Search Documents

By J. Fletcher Smoak

The value of abrasive materials consumed in the United States increased 37% in value over that of 1983 to $439 million; of which, 58% was manufactured abrasives, 36% was industrial diamond (natural and synthetic), and 6% was natural abrasives. Production value of natural abrasives, which consist of crude tripoli, special silica stone, garnet, and emery, increased 4% Production of crude tripoli, a finely disintegrated chert, increased 12% in quantity and 8% in value. Shipments of processed tripoli increased only 3% in quantity but increased 16% in value, with large increases occurring in both major end-use categories. Production of garnet, an abundant iron-aluminum silicate, decreased slightly in quantity and value after posting continued increases in quantity and value since 1980. There was a significant decrease in the quantity and [ ]

Jan 1, 1985

By Gordon T. Austin

The combined value of production of natural abrasives, which includes tripoli, special silica stone, garnet, staurolite, and emery, increased about 9% in 1988. In the case of emery, the increase was due to an increase in unit value of the material produced. The increase in the value of garnet and staurolite production was simply the result of an increase in the quantity of materials produced. However, special silica stone experienced both an increase in unit value and quantity produced. The nonmetallic manufactured abrasives industry, which includes only silicon carbide and fused aluminum oxide in the reported statistics, enjoyed the best production year since 1981 in terms of total quantity produced. Production increased 22% in quantity and 16% in value com-pared with those of 1987.

Jan 1, 1990

By Gordon T. Austin

The combined value of production of natural abrasives, which include tripoli, special silica stone, garnet, staurolite, and emery, decreased about 24% in 1992. The decrease in the value of tripoli production was the result of a decrease in total production. Emery decreased owing to a decrease in the volume of the material produced. Special silica stone experienced a significant increase in unit value and decrease in the quantity produced. Garnet showed a 6 % increase in quantity and a 36 % decrease in unit value. Staurolite decreased about 27 % in the quantity produced and value compared with those of 1991. The fused aluminum oxide industry showed a slight increase in the quantity produced and a 4 % increase in the value of production. The silicon carbide industry saw a 7 % increase in the quantity produced and a 10 % increase in the value of production. Combined, the industries increased 4 % in quantity and 6 % in value compared with those of 1991.

Jan 1, 1992

By Gordon T. Austin

The combined value of production of natural abrasives, which include tripoli, special silica stone, garnet, staurolite, and emery, increased about 4% in 1990. The decrease in the value of tripoli production was the result of a decrease in total production. Emery decreased owing to a decrease in the volume of the material produced. Special silica stone experienced a decrease in unit value and in the quantity produced. Garnet showed an 8 % increase in quantity and an 8 % increase in unit value. Staurolite increased about 38 % in the quantity produced, and the value of production increased about 36 %. The fused aluminum oxide industry showed a 12 % decline in the quantity produced and a 13 % decline in the value of production. The silicon carbide industry saw a 47 % decrease in the quantity produced and a 23 % decrease in the value of production. Combined, the industries decreased 17 % in quantity and value compared with those of 1990.

Jan 1, 1993

By Gordon T. Austin

The combined value of production of natural abrasives, which include tripoli, special silica stone, garnet, staurolite, and emery, increased about 4% in 1990. The increase in the value of tripoli production was the result of an increase in the unit value. Emery increased owing to an in? crease in the volume of the material produced and an increase in the unit value. Special silica stone experienced a decrease in unit value and an increase in the quantity produced. Garnet showed a 10% in? crease in quantity and a 73% increase in unit value. Staurolite decreased about 8% in the quantity produced, and the value of production decreased about 10%. The fused aluminum oxide industry showed a 5% decline in the quantity produced and in the value of production. The silicon carbide industry saw a 10% decrease in the quantity produced and a 9% decrease in the value of production. Production for both industries decreased 7% in quantity and value compared with those of 1989.

Jan 1, 1993

By James D. Cooper

COMBINED tonnage or natural abrasive materials sold or used in the United States in 1962 was 10 percent greater than that of 1961 and value was 9 percent higher. Production of crude artificial abrasives in the United States and Canada was up 14 percent in volume and 9 percent in value. Value of grinding-wheel sales increased 13 percent, and the value of coated-abrasives sales was up 10 percent. The value of imports and reexports declined, while the value or exports increased. [ ]

Jan 1, 1963

By Paul M. Ambrose

ADVANCES in mining and processing technology made it possible to reopen the De Beers diamond mine in South Africa, originally located in 1871 by Cecil Rhodes and closed in 1908. Radioactive material was used to indicate the efficiency of hydro-cyclones used in diamond concentration. Added interest was shown in recovering diamond from the sea off the coast of South-West Africa. Production of crude artificial abrasives declined because demand was paritally met by withdrawals from stocks. The value of graded grain-coated abrasives and grinding wheels surpassed those of 1962.

Jan 1, 1964

By NEFE AEWFW

Changes in the 1980 quantity and value of the sales of various natural abrasives, compared with the data for 1979, were of a mixed nature. Output of garnet and special silica stone products increased in both tonnage and value during the year, while emery and tripoli-type materials production decreased in both tonnage and value. The reported quantity and value of sales of manufactured abrasive material-fused alumina and alumina-zirconia, silicon car-bidet and metallic iron and steel shot and grit-also decreased for 1980. [ ]

Jan 1, 1981

By J. Fletcher Smoak

Consumption of abrasive materials in the United States increased 22% in value over that of 1982 to $320 million; of which, 59% was manufactured abrasive, 35% was industrial diamond (natural and synthetic), and 6% was natural abrasive. Production value of natural abrasives, excluding industrial diamond, remained virtually unchanged. Production of crude tripol, a porous siliceous rock, decreased slightly; however, shipments of processed tripoli increased 13% in quantity and 32% in value. Production of garnet, an abundant iron-aluminum silicate, continued to increase primarily because of further increases in production from one plant that had completed an expansion program in late 1981. Production of special silica stone, both crude and finished, decreased in 1983 because of reduced demand for oilstones

Jan 1, 1984

By Gordon T. Austin

The combined production value of natural abrasives, which consist of tripoli, special silica stone, garnet, and emery, decreased in 1986. Shipments of processed tripoli increased slightly in quantity and 20% in value. Production of garnet, a common iron- aluminum-silicate mineral, decreased 12% in quantity and value. There was a 4% increase in the quantity and an 11% increase in the value of refined garnet shipped when compared with 1985 shipments, a new record high. Production of crude special silica stone decreased 7% in quantity and slightly in value, and shipments of finished special silica stone products decreased slightly in quantity and increased 229% in value. Production of emery, an impure aluminum oxide, increased 77% in quantity and increased 269% in value of product mined and shipped. [ ]

Jan 1, 1988

By Henry P. Chandler

THE year 1950 was one of increased activity in almost all branches of the abrasives industry, with nearly all abrasive materials showing a marked increase in tonnage and value. New records were made In the production of tripoli, ground sand and sandstone, pumice and pumicite, and garnet. Total production of crude artificial abrasives in the United States and Canada increased 17 percent in tonnage and 30 percent in value. Imports of industrial diamonds increased 100 percent in total value and 72 percent by weight, the 1950 importation being the largest since 1944. Imports of corundum increased 76 percent in tonnage and 4 percent in value.

Jan 1, 1953

By Richard P. Hight

Abrasives include the substances, natural or artificial, that are used to grind, polish, abrade, scour, clean, or otherwise remove solid material, usually by rubbing action but also by impact (pressure blasting for example). They do not include abrasive tools, for instance, lathe tools and files--or polishing agents such as waxes, which act by filling pores. Detergents and cleaners whose action is chemical rather than physical are omitted al- though some chemical-action polishes and cleaners may also contain solid abrasives, for example, many automobile and metal polishes. General Considerations The most important physical properties of materials that qualify them for use as abrasives are hardness, toughness (or brittleness), grain shape and size, character of fracture or cleavage, purity or uniformity. For making bonded abrasive products such as grinding wheels, additional important factors are stability under high heat and bonding characteristics of grain surfaces. The economic factors of cost and availability are always important. No one single property is paramount for any use. For some uses extreme hardness and toughness are needed, as in diamonds for drill bits; for others, the factors of greatest importance are hardness and ability to break down slowly under use, to develop fresh cut- ting edges when grains become worn-for example: in garnet for sandpaper neither highly cleavable or friable grains nor extremely tough grains are wanted. For still other uses, great hardness is objectionable; for example, abrasives for dentifrices and for glass-cleaning soaps. For the most efficient use in the more critical applications, the different types of abrasives are rarely completely interchangeable; thus, while crushed quartz and garnet are both used in sandpaper, the papers are not at all interchangeable in their use applications. In the last analysis, the choice of a high grade abrasive depends upon the quality and quantity of work done by the abrasive per unit of cost. Initial cost of an artificial abrasive may be much greater than that of a natural abrasive but the artificial abrasive may do so much better work than the natural one, and do it so much faster that the ultimate cost will be less. It is for this reason that artificial abrasives have largely replaced natural abrasives. Abrasive Value Mineralogical hardness or "scratch" hardness as expressed in Mohs' scale is an important property in evaluating abrasive materials, but, as noted before, it is only one of several essential properties. The mineral hardness of pure crystal almandite garnet is about 7.5, but if the crystal is crossed by incipient fracture planes, or if it contains inclusions of other minerals, the apparent or useful hardness may be much lower. While the quartz grains in a sandstone have a hardness of 7, the bond holding the grains together may be so weak that the stone is valueless as a commercial abrasive. In artificially bonded wheels and stones, the hardness, strength, and character of the bond are fully as important as the hardness of the abrasive grains. Thus, in an overall consideration of abrasive hardness of loose abrasive grains, both "scratch" hardness and toughness must be considered. In naturally or artificially bonded abrasive stones, bond characteristics are a third factor, which is most important. The problem of abrasive hardness is further complicated by the inadequacies of methods of testing hardness and of expressing relative values. The Mohs' scale is inadequate both because the methods of testing are very crude and

Jan 1, 1975

By Raymond B. Ladoo

Abrasives include the substances, natural or artificial, that are used to grind, polish, abrade, scour, clean or otherwise remove solid material, usually by rubbing action but also by impact (sandblasting, for example). They do not include abrasive tools-for instance, lathe tools and files-or polishing agents such as waxes, which act by filling pores. Detergents and cleaners whose action is chemical rather than physical are omitted although some chemical-action polishes and cleaners may also contain solid abrasives; for example, many automobile and metal polishes. General Considerations The most important physical properties of materials that qualify them for use as abrasives are hardness, toughness (or brittleness), grain shape and size, character of fracture or cleavage, purity or uniformity. For making bonded grain abrasives such as grinding wheels, additional important factors are stability under high heat and bonding characteristics of grain surfaces. The economic factors of cost and availability are always important. No one single property is paramount for any use. For some uses extreme hardness and toughness are needed, as in diamonds for drill bits; for others, the factors of greatest importance are hardness and ability to break down slowly under use, to develop fresh cutting edges when grains become worn-for example, in garnet for sandpaper, neither highly cleavable or friable grains nor extremely tough grains are wanted. For still other uses, great hardness is objectionable; for example, abrasives for dentifrices and for glass-cleaning soaps. For the most efficient use in the more critical applications, the different types of abrasives are rarely completely interchangeable; thus, while crushed quartz and garnet are both used in sandpaper, the papers are not at all interchangeable in their use applications. In the last analysis, the choice of a high-grade abrasive depends upon the quality and quantity of work done by the abrasive per unit of cost. Initial cost of an artificial abrasive. may be much greater than that of a natural abrasive but the artificial abrasive may do so much better work than the natural one, and do it so much faster, that the ultimate cost will be less. It is on this basis that artificial abrasives have largely replaced natural abrasives for grinding metal. Classification Abrasives may be divided into two general classes, natural and manufactured. The former includes all rocks and minerals used for abrasive purposes without chemical or physical change other than crushing, shaping or bonding into suitable forms. Manufactured or artificial abrasives are made either by heat or chemical action from metals or mineral raw materials. On page 2 is a list of the most important abrasives, classified as to inherent types and as to forms in which they are used industrially. For most types of use there are manufactured products that can be substituted for the natural products, usually at higher initial

Jan 1, 1960

By Richard P. Hight

Abrasives include the substances, natural or artificial, that are used to grind, polish, abrade, scour, clean, or otherwise remove solid material, usually by rubbing action but also by impact (pressure blasting for example). They do not include abrasive tools, for instance, lathe tools and files-or polishing agents such as waxes, which act by filling pores. Detergents and cleaners whose action is chemical rather than physical are omitted although some chemical-action polishes and cleaners may also contain solid abrasives, for example, many automobile and metal polishes. General Considerations The most important physical properties of materials that qualify them for use as abrasives are hardness, toughness (or brittleness), grain shape and size, character of fracture or cleavage, purity or uniformity. For making bonded abrasive products such as grinding wheels, additional important factors are stability under high heat and bonding characteristics of grain surfaces. The economic factors of cost and availability are always important. No one single property is paramount for any use. For some uses extreme hardness and toughness are needed, as in diamonds for drill bits; for others, the factors of greatest importance are hardness and ability to break down slowly under use, to develop fresh cutting edges when grains become worn-for example: in garnet for sandpaper neither highly cleavable or friable grains nor extremely tough grains are wanted. For still other uses, great hardness is objectionable; for example, abrasives for dentifrices and for glass-cleaning soaps. For the most efficient use in the more critical applications, the different types of abrasives are rarely completely interchangeable; thus, while crushed quartz and garnet are both used in sandpaper, the papers are not at all interchangeable in their use applications. In the last analysis, the choice of a high grade abrasive depends upon the quality and quantity of work done by the abrasive per unit of cost. Initial cost of an artificial abrasive may be much greater than that of a natural abrasive but the artificial abrasive may do so much better work than the natural one, and do it so much faster that the ultimate cost will be less. It is for this reason that artificial abrasives have largely replaced natural abrasives. Abrasive Value Mineralogical hardness or "scratch" hardness as expressed in Mohs' scale is an important property in evaluating abrasive materials, but, as noted before, it is only one of several essential properties. The mineral hardness of pure crystal almandite garnet is about 7.5, but if the crystal is crossed by incipient fracture planes, or if it contains inclusions of other minerals, the apparent or useful hardness may be much lower. While the quartz grains in a sandstone have a hardness of 7, the bond holding the grains together may be so weak that the stone is valueless as a commercial abrasive. In artificially bonded wheels and stones, the hardness, strength, and character of the bond are fully as important as the hardness of the abrasive grains. Thus, in an overall consideration of abrasive hardness of loose abrasive grains, both "scratch" hardness and toughness must be considered. In naturally or artificially bonded abrasive stones, bond characteristics are a third factor, which is most important. The problem of abrasive hardness is further complicated by the inadequacies of methods of testing hardness and of expressing relative values. The Mohs' scale is inadequate both because the methods of testing are very crude and

Jan 1, 1983

By William W. Wellborn

Abrasives are substances both natural and synthetic that are used to grind, polish, abrade, scour, clean, or otherwise remove solid material usually by rubbing action (as in a grinding wheel), but also by impact (pressure blasting). Facts about the discovery, early use, adaptation, and development of abrasives prior to the 20th century are few. From the sparse, earliest information that is available, it would appear that the science of abrasives began when, to fashion his tools, man began to select certain kinds of rocks in preference to others because of their peculiar properties. There is evidence that stones were sawed by some sort of grinding machine as early as 4000 BC in Egypt. The real expansion of abrasives use coincided with the beginning of metallurgy in the Middle East around 2000 BC. The earliest confirmed use of abrasives for grinding metal comes from a steel dagger found along with a sharpening stone which was dated at about 1500 BC. Natural and manufactured abrasive substances play an important role in fashioning and finishing numerous products with a wide variety of end-use applications. The mining and preparation of crude, natural abrasives for their markets and the manufacture of synthetic and other abrasive materials contribute significantly to the US economy (Table 1). In addition, just as sawing to specific dimensions enhanced the value of the Egyptian stone, the use of abrasives in fabrication of modem products, and the addition of abrasives to others, add value. GENERAL CONSIDERATIONS The most important physical properties of materials that qualify as abrasives are hardness, toughness (or rigidity), grain shape and size, character of fracture (or cleavage), and purity (or uniformity). To fabricate bonded abrasive products such as grinding wheels, additional considerations include stability under high heat and bonding characteristics of grain surfaces. The economic factors of cost and availability are always important. No one singular property is paramount for any use. For some applications extreme hardness and toughness are needed, as in diamonds for drill bits. For other uses, factors of greatest importance are hardness and ability to break down slowly and, in the process, develop fresh cutting edges when grains become worn. In garnet sandpaper, for example, highly cleavable, friable, or extremely tough grains are not desirable. For other uses, extreme hardness may be objectionable. Abrasives for dentifrices and for glass-cleaning soaps are cases in point. For the most efficient uses in more critical applications, different types of abrasives are rarely completely interchangeable. While crushed quartz and garnet are both used in sandpaper, the two abrasives are not at all interchangeable in their applications. In the final analysis, the choice of a high-grade abrasive depends upon the quality and quantity of work performed by the abrasive per unit of cost. Initial cost of an artificial abrasive may be much greater than that of a natural abrasive, but the artificial mineral may do so much better work and do it so much faster that the ultimate cost is less. It is for this reason that artificial abrasives have largely replaced natural abrasives.

Jan 1, 1994

By Steven W. Hunt, Glen R. Frank

Assessment of abrasivity and cutter life are necessary to properly manage risks when tunneling in mixed face ground which includes ground with cobbles and boulders. Maximizing cutter life requires: (1) abrasivity and strength parameters for soil matrix and rock clasts, (2) methods of combining both, (3) proper selection of cutters and (4) modified TBM operation including use of boulder detection methods from the TBM to help make operation decisions. This paper presents approaches for addressing these factors sufficiently to improve tunneling success in mixed-face and cobbly-bouldery ground. Current laboratory abrasivity testing will be assessed along with equivalent quartz content correlations to soil matrix and rock clast abrasivity. New approaches to combining abrasivity testing of both the soil matrix and rock clasts for various cobble and boulder volume ratios will be suggested to estimate cutter life and intervention intervals. Methods for detecting boulders and using detection data to modify TBM operations to minimize boulder impacts are provided.

Jun 13, 2021

By J. -P. Gisiger

On the basis of laboratory test results a comparison of various parameters (unconfined compressive strength, CERCHAR and LCPC abrasivity indexes, mineralogy) is presented and discussed in order to outline certain correlations between them. Samples cover a wide range of lithological types coming from various sites of tunnels. A partir de résultats d’essais de laboratoire, une comparaison de divers paramètres (résistance à la compression simple, indices d’abrasivité CERCHAR et LCPC, minéralogie) est présentée et discutée dans le but d’en tirer certaines corrélations. Les échantillons couvrent un large éventail de types lithologiques provenant de plusieurs sites de tunnels. Basierend auf Laborversuchen, werden verschiedene Gesteinseigenschaften (Druckfestigkeit, CERCHAR und LCPC Abrasionsindexe) präsentiert und Korrelationen aufgezeigt. Die untersuchten Proben verschiedenster Lithologien stammen aus mehreren Tunnelprojekten.

Jan 1, 2003

By Camila Peres Massola

Este trabalho avaliou o efeito da corrosão no desgaste de bolas de aço e de ferro fundido branco de alto cromo durante a moagem de minério de ferro, através de ensaios eletroquímicos e de desgaste em moinho de laboratório. Foi feita uma alteração no modo tradicional de realização do ensaio de polarização potenciodinâmica, utilizando polpa de minério de ferro a 70% de sólidos (em peso) no eletrólito. As curvas de polarização obtidas foram compatíveis com os resultados de desgaste, de modo que as curvas correspondentes aos metais na condição mais ativa estavam associadas às menores taxas de desgaste nos ensaios de moagem em laboratório, demonstrando que os ensaios de polarização realizados podem ser utilizados como indicativo do comportamento do metal na moagem de minério de ferro. Verificou-se que, nas condições avaliadas, o efeito da corrosão não foi significativo no desgaste dos corpos moedores, tanto de aço quanto de FFBAC.

Aug 16, 2017

By Marcelo Braga dos Santos

Visando o estudo da sinergia entre abrasão e corrosão concebeu-se um novo instrumento, permitindo a medição das forças que atuam sobre o contacto. O dispositivo consiste de um equipamento de micro-abrasão por esfera fixa dotada de uma célula de carga de três eixos, e uma célula eletroquímica. Uma membrana protetora flexível foi desenvolvida para isolar a célula de carga, situado no exterior da célula eletroquímica, da amostra no interior da célula. Uma solução corrosiva com partículas abrasivas é continuamente alimentada no contacto entre a amostra e a esfera. Os ensaios de abrasão-corrosão foram realizados simultaneamente em aços inoxidáveis e ferríticos. Também foram executados ensaios de micro-abrasão e corrosão separadamente para avaliar a capacidade do equipamento nos estudos da sinergia entre a micro-abrasão e a corrosão. Para as três condições de ensaios (micro-abrasão, corrosão e abrasãocorrosão) o equipamento se mostrou eficiente em evidenciar a variação nas propriedades do material com excelente repetibilidade. Para os aços austeníticos, as mudanças nas condições de carregamento nos ensaios de abrasão-corrosão induziram variações significativas nas curvas de polarização. A capacidade única de acompanhar as forças que atuam sobre o contato dos processos de abrasão-corrosão pode abrir caminho para novas descobertas sobre o estudo da sinergia na abrasão-corrosão, em especial, a dissipação de energia na interface quantificada através do coeficiente de atrito.

Aug 16, 2017

By M. T. Errington, P. C. Miller, W. E. Hardwick

Paper discusses in general terms the techno economic merits of various types of aerated biological reaction systems. The current status of the technology leaves many questions unanswered and hence the choice of the best system to employ is open to discussion. Reasons are given for the choice of the reactor system to be built and operated by Davy McKee. The pilot plant has been designed to provide answers to a number of the questions posed by this technology.

Jan 1, 1998