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By H. R. Wuthrich

The Metallgesellschaft AG decided in late 1965 to build an Electrolytic Zinc Plant at Datteln (W. Germany). Lurgi-Chemie was entrusted with the engineering and erection of the entire plant. Ground was broken in February 1967 and the operation was started on August 1st, 1968. The new Electrolytic Zinc Plant was designed to produce a minimum of 100,000 metric tons of special high grade zinc and 200,000 metric tons of sulphuric acid. Concentrates from Meggen (W. Germany) and mainly Timmins (Canada) are roasted in two turbulent layer roasters. The sulfur dioxide containing gases are converted in a "Bayer double catalysis unit" to sulfuric acid. The calcine is leached batch wise, the leach residue separated from the pregnant solution by counter-current thickeners and drum filters. For maintaining the sulfate balance a modified jarosite leach is being used. After a two step purification the neutral solution is mixed with spent electrolyte and cooled in unpacked atmospheric cooling towers. Three electrical circuits are supplying the power to the tankhouse, each rated at 30,000 amperes. With a maximum current density of 750 amperes per square meter and a stripping cycle of 24 hours, an average current efficiency of 90 percent is obtained. Cathodes are melted in one induction furnace and cast into shapes, or alloyed with aluminum and copper for die-cast metal.

Jan 1, 1970

By W. O. Philbrook

An engineering analysis indicates that the coke rate in present blast-furnace practice is set not by chemical or thermal needs but to give adequate charge permeability for economical driving rates. An equation showing interrelations among pressure drop, gas flow, and charge characteristics has been derived. Flooding conditions and the location of the fusion zone are discussed. Maximum ore size is probably limited by chemical re-ducibility rather than by heat transfer. THE intention of this paper is to show that the ].imitations on the production rate and coke requirement of the iron blast furnace are not primarily chemical or thermal in nature but are related to characteristics of the burden and operation that govern gas flow, heat transfer, and stock movement. A semiquantitative analysis will be developed in terms of standard engineering principles to give a useful picture of the relative importance of physical and mechanical factors in contrast with the chemical features of the process that are more commonly emphasized. Most of the details of calculation have been omitted in the interest of brevity and to avoid submerging the rnain points in a sea of arithmetic. Numerical values have been arrived at by objective methods from reported operating data or by reasonable estimates of material properties where exact data are lacking and then tested to see how well they fit practice, rather than by working backward to find what assumptions are needed to give the desired answers. The analysis is oversimplified in many ways because exact engineering relations have not yet been studied for bed distributions as complex as are known to exist in the blast-furnace stock column. One objective of this paper is to show that the blast furnace, in spite of its complexity, can be at- tacked by engineering methods in the hope that this viewpoint will stimulate the kind of research needed for a more exact treatment. The basic ideas and many of the conclusions presented are qualitatively well known. A careful literature survey to credit the source of all observations not original to the author would indeed be voluminous, and such has not been attempted. T. L. Joseph's Howe Memorial Lecture' gives an excellent background of what is known about the internal workings of a blast furnace. Other important reference works or sources of specific information will be noted. It is hoped that the present paper will contribute something new, in method of attack and interpretation, that will aid in a clearer understanding of how to operate the blast furnace to best advantage. Factors Limiting Production and Coke Rates The rate of combustion of coke in a blast furnace, as in any fuel bed, is exactly proportional to the rate at which air is supplied. It is axiomatic, then, that the production rate of a furnace is limited by the rate at which it will take wind, i.e., burn coke, and the amount of coke that must be burned at the tuyeres to make a ton of iron of suitable composition. These two possible limiting factors will be considered briefly in the order mentioned. One common restriction on wind rate is flue-dust production. Since the volume of top gas is nearly proportional to the blast volume (by a factor of about 1.35 on a dry basis), an increased wind rate causes a correspondingly increased linear velocity of top gas in the throat of the furnace. The higher

Jan 1, 1955

By Ballard H. Clemmons

THE future of the steelmaking industry of the Birmingham, Ala., district is closely related to and, in a large measure, dependent on the development of workable, economic processes of ore concentration. Operations thus far in the area have been possible only because of the fortuitous occurrence of iron ore, fluxing stone, and coking coal-all the primary iron-making materials- within a 25-mile radius of the blast furnaces. Commercial ore of the district consists mainly of a 10 to 20-ft hematite-calcite-silica bed locally known as the "Big Seam," a component of the Clinton formation of Silurian Age. At present mining rates, this ore will be available for a number of years. It is largely mined under 1000 to 2000 ft of cover and transported on 15 to 20" slopes that, in some instances, are as much as 10,000 ft long. Under these conditions, particularly with increasing distances from face to portal, mining costs are gradually becoming disproportionately high. Although not a major factor thus far, it should also be noted that the average annual ore output of the district is gradually be- coming more siliceous.

Jan 1, 1950

By Bernt Ellingsaeter, Terkel Rosenqvist

IN the silicothermic reduction of magnesia, burned dolomite is treated with high grade ferrosilicon in an evacuated steel retort at temperatures between 1150° and 1200°C. The following reaction is assumed to occur MgO + CaO + 1/2 Si (Fe) - Mg(g) +- & Ca,SiO, + Fe with the equilibrium constant on the basis of thermodynamic data for the substances involved and assuming unit activity for all solid constituents, Kubaschewski and Evans' calculated the magnesium pressure as a function of temperature logp,, (mmHg) = 15.06-1.61 T- log T- 13,16O/T. Pidgeon and King," who measured the magnesium pressure by means of a flow method, found values about three times the calculated ones. This may be caused by uncertainties in the thermodynamic data, but may also be caused by the formation of other reaction products, such as Ca,SiO,, which is known to be the stable silicate in equilibrium with lime. Whatever the exact reaction may be, it is evident that as long as all other factors are maintained constant the magnesium pressure will vary with the silicon activity, viz: p,, = &,. (p,,) ", where (p,,)" is the magnesium pressure by the reduction with silicon of unit activity. In the present investigation, p,,, was therefore measured for various grades of ferrosilicon and their silicon activities were calculated. The experimental method was similar to that used by Pidgeon and King. Briquettes of burned dolomite and Fe-Si alloys were placed in a 1 in. heat resistant steel tube and were heated to 1200°C. By means of a flow of purified hydrogen, the magnesium vapor was swept into a condenser filled with steel wool. From the amounts of hydrogen used and magnesium condensed the magnesium partial pressure was calculated. First a tube of 28 pct Cr steel, and later a tube of Kanthal D (a ferrous alloy with 22.6 pct Cr, 2 pct Co, and 4.5 pct Al), was used as a heat resistant tube. The latter tube showed the best heat resistance. The dolomite used had the following composition: 43.6 pct MgO, 55.5 pct CaO, 0.2 pct K,O + NalO, 0.2 pct Fe,O,, and 0.3 pct insoluble. The ferrosilicons were prepared from 98 pct Si of technical grade (0.7 pct Al, 0.3 pct Ca, and 1 pct Fe) by melting with various amounts of electrolytic iron of high purity. The alloys thus obtained were analyzed on their iron and silicon contents, which added up to between 99 and 100 pct. The amounts of reactants were chosen so that there would always be an excess of the oxides, and the average decrease in silicon content during the experiments would be about 1 pct. Most of the reaction occurred in the part of the reaction mixture facing the gas flow. The change in the silicon concentration in the part facing the condenser was, therefore, negligible. To facilitate the reaction, about 1 pct fluorspar was added to the briquette mixture. Fluorspar does not enter the reaction, but is known to act as a

Jan 1, 1957

By C. W. Stratford

[During the last few years, the necessity for development work has been generally recognized by executives throughout the oil industry, resulting in greatly accelerated progress and the adoption of many noteworthy improvements in refining methods and equipment. Several years ago, the Associated Oil Co. decided to improve distillation methods with the object of reducing refining costs. This extremely interesting work was entrusted to the writer, and W. S. James, now Chief of Research for Studebaker Corpn. of America, was selected as the principal collaborator. The latter contributed much during his two years with the Associated Oil Co., to the development work that has followed. The writer extends to the Associated Oil Co. his appreciation for permission to disclose the details of distilling equipment. In petroleum refining the principal requisites of good economics are the separation of high-priced distillates from those of lower price; maxi-mum yield of any desired distillate; lowest capital investment in refining equipment; lowest cost of operation and maintenance, and the best adaptability and flexibility of the same refinery equipment for handling crudes of widely varying characteristics. The first two items mentioned, separation and yields of distillates are determined by efficiency of fractionating equipment,. Discussion in this paper is chiefly concerned with oil-heating equipment, combustion and furl economy. It has long been well known that velocity plays a very important part in all heat transfer systems. Any betterment in specific transfer. rates in such systems must. always involve velocity. Realizing this fact, IV decided to adopt as a basic principle, the employment of energy to impart velocity required for high transfer rates through a heating diaphragm, and our method of modernizing obsolete shell stills is founded on this principle. Mechanical energy is usually cheap and its rational rspcntliture is returned in the form of greatly increased heat transfer rates, on both oil and gas sides of the sheet. Certainly there is nothing new in this principle, the only novelty being that of our peculiar method of application On the oil side (Fig. I) use is made of a centrifugal pump to jet the oil against the heated sheet thereby creating a high velocity sheet flow over the entire fired area. Such a pump is one of the most efficient machines, so far developed, for moving fluids. 'I'he oil, under pressure impinging

Jan 1, 1928

By G. J. Ballmer

Drilling and blasting 12-in. blastholes started about the middle of 1946 and has worked out so well that about one half of the blasting, formerly done with 9-in. holes, is now done with 12-in. holes. In most of this work the harder benches were chosen for the 12-in. size because these were the areas where the greatest difficulty was encountered in thorough fragmentation. At the start of this experimental work a 42-T Bucyrus- Erie churn drill was available whereas all other blasthole drilling was being done with 29-T rigs. The large drill was first equipped with a standard 9-in. string of tools but it could not drill quite as fast as the 29-T drills. How- ever, when the weight of the string was increased about 700 lb, or to a total weight of about 3500 lb, it was found that the 42-T exceeded the drilling speed of the 29-T by about 25 per cent. When a 12-in. bit was substituted for the 9-in. bit the 42-T rig again dropped behind the drill- ing rate of the 29-T rigs. At this stage of the experiment the 42-T was using a 12-in. bit with detachable points and the total weight of the string of tools was about 3800 lb. It took longer to change the drill points than it did the regulation bit and this accounted for some of the slower drilling rate. When a heavier stem and standard construction 12-in. bits were used it was found that the 42-T could drill a 12-in. hole slightly faster than a 29-T could drill a 9-in. hole even in the hardest rock in the pit.

Jan 1, 1949

By R. S. Wagner, R. G. Treuting, W. C. Ellis

Use of the Weisseizbevg goniometer for the study of the morphology of whisker crystals and transfer of the results to a stereograplzic projection are described. While in almost all instances a complete and rapid solution is obtained with a purely gaphical treatment, an absolute analytical treatment applicable to difficult cases is given. Examples are given for determination of growth direction and external features of a crystal, for detection of 'twintzittg, and for establislting the orientation relntionships in a kinked whisker crystal. We give here a method for the use of the Weissen-berg goniometerl" in the study of orientation relationships in "whisker" (micro) crystals3-8 and direct transference of the data to the stereographic projection. The operations are straightforward and require no involved calculations: in almost all cases solely graphical treatment is adequate. In a few complex instances, a more exact analytic method may be required. In the method, not only are equatorial reflections of an oscillation photograph used, but also those on higher layer lines, or those not occurring on a recognized layer line. Such reflections off the zero level are often essentialy to detect the presence of twinning. The method is particularly suitable for examination of whisker crystals since the axial or growth direction is almost always one of high symmetry, permitting a more restricted oscillation range to obtain the necessary reflections and an accordingly shorter exposure time. The method is also applicable when there is no lattice-related external symmetry, and is as well able to identify external crystal surfaces, when such exist, with the aid of an optical beam. Thus growth direction, identification of lateral faces, twinning, and orientation relationships in a kinked crystal can be established. A test for the Eshelby twist6-8 can readily be made. The method can be used for orientation, for structure analysis, and as an aid in the identification of an unknown crystal. Moving-film techniques have previously been employed variously for crystal-orientation studies.1,2,9-13 In particular, use of the Weissenberg method for orientation determination has been reported by Wooster and wooster.14 While their method derives the same data as here described, it differs in depending on the tracing of constant p streaks, a less than dependable phenomenon with small specimens, a few microns or less in cross section. The Laue method can and has been used for orientation studies of microcrystals,15 e.g., 2 p in cross section, but requires the extreme intensity and concentration from a microfocus tube to obtain reasonable exposure time. PRINCIPLES OF THE PRESENT METHOD Consider a crystal of random orientation with respect to the oscillation axis in a Weissenberg goniometer. Its diffraction pattern need not necessarily result in recognizable layer lines. In Fig. 1, a stereo-graphic projection of the reference sphere is given with the equatorial plane XZ normal to the oscillation axis Y, and the X-ray beam directed from X towards 2. The great circle ZZ is then normal to the beam, and the axes are right-handed. Thus the reflected X-ray beam lies at the intersection R of small circle ARB of radius 28 from 2, and of small circle RE of radius a from the rotation axis Y. a is the conventional semiapex angle of a cone of diffracted rays from the atoms aligned in the direction

Jan 1, 1967

By R. F. Rolsten

The preparation of pure metals by the thermal decomposition of volatile halides was developed byde boer' and van Arkel.2 This has proved to be a useful technique for the refining of columbium,the mechanical and physical properties of which are seriously altered by such interstitial contaminants as oxygen, nitrogen, hydrogen, and carbon. The conventional deposition surface of a resis-tively heated metal filament was replaced, Fig. I, with an indirectly heated clear quartz surface. The impure columbium (feed) was contained in the annular space between the Vycor deposition bulb and the perforated molybdenum retaining cylinder. The head assembly was attached to the deposition bulb by fusing the Vycor at "A". This unit was then connected to a vacuum system composed of a three-turn glass coil to eliminate fracture due to vibration or expansion, a McLeod gage, a cold trap, a two-stage mercury diffusion pump, and a mechanical pump. The entire system was cold outgassed, and the 10 to 20 g of iodine in the auxiliary bulb (reservoir) was held in dry ice to prevent excessive loss of iodine. The columbium was hot outgassed at 800" to 825oC with the pressure maintained at l0-5 to 10-6 mm Hg for 48 hr and cooled under vacuum to 200° to 240oC. Iodine was sublimed from the reservoir and collected in the deposition bulb. The feed material temperature was adjusted to give the desired iodide vapor pressure and the finger temperature of 1000" C was independently attained and measured with a platinum-platinum 10 pct Rh thermocouple located in the center of the nichrome wire helical heating element, "F." The system was attended until temperature equilibrium was established, whence it operated without attention. This is a definite ad- vantage over the conventional "hot-wire" technique which required either constant attention or automatic control. In operation, the iodine vapor originally introduced into the vessel reacted with the crude metal to form a columbium iodide. This iodide vapor diffused to the hot deposition surface where it thermally decomposed, depositing columbium and releasing iodine. This liberated iodine then diffused back to the crude columbium where iodide was formed again. Thus, by repetition of this process, the iodine carried pure columbium from the crude material to the filament, where it deposited. The success of the "iodide" process in producing ductile metals depends on preventing the transfer of oxygen, nitrogen, hydrogen, and carbon from the feed material to the deposit. In many cases relatively minor quantities of these interstitial contaminants impair the ductility of metals. The material produced by the iodide process has such exceptional ductility that it is frequently and mistakenly assumed that iodide metal is always of very high purity. This assumption is not necessarily true since a number of metallic impurities can also be transferred. In the present investigation, the temperature of the feed material was adjusted to iodinate selectively and the deposition temperature adjusted to decompose the iodides selectively. By this technique, some metals present in the feed material were prevented from codepositing with the columbium. It is quite important to have the feed material symmetrically located around the deposition surface in order to obtain a uniform deposit at the maximum rate. For example, Runnalls and pidgeon3 observed that, when the base of a titanium filament was about 1 cm from the feed material, deposition was rapid on that section close to the feed, but that the rate decreased with distance from the feed so that a

Jan 1, 1960

By Charles H. White

METHODS in colorimetry are based on the assumption that the intensity of the color of a definite volume of solution is directly proportional to the quantity of the color-producing substance' present. In the preparation and examination of colored solutions there are three ways in which the depth of color may be varied. These variables are; (1) the quantity of the coloring matter, (2) the quantity of the solvent, or the dilution, and (3) the thickness or depth of that portion of the solution examined. With these three variables as a basis, three general methods in colorimetry have been devised, all of which have been used in the determination of carbon in steel. In the first method, the quantity of the solution is kept the same for both the unknown steel and the standard, and the sections compared are of equal thickness, while the quantity of the standard is varied until the color obtained is of the same intensity as that produced by a definite quantity of the unknown steel. In laboratories where this method is used there is pre¬pared and kept for permanent use a series of solutions with varying amounts of the standard, representing the percentages of carbon from the lowest to the highest demanded in that laboratory. These standard solutions are kept in bottles, or test-tubes of equal diameter, and are arranged in series from the faintest to the most intense color, so that it is a simple matter to find the place of the unknown steel in the series, when the solution is of a definite volume and is contained in a tube of the same diameter as the standard tubes. In the second method, equal quantities of the standard and of the unknown steel are dissolved, the standard is diluted to a definite volume, and the solution of the unknown steel is di-

Sep 1, 1906

By F. A. Crossley

The additions: o, Sn, Zr, Cb, Mo, and V were studied for their effects on the a/a + Ti3A1 boundary of Ti-A1 base ternary alloys. These additions were chosen because of their importance to commercial titanium alloy practice—oxygen as the major impurity (in terms of influence on mechanical properties) and the others as major alloying additions. The composition and temperature ranges of investigation varied according to the system as shown in Table I. The principal means of investigation was light-microscopy. The basis of the ternary studies was the recently determined titanium-rich end of the Ti-A1 system.' MATERIALS, METHODS, AND PROCEDURES Ingots were prepared in 15 g size for all alloys except those of the Ti-Al-Mo and Ti-A1-V systems which were prepared in 20 g size. These alloys were prepared from high-purity, electrolytically refined titanium obtained from the Bureau of Mines, Boulder City Metallurgical Laboratory, Boulder City, Col., and Chicago Development Corp., Riverdale, Md., for the 15 g and 20 g ingots, respectively. The alloying additions were obtained from commercial sources, and were at least of 99.9 pct purity, except the V-15 wt pct A1 master alloy for vanadium additions. This alloy was of 98.2 pct purity; the major impurities were 0.37 wt pct Fe and 0.38 wt pct Si. The ingots were prepared by multiple melting in a nonconsum-able-electrode arc furnace. The ingots were covered with Markal coating "CR-T22" (Markal Co., Chicago) to protect them from scaling. Markal coating is applied as a slurry of solids in a volatile carrier liquid. The coated article is air dried. Upon heating to the hot working temperature the coating fuses to form a glassy, protective film. The ingots were heated to 1000°C and rolled to 0.16 in. thickness, reheating after each pass. The glassy film was removed by sand blasting. Ten mils were removed from all surfaces by grinding and/or pickling (3 pct HF, 30 pct HN03, balance water). Grinding was always followed by pickling to remove traces of the grindmg medium. Hydrogen removal was accomplished by vacuum annealing at 1000°C for 2 hr to a final pressure of about 0.02 µ Hg. This was followed by annealing in evacuated Vycor bulbs (800°C, 2 hr, ice brine quenched (IBQ)) in order to maximize ductility. The materials were then lightly pickled and cold rolled to 0.12 in. thickness or cracking, whichever occurred first. After rolling, 1/2 by 1/4 in. specimens were cut for the equilibration anneals given in Table 11 and carried out as previously described.1 Final polishing of the specimens for metallographic examination was done by electrolytic means. Specimens were first examined without etching under bright field and polarized light illumination, for this is the only means of detecting the "two-phase" phenomenon.1,2 The term "two-phase syndrome" refers to Ti-A1 al-loys which appear on the bases of their chemical, phys-ical, and mechanical properties, to be two-phase, but are actually single phase and inhomogeneous in composition. Since processing and heat treatment of the alloys of the first group were completed before the two-phase syndrome was discovered, a number of the specimens were found to exhibit this phenomenon—80 pct of those of the Ti-Al-Zr system, 5 pct of those of the Ti-Al-Sn system, 30 pct of those of the Ti-Al-Zr system. The affected specimens were homogenized by heating above the ß transus temperature and quenching. The heat treatment and working schedules to accomplish this are given in Table 111. After rolling, specimens were pickled (3 pctHF, 30 pct HNO3 in water) to remove 1 to 2 mils from the

Jan 1, 1970

By R. M. Fowler, H. L. Hamner

DURING the last 25 years, there appeared in the literature a number of papers describing equipment and operating techniques for the determination of total oxygen in iron and steel. In the early papers, comparatively little attention was paid to side reactions that occur when iron is saturated with carbon at a high temperature in a high vacuum. As more experience was gained with the new method, the limitations appeared. Metals, with a boiling point lower than iron, distilled out of the crucible, condensed in the cooler part of the furnace, and subsequently reacted with carbon monoxide to form oxides and carbon. Aluminum, manganese, and the alkaline earth metals proved troublesome in this respect. Modifications have been devised to overcome the difficulties due to aluminum and manganese, while the alkaline earth metals are not of too much concern as yet to the steel chemist. The reactions of sulphur have received less attention, although it is generally recognized that some carbon disulphide is probably formed. Liquid air traps have been used in some cases to prevent any carbon disulphide from entering the analytical train. Sulphur was not a particular problem at the Union Carbide and Carbon Research Laboratories until the analysis of the irons of higher than usual sulphur contents became necessary. In order to describe the procedure developed for such irons, it will be necessary to first describe the type of vacuum-fusion equipment employed because the operation of vacuum-fusion equipment is an art to a considerable extent. At the Laboratories, vacuum-fusion equipment has been in daily operation since about 1930. Over the years, the evolution of this apparatus has been governed by the versatility required to analyze a wide variety of materials. Since all types of materials from high purity metals to slags are analyzed and, since seldom more than a few samples of one type are analyzed in succession, the apparatus was designed for accuracy and flexibility rather than for speed. A general view of the equipment is shown in Fig. 1, while Fig. 2 shows the relationship of the various parts. In Fig. 2, A is a vertical double-glazed 24X27/8 in. OD silica tube heated with a 20 kva mercury-arc high frequency generator. The tube is closed with a water-cooled brass head attached with de Khotinsky cement. A turret cap fits on this head and is sealed with a 1/8x3 in. "0" ring. The head contains a sight glass and two 8 in. horizontal glass tubes, for sample storage, cemented in with de Khotinsky cement. B is a four-stage Gaede mercury diffusion pump connected to the water-cooled head with a 11/2 in. copper tube through a flange with an "0" ring. The output of the vacuum pump feeds into an automatic Toepler F pump which compresses the gas sample over mercury in the measuring burettes, G and H. There are bypasses in this line for a McLeod gage C and a Piranni gage D, a manometer E, and for initial pumping out of the system with a Cenco Megavac backing-up pump. The reduction crucible shown in Fig. 3 is machined of Tungar Bulb quality (A.G.K.T.E.-2) graphite. The sample is guided into the crucible with the graphite funnel depicted on this figure. The arrangement of the crucible, radiation screens, etc. in the furnace is as follows: A 1 15/16x61/2 in. Alundum thimble, porosity RA-84, with two 1/8 in. holes near the top and opposite each other which take a pair of special tongs used for lowering it in place, is prepared. A 3/4 in. layer of powdered graphite is placed in this Alundum thimble, and the graphite crucible containing 20 g of ingot iron and 0.5 g of carbon is carefully centered on this bed of graphite powder and graphite powder is packed around it to the top of the graphite cru-

Jan 1, 1953

By Edward B. Dismukes, Walter R. Dickson

Measurements of current efficiency at an iron anode during the electrolysis of FeO-CaO-SiO2 melts contained in an iron crucible indicate that compositions of high SiO5 content conduct current almost entirely by ionic mechanisms. Hozueuer, compositions of high metal oxide content give euidence for considerable nonionic conduction that can be attributed to p-type semicon-duction. Measurements of transference numbers in a Hittorf-type cell show that both calcium and iron ions are important contributors to ionic conduction. ELECTROCHEMICAL properties such as conductance, transference numbers. and oxidation or reduction at an electrode have been studied as means of delineating the structure of simple silicate melts that are related to the more complex slags encountered ir steelmaking processes.' Measurement of these properties has strengthened the concept that molten silicates are constituted of metal ions and of silicate networks. Typically, the magnitude of electrical conductivity and the extent of agreement with Faraday's law have given evidence for ionic structures, and transference numbers have shown cations to be the exclusive carriers of electrical charge. However, melts containing oxides of iron, FeO in particular, have been found to exhibit nonionic conduction of curx,ent. The work by Inouye, Tomlinson, and chipman' demonstrated semiconduction, presumably of the p-type, in molten wüstite. Simnad, Derge, and George3 and Dukelow and Derge,4 in studying the electrolysis of FeO-SiO2 and FeO-MnO-SiO2 melts, concluded that p-type semi-conduction occurs in these systems, although ionic conduction is generally favored by increased percentages of MnO or SIO2. Previous research on the electrochemistry of

Jan 1, 1962

Jan 1, 1893

By J. A. Cahill, A. D. Kirshenbaum

Using an alumina or zirconia crucible with an alumina sinker or a molybdenum sinker coated with zirconium dioxide, the density of liquid iron was determined by the immersed-sinker method over the temperature range of 1800" to 2500°K. The density, with respect to temperature, is ex-Dressed by the equation Dg/cm = 8.523 - 8.358 X 10 T'K The molar Volumes and thermal coefficients of expansion were calculated. Iron, upon me1ting, was found to expand 3.5 pct. A basic knowledge of the physical properties of materials at high temperatures is becoming increasingly important. A check of the literature shows, that in spite of the importance of iron, very few measurements have been made of its physical properties in the liquid state. Density measurements have been made by Benedicks and his collaborators1g using the method of balanced columns, by Desch and smith4 using the immersed sinker method with an alumina sinker, by Lucas using the maximum bubble method5 and by Stott and endall' who used an alumina pyknometer. In the method of balanced columns, the difference in level of molten iron in two arms of a U-tube, together with the corresponding difference of pressure had to be measured. The formation of gas bubbles in one or both arms was a great source of error. These values are very erratic. They vary from 6.83 to 7.45 g per cm3 at the melting point (1805"~) and from 6.45 to 7.15 g per cm3 at 1890°K. Stott and Rendall determined the density at 1837"K, with a reproducibility of *0.2 pct. They used an alumina pyknometer fired to 1973°K. The vessel was filled in a vacuum furnace by immersion in the liquid metal. When thermal equilibrium was attained, the pyknometer was withdrawn, cooled, the ingot removed and then weighed. The chief disadvantage of the method was the difficulty of inserting the pyknometer without cracking it. The authors have been able to determine the density of liquid iron from its melting point up to 2500°K, by using the immersed-sinker method, with A1203 or ZrOz crucibles and A1203 or molybdenum sinkers coated with Zr02, Fig. 1. EXPERIMENTAL Apparatus. In these studies the source of heat was the carbon tube resistance furnace with an argon atmosphere described previously.7 Experimental runs were made using either Ala3 or ZrOz crucibles. The sinkers used were 1) pure A1a3 and 2) molybdenum coated with ZrOz. The crucible, 2 1/8 in. in diam and 3 in. high, was centered in the furnace on an Ala3 of Zr02 pedestal. The sinker, 1/2 in. in diam and 1 1/2 in. long, together with a counter weight, was suspended from an analytical balance into the melt by a molybdenum wire. Procedure. The procedure, as described previously,' consisted in measuring the weight loss of the sinker in the liquid iron while determining simultaneously the liquid iron temperature by means

Jan 1, 1962

By M. Cohen, C. Wagner, J. E. Reynolds

If the total volume of a diffusion couple changes during the diffusion, the measurement of distance becomes ambiguous. Use of distance parameters as suggested by Hartley and Crank is discussed. For small concentration differences, the standard form of Fick's second law is retained with conventional length units and the in- terdiffusion coefficient D. It is shown how D can be calculated from experiments involving large concentration differences and analyzed in terms of distance parameters. 'The merits of incremental diffusion couples involving small concentration differences are emphasized. THE conventional form of Fick's second law for one-dimensional diffusion of component B in a binary solution of A and B is where c, is the concentration of component B; x, the distance; t, the time; and D, the interdiffusion coefficient which may depend on ca. Hartley and Crank' have pointed out that Eq. 1 applies only if the total volume of the diffusion couple does not change during the diffusion process; otherwise, the definition of x becomes ambiguous. No change in total volume takes place if the specific volume of the solution is a linear function of the weight fraction Wb, or if the molar volume is a linear function of the mol fraction N. In some alloys, however, these relationships do not hold, and then it is necessary to introduce a modified measure of distance, 4 in order to retain the general form of Eq. 1. The application of Hartley and Crank's suggestions to diffusion in alloys has been discussed by Wagner.' Relation Between Measure of Distance and Units of Concentration The definition of [ depends on the choice of units for the concentration c,, as follows: 1—If the concentration ca is measured as the weight fraction W, (or weight percent), [ = 5, has to be defined so that equal increments of contain equal increments of mass m of the solution, e.g., dm = pSdx = Sdw [2] where p is the local density of the solution, and S is the cross-sectional area in sq cm which is taken to be constant in this problem of one-dimensional diffusion." * da Silva and Mehla have demonstrated the constancy of the cross-sectional area in the usual type of diffusion couple. However, experiments involving diffusion into thin wires4, 5 may exhibit changes in cross-sectional area, and therefore are excluded from the present treatment. Thus and the unit of is gram per sq cm instead of cm. 2—If the concentration c, is the mol fraction N, must be defined so that equal increments of contain equal numbers of mols of solution, e.g., dn= (S/V)dx= Sd [41 where V is the local molar volume of the solution. Thus dt, = dx/V [51 and the unit of is mols per sq cm. 3—If, as may be advisable in the case of interstitial solutions, the concentration C is measured in terms of the molar ratio of components B and A (c,, = Y, = nH/nA, where n and nl are numbers of mols of B and A), = Y has to be defined so that equal increments of contain equal numbers of mols of A, e.g., dnA= (NAS/V)dx = Sdf [6]

Jan 1, 1954

By Henry G. Granger

A RESIDENCE of 14 years in the Republic of Colombia, spent in almost continuous traveling and prospecting-trips, has given me an intimate knowledge of the resources of that wonderful country. The man who best knows Colombia is unquestionably General Rafael Reyes, President of the Republic for the past three years, and with seven years more to serve in his present term. Such is the strength of his personality and the wisdom of his policies that his term of office will no doubt endure as long as he is willing to serve. The vastly improved economic situation and the brilliant outlook for Colombia are so directly due to the influence of President Reyes that a few lines concerning him. will not be amiss, if they serve towards a better understanding of his personality. Born of a distinguished ancestry in the mountains of Boyaca, he is now 57 years old, just the age of his friend Porfirio Diaz when be began the work which has placed Mexico in the rank of great modern nations. It was Reyes who came to Washington to protest against the action of the government of the United States of America in reference to the establishment of the Republic of Panama, and, without entering into a discussion of this affair, it can be fairly said that there was not an American in Colombia whose feelings of justice were. not outraged at the government action and subsequent refusal to submit the matter to the impartial judgment of the' Hague. President Reyes is an accomplished linguist, speaking English, French, German, Portuguese, Spanish, and Italian. He has a remarkably. powerful voice, which can readily be heard by a large assemblage. His height is about 6 ft., and his weight exceeds 200 lb. He has clear gray eyes. Reyes was the leader of those who favored the approval of

Sep 1, 1908

By M. J. Salkind

In order for fiber composite materials to find extensive use in structures, it is necessary to develop techniques for joining these materials. Riveting and adhesive bonding are two possible techniques which have been investigated although the former is less desirable because the low shear strength of most matrices makes this type of joint subject to bearing failure. Welding is an effective means of joining, especially for high-temperature applications where ad-hesives are weak; however, there are significant limitations placed on welding composite materials. The commonly used fusion welding techniques will find less use for joining composites because the two phases are often unable to stand exposure to such a stringent environment. In the case of eutectic composites, fusion welding will completely destroy the controlled microstructure. Solid-state techniques such as diffusion bonding offer potential success with certain design requirements placed on such joints. Since the primary mechanism of load transfer from matrix to fiber is shear parallel to the fibers, little load can be transferred across a butt-welded interface perpendicular to the aligned fibers. Successful joint designs must have a component parallel to the fibers to allow a shear area for load transfer. Configurations such as lap and scarf welds are likely to be successful. This note describes some results of experiments with diffusion-bonded joints in A13Ni whisker-reinforced aluminum. The composite material, prepared by unidirectional solidification of the A1-A13Ni eutectic, is described elsewhere.'-' It consists of aligned micron size whiskers in a matrix of aluminum. Since it has been shown that the microstructure of

Jan 1, 1969

By John McDonald

THIS report is a continuation of an earlier one with a similar title,1 to which the reader is referred for such details of procedure as do not appear here. A brief summary will be given of the objects and methods of the research at this time. It was pointed out in the previous paper that properties of magnesium alloys, as re-ported by different workers, often differ. This was thought to be due to differences in the preparation of the specimens tested. The ideal way to compare alloys would be to prepare each of them in so many ways that reasonable assurance would exist that the best properties of each alloy had been developed. The alloys would then be com-pared on the basis of these properties. The treatment actually given the alloys of these studies is necessarily a compromise with completeness. Nevertheless, enough treatments have been given so that a con-siderable degree of assurance exists that the properties obtained are representative of the alloy as such, and not merely of the manner in which it was worked and heat-treated.

Jan 1, 1940

By Joseph Hartshorne

EVER since the introduction of the Siemens regenerative furnace, it has been recognized that a certain amount of gas is lost each time the furnace-action is reversed. This loss comes, first, from the gas which passes through the free connection between the stack and the gas-main, which exists during the time the reversing-valve is turning over; and, secondly, from the gas which is in the chamber and flues, from the hearth to the reversing-valve, and which flows back into the stack when the valve is reversed. The amount lost each time is, of course, small; but, since a furnace is reversed from four to six times every hour for, say, 300 days in the year, the aggregate is large enough to be well worth attention. The estimate has been published' that, in Germany alone, the loss from the first of the above causes amounts to 500,000 marks per year. The loss from the second cause is, of course, much greater. A process for saving this entire loss, in use at Teplitz, Bohemia, for about three years, would seem to be of value even in this country, where coal is cheaper and where the small economies are not watched as closely as they are in Europe. This process, invented by Mr. Adelbert Kurzwernhart, late Technical Director of the Teplitzer Walzwerk, has been worked out with thoroughness. The loss from each cause can be calculated very closely for any particular furnace, and the results to be expected from the process ascertained. It can easily be decided, therefore, whether it is worthwhile to adopt it under any given conditions. The amount of chamber-gas lost depends upon,-(1), the cubic contents of the chamber, ports and flues upon one side of the furnace, up to the reversing-valve (deducting, of course,

Mar 1, 1906

By Lawrence Adler

MINE hoist ropes have hitherto been selected by successive approximation, a process both tedious and inexact. The proposed expression is a readily solved synthesis of existing data and the following standard equation:' [ W + Wr + (W + Wr) -a 9 (W + W)f + b] n=T [1] For convenience, a glossary of all terms appears on page 564. Since rope weight (W,) and bending load (B) are functions of unit rope weight (Wv), which in turn is a function of rope strength (T), W, and B can be expressed in terms of T. W, as a Function of T: A study of the curve in Fig. 1, unit rope weight vs strength, yields Eq. 2: W. = -f- [2] Therefore Wr = WvL = T. [3] iv B as a Function of T: From Fig. 2, unit rope weight vs diameter, Eq. 4 is obtained: W, = 1.6d2 [4] B is related2 to d and D, and d has been expressed in terms of W, by Eq. 4, so the curve B vs W, (Fig. 3) gives Eq. 5: 177,000 177,000 This may readily be checked from the expression3 for a 6x19 rope, i.e., d3 B = 288,000D Since d2 = 0.625 W, and N = substituting d into the above expression gives Ea. 6: 180,000 180,000 B T, which will be used. [6] Into Eq. 1 substitute Eq. 3 and Eq. 6, noting that f=0.02: W + T 1.02+=T. [7]

Jan 1, 1958