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By T. S. Lovering

The use of geothermal energy is expanding very rapidly. This type of energy has proven commercially profitable for generation of electricity, for space heating, process heating, auxiliary heating of water in conventional steam power plants and for recovery of chemicals contained in natural hot water and steam. Two types of geothermal energy sources are recognized: 1) hot springs in regions of nearly normal heat flow that tap a deep reservoir through which water moves slowly to a hot springs conduit and then rapidly to the surface; 2) hyperthermal areas in which the water is heated by a relatively concentrated heat source related to volcanicity. If there is a geologic trap that provides a geologic analog to a steam boiler, as at Larderello, Italy, the hyperthermal area will have a convecting system that develops superheated water at relatively shallow depth and may provide natural steam in large quantities. If a hyperthermal area is to be productive for a long time, the underflow into the reservoir should be slow enough to allow the heat source and convective system to heat the underflow to the working temperature, and the production rate must not exceed this rate of underflow. A model based on a typical aquifer suggests that the rate of movement of water through the reservoir be such that a few years are spent in transit between isotherms that are spaced about 2°F apart. The possibility of finding blind geothermal areas is illustrated by discussion of the techniques developed in evaluating the subsurface temperatures in the East Tintic district of Utah where a map of isotherms at water level (2000 to 2000 ft below the surface) shows that a hyperthermal area may exist a short distance southeast of the mining district. Very nearly all of the energy that man currently uses comes ultimately from the sun's radiation. This includes water power, fuels such as wood, peat, coal and petroleum, the wind and all our animal power. In the paper summarizing a conference on solar energyl6 the average amount of solar energy received daily on the earth is taken at about 1 cal per m2 per min or slightly less than 2 pcal per cm2 per sec; this is almost exactly the amount of energy on the average that the earth liberates in regions of normal geothermal gradient due to its own internal heating. In many places, however, the energy released is many times the average and in some of these hyperthermal areas, geothermal steam is used for generation of electricity, and hot springs are used for heating buildings and private dwellings, process heating, auxiliary heating of water in conventional steam power plants, and chemicals may be recoverable from both hot water and steam. The use of hot springs waters for heating houses goes back hundreds of years but until recently was confined to a few dwellings close to the hot springs. In Korea, some houses had hot spring water channeled through conduits in the floor centuries ago and thus the Koreans can be credited with pioneer development of radiant heating. In Iceland at present nearly a third of the population uses natural thermal water for domestic heating." The Reykjavik system pipes hot spring water at about 94°C throughout the city and has devised insulated double pipes that allow the water to be piped for some 25 km with a drop of only 1°C for every 5 km. The actual cost to the Icelandic consumer is only one-third the cost of heating by imported coal and yet the industry is one of the most profitable in Iceland. The most profitable use of geothermal energy has been its conversion into electricity which can be transmitted economically much greater distances than hot water. The largest installation at the present time is that at Larderello, Italy, where the Count of Larderello began to experiment in the production of electricity from geothermal steam 60 years ago — in 1904. He installed his first steam turbine, with a capacity of only 250 kw, in 1912 as the result of a local quarrel with the power company which furnished the current required in the Larderello chemical industry - an industry that then dated back nearly a century. As experience was gained in drilling deep holes to tap geothermal steam and in converting it to electric power, the capacity of the installation of Larderello gradually increased, but was all destroyed by the Germans during their retreat from Italy in the closing

Jan 1, 1965

By Arthur Boynton

IN THE preparation of this paper the writer has been influenced by the fact that descriptions of various means of cleaning blast-furnace gas have been published and that further descriptive treatment of the subject will probably be less interesting than a statement of conclusions with regard to preferable methods which have been reached by him as a result, of experience and observation in this country and also as a result of somewhat detailed investigation of the subject made toward the end of the year 1927 on the Continent of Europe and particularly in. Germany. Owing to various circumstances, including a cost of fuel that is extremely high in relation to the wages of labor, the German iron and steel industry has accumulated experience in gas washing which is as yet in part lacking in the United States of America. The paper begins with a statement regarding the economics of the use of blast-furnace gas, then considers the principle's and practices employed in its purification. USES OF BLAST-FURNACE GAS For many reasons having to do with the utilization of coke-oven and blast-furnace gases in steel manufacture and with the use of hot metal, the blast furnace is now usually a part of a steel-producing unit, which also includes coke plant and rolling mill. Therefore both blast-furnace and coke-oven gas are usually applicable to any of the iron and steel-making processes, including the generation of power, and their allocation in any given works should be considered as a single problem. The uses to which blast-furnace gas, either alone or mixed with coke-oven gas may be put, include the following: Regenerative Heating of Air for the Blast Furnace.-This is the oldest and metallurgically the most important of all uses. It is universally performed with unmixed blast-furnace gas and under proper conditions should require not over 23.5 per cent. of the total gas generated for a blast temperature of 1350° F. For Steam-raising Purposes.-This is almost universally done with unmixed blast-furnace gas. From the standpoint of quantity used, it is at the present time the most important application in American steel-works practice.

Jan 1, 1928

By E. J. Whittenberger, F. N. Rhines

The formation of casting porosity is viewed as a nucleation and growth process with solidification shrinkage and gas precipitation as cooperative driving forces. Experimental evidence evaluating the individual contribution of each force confirms the major premise that microporosity is nucleated by gas precipitation. Additional data disclose the effects of the identity and quantity of gas, the temperature range of freezing, and the freezing rate upon the amount and distribution of porosity in light metal castings. POROSITY, as it commonly occurs in metal castings, has been ascribed to the contraction that accompanies the freezing of the metal, to the evolution of dissolved gases from the liquid during cooling and freezing, and, most frequently, to a combination of the two.'" "Pipe" formation is universally associated with solidification shrinkage; spherical "gas holes" are understood to be retained bubbles of gas; but the origin of microporosity, which usually exhibits an irregular or scalloped outline when viewed in cross-section, remains a subject of continuing debate.", ' The present research constitutes an endeavor to show what parts are played respectively by shrinkage and gas evolution in the initiation and growth of micropores and what factors determine their number, size, shape, and distribution. A preliminary outline of the mechanism of cavity formation in castings will serve to coordinate the experimental findings that will be reported and will at the same time provide a general theory of the origin of casting porosity. Basic to the mechanism of cavity formation that will be proposed are the following established facts: 1—that liquid metals and alloys contract gradually during cooling down to the freezing range, where a relatively large contraction, known as the "solidification shrinkage," takes place (exceptions in bismuth and gallium being noted);' 2—that the capacity of liquid metals and alloys for dissolving gases diminishes with cooling until, in the freezing interval, a large decrease takes place (various exceptions being noted and excluded from present consideration) ;.: and 3—that freezing proceeds counter to the direction of heat flow, the freezing front most commonly being composed of a system of tapering dendrite stalks and side arms which are coarser the lower the freezing rate and which protrude into the liquid for a distance that is greater the longer the freezing temperature interval of the alloy and the smaller the thermal gradient.' The mechanism by which voids are generated

Jan 1, 1953

The Annual Business Meeting of the members of The Rocky Mountain Coal Mining Institute held during the 83rd Regular Meeting of the Institute was called to order by the president, Bernard Bernstrom at 2:50 p.m. Tuesday, June 30, 1987 in the Janss Auditorium of the Snowmass Conference Center in Snowmass Village, Colorado. Thirty-one were present and a quorum was established. The president outlined the purpose of the meeting was to inform the members of the status of the affairs and activities of the corporation during the preceding year. It was moved by Leon Jeannot, seconded and carried to approve the minutes as published in the 1986 Proceedings. The chair called for reports of the various committees and these reports will by placed on file in the RMCMI Office. Bylaws and Resolutions. Chairman Loren V. Linville reported there were no bylaws revisions. He further reported that the Board had adopted three resolutions: (1) Noting the passing of members since the last convention-Benton Boyd, E. A. Hare, E. S. Moran, Jr. and Edward Prostel. (2) Of appreciation to the Executive Secretary, officers, chairman, Diamond Jubilee chairman and committees and convention committees for an outstanding job in preparing for the 83rd Regular Meeting of the Institute. (3) To recommend to all RMCMI members that, on an individual basis, they each oppose replacing coal fired generation with natural gas generation. Membership. Chairman Leon Jeannot reported that at the beginning of the 1986 fiscal year, there were 881 active or dues-paying members. During the year, 219 members were dropped for a variety of reasons such as non-payment of dues, transfer, employed elsewhere, change of address. Ninety-six new members have been recruited for an active total of 758. In addition there are 55 Life Members, 20 senior members, six scholarship winners and seven supporters for a net total of 846. The budget of RMCMI calls for 1,000 active members and we must address and plan for those short-term prospects as they will certainly impact our membership. A full report is on file in the RMCMI office. Patrons of the Institute. Chairman Ira McKeever reported that only 59 Patrons renewed their support during 1986-87. Program. Chairman Bill Balaz announced that the convention program theme "This is OUR Life", as presented in "Past", "Present" and "Future" segments was very well received. He called for additional helpers another year and suggested that next year's program format be changed to a hard hitting one. Publicity. Chairman Tom Egan reported that of the three newsletters sent members during the year, that the most effective one was the newspaper format one and recommended its use next year. RMCMI hired Bob Jacob who heads his own public relations firm to solicit advertising for the Proceedings on a contract/ commission basis. He attended the convention for this purpose and to solicit business card ads. A full report is on file in the RMCMI office. Scholarship. Chairman Keith McGinnis reported that five of the six scholarship recipients were present at the convention. Each was introduced to the membership at the Tuesday morning Scholarship Breakfast, presented a plaque and responded. The input from each winner was most favorable to the program. Each was appreciative of the many contacts made and the educational seminars and programs. The selection process started in March and was completed in May, except for one university which had difficulty in providing a candidate. It is suggested that the initial contact with the institutions be made in December and completed by April 1. This year, for the first time, three of the six universities were visited for the purpose of interviewing the candidates. They were Colorado, Utah and Wyoming. A very positive feedback was received from these schools and it is recommended that the practice continue. CONVENTION COMMITTEES Convention Arrangements. Doris Finnie presented the following report: As a professional meeting planner, this Diamond Jubilee convention was indeed a great challenge. One meal was added to the package and thus increased the individual cost. Snowmass Resort Association is unique in that they utilize a conference coordinator who acts as the middle man between myself and the usual persons we deal with, like AV personnel, the chef, the banquet director, the steak fry personnel, the Sunday tour etc. so the office had to become creative. For instance, we learned early on we could not deal with the local florists. It cost us lots less to buy our flowers wholesale in Denver, have my husband drive them up and our West Virginia daughter to arrange them! But, finally her floral arrangement class at CSU paid off! This was truly a Finnie family orchestrated convention. Our Lakewood daughter acted as Scholar-

Jan 1, 1987

Chelopech Mining EAD and Best Available Techniques for Management of Waste Rock in Mining Activities

Sep 13, 2010

By A. Kapito

The formation of bainite in steel is dependent on the size of the casting, the heat treatment, and the alloying elements. It is difficult to obtain a fully bainitic microstructure in steels during heat treatment because of its close proximity to the martensite (a?) reaction. The ferrite (a) and pearlite reactions in steels are also rapid and shield the bainite reaction. Alloying elements therefore need to be added to separate the bainite reaction. Boron (B) and molybdenum (Mo) are key elements added to bainitic steels because of their ability to retard the a reaction. Other elements used in the production of bainitic steels are silicon (Si), chromium (Cr), manganese (Mn), and titanium (Ti). In this paper we investigate the effect of alloying elements on the bainite reaction through the use of dilatometry. Dilatometry is a technique that determines phase transformations in the steel and through which continuous cooling transformation (CCT) curves can then be developed. Some initial results are presented of an ongoing study on the development of bainitic steels for railway wheel applications.

Jan 1, 2013

Owing to improvements in computer capacity, it is now possible to undertake fully coupled or partially coupled, three-dimensional (3D) hydromechanical Finite Element (FE) simulation of mines, including explicit representations of large numbers of discontinuities. The analysis requires fewer assumptions than uncoupled analysis or two-dimensional (2D) analysis, but may require a change in how hydrological data is collected. The way hydrological data is incorporated in stability assessment and the approach to uncertainty in hydrological information also requires discussion. The current procedures for this type of analysis are discussed, along with some practical difficulties and teachings from early applications. A work flow for integration of 3D hydromechanical modelling with pit planning and some considerations for the management of uncertain data are also proposed.

May 1, 2010

By V. Galla

Waste rock facilities (WRF) generally have a large footprint depending on the strip ratio the mine plan provides. Considerable planning is involved during the initial phase of the mine plan regarding the location of the WRF. As the mining operations are commenced the locations of the WRF change accordingly with the variations in the mine plan involving feedback and support from local communities and stakeholders. Waste rock facilities management becomes challenging when the area available for placement is limited due to terrain topography, environmental and permitting constraints. Risks associated in the design of waste rock facilities constitute particle size of rock, chemistry associated with the rock for reactivity and stability of the over all facility. This paper will provide some insights on designing, scheduling and managing a WRF. Emphasis on geotechnical, geophysics and geochemistry aspects of waste rock with reference to design, construction process and scheduling of WRF are also presented. Design improvements in the reclamation slope of WRF for erosion control will be discussed. Continuous improvement (CI) methodology will be introduced in the process of WRF operations. Current practices and future recommendations towards sustainability and consistency in operating WRF will be discussed in conclusion.

Jan 1, 2011

The modelling of lithological domains is a critical step in mineral resource and reserve evaluation. Deterministic models rely on an interpretation of the available drill hole data and expert knowledge, but do not account for the uncertainty in the spatial extent of the lithological domains. Instead, probabilistic models based on conditional simulation can be used to map the probabilities of occurrence of the domains within the deposit, which reflect the uncertainty in their presence or absence at unsampled locations. The mineral grade model is then obtained by weighting the predicted grades associated with each lithological domain by the probability of occurrence of this domain. Such an approach accounts for the continuity of the grades proper to each lithological domain and for the uncertainty in the spatial extent of these domains within the deposit. An application to a porphyry copper deposit is presented. Keywords: spatial uncertainty; plurigaussian simulation; geological control; kriging; geostatistics.

Jan 1, 2007

By R. Webber-Youngman

The Department of Mining Engineering at the University of Pretoria accepts that the process of teaching and learning improvement is an ongoing exercise with the ultimate aim to deliver well-rounded mining engineering practitioners. Various challenges impact on the success of this process. An integrated and innovative process was developed and is followed in the Department to overcome these challenges. The aim of the Department is to apply a holistic teaching approach by introducing multiple integrated interventions with regards to teaching and learning strategies. Three phases of this process are discussed in this article, and are illustrated in Figure 1. During the first phase, prior to 1999, several teaching and learning challenges were identified in the Department of Mining Engineering. These challenges are discussed in the next section. In the current phase, a variety of interventions to address the challenges are being developed, implemented (in some cases piloted), and evaluated. The future phases will focus on the improvement, successes, and full roll-out of current interventions, as well as on training, development, and support for all staff members to participate in the process. (Figure 1)

Jan 1, 2011

The Ekati Diamond Mine is located on permafrost terrain in CanadaÆs Northwest Territories. The mine rock consists of: diamond-bearing and barren kimberlite; and surrounding waste rock such as granite. The kimberlite occurs in several vertical æpipesÆ that are, or will be, mined using open pits. Early predictions of drainage chemistry at Ekati identified the potential for ARD due to sulfide oxidation from both waste rock and kimberlite. This was surprising for the kimberlite, because neutralisation potentials (NP) are typically hundreds of kg CaCO3 equivalent/t. However, subsequent testwork showed that substantial portions of the NP ædisappearedÆ quickly, apparently due to the unusual non-carbonate mineralogy. In any case, additional predictive work concluded much of the rock was benign and there would be no ARD. Shortly after mining started, ARD appeared from both the waste rock and kimberlite, although a few years passed before the company and its consultants recognised that at least some of the acidic water was ARD. Numerous other processes have been put forward as possible explanations for the remaining acidic drainage, although none have been either confirmed or eliminated. Because: the causes of the ARD and acidity are not known; no causes have been eliminated and more have been added; drainage chemistry was not predicted accurately; and future mining will encounter similar rock. I believe the Ekati Diamond Mine needs high-level assistance to understand current chemistry and to avoid problems with future drainage. Organisations like INAP, MEND3, and universities could provide this assistance.

Jan 1, 2003

By Frank Chase

Longwall mining has gained the reputation as being the safest extraction method in underground coal mines. However, one of the most difficult tasks associated with longwall mining is moving the face once a panel is completed. Based on Mine Safety and Health Administration (MSHA) fatality reports since 1996, longwall face recovery operations have claimed the lives of 5 U.S. miners and have resulted in numerous injuries. Recovery operations can be hazardous because they involve moving large pieces of equipment in very confined spaces. They are also conducted in highly stressed ground conditions due to front abutment loads generated by panel extraction. Shield removal is the most hazardous operation during face recovery because miners are constantly exposed to the unpredictable gob edge. To protect the miners, one or more walking shields, cribbing and/or other supplemental roof and standing supports are typically employed as breaker line supports as each shield is removed. At the Harris No. 1 Mine in southern WV, mobile roof supports (MRS?s) have been used in lieu of traditional walking shields on 17 face moves since 1997. MRS?s are shield-like support units mounted on crawler tracks and are commonly used during room-and-pillar retreat mining operations. For longwall recovery, the two biggest advantages that MRS?s have over traditional walking shields are that they are remotely controlled and are highly maneuverable. MRS?s have contributed to safer shield recovery and shorter move times at the Harris No. 1 Mine. This paper will address both the safety and the operational issues associated with MRS usage during shield recovery. It will also discuss new developments, including the use of the inherently safer battery powered MRS?s, which have been recently certified by the Mine Safety and Health Administration.

Jan 1, 2007

By P. R. Clifford

Phosphogypsum is a byproduct of the manufacture phosphoric acid. There are approximately one billion tons of phosphogypsum stored in stacks in northern and central Florida. The Florida Institute of Phosphate Research (FIPR) is investigating potential uses of phosphogypsum. These include using phosphogypsum as a road base material, as a soil amendment in agriculture, as a daily cover in landfills, and as a construction material. The results of this research will be presented and will be discussed in light of regulatory barriers to the use of phosphogypsum.

Jan 1, 2002

The 109th Annual General Meeting of The South African Institute of Mining and Metallurgy was held at The Country Club, Johannesburg, Napier Road, Auckland Park on Wednesday, 16 August 2006. Special General Meeting A Special General Meeting to consider the changes to the Constitution was held immediately prior to the AGM. 1. Purpose In order for the SAIMM to remain relevant and ensure maximum value to all members, Council propose three changes to the Constitution. 2. Background Three changes to the Constitution were proposed by the Council on 21 July 2006. These changes now have to be approved by means of a ballot at a Special General Meeting. These three proposed changes are discussed briefly below:

Jan 1, 2006

Objective The main purpose of this video is to teach mine rescue personnel certain aspects of rescue work that are not traditionally taught. These include the strain caused by working continually under adverse conditions; the "survivor guilt" that occurs from being spared the fate of one's deceased cohorts; and the posttraumatic stress that may be experienced during the sometimes lengthy task of recovering the victims' bodies. Background On November 20, 1968, an explosion rocked the Farmington No. 9 Mine in northern West Virginia (figure 1). The explosion killed 78 of 99 miners who were working in the mine, including all but one member of the mine's rescue team. Some 30 years after the event, researchers from the NIOSH Pittsburgh Research Laboratory (PRL) conducted a video interview with Danny Kuhn (figure 2), the only Farmington No. 9 mine rescue team member who was not working that day and who did not die in the explosion. According to the Mine Safety and Health Administration (MSHA), there are about 80 underground coal mine rescue teams in the United States, and according to the National Mining Association, there are more than 850 underground coal mines. This represents a significant decrease in both over the past decade. The low number of rescue teams is a concern because serious incidents, though fewer, still happen, and if a disaster occurs, there will be fewer rescue teams to respond. This would result in an increased need to use available human resources very efficiently. Much training to prepare these rescue teams still takes the form of what educators call "teaching to the test." In other words, teams practice in order to win mine rescue contests. This test-oriented approach has traditionally been augmented by interactions with others who have responded to real situations or by participating in actual incidents. Given few incidents and fewer rescue teams from whom to derive enrichment, the preparation of coal mine rescue personnel becomes a problem. Recently, more emphasis has been placed on active learning, such as working out problems in smoke. These sessions more nearly simulate the actual conditions that today's team members might rarely encounter. To properly prepare and retain the current coal mine rescue personnel who are left in the workforce, it is necessary not only to offer such hands-on experience, but also to replace the learning narratives that once were passed from team to team. The present video is intended to contribute in that capacity. Approach NIOSH researchers first learned of Mr. Kuhn in the fall of1998. Mr. Kuhn was contacted and agreed to an interview. An oral history interview was conducted with Mr. Kuhn in early November1998. After reviewing the videotape of the interview, researchers determined the content to be so rich as to warrant a second interview in a more formal setting. The second interview was done in early December 1998. During this interview, Mr. Kuhn spent about 2 hours describing the Farmington disaster, including the workplace climate leading up to the explosion, the events that took place in the 10 days after the explosion, and the nearly 10-year effort to safely and successfully recover most of the victims' bodies. The videotape of the second oral history interview with Danny Kuhn was reviewed and edited by NIOSH researchers for content. Careful attention was used to ensure that valuable information was presented, but within a reasonable timeframe. A detailed map of the Farmington No. 9 Mine was edited into the final video and used to highlight critical features as they were being described by Mr. Kuhn. Results and Accomplishments A 60-minute videotape and instructor's guide for use in safety training or other settings was completed. The target audience consists of all those who work in underground coal mines. This training video will help safety instructors better prepare mine rescue team members for the situations that they will encounter when engaging in extended rescue and recovery work. As a result of this expectations training, team members will be more likely to serve their

Mar 1, 2002

By Francis Foley

Small cracks in a plane normal to the axis of steels are found to be prevalent around the water hole of drill steels that have been in service for an unknown period of time. Cracks are not found on the exterior surface of the steels nor to any noteworthy extent even in the water holes of new drill steels. Undulations and serrations are found in the surface of the water hole in new steels; it is in the bottom of such defects that cracks appear to develop in used steels. The occurrence of the more serious of these cracks at the point in the steel to which it has been heated for forging or hardening is thought to account to a great extent for failures in that region. DURING the past, year, we have investigated the cause of 88 per cent, of the failures by breakage near the bit end of some 1-in. hollow, hexagon, drill steel used in a metal mine. This breakage in the region of the bit end of the steel was peculiarly interesting because we have been led to believe that breakage is most prevalent at the shank end of drill steels near the place where the steel is gripped in the chuck of the machine. Records from the mine showed, also, that the breakage was much more frequent in the short lengths of large gage than in the longer steels; this is shown graphically in Fig. 1. Because the shorter lengths of steels are usually those that have been made from broken pieces of long steels or from steels that have worn down in service, rarely being made from new stock, those who are wont to suspect steel of tiring and crystallizing in its old age through fatigue are quite apt to see in this instance an argument in favor of their idea. As usual, a careful examination of these steels reveals defects of a character hardly to be overlooked in favor of such a cause. The steel in question was rolled with a sand core and was of the usual drill steel composition: Carbon 0.85 per cent., manganese 0.60 per cent., silicon 0.25 per cent., phosphorus 0.02 per cent., and sulfur 0.02 per cent., with the exception that in some specimens there was vanadium, not exceeding 0.20 per cent.

Jan 3, 1924

By Laurance L. Oden

Titanium-enriched smelter slag produced commercially by Quebec Iron and Titanium Corp., Sorel, Quebec, was evaluated as feed material for a process developed by the Bureau of Mines to prepare rutile. Glass-forming agents including P205, B203, and two binary mixtures were added individually to the as-received and preoxidized smelter slag, and the nonferrous tramp oxides were effectively partitioned into the resulting noncrystalline phase. Iron in the ferrous oxidation state was moderately soluble in the glass of reduced specimens but less soluble under oxidizing conditions. The solubility of iron oxide in phosphate glass exceeded the solubility of iron oxide in borate glass. Effective conversion of titanium oxide to rutile was not achieved in the high-iron commercial smelter slag, and 20 to 30 pct of the titanium remained as pseudobrookite, a mixed iron-titanium oxide.

Jan 1, 1973

By R. R. Wells

This report summarizes the results of laboratory testing of copper-bearing magnetite ore from the Poorman, Bush & Brown, and Copper Center deposits, Kasaan Peninsula, Prince of Wales Island, southeastern Alaska. The ores contain minor amounts of chalcopyrite and pyrite. Intimate association of these sulfides with magnetite necessitates fine grinding for adequate liberation and rejection of copper and sulfur and for the production of high-grade iron concentrate low in objectionable impurities. Laboratory tests indicated that the optimum results can be obtained by flotation of ore ground to minus-100-mesh, with subsequent wet magnetic separation treatment of the flotation tailing. A summary of results obtained by this treatment of the three samples tested is shown in table 1.

Jan 1, 1957

By E. Houdremont

THE different influences exerted by the various alloying elements in iron and iron-carbon alloys give rise to a great number of complexities, which are difficult to grasp. It is important therefore to study any sys-tematic relations that may exist between the effects exerted by the various alloying elements, in order to obtain a general classification and thus a clearer conception of the nature of alloy steels. A systematic survey of the alloys of iron, based on an investigation of the binary equilibrium diagrams, was recently published by Wever. Although his work deals little with properties of importance in works practice, its purpose being rather to point out the theoretical agreement among the types of binary equilibrium diagrams and the position of the alloying elements in the periodic system (atomic radii, etc.), the classifica-tion proposed nevertheless also suggests relationships among the proper-ties of the alloys in question, even though the alloys may contain carbon in addition to iron and the alloying element. Wever divided the alloys of iron into one group exhibiting an open or enlarged gamma field and another exhibiting a closed or restricted gamma field, with both groups capable of further subdivision depending upon whether a continuous series of solid solutions is formed, or, owing to the separation of compounds, etc., only a limited series. Thus all alloying elements which with iron form a closed gamma field, a "gamma loop," produce alloys that beyond the composition correspond-ing to the greatest extent of the gamma loop are composed of ferrite alone at all temperatures. Alloys of this composition accordingly are not susceptible to ordinary heat treatment because of the lack of tran-formations. Steels. of this class may thus be divided into steels that contain less than the critical amount of alloying element, and are subject

Jan 1, 1934

By C. S. Giggins, F. S. Pettit

The oxidation of Ni-Cr alloys in 0.1 atm of oxygen has been studied at temperatures between 800" and 1200°C. For alloys with 30 wt pct or more Cr, continuous layers of Cr2O3 are formed during oxidation. In the case of alloys with chromium concentrations between approximately 5 to 30 wt pct, external scales of Cr203 are formed over grain boundaries whereas internal precipitates of Cr2O3 and external layers of NiO are formed at other areas on the alloy surface. When such conditions are present on the alloy surface, chromium diffuses laterally from those areas covered with a continuous layer of Cr2O3 to areas where a Cr2O3 sub scale exists and it is possible for the sub-scale zone to become separated from the alloy by a continuous layer of Cr2O3. Whether such a state will be attained depends upon the initial grain size of the alloy and the oxidation time. When the concentration of chromium in the alloy is less than 5 pct, Cr2O3 is formed internally both at grain boundaries and within the interior of grains and the alloy is covered with an external layer of NiO. MECHANISMS which describe the growth of oxide scales on nickel-base superalloys are complex and the effects produced by the various elements in these alloys on the oxidation behavior of superalloys are not clearly understood. In order to determine the influence of the different elements on the oxidation behavior of superalloys, it is first necessary to examine the oxidation properties of binary nickel-base systems which contain the principal elements present in the superalloys and then progressively more complex systems until compositions typical of the superalloys are attained. Chromium is present in virtually all nickel-base superalloys and the purpose of the present studies was to examine the selective oxidation of chromium in Ni-Cr alloys. The oxidation characteristics of Ni-Cr alloys have been extensively studied1-" to date principally as a result of the high oxidation resistance exhibited by some of these alloys. Ni-20Cr* has long been known *All compositions are given as wcight percent unless specified otherwise. to be oxidation resistant and is commonly used as resistance heating elements for service temperatures up to 1100°C. This alloy cannot be used for extended periods of time at higher temperatures because of the apparent reaction of the external scale with oxygen to form gaseous CrO3. In spite of the considerable work cited above some important aspects of Ni-Cr oxidation still remain unresolved. Virtually all of the previous studies agree that small additions of chromium to nickel, e.g., <10 wt pct Cr, result in increased oxidation rates as compared to that of pure nickel, whereas larger additions, e.g., 20 to 30 wt pct Cr, form alloys with substantially lower oxidation rates. The controversial aspects of the oxidation mechanisms for these alloys that still remain unresolved are as follows: 1) A description of the oxidation mechanism for the low chromium alloys. 2) A description of the oxidation mechanism for the high chromium alloys, particularly with respect to the composition of the external scale which results in the lower oxidation rates. 3) The specific alloy compositions at which the oxidation mechanism changes from that obtained for low chromium contents to that of the high chromium alloys and the reason for this transition. EXPERIMENTAL The Ni-Cr alloys listed in Table I were prepared from high purity metals by nonconsumably arc melting and casting as buttons. These alloys were then given a preliminary annealing treatment in argon at 815°C for 100 hr to promote homogeneity. Each button was cut into 0.250 in. thick sections that were subsequently cold-rolled to 0.050 in. thicknesses and annealed in argon at 815°C for 48 hr to provide a twinned, equi-axed grain structure. The grain size for these alloys was not uniform and the limits, within which the average grain size lies, are given in Table I for the single-phase alloys. All the alloys were single phase with the exception of the Ni4OCr alloy in agreement with the Ni-Cr phase diagram.&apos;&apos; Rectangular specimens were cut from the sheet to provide surface areas of approximately 2.5 sq cm. Exact areas were determined with a micrometer after surface preparation was completed. All of the specimens except the Ni-40Cr alloy and pure chromium were polished through 600-grit Sic abrasive paper, ultrasonically agitated in ethylene trichloride, rinsed with ethyl alcohol, and electro-polished. The specimens were electropolished in a 10 vol pct H2SO4 (conc), 6 vol pct lactic acid, methyl alcohol solution at 70" to 80°C for 2 min at a current density of 0.8 to 1.2 amp per sq cm. This electro-polishing procedure did not produce acceptable surfaces on the Ni-40Cr alloy nor on pure chromium and the oxidation properties of these materials were obtained for specimens polished through 600-grit Sic

Jan 1, 1970