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By Alexander N. Mitinsky

UP to a certain limit, the increase of pressure on the diamond-drill increases the rate of progress in drilling. That limit is set by the resistance of the diamonds to compression; and beyond it, the destruction of the stones will involve an. economic loss, both in time and in money. It is, therefore, important to all diamond-drillers to know what is the resistance mentioned. In Europe, operators usually follow an empirical rule, which directs the maintenance of a pressure, on the area-of the bottom of the drilling-tool, of 12 kg. per sq. 4m. For the tools in ordinary use, this is equivalent to 1 kg. per sq. mm. of the diamonds set in the tool So far as I know, American drillers are using pressures as high as 50 to 60 kg. per sq. cm. of the total area of the drill, and the consumption of diamonds (on Denny's authority, 0.2 carats per meter bored) is greater in America than in Europe. But the reason for this difference may be the comparatively larger size of the diamonds commonly used by American drillers. With the assistance of my friend, the late S. Woisslaw, who was the pioneer of diamond-drilling in Russia, I selected from his stock a number of black diamonds, which I subjected in my laboratory to compression-tests. To prepare regular cubes for such tests, as is generally done with other stones, would have been not only costly, but, what is more important, practically useless. I therefore determined, in order to assimilate as nearly as possible the conditions of actual use, to place each sample between a hard plate (corresponding to the rock) and a softer plate (corresponding to the bottom of the tool), into which it would be pressed during the test.

Jan 1, 1906

Diesel powered machines are doing some specific operations in the cyclic order required by the technical process. The dynamics of this process in certain conditions has an essential influence on environmental health conditions in the working area. The main purpose of this paper is to show, using computer simulation, how the movement (dynamic) of diesel vehicles effects environmental health standards and also how to determine the required air quantity for ventilation.

Jan 1, 1985

President Howe: It is, of course, not easy to discuss off-hand the paper which Mr. Becker has presented with so much lucidity. I will only make one remark, which is outside of the line of his argument, and concerns merely a passing allusion in his paper. Mr. Becker speaks of the fact that glass breaks with a flat or conchoidal fracture, and that steel shows a rough or " cupped " surface of frac-

Jan 1, 1895

By Ivor Jenkins

PROCESSES employing controlled atmospheres in the heat-treatment of metals and alloys are now well established on an industrial scale, and the general principles involved and the advantages to be gained in the use of the technique have received considerable publicity over a period of years. During this time the greatest emphasis has been on the establishment of the process in industry, the main effort being devoted to development work on various types of atmospheres, their useful fields of application and the design of suitable heat-treatment furnaces in which they are to be used. The various types of controlled atmospheres are fairly well standardized, but there still remains a considerable field for the investigation of related problems, in connection with both the gas-generating equipment and the surface chemistry of the heat-treatment of metals, especially in complex controlled atmospheres. This paper describes certain investigations of this nature that were carried out in England up to 1939. The development of processes employing controlled atmospheres has been associated to a very large extent with the heat-treatment of steels, both because of the major importance of steel in industry and the many diverse and difficult problems of surface chemistry involved when steels of such a wide range of composition are heated in the presence of active gases Controlled atmospheres such as dissociated and burnt ammonia or charcoal gas are used in the heat-treatment of low-carbon and high-carbon steels, but from certain points of view a suitable atmosphere generated by the partial combustion of city gas is to be preferred. Both the ammonia derivatives are comparatively expensive, and even if the burnt ammonia is regenerated, thereby reducing operating costs, the capital expenditure of the gas plant may make it prohibitive for the smaller type of furnace installation. Charcoal-gas generators are not without their operating difficulties: especially those associated with the quality of the charcoal, clinker formation and the removal of carbon dust from the generated gas. City gas has the advantage of being comparatively cheap and "on tap" in most if not all industrial centers. The use of raw city gas as a protective atmosphere in the heat-treatment of steels has been described,1 but it presents certain difficulties because of its complex composition and its explosive nature when mixed with air. These factors, together with the tendency toward sooting at elevated temperatures, arising mainly from the hydrocarbon gases present, all militate against its use as a protective atmosphere in industrial furnaces. The following analysis, based on the analyses of city gas in different localities in Great Britain, indicates the wide limits existing

Jan 1, 1947

By John F. Abel

Personal gain seems to be the most powerful incentive to economic progress. One of my first exposures to this phenomenon was the comparison between company stopes and leaser's stopes in a vein gold mine. The company stopes were 4 to 6 ft wide, whereas the leaser's stopes were so narrow that in some places one could not turn around. The company leased only that ground it felt was marginal to mine with day's- pay miners, but by skillful, careful and energetic mining, the leasers managed in most cases to make money for themselves and the company. The Hurting Truth This capitalist system, which puts a premium on successful risk taking, is under attack. Not that it hasn't been under attack all along. What hurts and angers us at this time is that the attack comes from the children of the system-its youth. Such blasphemy should, of course, be eradicated, root and branch. Or should it? Are we hurt in part because some of the things they say are true?

Jan 1, 1970

By S. Shapiro, G. Krauss

We will reply to Dr. Pitsch's discussion by 1) presenting in greater detail the single surface trace analysis which we performed on the reversed austenite plates in a single parent plate of martensite of known orientation, 2) relating the results of our analysis to the conclusions which Dr. Pitsch makes on the basis of our data, and 3) examining the validity of our selection of twenty-nine individual traces from the over 200 austenite plates which were observed in a surface of this single martensite plate. Fig. 7 shows a standard (001) projection of the martensite plate from which the austenite-martensite interface traces were taken. The traces are plotted on the projection as the small solid circles, and the great circles corresponding to the loci of plane normals which could contain each trace or could intersect the surface plane along the measured directions are also plotted. It can be seen that these great circles intersect at a point which corresponds to the normal of the surface plane on which the traces were observed. Also rate which occurred only at particularly low heating rates, see Figs. 1 and 3 in the paper.2 Since in this case the interpretation of Jana and Wayman is plausible and since we have no alternative to this interpretation, we would like to state only that the existence of a diffusion-controlled reversal at low temperatures seems to be not yet proved beyond any doubt. The author wishes to thank Professor G. Krauss for making available his manuscript prior to publication. It is also a pleasure to acknowledge the lively written discussions, which the author has had with Professors G. Krauss and C. M. Wayman prior to this communication. The financial support of the Deutsche For-schungsgemeinschaft for the work on which this communication is based is also gratefully acknowledged. plotted within small dotted circles which represent a i3 deg scatter in each of the twenty-four unit stereo-graphic triangles are our A and B poles7 and the pole P determined by Kessler and itsch.' The data presented in Fig. 7 permit a direct association of the measured traces and the various proposed habit plane poles for the reversed austenite plates in the martensite crystal. If the sample measurements do in fact

Jan 1, 1969

By Shiro Ban-ya, John Chipman

Equilibrium in the reaction was investigated at temperatures of 1500°, 1550°, and 1600°C for sulfur concentrations up to 7.2 wt pct. Multisample crucibles contained the liquid alloys in a resistance-heated furnace using a technique especially designed for the study of more complex alloys to be reported separately. Modern free-energy data are used to correct the H2S:H2 ratio for dissociation of H2S and calculalion of the partial pressure of S2. Published data on the equilibrium are similarly corrected. Thermodynanzic treatment of the data employs the composition variable zs = nS/(nFe — nS) and the activity coefficient Gs = as/zs The data at 1500" and 1550°C are fitted by the equation log s = —2.30zs. Within the limits of experimental error the same coefficient is applicable to the data at higher temperatures. Equations are given for the free-energy change in Reaction [I] as well as for the solution of S, gas in the metal. The heat of solution of 1/2 s2 is -32.28 i2.5 kcal. Uncertainty in the free energy is very much smaller. For dilute solutions of interest in steelmaking, the activity coefficient of sulfur is unchanged from that listed in Basic Open Hearth Steel-making. DETERMINATIONS of the thermodynamic properties of sulfur in liquid iron by Morris and williams1 and by Sherman, Elvander, and chipman' provided a basis for control of sulfur in steelmaking processes. From the standpoint of understanding the chemistry of metal plus nonmetal in liquid solution they left several questions unanswered. The activity of sulfur in dilute solution at about 1600°C was well-established but temperature coefficients were uncertain, due at least in part to the use of the optical pyrometer and uncertainty regarding the effect of sulfur on emissivity. It appeared that deviation from Henry's law increased with increasing temperature, a most unusual behavior requiring either confirmation or disproof. These studies were based on experimental determination of equilibrium in the reaction: At high temperatures H2S is partially dissociated so that the gas mixture contains HS, S2, and S in addition to HS. At the time of the earlier studies the free energies of these constituents were unknown and it was therefore impossible to make adequate correction for dissociation. Observations on the effects of alloying elements by Morris and coworkers1, 3 and by Sherman and Chip-man4 enable us to assess the effects of alloying elements on the activity and to make corrections for incidental impurities in the binary liquid. These studies as well as a number of more recent investigations will be reviewed in detail after out own experimental results have been presented. It was our purpose in planning this study to avoid uncertainties regarding the emissivity of alloys and the errors of thermal diffusion which plagued some of the early attempts,5 by using a resistance furnace and thermocouple in preference to induction heating and optical pyrometer. Modern data on free energies of the gaseous species are to be applied to our data and to those of other investigators to obtain corrected values of K1 and of the activity coefficient and ultimately to relate the sulfur content of the bath to the equilibrium partial pressure of S,. Extension of the study to include ternary and complex solutions will be described in a later section. EXPERIMENTAL METHOD a) Preparation and Calibration of H2-H2s Gas Mixture. The source of hydrogen sulfide was a preparer mixture of 43 pct H2S, balance hydrogen, contained in a large aluminum cylinder. This was passed through anhydrone and through a microflowmeter. Hydrogen was passed through platinized asbestos, ascar-ite, and anhydrone, and through a capillary flowmeter. Argon was passed through copper wool at 500°C, then through ascarite, anhydrone, and a flowmeter. The flow rate of hydrogen was kept constant at 200 ml per min, to which an arbitrary amount of the hydrogen-hydrogen sulfide mixture was constantly added and then the prepared gas mixture was introduced into the reaction tube through a gas mixer. In certain experiments 200 ml per min of argon was added to the hydrogen-hydrogen sulfide gas mixture to increase the total flow rate of gas. The ratio of hydrogen-hydrogen sulfide in the inlet gas was checked for each run by chemical analysis. A sample of the gas taken from a bypass was bubbled through zinc and cadmium acetate solution (4 pct zinc acetate, 1 pct cadmium acetate, and 1 pct acetic acid) to remove hydrogen sulfide from the gas mixture, and the flow rate of the remaining hydrogen was measured by a soap bubble method to determine the volume of hydrogen. The amount of hydrogen sulfide absorbed in solution was determined by titration with iodine against sodium thiosulfate, with starch used as the indicator. The ratio of hydrogen sulfide to hydrogen in the inlet gas could be kept within ±2 pct in the range from 10-2 to 5 x 10"4 which corresponds to from 0.2 to 7.0 wt pct sulfur in liquid iron. b) Furnace Arrangement. Fig. 1 shows the furnace arrangement and the shape of the alumina crucible used in this experiment. A vertical-tube silicon carbide electric resistance furnace contained the reaction tube which consisted of two parts, the gas-tight

Jan 1, 1969

By J. L. Bruce, G. W. Nicolson

THE country rock of the Mavrovouni mine of the Cyprus Mines Corp. is hydrothermally altered, disintegrated pillow lava, with very little tensile strength ("short" ground). In places, especially when wet, it is heavy ground, though not extremely heavy except where movement has been caused by underlying or nearby stoping operations. Damage by caving from roof or sides of galleries is not sudden but progressively faster when the size of the cave increases as a result of the fall of small pieces. CEMENT AND CONCRETE LININGS During early operations, galleries in the country rock were supported by customary mine-timbering methods. Available timber, however, was of poor quality and of relatively high price, and replacements were frequent and expensive. Furthermore, the massive sulphide ore bodies required large volumes of fresh air for ventilation and cooling, and it was therefore desirable to provide smooth-lined galleries with low resistance for the introduction of air to the ore bodies. It was also desirable to eliminate hazards of fire in shafts and underground workings insofar as this would be practical. Cement and concrete were relatively cheap, and plans for using these in support of shafts, underground galleries, raises, and chutes, were developed steadily. Circular shafts with diameters ranging from 10 to 15 ft were adopted for all permanent shafts and airways. In places these were lined with concrete poured behind sectional pressed-steel forms especially constructed for this purpose. In other places, they were lined with precast-concrete blocks. It was found that such precast concrete of good quality could be produced on mass production scale and delivered at the mine from most favorable point of manufacture, at a cost of about 25 cents per cubic foot of concrete. This refers to prewar costs. As the use of concrete blocks in circular lined galleries was developed, it was found that there were very great advantages in the reduction of air resistance as compared with customary timber supports. After best methods had been developed, it was found that breakage and replacements were extraordinarily low, averaging only about 1 ½ pct per year during a period of about 15 years. Furthermore, it has been possible to reclaim for re-use a very large percentage of the concrete blocks from abandoned galleries. During the history of the operations precast-concrete blocks have been used for lining shafts, raises, ore chutes, galleries, and shaft stations, ranging from 3 to 16 ft id. The thickness of lining has varied from 5 to 10 in.; with I2 in. thickness in a few cases. Junctions of two galleries at angles ranging from about 30 to 60° are usually made of poured concrete behind sectional forms, or of a combination of poured concrete and precast blocks. In nearly all cases it has been found advisable to make the point of the wedge at the junction, of

Jan 1, 1947

By Christopher W. Schram, Allan B. Tanner, Frank E. Senftle, George R. Boynton, Philip W. Philbin

A borehole sonde using a 252Cf neutron source and a Ge(Li) gamma-ray detector was field tested in a coal bed in Belmont County, Ohio, to ascertain whether such a device could be useful as a coal-exploration tool. As the sonde was lowered into the borehole, successive spectra were accumulated over short time intervals. The intensities of the capture gamma rays from hydrogen and of decay gamma rays from aluminum were determined simultaneously in each spectrum. A log of the intensities versus depth shows the depth and thickness of the coal bed. With the sonde stationary at points above, in, and below the coal bed, capture gamma rays were measured to show the variation in concentration of certain elements. From the spectrum recorded in the bed, a complete ultimate analysis, the percent ash content, and the heat content were determined without recourse to an external standard. Delayed gamma-ray analyses of the core were also made on the surface in the vicinity of the borehole in a fixed-geometry irradiation facility wing the detector in the borehole sonde. The concentrations of 10 elements were determined by this method on a coal split from the drill core. These experiments show that it is feasible to use a 252Cf- Ge(Li) borehole sonde as an aid in coal exploration.

Jan 1, 1979

By Arthur F. Taggart

The following conclusions on the work of the Hardinge mill are based on data furnished to the writer by the Hardinge Conical Mill Co. in the form of the mesh cards hereto appended. Energy units (E. U.) and relative mechanical efficiencies (R. M. E.) are computed by the "volume method" of Stadler.' Screen apertures used are the average apertures of testing screeps of the meshes given. i . Card 122. June 28, 1912. Vipond Porcupine Mines Co., Ltd., Schumacher, Ont., Canada. Ore from mill bin. Gangue, quartz and basalt. 4.5 ft. by 13 in. ball mill, Capacity, 48 tons per 24 hr. Charge, 4,000 lb. balls. Speed, 33 rev. per minute. Horsepower, 15 to 17. Water, 100 per cent. by weight. (50 per cent. ?) Product deslimed and oversise reground in pebble mill, see Card 113. Feed to mill through 2-in. mesh. Mesh Feed, Per Cent. Discharge, Per Cent.. + 1in. 5.50 ....... + 3/4. 28.00 + in. 30.00 ...... + 1/4in. 19.72 ....... + 10 10.87 2.10 + 20 2.42 8.00 -20 3.51 .....,. + 40 ....... 22.68 + 60 ...___ 10.50 4-80 ....... 11.80 + 100 ....... 3.90 -100 ....... 40.15

Jan 1, 1916

By Schneider, W. G.

IT is not my purpose to burden you with many statistics. The charts herewith should be considered merely as indicating the trend. I believe' that is what is really of interest to us. It is difficult, if not impossible to forecast with any assurance future developments, because of possible new mines, competitive materials, curtailment' or increase in the use of the metal in certain markets, and many other factors that have a vital bearing on any industry. Fig. 1 shows United States smeltet output of copper, starting with 1845. It is estimated that in 1928 the smelter output of copper will be about 1,010,000 tons. Between 1895 and 1905 it increased about 200,000 tons, and between 1905 and 1915 about 240,000 tons. Between 1915 and 1925 the increase was about 140,000 tons. This is an average increase over 30 years of about 190,00Q tons per ten-year period. At the present time the indications are that this demand for increased production will continue. As to whether or not we have the supplies or facilities to maintain this increase or a greater one, remains to be seen. Provided it is possible for United States smelters to increase their production, they should be producing at the rate of about 1,210,000 tons or more per year by 1935.

Jan 1, 1928

By G. A. Reinhardt, H. J. Cutler

ThE Youngstown Sheet & Tube Co. has produced a large tonnage of 0.35 to 0.45 carbon forging steel, the acceptance of which was based on the physical properties of test specimens obtained by forging the original 5 3/4-in. (14.5 cm.) square bloom to a 3/4-in. (1.9 cm.) round. Annealed and tempered specimens were required. The test bars were annealed by heating from 900" to 950' C. and cooling slowly in mica. The test bars were tempered by heating to 825' to 875" C., quenching in water, and drawing to 515" to 535" C. Immediately after heat treatment, the test pieces were machined to a diameter of 0.534 in. (1.38 cm.) and tested. Very good physical properties were obtained and no difficulty was experienced in meeting the specifications called for. UlTimate Strength.. Elongation, Lb. pER Sq. In. PEE Cent.. in 4 In. Not LeEs Than Annealed specimens.............. 78,230 to 92,450. 18 Tempered...................... 120,000 to 149,350 9 After experience on this material, production of slightly higher carbon forging steel was started. The method of testing this material required that test blooms be either normalized or annealed. The normalizing consisted in heating to 850" to 900" C. and cooling in still air; the annealing, in heating to 850" to 900" C. and cooling in the furnace or in mica. From the treated bloom, the test pieces were taken either by core drilling or by sawing from points midway between the edges and the intersection of the diagonals. The cores or blocks were turned to a standard 2-in. test piece with a diameter of 0.564 in. and tested without further treatment. The physical requirements of the test pieces were: yield point, pounds per square inch minimum, 44,800; ultimate strength, pounds per square inch, 89,600 to 112,000; elongation, per cent. in 2 in. not less than 17. Difficulty was encountered as soon as work on this material was started. Many precautions and refinements were instituted but it was found very difficult to secure the required elongation.

Jan 1, 1920

By Ernest R. Dickie

BRIEFLY, the ore body of the Bagdad Copper Corp., Bagdad, Ariz., is a monzonite porphyry carrying copper values fairly evenly distributed from the surface down through the primary zone. Tabular in shape, the ore body extends over several hundred acres. The oxidized zone averages about 60 ft thick and assays about 0.50 per cent copper. Under this is the chalcocite zone, or the zone of secondary enrichment, which averages about 100 ft in thickness and assays about 1.4 per cent copper. Under this zone lies the primary zone which extends in places to a known depth of about 150 ft and averages in grade about 0.60 per cent copper. Several years ago the block-caving method of extracting the ore from the chalcocite zone was installed. Then it was necessary to draw only about 250 to 300 tons per day, the capacity of the old milling plant. Early in 1943 the new 2500-ton concentrator was put into production. Drawing ore from the developed stopes in sufficient tonnage to furnish the mill at capacity proved unsuccessful in more ways than one. First, drawing the ore at an accelerated rate caused a large amount of dilution, there-by lowering the grade, and also caused funneling through to the surface. The surface material was detrimental to milling metallurgy and development of these stopes was costly per ton of ore extracted. The grade of ore decreased. making it impossible to maintain a mill head of over 0.9 per cent copper. The

Jan 1, 1947

By A. B. Young

THERE were produced in this country in 1923 probably in the neighborhood of 12,000 or 13,000 tons of refined and crude arsenic, by far the greater portion coming as a by product of smelting operations. Early this year copper smelters were producing arsenic at the rate of about 425 tons per month and lead smelters at the rate of 7;0 tons per month. During the entire eighteen years prior to 1919, there were produced in the United States only 47,000 tons of arsenic, which amounts to only 25 per cent. of the present output. The great increased demand has come about through the augmented use of arsenates as insecticides and arsenates as weed killers. In an extract from "Mineral Resources of the United States" on "Arsenic in 1922," Messrs. Heikes and Loughlin say, "The minimum possible demand for arsenic in 1923 was estimated at the end of 1922 to be about 13,000 tons, including 2000 tons for plate glass manufacturers, 3000 tons for lead arsenate, 3500 tons for calcium arsenate, 1500 tons for weed killers, 1200 tons for Paris green, 1000 tons for sheep dips and 750 tons for proprietary mixtures. More recent information, however, indicates twice as great a demand for calcium arsenate." The latter has found great use in the last three or four years as a weapon to combat the boll weevil pest of the southern cotton belt. ~t the present writing refined white arsenic is being quoted on the New York market at from 13)d c. to 1455 c. per Ib., while the average price during the eighteen-year period just mentioned was 4.8 c.

Jan 1, 1924

Carlisle: Jim Knapp, has been the good friend of hundreds-maybe thousands-of mining men in these western states in the last 40 or 50 years. Jim is going to talk about many of the mining camps of Nevada, where he has done plenty in the mining field during the last 50 years. Jim, for a starter, how did you happen to go to Nevada? Knapp: In the summer of 1902, two years after the discovery at Tonopah, the professor of mining at Stanford sent out myself and another student by the name of Joe Miller to make a report on the camp. We left San Francisco at 8 p.m., got to Reno the next morning, then took the train to Sodaville, arriving about 4:30 in the afternoon. The first man I met when I arrived at the Tonopah station was Tasker Oddie, a gentleman who later became the Govenor of the State and then a United States Senator. Before we got away from the stage station I also met S. H. Brady, the first mining engineer to put out his shingle in Tonopah. He afterwards became general manager of the West End Mining Co.

Jan 3, 1965

By John A. Emery

The Pea Ridge iron ore deposit near Sullivan, Missouri, is a dike-like mass of magnetite enclosed in Precambrian porphyries. The ore body tops at the Precambrian surface at a depth of 1300 feet below the present surface and extends to an unknown depth. It dips nearly vertically, intersecting the dip and strike of the enclosing porphyries at an extremely sharp angle. Faulting, both pre- and post-ore, appears to be of minor consequence, and present knowledge indicates that no preferred structural conditions existed prior to emplacement. The ore body is composed of magnetite with specular hematite, quartz, apatite, and pyrite occurring as accessory primary minerals. Specular hematite in appreciable quantities occurs on parts of the cap and the footwall of the ore body. Fresh porphyry breccia is enclosed in the magnetite along the hanging wall and in the western portion of the ore body. Hanging-wall quartz-amphibole and footwall quartz-hematite occur as replacements of certain porphyries. Further alteration has caused sericitization of parts of these zones. The ore deposit is interpreted as having been formed essentially by a single injection of a magmatic differentiate with hydrothermal end phases forming the quartz-amphibole and quartz-hematite portions of the deposit.

Jan 1, 1968

By G. F. Bolling

Single crystals of each metal were deformed at 77°K and heated at constant rates, variously in the range 0.125" to 4o°Kper min from 77" to -390oK, while being monitored in an X-ray diffractometer. Changes in diffraction-peak heights and line breadths were used to ascertain the temperature ranges of recrystalliza-tion. The results were subjected to the analysis of nicholas' in order to obtain the rate-controlling activation energies,Q. In this analysis no recourse to a separate and distinct nucleation stage is required and the results of studying recrystallization proved consistent with the hypothesis of a constant number of nuclei or equivalent hypotheses. The values Pb = 5.5 ± 0.5 keal per mole Zn ~ 7.5 Sn - 5 Bi - 9. 5 correspond for lead, zinc, and tin to activation energies obtained elsewhere for grain boundary migration, and for bismuth and lead to previous studies of re-crystallization by Barrett.6 This correlation allows the conclusions that interference from recovery was minimal and that the observed recrystallization rates in these pure metals are effectively governed by grain boundary migration. Good agreement was not found between the results of this kind of study in zone-refined aluminum and previous work; and supplementary isothermral experiments involving hardness tests and metallography did not resolve the discrepancy. Nevertheless, at least a range,Q = 11.5 ± 2 keal per mole, can be assigned to the activation energy for boundary migration in aluminum. An experimental study of one aspect of the recrystallization process is presented here for four metals of different crystal structure. The metals chosen for study were all zone-refined to reduce impurity effects, but the attendant high purity presented a difficulty. For any reasonably high driving force a "re-crystallization temperature", TR, is in the range of 0.25 T,, where T, is the absolute melting point, and study was therefore restricted to lower temperatures. An X-ray technique under constant heating-rate conditions adequate above 90°K was devised for the study; in consequence, a newer type of analysis following Nicholas1 had to be used to obtain quantitative information about activation energies. The standard methods of studying recrystallization have involved the comparable analyses of Johnson and Mehl2 and Avrami3 which are reviewed by Burke and Turnbull.* The general analysis4 which is applied only to isothermal studies using any of various investigative techniques states:

Jan 1, 1968

By E. S. Machlin, W. R. Yankee

IN a previous study1 of the effect of heating com-mercial titanium in air on its subsequent friction coefficient against other metals, as well as itself, it was found that the friction coefficient markedly decreased from a value of about 0.7 to about 0.3. A tentative explanation was given that surfaces normally produced at room temperature are not contaminated sufficiently to prevent seizing or welding of the titanium to the softer mating metals. The latter tend to cleanse themselves during rubbing over the harder titanium. It was thought that the lack of a contaminant protective film on the titanium was due to the high solubility of titanium for oxygen and nitrogen and hence an inability to form a contaminant oxide or nitride. This explanation requires the ratio of the surface absorption rate to the diffusion rate to become much lower at room temperature than it is at high temperatures. In order to check the phenomenon further, commercial titanium specimens were nitrided or oxidized at 800°C for 20 hr in flows of prepurified N2 and 01, respectively, at about 1/2 in. H2O above atmospheric pressure. Friction runs were made in argon using a freshly cut copper hemisphere (cut in argon) on surfaces cut successively into the diffusion layers in the titanium (cut in argon) using the techniques described in a previous publication.' DPH values (100 gram load) were made as a function of depth into the diffusion layer using a Tukon tester. Also, micrographs were taken at separate cross sections to indicate the diffusion layers. The results obtained are presented in Figs. 1 and 2, which show the "static" friction coefficient vs hardness for the nitrided and oxidized specimens, respectively. A separate measurement of the friction coefficient of clean copper vs iodide titanium also was made. From results reported in the literature' giving the oxygen and nitrogen contents as functions of the hardness, cross plots were made showing the friction coefficients as functions of the amount of interstitial solute. These plots are given in Figs. 3 and 4. From micrographs of the diffusion layers and the phase diagrams, it was deduced that the data in Figs. l through 4 correspond to the single phase a region. The points observed on the compound regions have been excluded from the figures. It is apparent that nitrogen or oxygen in solution in the a titanium markedly affects the friction coefficient against a softer mating metal. Discussion of Results These results are extremely interesting from both a practical and theoretical viewpoint. The theoretical implications will be discussed first. According to Bowden, the friction coefficient should be given to a good approximation by the relation where a is the fraction of contact area that has welded, a is the shear strength of weaker component, and H is the hardness of softer component. Using this relation alone, it is difficult to understand the results because none of the terms should be affected by a variation in the oxygen or nitrogen content of the harder and stronger metal, titanium. Even if the ratio of S/H for titanium is used in Eq. 1, the ratio has been shown to be independent of oxy-gen or nitrogen content.' If a more rigorous equa-tion is used combining Eq. 1 and a result given pre-viously" for the case where welding is absent, then the relation obtained is µ = a S/H + (1-a) a W aß/H where a is constant and Waß is the work of adhesion between the two metals comprising the friction couple. This relation states that if a is less than 1/2 or so, variation in the work of adhesion Waß between copper and the titanium should affect the friction coefficient markedly. It is reasonable to expect that the work of adhesion will depend on the oxygen or nitrogen content of the titanium. Available data4 show that clean metals and oxides have much lower works of adhesion than the same metals against the

Jan 1, 1955

By R. F. Bell, L. W. Eastwood, R. W. James

Among those concerned with the annealing and heat-treating of aluminum and aluminum alloys, it is well known that after co1d-working a coarser grain is usually produced by slow heating than hy more rapid heating. Consequently, for the control of the grain size produced by annealing or heat-treating cold-worked aluminum and aluminum alloys, the heating rate is of considerable practical importance. References in the current literature on the effect of heating rate are numerous, but it appears neither necessary nor desirable to give here a review of the former nark done on this subject. It became evident during some preliminary work on the recrystallizn-tion of aluminium and aluminum alloys that the effect of heating rate depended upon the type of microstructure of the metal. This observation led to the following study of the relationship of the type of microstructure of the alloy to the effect of the heating rate. Materials Investigated Analyses of the aluminum and aluminium alloys investigatted are given in Table 1. Three classes of material are listed, as follows: Class I.— Belonging to the first class are pure aluminium and aluminium containing a second constituent that is soluble in the aluminium matrix at

Jan 1, 1939

By R. F. Bell, R. W. James, L. W. Eastwood

Among those concerned with the annealing and heat-treating of aluminum and aluminum alloys, it is well known that after co1d-working a coarser grain is usually produced by slow heating than hy more rapid heating. Consequently, for the control of the grain size produced by annealing or heat-treating cold-worked aluminum and aluminum alloys, the heating rate is of considerable practical importance. References in the current literature on the effect of heating rate are numerous, but it appears neither necessary nor desirable to give here a review of the former nark done on this subject. It became evident during some preliminary work on the recrystallizn-tion of aluminium and aluminum alloys that the effect of heating rate depended upon the type of microstructure of the metal. This observation led to the following study of the relationship of the type of microstructure of the alloy to the effect of the heating rate. Materials Investigated Analyses of the aluminum and aluminium alloys investigatted are given in Table 1. Three classes of material are listed, as follows: Class I.— Belonging to the first class are pure aluminium and aluminium containing a second constituent that is soluble in the aluminium matrix at

Jan 1, 1939