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By J. S. Pascover, J. K. Abraham

The influence of the early stages of precipitation on the kinetics and structure of martensite formation in Fe-27Ni and Fe-29.5Ni alloys containing from 0 to 10 pct Ti was examined with X-ray and electron microscopy techniques. The formation of a coherent, ordered preprecipitate had a profound stabilizing effect on the austenite. The Ms was decreased by increased titanium content and aging time up to a critical time. When the critical aging time was exceeded, the Ms was observed to increase markedly. The formation of the clusters was insuppressible and the volume fraction of clusters formed during the quench was a function of the titanium content. Martensite resulting from transformation of the clustered austenite is tetragonal with the c/a ratio increasing with titanium content. A model for the tetragonality is suggested. The morphology and substructure of the m artensite is inter-preted in terms of the above information and the cur-rent models of twinned martensite. ThE ramifications of precipitation in austenite to the properties of austenite have been the subject of numerous investigations. The current research is concerned with the influence of precipitation in austenite on the kinetics and structure of subsequent marten-site formation. In a previous investigation, Abraham et al.1 followed the aging reaction in an Fe-29.5Ni-4.2Ti* (at. pct) alloy using an X-ray diffraction technique. This technique, employing a Guinier camera, provided kinetic measurements through observation of the side band position as a function of aging time. The salient results of this work were: 1) The initiation of precipitation was not suppressed by quenching, i.e., there was a finite cluster zone size at zero aging time; and 2) The hardness of the aged austenite correlated extremely well with the zone size. During the previous work it was noted that the mar-tensite formed after aging was tetragonal, substanti-ating an earlier observation.2 Systematic investiga-tion revealed that the martensite was tetragonal in both the solution-treated then quenched, and the solu-tion-treated, aged, and quenched condition, and, furthermore, that a marked stabilization of the austenite occurred as a function of aging time. The present work is concerned with documenting the tetragonality and the stabilization phenomena as well as the ob- served microstruction with a suggested rationale for the behavior noted. EXPERIMENTAL PROCEDURE The compositions of the alloys are listed in Table I. The analyses were performed after the solution treatment of the strip material. Nickel was determined using the standard dimethy1-glyoxime procedure whereas titanium was determined colorimetrically with hydrogen peroxide and volumetrically by titrating with ferric iron. The materials were melted in a 5-lb vacuum induction furnace, cast into 2-in.-diam ingots, and forged in a temperature range of 950. to 1200°C to 1/2-in. slabs. The three higher titanium containing materials cracked during forging; therefore, to get the alloys into strip form, slices 1/8 in. thick were cut from the slab, homogenized 4 hr at 1150°C, then cold-rolled to a 0.04-in. thickness. The remaining slabs were hot-rolled, homogenized 4 hr at 1065"C, then cold-rolled to a final thickness of 0.03 in. All of the heat treatments were performed under a protective atmosphere of argon. The Ms temperature for most of the alloys is below room temperature; therefore, it was possible to solution treat, quench to room temperature, polish, and then observe the transformation optically on a cold-stage microscope. To determine the effect of aus-tenitizing temperature on Ms, eight of the alloys were treated at two temperatures, 1025" and 1120°C. No measurable variations in Ms were noticed. The remaining alloys were treated at 1025°C. The specimens, : by 5/16 by 0.03 in., were austeni-tized in a vertical tube furnace under a dynamic argon atmosphere. The bottom of the tube was submerged in water for quenching purposes. The question of stabilization that may be operating at room temperature was investigated and found to be negligible. Many of the specimens were held at room

Jan 1, 1970

By Strathmore R. B. Cooke, Emert W. Lindroos, Norman F. Schulz

DURING the course of an investigation of the effects of various starch products on hematite and quartz in regard to their separation by' flotation, it was found that whereas most starches flocculated suspensions of hematite in water, they did not flocculate similar suspensions of quartz. However, a derivative of whole corn starch containing approximately one tenth aminoethyl group (--CH2CH2NH2) per glucose unit proved to be an exception. This aminoethyl starch was a very good flocculant for both hematite and quartz, and also possessed the property of depressing both minerals in cationic flotation tests. In view of the widespread use of starch as a flocculating agent of solids in tailing water, pulps, and for coal slimes, ore and various other purposes in sulphide and nonsulphide flotation, attention is called to the effective surface activity of aminoethyl starch in flocculating suspensions of the two minerals investigated. Test Materials The starch products employed included Globe Pearl starch No. 144 and fresh aminoethyl starch, both supplied by the Corn Products Refining Co. Dr. A. L. Elder[4] has kindly furnished a description The minerals used in the various tests are listed in Table I. Their specific surfaces were determined by the air permeability method, which gave results reproducible to within plus or minus 3 pct. Surface areas obtained by krypton adsorption were greater than the air permeability values by a factor of 2.0 for quartz and 62.4 for hematite. Starch Adsorption on Mineral Surfaces Starch adsorption data were obtained by agitating for 1 hr measured volumes of neutral starch solutions of known concentrations with weighed quantities of finely divided mineral of measured specific surface. The mineral then was separated from the pulp liquor by centrifugation and the residual starch content determined by chemical analysis. The analytical procedure consisted of oxidizing the starch with an excess of dichromate in acid medium at elevated temperature and titrating the excess dichromate by the ferrous ammonium sulphate-potassium permanganate method. Analytical results were reproducible to within less than 1 pct. Adsorption data obtained in unbuffered solutions near the neutral point are plotted in Fig. 1. The adsorption on either mineral was far greater for the aminoethyl starch than for the Pearl starch. Flocculation The degree of flocculation was determined for a given pulp by measuring the time required for the supernatant liquid to reach a certain degree of clarity. This was accomplished by passing a standard light beam through the pulp, contained in a glass settling tube, and measuring the time required after agitation ceased for the intensity of the transmitted beam to reach a predetermined value. Starch reagent was added to each pulp in small uniform increments, and the settling time was determined after each such addition. Increase in pulp liquor volume due to the added starch reagent was ignored in these tests. Pulps were maintained at or near neutrality.

Jan 1, 1952

By AIME AIME

THE fifth annual fall meeting of the Petroleum Division of the A. 1. M. E. went down into history as being one of the best ever held by this Division and marked progress was made in the concentration of sentiment regarding several matters-particularly the principles of unit control or operation of oil pools. The first day's program was devoted to the discussion of well spacing and many valuable data were assembled and presented and the discussions following the reading of the different papers was interesting and spirited. However, throughout the whole trend of the discussion it was noted that in the background there was the idea of unit control of the pool and if such a condition could be secured the well spacing theories could be applied much better than could be hoped for if each lease in the pool was treated as a separate and individual unit.

Jan 1, 1929

By J. H. Hensley

The mine of the Miami Copper Co. is in the Miami district, Gila County, Ariz., approximately 7 miles west of Globe. In 1906, the General Development Co. secured the ground now owned by the Miami Copper Co., and about a year later discovered ore in a prospect shaft at a depth of 220 ft. The Miami Copper Co. was organized in 1907, the claims held by the General Development Co. were transferred to it, and an active development campaign was inaugurated. The railroad was extended from Globe to Miami in 1909, a concentrating plant was constructed, and the company began producing early in 1911. The unit size of mineral tract in the district is the standard lode claim 600 ft. in width by 1500 ft. in length. Ownerships of land are held in fee. The geology of the district has been described by F. L. Ransome.' The formations of local importance are: The pre-Cambrian Pinal schist, which consists mainly of metamorphosed sedimentary rocks and is commonly of a thinly laminated sericitic variety; the diabase, which is thought to have been intruded in late Paleozoic or early Mesozoic times; the Schultze granite and granite porphyry, considered early Tertiary; the dacite of late Tertiary time; and the Gila conglomerate of early Quaternary. General Items Influencing Mining Methods The bodies of disseminated ore in the district are flat lying masses of irregular outline and variable thickness. As a rule, these masses lack definite boundaries; the orebody follows a curve along one of the main ridges, approximately 5500 ft. in length with a maximum width of 1600 ft. The minerals occur as finely divided and uniformly disseminated chal-cocite in the Pinal schist and Schultze granite. The typical overburden or capping is a barren rusty brown, very friable, highly siliceous, leached schist, or granite-porphyry. The topography of the district is fairly rugged and irregular; the altitude ranges from 3400 ft. above sea level, at the town of Miami, to 3900 ft. on the hills above the Miami orebody. The climate is mild; the mean annual temperature is 63.°F.

Jan 1, 1925

By D. R. Hanson

The acoustic vibrational spectra of impacted rock slabs were examined at the Denver Research Center, US Bureau of Mines, in an attempt to characterize the behavior of partially detached mine roof rocks. The ultimate goal of this study was to develop a technique or instrument that could provide a quick, accurate, quantifiable measure of mine roof stability. The power spectra of unstable rock slabs were found to contain more energy in the range of 200 to 1000 Hz than solid rock. Comparison of the power contained between 500 and 1000 Hz with that between 3000 and 3500 Hz provided a quantitative measure of rock stability. A lightweight prototype field instrument was designed, constructed, and field tested. This battery-powered instrument computes the power contained in the two frequency bands, compares their magnitude, and displays a number related to the stability of the block tested. Field tests showed the instrument provided reliable measurements of block stability even under conditions of noise that would have seriously degraded the accuracy of the standard methods of roof sounding.

Jan 1, 1986

By Paul R. Wieber, Atam P. Sikri

This paper describes the U. S. Energy Research and Development Administration's (ERDA) program to develop in situ coal conversion processes, especially gasification. The potential of this technology, the technical directions being explored, and the program strategy to carry the process concepts toward commercialization are emphasized. The geographic location of the U. S. coal resources and a market analysis are described. Commercially successful in situ coal processes could add over a trillion tons of coal to the U. S. coal reserves. The economics of these processes is compared with surface gasification. Independent studies show this process to be 25% cheaper than surface gasification for Western coals. The major projects are briefly described. The Linked Vertical Well process is in the most advanced stage and shows great promise. The last test produced a low-Btu gas averaging 171 Btu per standard cubic foot for average production rates of 8.5 million standard cubic feet per day. The other projects are Packed Bed, Longwall Generator, and Steeply Dipping Beds. Unique factors of the process development are discussed which may lead to commercial processes in the near term. A development strategy is proposed by which this technology could be commercialized before 1983 with potentially lower gas prices and lower environmental impacts, relative to mining plus surface gasification.

Jan 1, 1979

By J. L. Taylor, P. Duwez

PARTIAL phase diagrams of titanium with iron, cobalt, and nickel have been established by previous investigators.1-3 These diagrams seem to be reliable, at least for concentrations of titanium ranging from 0 to about 50 at. pct. More recently, Long and his collaborators have presented a tentative titanium-nickel diagram covering the titanium-rich side.' These various studies indicate that in each system three intermediate phases exist and correspond to the compositions Tia, TiX, and TiX2 (or TiX3). The purpose of this paper is to review the available information on the crystal structure of these phases and to give the results of additional X-ray diffraction studies. Previous Work A summary of the work of Wallbaum and his collaborators"-' is presented in table I. The first intermediate phase on the titanium-rich side of the three systems, with iron, cobalt, and nickel, is of the Ti2X type and has a face-centered cubic structure. Although it is stated that the unit cell contains 96 atoms: no lattice parameters are given. The second phase is centered around the compositions TiX for the three systems. The crystal structure of this phase is mentioned in a short note" as being body-centered cubic (CsCl type), but no parameters are given. The analogy between the three systems, which is perfect as far as the two phases of the type Ti2X and TiX are concerned, disappears at the titanium-poor end of the diagrams. In the system titanium- iron, TiFe2 has an hexagonal (MgZn2 type) struc-ture with the parameters given in table I. The existence of TiFe3 has also been reported8 (table I) but was questioned by other investigators2 and is also refuted by the present study. In the system titanium-cobalt, a phase corre-sponding to the composition TiCo2 has been investi-gated by Wallbaum and Witte6 who claim that the structure is cubic (MgCu2 type) for alloys slightly deficient in cobalt and hexagonal (MgNi2 type) for alloys slightly deficient in titanium. The parameters of the two phases are given in table I. In the system titanium-nickel, the nickel-rich phase corresponds to the composition TiNi3 and has been described as hexagonal7 with the parameters given in table I. The present investigation was initiated for the purpose of filling in the gaps in the knowledge con-cerning the structure of the various phases sum-marized in table I. Since the titanium used by Wallbaum and his collaborators was only 95 pct pure,' it was found desirable to redetermine the lattice parameters of the alloys prepared with a

Jan 1, 1951

By F. O. Garrabrant

POWER is furnished to the Climax Molybdenum Co. by the Public Service Co. of Colorado over two 100,000-volt line to a bank of three 3333-kva. Transformers 100/13.8 kv. These transformers arc so designed that with the addition of forced cooling their capacity may be increased 33 1/3 per cent at 12,000-ft. altitude. Under present conditions, these transformers are operated at 140 per cent of their rating with forced air cooling. On the secondary side of this bank there is a 15-kv., 1200- amp. Westinghouse oil circuit breaker provided with automatic reclosing relays allowing three successive short circuits before lockout. From this breaker 13.8-kv. power is transmitted to a central switching station (Fig. I) where all circuits radiate to the different operations of the property. Each circuit is protected by a 23-kv., 600-amp. oil circuit breaker with by-pass and isolating disconnecting switches. MINE Power at 13.8 kv. enters the mine through a ventilation raise over a three-conductor, size 1-0 varnished cambric insulated, leaded, steel-wire armored cable, insulated from 17 kv. This power is received and distributed through one switching station and four underground substations, shown in Fig. 2. No. 370 substation (Fig. 3) contains three 250-kva, 13,800/440-volt, single-phase Pyranol transformers protected on the high-voltage side by a 600-amp. manually operated oil circuit breaker. This station serves 20 slusher-hoist motors, a 45-kw., three-phase, 220-volt electric furnace, a Massco hot miller for tempering and milling Timken detachable bits and a hoist with 175-hp. motor on the No. 3 development shaft. Also at this shaft are three pumps. One two-stage pump, 1200 gal, per min., 100-ft. head, 3600 r.p.m., driven by a 150-hp. motor, is at the bottom of the shaft. Two deep-well pumps, 500 gal. per min., 500-ft. head, are at the collar of the shaft. Under normal operation the one pumping 1200 gal. per min. is controlled by a float switch to take care of the water. If this pump fails, or if its capacity is insufficient, the first 500-gal. pump is automatically started, and if still more capacity is needed the second 500-gal. pump automatically starts. Time delay relays are provided on the deep-well pumps, so that if power fails the column will have time to drain before the pumps restart. On failure of any of these, an alarm is sounded in the train dispatcher's office, so that mechanics can be sent to ascertain the cause of failure and make repairs. The cable from No. 370 substation is run to the switching station, in which are four15-kv., 600-amp. direct-current solenoid-operated oil circuit breakers. The current for operating and tripping is furnished by a 125-volt storage battery. All breakers are operated from the switchboard in the compressor room. One circuit from this switching station goes to the

Jan 1, 1944

By J. Weng

The equations of heat conduction are numerically solved for two kinds of artificial freezing- mechanical freezing and liquid nitrogen freezing. A two dimensional finite difference model simulating the freezing field is developed. The procedure introduces a way to simulate the effect of latent heat released when water transforms from liquid to solid. The procedure also produces a way to calculate the harmonic mean of heat conductivity used when dealing with heterogeneous material. The theoretically derived temperature distributions in frozen soil are given and compared with measured data. An analysis made on the thermal design in shaft freezing. The average temperature of frozen soil is calculated by using numerical integration. The regularity of development of frozen soil radius is revealed and given in an appropriate mathematical model.

Jan 1, 1984

By Thos Egleston

The sands of Snake River, Idaho, have long been known to contain gold. They were worked by some of the first prospectors who came to Idaho, and on the banks still stand the ruins of camps abandoned for years. There are almost always prospectors searching for gold during the season of low water, and it is not an infrequent thing to find a miner of the old type actually panning the sand, or the prospect-hole which he has just left. There is more or less mystery about these miners and their methods of finding the spots where they work. They are always subjects of much speculation to the ordinary traveller. The rich discoveries are, for the best of reasons, concealed until the claims can be taken up. It is difficult to find a place where there are no prospects, but the " colors " are so very fine that they do not offer much inducement to enterprise. The California miner usually values a color at from 5 to 10 cents, often the latter; while on Snake River it would take 100 colors, or even more, to make that amount.

Jan 1, 1890

By A. D. McMaster, M. L. Gimpl, N. Fuschillo

Low-power, high-speed, radiation-resistant, monolithic thin-film integrated circuits require thin-film resistors of high sheet resistance which are compatible with the processing requirements for monolithic silicon devices. For this purpose the structure and electrical resistance as a function of temperature were investigated for Nichrome-silicon monoxide cermet films on passivated single-crystal silicon substrates. A suitable material was found to be a mixture of 50 vol pct Nichrome-50 vol pct silicon monoxide. This mixture, when evaporated onto 300°C substrates. showed a low temperature coefficient up to 400°C, at both 270 and 1100 ohms per square. Resistors deposited on room-temperature, 300°, and 500°C substrates were heat-treated at 600°C in air for short periods of H- seed, low-power, radiation-re sis tant, monolithic thin-film integrated circuits'-3 require thin-film resistors of high sheet resistance and low temperature coefficients of resistance which are compatible with the processing requirements for monolithic silicon active devices. The present investigation is directed towards the replacement of the Nichrome in the sandwich-type SO2-Nichrome-SiO resistors, currently used for DTL monolithic thin-film integrated circuits, with codeposited Nichrome-SiO cermet resistors. These Nichrome-SiO resistors are provided with an overcoat of SiO and are deposited onto thermally oxidized silicon wafers used in monolithic mi-crocircuit technology. The cermet resistors are shown to provide a lower temperature coefficient of time totaling up to 45 min. Electron nzicrogvaphs and diffraction patterns were taken of the as - deposited and heat-treated films. These results were then compared with electrical-resistance measurements for each condition. The room-temperature and 300°C substrate films showed a large decrease in resistance. The 500°C substrate film remained stable throughout the entire cycle. Electron-microscopy results show that the increased stability after heating to 600°C is largely due to crystallization of the films which begins in the vicinity of 400°C. The slight oxidation of the films when heated in air had a negligible effect on the resistance. The resistance of the film was a function of the substructure. resistance and a more versatile compatibility with silicon monolithic processing. Previous work3, on chromium-SiO coevaporated cermet resistors on glass and ceramic substrates without overcoats of SiO has been reported. For the present application, the thin films should possess the following ideal requirements: a) a temperature coefficient of resistance as near zero as possible up to 300°C; b) have a sheet resistance higher than 200 ohms per sq to conserve space on the chip; c) be easy to evaporate; d) be oxidiation- and radiation-resistant; e) show long-time stability at 100°C; } be stable in N2 atmospheres up to 600°C for short periods of time (5 to 45 min). Requirements a to e are well-known. The last requirement was optional and was due to a mask elimi-

Jan 1, 1967

By James A. Crookston, William D. Fitzpatrick

Committee C-8 of the American Society for Testing and Materials defines "Refractories" as "Material, usually nonmetallic, used to withstand high temperature," and it defines the term "Refractoriness" thus, "In refractories the capability of maintaining the desired degree of chemical and physical identity at high temperatures and in the environment and conditions of use." The ability to withstand high temperatures is critical to classifying a material as a "refractory." However, as the foregoing definition of "refractoriness" implies, the refractory material may be subjected to and is expected to resist not only high temperatures but a variety of other destructive forces incident to its use. These include abrasion, impact, thermal shock, chemical attack, and high level loads at high temperatures. The various industrial applications of refractories represent an infinite variety of combinations and degrees of severity of these destructive forces, including high temperatures. Naturally, such a variety of application conditions leads to a need for a wide variety of refractory products to satisfy those conditions. The number of refractory products available is great enough that some form of classification is necessary to a discussion of refractories. Refractories may be classified in several ways, but the most suitable one is based on their general compositions and to lesser degrees on their physical condition and distinctive properties. The primary types of brick include aluminosilicate brick (fire clay and alumina), basic brick (magnesia and chrome ore, alone and in various combinations), silica brick, insulating brick, and special refractories (carbon, Sic, ZrO,, zircon, borides, and nitrides). Brick are, of course, preformed and are usually heat treated at high temperatures before use, but are in some instances unburned and/or chemically bonded, including the relatively new class of tar-bonded magnesia and/or dolomite brick. In addition to preformed refractories, another broad category includes the so-called specialty refractories, which are usually made in the same types as itemized for brick-bonding mortars and high temperature cements, hydraulic setting castables or refractory concrete, plastic firebrick, and ramming mixes. Refractory grains, such as fire clay and high alumina calcines, dead-burned magnesite and periclase, and dead-burned dolomite are also considered refractory products. Brick are also classified on the basis of physical dimensions, as standard sizes and special shapes. The standard sizes are those which are of definite shape and design and are designated as 9 x 4 ½ x 2 ½ in. and 9 x 4 ½ x 3 in. straights and series. All other brick of non- standard sizes are referred to as special shapes. These come about as a result of a particular need for a given furnace or for a particular application.

Jan 1, 1975

By H. Kenworthy, M. M. Fine

The progress made to date in the mineral dressing of complex Arkansas titanium ores is reported in this paper. Concentrates of rutile, a dioxide of titanium, were produced by treating a submarginal ore from the Magnet Cove Rutile Co., Inc., Magnet, Ark. The rutile recovery at present is 45 to 50 pct of the total TiO2 with the possibility of increased recovery with additional research. The work reported herein is part of a general study which will later include results of investigation of other titanium ore bodies in the Magnet, Ark., area. The fragile character of the rutile minerals, the softness of the gangue, the occurrence of pyrite and leucoxene, and the considerable proportion of extremely small size rutile in the presence of montmorillonite- and illite- type clays in the Magnet Cove open-pit mine are the important factors in the mineral dressing of this submarginal rutile ore.

Jan 1, 1949

By N. A. Hasenack

A full description of tests and test results of potgrate--as well as industrial tests is given. It is concluded that the favorable effects of magnetite ores on the pelletizing-plant results can almost be obtained by replacing the magnetites by hematites with coke breeze. The amount of coke breeze to be added should be about 30% above the theoretical value which is derived from the transition heat of the magnetite. The total amount of coke breeze should be limited to 1.5%.

Jan 1, 1977

By J. E. Gould, H. J. Hand

Many independent studies are being made on slag-metal relationships in the open-hearth furnace, and these studies cannot help but result in an ultimate improvement in the quality of open-hearth steel of both the open and killed types. In maintaining quality control at the National Tube Company's plant, emphasis has been placed on an evaluation of the iron oxide content of the steel in as quantitative a manner as possible, in order that the most desirable level of oxidation might be obtained for a given type of steel, and to secure a more precise basis for final de-oxidation. In the past, various methods were used for estimating FeO content of the metal at tap to ensure uniform and thorough deoxidation of killed steel, avoiding overdeoxidation to minimize the amount of inclusions present and to make as sound a steel as possible. For the open-type steels, such control involves obtaining the necessary level of oxidation for the most suitable action of the steel in the molds to provide good surface quality and cross section for the specific grade involved. While rapid analytical methods are available for determination of FeO in the liquid metal, such methods are still not sufficiently rapid for routine control on the open-hearth floor, nor do such analyses provide information as to what causes high or low FeO values. The method of sampling can still be considered a problem in view of the variability encountered in taking simultaneous duplicate tests. With the accurate rapid methods now available for determining carbon in the metal, estimating slag basicity and obtaining temperatures of liquid metal, it was believed possible to determine the influence of the various furnace reactions in establishiug the state of oxidation at a given time. Simultaneous slag and metal tests were used in this analysis, aided by statistical methods, to determine the factors that affect the metal FeO, and also to make a quantitative evaluation of these factors. Data obtained are from actual iurnace operations, the metal test being of the I spoon, Herty type, and taken in duplicate. Metal temperatures were taken with the open-tube bath pyrometer developed by the Research Laboratory of the United States I Steel Corporation. This method of taking open-hearth metal temperature was invented by Collins and Oseland,l and was developed into its present form by L. 0. Sordahl,2 of the Research Laboratory. The instrument and its mode of operation have been fully described by Sordahl and Sosman in three publications.3,4,5 lag components were obtained by chemical analysis. Data were taken from four 165-net-ton furnaces during the working period of the heat. Recognizing that additions of ore affect the metal FeO. no tests were included within 30 min. after ore additions. In all, 65 tests (48 heats) were used in this study.

Jan 1, 1942

By J. E. Gould, H. J. Hand

Many independent studies are being made on slag-metal relationships in the open-hearth furnace, and these studies cannot help but result in an ultimate improvement in the quality of open-hearth steel of both the open and killed types. In maintaining quality control at the National Tube Company's plant, emphasis has been placed on an evaluation of the iron oxide content of the steel in as quantitative a manner as possible, in order that the most desirable level of oxidation might be obtained for a given type of steel, and to secure a more precise basis for final de-oxidation. In the past, various methods were used for estimating FeO content of the metal at tap to ensure uniform and thorough deoxidation of killed steel, avoiding overdeoxidation to minimize the amount of inclusions present and to make as sound a steel as possible. For the open-type steels, such control involves obtaining the necessary level of oxidation for the most suitable action of the steel in the molds to provide good surface quality and cross section for the specific grade involved. While rapid analytical methods are available for determination of FeO in the liquid metal, such methods are still not sufficiently rapid for routine control on the open-hearth floor, nor do such analyses provide information as to what causes high or low FeO values. The method of sampling can still be considered a problem in view of the variability encountered in taking simultaneous duplicate tests. With the accurate rapid methods now available for determining carbon in the metal, estimating slag basicity and obtaining temperatures of liquid metal, it was believed possible to determine the influence of the various furnace reactions in establishiug the state of oxidation at a given time. Simultaneous slag and metal tests were used in this analysis, aided by statistical methods, to determine the factors that affect the metal FeO, and also to make a quantitative evaluation of these factors. Data obtained are from actual iurnace operations, the metal test being of the I spoon, Herty type, and taken in duplicate. Metal temperatures were taken with the open-tube bath pyrometer developed by the Research Laboratory of the United States I Steel Corporation. This method of taking open-hearth metal temperature was invented by Collins and Oseland,l and was developed into its present form by L. 0. Sordahl,2 of the Research Laboratory. The instrument and its mode of operation have been fully described by Sordahl and Sosman in three publications.3,4,5 lag components were obtained by chemical analysis. Data were taken from four 165-net-ton furnaces during the working period of the heat. Recognizing that additions of ore affect the metal FeO. no tests were included within 30 min. after ore additions. In all, 65 tests (48 heats) were used in this study.

Jan 1, 1942

By William M. Brewer

History.—The history of gold-mining in Georgia and Alabama antedates the discovery of gold in California. A very large proportion of the gold used in the United States previous to 1849 was produced by these States. A great deal of this history is merely tradition, and no reliable statistics can be obtained ; yet a personal examination of the gold-fields of Georgia and Alabama indicates that tradition is as fairly reliable, with regard to the history of these gold-regions, as it is in any similar cases throughout the world. In Georgia, the history of gold-mining dates back to 1829, when the first gold-mining excitement in the United States occurred. In Alabama, the discovery of gold was made some years later through the work of prospectors, incited by the rich finds in the Georgia mining camps. The greatest product of gold in these States was between the years 1840 and 1849. In Lumpkin county, Ga., and Cleburne county, Ala., the districts from which the most of this gold was taken, the tailing-dumps are silent witnesses of the extensive operations which were carried on by the primitive and crude methods then known. It is no rare thing to see trees 12 to 15 inches in diameter, and even

Jan 1, 1896

By P. Duwez, C. B. Jordan

A. J. SHALER*—I should like to congratulate the authors for having carried out such a precise set of experiments. It has been found useful, in sintering experimental compacts in vacuo, to make certain that the residual gas is not one which reacts with the metal. Since traces of oxygen can be kept away only with great difficulty, the technique is often adopted of using a "getter " of powder in the vicinity of the compacts, and, in addition, of permitting a small hydrogen leak to flow into the vacuum chamber. Did the authors use similar devices? This paper brings up a question concerning the definition of the word ' sintering.' The authors restrict its use to the adhesion between particles. Kuczynski, in a paper presented at this meeting, applies the word to the growth of areas of contact between particles. I have used it to mean both these phenomena and also the dimensional changes which continue to take place after the first two have run their course. May I suggest that we should come to an agreement on the use of these words ? Fig 1 and 2 show an interesting feature: extrapolation of the curves to zero time does not give a densification parameter of zero. The higher the temperature, the higher is the intercept on that axis. These observations agree with the concept of a practically instantaneous densification taking place while the compact is being brought to heat. Such a change may be brought about by plastic deformation and primary creep. The stress pattern causing this first rapid flow is, to my mind, due to the force of attraction between the surfaces of opposite particles in the regions immediately flanking their common areas of contact. The stress is not temperature-sensitive, but at room temperature plastic deformation only proceeds until the metal in the area of contact can support it elastically. As the metal is heated, the elastic limit falls, and further plastic flow occurs. At the higher temperatures, this is followed by primary creep, and finally by the steady-state rate-reaction which the authors are seeking. If they were to recalculate their densification-parameter values, using, not the initial density of the cold compact, but the density after the compacts have been brought to temperature, the systematic deviations from linearity in Fig 3 and 4 might be eliminated. Such initial densities might be obtained by extrapolating the curves of Fig 1 and 2 to zero time. I am naturally pleased to see that such a very well done series of experiments leads to a heat of activation (for the densification process in hydrogen) that is much higher than that for self-diffusion, in confirmation of the less elaborate results reported by Wulff and myself (Ind. and Eng. Chem., (1948) 40, 838). J. T. KEMP*—I would like to comment on Dr. Shaler's remarks. There are apparently different interpretations of the word "sintering." It seems to me that an accurate definition of our word is essential in all metallurgy. May I point out, in this connection, that in practical metallurgy the word "sintering" has been applied to a bonding process in the preparation of ores and flue dust for fur-nacing. It would be unfortunate if in the area of powdered metallurgy we should establish a definition that is essentially different in meaning. F. N. RHINES*—I think that I can answer the question by saying that I see no essential difference between the use of the term "sintering" in extractive metallurgy and in powder metallurgy; physically the same things are going on. I admit sintering is used for different end purposes in the two cases. When we resort to the sintering of lead ore mixture we are doing so to obtain a chemically reactive, loose texture of some rigidity. This is only a difference in use. After all, in powder metallurgy we sometimes deliberately produce a very porous material which has just a little strength, just as in the case of sinter cake. P. DUWEZ (authors' reply)—We agree that it would be helpful to have well-established definitions of such terms as "sintering." Since the question has now been raised, the time might be appropriate for its consideration by some suitable committee of one or more of the metallurgical societies. In answer to Dr. Shaler's first question, no getter nor hydrogen leak was used in our vacuum experiments, except insofar as the guard disks (used to reduce friction between specimens and trays) may have acted as getters. Dr. Shaler's statement that extrapolation of the curves of Fig 1 and 2 does not lead to zero densification at zero time apparently overlooks the logarithmic

Jan 1, 1950

THE fifth annual convention of coal-operating men, with the usual exposition of coal-mine equipment, was held at Cincinnati, May 7 to 11 inclusive, and was fully up to the high standard set by previous years. This spring meeting has come to be one of the most helpful services to industry performed by the Ameri-can Mining Congress and a center at which operators and engineers easily and quickly get into touch with the newest and best things in practice and equipment. Over 200 exhibitors showed this year and very little if anything that is new `failed to be shown. The ex-hibits were well arranged and adequate rather than elaborate. They attracted the careful attention of the members and guests of the Congress, admission being by badge rather than by ticket sold to, the general public. Eight sessions were held for reading and dis-cussion of technical papers, one for Management and

Jan 6, 1928

By R. L. Fleischer, W. F. Hosford

Tensile data for coarse grained aluminum Polycrystals suggest that the "grain size" effect is not due to dislocations piled up at grain boundaries but rather is primarily a relative size effect due to surface crystals being weaker and less confined. STUDIES directed at interpreting hardening of poly-crystalline metals normally identify their strain hardening properties with those in some particular type of single crystal.1"4 The recent recognition in face centered-cubic metals of a nearly linear stage with rapid hardening occuring at comparable rates for both polycrystals and single crystals, suggested that the same process or processes determine both cases and hence that there exists some justification for the use of single crystals to understand polycrystals. Further evidence for the above view may be found by an approach initiated by Chalmers:5 By using bicrystals of controlled orientation it is possible to begin to assemble a polycrystal and also to study grain boundary effects in detail. In this way it has been found that a single grain boundary affects easy glide but not the subsequent stage II hardening.6 This result suggests that a sensitive way to observe grain boundary effects in polycrystals would be to vary grain size and measure easy glide. As will be seen, easy glide is only possible for coarse-grained samples, and hence the results will serve to fill in the gap in measurements between single crystals and bicrystals on one hand and fine-grained polycrystals on the other. One problem inherent in comparing single crystals with polycrystals is the uncertainty as to what slip systems are acting in a polycrystal. To compare the two types of samples, rates of shear hardeninn---L. on the acting -planes are needed. and these may be computed only if it is known what particular systems are active. The acting systems were examined for a coarse-grained polycrystal and it will be shown that the systems supplying the preponderance of slip can be determined with little ambiguity. EXPERIMENTAL PROCEDURE Twelve samples of aluminum were prepared by chill casting into a heated graphite mold, followed by annealing at 635° ± 5°C for 24 hr with an 8-hr fur- nace cool, and finally either etching7 or electropol-ishing.' The samples, with a 7 to 10 cm length between grips and 4.4 by 6.6 mm in cross section, were deformed at a strain rate of about 3 10 -3 . per min in a tensile device which has been described elsewhere.5 The composition was reported by Alcoa as 99.992 pct Al, 0.004 pct Zn, 0.002 pct Cu, 0.001 pct Fe, and 0.001 pct Si; nine samples were deformed while immersed in liquid helium and three in air at room temperature. The stress-strain curve for one of the samples (P-1) deformed at 4.2 "K has been reported previ~usl~.~ This sample was selected for determination of active slip systems. Eighteen of the crystals were examined by optical microscopy to determine the angles of slip line traces and by X-ray back reflection to determine orientation. By this means the slip planes were determined and the resolved shear stress factors for possible slip systems could be computed. Finally each sample was sectioned so that after etching, the number of crystals could be counted for each of ten newly exposed surfaces. The average of these ten values will be termed n, the number of crystals per cross section. Values of 11, varied from 1.9 (nearly bamboo structure) to 12.7. Sketches of typical cross sections appear in Fig. 1. RESULTS AND DISCUSSION: SLIP SYSTEMS 1) Determination of Acting Slip Planes—The stress axis orientation and operative slip planes in eighteen crystals of sample P-1, as determined by slip line traces and crystal orientation, are summarized in Fig. 2. For one of the crystals two planes had a common trace. so that the traces alone did not distinguish which plane or planes were slipping. However it was found that the stress resolving factor for the primary system was 0.386, .while that for the most stressed system in the other plane (indicated bv the dotted arrow) is 0.138. It will be assumed tgerefore that only the primary plane acted. Since the orientations were determined after extending the samples 4 pct, the stress axes may be rotated from their original value by as much as 2 deg in some cases. It is interesting to note that in five crystals only one slip plane acted, in eight two acted, and in five three planes were observed—an average of two slip

Jan 1, 1962