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By John Hall

THE Fremont test for measuring the energy consumed in breaking a notched bar of steel is not so well known in this country as it deserves to be. The test specimen used in this test is about 3/8 by 1/4 by about 1 1/4 in., notched with a hack saw on the lower side to cause the piece to break at a fixed point. A weight of 10 kg. falling 4 m., and provided with a knife or chisel which strikes the specimen, breaks the test piece by impact. The residual force in the falling weight after it has broken the specimen is recorded by a suitable device, and the difference between the total energy and the residual energy of the weight (in kilogrammeters) is the force consumed in breaking the specimen. An experience of several years with the Fremont testing machine has shown its great value in readily detecting brittleness not revealed by tensile testing or slow bending testing. I this paper it is proposed to discuss (1) the supersensitiveness of the test as applied to cast steel and (2) its value in revealing the effect of heat treatment under certain conditions. .

Jan 7, 1913

By T. S. Jr. Sligh

OF all the qualities that are essential in a good cigar tobacco none is quite so important as the burn. This term is general and includes many points, the most important of which are evenness of burn, color of ash, firmness and coherence of ash, and fire-holding capacity. The fire-holding capacity refers to the length of time the leaf or cigar will continue to, glow after ignition. Chlorides tend to prevent complete combustion and products are formed thereby that are injurious to the flavor and aroma. On the other hand, the carbonates of the alkalies, particularly of potassium, aid the combustion and increase the fire-holding capacity. Barth1 thought that the harmful effect of the chlorides was due to their fusing and coating the tobacco, thereby preventing complete combustion. Schlosing,2 Nessler,3 and Garner,4 suggested widely different theories to account for the favorable action of potassium salts. In order to study carefully the action of the various salts upon the course of combustion of the cigar a knowledge of the temperature of the burning cigar is necessary. Lehmann5 who seems to be the only investigator who has made any attempt to determine the temperature of a burning cigar gives 480° C. as the maximum temperature which he recorded. It is evident, however, that his measurements were in error, probably on account of the method and apparatus used, since the lowest visible red corresponds to a temperature of about 575° C.

Jan 9, 1919

[ ] Utilizing tendencies for low grade ores in the Sudbury District of Ontario to cave after higher grade ore has been mined, International Nickel Co., of Canada, Ltd., is recovering millions of tons of nickel-copper ore once regarded as submarginal. Inco is working lower grade ore than ever mined before from its underground operations because of the caving method and metallurgical practices. In the caving method, blocks containing as much as 1.5 million tons of ore are undercut. As ore from the undercut block is withdrawn, the block to be mined breaks away and starts to disintegrate as it moves downward. Inco is also using the blasthole method, using explosives to break slices of harder, tougher ore from solid material. Inco has built a new concentrator at one of its most recent shafts for handling the increased tonnages of low grade ore. The concentrator presently has a 10,000-ton per day capacity, and is scheduled to be increased to 12,000 tons. Hoisting from the mine is by push-button control and the ore is milled on the spot. A 7 ½ -mile pipeline carries bulk concentrate to reduction plants at Copper Cliff. Giant crushers, weighing 165 tons each, have been installed underground. Twenty-ton electric locomotives haul ore to the crushers. The expansion program is expected to lift total annual production of nickel in the free world to 375 million pounds annually, an increase of 150 million pounds. Inco is presently mining more than 1 million tons of ore per month from combined surface and underground operations.

Jan 1, 1952

By P. B. Baxendell, R. Thomas

Work on the calculation of vertical two-phase flow gradients by Cia. Shell de Venezuela has been based mainly on the "energy-loss" method proposed by Poett-mann and Carpenter in 1952. The "energy-loss-factor" correlation proposed by Poettmann and Carpenter was based on relatively low-rate flow data. This correlation proved inapplicable to high-rate flow conditions. In an attempt to establish a satisfactory correlation for high rates, a series of experiments was carried out at rates up to 5,000 BID in Cia. Shell de Venezuela's La Paz field in Venezuela, using tubing strings fitted with electronic surface-recording pressure elements. As a result of these experiments a correlation between energy-loss factor and mass flow rate was established which is believed to be applicable to a wide range of conduit sizes and crude types at high flow rates (e.g., above 900 BID for 27/8-in. OD tubing). It is anticipated that the resulting gradient calculations will have an accuracy of the order of % 5 per cent. At lower flow rates the energy-loss factor cannot be considered as constant for any mass rate of flow, but varies with the free gas in place and the mixture velocity. No satisfactory correlating parameter was obtained. As a practical compromise for low flow rates, a modification of the curve proposed by Poettmann and Carpenter was used. In practice this was found to give gradient accuracies of approxirnately ± 10 per cent clown to flow rates as low as 300 B/D in 27/8-in. tubing. INTRODUCTION Production operations in Cia. Shell de Venezuela's light- and medium-crude fields are principally concerned with high-rate flowing or gas-lift wells. Under these conditions the analysis of well performance, the selection of production strings and the design of gas-lift installations are vitally dependent on an accurate knowledge of the pressure gradients involved in vertical two-phase flow. Initially, attempts were made to establish the gradients empirically as done by Gilbert,' but the results were not reliable due to scarcity of data over a full range of rates and gas-oil ratios. Several methods of calculation based on energy-balance considerations were attempted, but the computations were cumbersome and the results cliscouraging. In 1952 a paper was published by Poettmann and Carpenter' which proposed a new approach. Their method was also based on an energy-balance equation. but it was original in that no attempt was made to evaluate the various components making up the total energy losses. Instead, they proposed a form of analysis which assumed that all the significant energy losses for mutiphase flow could be correlated in a form similar to that of the Fanning equation for frictional 1osses in single-phase flow. They then derived an empirical relationship linking measurable field data with a factor which, when applied to the standard form of the Fanning equation, would enable the energy losses to be determined. The basic method was applied in Venezuela to the problem of annular flow gradients in the La Paz and Mara fields" This involved establishing a new energy-loss-factor correlation to cover high flow rates and, also, some adaptation of the method to permit mechanized calculation using punch-card machines. The final result was 1 set of gradient curves for La Paz and Mara conditions which proved to be surprisingly accurate. With the encouraging results of the annular flow calculations, several attempts were made to obtain a corresponding set of curves for tubing flow. Here, unfortunately, little progress could be made. The original correlation of Poettmann and Carpenter was based on rather 1imited data derived from low-rate observations in 23/8- and 27/8-in. OD tubing. It did not cover the higher range of production rates, and extrapolation proved unsuccessful. A new correlation covering high flow rates was required, but this proved to be extremely difficult to establish since tubing flow pressure measurements at high rates did not exist—due to the difficulty of running pressure bombs against high-velocity flow. The necessity for reliable tubing flow data increased with the development of the new concessions in Lake Maracaibo, where high-rate tubing flow from depths of 10,500 ft became routine. Thus. it was decided to set up a full-scale test to establish a reliable energy-loss factor for tubing flow conditions. A La. Paz field light-oil producer with a potential of approximately 12,000 B/D on annular flow was chosen. To obtain full pressure gradients, a special tubing string was installed which was equipped with electronic surface-recording pressure measuring devices,

By F. S. Crawford

IRON and copper are mined in the Lake Superior district. The iron mines of the district have the best safety record for that industry in the country as a whole, while the copper mines of the district rank second in two of the four years recorded (Table 1). In Utah copper comes mainly from open-pit mines, which enables that state to lead easily in safety. All of the Michigan production comes from deep underground workings. About 60 per cent of the iron miners in St. Louis County, Minnesota, are employed at open-pit mines; this favorably affects the combined open-pit and underground accident-frequency rate, as this county provides most of the Minnesota-mined iron ore. In Michigan, however, there are few open-pit mines, the bulk of the production coming from underground mines, while all of the Wisconsin production, just across the state line from Michigan, is from underground mines. In spite of the fact that fewer mines in Michigan use the safer open-pit method, the iron-mining industry of that state maintained a consistently low record from 1931 to 1934; however, it was many points behind its nearest competitor, Minnesota, with its much greater production from open-pit mines.

Jan 1, 1939

By Alfred F. Beasley

The slags derived from the smelting of lead and copper ores are composed essentially of silicates. The problems arising from the smelting of these ores consequently involve the study of silicate fusions. In the absence of specific knowledge concerning the compounds occurring in slags, it has been the practice of metallurgists to treat them in terms of their total chemical composition. Slags have been classified as monosilicates, bisilicates, sesquisilicates, and subsilicates according to the relative amounts of oxygen in the acid and basic radicles of the hypothetical salt produced. While this has been a useful guide to metallurgists in computing the furnace charges, it falls far short of a basis for the scientific investigation of slags. In order to understand the nature of a slag as a whole it is necessary to learn the physical and chemical properties of the mineral compounds which go to make up that slag. The efficiency with which an ore is smelted in a furnace depends primarily on the physical properties of the compounds formed during the operation. When the melting points and fields of stability of each of the mineral compounds in slags have been established, it will be possible to determine the properties of any given slag by examining the nature and amounts of its mineral constituents. Earlier Investigations In 1884 and succeeding years an extensive survey of lead and copper furnace slags was made in Europe by Vogt, and a large part of the present knowledge of the subject is due to his publications.' Vogt's interest in artificial fusions was directed primarily towards the explanation of problems in igneous and economic geology and his subsequent works have been confined wholly to that subject.

Jan 1, 1930

By J. F. Lewis

Much has been written on this great engineering work, principally from the civil engineer's stand-point. In presenting the subject to the Institute, it seems necessary to include something of geology as well as engineering. In this case, it is particularly the glacial and post-glacial periods with which we are concerned; for it has been clearly proved that the canal recently excavated has not for the first time opened the Des Plaines valley for drainage away from Lake Michigan, and that this valley, as well as the site of this city, is very closely connected with the processes and effects of the ice period. We have simply renewed a channel and a drainage direction which formerly existed. As the days of deep water-ways for commercial purposes are fast approaching, engineers may find the consideration of ancient topography and geologic changes highly useful. For what I may say on this subject I am greatly indebted to Mr. Ossian Guthrie, who has made an earnest study of glacial geology and labored especially to decipher the records of its history in this region. * Chicago is situated in the track of one of four great glacial ice-streams that swept down from the North: one moving due South from Marquette and entering the Illinois valley at Ottawa; one through the Lake Michigan valley, entering the Illinois valley near Lemont; one from Saginaw Bay diagonally across the States of Michigan and Iadiana, entering through

Jan 1, 1898

By Pei-Yung Huang, C. R. Hayward

In order to understand more fully the actual state of copper lost in copper reverberatory slags, a systematic study on the various reactions between certain metallurgically important copper compounds and synthetic copper reverberatory slags was undertaken by the authors in the Massachusetts Institute of Technology from 1942 to 1945.1 This paper, being only a part of the work completed, is published first because it furnishes the first experimental evidence of the formation of copper ferrite from reactions between cuprous oxide and copper reverberatory slags. Choice of Slag Composition The choice of the composition of the synthetic reverberatory slags to be used was much deliberated. Commercial copper reverberatory slags, neglecting minor constituents, avcrage :2,3 45 to 47 pct FeO; 38 to 42 pct SiO2; 5 to 6 pct CaO; 5 to 6 pct A12O3. Since the ternary system CaO-FeO-SiO2 has been much more thoroughly studied4 and is much simpler than the quaternary system CaO-FeO-SiO2-Al2O3, it was decided to use calcium oxide only instead of calcium oxide and alumina in the synthesis of the slags. Fortunately the composition of the average copper reverberatory slag with calcium oxide substituted for alumina lies in the region of the phase diagram clarified by the investigators. A survey of the phase diagram (Fig I) suggested two compositions: (I) the composition near the invariant point S, which is made up of 46 pct ferrous oxide, 37 pct silica and 17 pct calcium oxide; (2) the composition near the invariant point K with 45.5 pct ferrous oxide, 43 pct silica and 11.5 pct calcium oxide. Composition S has the advantage that the percentages of ferrous oxide and of silica almost exactly coincide with those of the average reverberatory slags, and that of the lowest melting point (1093º ± 3ºC) in the whole ternary system. The calcium oxide content, however, obviously is high. Since we have already substituted calcium oxide for alumina, and since calcium oxide is more basic than alumina, the fulfil- slag is decidedly too basic. Composition K has a slightly higher melting point (1150O + 3OC) and a higher silica content, but this is preferred because the slag is saturated with respect to tri-dymite and thus should not corrode siliceous refractories. Besides, it is less basic than composition S. The filial slag composition, therefore, was chosen to

Jan 1, 1949

By F. George, W. Tice, M. Salkind

It was found that Al-A13Ni could be readily cold rolled perpendicular to but not parallel to the whiskers. Reductions of more than 98 pct were achieved without cracking by rolling perpendicular to the whiskers, whereas extensive edge cracking was noted after only 15 pct reduction when rolling parallel to the whiskers. The longitudinal and transverse tensile strengths were nearly doubled, and the longitudinal yield strength more than tripled by cold rolling 50 pct in a direction perpendicular to the whiskers. The whiskers exhibited some waviness (elastic bending) as a result of cold rolling, but at very high reductions (greater than 75 pct) whisker fracture and misalignment became significant. A fine dislocation substructure in the matrix consisting of cells attached to the whiskers was pro -duced by cold rolling. Most of- the substructure was readily removed by a 1-hr anneal at 500°C. Cold rolling was found to substantially reduce the thermal stability of the microstructure at 610°C but did not affect the stability at 500°C. FIBER and whisker reinforced composite materials promise significant improvements in properties over conventional materials. Before they find wide use, however, it will be necessary to understand the response of these highly anisotropic materials to common metalworking processes. Most of the nonmetal-lic fiber reinforced materials have very low elongations (a few pct or less) in the direction of fiber alignment. Thus, metalworking techniques such as rolling and forging would not be as broadly applicable to these materials. This investigation was initiated to determine how a composite system consisting of Al3Ni whisker reinforced aluminum responded to rolling, what changes in the microstructure occurred, and the effect of deformation on the mechanical properties. The composite material studied was produced by unidirectional solidification of the A1-Al3Ni eutectic alloy'-7 and consisted of 10 pct by volume of aligned whiskers of Alai in a matrix of aluminum. It should be pointed out that this system is not representative of all composite materials, and the results will therefore not be universally applicable. The A1-Al3Ni system is characterized by: 1) A strong fiber-matrix interfacial bond 2) A ductile matrix 3) A sufficiently low fiber content to allow significant plastic flow between fibers 4) Strong, completely elastic whiskers (tensile strength 400,000 psi, elastic modulus = 20 X 106 psi.1 These factors allow the material to be readily rolled perpendicular to the fibers. If the fiber-matrix bond were not strong, such a weak interface could fail during rolling. A measure of the ability of a composite to be rolled in the transverse direction can be obtained from noting the transverse tensile behavior. In the case of Al-Al3Ni,2 there is considerable ductility (15 to 30 pct). In the case of boron filament reinforced aluminum, for example, the transverse elongation is less than 1 pct,8 and the material could probably not be cold rolled as readily in that direction. EXPERIMENTAL PROCEDURE 3-in. diam ingots of A1-A13Ni eutectic were unidi-rectionally solidified in graphite crucibles. The starting materials consisted of 99.99+ pct pure nickel and aluminum, and the pure eutectic ingots were made with 6.2 wt pct Ni. The unidirectional solidification process (described in detail elsewhere1-3) consists of preparing a master heat of eutectic composition, remelting, and withdrawing the ingot vertically downward through the heat source at a controlled rate so that plane front solidification proceeds upward at a constant velocity. The resulting microstructure consists of 10 pct by volume of whiskers of very high aspect (length to diameter) ratio. The fiber lengths have not been measured because of the difficulty of detecting fiber ends9 but exceeds 104. There is some possibility that the fibers may be continuous within one grain. Flat sheet specimens 2¾ in. sq and approximately 0.2 in. thick containing whiskers parallel to the plane of the sheet and to one edge were used for this study. A1-A13Ni exhibits either a rod-like (high solidification rates) or a blade-like (low solidification rates) whisker morphology,1,3 and both types were studied. Rolling was accomplished using a two-high rolling mill at a speed of approximately 10 fpm. The rolling direction was either parallel to or perpendicular to the direction of growth (direction of whisker alignment). Reductions of from 0.002 to 0.03 in. per pass were used with the most common value being 0.005 in. per pass. Cold rolling of Al-Al3Ni to more than 98 pct reduction in thickness was accomplished with no intermediate anneals. In addition. a series of speci-mens was cold rolled 97 pct with a 1-hr, 500°C anneal in air after each 50 pet reduction. Tensile testing was accomplished using a Tinius-lsen four screw testing machine. Flat sheet specimens + in. wide and between 2 and 2; in. long with the thickness dependent upon rolling reduction, were used. The gage section was in. wide and 1 in. long. Strain was measured using a clip-on LVDT extensome-

Jan 1, 1970

By Charles Austin

IN an earlier series of studies on 18-8 stainless steel at 600°, 700°, and 800°C.1 one pretreatment was used throughout; viz., 15 min. in hydrogen at 950°C., followed by an air quench. Several manufacturers of this alloy since have expressed doubt as to the suitability of the temperature employed, recommending instead the more customary Strauss treatment as promising superior results. In this subsequent investigation on the effects of the temperature of pretreatment several interesting points have arisen, which are described in this paper. Previous work on our equipment had shown a marked difference between alloys of "similar chemical composition" that had been manu-factured by different companies. Accordingly, one mill-bar length was selected from which to prepare all specimens. It could then be assumed that any marked differences in creep characteristics would be due to effects resulting from variations in the pretreatment of the alloy. The material was furnished by the Allegheny-Ludlum Steel Co. in the form of 5/16-in, dia. rod, finished by air cooling from a mill anneal at 1950°F. (1066°C.). It was analyzed only for the elements shown: carbon, 0,07 per cent; chromium, 18.73; nickel, 9.46; manganese, 0.40. Three pretreating temperatures were chosen, the specimens being held for 15 min. in hydrogen at either: (1) 1150°C., to conform to the recom-mended Strauss treatment; (2) 950°C., to compare with the results of previous tests; or (3) 750°C., to initiate precipitation of carbides in the material before testing. As the test cross sections were only 1/8 -in. dia., air cooling followed the annealing treatment. These treatments per-mitted two direct comparisons: (1) between the 1150° and 950°C. treat-ments to indicate the effect of grain size when all carbides were probably in solution at the start of the test; and (2) between the 950° and 750°C. treatments to indicate the effect of carbide "nucleation" for similar grain sizes.

Jan 1, 1940

By Robert H. Richards

It will hardly be worth while to spend time over the discovery of this mine, how lumps of galena were picked up and brought to town, and how legends were told of an old mine from which Revolutionary bullets were made. This is an entirely new mine, with no evidences of former or ancient workings in its immediate vicinity to guide or attract the prospector. The first pit was opened in May, 1874. In August I made a visit to this pit, which was 6 feet wide in the northwest direction, 12 feet long north 80° east, and 6 feet deep..About 4 tons of a galena carrying gray copper, siderite, and quartz, had been taken from this pit. The lumps were all of them evidently float specimens, and varied from 8 to 12 inches thick, and showed very distinct indica-

By P. B. Bucky

IN previous publications1 it was shown that a scalar model of any weighty structure, where the stresses produced are mainly due to gravita-tional forces, will behave similarly to its prototype if the model and proto-type material are the same arid the model is placed in a centrifugal field of force (substituted for the gravitational field) which has been increased in the same proportion as the linear model scale is decreased. This principle is now being applied to a study of the behavior of mine structures in an attempt to determine the laws that control them. The importance of using models as a means of solving mining problems has been discussed previously, yet it may be well to reiterate here that this method of research and type of solution have been productive of far-reaching results in other engineering fields, notably those of hydraulics and aerodynamics. Model research is a comparatively cheap and time-saving method of checking practical experience. Up to the present time the best guide to what will happen underground has been the judgment of the man who has observed most and been longest acquainted with the local conditions. His experimental work underground is limited by the elements of cost, time and danger, while failure is seldom permissible. In a model, as in a test tube, all elements that affect the solution of a problem are under definite control. Each element may be varied independently at will and its effects noted. Experimental work on a small-scale model may there¬fore be performed at a comparatively small expenditure of time and money, instead of on a full scale in the mine, where the cost, time, and danger elements are necessarily great. The experiments described in this paper are to be considered as part of a progress report and a continuation of Technical Paper 425. One object of the research program is to make each experiment point the way for further research on that particular phase of the general problem. The results and conclusions presented here are therefore not to be considered as final, but are to be interpreted as

Jan 1, 1933

By W. E. Keck

THE potential iron ores of Michigan can be classified from the stand-point of the predominant impurities into siliceous, sulphurous and phos-phorous ores. Research on the flotation of each of these classes of ore was carried out in the following Planner. The flotative properties of the valuable minerals of iron and of the worthless and deleterious ones were first determined under carefully controlled conditions. This information was then applied to synthetic mixtures of these minerals, which simulated the potential ores. Finally, data obtained during the two foregoing stages of the investigation were used in the flotation beneficiation of samples of the potential ores. Hematite is the most important mineral of iron in each of the above classes of iron ores. This paper deals with a study of that mineral in the very nearly, pure state. There are two varieties of the mineral-specular hematite and massive hematite. The latter is the principal variety, but the former is an Impor-tant mineral of iron in some of the potential ores. Because of this condi-tion, flotation research was performed with both varieties. This research consisted essentially of: (1) a survey of the literature on hematite flota-tion, (2) the preparation of pure massive hematite, (3) the preparation of pure specular hematite, (4) the; development of a laboratory procedure and (5) flotation experimentation. For the purpose of this discussion, the results of previous work on the flotative properties of hematite can be summarized as follows: Specular hematite has been readily floated with terpineol and sodium oleate or heptylic acid1. Further, hematite has been likewise floated with a pro-prietary frother and oleic acid or other soluble oils 2. Finally, lead nitrate, copper sulphate, silver nitrate, chromium nitrate, mercuric chloride, ferric

Jan 1, 1937

By H. J. Struth

In these trying times of proration and low oil prices, it is decidedly necessary for all branches of the petroleum industry to accord full recognition to the economic phenomena that contribute to its varying state of welfare. Perhaps no other single factor has a more important bearing upon the general oil situation than the supply and demand of gasoline. Year after year, the records have shown that the degree of prosperity or depression accompanying the industry's developments has been to a large extent influenced by the degree of balance maintamed between the supply and demand of gasoline. More and more it is being realized within the industry that equilibrium between the supply and demand of gasoline forms the basic structure of crude and product market values and, consequently, the deciding factor in the financial results of the industry as a whole. The influence of the gasoline situation upon the market and financial structure of the petroleum industry was effectively demonstrated during 1930, when excess accumulation of gasoline undermined not only the refined oil market but the crude market as well. In fact, it was a top-heavy gasoline situation that defeated the realization of benefits that might have accrued from an otherwise favorable statistical position in the producing branch of the industry. Indicative of this is the fact that crude oil production was curtailed to the extent of 98,323,000 bbl. last year, while refinery runs to stills were maintained at an excessive rate until late in the year, creating an excess gasoline production of 6,663,000 bbl. above actual requirements. Nevertheless, the movement to curtail refinery operations during the closing months of the year prevented a far worse situation, although it came too late to turn the ebbing momentum of the general oil market. Despite the severe depression of the market values that accompanied 1930 developments, it can be said that the results attained during the closing months of the year, in the direction of production control, marked a decisive turn in the industry's economic affairs. In fact, a review of the oil situation from every angle points definitely to a better general understanding and recognition of the workings of the economic law of supply and demand. As a result, the year closed with crude production in

Jan 1, 1931

This is a most interesting paper and some data in it are corroborated by work I did at Watertown Arsenal some time ago with iron powder. I would like to ask Dr. Wulff to say just a little more about the compressive and tensile stresses on the surface of compacts. JOHN WULFF (author's reply).-Our work has not yet been completed; although enough data have been obtained with cylindrical compacts of iron to permit some conclusions. Briefly, in a compact 3/4 in. high and 1/2 in. in diameter pressed at 48 tons per sq. in., the residual stresses on the surface measured by X-ray diffraction techniques are as follows: The radial stresses on top center and bottom of compacts are practically zero; the longitudinal residual stresses on the side walls are near the top quarter of the compact about seven tenths that of the yield point of mild steel in tension; at the center surface of the compact they are in compression and in magnitude about 0.3 that of mild steel in tension; near the bottom, they are practically zero. F. V. LENEL.?- I was particularly interested in the work that Messrs. Wulff and Seelig reported on the influence of lubrication on the density of parts. In connection with the work of the American Society for Testing Materials on determining the green density of a compact, we ran into considerable difficulty in getting reproducible results of green density determinations. It was much easier to get a reproducible green density when the lubricant was mixed with the powder than when the lubricant was applied to the die walls; particularly when the die was not perfect-i.e., if it was somewhat rough or out of round. In this case, it was almost impossible to get reproducible green densities when the die walls were lubricated, while it was not too difficult to get reproducible

Jan 1, 1946

By Raymond Ward

IN the past few years several papers have appeared dealing with different aspects of the oxidation of dilute alloys, especially with respect to the formation of internal oxides or subscales. Subscale has been defined1 as that layer or zone of oxide particles precipitated in a matrix of metallic metal in which the oxide particles are dispersed uniformly and occur by diffusion of the oxygen inward from the metal surface. Alloys composed of a solvent metal more noble than the alloying elements are subject to subscaling or internal oxidation. In these alloys the solute must be present in such quantities that if the alloy is exposed to an oxidizing atmosphere at elevated temperatures, the rate of diffusion of the oxygen into the metal will be greater than the rate of diffusion of the solute outward. There is a composition range of the iron-silicon system that falls into this classification. Knowledge of the nature and rates of oxidation of iron-silicon alloys is of great commercial importance, but very little information of this nature is available. Darken2 recently has made calculations to show the limits of concentration of silicon for which subscales are produced in iron-silicon alloys; however, the main thesis of his paper was to analyze and to explain the already existing data. The purpose of this paper is to present the effect of com position, temperature, time, and atmosphere on the type of scale-metal layer obtained and to give some qualitative indication of the effect of these variables on the rates of oxidation. Since this paper is a study of silicon steels that are available commercially, extremely low-silicon and high-silicon alloys are not included. EXPERIMENTAL PROCEDURE The alloys used in the experiment were taken from heats of silicon steel that ranged in analysis from 0.70 to 5.8 per cent silicon. This composition range takes in most of the commercial silicon steels. In Table I are listed the compositions of alloys used. Other than iron and silicon, the alloys normally contained approximately the following impurities: carbon, 0.03 per cent; manganese, 0.07; phosphorus, 0.008; sulphur, 0.02; copper, 0.07; tin, 0.01, and from nil to a trace of chromium, nickel and copper. All of the alloys used were melted in open-hearth furnaces, except where otherwise noted, and were hot-rolled to 0.100-in. plate. Samples approximately 1/2 in. square were then cut from these materials. So that the surface conditions of the samples used for oxidation would be standardized, each sample was ground through 000 emery paper immediately before oxidation. Two different techniques were employed in carrying out the oxidizing treatments. One consisted simply of heating the samples with free access to air. In this treatment the samples were set on edge on a refrac-

Jan 1, 1945

By A. U. Seybolt

Experiments on both suljidation and hot corrosion have been carried out using ternary Ni-Cr-X alloys and commercial nickel-base superalloys. It has been shown that lhere are certain micro structural similarities between sulfidation using H,S/H2 mixtures and hot corvosion using Na,S04 in "crucible" experiments or hot corrosion tests using a flame tunnel apparatus. It is proposed that two key processes in the hot cowosion process are: 1) formation of chromium sulfides which deplete the alloy matrix, and 2) oxidation which can be accelerated because of chromium depletion. Other processes play an important role in the hot corrosion process, such as accelerated oxidation attack due to the presence of a N& S04 or N&SO,- NaC2 film which inhibits the formation of a protective external oxide scale. However, this latter phenomenon was not studied in this work. THE term hot corrosion has come to mean a combination of sulfur and oxygen attack on nickel-base or cobalt-base superalloys used as gas turbine blades or partitions. This attack can be initiated by any combustion process in air involving fuel containing sulfur if the sulfur level is sufficiently high. Levels of 5 pet SO2l for example, in the combusting gas have been observed to produce hot corrosion attack on nickel-base alloys. The important immediate corroding medium in aircraft gas turbines, however, has been established to be Na2S04, formed from reaction between NaCl from sea air and sulfur in the fuel.' The Na2S04 concentrates the sulfur sufficiently so that superalloy parts heated in the range 1400" to 1900°F can become sulfided by reducing the Na2S04 film which forms on the parts, and this reaction allows sulfur to gain access to the alloy. The sulfur thus released diffuses into the superalloy and forms primarily chromium sulfides of various compositions, but frequently Cr2S, has been identified. Figs. 1 and 2 show the morphology typical of hot corrosion of a cobalt-base superalloy X-45 (25 Cr, 10 Ni, 7.5 W, 0.25 C) and a nickel-base alloy, Udimet 500 (19 Cr, 19 Co, 4 Mo, 3 Ti, 2.9 Al, 0.07 C). Both alloy samples were subjected to the same hot corrosion conditions: 616 hr at 1600°F in a combusted 2.9 pct S distillate oil containing 125 ppm Na as NaC1. It will be noted at once that the nickel-base alloy is much more severely attacked. The depth of corrosion is much greater and the number and size of the sulfides present are much greater. Both alloys show a duplex oxide scale, which is more noticeable in the X-45 alloy. The external scale is probably a spinel in both cases, with CrQ3 lying next to the alloy. Many investigators1 -"ve been concerned with hot corrosion phenomena, but there has been a lack of unanimity of opinion as to the details of the hot corrosion mechanism. More than one definition of hot corrosion is possible. Some investigators con- sider as a measure of hot corrosion only the weight gain due to an accelerated oxidation. However another point of view is that the total depth of affected alloy may be used as a measure. While it is recognized that surface oxidation attack is greatly accelerated by the presence of salts like Na2S04 or Na2S04-NaC1 mixtures, sulfur penetration into the alloy also undoubtedly produces very important effects. The region of sul-fide penetration which is so prominent in Fig. 2 is one of the outstanding characteristics of hot corrosion. For highly stressed parts, such as first-stage buckets, this sulfur-penetrated region can be more significant in mechanical property loss than the reduction of cross section produced by the formation of the massive external scale. In addition, evidence will be presented that this sulfided region can be less resistant to subsequent oxidation attack. Since it appears that the sulfided region below the surface oxide scale plays an important role in the overall corrosion process,

Jan 1, 1969

By T. Watanabe, S. Karashima, H. Oikawa

Creep tests of a! iron and its solid-solution Fe-Mo, Fe-Co, and Fe-Si alloys with bcc structure were conducted under constant stresses in ferromagnetic and paramagnetic temperature regions above 0.5T,(T, is the absolute melting temperature). It was found their high-temperature creep behavior changed in the vicinity of the magnetic transformation temperature, that is Curie temperature, TC. In the ferromagnetic region below the steady-state creep rates were lower than those expected from the extrapolation of the data in the paramagnetic region, the amount of decrease being affected by solute addition. Also, activation energies for steady-state creep were different in the two temperature regions. The observed changes were concluded to be due to the effect of ferromagnetism on diffusion. It is well-known that plastic deformation of metals and alloys in the temperature region where mobility of atoms becomes high enough is controlled by atomic diffusion." Many experimental results394 on fcc and hcp materials have been reported to confirm this view. In bcc metals and alloys, not much basic investigation of creep deformation has been performed. In particular, experimental work on iron5-&apos; and its alloys, covering a quite wide temperature range is extremely scarce. On the other hand, the effect of ferromagnetism on diffusion has recently been demonstrated in a iron and its alloys;&apos; it has been made clear that diffusion rates in ferromagnetic temperatur~e region are significantly lower than those expected from diffusion measurement in the paramagnetic region. Therefore, it is concluded that the magnetic effect influences the high-temperature creep behavior in a! iron and in its alloys. The present authors have conducted creep experiments on a iron and its solid-solution alloys over a very wide temperature range, and have demonstrated the magnetic effect. A part of the result has already been reported elsewhere.26 In this paper, the experimental results will be described in detail. While the manuscript was in preparation, a similar magnetic effect on creep deformation of a iron was reported by Ishida . Though their experiments covered an extremely wide temperature range, the creep stresses varied from several thousand psi to several ten thousand psi with decreasing temperature. Consequently, it may be said that there remain some questions concerning their results. I) EXPERIMENTAL PROCEDURE The materials used in the experiments were pure iron and its alloys; they were prepared by vacuum melting (10"" mm Hg) electrolytic iron (99.9 pct), molybdenum powder (99.9 pct), ultrapure silicon, and cobalt pellet (99.5 pct) in alumina crucibles. The ingots were hot-forged to plates 10 mm thick and 50 mm wide, and then were hot-rolled at about 700°C into sheets 1 mm thick. Creep specimens, 5 mm in width and 15 mm in gage length, were machined from the sheets. They were annealed at temperatures which were well above their respective recrystallization temperatures. The chemical compositions of the metal and alloys are shown in Table I together with their heat treatments. High-temperature creep tests by the use of a lever-type creep testing machine were carried out in argon atmosphere under constant tensile stress. In order to keep &eep stress constant within about *0.5 pct, stress change due to specimen elongation was compensated by tensile force of a stainless-steel bellows which was inserted between the loading lever and lower specimen grip with the assumptions of a linear relationship between change in cross section and strain and uniform strain along the section. Beyond the limit of compensation by the bellows, small amounts of load were removed after appropriate strains. The testing temperatures were maintained to within i2"C of the reported values. Creep deformation was auto-graphically recorded at the upper (moving) specimen grip using a linear differential transformer which was held by a stainless-steel rod mechanically connected to the lower specimen grip. It was also directly measured with a dial-gage reading to -& mm. 11) EXPERIMENTAL RESULTS AND DISCUSSION 1) Creep Curves of a Iron and Its Alloys. Creep curves of a! iron, Fe-Si, Fe-Co, and Fe-Mo (<2 at. pct Mo) alloys usually consisted of three stages, that is transient (primary), steady-state (secondary), and accelerating (tertiary) stages. An example is illustrated in Fig. 1 for a! iron. However, in Fe-Mo alloys with more than 2 at. pct Mo, an inverse transient creepZ8 was observed as indicated in Fig. 2. The inverse behavior, which varied with the amount of molybdenum, may be due to the substructure* in the annealed specimen as was sug-

Jan 1, 1969

By John Birkinbine

The following data, collected during a visit to the Snake river district, in Idaho, arc offered as indicating the possible utilization of a water-fall for irrigation by pumping, the working of gold-placers, the generation of electricity for light and power, and possibly for manufacturing purposes. For irriga-

Jan 1, 1901

Jan 1, 1969