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By G. A. Apell

The presence of considerable mineralization at the surface together with other favorable conditions suggested inclusion of the Nigger Jim diggings area in a comprehensive study of shallow lead deposits in southwestern Wisconsin. The area, which was the site of considerable shallow development some 60 to 70 years ago, offered the possibility of substantial quantities of lead at near-surface horizons. The investigation included completion of 30 churn-drill holes totaling 1,808 feet of drilling, 2 diamond-drill holes totaling 164.5 feet of drilling, and 25 feet of test pitting in two excavations. The degree of mineralization was determined in an area l,500 feet long and 150 to 300 feet wide along a mineralized trend that has not been investigated beyond the limits of the zone drilled by the Bureau of Mines.

Jan 1, 1948

By N. A. Rose, E. L. Spain

THIS study was undertaken primarily to determine the reasons for certain variations in the soundness of gravel aggregate taken from a number of widely separated points on the Tennessee River. Under laboratory tests, concrete made with these various aggregates in some cases exhibited marked differences in specific gravity crushing strength and durability. Gravel was studied in detail from Chattanooga to the mouth of the river and to a lesser extent from Chattanooga to Knoxville. The causes of variation were determined, and variational curves were constructed, which accurately predict the composition of aggregate at any point on the river and therefore its relative suitability for use in concrete. The aggregate at any point is suited for making sound concrete; the variance of suitability is due to varying percentages of sandstone and weathered material, which are less sound than other constituents. INTRODUCTION When it is stated that the aggregate from one point is inferior to that from another, it must not be construed to mean that the gravel is unfit for use. The classification upon which such aggregate ratings are based is largely arbitrary, thus inferiority or superiority is merely relative. Samples of gravel were selected from stockpiles at the dams of the Tennessee Valley Authority under construction, from the stockpiles of private companies along the river, and from samples taken by the gravel- exploration barge of the T. V. A. One hundred or more gravels of each size studied were selected at random by taking small handfulls while walking around the piles. These were separated according to the different mineral or rock constituents present, and the percentage of each constituent was obtained by counting. At least three such samples were taken from each size, and all checked with one another within a few per cent. The results were then averaged. In order to check on the accuracy of such sampling, a whole sample was taken from one point after the gravel was thoroughly mixed. The two methods gave approximately identical results. SOURCES AND TYPES OF MATERIALS The sources of gravel found in the Tennessee River are numerous and varied. The river itself traverses several geologic provinces, each

Jan 1, 1937

Provide means for rapidly re-establishing ventilation control in metal mines after blasting, for emergency applications, and for routine temporary use. Approach Two quickly-installed, parachute-like stoppings have been developed and tested by the Bureau's Pittsburgh Mining and Safety Research Center. How the Parachute Stopping Works The parachute stopping can be fastened to an existing anchor point, opened, and effectively block the air flow, in less than two minutes. Because the parachute stopping tends to be self-scaling, its performance is generally better than that of conventional fabric stopping. However, the periphery of the parachute stopping must be longer than the periphery of the mine opening, Figure 1 shows the parachute stopping deployed in a mine entry. To reduce leakage during routine use, the cloth at the periphery of the parachute stopping can be adjusted and then anchored at several points as necessary. This extra adjustment can also be done after the initial installation during mine rescue or mine recovery.

Jan 1, 1977

By S. S. Peng

Successful longwall mining requires a good roof control. A good roof control implies that: (1) no excessive pressure is build up in the face powered supports, and (2) chain pillars are designed in such a way that panel entries are well protected and interactions between adjacent panels are minimized. A clear understanding of strata behavior around longwall panels due to face movement is, therefore, the foremost requirement for achieving better roof control. This dissertation is designed to analyze the effects of strata behavior on longwall panels due to the mining activities. The following topics are studied: (1) the weighting, phenomena and their effects on front abutments, and (2) the chain pillar stability and pillar design under various roof conditions. Three dimensional finite element analysis was employed. The effect of parameters such as overburden depth, mechanical properties of the immediate roof and main roof, panel width, and size of chain pillar on (t) and (2) were analyzed. Four typical models were utilized to simulate various phases of panel extraction under various combinations of the above parameters; model one is to simulate the beginning of panel mining; model two is to simulate the situation that longwall face has passed more than half of panel length; model three is to simulate the completion of panel production; and model four is to simulate the second panel mining. The following formulae have been developed by applying multiple regression model to analyze the finite clement results: (1) a formula that classifies the type of root strata at the face area. (2) formulae that predict the first weighting and periodic weighting lengths. (3) a formula for design of the chain pillar size. Case studies were performed to check the validity of the formulae proposed. Comparison of the formulae proposed for the chain pillar design with other formulae were also performed.

Jan 1, 1984

By B. C. Allen, W. D. Kingery

Surface tension and its temperature dependence have been determined for pure liquid Fe, Cu, Co, Ni, and Sn and for Fe-C, Co-C, and Ni-C alloys. The temperature coefficient of surface tension is negative for all these liquids. The surface tension and wetting behavior of tin and tin-titanium alloys on A120,, Si,N,, MoSi,, and Sic, as well as the behavior of titanium-containing nickel alloys on A1 20, have been determined over a wide temperature range. For all the solids investigated titanium additims markedly lower the contact angle. Some limits for the solid-surface energies have been calculated from liquid surface tension and wetting behavior. SURFACE tension and interface energy are important variables in a number of metallurgical and ceramic phenomena, and have been discussed at some length in connection with determining micro-structure of polyphase systems,' solid-state sintering,' thermal etching of grain boundaries, heats of solution and fine powders,'1 grain-growth phenomena,' the mechanical behavior of fine foils and fibers, nucleation, soldering and brazing,' and other phenomenz of academic or practical interest However, until recently few quantitative data have been available for high-temperature systems. Among available data are some indicating positive temperature coefficients for the surface tension of liquid copper,*,11,'2 cast iron,l3 and iron-carbon14 alloys. Although carbon was found to be not surface active in iron at 1570" some preliminary studies had indicated the possibility of a positive temperature coefficient for the eutectic composition at lower temperatures.16 One part of the present study has been largely concerned with determining the temperature coefficient of surface tension for several metals at elevated temperatures, In addition to surface-tension studies, the wetting behavior of alloys containing titanium has been investigated over a wide temperature range. Previous measurements indicated that titanium was selectively adsorbed from nickel at a liquid nickel-solid alumina interface,17 and the use of titanium hydride or titanium-alloy techniques for metal-ceramic soldering is well known. In the present study, previous data have been extended to new alloy systems, and measurements have been carried out with other oxidation-resistant ceramics. EXPERIMENTAL The sessile-drop method was employed to measure liquid surface tension and contact angle between liquid and solid, utilizing apparatus and techniques which have been described previously.'g The shape of a sessile drop depends on equilibrium between forces of surface tension tending to form a spherical surface of minimum area and forces of gravity tending to flatten the drop. Typical sessile drops are shown in Fig. 1. From precise measurements of maximum drop diameter and drop height the surface tension and drop volume were calculated. Four solid materials were employed as supporting plaques for the liquid-metal drops. Aluminum oxide (99.9 pct, J, T. Baker, reagent grade) was pressed and sintered at 1800°C. Molybdenum-disilicide powder (99.0 pct, Electro Metallurgical Co.) was pressed and sintered at 1650°C. Plaques were cut from silicon carbide (99.4 pct, hot-pressed at Alfred University) and silicon nitride (95.1 pct, with Al, Fe, 0 as major impurities, Norton Co.) rods. All plaques were polished, cleaned, and dried prior to use. A number of metals and alloys were employed. Chemical analyses of vacuum-melted ingots of iron, nickel, cobalt (National Research Corp.), commercial nickel-base alloys, electrolytic copper (International Smelting and Refining Co.), and tin (Mal-linckrodt Chemical Works) are given in Table I. Alloys were prepared in the laboratory by vacuum melting the base metal with either titanium hydride (Metal Hydrides, Xnc.) or spectroscopic-grade carbon (National Carbon Corp.). Nickel-titanium alloys contained between 0.001 and 0.005 pct oxygen and the ferromagnetic metal-carbon alloys contained 0.001 pct. Cylindrical metal specimens (1 to 2.5 g) were machined and bevelled at the bottom to insure a uniform advancing contact angle on melting. Before use the samples were acid-etched, cleaned with acetone, and rinsed in petrol ether.

Jan 1, 1960

By J Chßvez, J Rosa del Castillo, J Rui

Environmental Impact Assessment (EIA) and Feasibility Studies (FS) were carried out to evaluate the potential use of treated acid mine drainage (AMD) occurring at the Kingsmill Tunnel in the Central Andes of Peru. The 11 km long tunnel drains the underground works of the Morococha Mining District and discharges about 1.25 m3/sec of AMD directly into the Yauli River in the Amazon Basin. The communities living downstream cannot use the Yauli River water due to its low pH and elevated concentrations of metals (eg Cu, Zn, Fe, Mn, As, Cd) and sulfate. Studies carried out for this project included technical feasibility, EIA, economic viability and social impact assessment phases. During the æTechnical FeasibilityÆ phase, the treated AMD was produced by simulating a high density sludge (HDS) lime neutralisation/ precipitation process and was evaluated for various potential uses. Mining companies located in Morococha, in particular Centromin Peru SA, and the Water Works Company of the City of Lima (Sedapal) collaborated with Golder Associates during the studies. The Canadian International Development Agency (CIDA) provided the financial assistance. The results of the physical, chemical, biological and toxicological analyses demonstrated that the AMD could be sufficiently treated to be potentially used to supplement the drinking water supply of Lima, and for agricultural (eg irrigation and livestock) and recreational purposes. Process design and scale-up parameters were also determined for implementation of the full-scale treatment facility at the site. The use of the treated AMD as a drinking water supplement would be economically feasible.

Jan 1, 2003

By Donald E. Zipperian

It has been recognized that froth flotation of mineral particles utilizing rising flow of micro size air bubbles, counter-current to quiescent falling flow of particles in a column type cell, provides a unique mechanical atmosphere conducive to extension of froth flotation process to much coarser and finer particles sizes than possible with mechanically agitated and aerated cells. 1,2,3,4. This paper describes metallurgical results obtained at several plant installations of large capacity commercial size Deister FLOTAIRE® Column Flotation Cells. These cells utilize air aspiration into surface tension lowered water to generate micro size bubbles. Operating costs, power, wear, and scaling characteristics of rougher, cleaner, and scavenger units are compared with mechanical units. Problems encountered and scale up criteria developed when increasing from 0.20m(8inch) diameter pilot cells to 2.42m(96inch) commercial cells are discussed.

Jan 1, 1985

By W. Jilowa, C. Nguni, M. Simukoko, C. Nampungwe

The upsurge in cobalt price and demand is propelled by high demand from the electronics and electric vehicle industry. Konkola Copper Mines has cobalt occurring with copper in the ratio 1:10 in ore. The ore is treated in the concentrator and recovered at the smelter as an alloy (Cu 70%, Co 4%–7%, 15% Fe). Subsequent processing of the cobalt alloy is challenging, with very few plants able to treat it, leading to marketing challenges. Konkola Copper Mines sought to improve the cobalt alloy by producing a slag that is easier to handle and process in subsequent processes. Cobalt alloy (3.60% Co, 85.4% Cu) was re-melted in a copper bath four times the mass of the alloy. Silica and lime were added for phase separation and fire refining commenced. Following completion of fire refining and after holding the temperature at 1200°C, cobalt-rich slag was skimmed and blister copper was cast into anodes for electrorefining

Jan 1, 2023

COMPLYING with your frequently expressed wish and, your persistent request, I have decided to prepare a brief little book on metallic ores, based on ,the books of the ancient philosophers and on the experience of practicing miners, that will instruct you how to judge from promising indications which rock forma¬tions, which veins, stringers, or mineral matter are likely to bring. forth metallic ores so that it would be promising and gainful to work them. It explains according to the best of my ability, in separate chapters, as much as you need to :know for your, chosen profession or business, about such things as the favorable characteristics of the terrain, the strike, and dip* and outcrop of veins in general, and also about each metal in particular. Young Knappius: † Then it will be explained to me logically in. this little book and I shall be given a reasonable understanding which mines can be worked gainfully so that my investment will not be wasted but will show a profit. Daniel: Everybody should, of course, use his intelligence and should educate himself well and diligently to become able to understand, [2]‡ as far as that is. possible, from what matter, by what means, and where metals are generated by. Nature; and as a mere side issue he should not spurn the profit that ensues there from. But if his aim is solely and predominantly profit and gain rather

Jan 1, 1949

By M L. van Kampen

The recent (2005) amendments to the Resource Management Act 1991 have made it clear that there is no obligation on an applicant to consult. However the importance and value in consulting with the community, particularly before commencing a major project, cannot be understated.   This paper looks at the provisions of the Resource Management Act as they relate to consultation and public participation in the process, and will discuss the benefits of consultation both before an application is filed and following the filing of the application. Engaging with the local community can help shape a project to better fit the community, engender support and address opposition. In short, taking the extra step to what is legally required, can help smooth what is potentially a bumpy road. Examples in practice of the value of consultation are given.

Jan 1, 2006

By C. H. Schwartz

A thermal radiation probe was constructed and tested in pulverized-coal-fired furnaces. A rotatable sensing head on the side of a water-cooled probe permitted measurement of radiant flux within a 7.20 cone from any desired direction to a point within a furnace. A response curve for a corner-fired furnace showed radiant flux of 130,000 Btu per sq ft per hr, when viewing flame, and 60,000 Btu per sq ft per hr, when sensing wall reflection. Detailed drawings and fabrication procedure are given.

Jan 1, 1970

By J Hartnett, B Tarrant, A Rayner, D O’Toole, P Davies

Since 2009, the Northern Territory and Australian governments have been working under a national partnership arrangement to inform a rehabilitation plan for the former Rum Jungle uranium mine. Part of the rehabilitation strategy is to backfill a flooded former pit (Pit), which extends down to 100m below the current pit lake surface and was historically partially backfilled with uranium tailings. It is proposed to utilise the remaining pit volume below water level to sub-aqueously store Potentially Acid Forming (PAF-I) waste rock which currently occupies large stockpiles across the site. The rehabilitation design and planning process undertaken to develop a strategy commensurate to project objectives and construction constraints involved the establishment of key constraints derived from the analysis of historic data sources and preliminary design efforts. Tabled strategies were balanced against dependent project tasks and project objectives, especially surrounding minimising disturbance of highly contaminated materials within the Pit. Ideas were developed in conjunction with industry input and review of case histories to develop a remediation solution that is constructible within the project timeframe and constraints.

Jul 1, 2021

By Yael Miron

ANFO blasting agents may undergo an exothermic reaction when they contact warm ore bodies that contain pyrite and its weathering products. The reaction is very fast at temperatures above 80° C. Urea, when present in sufficient amounts, inhibits this reaction at temperatures below 180° C. But urea-ammonium nitrate mixtures are very hygroscopic and, in certain climates, may be difficult to handle in the field. Reaction-inhibiting characteristics of three compounds were reported by the Bureau of Mines in 1979. Recently, the Bureau investigated the reaction-inhibiting qualities of five additional compounds. Mixtures of ANFO, pyrite, weathering product, and prospective inhibitors were slowly heated, under conditions simulating a hot borehole, to determine prospective inhibitor capability at temperatures up to ~175° C. Small-scale thermal tests of the same mixtures were used for verification and clarification of results. Two organic compounds, phthalimide and xanthine, similar in structure to urea, failed to inhibit the reaction. Zinc oxide and calcium carbonate were found inferior to urea, though zinc oxide raised the onset of reaction from 80° C to about 140° C. Only magnesium oxide was found to be similar to urea in its inhibitory ability at temperatures below 175° C. Based on results from analysis of quenched residues, the use of more than 5 wt-pct magnesium oxide is recommended.

Jan 1, 1982

By V. R. Garfias, R. V. Whetzel, J. W. Ristori

Since the entry of the United States into global war, virtually all data and information necessary for compiling figures on world petroleum consumption have become unavailable. This situation undoubtedly will continue until the world petroleum industry can return to a peacetime basis. During the past 10 years, the authors, by publishing annual estimates of .world consumption, have attempted to emphasize the importance of a yearly world-wide survey of petroleum supply and demand. It is beconling more and more evident that statistics for the United States alone can no longer give a comprehensive idea of the state of the petroleum industry, even within the United States itself. Therefore, when conditions in the industry again become normal, it is the hope of the authors that those bureaus equipped to do so will carry forward the study of petroleum supply and demand on a world-wide basis. Enough data and information are available, however, to attempt a rough estimate of world output of crude petroleum and petroleum substitutes for 1942, which to some extent may reflect the trend of world consumption. This estimate by countries, as compared with the output in 1941, is shown in Table I. The world production of crude petroleum and petroleum substitutes for 1942 is estimated at 2,208,000,000 bbl., or a decrease of 171,000,000 bbl. under 1941. Crude production is believed to have decreased by about 200,000,000 bbl., (about 9 per cent); while petroleum substitutes increased by 28,500,000 bbl., (nearly 20 per cent). The decline of crude output in the United States is estimated at 19,000,000 bb1.—less than 2 per cent; while that in foreign countries is estimated at 180,000,000 bbl., or more than 20 per cent. The marked decline abroad is due largely to losses in Venezuela and Colombia, where the lack of ocean transportation became the controlling factor, and in the East Indies and Burma, where military invasion brought about the destruction of the fields. The production of petroleum substitutes in 1942 apparently reached a new high figure of 7.5 per cent of the total world petroleum output. The important features of petroleum production outside of the United States are the changes that have taken place during the year in the supply of the Axis countries. In Japan the output for 1941 was estimated at 8,800,000 bbl., 5,500,000 of which were petroleum substitutes. It is believed that the output of synthetic oils during 1942 substantially increased, raising the total interior production of Japan to nearly 10,-ooo,ooo bbl. Also, during 1942 Japanese armed forces gained possession of oil fields having a normal peacetime output of about 78,000,000 bbl. per year. The production of these areas for 1942 is estimated at some 23,000,000 bbl., which indicates that Japan is now getting at least 33,000,000 bbl. a year, which exceeds by 8,000,000 bbl. Its

Jan 1, 1943

By J. W. Ristori, V. R. Garfias, R. V. Whetzel

Since the entry of the United States into global war, virtually all data and information necessary for compiling figures on world petroleum consumption have become unavailable. This situation undoubtedly will continue until the world petroleum industry can return to a peacetime basis. During the past 10 years, the authors, by publishing annual estimates of .world consumption, have attempted to emphasize the importance of a yearly world-wide survey of petroleum supply and demand. It is beconling more and more evident that statistics for the United States alone can no longer give a comprehensive idea of the state of the petroleum industry, even within the United States itself. Therefore, when conditions in the industry again become normal, it is the hope of the authors that those bureaus equipped to do so will carry forward the study of petroleum supply and demand on a world-wide basis. Enough data and information are available, however, to attempt a rough estimate of world output of crude petroleum and petroleum substitutes for 1942, which to some extent may reflect the trend of world consumption. This estimate by countries, as compared with the output in 1941, is shown in Table I. The world production of crude petroleum and petroleum substitutes for 1942 is estimated at 2,208,000,000 bbl., or a decrease of 171,000,000 bbl. under 1941. Crude production is believed to have decreased by about 200,000,000 bbl., (about 9 per cent); while petroleum substitutes increased by 28,500,000 bbl., (nearly 20 per cent). The decline of crude output in the United States is estimated at 19,000,000 bb1.—less than 2 per cent; while that in foreign countries is estimated at 180,000,000 bbl., or more than 20 per cent. The marked decline abroad is due largely to losses in Venezuela and Colombia, where the lack of ocean transportation became the controlling factor, and in the East Indies and Burma, where military invasion brought about the destruction of the fields. The production of petroleum substitutes in 1942 apparently reached a new high figure of 7.5 per cent of the total world petroleum output. The important features of petroleum production outside of the United States are the changes that have taken place during the year in the supply of the Axis countries. In Japan the output for 1941 was estimated at 8,800,000 bbl., 5,500,000 of which were petroleum substitutes. It is believed that the output of synthetic oils during 1942 substantially increased, raising the total interior production of Japan to nearly 10,-ooo,ooo bbl. Also, during 1942 Japanese armed forces gained possession of oil fields having a normal peacetime output of about 78,000,000 bbl. per year. The production of these areas for 1942 is estimated at some 23,000,000 bbl., which indicates that Japan is now getting at least 33,000,000 bbl. a year, which exceeds by 8,000,000 bbl. Its

Jan 1, 1943

By L. Hoffman, F. Seymour, S. Hoerger

Newmont has a large integrated operation in Northern Nevada with numerous mines, stockpiles, and processing facilities. There are over ninety defined metallurgical ore types and over sixty defined gold recovery process options. To take better advantage of the available synergies, a complete Nevada wide mine plan and process model along with a mixed Integer and Linear Programming optimization tool has been developed and implemented. This system is maintained and operated by a Nevada Planning Group. Standard in-house planning software tools and methods have been implemented at all mine sites. While increasing the effectiveness of planning in Nevada, these changes have allowed a significant reduction in overall Mine Engineering staff.

Jan 1, 1999

By R. I. Pennington, J. L. Vanderbeek

Investigations have been conducted at Chino Mines Co. into the effect that SAG mill recycle material (critical size) exerts on SAG mill throughput and specific energy requirements. Tests were conducted on laboratory, pilot, and plant scales to evaluate the merits of alternative treatment options. Removing critical size material from the SAG mill circuit has been shown to improve new feed rates by 84% with a reduction in specific energy (kWh./t) of 88%. Test results obtained to date are presented.

Jan 1, 1987

By F. D. Weeks

The Salida smelting plant, owned by the Ohio & Colorado Smelting & Refining Co., is situated at an altitude of 7,000 ft., about 2 miles west of Salida, Colo., and 215 miles southwest of Denver. Salida is a division point on the Denver & Rio Grande R. R. where the narrow-gage line serving the San Juan region joins the through standard gage. This narrow-gage road also serves the coal and coke companies at Crested Butte and the lime quarries and mines at Monarch and Garfield, which are only 20 miles distant. These facts, together with the possibility of an appropriate site, doubtless influenced the builders to locate at this point. The smelting plant and yard occupy 80 acres of land on the northeast side of the Arkansas River. The slope of the ground is such as to permit of the ore being delivered by cars at a point 25 ft. above the feed floor; and in front of the furnaces there is a fall of 50 ft. for the slag dump. A recent purchase of river bottom has provided slag room for 20 years. As originally constructed, the plant consisted of four blast furnaces, 40 by 144 in. at tuyéres, two copper-matting furnaces, dust chamber, stack, power plant, blowers, sampling works, and one railroad trestle about 16 ft. from bed floor to rails. Later 12 hand roasters of excellent design were added and the practice of smelting leady matte in a copper-matting furnace was abandoned. Since the plant passed under the present management the equipment has been increased so that the following is a brief description of the same at this date: Two lead blast furnaces, 48 by 180 in. at tuyéres, 17 ft. 6 in. tuyéres to feed floor; four lead blast furnaces, 40 by 144 in. at tuyéres, 17 ft. 6 in. tuyéree to feed floor; two copper-matting furnaces, not used; blast-furnace flue, 900 ft.; area 245 sq. ft.; blast-furnace stack, 150 ft.; above furnace floor, 190 ft. When smelting a 500-ton charge per day, the gases approximate 63,700 cu. ft. per minute and travel at a speed of 260 ft. per minute. The slag is hauled by a 10-ton electric locomotive; the slag shells and settler refuse are elevated to a bin on the feed floor by an electric hoist. The matte is tapped in 1,600-lb. cakes and loaded into cars

Jan 1, 1916

By J. A. Farinelli

In the Appalachian region of the United States, approximately 40% of the underground coal reserve base exists in seams 0.7 - 1.1m thick. These seams are, in general, often of premium quality and are frequently accessible through above-drainage drift-type openings. Unfortunately, there are no apparent advantages to mining thin seams, if quality is disregarded. The thin-seam mine is faced with the same legal and economic pressures as any other underground coal mine. But in addition to these common problems, thin-seam operations must also deal with the unique problems associated with mining at such a restrictive height. Small-scale, short-lived operations appear to be the most feasible means of mining these reserves. The purpose of this paper is to evaluate the production and safety potential of various thin-seam mining systems. Recommendations will be made regarding present and future thin-seam operations.

Jan 1, 1987

By M. M. Rao, P. G. Winchell

The growth rates of bainitic plates were measured at 400°C in Fe-Ni-C alloys containing 0.10 atom-fract~on nickel and 0.0012 to 0.0075 atonz-fraction carbon. The growth rates are adequately represented by where xc is nearly the atom fraction carbon of the bulk austenite and PXCy is nearly the carbon atom fractlon in the ferrlte of radiids p In equilibrium with austetzite. The form of the equation is that predicted by a model in which carbon diffusion in austernite controls the gvowth, but the numerical constatnt is two orders of magnitude below that suggested by the model. THE growth of bainitic plates in steel is often assumed to be controlled by the diffusion of carbon away from the advancing plate tip. This hypothesis predicts that the growth rate will increase as the carbon content of the austenite, xCz, is reduced toward the carbon content of the saturated ferrite comprising the plate tip, PxCY The growth rate should vary approximately as (xCg- pxCy)-1. Experimental observation of the growth behavior at low carbon levels should provide a significant test of this model. An alloying element in addition to carbon is required so that low-carbon austenite can be experimentally observed while undergoing bainitic transformation. Nickel was selected. The presence of nickel complicates the interpretation of the data in two ways: First, diffusion of nickel during the transformation would make analysis very difficult. Nickel is assumed immobile during the transformation. Second, nickel affects the solubility of carbon in ferrite and austenite in equilibrium. This effect has been evaluated.' At the completion of our experimental work Goode-now et al.2 published data in essential agreement with the observations to be reported here. Since their discussion is abbreviated and their data are scanty in the region of interest, we believe the present work is of significance. I) THE MODEL OF BAINITIC PLATE GROWTH The rate of lengthening of a plate is assumed to be controlled by the diffusion of carbon from the advancing ferrite-austenite interface into the surrounding austenite. The precipitation of carbides is assumed to be a secondary process. For ease of analysis the carbon-atom ratio,* pxCy, of austenite in equilibrium with ferrite which is convex with minimum curvature radius p, and the carbon-atom ratio, PxCY, of that ferrite in equilibrium with austenite are assumed independent of location on the ferrite-austenite interface. Since these carbon contents vary with the radius of curvature of the ferrite, p, their assumed positional independence must be held as an approximation. The consequences of these assumptions have been developed approximately by zener3 and Hillert,4 and the resulting equation for a platelet has been applied to bainite by Speich and cohen5 and Kaufman, Radcliffe, and Cohen.8 The Zener-Hillert equation* for plates is: The analysis of Hillert is supported by that of Hor-vay and cahn7 which involves no mathematical approximations but does include the assumption that the a/y interface coincides with an isoconcentration line. The solutions of Horvay and Cahn for elliptic paraboloids are replotted in Fig. 1. The shape of the paraboloid is expressed in terms of the ratio of the principal radii of curvature at its tip, A =p1/p2, which is also the ratio of the minor to the major axis of the elliptic cross section. The Zener-Hillert equation for plates is also plotted. The agreement is within a factor of two for (pxyaCr - xyC )/(xyC - PxCaY) between 0.5 and 100. This is the range of interest here and in most other work on bainite. The original form of the Zener-Hillert equation was the form given above with the right-hand side replaced by (pxCya -xCy)/(PxCya). This replacement is not appropriate here. 11) THE EXPERIMENTAL PROCEDURE Alloys were prepared and three kinds of experiments carried out. Continuous-cooling-transformation experiments were carried out on wires by measuring temperature and resistance during continuous cooling. Isothermal-transformation experiments were carried out on wires by measuring electrical resistance as a

Jan 1, 1968