(See related pages)
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| Austenite | (γ phase in Fe-Fe3C phase diagram): an interstitial solid solution of carbon in FCC iron; the maximum solid solubility of carbon in austenite is 2.0 percent. (See page(s) 512; Sec. 9.2) |
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| Austenitizing | heating a steel into the austenite temperature range so that its structure becomes austenite. The austenitizing temperature will vary depending on the composition of the steel. (See page(s) 512; Sec. 9.2) |
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| α Ferrite | (α phase in the Fe-Fe3C phase diagram): an interstitial solid solution of carbon in BCC iron; maximum solid solubility of carbon in BCC iron is 0.02 percent. (See page(s) 512; Sec. 9.2) |
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| Cementite | the intermetallic compound Fe3C; a hard and brittle substance. (See page(s) 512; Sec. 9.2) |
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| Pearlite | a mixture of α ferrite and cementite (Fe3C) phases in parallel plates (lamellar structure) produced by the eutectoid decomposition of austenite. (See page(s) 512; Sec. 9.2) |
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| Eutectoid α cementite | cementite which forms during the eutectoid decomposition of austenite; the cementite in pearlite. (See page(s) 512; Sec. 9.2) |
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| Eutectoid (plain-carbon steel) | a steel with 0.8 percent C. (See page(s) 512; Sec. 9.2) |
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| Hypoeutectoid (plain-carbon steel) | a steel with less than 0.8 percent C. (See page(s) 512; Sec. 9.2) |
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| Hypereutectoid (plain-carbon steel) | a steel with 0.8 to 2.0 percent C. (See page(s) 512; Sec. 9.2) |
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| Proeutectoid cementite | cementite that forms by the decomposition of austenite at temperatures above the eutectoid temperature. (See page(s) 512; Sec. 9.2) |
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| Martensite | a supersaturated interstitial solid solution of carbon in body-centered tetragonal iron. (See page(s) 512; Sec. 9.3) |
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| Bainite | a mixture of α ferrite and very small particles of Fe3C particles produced by the decomposition of austenite; a nonlamellar eutectoid decomposition product of austenite. (See page(s) 513; Sec. 9.3) |
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| Spheroidite | a mixture of particles of cementite (Fe3C) in an α ferrite matrix. (See page(s) 513; Sec. 9.3) |
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| Isothermal transformation (IT) diagram | a time-temperature-transformation diagram that indicates the time for a phase to decompose into other phases isothermally at different temperatures. (See page(s) 513; Sec. 9.3) |
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| Continuous-cooling transformation (CCT) diagram | a time-temperature-transformation diagram that indicates the time for a phase to decompose into other phases continuously at different rates of cooling. (See page(s) 513; Sec. 9.3) |
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| Martempering (marquenching) | a quenching process whereby a steel in the austenitic condition is hot-quenched in a liquid (salt) bath at above the Ms temperature, held for a time interval short enough to prevent the austenite from transforming, and then allowed to cool slowly to room temperature. After this treatment the steel will be in the martensitic condition, but the interrupted quench allows stresses in the steel to be relieved. (See page(s) 513; Sec. 9.3) |
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| Austempering | a quenching process whereby a steel in the austenitic condition is quenched in a hot liquid (salt) bath at a temperature just above the Ms of the steel, held in the bath until the austenite of the steel is fully transformed, and then cooled to room temperature. With this process a plain-carbon eutectoid steel can be produced in the fully bainitic condition. (See page(s) 513; Sec. 9.3) |
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| Tempering (of a steel) | the process of reheating a quenched steel to increase its toughness and ductility. In this process martensite is transformed into tempered martensite. (See page(s) 513; Sec. 9.3) |
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| Plain-carbon steel | an iron-carbon alloy with 0.02 to 2 percent C. All commercial plain-carbon steels contain about 0.3 to 0.9 percent manganese along with sulfur, phosphorus, and silicon impurities. (See page(s) 513; Sec. 9.3) |
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| Hardenability | the ease of forming martensite in a steel upon quenching from the austenitic condition. A highly hardenable steel is one that will form martensite throughout in thick sections. Hardenability should not be confused with hardness. Hardness is the resistance of a material to penetration. The hardenability of a steel is mainly a function of its composition and grain size. (See page(s) 513; Sec. 9.4) |
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| Jominy hardenability test | a test in which a 1 in. (2.54 cm) diameter bar 4 in. (10.2 cm) long is austenitized and then water-quenched at one end. Hardness is measured along the side of the bar up to about 2.5 in. (6.35 cm) from the quenched end. A plot called the Jominy hardenability curve is made by plotting the hardness of the bar against the distance from the quenched end. (See page(s) 513; Sec. 9.4) |
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| White cast irons | iron-carbon-silicon alloys with 1.8 to 3.6 percent C and 0.5 to 1.9 percent Si. White cast irons contain large amounts of iron carbide that make them hard and brittle. (See page(s) 513; Sec. 9.8) |
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| Gray cast irons | iron-carbon-silicon alloys with 2.5 to 4.0 percent C and 1.0 to 3.0 percent Si. Gray cast irons contain large amounts of carbon in the form of graphite flakes. They are easy to machine and have good wear resistance. (See page(s) 513; Sec. 9.8) |
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| Ductile cast irons | iron-carbon-silicon alloys with 3.0 to 4.0 percent C and 1.8 to 2.8 percent Si. Ductile cast irons contain large amounts of carbon in the form of graphite nodules (spheres) instead of flakes as in the case of gray cast iron. The addition of magnesium (about 0.05 percent) before the liquid cast iron is poured enables the nodules to form. Ductile irons are in general more ductile than gray cast irons. (See page(s) 513-514; Sec. 9.8) |
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| Malleable cast irons | iron-carbon-silicon alloys with 2.0 to 2.6 percent C and 1.1 to 1.6 percent Si. Malleable cast irons are first cast as white cast irons and then are heattreated at about 940oC (1720oF) and held about 3 to 20 h. The iron carbide in the white iron is decomposed into irregularly shaped nodules or graphite. (See page(s) 514; Sec. 9.8) |