High-grade fire clays can withstand temperatures of 1,775 °C (3,227 °F), but to be referred to as a "fire clay" the material must withstand a minimum temperature of 1,515 °C (2,759 °F).[2] Fire clays range from flint clays to plastic fire clays, but there are semi-flint and semi-plastic fire clays as well. Fire clays consist of natural argillaceous materials, mostly Kaolinite group clays, along with fine-grained micas and quartz, and may also contain organic matter and sulphur compounds.
Fire clay is resistant to high temperatures, having fusion points higher than 1,600 °C (2,910 °F); therefore it is suitable for lining furnaces, as fire brick, and for manufacture of utensils used in the metalworking industries, such as crucibles, saggars, retorts and glassware. Its stability during firing in the kiln means that it can be used to make complex items of pottery such as pipes and sanitary ware.
Chemical compositionEdit
The chemical composition typical for fire clays are 23-34% Al2O3, 50-60% SiO2 and 6-27% loss on ignition together with various amounts of Fe2O3, CaO, MgO, K2O, Na2O and TiO2.[2] Chemical analyses from two 19th-century sources, shown in table below, are somewhat lower in alumina[3][4] although a more contemporary source quotes analyses that are closer.[5]
Unlike conventional brick-making clay, some fire clays (especially flint clays) are mined at depth, found as a seatearth, the underclay associated with coal measures.
ReferencesEdit
^"Calciners and Dryers in Mineral Industries" (Background Information for Proposed Standards). U.S. Environmental Protection Agency. 1985. pp. 3–48. EPA-450/3-85-025a.
^ abMinerals Zone, World Mineral Exchange. 2011-07-14 at the Wayback Machine Retrieved 2011-6-23.
^ abThorpe, Sir Thomas Edward (1890). A Dictionary of Applied Chemistry Volume I. Longmans Green & Company, London.
^ abKing, William B. (1878). King's Treatise on the Manufacture and Distribution of Coal Gas. self.
^ abShackelford, James F (2008). Ceramic and glass materials: structure, properties and processing. Springer. p. 121.
October 14, 2023
fire, clay, range, refractory, clays, used, manufacture, ceramics, especially, fire, brick, united, states, environmental, protection, agency, defines, fire, clay, very, generally, mineral, aggregate, composed, hydrous, silicates, aluminium, al2o3, 2sio2, 2h2o. Fire clay is a range of refractory clays used in the manufacture of ceramics especially fire brick The United States Environmental Protection Agency defines fire clay very generally as a mineral aggregate composed of hydrous silicates of aluminium Al2O3 2SiO2 2H2O with or without free silica 1 Furnace in fire clay Contents 1 Properties 2 Chemical composition 3 Extraction 4 ReferencesProperties EditHigh grade fire clays can withstand temperatures of 1 775 C 3 227 F but to be referred to as a fire clay the material must withstand a minimum temperature of 1 515 C 2 759 F 2 Fire clays range from flint clays to plastic fire clays but there are semi flint and semi plastic fire clays as well Fire clays consist of natural argillaceous materials mostly Kaolinite group clays along with fine grained micas and quartz and may also contain organic matter and sulphur compounds Fire clay is resistant to high temperatures having fusion points higher than 1 600 C 2 910 F therefore it is suitable for lining furnaces as fire brick and for manufacture of utensils used in the metalworking industries such as crucibles saggars retorts and glassware Its stability during firing in the kiln means that it can be used to make complex items of pottery such as pipes and sanitary ware Chemical composition EditThe chemical composition typical for fire clays are 23 34 Al2O3 50 60 SiO2 and 6 27 loss on ignition together with various amounts of Fe2O3 CaO MgO K2O Na2O and TiO2 2 Chemical analyses from two 19th century sources shown in table below are somewhat lower in alumina 3 4 although a more contemporary source quotes analyses that are closer 5 Fire clay compositions Thorpe 3 King 4 Shackelford 5 Stonebridge Eisenberg I Eisenberg II Newcastle 1 Newcastle 2 Newcastle 3 N ASiO2 65 10 89 8 64 7 51 1 47 6 48 6 58 1Al2O3 22 2 5 40 24 0 31 4 29 5 30 2 23 1MgO 0 18 0 09 0 40 1 54 0 71 1 91 1 00CaO 0 14 0 20 0 37 1 46 1 34 1 66 0 08Iron Oxides 0 18 0 09 0 40 4 63 9 13 4 06 2 40K2O 0 18 0 61 2 40 not given in the textExtraction EditUnlike conventional brick making clay some fire clays especially flint clays are mined at depth found as a seatearth the underclay associated with coal measures References Edit Calciners and Dryers in Mineral Industries Background Information for Proposed Standards U S Environmental Protection Agency 1985 pp 3 48 EPA 450 3 85 025a a b Minerals Zone World Mineral Exchange Archived 2011 07 14 at the Wayback Machine Retrieved 2011 6 23 a b Thorpe Sir Thomas Edward 1890 A Dictionary of Applied Chemistry Volume I Longmans Green amp Company London a b King William B 1878 King s Treatise on the Manufacture and Distribution of Coal Gas self a b Shackelford James F 2008 Ceramic and glass materials structure properties and processing Springer p 121 Retrieved from https en wikipedia org w index php title Fire clay amp oldid 1143579432, wikipedia, wiki, book, books, library,
