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By William F. Harris, Joseph Easha

FOR many years basic control of refinery operations depended on visual observation of small chill specimens poured at various intervals during processing. The oseto of these samples was related to the physical and chemical properties of the metal. Since the =setn is dependent on many factors other than oxygen content, this method, while giving a general indication of the condition of the copper, does not accurately measure the oxygen content. For the last 3 years a modified vacuum fusion procedure which enables the operator to determine the oxygen content of the copper within 1 5 min of sampling has been in use at the Westinghouse Copper Mill. For use with this apparatus a sampling technique has been developed which gives oxygen values representative of the oxygen content of the wire bar. The sampling technique is based on a statistical study, which compared the oxygen content of the laboratory sample of copper poured at the same time a wire bar was being poured, with the oxygen content of the wire bar. The apparatus used for the determination of oxygen in copper is shown in Fig. 1 and is essentially the same as previously described but with one important modification. A very porous fritted glass disc has been inserted in the tubing between the manom- eter and 40/50 ground glass joint. The fritted disc retains the copper vapor and copper particles in the furnace section and prevents contamination of the mercury in the manometer. Without the disc the manometer became difficult to read after a few weeks of operation. In earlier work1 it had been established that the simplified vacuum fusion apparatus used at the Copper Mill gave essentially the same results as a con-vential vacuum fusion apparatus. However, for this study it was necessary to determine the difference, if any, between the oxygen content of the wire bar and the oxygen content of the small chill sample used for the oxygen analysis. This correlation was established by taking a chill sample at the same time wire bars were being poured. The wire bar being poured at the time the chill sample was taken was marked and removed for further analysis. The copper is sampled at various times during refining and cast into laboratory size samples with the mold shown in Fig. 2. The mold is made of cold rolled steel and is 2 in. high and 2 1/2 in. in diam. The large upper portion of the cast sample is used for measurement of the conductivity of the copper, The lower portion which is a rod about 1/4 in. diam by 3/4 in. long is used for determination of the oxygen content. This portion of the sample weighs about 5 g which is approximately the size sample used for the analysis. The only preparation neces-

Jan 1, 1962

By AIME AIME

WHETHER by the Mohawk Trail, Sound steamer, air plane, railroad or any other route or mode of locomotion, all roads will lead to Boston the week of National Metal Congress, Sept. 21-25. The Institute of Metals and Iron and Steel divisions of the Institute are then to meet jointly at the Hotel Statler, and the American Society for Steel Treating, the American Welding Society, the Society of Automotive Engineers and the Iron and Steel Division of the American Society of Mechanical Engineers present carefully planned programs at their respective sessions. The National Metal Exposition will be held on Commonwealth Pier.

Jan 1, 1931

By Klaus Schwerdtfeger

Activities of lead in Pt-Pb and Pd-Pb melts in the temperature range of 800° to 1200°C have been detev-mined from electromotive-. force measurements 202th the cells Both systems display strong negative deviations from Raoult's law. The data obtained with cell [1] were combined with available data on the activity of PbO in silica-satuvaterl PbO-SbO2 melts to calculate the standard free cnergy of formation 01- liquid PbO. FREE energies of formation of oxides and activities of components in metal and oxide melts can be determined with galvanic cells consisting of a metal phase, an electrolyte containing the oxide of one of the components of the metal phase, and an oxygen electrode. This technique has been used previously to measure the standard free energy of formation of solid sio2, 1 and activities in Fe-si, CO-si,2 Ni-Si,2 and CaO-P2O5 3 melts. The present paper reports activities in Pt-Pb and Pd-Pb melts as measured with the same experimental technique. EXPERIMENTAL METHOD General Considerations. The following cells were used: Pbl (PbO-SiO2)liquid, SiO2 Pt-Pb 1 (PbO-SiOz)liquid, SiO2solidO2 [2] Pd-Pb (PbO-SiOz)liquid, SiO2solid O2 [3] Liquid alloy and' oxide melt were contained together in a silica glass crucible of essentially the same design as described previously.1'2 The PbO-SiO2 melts are ionic conductors.' During the experiment, the silica glass crystalizes in a layer adjacent to the electrolyte. The electrolyte equilibrates with solid silica and hence attains the composition of the Si02-liquidus curve in the system PbO-SiO2 at any particular temperature. Molybdenum wires were used to establish contact with the liquid metal. The oxygen electrode, which reaches the surface of the PbO-SiO, electrolyte from above, consists of a platinum wire inserted into a ceramic tube and provided with a 2-mm-diam platinum bead at its end. Gas of known oxygen partial pressure (pure oxygen of 1 atm: air, or N2 with 1.04 pct 0,) is blown through the ceramic tube onto the surface of the electrolyte. The cell reaction is Pb (metal) + 1/2O2 (gas) = PbO (electrolyte) [4] No oxidation of platinum or palladium ("displacement reaction") occurs. This is to be expected from the noble character of platinum and palladium, but was also shown experimentally, as described in the next section. The galvanic electromotive force of the cell is given by where AG is the change in free energy for Reaction [4], E(=2) is the number of electrical equivalents necessary to form 1 mole of PbO, and F is the Faraday constant. Formula [5] is valid only if no junction potential exists within the electrolyte. Junction potentials occur only when the compositions of the electrolyte are markedly different at the electrodes. Such differences are negligible in the PbO-SiO, electrolyte, as shown in the next section. Since molybdenum contact leads are used, appropriate corrections were made on the measured electromotive forces to account for the thermoelectric effect of the Mo-Pt couple. The thermoelec-tromotive forces were measured separately with a Mo-Pt couple, and were found to vary linearly from 19 mv at 740°C to 40 mv at 1310°C with molybdenum being positive and platinum negative (cold junction at 25°C). Extrapolation of these values to higher temperatures yields values which are in satisfactory agreement with those obtained previously in the temperature range 1440° to 1630°c.1,2 The change in free energy for Reaction [4] is expressed as where chemical potentials of the species. The value of constant for a given temperature because the slag composition is fixed. Inserting [6] into [5] and using appropriate expressions for upb and uO2 the relation

Jan 1, 1967

By AIME AIME

The 102d meeting of the Institute was held at the Institute headquarters in the Engineering Societies Building, New York, N. Y., on Feb. 19, 20 and 21, 1912. A Bureau of Information, in charge. of Mr. George Buckman, was maintained during the meeting. The proceedings opened with an informal social meeting on Monday evening, Feb. 19, in Assembly-Room No. 1, on the

Mar 1, 1912

(The following list contains the names of those members of the Institute of whose connection with military service we have only recently become acquainted; it also includes the names of a few who have recently been promoted or transferred, indicated by a *. A complete list was published in the Year Book, issued as a supplement of the Bulletin for March, 1918.) ALLEN, Roy H., Capt., Air Service, Bureau of Aircraft Production, Washington, D. C. *AMIDON, CLAUDE E., Chemical Warfare Section', Astoria, L. I. *ARCHBALD, HUGH, 311th Infantry, 78th Division, American E. F. ASKIN, THOMAS B. H., Radio Station, Cavite, P. I. *AYER, FRANK A., Lieut., Commanding Officer, -270th Aero Squadron, American E. F. BARBA, W. P., Lieut. Colonel, Ordnance, U. S. A., Washington, D. C. *BARRETT, LESLIE P., 1st Lieut., 5th Field Artillery, American E. F. BLICKENSDERFER, F. C., 1st Lieut., N. A., Ordnance Dept., Edgewood Arsenal, Edgewood, Md. *BROOKS, FLOYD R.., Lieut., Canadian Engineers, Seaford, England. BROWN, GEORGE M., Co. G, 1st Replacement Regiment, Washington Barracks, D. C. *BRUNEL, LOUIS J., Lieut., 5th Field Artillery, Brigade Headquarters, American E. F. *BRUNTON, D. W., Cons. Engr., Naval Consulting Board, Washington, D. C.

Jan 11, 1918

By T. P. Floridis, J. H. Young

The need for close control of the phosphorus content of steels has led to numerous investigations on the equilibria of the dephosphorization reactions. Winkler and chipman1 have established the general conditions for effective dephosphorization of steel. They are high slag basicity, high oxygen potential, and low temperature. Other investigators have made additional contributions to the understanding of the dephosphorization process. The current status of the understanding of the dephosphorization of steel is concisely presented by Bodsworth2 and by Ward. The investigation reported in this communication was undertaken with the purpose of establishing the effect of additions of barium oxide and calcium fluoride on the dephosphorizing capacity of slags. Esin and Gel'd4 proposed that barium oxide, being more basic than calcium oxide, should cause an increase in dephosphorizing capacity when added to steelmaking slags, or when used as a substitute for calcium oxide. Derge5 has also proposed that in the future conventional slags might be replaced by BaO-Al2O3 slags. There is, however, no experimental evidence confirming the effect of barium oxide on the dephosphorizing capacity of slags. The effect of calcium fluoride on the dephosphorization of steel is not clearly understood. It is generally recognized that additions of calcium fluoride are beneficial. It is not clear, however, whether calcium fluoride affects the equilibrium of the dephosphorization reaction, or whether it simply causes an increase in the fluidity of the slag and, consequently, faster approach to equilibrium. The experimental procedure consisted in equilibrating synthetic molten slags with liquid copper at 1550°C under a gas stream containing argon, hydrogen, and water vapor. In all experiments the argon to hydrogen ratio was approximately 4:1, and the hydrogen to water ratio was 5.42:l. Molybdenum crucibles were used as containers for the slag and metal. Under the above-described conditions of temperature and composition of atmosphere, there was no observable attack of the crucibles by the metal, slag, or atmosphere. Copper was used instead of iron, because iron attacks molybdenum. The equilibration was made in a tubular furnace consisting of a recrystallized alumina tube. The alumina tube was heated by electrical resistance. A Pt-40 pct Rh wire winding was used for most runs. A silicon carbide tubular resistor was also used for some runs. Temperatures were measured with a Pt-Pt-Rh (10 pct Rh) thermocouple and kept constant within ±5°C. Equilibrium was approached from both sides, i.e., by adding the phosphorus either as oxide in the slag or as a phosphorus-rich alloy of phosphorus and copper. The holding time at the equilibrium temperature was 6 hr. At the end of each run the crucibles were rapidly cooled and removed from the furnace. The slag and metal were separated and analyzed. The experimental results are shown in Table I. The phosphorus content of the slag is expressed both as percent phosphorus pentoxide and as percent phosphorus. The basicity ratio is computed by dividing the number of moles of basic oxides-oxides of barium, calcium, magnesium, and sodium—by the number of moles of acidic oxides- oxides of aluminum, phosphorus, and silicon. Calcium fluoride is not included in the computation of the basicity ratio; i.e., calcium fluoride is assumed to be neither basic nor acidic. The distribution ratio of phosphorus—percentage of phosphorus in the slag divided by the percentage of phosphorus in the metal- is plotted in Fig. 1 against the basicity ratio. The results indicate that slags containing barium oxide have greater dephosphorizing capacity than slags containing calcium oxide. The high dephosphorizing capacity of slags containing sodium oxide and the low dephosphorizing capacity of magnesia-containing slags which already have been reported in the literature2 are confirmed by the results of this investigation. It appears that calcium fluoride has a beneficial effect on the distribution of phosphorus between slag and metal in acid slags only. Although the obtained distribution ratios between the phosphorus contents of slag and copper are not directly applicable to the dephosphorization of steel, they are sufficient for evaluating the effect of slag additions on the dephosphorizing capacity of slags in general. An increase in the ratio of distribution of phosphorus between slag and metal indicates lowering

Jan 1, 1968

Jan 1, 1881

By N. C. Fick, R. L. Rickett

DESPITE the large volume of literature on alloys of iron and silicon,1 there is little published information dealing specifically with the constitution, at various temperatures, of the alloys containing less than 0.10 per cent carbon and from 0.5 to 4.5 per cent silicon that are used extensively in the electrical industry. Because such information was needed by those engaged in the production of these alloys in, sheet and strip form, the constitution was determined of a series of commercial silicon steels containing 0.05 to o.08 per cent carbon and 0.20 to 4.31 per cent silicon, over the temperature range 1300° to 2500°F. These alloys were all from regular production heats and of commercial quality. The results of, the tests are given in Fig. I and for comparison the constitution diagram of iron-silicon alloys with 0.01 to 0.02 per cent carbon, taken from the literature, is also presented. MATERIAL AND PROCEDURE All steels were hot-rolled to a thickness of 0.060 to 0.080 in. and used in this condition. Their chemical compositions, including over-all check analysis, and "center" analysis for carbon and silicon, are given in Table I. The so-called center analysis was determined on samples pickled to remove the outer surface and leave only the center third of the gauge thickness-the portion of the sample on which metallographic ratings were based. In most, but not all, of the alloys, slightly higher carbon was found at the center than when the whole strip was sampled; the two methods of sampling show relatively little difference in silicon. Two of the steels, A and E, contain relatively high phosphorus, while I and K are somewhat higher in manganese than the others. [ ] The procedure consisted essentially of heating specimens (about 1/16 by 3/8 by 3/4 in.), protected from oxidation or change in carbon content, at a temperature in the desired. range and for a selected period, after which they were quenched in iced brine; the degree of transformation that had then occurred was determined by metallographic examination. The soaking periods were selected after preliminary investigation had shown that a con-

Jan 1, 1946

By R. L. Rickett, N. C. Fick

Despite the large volume of literature on alloys of iron and silicon,' there is little published information dealing specifically with the constitution, at various temperatures, of the alloys containing less than 0.10 per cent carl~on and from 0.5 to 4.5 per cent silicon that are used extensively in the electrical industry. Because such information was needed by those engaged in the production of these alloys in sheet and strip form, the constitution nas determined of a series of commercial silicon steels containing 0.05 to 0.08 per cent carbon and 0.20 to 4.1 per cent silicon, over the temperature range 1300° to 1500°F. These alloys were all from regular production heats and of commercial quality. The results of the tests are given in Fig. I and for comparison the constitution diagram of iron-silicon alloys with 0.01 to 0.02 per cent carbon, taken from the literature, is also presented Material and Procedure All steels were hot-rolled to a thickness of 0.060 to 0.080 in. and used in this condition. Their chemical compositions, including over-all check analysis, and "center" analysis for carbon and silicon, are given in Table I. The so-called center analysis was determined on samples pickled to remove the outer surface and leave only the center third of the gauge thickness—the portion of the sample on which metallographic ratings were based. In most, but not all, of the alloys, slightly higher carbon was found at the center than when the whole strip was sampled; the two methods of sampling show relatively little difference in silicon. Two of the steels, A and E, contain relatively high phosphorus, while I and K are somewhat higher in manganese than the others. The procedure consisted essentially of heating specimens (about 1/16 by 3/8 by 3/4 in.), protected from oxidation or change in carbon content, at a temperature in the desired range and for a selected period, after which they were quenched in iced brine; the degree of transformation that had then occurred was determined by metallographic examination. The soaking periods were selected after preliminary investigation had shown that a con-

Jan 1, 1947

By N. C. Fick, R. L. Rickett

Despite the large volume of literature on alloys of iron and silicon,' there is little published information dealing specifically with the constitution, at various temperatures, of the alloys containing less than 0.10 per cent carl~on and from 0.5 to 4.5 per cent silicon that are used extensively in the electrical industry. Because such information was needed by those engaged in the production of these alloys in sheet and strip form, the constitution nas determined of a series of commercial silicon steels containing 0.05 to 0.08 per cent carbon and 0.20 to 4.1 per cent silicon, over the temperature range 1300° to 1500°F. These alloys were all from regular production heats and of commercial quality. The results of the tests are given in Fig. I and for comparison the constitution diagram of iron-silicon alloys with 0.01 to 0.02 per cent carbon, taken from the literature, is also presented Material and Procedure All steels were hot-rolled to a thickness of 0.060 to 0.080 in. and used in this condition. Their chemical compositions, including over-all check analysis, and "center" analysis for carbon and silicon, are given in Table I. The so-called center analysis was determined on samples pickled to remove the outer surface and leave only the center third of the gauge thickness—the portion of the sample on which metallographic ratings were based. In most, but not all, of the alloys, slightly higher carbon was found at the center than when the whole strip was sampled; the two methods of sampling show relatively little difference in silicon. Two of the steels, A and E, contain relatively high phosphorus, while I and K are somewhat higher in manganese than the others. The procedure consisted essentially of heating specimens (about 1/16 by 3/8 by 3/4 in.), protected from oxidation or change in carbon content, at a temperature in the desired range and for a selected period, after which they were quenched in iced brine; the degree of transformation that had then occurred was determined by metallographic examination. The soaking periods were selected after preliminary investigation had shown that a con-

Jan 1, 1947

By AIME AIME

FREDERICK WORTHEN BRADLEY, the newly elected president of the Institute, may be said to be the prototype of the men who have built up the great mining industry of the West. He was born in Nevada County, Cal., on Feb. 21, 1863, and studied mining at the University of California from 1882 to 1884, as a member of the Class of 1885. He was in contact with the mining industry from his earliest years and in his reminiscences which we published last month, he told of meeting Thomas Mein and H. C. Perkins in 1877. Beginning as assayer and roustabout at the Eagle Bird mine, in Nevada county, Mr. Bradley was a deputy mineral surveyor in 1886 and 1887 and superintendent of the Spanish mine from 1885 to 1890. There he made a record of mining gold ore at 65 cents per ton that was not only astounding in that day when modern large scale mining had not yet been developed but is still a mark to shoot at. As a result he was called in 1890 to be assistant manager of the Bunker Hill and Sullivan and was made manager in 1893. In 1897, he was elected to the presidency of the company, a position he still holds. H. C. Perkins and D. O. Mills, the largest stockholders in the Bunker Hill and Sullivan Co. took over the Tacoma smelter in 1898, feeding it with concentrate from the Coeur d'Alene and Douglas Island mines but also doing a gen-era1 smelting business. Mr. Bradley was put in as president of the Smelting company, and held that position until the plant was sold to the American Smelting Securities Co. in 1905.

Jan 1, 1929

By D. J. McAdam, G. W. Geil, R. W. Mebs

AS shown in previous papers by the authors 9-l7† the resistance of a metal to fracture, like its resistance to plastic deformation, is a function of all three principal stresses.‡ A technical cohesion limit is the technically determined resistance to fracture under a specific stress system. The technical cohesive strength thus comprises an infinite number of technical cohesion limits corresponding to the infinite number of possible combinations of the principal stresses. The technical cohesive strength, therefore, may be represented by a surface in a diagram with the three principal stresses as coordinates. As shown in previous papers, 9-I8 the technical cohesive strength increases with plastic deformation, with decrease in temperature, and with increase in the strain rate. The technical cohesion limit, therefore, is affected by the same factors that affect the flow stress, § namely, the stress system, plastic deformation, temperature, and the strain rate. More- over, the influence of each of these factors on the technical cohesion limit has been shown to be qualitatively similar to the influence of the same factor on the flow stress.9-18 Advance of knowledge about the conditions determining fracture, of metals has been retarded by the reluctance of some investigators to abandon preconceived ideas about how metals "should" behave. The incorrect idea is still prevalent that the conditions determining resistance to fracture are very different from those determining the flow stress. Attempts are still being made to express resistance to fracture in terms of a single parameter, such as a limiting value of the greatest principal stress, the maximum shearing stress, or the volume stress (one-third the algebraic sum of the three principal stresses). In these attempts, a sharp distinction is sometimes made between a ductile or "plastic fracture " and a "brittle fracture." In making this distinction, however, the meaning attached to the term "brittle fracture" sometimes is not made clear. The term could mean fracture after very little plastic deformation or it could be used to designate the type of fracture. An ordinary fracture of a ductile metal at room temperature starts as a cleavage, generally transverse to the direction of the greatest principal stress, but eventually changes to a shearing fracture. In some conditions, however, the metal fractures entirely by cleavage, with no evidence of plastic deformation during the fracture; the surface of such a fracture may have a

Jan 1, 1947

By F. N. Rhines

Sintering may be defined as the process by which powders bond themselves into coherent bodies, usually, although not necessarily, under the influence of pressure and elevated temperature. For the sake of clarity and simplicity, the present survey will exclude from consideration the sintering of mixed or alloyed powders, with attendant complications, but at the risk of overlooking information of general applicability. Sintering in the presence of a liquid phase is thus automatically eliminated. The sintering of alloys involves much additional subject matter and deserves separate consideration. Since the literature of the subject is extensive and widely scattered, it will not be feasible to consider the contributions individually. Instead, the subject matter will be classified according to experimental observations and theory, and will be presented in summary form. It should be noted that the appended list of references does not constitute a complete bibliography; it includes only those works quoted below. More extensive bibliographies are included in several of the references; see particularly references 7, 9, 28, 34, 38, 50, 52, 54, a "Bibliography on Powder Metallurgy" published by the Library of Congress and a pamphlet published by the Metals Disintegrating Co. entitled "The Field of Powder Metallurgy and Bibliography." 11. Summary of Experimental Observations The following classified list is composed of general statements of established fact derived from the experimental results reported in the published literature. A few contested observations are included, because of their potential importance; these are labeled as such. Any satisfactory and complete theory must be capable of explaining all of the uncontested facts. Obviously, some important facts may be missing from this list and these may hold the key to the correct explanation of the sintering process, but the possible lack of such material should not deter attempts to understand the subject on the basis of what is available here. A, The Initial Bond at Room Temperature a. To a limited extent uncompressed powders and massive metals adhere at room temperature. Clean tin powder forms a weak "cake" on standing at room temperature, the strength increasing with time. Clean gold surfaces adhere on light con-tact, as do those of many other substances, including nickel.27 b. Upon compression the strength of the bond- is increased progres-ivelv. There is a limit of pressure

Jan 1, 1946

By F. N. Rhines

Sintering may be defined as the process by which powders bond themselves into coherent bodies, usually, although not necessarily, under the influence of pressure and elevated temperature. For the sake of clarity and simplicity, the present survey will exclude from consideration the sintering of mixed or alloyed powders, with attendant complications, but at the risk of overlooking information of general applicability. Sintering in the presence of a liquid phase is thus automatically eliminated. The sintering of alloys involves much additional subject matter and deserves separate consideration. Since the literature of the subject is extensive and widely scattered, it will not be feasible to consider the contributions individually. Instead, the subject matter will be classified according to experimental observations and theory, and will be presented in summary form. It should be noted that the appended list of references does not constitute a complete bibliography; it includes only those works quoted below. More extensive bibliographies are included in several of the references; see particularly references 7, 9, 28, 34, 38, 50, 52, 54, a "Bibliography on Powder Metallurgy" published by the Library of Congress and a pamphlet published by the Metals Disintegrating Co. entitled "The Field of Powder Metallurgy and Bibliography." 11. Summary of Experimental Observations The following classified list is composed of general statements of established fact derived from the experimental results reported in the published literature. A few contested observations are included, because of their potential importance; these are labeled as such. Any satisfactory and complete theory must be capable of explaining all of the uncontested facts. Obviously, some important facts may be missing from this list and these may hold the key to the correct explanation of the sintering process, but the possible lack of such material should not deter attempts to understand the subject on the basis of what is available here. A, The Initial Bond at Room Temperature a. To a limited extent uncompressed powders and massive metals adhere at room temperature. Clean tin powder forms a weak "cake" on standing at room temperature, the strength increasing with time. Clean gold surfaces adhere on light con-tact, as do those of many other substances, including nickel.27 b. Upon compression the strength of the bond- is increased progres-ivelv. There is a limit of pressure

Jan 1, 1946

By Jay Carpenter

THIS paper deals with only one step in the treatment of ore at the West End mill; not because the other steps are repetitions of practice in other mills, but because in this particular step there is in use the Trent agitator. This device, although it has apparently failed in many mills, is here giving excellent service and has proved to be well adapted for making a thorough replacement of pregnant solution with a minimum amount of barren solution. The strong and weak points of this agitator, its present simple construction, and its use as a thickener for agitator or battery pulp are features of interest; but perhaps the point of greatest interest to the metallurgist in this day of continuous decantation is its use in a series of tanks for slime treatment by the replacement method. The agitating department of the West End mill consists of six redwood tanks, 24 ft. in diameter, 18 ft. high, each equipped with aTrent agitator, a centrifugal pump, and a motor. The pulp is transferred by a pump from the top of a flat-bottomed tank to a set of arms and nozzles in the bottom of the tank, at just sufficient pressure to cause the arms to revolve. The streams from the many nozzles keep the bottom of the tank clean, and these streams, coupled with the effect of the revolving mechanism and the ascending current, keep the pulp in constant motion and of constant gravity. .These agitating tanks hold 90 tons of dry slime and 202 tons of solution with a 1.24 pulp, our ore having a specific gravity of 2.7. This capacity is about 10 per cent. in excess of the standard 15 by 45 ft. Pachuca tank. The tanks are connected in one series for continuous agitation, the pulp for each agitator being drawn by its pump through a branch suction from near the top of the preceding tank and. delivered to the bottom of the tank by the agitator arms along with the regular pulp of that agitator. This method works automatically, since the flow through the branch suction varies directly with the difference in head of the two tanks. The chance for new pulp to pass out quickly is, therefore, much less than in many other systems of continuous agitation, since the new

Jan 8, 1915

By Jay A. Carpenter

This paper deals with only one step in the treatment of ore at the West End mill; not because the other steps are repetitions of practice in other mills, but because in this particular step there is in use the Trent agitator: This device, although it has apparently failed in many mills, is here giving excellent service and has proved to be well adapted for making a thorough replacement of pregnant solution with a minimum amount of barren solution. The strong and weak points of this agitator, its present simple construction, and its use as a thickener for agitator or battery pulp are features of interest; but perhaps the point of greatest interest to the metallurgist in this day of continuous decantation is its use in a series of tanks for slime treatment by the replacement method. The agitating department of the West End mill consists of six redwood tanks, 24 ft. in diameter, 18 ft. high, each equipped with a Trent agitator, a centrifugal pump, and a motor. The pulp is transferred by a pump from the top of a flat-bottomed tank to a set of arms and nozzles in the bottom of the tank, at just sufficient pressure to cause the arms to revolve. The streams from the many nozzles keep the bottom of the tank clean, and these streams, coupled with the effect of the revolving mechanism and the ascending current, keep the pulp in constant motion and of constant gravity. These agitating tanks hold 90 tons of dry slime and 202 tons of solution with a 1.24 pulp, our ore having a specific gravity of 2.7. This capacity is about 10 per cent. in excess of the standard 15 by 45 ft. Pachuca tank. The tanks are connected in one series for continuous agitation, the pulp for each agitator being drawn by its pump through a branch suction from near the top of the preceding tank and delivered to the bottom of the tank by the agitator arms along with the regular pulp of that agitator. This method works automatically, since the flow through the branch suction varies directly with the difference in head of the two tanks. The chance for new pulp to pass out quickly is, therefore, much less than in many other systems of continuous agitation, since the new

Jan 1, 1916

By F. N. Rhines

I. An Outline of the Theory of the Sintering of Pure Metal Powders SINTERING may be defined as the process by which powders bond themselves into coherent bodies, usually, although not necessarily, under the influence of pressure and elevated temperature. For the sake of clarity and simplicity, the present survey will exclude from consideration the sintering of mixed or alloyed powders, with attendant complications, but at the risk of overlooking information of general applicability. Sintering in the presence of a liquid phase is thus automatically eliminated. The sintering of alloys involves much additional subject matter and deserves separate consideration. Since the literature of the subject is extensive and widely scattered, it will not be feasible to consider the contributions individually. Instead, the subject matter will be classified according to experimental observations and theory, and will be presented in summary form. It should be noted that the appended list of references does not constitute a complete bibliography; it includes only those works quoted below. More extensive bibliographies are included in several of the references; see particularly references 7, q, 28, 34, 38, 50, 52, 54 a "Bibliography on Powder Metallurgy" published by the Library of Congress and a pamphlet published by the Metals Disintegrating Co. entitled "The Field of Powder Metallurgy and Bibliography." II. Summary of Experimental Observations The following classified list is composed of general statements of established fact derived from the experimental results reported in the published literature. A few contested observations are included, because of their potential importance; these are labeled as such. Any satisfactory and complete theory must be capable of explaining all of the uncontested facts. Obviously, some important facts may be missing from this list and these may hold the key to the correct explanation of the sintering process, but the possible lack of such material should not deter attempts to understand the subject on the basis of what is available here. A. The Initial Bond at Room Temperature a. To a limited extent uncompressed powders and massive metals adhere at room temperature.28 Clean tin powder forms a weak "cake" on standing at room temperature, the strength increasing with time. Clean gold surfaces adhere on light contact,"' as do those of many other substances, including nickel." b. Upon compression the strength of the bond is increased progressively.28 There is a limit of pressure

Jan 1, 1946

By J. T. Brown

AS far as could be ascertained, no one had previously investigated the creep strength of silicon poly-crystals. Literature has appeared showing evidence for plastic deformation in silicon single crystals and whiskers.*1"6 Also the fact that germanium, a material of similar crystal structure to silicon undergoes plastic deformation under stress at temperatures above about 60 pct of its melting temperature, has been known for some time.2"4'7 This investigation was performed for the purpose of determining the strength and ductility of silicon polycrystals under creep conditions that would give fairly long times to rupture. PROCEDURE The silicon specimen blanks were obtained by first placing granulated transitor grade silicon (99.999 + pct pure) in a silica crucible. The crucible was surrounded by a graphite susceptor, and induction heating was used for melting the silicon in a vacuum furnace. Blank specimens were formed by freezing molten silicon onto a polycrystalline seed of silicon in a vacuum furnace. The seed was attached to a motor driven revolving rod. As silicon solidified, this rod was gradually withdrawn from the melt. A shape with a contracted center section was obtained by varying the rate of withdrawal from the melt. Specimens for the creep-rupture tests were ground from these "pulled" blanks. Creep-rupture tests were performed in spring loaded machines under constant load at 1800" and 2000° F. RESULTS AND DISCUSSION A test specimen which was sectioned longitudinally is shown in the photomacrograph in Fig. 1. Very little deformation has taken place in the portion of the specimen shown, however, slip lines from several slip systems within the same grain, and deformation band formation was seen. The elongated appearance of the grains is due to the method of growing the specimens. One of the most interesting aspects of the results obtained from the creep-rupture tests was the high strength and the accompanying large amount of ductility. The data obtained is listed in Table I which shows the stress to rupture in 100 hr at 2000°F is between 8000 and 9000 psi. This indicates that silicon's strength at 2000°F is about equal to that of the best commercial super-alloys. It is important to mention that silicon has less than 1/3 the density of iron-, nickel-, and cobalt-base alloys. The usual type alloys for high-temperature applications

Jan 1, 1960

By B. F. Buie

Included in the general category of clays is a large and varied assemblage of nonmetallic silicate minerals which characteristically occur as fine-grained particles having flaky, sheetlike, or rod-shaped form. Most, though not all, are hydrous aluminum silicates. Amount and kind of impurities vary greatly, and these strongly influence the uses of the various clay types. Clays occur in a wide range of geological situations: as bedded sedimentary deposits composed of the weathering products of feldspar and other minerals; as alteration products of igneous, sedimentary, and metamorphic rocks weathered or hydrothermally altered in place; and, to a more limited extent, as hydrothermally introduced materials. TYPES AND MARKETS On the basis of chemical composition and crystal structure, two major groups of clay minerals recognized are the "kandites" or kaolin group, and the "smectites" or montmorillonite group. Another major type is illite, particularly important as a constituent of shales. Two additional mineral species having economic importance are attapulgite (palygorskite) and sepiolite. For present purposes, however, a classification based on utilization is more appropriate. The U.S. Bureau of Mines recognizes six types of clay: kaolin, ball clay, fire clay, bentonite, fuller's earth, and miscellaneous clay. Kaolin The kaolin group of minerals consists of the mineral species kaolinite, halloysite (metahalloysite), dickite, and nacrite, although the latter two are not being produced commercially. Kaolin, also called china clay, is a high-purity white material. Perhaps it is best known as a principal ingredient in the manufacture of chinaware, porcelain, and other high-quality ceramic products. However, by the mid-1970s very close to 50% of the kaolin produced in the United States was going to the paper industry for use as a filler and coating material. Manufacture of refractories uses about 12% of U.S. production. Kaolin is also used in plastics, in the rubber industry as a filler in footwear, electrical cable, and similar products, and as a conditioner of rubber for automobile tires to add strength and abrasion resistance. Smaller amounts are used in printing ink, paint, and adhesives; as insecticide carriers; in the production of catalysts for the petroleum refining industry; and in many other industrial and commercial applications. Production and use of kaolin in the United States doubled in the ten years from 1946 to 1956, and doubled again by 1966. Growth continues at a rate of about 7 % per annum.

Jan 1, 1976

By Daniel M. Bass, Paul B. Crawford

Laboratory investigations have been made to study the effect of variations in fluid characteristics, gas saturation, water saturation, and water injection rate on oil recovery by water flooding. Three synthetic gas-saturated crude oils having bubble points of 860, 1,540 and 1,885 psi were used as reservoir fluids. Repeated tests were made in which a and pack, saturated with water and synthetic oil, was produced by solution gas drive followed by water flooding at various pressure levels. Oil recovery by solution gas drive and subsequent water injection is shown to vary with the pressure and rate at which the water flood is conducted. The pressure at which optimum flooding conditions exist is shown to be a functiotl of the physical characteristics of the reservoir fluid. For the systems studied, increases in oil recoveries of near 10 per cent were obtained by flooding at the most desirable conditions. Va- riations in initial water saturations gave results similar to those in the literature. INTRODUCTION Most of the waterflooding studies investigating means of improving present exploitation processes have been conducted at low pressures with little effort to simulate reservoir conditions. Holmgren and Morse' performed a waterflooding study at 300 to 500 psi wherein the gas saturation was created by injecting gas, letting dissolved gas evolve from the oil, and then flushing the core with "live" oil until the desired gas saturation was obtained. Their results show increasing oil recoveries with increasing gas saturations. Data presented by Guerrero' and Kennedy, et al, indicate that in some instances water flooding at approximately 500 psi below the original bubble point results in a lower residual oil saturation than is obtained when water flooding above the bubble point. In their work gas saturations were created by primary depletion. By correcting low pressure flooding data for fluid shrinkage, Dyes found that a maximum oil recovery may be obtained by flooding with initial gas saturations of from 7 to 12 per cent. The purpose of this work was to determine the variations in oil recovery caused by initiating a waterflooding program at various stages of primary depletion of a core. This is a part of a more comprehensive study of obtaining criteria for determining when to initiate a pressure maintenance program and what fluids to in-ject. EQUIPMENT A schematic diagram of the apparatus is shown in Fig. 1. Fluid transfer was accomplished with metering pumps. Pressure control was ob-

Jan 1, 1957