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By Frame Ritzert, Dennis Keller, Vijay Vasudevan, David Arenas

"An investigation was conducted to describe topologically close packed (TCP) phase instability as' a function of composition in the advanced ·Ni-base superalloy Rene N6. TCP phases are detrimental to overfill high-temperature performance of Ni-base superalloys because of their brittle nature and because they deplete the Ni-rich matrix of potent solid solution strengthening elements. Thirty-four variations of polycrystalline .Rene N6 determined from a design-of-experiments approach were cast and homogenized at 13 l5°C for 80 hours followed by exposure at 1093°C for 400 hours to promote TCP formation. The alloys had the following composition ranges in atomic percent: cobalt 10.61 to 16.73, Mo 0.32 to 1.34%, W 1.85 to 2.52%, Re 1.80 to 2.11%, Ta 2.36 to 3.02%, Al 11.90 to 14.75%, and Cr 3.57 to 6.23%. Physical and chemical characteristics of all microstructures obtained were described using various analytical techniques. From these observations, a mathematical description of TCP occurrence (s and P phase) was generated for polycrystalline Rene N6.IntroductionNi-base superalloy single crystals represent the state-of-the-art for turbine engine airfoil application as they offer the best balance of properties to allow for the high operating temperatures required: for efficient engine operation.1 Current trends in alloy design take advantage of improved creep rupture strength with the addition .of higher levels of refractory elements. 2 In .particular, the addition of significantly higher levels of Re in third generation superalloys is key for both microstructural stability and creep rupture strength. 3 While the presence of the refractories is thought to provide strength benefits from solid solution hardening, a tendency for alloy instability in the form of topologically-close-packed (TCP) phases or secondary reaction· zone (SRZ) ·phenomena accompanies the high refractory content. 3 The formation of these phases in sufficient amount is detrimental to the overall high temperature performance of Ni-base superalloys because of their brittle nature and because they deplete the Ni-rich matrix of potent solid solution strengthening elements.4 The tendency for a particular composition to form TCP may not be immediately known since the precipitation of TCP phases in Ni-base superalloys is nucleation controlled, thereby requiring long times at elevated temperatures to precipitate. 5 They preferentially nucleate along the octahedral planes of the Ni-base superalloys, usually in areas of refractory metal enrichment at grain boundaries or inside dendrites.5-6 In Rene N6, two closely related TCP phases, a and P, have been observed.2"

Jan 1, 1998

The Mt Lyell Mine at Queenstown, Tasmania was re-opened in 1995 by Copper Mines of Tasmania Pty Ltd, a wholly owned subsidiary of Mt Lyell Mining Co Ltd. The re-opening followed over 100 years of copper and gold mining at Mt Lyell. Major changes in practice were implemented across the site. Preventing further damage to an already disturbed environment was a major priority. Sublevel caving, at a lower cut-off grade, replaced open stoping for the deep underground mining. Development and later stoping are handled by a contractor, National Mine Management Pty Ltd, in the largest underground contract awarded at the time. Large scale sublevel caving was new to Mt Lyell and not widely practised in Australia, requiring studies and systematic development of the method, particularly in drilling and blasting. Rehabilitation and upgrading of mine infrastructure have been and will continue to be a challenge. The mine has, since 1995, returned to being a stable producer with potential for growth.

Jan 1, 1998

By C. M. Jones

Cyprus Sierrita Corp. has developed a training program that has led to several significant improvements in safety performance and productivity. Truck productivity has increased 6% as measured by truck cycle times. Increased skill levels and awareness on the part of the mine's operators are due to the new training effort. Costs associated with productivity training have been about $185,300. This includes program development and execution costs, as well as lost productivity during the training itself. These costs are offset by $1.9 million in savings attributable to the increased skill levels of technicians due to the training effort. Cyprus Sierrita is a subsidiary of Cyprus Amax of Englewood, CO. The company operates a copper and molybdenum mining and processing facility south of Tucson, AZ, near the town of Green Valley. The Cyprus Sierrita operation produces about 109 kt/a (240 million lbs/ year) of copper, 11.3 kt/a (25 million lbs/year) of molybdenum, 31.1 t/a (1 million oz/year) of silver and 1.8 t/a (4,000 lbs/year) of rhenium. The opera¬tion employs 770 people at the site. About 200 of these employees work in the mine operations. Mining at Sierrita uses standard open-pit techniques. Crews of 43 people rotate on 12-hour shifts. Hourly technicians are nonunion and do not use rigid job classifications to define pay. Rather, the system is designed to pay employees for what they are able to do. Administering this effort requires that training opportunities are provided to those people who desire them. Successful training opportunities al¬low people to gain skills. The more skills an employee can demonstrate, the higher his or her "tech level." A technician's pay is commensurate with his or her tech level. Much of Sierrita's training in past years concentrated on building basic

Jan 1, 1998

By Dan Johnson

The discovery of rich alluvial diamond deposits on Namibia?s Skeleton Coast in 1908 began a period of intense exploration and mining off the coastal sand; and shallow surf zones. In the mid-60s a Texas entrepreneur, Sam Rollins took the search to the seafloor. The inhospitable conditions encountered made the early going difficult. After a slow start, the past 10 years have seen much progress in geologist?s understanding of the deposition mechanics and the use of sophisticated geo-physical and sampling techniques to aid in the discovery of economic deposits. Diamondfields, in a joint venture with BHP and Benguela Concessions, began an exploration program in 1994 for sea-bed diamonds off the Port of Luderitz in Namibia. This program has progressed to a mine development program with the potential of creating a 500,000 carat per year operation. The mining technologies being considered include state-of-the-art, remotely operated sea-bed crawlers and high volume dredges feeding to semi-mobile processing platforms. The company's objective is to use the best proven technology to create an environmentally responsible operation with the lowest fixed operating costs and the longest and safest weather operating window of any offshore operator working Africa's diamond coast.

Jan 1, 1998

By Thomas Barczak

Hydraulic cylinders are used in several roof support systems, such as longwall shields and mobile roof supports, to provide critical ground control Many state-of-the-art hydraulic support system operate at pressures as high as 7,000 psi to provide the necessary support capacities Pressure in the upper stages of multi-stage cylinders can be intensified by a factor of 2 or 3 providing pressures of 20,000 psi or greater. A proper understanding of the operation of these high pressure systems is necessary to safely maintain and repair these support systems. Likewise, the performmce characteristics need to be fully understood to evaluate the impact of design parameters on the capability of the support to maintain effective ground control This paper examines the basic operating principles of state-of-the- art hydraulic cylinders and discusses relative issues pertaining to. (1) setting loads, (2) support stiffness, (3) yielding behavior, (4) errors in assessing support loading, and (5) hydraulic failure mechanisms and how to detect them

Jan 1, 1998

By Malcolm J. A. Swallow

In June 1997, Mount Polley Mining Corp., a division of Imperial Metals Corp., completed an 18-kt/d (20,000 stpd) gold-copper mine in central British Columbia. Fast-track construction and extensive off-site construction were combined with an aggressive project schedule to build the mine in one year. This was three months ahead of schedule and 7% below the original budgeted cost of C$123.5 million (US$86 million). The Mount Polley Mine was the first of a crop of new open-pit mines in British Columbia. The Mount Polley deposit has been explored since the mid-1960s when it was known as the Cariboo Bell property. From 1988, Imperial Metals completed drilling and metallurgical testing on the deposit. This led to a positive feasibility study and the issuing of a Mine Development Certificate in 1991. The project was later shelved due to falling metals prices and the strength of the Canadian dollar. In late 1994, Imperial merged with Bethlehem Resources Corp., bringing a strong project team to the company. The deposit was then re-evaluated, ore reserves revised and additional metallurgical testing was performed. The result was a revised project plan. It indi¬cated that a financially feasible gold-copper mining op¬eration could be constructed at Mount Polley operat¬ing at 18 kt/d (20,000 stpd). In May 1996, an agreement was reached with Sumitomo to jointly fund and develop the project. By early 1996, final plans and permits were being prepared for construction, scheduled to begin in June 1.996. On-site work commenced on May 28th, 1996 following lifting of the road restrictions. Mount Polley Mining acted as its own project manager. Construction was completed in June 1997. Plant runup took place in July and full production began in August. Through the use of off-site construction and the careful selection of contractors who cooperated to complete some 12 major contracts, it was possible to reduce the mine and mill construction time from 16 to 13 months. Off-site construction for all possible aspects of the work and the use of used milling equipment allowed significant savings in overall capital costs of construction. Total costs for the mine, mill and tailings dam equated to C$6,100/t/d of throughput. The mill design incorporates several innovative features that will aid maintenance and allow flexibility of operation. The operation is designed as a closed system and meets the latest environmental standards. Concentrate is shipped by truck to the port of Vancouver. Revenues for the mine come from the mine's production of about 3.1 t/a (100,000 oz/year) of gold and 10.8 kt/a (24 million lbs/year) of copper during the first four years of the 12-year mine life.

Jan 1, 1998

By S. Mason

Many organizations are realizing that continual improvement in health and safety relies on addressing the potential for various forms of human error. Of these, violations are often the most frequent form associated with accidents. These occur when an individual, or individuals, deliberately contravenes established and known safety rules. They have been associated with up to 90% of accidents and incidents in some industries and yet rarely receive the systematic attention they deserve in the promotion of safety. This paper presents underlying motives which cause violations. These can vary significantly from mine to mine and from job to job. Managers need some measure of attitudes to determine the underlying motives behind violations if they are to determine effective strategies for promoting safe behaviour. Questionnaires form the starting point to address attitudes and the motives behind rule violations. The choice of the most suitable questionnaire, however, will vary from organization to organization. Guidelines on the choice of questionnaire are offered.

Jan 1, 1998

Drilling and blasting operations have historically been viewed as a necessary 'evil' part of mining, whose costs should be minimised by whatever means possible. In the past, when operations depended primarily on crushing and milling for ore re

Jan 1, 1998

Powered support plays a major role in longwall mining and improper selection may lead to a disaster. While different countries follow different norms, a universal approach is needed to be developed. For this purpose, a computer program C-ALPS

Jan 1, 1998

By Kiyoshi Shibata

A new assessment model has been proposed for metal production and its recycling system. The model consists of three processes, smelting of ore, cascading and upgrading of metal scrap. The present approach is to assess the total energy consumption of the system, by introducing two equations for describing the relationships between critical impurity content and the mass of production or scrap recycling. The total energy consumption in the system can be described as a function of recycling rate and performance of the upgrading process. The present model suggests that the impurity removal efficiency and yield in the upgrading process are essential to reduce the energy consumption in the systems. Especially, such points should be explicitly controlled in recycling of aluminum. The potential capability of this model was also discussed by obtaining several quantitative information required for the process design and the operational control of beneficial recycling of metals.

Jan 1, 1998

By J. Gao, H. O. Gekonde, S. V. Subramanian

"The functional role of inclusions at low cutting speeds is to promote ductile fracture in chip formation process, whereas the role of inclusions at high cutting speeds is to prevent tool crater wear by suppressing the tribological phenomenon of seizure at the tool-chip interface. Glassy oxide inclusions are engineered into the workpiece to form a viscous layer in-situ at the tool-chip interface at high cutting speeds. The viscous layer lubricates the tool-chip interface to prevent the seizure. In comparison with the large volume fraction of inclusions needed for promoting ductile fracture at low cutting speeds, the amount of inclusions required for lubricating the toolchip interface at high cutting speeds is very small and is in the range that is typical of clean steels. The chip fracture process at high cutting speeds is aided by strain rate hardening of the matrix, which facilitates chip disposal of relatively clean steel.Inclusion engineering for high speed machining involves the control of the rheology and composition of inclusions to meet target viscosity at the tool-chip interface. The application of thermodynamic models in controlled production of inclusions in steels designed for high speed machining is discussed."

Jan 1, 1998

By H. H. Murray

Industrial usage of clays for current and new applications will continue to grow into the next century. The rate of growth will be highest in the less developed areas of the world. Transportation costs are a significant part of the delivered price, so the location of reserves and processing facilities for kaolin, bentonite, and palygorskite (attapulgite) are reviewed relative to serving these emerging markets. New value added applications will increase in the more developed areas which will require high quality raw materials, more sophisticated processing, and rigorous quality control.

Jan 1, 1998

By Laurel E. Burns

Alaska is in competition with the rest of the world for exploration dollars. Providing a "seed package" of airborne geophysical data for the state's numerous mining districts encourages companies to begin more detailed exploration in more areas than they could have afforded on their own. When data are already available, the initial risk decreases for people involved in exploration. Airborne magnetic and electromagnetic data help ge¬ologists and geophysicists determine what rocks and structures are present under overburden and vegetation. These data form a fundamental package that exploration companies want before intensively exploring most regions. Individual mining companies have conducted their own geophysical surveys during the past several decades. However, these data are not available to other companies. The companies able to afford geophysical surveys have less money for ground exploration after purchasing expensive, private geophysical data. Therefore, they are not able to explore as many places as they might. Additionally, since data are not shared with other exploration companies, the proprietary surveys do not foster intercompany competition to move projects forward. Individual prospectors and small companies can not afford their own geophysical surveys. "It is more often than not the grassroots exploration efforts of the smaller operator that leads to significant discoveries," said Klaus M. Zeitler, senior vice president for development and exploration at Teck Exploration. Acquiring and releasing the geophysical data to the public produces several benefits. The increased explo- [ ]

Jan 1, 1998

MIM Holdings Limited (MIM) committed to a long-term future in copper in the Carpentaria Mineral Province in 1996 with the development of the Enterprise and Ernest Henry mines, and an upgrade of MIMsÆ copper smelter in Mount Isa, and copper refinery in Townsville. The upgrade of the copper smelter will enable the smelter to produce 250 000 tpa of copper with a single primary smelting unit, the copper Isasmelt furnace installed in 1992. The copper Isasmelt furnace currently smelts concentrate containing 145 000 tpa copper. To reduce the risk associated with the copper smelter upgrade, and shorten the ramp up time of the upgraded smelter, two high-rate trials were undertaken in 1997 to demonstrate that the copper Isasmelt furnace could, with an additional 525 tpd of tonnage oxygen, treat concentrates containing 250 000 tpa copper. During the trials the concentrate feed rate to the Isasmelt furnace was increased from its average rate of 100 tph of concentrate to 150 tph of concentrate. The increase in the capacity of the furnace was achieved by: supplementing the installed tonnage oxygen capacity of 595 tpd with an additional 300 tpd supply; reducing variability in the furnace feed rate from ¦25 per cent to less than ¦5 per cent; and reducing tramp air. The Isasmelt furnace smelted concentrate at a rate of 140 to 150 tph for four hours 25 minutes during Trial 1, and at a rate of 150 tph of concentrate for five hours and 30 minutes during Trial 2. The oxygen utilisation was 100 per cent during the trials with the process remaining under control. As a result of the development work for the trials the average treatment rate of the furnace under normal conditions increased by ten per cent.

Jan 1, 1998

This paper will examine some of the significant developments in the training field in Australia in the past decade and the application of these changes to the mining industry generally, and the coal sector specifically. Three major aspects will be examined:1. Competency - the use of Industry Competency Standards and how these can be used for achieving enterprise performance requirements2. Assessment - making judgements about an individual's competence, and using a rigorous assessment system as the basis for the "authorisation" system at a mine3. Evaluation - ways to evaluate the return on investment in training, and convincing CEO's/shareholders that your training dollar is being spent wisely.Before examining these issues, it is important to understand the drivers of change in the training systems in Australia, and the functions that Industry Training Advisory Bodies (ITABs) perform.

Jan 1, 1998

By A. P. Chaves, A. Gomes

The cyanidation and adsorption processes at Fazenda Brasileiro mine were studied with the aim of increasing hydrometallurgical recovery. Technical evaluation of the processes consisted of (i) quantitative mineralogy of ore samples collected in different points of the circuit, and (ii) comparison of plant performance in the original (designed CIP) and in the modified (current CIP/CIL) circuits. An empirical correlation between process variables and gold grades in the cyanidation tailings was established. The suggested modifications in the circuit and in the operation conditions led to an increase in gold recovery, from 91 to 93.5%. Annual revenue is expected to show an increase of approximately US$ 1 million.

Jan 1, 1998

By James W. Martin, Brad H. Droegmiller

As construction projects continue to get larger, greater demands are placed on systems to provide higher production rates at reasonable costs. This paper shows the application of dozer-trap loading versus other methods of moving bulk materials. Most conventional methods employ multiple types of heavy equipment to accomplish a single task. Trap loaders fed by dozers and discharging onto overland conveyors offer an alternative/economical means of high volume bulk material movement. This paper will discuss the process of trap loading to overland conveyors.

Jan 1, 1998

By B. J. Madden

Over 206 million tons of hard coal were mined in South African collieries in 1996. Some 132.5 millions tons came from underground operations and approximately 120 million tons came from bord-and-pillar workings resulting in between 100 000 and 150 000pillars being formed. Coal pillar design remains a significant feature of South African mining. This paper reviews South African coal pillar design procedures in the light of 90 pillar collapses that have occurred since 1904. It shows that, while the current pillar strength formula is still valid within the original empirical range of Salamon1,cognisance must be taken of local conditions. Current South African coal pillar research is attempting to account for the variations in local conditions with the emphasis on the effect of discontinuities and pillar deterioration. It is suggested that a more holistic approach to pillar design be adopted to include a design methodology that examines the stability of the roof, pillar and floor of the underground workings. Using this approach, deviations from the empirical database used by Salamon and Munro will be incorporated into the design methodology resulting in more stable underground workings.

Jan 1, 1998

By Rolf Koenig

After the Dynatronic firing system was demonstrated for the first time at the SEE conference in Miami in 1987, it was officially approved in Germany at the beginning of 1993. Dynatronic has now been on the market for 5 years. At present, it is used in several European countries and successful test series have been running in Australia.

Jan 1, 1998

By Terry Mandziak

Typical leach mine operations recover gold values through the application of a dilute cyanide solution onto ore within an engineered facility. Key to the success of mining operations is the, containment and management of the cyanide solutions within the facility. Properly engineered' facilities will have containment systems that are both protective of the environment while enhancing solution recovery. This paper not only discusses general containment standards, but identifies state-of-the-art containment and monitoring practices;

Jan 1, 1998