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By Daniel Scott

Mines have used explosives for economical fragmentation for many years. It can therefore be expected that the mining industry has thoroughly researched how to achieve the most efficient blast. However, there is still a large amount of iteration that must be undertaken before blasting at a mine site can be refined enough to allow for consecutively successful blast results. And then the geology changes. This paper will present an approach to blast design that considers production goals, geology, budget, and safety, and will contrast the proposed method with well established blasting theory.

Jan 1, 2012

By Kenneth McGowan

"The aluminum industry is the 5th largest consumer of energy and the largest consumer of energy on a per-weight basis. Process heating accounts for 25% of the energy consumed to manufacture aluminum. Consequently, the generation of this energy results in the production of a significant amount of CO2 (over 3.75 million metric tons in 2003)1. As a result, the Aluminum Industry Technology Roadmap of 2003 listed the development of improved refractory materials as a goal to reduce energy use and decrease greenhouse gas creation. The result of a R&D effort addressing this desire is the development of patented microporous refractory materials for metal contact applications in all furnace areas including the belly band. It has been demonstrated that this material can reduce energy consumption up to 38% in furnaces and significantly reduce heat loss in launder and trough systems. Furthermore the material developed is non-wetting and remains un-penetrated by metal throughout its lifetime. The material does not contribute to the formation of corundum. As a result, the energy efficiency of an older lining remains intact compared to standard refractory materials which may have an initial high insulating value (such as lightweights and board) or standard dense refractory (even with penetration inhibitors) both of which show a rapid increase in thermal conductivity as the refractory is penetrated with aluminum and formed corundumIntroductionThe aluminum industry is the second largest producer of metal in the United States, behind the iron and steel industry. It is the 5th largest consumer of energy and the largest consumer of energy on a per-weight basis. Process heating is required to melt, hold, purify, alloy, and heat treat the metal and accounts for 25% of the energy consumed to manufacture aluminum. As such, process heating is the second largest energy consuming operation. Smelting, which utilizes an electrolytic reduction process is the largest energy consuming operation1.Most process heating is accomplished through the use of fossil fuels, either directly or indirectly. The choice of fuel is dependent on a plant’s location and fossil fuel availability. Table I shows the processes impacted by refractories and the calculated BTU’s generated by usage of the respective fuels as well as the Metric Tons (MT) of metal passed through each process in 20001."

Jan 1, 2009

By J. W. Craig

CHROME ore, which is used in Canada in the production of ferro-alloys, in a variety of refractories, and indirectly in many chemical industries, is both commercially important and scientifically interesting. The sight of chromium metal is familiar to all of us in the home, the office, the automobile. Chromium is synonymous with armaments: it is understood to be one of several essential metals in tanks, which played an important role in the defeat of France in the spring of 1940. Chromium, in other forms, comes into our daily lives by way of paint and leather, of the familiar green ginger-ale and beer bottles, and more indirectly in every pound of steel produced in the .Dominion. Necessary to our civilization in peace and war, the ores of chromium occur in many corners of the earth. This paper attempts to describe the chemical constitution of chrome ores, their world distribution, and the various chrome products and their industrial applications in Canada.

Jan 1, 1940

By Paul F. Sikora, John W. Weeton, Philip A. Clarkin

Effects of variations in carbon content and micro-structure on the stress-rupture properties of a liquid-phase-sirztered, Izeut-resistunt alloy were studied. Using the powder rnetallurgy technique, specimens could be produced having stress-rupture profierties equivalent to or better than those of the alloy in wrought form. In addition, sintered specimens were easily hot worked even when carbon contents were as high as I pct. Correlations between stress-rupture properties and micro structure were obtained in some cases. IT is well known that many alloys used in high-temperature service are quite complex both from the standpoint of chemical composition and microstruc-ture. During the development of these alloys their complexity has in some cases led to treatment schedules which, while practical, often do not fully utilize available alloying elements. For example, in some alloys, massive carbides that form during ingot practice may never be dissolved by reasonable solution treatments and therefore are unavailable for subsequent precipitation hardening, Ref. 1. This investigation was undertaken to determine whether the powder metallurgy method of consolidation might provide distinct advantages over the conventional melting method. First, segregation of alloying elements might be eliminated or reduced and thus a more efficient use of these elements obtained. Second, the structures produced in powder specimens might differ considerably from those normally seen in castings, which would perhaps result in better response to subsequent mechanical or thermal treatments. If these results could be achieved, it was felt that both forgeability and stress-rupture properties might be improved. The alloy used in this investigation was S-816 produced by powder metallurgy methods. The influence of carbon content over the range of 0.1 to 1.0 wt pct was studied for the alloy in the as-sintered condition and after three additional treatments involving heat treatment, hot swaging, and combinations thereof. EXPERIMENTAL Standard S-816 has the composition shown in Table I. It is a cobalt-base alloy having a nominal carbon content of 0.4 pct and is classified as a precipitation-hardening alloy. This alloy was chosen because it is representative of a class of heat-resistant alloys and because adequate information was available concerning its response to various treatments and its subsequent properties. For this study, -100 mesh alloy powder having essentially the same composition as shown in Table I but without the 0.4 pct C was used. Desired carbon variations, achieved by wet mixing the alloy powder with graphite, ranged from 0.1 to 1.0 wt pct. Specimens were hydrostatically pressed and then sintered in vacuum by slowly heating until incipient melting was observed. Sintering this way gave a liquid phase in the interstices of the powder particles and achieved reasonably high densities. The average density of as-sintered specimens was about 95 pct of wrought alloy density. In order to obtain various microstructures, some specimens were heat treated (solution treated for 24 hr at 2150°F, water quenched; aged 16 hr at 1400°F, air cooled); others were hot swaged at 2150 o F (50 pct reduction in area), while still others were hot swaged (50 pct reduction in area) and then given the above heat treatment. During hot swaging it was observed that forgeability was quite good even when specimens contained as much as 1.0 pct C. Specimens were evaluated by stress-rupture test-

Jan 1, 1962

By Charles L. Ross

A successful placer mine is being operated by the E. T. Fisher Co. on Rock Creek in the South Pass mining district at Atlantic City, Wyo. About 2,800 cubic yards of gravel is dug daily by a gasoline-driven dragline shovel with a 1 1/4-yard bucket and washed in a movable plant with a gold-dredge trommel and standard-dredge sluice boxes; the total cost is about 12 cents per cubic yard. The gold-bearing gravel occupies a narrow valley between two low ranges, of hills. The ground is covered by brush and willows, which are cleared of in the fall by burning after the leaves have dried. The elevation at the mine is 7,600 feet above sea level.

Jan 1, 1935

By Joseph Grumer

About a century ago Bunsen and his associates invented the famous burner that bears his name and was to become the ancestor of today's gas appliances. Over the years, Bunsen's invention became the starting point of a highly developed, practical technology that culminated in the gas industry as we now know it. However, it did not occur to the early workers to investigate the scientific potentialities of the new device, and as a result the science of gas-burner performance did not keep pace with the growing industry. It was with the objective of closing the rapidly widening gap between science and technology that the present research was undertaken Its immediate purpose was to provide basic information on the combustion characteristics of .fuel gases, in particular as they affect flashback, blowoff, and yellow tipping. Information obtained in the present research and contained within this report consists of the following: (1) Fundamental flashback and blowoff characteristics have been determined, it is believed, for all fuel-gas mixtures in which the gas industry may be interested. These are critical boundary velocity gradients for flames in free air, on burners with ports at room temperature and pressure. Burner aeration is characterized by the parameter, fraction of stoichiometric. These basic limits are explained, values are presented, and calculation procedure is given for deriving corresponding values of port loading and percent primary air (chs. I and II).

Jan 1, 1956

By J. E. Hawley

Abstract Spectrographic methods for the analysis of minor constituents such as platinum-group metals, gold, silver, and silica in palladium and platinum refinery sponge are described. These involve the conversion of the sponge metals to the black form by reduction with high purity aluminum filings in either acid or alkaline media. Standards of known composition are prepared in the same manner from either refinery or spectrographically standardized sponge metals. Samples of the black metals are mounted in pellet form and a multisource spark discharge used for excitation. The range of concentrations of impurities studied are those common to refinery samples. Excellent reproducibility of intensity ratios using major constituents as internal standards, is demonstrated and two methods have noted by which the accuracy of the procedures are shown to be of the order of 3 per cent, on the basis of synthetic preparations. Introduction During the past two years an investigation has been carried out in the Spectrographic Laboratory, Queen's University, to determine the suitability of modern spectrographic techniques for the precise analysis of the platinum-group metals palladium, platinum, rhodium, iridium, and ruthenium in the form of refinery sponge analyzing about 99 per cent of the major constituent.

Jan 1, 1951

By A S. Fogliata, L Bengochea, G Mas, J E. Lazarte

The Culampajß auriferous district is located in the northern sector of the eastern edge of the homonymous hill, Catamarca Province, Argentina. Tajo Largo mine is situated in the southern flank of Las Minas gulch at an approximate height of 3.600 m above sea level. In the studied area main outcrops are orthogneiss rocks of Chango Real Formation. The ore mineral is native gold with a lesser amount of pyrite, chalcopyrite, haematite, limonite, malachite, azurite and covellite. These ore mineral assemblages are disseminated in quartz veins filling tension fractures in the host orthogneiss.Several types of inclusions have been recognised, including three phase H2O-CO2liq-CO2vap inclusions, polyphase inclusions with H2O-CO2 and one or more solid phases, and two phase aqueous inclusions. In the three phase H2O-CO2liq-CO2vap inclusions the Tmclath is about 1¦C and the CO2 liquid-vapour homogenisation occurs at 26 - 28¦C, to liquid phase. The homogenisation temperature of H2O-CO2 occurs at 365 - 380¦C in the aqueous phase. This set of data defined a solution with a salinity of 14, 4 wt per cent NaCl equivalent and a density of 0.84 g/cm3. In the two phase aqueous inclusions the melting temperature (Tm) of -5.4¦C and the eutectic point (Te) in -38¦C indicates a salinity of about 7.5 wt per cent NaCl equivalent, with the probable presence of Ca2+. Density of fluid is about 0.83 g/cm3. Homogenisation temperature ranges between 260¦ and 280¦C. The pressure, temperature and salinity of fluids in the polyphase inclusions suggest an early fluid of high density and high salinity. The three-phase fluid inclusions may be the result of an unmixing-phase separation of post magmatic hydrothermal fluid due to pressure decrease along fractures. It is suggested that the deposit was formed during the late magmatic hydrothermal stage genetically linked to granitic rocks and can be comparable with the intrusion-related gold system of Baker (2003).

Jan 1, 2008

By P Audet, D Doley

The mining industry often embraces mine closure criteria that require the reinstatement of predisturbance or even presettlement (ie historic) ecosystems. However, the extent and severity of disturbance associated with most mining activities mean that critical physical and biological characteristics are irreversibly altered. Consequently, it is rare that a reconstructed landscape can support ecosystems even close to the historic condition, and this rarity is reflected in the small number of mine leases that have been extinguished by attainment of such completion criteria. Novel ecosystems are defined as those in which some or all physical and biotic components are irreversibly different from the historic condition. Recognition of the concept of novel ecosystems allows mine closure criteria to be set according to attainable physical and biological conditions that provide safe, stable and manageable environments with acceptable ecological functions. We propose that a landscape that first maximises physical stability and economy yet will provide a range of environments for vegetation communities and fauna habitats that may be very different from those existing prior to a disturbance should be considered suitable alternatives to, eg targeting idealised historic environments. As a result, mine closure criteria should be established by detailed description of the best attainable physical conditions, with negotiated identification and testing of the most appropriate biological systems for the various parts of the reconstructed landscape. As a general practice, revegetation would use native, but not necessarily local species if the new physical environment is not conducive to the survival and growth of local species. These new ecosystems would need to be managed in perpetuity, although the intensity of management might be low if landscape design and engineering are combined with appropriate species introductions. Here, we suggest an abbreviated procedure that may be adapted in light of local conditions and circumstances for guiding decisions influencing the physical and biological properties of reconstructed landscapes that will enable novel ecosystems to meet realistic closure criteria.CITATION:Doley, D and Audet, P, 2014. Changing restoration priorities in the 21st century – opportunities for novel ecosystem design in mine closure, in Proceedings Life-of-Mine 2014 , pp 649–662 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

By C. M. Brinckerhoff

Much has been written in the mining technical magazines about the caving system. Many of these articles were published in the Transactions of the American Institute of Mining Engineers prior to World War II. In recent years little has been written on mining methods or on the detailed planning always required. Block caving had primarily been used to mine deep copper ores in Africa, the United States and in Chile, although other ores had been mined by this same system. Asbestos ore had been caved in Canada, tin ore in Bolivia, molybdenum ore in Colorado, iron ore in Wyoming and Sweden, and limestone in California.

Jan 1, 1984

By J Taguta, B. McFadzean, P. E. Ngoepe, M. G. Mulaudzi

Computational modelling methods and isothermal titration calorimetry (ITC) were employed to investigate the interaction of a pyrite surface with thiol collectors. Modelling work was conducted in the presence and absence of water. Microcalorimetry was employed to investigate the resultant energy of interaction pyrite as a result of mineral-collector interactions. Sodium ethyl xanthate (SEX), diethyldithiocarbamate (DTC) and diethyl dithiophosphate (DTP) were investigated in this study. The results showed that the calculated surface energies and morphologies for FeS2 showed that (100) and (111) are the most stable surfaces. The morphology also indicated the appearance of the (100) and (111) surface facets and no presence of others. The calculated adsorption energies between thiol collectors and the pyrite surface were always more exothermic than the experimentally determined ones. When comparing different ligand types with the same alkyl chain length, the heat of adsorption of diethyl-DTC was greater than that of ethyl xanthate and diethyl-DTP for pyrite. Experimentally, the diethyl DTP barely adsorbed onto the pyrite surface and this may be due to a different mechanism of action. In computational calculations, water adsorption was found to reduce the reactivity of the Fe atom for the interaction with thiol collectors, and bring the adsorption energies closer to the magnitude of the experimental values. Keywords: Computational modelling, microcalorimetry, experimental and thiol collectors, adsorption energies

Jan 1, 2020

By Henry M. Harris

Low-carbon shales from 65 deposits and 11 sources of coal-mine waste in western Oregon and Washington were tested in a rotary kiln for their suitability as raw material for expanded aggregate. Shales from 41 sources bloated enough to produce crushed, expanded aggregates, weighing less than 65 pounds per cubic foot in the preliminary tests. The samples were judged on the basis of processing qualities, physical properties, and size and uniformity of the source. Nine low-carbon shale deposits and three coal-mine waste sources were selected for more extensive bloating tests and for examination of the expanded aggregates in concrete shapes. Composite samples from these 12 sources and from 2 commercial operations, when processed for testing in concrete shapes, had bulk densities ranging from 37.S to 72.9 pounds per cubic foot. Damp-cured concrete shapes made with these aggregates had bulk densities ranging from S6 to 119 pounds per cubic foot, and all but three of the lightweight concretes had crushing strengths ranging from 3,270 to 6,810 p.s.i. Properties of the lightweight concretes were compared with those of concrete shapes made with commercial aggregates, and with sand and gravel.

Jan 1, 1962

By Q Gong, J Li, J Zhao, Y Zheng

Excavation by tunnel boring machines (TBMs) offers many advantages over conventional excavation methods, in terms of safety level, working environment, advance rate and overall cost. While TBMs have been extensively used in civil tunnel construction, they are also viewed as a competitive alternative to the drill-and-blast method for underground mining, attracting increasing attention from the mining industry. This paper presents an overview and general assessment on applications of TBMs in mines, by reviewing more than 60 TBM applications in underground/open pit coal and hard rock mines around the world. The projects range from the early exploratory trials of TBMs in mines in Germany, England, South Africa and America in the 1960s and 1970s, to the ongoing projects in Australia, China and Chile. The paper focuses on the geological compatibilities, the problems encountered, the solutions undertaken and the lessons learned from those projects. The paper summarises the progress made in the past and highlights the challenges faced by TBMs in mining due to complex ground conditions and geometrical requirements. With the technological advances of TBM and experiences gained in the past, more applications of TBMs are expected in underground coal and hard rock mines.CITATION:Zheng, Y, Gong, Q, Li, J and Zhao, J, 2014. A review of the applications of tunnel boring machines in mines, in Proceedings 15th Australasian Tunnelling Conference 2014, pp 691–704 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By Tomek Ulatowski

INTRODUCTION In 1974, Industrial Miners Mexico, S.A. (IMMSA), agent for the borrowers, was the largest privately-held mining, smelting, and refining company in Mexico (accounting for 32% of Mexico's nonferrous metal and coal production in 1974), the fourth largest company in terms of sales, and the second most profitable company in Mexico, excluding government wholly-owned and operated industries. The company was engaged in the mining, smelting and refining of coal, copper, fluorite, gold, lead, silver, zinc and related by-products for domestic consumption and export. A combination of favorable factors led IMMSA to propose an investment plan amounting to US$286 million for 1974 through 1978, of which US$150 million was to be financed. These factors included: Substantial profits in 1973 and 1974 Positive near-term outlook for metal prices Success of the reinvestment program in increasing productivity Substantial additions to proved reserves during 1973-1974 and Fiscal incentives provided by the Mexican government to stimulate investment in the mining industry. The primary purpose of the investment program was to construct a new electrolytic zinc refinery and to expand and modernize many of the company's existing mining and refining facilities. THE BORROWER Company History Compania Miners Mexico, S.A. was incorporated in the city of Monterrey in 1918 as a wholly-owned subsidery of ASARCO Inc. (formerly American Smelting and Refining Company, New York) for the purpose of mining and processing non-ferrous metals and related products. In compliance with the Government's Mexicanization program, ASARCO Inc. divested itself of 51% of its equity in Compania Miners Asarco, S.A. on June 30, 1965. Subsequently, ownership in the divested share was apportioned as follows: 15% ownership in Compania Miners Asarco, S.A. to a group of private investors, and 36% in trust for subsequent public sale. The company's name was changed to Asarco Mexicana, S.A. in 1965. Mexican ownership in Asarco Mexicans, S.A. was increased to 51% in 1967, following the purchase of the 36% share ownership held in trust, and then to 66% in 1974 when ASARCO Inc. divested itself of an additional 15% of its holdings in Asarco Mexicans, S.A. Following its 1974 divestiture of 15% of Asarco Mexicans, S.A., ASARCO Inc's ownership in Asarco Mexicana, S.A. was reduced to 34%. In 1974, the company changed its name for the second time to Industrial Miners Mexico, S.A. (IMMSA). Fiscal Agreement IMMSA entered into a fiscal agreement with the Mexican government in 1969. The agreement, which was renewed in 1974, provided for 100% of the production and export tax corresponding to the federal government with a minimum of 50% of the amount refunded to be reinvested in fixed assets. Further, the agreement permitted the company to

Jan 1, 1985

By D. Shink

A small scale continuous flotation cell was designed and constructed at Noranda Technology Centre to develop a mobile testing flotation circuit located next to the production circuit. This mobile small scale flotation pilot plant can easily and economically be set up at any circuit in a mill and used to evaluate and predict plant performance against a given flotation condition. The main feature of the cell, beside the provisions of automatic pulp level and feed rate control, is to provide a reduced surface to volume ratio approaching to that of an industrial machine. This paper describes the basic design and the results of various testwork carried out to date including aeration, conditioning, reagents, recirculation, flotation gas, etc. are presented in comparison with the plant production results.

Jan 1, 1992

By J. P. Messervey

Dr. K. A. Clark: No one will doubt the statement of fact that, during drilling operations through the bituminous sand beds in the Mildred-Ruth Lakes area, the core-barrel was found to contain bitumen with minor amounts of sand instead of bituminous sand. But many will doubt the interpretation of this fact as meaning that beds of bitumen occur interstratified with the bituminous sand beds. They will prefer to hold faith in the laws of physics, which deny that sand will float on oil or that fluid under pressure will not flow away through a permeable medium, until it is proved that the appearance of the oil in the core-barrel was not due to circumstances surrounding the drilling of the bituminous sand beds. The implication of the interpretation that sand is floating on oil is clear and it is unacceptable. Bituminous sand is unconsolidated sand more' or less saturated with a viscous oil. It is as difficult to conceive of bituminous sand lying on top of a body of the viscous oil as it is to conceive of unconsolidated sand more or less saturated with water lying on top of a body of water. The only difference between the two concepts is that the oil is viscous whereas the water is fluid. Oil-soaked sand placed on viscous oil would, when released, sink through the oil slowly, whereas water-soaked sand would sink through the water quickly.

Jan 1, 1947

By Arash Khosravifar

One of our research thrusts at Portland State University (PSU) centers on developing design guidelines for pile foundations in liquefiable, laterally spreading grounds. This research has been primarily sponsored by the DFI Committee Project Fund (CPF) program through four awards, totaling nearly $240,000 in financial support. DFI contributed half of this financial support, while the other half was contributed in-kind by PSU and DFI Project Advisory Board members. Leveraging the CPF funds, we secured an additional $550,000 in financial support from the National Science. Foundation (NSF), which has enabled our research group to continue exploring this topic and contributing to the broader engineering community's understanding of the behavior of pile foundations in liquefiable soils. The CPF funds have fostered collaborations with practitioners and researchers beyond PSU. Notable examples include collaborative research involving data from five large-scale centrifuge tests on pile-supported wharves by Steve Dickenson, Ph.D., New Albion Geotechnical; Nason McCullough, Ph.D., Jacobs Engineering and Scott Schlechter, Geotechnical Resources, as well as 1-g shake table tests of bridge pile shafts conducted by Professors Ahmed Elgamal, Ph.D., and Ahmed Ebeido, Ph.D., of the University of California, San Diego. In addition to these collaborations, our research has benefited from industry-university partnerships formed through the involvement of DFI Project Advisory Board members. Their support and feedback ensure that our research products are practical and imple- mentable in real-world projects. The impact of the CPF funds extends to supporting graduate students' theses, which were the basis for 17 technical publications. Some of these publications are expected to have a significant impact on the industry. For instance, our 2018 DFI Journal paper, co-authored by former master's student Jonathan Nasr, cur- rently with the Army Corps of Engineers, has been cited in the 2022 British Columbia Supplement to Canadian Highway Bridge Design Code S6:19. A noteworthy product of our study is a step-by-step design procedure for pile- supported wharf structures subjected to the combined effects of lateral spreading and inertial loads, outlined in a 2022 American Society of Civil Engineers' (ASCE) Journal of Geotechnical and Geo- environmental Engineering paper co- authored by former doctoral student Milad Souri, Ph.D., PE, Geotechnical Resources.

Nov 1, 2023

By C. W. Kovach, A. Moskowitz

Studies were undertaken to investigate the effects of manganese content on the machinability and other Properties of a free machining martensitic stainless steel (AISI Type 416). Machinability was found to be significantly improved in steels of high manganese content, and a direct relationship was obtained between machinability and steel Mn:S ratio. As the manganese content of the steel increases, the sulfide Phase present changes from CrS to (FeMn)Cr2S4 to (MnFeCr)S, and finally to MnS. The average sulfide inclusion hardness decreases through the same range of increasing manganese content. The mechanism for machinability improvement is discussed in terms of a soft ductile sulfide affecting deformation in the secondary shear zone. Type 416 containing relatively high manganese for improved machinability shows good general properties. The effects of increasing manganese content on mechanical properties, cold formability, and corrosion resistance are described. THE addition of sulfur is commonly used to improve the machinability of stainless steels. However, little attention has been paid in the past to the composition and characteristics of the sulfur-containing phase or phases present in these resulfurized steels. Recent information on the properties of sulfide phases, and their role in metal cutting, suggests that variations in these phases could have critical effects on machin-ability, as well as important effects on formability and other properties such as corrosion resistance. Manganese, chromium, and iron are strong sulfide forming elements present in stainless steels! of these, manganese has the greatest sulfide forming tendency and iron the least.1"1 The manganese content of resul-furized 13 pct Cr steels, often about 0.5 pct, can be insufficient or only barely sufficient to combine with the sulfur that is present; thus, the precise level of manganese can strongly influence the nature of the sulfide phase. Sulfide phases which may be present in stainless steels have been reported to include CrS, a spinel-type sulfide, chromium-rich manganese sul-fide, and manganese Sulfide.5,6 Detailed phase relationships for the Fel3Cr-Mn-S system have been reported by the present investigators,7 and a portion of this work will be referred to subsequently in this paper. Recent work by Kiessling6 and Chao et a1.8 has shown that sulfide phases can display wide variations in hardness, and may undergo considerable plastic deformation under isostatic loading.9-12 Early theories of metal cutting attributed the influence of sulfur to a lubricating effect. It is now apparent that the influence of the nonmetallic inclusions and their properties on crack initiation, deformation in the shear zones, and boundary films must also be considered in relation to the machining process. This paper presents the results of studies conducted to relate machinability to the various sulfide phases which occur in stainless steels. This work has led to the development of alloys with improved machinability, and has generated information on the effects of inclusions on metal cutting processes. Effects of sulfide inclusions and steel composition on other important metallurgical properties are also discussed. MATERIALS For drill machinability and inclusion studies, 10 lb laboratory heats were melted in an air induction furnace. These heats were made with sulfur contents be tween 0.10 and 0.50 pct and manganese contents be tween 0.05 and 3.0 pct. Residual elements were added to the heats in amounts typical for commercial steels. The typical compositional range covered by the heats is shown below: C Mn P S Si Ni Cr Mo Cu N 0.10 0.05 0.007 (M0 0.40 0.40 13.0 0.20 0.10 0.03 3.0 0750 The laboratory ingots were forged in the temperature range of 1800" to 2100°F to 3/4-in. sq bars, and all bars tempered to a hardness aim of 200 Bhn prior to testing. Because of differences in composition and tempering response, the tempered bars showed some variation in hardness (175 to 275 Bhn) as well as variations in delta ferrite content (0 to 50 pct). Composition, hardness, and delta ferrite content were considered in the analysis of the machinability data. Additional tests involving tool-life evaluation and determination of other properties were conducted on materials from commercially melted and processed 15-ton electric furnace heats. TESTS AND PROCEDURES Machinability of the laboratory heats was evaluated in a drill test. In this test, 1/4-in. diam holes, 0.4 in. deep, were drilled alternately in a test bar and in a standard bar for a total of four holes in each. This sequence was repeated three times using a freshly sharpened drill each time. The average time required to drill a hole in the test bar was compared to that for the standard bar. A drill machinability rating was assigned to the test bar relative to a rating of 100

Jan 1, 1970

By Robert S. Hedin

Passive methods of treating mine water use chemical and biological processes that decrease metal concentrations and neutralize acidity. Compared with conventional chemical treatment, passive methods generally require more land area, but use less costly reagents and require less operational attention and maintenance. Currently, three types of passive technologies exist: aerobic wetlands, organic substrate wetlands, and anoxic limestone drains. Aerobic wetlands promote mixed oxidation and hydrolysis reactions, and are most effective when the raw mine water is net alkaline. Organic substrate wetlands promote anaerobic bacterial activity that results in the precipitation of metal sulfides and the generation of bicarbonate alkalinity. Anoxic limestone drains generate bicarbonate alkalinity and can be useful for the pretreatment of mine water before it flows into a wetland. Rates of metal and acidity removal for passive systems have been developed empirically by the U.S. Bureau of Mines. Aerobic wetlands remove Fe and Mn from alkaline water at rates of 10-20 and 0.5- 1.0 g. m-2? d-1, respectively. Wetlands with a composted organic substrate remove acidity from mine water at rates of 3-9 g. m-2? d-1?. A model for the design and sizing of passive treatment systems is presented in this report.

Jan 1, 1994

By HENRY M. HOWEL

1. Introduction.-The first part of this papers treats of the causes and the restraining of piping in steel ingots; the second& considers the causes and the restraining of -segregation; and the third proposes certain precautions in engineering specifications concerning these two defects. Into their causes I have looked carefully, with the purpose of arriving at rational methods of restraining them, and at efficient ways of detecting. and measuring the harm which they cause, so as to benefit the public by reducing this harm at once effectively and with the least expense to the manufacturer, and therefore in the end with the least expense to the consumer. In Part I., I infer that the pipe is chiefly due to what I, call the virtual expansion of the outer walls of the ingot in the early part of the freezing. I find that the upper and smooth-faced part of the pipe probably forms while the interior is still molten, but that the lower, steep, and crystal-faced part probably forms in metal which is already firm. Of the five causes which may co-operate to limit the depth of the pipe, I find that three-blow-holes, sagging, and the progress of freezing from below upwards-are usually effective. I find that the pipe may be lessened by casting (1) in wide ingots,; (2) in sand molds, especially if these are pre-heated (this is rarely expedient); (3) at the tops instead of at the bottom; (4) slowly; (5) and with the large end up; (6) by the use of a sinking-head or other means of retarding the cooling of the top; (7) by permitting blow-holes to form; and (8) by liquid compression.) Most of these I consider in some detail, and in particular I dwell on the advantages of casting with the large end up, and I propose certain administrative arrangements to permit this.

Mar 1, 1907