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By Xue Yang

Even though many approaches have been proposed for automated fault detection and diagnosis of Heating Ventilation and Air Conditioning (HVAC) systems, and advanced maintenance programs, such as preventive and predictive maintenance have been applied for the systems, issuing work orders for corrective maintenance is still a reality. Currently corrective maintenance still accounts for more than 55% of all maintenance programs in average facilities in the US (DoE, 2010). Indoor air related problems are especially important among corrective maintenance work orders. This paper provides details of a case study conducted to capture the workflow that HVAC mechanics follow, their rationale in diagnosis process and the information they typically refer to while responding to indoor air related corrective maintenance work orders. The general workflow for HVAC mechanics to complete such types of work orders was summarized into 5 stages, and generic information requirements recorded from the case study were synthesized. Initial findings show two main challenges in the industry for HVAC mechanics to get access to required information, which highlights the need for a systematic approach that would enable identification of such information applicable to a given context under which a work order has been generated and provide values of required information for HVAC mechanics to do sound diagnosis through integrated data repositories.

Aug 1, 2013

By Silvando Vieira dos Santos

O emprego de trabalho mecânico em ligas metálicas associado a aplicações de tratamentos térmicos estão entre os principais métodos para se conseguir alcançar aumento de resistência mecânica e manutenção de boa ductilidade. Este estudo busca avaliar a correlação entre deformação a frio, tratamento térmico, microestrutura e propriedades mecânicas da liga Ti35Nb2,5Sn. Para isso realizou-se laminação a frio empregando níveis de redução equivalentes a 70%, 80% e 90%. Em seguida, as amostras foram analisadas por meio das técnicas de microscopia ótica, difração de raios X e microdureza Vickers. Na sequência, tratamentos térmicos de envelhecimento foram aplicados em diferentes tempos para cada nível de deformação e os mesmos parâmetros foram avaliados. Observou-se significativo aumento de dureza após etapa de envelhecimento e as análises por metalografia e difração de raios X evidenciaram a presença de fases metaestáveis na matriz beta..

Oct 30, 2017

By Larissa Koroznikova, Steve Durkin, Bradley Drake, Michael Tuck

This paper presents the results from the investigation of the application of thermal fragmentation in Australian hard rock underground narrow-vein mining. Two geologically similar samples from an underground narrow-vein hard rock gold mine were collected to obtain a measure of the technology’s ability to recover ore by the creation of large thermal openings to assess the applicability of the thermal method. Particle size distribution showed a higher generation of fine product, − 2 mm, by thermal fragmentation compared with selective blasting by 31%. The Bond work index for thermal ore (12.62 kWh/t) is half to that of the blasted ore value (25.32 kWh/t). The average grindability obtained for the thermal ore sample was greater than the blasted sample by a factor of 2.44, a higher value indicating a decrease in the energy required to grind. The thermal fragmentation method generates product with higher dissolution of gold in cyanide, by 14% for the − 9.5 + 2 mm size fraction samples. Additionally, the thermal fragmentation results in higher production of − 9.5 + 2 mm material by 15 % compared with selective blasting.

In the past two and a half years, over 40 000 metalliferous mining and related services personnel have been trained through an Australian Generic Safety Induction system. This is almost half of AustraliaÆs metalliferous mining related workforce. This remarkable industry acceptance and delivery of safety courses is supported by Acacia Resources, Great Central Mines, Homestake, Newcrest Mining and WMC Resources, amongst hundreds of other mining, exploration and major contracting and services companies. MARCSTA; the Mining and Resources Contractors Safety Training Association (a pro-active not-for-profit self-help group of 24 major contracting companies) developed this generic safety induction. MARCSTA set out to find the æcommon groundÆ necessary to help address the evident safety problems and cost of re-training that were plaguing development of an internationally competitive and productive export industry. The incredible expansion of Australian mining during the decade fuelled a need for out-sourcing, resulting in much larger numbers of contractors on-site. At the same time, changes within Australian legislation, community expectations and the development of huge fly-in/fly-out operations and widespread skills shortages led to a rapid labour turnover and a higher paid workforce. Many Australian mining houses also ran international operations, particularly in South East Asia and head hunted people across the world. The skill levels fluctuated and fell at some local operations. Employers could no longer rely on systematic in-house training of permanent employees to improve safety and productivity as workers could and often did move on. Serious discrepancies in both quality and quantity of safety induction training and work practices occurred. Repetitive, boring and ineffective safety training became an embarrassing and costly burden for companies and workers alike. Then a spate of mining deaths sparked highly publicity, workforce concern and a demand for improvement from government, unions and corporate stakeholders. MARCSTA recognised it had to develop a high-quality safety-training program to satisfy the needs of all employers and be acceptable to others within the industry. This induction system had to be flexible enough to meet differences in legislation between states and industry sectors and be portable to enable cost and time savings for the new transient workforce. Changes in the last two years as a result of evaluating and incorporating various Taskforce inquiries into underground mining fatalities later led to the development of the MARCSTA Underground Safety Induction. This logical development added to the run away success of MARCSTAÆs General Safety Induction and was seen to be essential for many surface mines that were planning to develop underground operations. There are many lessons that MARCSTA learnt during its development that Pacific and South East Asian mining operations can benefit from. The most important of these are the support of stakeholders within industry and the recognition of higher safety and health expectations from workers and government. This goes hand-in-hand with the productivity and return on investment expectations of companies and their shareholders.

Jan 1, 1999

By Leo F. Reinartz

Part II of a four-part series on the history of steelmaking in the US, points out the inadequate safety and living conditions that existed in steel mills at the turn of the Century. Also defined are furnace and process developments. OPERATIONS in steel plants today are highly mechanized. Men work in light, clean, orderly melting shops, making it difficult for old timers to convince young men that primitive, hazardous conditions existed in steel plants at the turn of the century. Working conditions then were very poor as compared to present day standards. In small plants especially, sanitary, locker, and washroom facilities, first-aid practices and stations were un- known Accidents were frequent and severe. Workers had a fatalistic attitude toward getting hurt. He who had an accident was looked upon as a hero. A dirty bandanna often served as a bandage. Infections were frequent. Electric cranes were in their infancy and broke down often Cables had not as yet replaced chains. Pig iron and scrap iron were loaded by hand in the stockyard, and stockyard locomotives were un- known; mules served as the usual motive power. It was not unusual to see recorded a delay of ½ hr in charging a furnace because of a balky mule. Furnace operations A few plants had primitive charging machines, but most furnaces were charged by placing scrap or pig iron on the paddle of a long peel, which rested on a bar across the furnace door opening. Laborers at the handle end of the peel, using the bar as a fulcrum, would heave the material into the furnace by a down and sideward motion of the peel handle. In time they became expert in placing these materials in the furnace, but it was hard, hot work, and a long time was required for charging. Cold charges of 25 tons required more than 12 hr for melting and re- fining the steel. Ports, doors, and frames were not water cooled. The charging and working area in front of the furnace was covered with steel plates. They were hot and often warped by the intense heat of the un- insulated checker chambers directly below. In the summer, working conditions on the charging floor were almost unbearable. Silica refractories were of poor quality. Because of this, and the inadequate training of furnace men in fuel control and furnace operations, roofs, front and back walls, and ends burned out rapidly. Dolomite machines were unknown; consequently, furnace banks and hearths were fettled with dolomite by the use of hand shovels. The round system required six or more men. Each man took a shovelful of dolomite and, in his turn, deposited it on the back wall and bank by a dexterous forward swing and twist of the shovel. The upward swing of the shovel partially protected his face from the searing heat of the furnace coming out through the wide-open door. Considerable skill and stamina were required to do this job properly. Reverse valves, usually of the cast-iron butterfly type, were located below the charging floor. They were operated by long levers on the charging floor level men they became warped, because of heat and abuse, great strength and skill were required to reverse them. Furnace operations were difficult. The quality and quantity of producer gas coming from irregularly stoked, hand-operated gas producers was uncertain and unreliable. Furnace Linings and ports were quickly burned out. Poor bottom and side-wall refractories, indifferent and inexperienced crews, as well as irregular re-

Jan 1, 1961

By J. R. Bradfield

THOSE familiar with the development of the Horne mine can readily appreciate that more and more accommodation bas been required for underground labour as the mine has grown. A permanent fire-proof change house, 30ft. by 75 ft., was built in 1927 to accommodate 194 men. This was extended ro 30 ft. by 92 ft. in 1928 to accommodate 296 men, and to 30ft. by 110 ft. in 1930 to accommodate 398 men. By 1933 this building was again overcrowded and tentative plans for a new change house were drawn up. However, it was realized that future operations would be centred around No. 4 shaft and a proposed new shaft, and the decision as to the location of the new change house had to be deferred until the area which seemed most suitable for the new shaft had been thoroughly explored underground. In the spring of 1934, the basic idea was accepted of drying the wet clothes in open mesh compartments or baskets located between rows of standard steel street-clothes lockers and built so that the covers or lids would serve as seats or benches.

Jan 1, 1935

By T. H. Adair

"IntroductionCONTINUOUS casting of ferrous and non-ferrous metals is not a new innovation. Patents describing machines for continuous casting are on file as far back as the year 1842. In the middle of the last century, Sir Henry Bessemer conceived and built a continuous casting• machine for the production of mild steel sheet.The production of billets and slabs of both non-ferrous and ferrous metals is being carried out by the continuous method on a fairly large scale on this continent and abroad. At present, the volume of production of •copper and aluminum and their alloys in billet and slab form is much greater than the continuous casting of steel products. The new installation of a continuous casting unit at Atlas Steels, Limited, is designed primarily for the casting of alloy steel billets and slabs.As an introduction to the art of continuous .casting of metals, it is interesting to examine a few of the many devices which have been developed. As previously mentioned, Sir Henry Bessemer constructed a machine for the direct casting of mild steel sheet. His discoveries and ideas of continuously casting steel formed the foundation for the work of other pioneers in this field, all of whom have contributed to the improvement of this art through the ensuing years. The machines which will be selected for examination are those of Bessemer, Poland-Lindner, Williams, Ennor, and Junghans. The last unit to be discussed will be a modification of the Junghans machine recently installed at Atlas Steels."

Jan 1, 1954

By D. Georgiou

Direct sulphuric acid leaching of nickeliferous limonites is the process of choice to recover nickel and cobalt from equatorially located lateritic ores. These ores are rich-in-iron (-45 wt%) existing in the form of goethite enriched with nickel. The merit of this process is due to its high nickel selectivity because of simultaneous iron separation and acid regeneration. Under acid leaching conditions (-250 to 270°C) iron follows an acid dissolution-hydrolytic precipitation path yielding a very low concentration level depending on temperature and acidity of the final leach liquor. The primary precipitation product of iron is hematite which also forms as a scale on reactor internals along with co-existing aluminum. In this paper, an overview of the behaviour of iron solid products under process conditions is made. The evolution of goethite to hematite transformation, as well as the role of iron in reactor scale production, are studied using SEM/EDX characterization techniques.

Jan 1, 1995

By Yong Li, Tao Jiang, Xiangxin Xue, He Yang

"In this paper, we describe the current status and research progress on the utilization of typical industrial solid wastes in China. We propose a creative method called “eco-utilizing wastes” with an aim of both integration and increment but without second-time waste and pollution, in terms of the characteristics of typical industrial solid wastes, such as titanium-bearing blast furnace slag, high-silicon iron tailing and boron-enriched slag as well as oil shale.Situation of Typical Industrial Solid Wastes in ChinaThough mineral resources in China are abundant, most of these are low grade ores. Moreover, the distribution of mineral resources is asymmetric, which causes the increase of cost and decrease of the economic benefit. Over-exploitation of mineral resources results in a large number of solid wastes. The accumulation of solid wastes not only means the waste of valuable resources, but also causes environment deterioration. There exist some problems in the current practice of the disposal of industrial solid waste, such as only emphasizing the final results and causing new pollution and waste [1]. So the research and development of a high value-added method has a high practical relevance to our nation. Based on the present status and research progress of industrial solid wastes in China, a creative new idea and method for eco-utilization of solid wastes is proposed in this paper."

Jan 1, 2012

By R. A. Beall

As part of an ongoing program to develop high-quality materials with improved performance and service lives, and to conserve critical minerals, Bureau of Mines, U.S. Department of the Interior, researchers studied the process of hot-rolling metals, alloys, and composites in vacuum. First, a comprehensive review of the literature is presented, including the advantages and disadvantages of using vacuum. Next, details of hot-rolling titanium, chromium, and molybdenum-iron bimetal are given. Finally, the design of new equipment is described. At this time, it is uncertain whether hot-rolling metals in vacuum will gain commercial acceptance in the future.

Jan 1, 1979

By Wang Jia, Chai Li-yuan, Zhang Jin-Long, Peng Bing, Zhang Qiang

"Electrolytic manganese dioxide (EMD) residue was mixed with shale and fly ash as the main materials to make solidification/sintering brick for the utilization of the residue from EMD production. The effects of sintering temperature, sintering time, solid waste content and cooling process on its mechanical properties and toxic elements solidification were investigated according to compressive strength and leaching toxicity. The results showed that the calcined residue had capability of solidifying toxic metals and exhibited perfect strength after treated in the optimal parameters of EMD residue below 50%, temperature at 1000-1100°C, time3-5h, and semi-quenched at 600°C1 InstructionSolid clay-brick holds the leading position among building materials for a very long time in China. The traditional technique of making clay-brick has the drawbacks of backward process, simple facilities and single product. Since Chinese Reform and Opening-up, urban-rural construction and real estate have been booming with the rapidly development of national economy and science technology. The problems of ruining fertile land, environment contamination and high energy consumption in the traditional technique of clay-brick making have not been solved yet. On the other hand, more than 7 billion tons of industrial wastes are accumulated over years which occupies over 6.7 million hectares filed and causes serious environmental problems[1-31. Strategy present in ""The Chinese Agenda of the 21st Century"" required the production of wall materials less energy conservation, land saving and waste recycling.Coal gangue[4-9l, fly ash[I0- 13l, sludge from waste water treatment and tailings of gypsum, pyrite, copper mine, high silicon containing iron, asbestos and ects [l4-lSJ are the solid wastes used for brick making around the world. There are two kinds of process for brick making, high temperature sintering and low temperature steam curing[19•201. Although the technology of two brick making made great progress and got widely application in construction field, no precedent for preparing sintering-bricks with EMD residue as materials occurred in China because of its complicated processing technics and lack of sufficient practical experience to guarantee the bricks' quality.In this study, EMD residue was mixed with shale and fly ash as the main materials to make solidification/sintering brick. The effects of sintering temperature, sintering time, solid waste content and cooling process on its mechanical properties and toxic elements solidification were investigated according to compressive strength and leaching toxicity."

Jan 1, 2011

By A. E. Jack Swanson, Brian P. Micke

INTRODUCTION Nevada Goldfields began underground mining development at the Kingston Project in September, 1986, followed by mill start-up in March, 1987. The first gold pour in April followed three years of preparatory work in establishing a North American operational base for the production of precious metals by Golconda Minerals N.L., an Australian mining firm. GENERAL CORPORATE BACKGROUND The Golconda Group of companies was established in early 1983 in Australia. It began operations by successfully retreating tailings at several old gold mining sites throughout Australia. With the limited reserves available for tailings retreatment, Golconda began to look toward the future by conducting a gold exploration program in Australia. However, the continued high price of gold in Australia had limited the possibilities of acquiring good properties at a reasonable cost and consideration was given to looking outside Australia in addition to Golconda's domestic exploration activities. North America was favored because of the proven potential for substantial gold deposits, the established infrastructure which would allow for rapid and cost-effective development of new projects and the advantages of similar political and economic climates. In mid-1984, Golconda established an office in California and began an extensive study of over 100 prospects throughout the United States. Two prospects were identified as a result of this study whch showed merit; one was located at Empire, Colorado and the other at Aurora, Nevada. Negotiations were then successfully undertaken to acquire these two properties. Golconda's U.S. offices were moved to Reno, Nevada in early 1985 to facilitate management of its projects. To operate and manage these projects, a small Canadian company listed on the Vancouver Stock Exchange, Cannon Minerals, was acquired by Golconda and renamed Nevada Goldfields Corporation. The current structure of the company is shown below in Figure 1. A private placement of 2,575,000 shares of common stock at US54.00 per share was arranged by Jacksons Limited of Australia in association with W.I. Carr (U.K.) Limited of London. This placement resulted in US510.3 million being available in May, 1986 for the acquisition and initial development of the Aurora and Empire projects. While the financing was underway, project planning commenced on both the Aurora and Empire projects. The Aurora project was selected as the one to be initially developed because of its relatively advanced stage of development. The

Jan 1, 1987

By L. Yuan, C. Brown, N. Rayyan, J. Soles, T. H. Dubaniewicz

As lithium-ion batteries (LIBs) become more prevalent in the mining industry, new hazards of battery fire and explosion are emerging. Efforts must be taken to ensure that workers are safe from these new hazards, such as batteries undergoing thermal runaway in underground areas that may have explosive methane-air mixtures. Researchers at the National Institute for Occupational Safety and Health (NIOSH) investigated overpressures generated within a sealed battery enclosure filled with an explosive methane-air mixture and a single cell lithium-ion battery driven into thermal runaway using an accelerating rate calorimeter (ARC). For both iron phosphate (LFP) and nickel manganese cobalt (NMC) lithium-ion cells, the explosion overpressures remained unchanged with varying percentages of methane concentration in the atmosphere surrounding the cell. It’s likely that the gases released from the battery undergoing thermal runaway caused an inert atmosphere within the sealed canister. The results from this study will help mining equipment manufacturers develop proper measures to keep miners safe while working with lithium-ion batteries in underground gassy mines

Mar 2, 2022

By H. A. F. de Souza, Dana S. Mills, P. E. Burgener

"ICP-MS has moved from a laboratory curiosity to a functional analytical tool. This paper discusses how ICP-MS has been used to solve difficult analytical problems encountered when analyzing various mine materials. Comparisons between analytical techniques applied to the analysis of gold and the platinum group metals illustrate the advantages and problems of ICPMS when. applied to trace levels of some metals iri the presence of ore grade metals. Interferences and matrix effects are compared to ICP, AA and Neutron Activation. The necessity to select chemical extractions which are compatible with ICP-MS are also discussed.The ICP-MS techniques explained in the examples on Au and precious group elements (PGE) have validity in analytical problems encountered in testing of trace metals in the presence of major elements found in mine materials. Exploration and environmental testing are other areas that require the same analytical approach to quantify trace levels in the presence of major interfering elements normally associated with mining environments."

Jan 1, 1999

By F. W. Jessen, James N. Howell

INTRODUCTION The determination of cloud points has to date been limited to rather transparent oils, visual observation of the formation of a solid phase being the criterion for the standard ASTM D 97-47 method. The need for a quiclc and simple method for determining cloud points under dynamic conditions for opaque crude oils became necessary in a study of fundamental aspects of paraffin deposition from crude oils. PREVIOUS WORK The determination of cloud points in opaque oils by viscosity temperature curves is fairly new, Young' described a method employing the capillary tube principle. No information exists relative to the determination of cloud points of crude or refined oils under dynamic conditions. Shock' noticed that deposition of paraffin from crude oils took place at temperatures at or below the temperature at which a sharp inflection point occurred in the viscosity-temperature curve. This observation indicates a possible correlation between this temperature and the cloud point of the crude oil. Reistle and Vietti1 have reported that when crude oils containing small amounts of asphaltic materials were heated to temperatures sufficiently high to solubilize these materials and immediately cooled the pour point of the crude oil was lowered as much as 70°F. Sachanen\ asribes this effect to the action of colloidal asphaltenes in preventing the formation of the crystalline structure necessary to maintain the oil in a rigid state. At high temperatures, asphaltenes are peptized, and the paraffin crystals formed at these temperatures adsorb the colloidal asphaltenes on their surface thereby hindering further growth of the crystals. Reistle" found, however, that such heating and cooling of crude oils had no effect upon the cloud points. This latter work dealt with a crude oil of fixed composition, and the question immediately arises as to the effect of varying the concentration of asphaltic materials on the cloud point. APPARATUS AND PROCEDURE All viscosity measurements were made with a Bendix Ultra-Viscoson. The Bendix Ultra-Viscoson, which consists of a vibrating probe and an electronic computer. measures viscosity by exciting a thin alloy steel blade on the end of a probe by short electrical pulses in damped oscillation at 28 kilocycles. The blade vibrates longitudinally with an amplilude of less than 55 micron or 20 millionths of an inch. Energy to protlucc this excitation is generated in he computer and transferred to the probe through the connecting cable. The oscillating blade is magnetostric-tive, i.e., it is capable of transforming electrical energy to mechanical energy in the ultrasonic range. Ultrasonic waves are produced in the material surrounding the blade by the oscillating motion of the blade causing layers of the material to slip back and forth over one another at a known frequency. The electronic computer calculates the energy required to produce the sliding motion which is in turn proportional to the viscosity of the material. Actual values of viscosity times density (centi-poise X grams/cc) are indicated on the computer and a continuous D-C signal is provided which is fed into a type 153 Electronic Recorder (manufactured by Brown Instruments Div. of Minneapolis-Honeywell Regulator Co.) The liquid sample container was fabricated from a Lucite cylinder and jacketed by a Luicite water bath. Early experiments using glass and steel sample containers were not satisfactory. since the Ultra-Viscoson was apparently affected by the alterzltion of the magnetic fields surrounding the probe by stresses set LIP in the glass and steel as it cooled. The procedure for determining viscosity-temperature curves was relatively simple. The temperature ot the sample was raised sufficiently high to solubilize all paraffin and asphalts present. After heating, the oil sample was immediately transferred

Jan 1, 1957

By Michael J. Friedel

The integrity of mine structures, such as the roofs, ribs, face and supporting pillars, is difficult to assess beyond the exposed surface. To mitigate potential rockfall hazards, the U.S. Bureau of Mines is assessing the usefulness of Rayleigh wave dispersion analysis to detect damage and stress-relieved zones in mine structures. Classical surface wave dispersion modeling is utilized at both laboratory and field scales in damaged and undamaged material to assess the integrity of a mine pillar and roof. To more fully exploit Rayleigh wave propagation characteristics, derivation of a novel dispersion parameter was conducted using a convolutional model. The development of a suitable Rayleigh wave dispersion system based on insight derived from forward modeling is presented. The application of inverse modeling for damage and stress assessment in the mine environment is also discussed.

Jan 1, 2010

By T. A. Sullivan

The use of sulfur combined with either sand or waste copper tailings was investigated by the Bureau of Mines as a substitute for a good graded aggregate in asphalt paving materials. The research was part of a utilization program to develop meaningful uses for a projected oversupply of sulfur. Many sections of the country lack good aggregate for paving but do have available sources of sands and sulfur. The development of paving mixtures of desert sands or tailings with sulfur and asphalt was accomplished in the laboratory and tested by laying small paving test sections. Three types of material were studied for use with the sulfur and asphalt. They were (1) a concrete sand similar in gradation to river or beach sands, (2) desert blow sand, and (3) waste copper tailings. Desert blow sand and waste copper tailings are much finer than concrete sand. Mix designs were established for the three types of materials, sulfur, and asphalt used in the paving materials. The best mix designs were as follows, in weight-percent: 80.5 concrete sand, 13.5 sulfur, and 6 asphalt; and 77 either blow sand or tailings, 17 sulfur, and 6 asphalt. Small-scale testing showed that these mixtures were suitable paving materials but would require specialized equipment for transporting and laying. The chemical modification of sulfur to obtain properties that would allow placement of these materials with normal asphalt paving equipment was studied. Results indicate that reacting sulfur with dicyclopentadiene before adding it to the paving mixture was effective in modifying the sand-sulfur-asphalt paving so it could be placed and rolled with conventional equipment.

Jan 1, 1975

By Owen Matthews

Introduction For the past year and a half, the mill of Cochenour Willans Gold Mines, Limited, McKenzie Island, Ontario has been roasting arsenopyrite-gold concentrates, prior to cyanidation, by means of a roaster employing techniques that are new and novel. The roaster is known as the Dorrco 'fluo-solids reactor', and the technique as 'fluidization'. The reactor has demonstrated its ability to roast a flotation concentrate containing arsenopyrite, pyrite, stibnite, small quantities of other sulphides, and some lime silicates and carbonates, yielding a calcine consisting mainly of porous iron oxide, plus the gold values. This calcine is readily amenable to cyanidation. Bulk shipments of concentrates to a distant custom smelter, as practised prior to this installation, has thus been eliminated, with appreciable savings in smelting charges, freight costs, and interest losses during shipment and smelting. This is the pioneer installation of fluo-solids roasting at a Canadian mill and up to the present performance results have not been published. It is the purpose of this paper to present the information now available for the benefit of other millmen who may be confronted with identical or similar problems to those encountered and solved at Cochenour Willans.

Jan 1, 1949

By C. W. Phillips, D. N. Frey

A commercial Ti-Fe-Cr alloy, Ti-150, exhibits a martensitic transformation on cooling and two nucleation and growth reactions, one above and one below the Mg-Mf region, on isothermal holding below the single-phase ß temperature range. The reactions were followed by metallographic, X-ray diffraction, and microhardness methods. THE rapidly expanding engineering application of titanium and its alloys makes increasingly urgent an adequate knowledge of the effect of heat treatment on this material. The work herein reported is an attempt to determine certain aspects of the behavior of a commercially available alloy, Ti-150, during heat treatment. The alloy, with a nominal composition of 2.7 pct Cr, 1.3 pct Fe, 0.25 pct 0, 0.02 pct N, and 0.02 pct C, was received in the as-rolled condition as a 3/4 in. round. Slugs 0.11 to 0.12 in. thick were cut under a coolant using a silicon carbide wheel. Preliminary work established that the alloy consists of two phases, a (hexagonal close-packed) and /3 (body-centered cubic), at temperatures below 1750" to 1775"F, and of only /3 phase at higher temperatures. The slugs were heated for 1 hr in air at 1800°F to form a single-phase /3 matrix, then transferred to molten tin (1250° to 1650°F) or lead (1150°F and below) for isothermal holding. Holding temperatures ranged from 700° to 1650°F, times from 0.001 to 23 hr. The treated slugs were then sectioned, one part for metallographic examination and diamond pyramid hardness, the other, after deep etching to remove the high oxygen surface,' for comparative lattice parameter determination and X-ray phase identification. Hardness measurements were taken on the lightly etched surfaces of the metallographic specimens; a 1000 g load on a 136° diamond pyramid was used. Five impressions on each sample were made and the average of the hardness calculated. The use of microhardness measurements to follow the course of an isothermal transformation reaction is undesirable because of the possibility of wide differences in microconstituent hardness.' They were used in this case, however, because of the small amount of material available. At the higher transformation temperatures, where the above-mentioned objection was apparent, the readings were proportioned to correspond to the estimated ratio of transformed and untransformed constituents present. At lower temperatures, resulting in much finer microconstituents, the microhardness measurements were more uniform. The standard deviation of the mean of five impressions calculated from these latter values was 4.2 DPH. Employing 2a limits (probability 0.95) the experimental error of the hardness measurements averages was 8.4 DPH. The etchant used was composed of one part glyc-erol and one part 48 pct hydrofluoric acid." Of a number of etches tried, this one appeared most satisfactory. All micrographs were taken at 500X magnification and with oblique lighting to permit easier identification of the acicular structure resulting from rapid cooling. No advantage was gained by using polarized light for metallographic examination. Phase identification and lattice parameter measurements were made with a North American Philips high angle spectrometer in conjunction with a recording potentiometer. Considerable difficulty was encountered with some of the lattice parameter measurements because of the extreme broadness of the few diffraction lines obtained from samples consisting mainly of strained, untempered, quenched structures.

Jan 1, 1953

By F. W. Luersson

High carbon, low phosphorus steel can now be made from pig iron containing 0.7 pct P or more, in a commercial sized open hearth furnace. No external heat is required for refining, and steel produced is identical with basic open hearth steel. THE classical Thomas process, which requires liquid pig iron containing over 11/2 pct P, yields a product relatively high in phosphorzs and nitrogen. Unless large quantities of recarburizers are added to the refined steel, the product is low in carbon content. Thus, the Thomas process is not well suited to American raw materials, and its product is often not acceptable according to the standards set by American industry. The shortcomings of the Thomas process have long been recognized; with the advent of low cost oxygen, studies were initiated to develop pneumatic processes which would conceivably overcome the inherent objections to Thomas steelmaking. Several such modified basic pneumatic processes have been tested experimentally in commercial trials during the past decade. Probably the most widely publicized of these developments has been the oxygen converter process as practiced in Austrial,2 and in Canada.8 n this process, oxygen is substituted for air and introduced above the liquid bath in order to increase the heat available to the metallurgical system. This avoids the need for high phosphorus raw materials and gives a product low in nitrogen. In this process, the phosphorus content in the final product depends, to a considerable extent, on the total amount of that element in the burden. The rotary furnace4 which is now in commercial operation at Domnarvet Steelworks, Sweden, is producing low phosphorus steel from iron containing 1.8 to 2 pct P. One or more early slags are removed and by this means high carbon steels of open hearth quality can be produced. At this stage of development there is some question as to the applicability of the rotary process to large heats. Another development has been the use of oxygen in combination with either steam6 or carbon dioxide yn the basic bessemer, thus avoiding the introduction of nitrogen gas into the refining system and giving a product relatively low in nitrogen content. A double slag process has been used in Europe7 in conjunction with a regular Thomas converter, by means of which it is possible to obtain a phosphorus content in the product approaching that obtained in basic open hearth steels. The Turbo-Hearth process:' which uses the side blowing principle so as to produce low nitrogen steel from normal American pig irons, has been developed experimentally in this country. A process fitted to U. S. raw materials All of the preceding processes, with the exception of the rotary furnace, suffer from the common shortcoming that they cannot be adapted to the production of high-carbon, low-phosphorus steels unless large proportions of recarburizers are added. In 1947, a program was initiated by the Inland Steel Company1' to study an oxygen steelmaking process specifically designed to utilize the full range of phosphorus analyses encountered in American pig irons and to give finai products with phosphorus and nitrogen contents comparable to steel produced by the basic open hearth process. Some of the objectives of the proposed process are: 1) the process should be able to accommodate molten pig iron conta;rl;rrg up to 1 pct P., 2) sne process should be subject to close control of carbon analysis, 3) the process should be capable of producing high carbon

Jan 1, 1958