It was hoped that a discussion might thus be elicited, similar in interest and value to the discussion of the physics of steel, which had been so widely and gratefully welcomed by students and practitioners in that department. That this hope was not

Jan 1, 1905

By R. M. Zimmerman

INTRODUCTION Tuff is being considered as a possible geologic median for the underground storage of commercial high level radioactive wastes by the Department of Energy (DOE). DOE has the responsibility for developing or improving the technology fir safely and permanently isolating these wastes. DOE programs must satisfy requirements established by the Nuclear Regulatory Commission (NRC) for the licensing and regulating of these storage facilities (NRC 1981). Pertinent draft NRC requirements are: 1) releases of radioactivity to the environment must be within prescribed limits and 2) emplaced canisters containing wastes must be retrievable up to 50 years following emplacement. High level radioactive wastes produce heat in storage and it is essential that the thermal/mechanical/hydrological response of the host rock will not significantly degrade either the structural performance o£ the repository or the ability of the natural or engineered barriers to retard radionuclide migration. The Nevada Nuclear Waste Storage Investigations (NNWSI) was established by DOE to evaluate the suitability of disposing of high level nuclear wastes on or near the Nevada Test Site (NTS) (NNWSI 1980). NNWSI has focused exploration and site evaluation on the tuffs of Yucca Mountain. Field testing is essential to support site characterization and repository design efforts. Preliminary studies have been conducted indicating that tuffs in G-tunnel on the NIS contain welded and nonwelded tuffs that have similar properties to those in Yucca Mountain. Thus, field testing can be accelerated. This paper discusses the issues supporting the planned field experiments in G-tunnel. Issues not related to rock mechanics are not included.

Jan 1, 1982

By Gregory Dybalski

The purpose of this paper is to illustrate the forecast capability of the econometric model of the cobalt industry1/ as utilized by the Federal Preparedness Agency. Forecasts from this model are illustrated from the premise that the leading producer continues production of cobalt. An alternate forecast is presented where the model structure is altered to reflect the condition where the leading producer leaves the market. All estimations and forecasts presented here are shown for illustrative purposes. The cobalt industry is highly concentrated; one company, owned by the Zaire government, accounts for approximately three-fifths of world production. The cobalt supply outside of Zaire is determined by the level of activity of copper or nickel markets, as cobalt is mined as a by-product of copper or nickel. The demand for cobalt reflects a diversified usage pattern; cobalt is used mainly in heat and corrosion-resistant materials, high- strength materials and permanent magnets. According to 1974 U.S. consumption data superalloys accounted for 22%, magnetic alloys 18%, cutting and wear-resistant materials 13%, and catalyst 7%. Foreign consumption is probably similar in terms of usage categories, but the relative order of the categories is in variance.2/ The Cobalt Model The cobalt model's object is to explain consumption, supply and price movements by utilizing statistically estimated equations. Central to the econometric model is the role of Zaire as the profit-maximizing "dominant firm". Zaire sets the price that is most profitable for itself. The price of cobalt depends on industrial demand, production of other firms, and net exogenous purchases, such as government

Jan 1, 1977