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annealing
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The steady heating of a metal at a certain temperature above the recrystallization phase followed by a gradual cooling process.
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austenite phase
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The phase at which solid steel recrystallizes and has a face-centered cubic crystal structure. Austenite steel holds a greater amount of dissolved carbon and exhibits increased formability.
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bainite
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A combination of ferrite and cementite in ferrous metals that is harder than pearlite. Bainite contains needlelike grain structures, and it requires an initial rapid cooling followed by gradual cooling.
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batch furnace
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A heat-treatment furnace that soaks a stationary workpiece.
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body-centered cubic
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The crystal structure that contains an atom in the center and one atom in each corner of a cube. Ferrite has a BCC crystal structure.
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body-centered tetragonal
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A body-centered cubic crystal structure that has been distorted by the presence of extra atoms of carbon. Martensite has a BCT crystal structure.
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carburizing
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A surface hardening method that heats metal within a carbon-rich environment to increase carbon levels on the metal surface for added hardness.
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cementite
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A compound of iron and carbon that is very hard and brittle. The presence of cementite hardens steel.
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chromium
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A shiny, hard, steel-gray metal that increases the hardenability of steel. Stainless steels also contain large amounts of chromium.
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cold working
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The shaping of metal at temperatures substantially below the point of recrystallization. Cold working adds strength and hardness.
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continuous furnace
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A heat-treatment furnace that soaks a workpiece as it moves along a conveyor or rotating hearth.
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crystal structure
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The formation of a consistent, repeating pattern of atoms. A crystal structure develops as a liquid metal cools and changes into a solid.
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ductility
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The ability of a metal to be drawn, stretched, or formed without breaking.
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electric furnace
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A heat-treatment furnace that uses electric current to control the temperature of a metal.
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eutectoid temperature
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The lowest temperature at which austenite transforms into ferrite and cementite. Steel with 0.77 percent carbon transforms at this temperature.
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face-centered cubic
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The crystal structure that contains one atom in the center of the six sides of a cube and one atom in each corner of the cube. Austenite has an FCC crystal structure.
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ferrite phase
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The phase at which solid steel has a body-centered cubic crystal structure. Ferrite steel can hold only a minimal amount of carbon, and it is relatively soft.
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flame hardening
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A surface hardening method that heats a metal with a high-temperature flame, followed by quenching.
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full annealing
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An annealing process that soaks the metal above the austenite phase, followed by gradual cooling. A full anneal may take a day or longer.
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hardenability
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The ability of a metal to be hardened by normal heat treatment processes.
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heat treatment
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The controlled heating and cooling processes used to change the structure of a material and alter its physical and mechanical properties.
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hypereutectoid steel
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Steel that contains more than 0.77 percent carbon. Hypereutectoid steel consists of pearlite and cementite at room temperature.
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hypoeutectoid steel
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Steel that contains less than 0.77 percent carbon. Hypoeutectoid steel consists of ferrite and pearlite at room temperature.
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induction hardening
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A surface hardening method that heats a metal with an electrical current.
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manganese
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A hard, brittle, gray-white metal that increases the hardenability of steel. Manganese also increases strength and hardness.
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martensite
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A steel that consists of a distorted, body-centered tetragonal crystal structure. Martensite is very hard and brittle.
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mechanical properties
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A property that describes a material's ability to compress, stretch, bend, scratch, dent, or break.
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molybdenum
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A hard, silvery white metal that increases the hardenability of steel. Molybdenum is also an effective substitute for tungsten in many high-speed tool steels.
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nitriding
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A surface hardening method that heats a metal within a nitrogen-rich environment. Metals that are nitrided typically contain aluminum or chromium.
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normalizing
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The steady heating of a metal above the recrystallization phase, followed by a cooling process at a moderate pace. Normalized metals are often cooled in open air at room temperature.
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pearlite
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A combination of ferrite and cementite. Pearlite grain structures resemble human fingerprints. Steel with exactly 0.77 percent carbon consists of uniform pearlite at room temperature.
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phase
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A portion of material with a uniform crystal structure, consistent properties, and recognizable boundaries. At room temperature, steel consists of two or more phases.
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precipitation
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The separation of a substance that was previously dissolved in another substance.
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process annealing
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An annealing process that heats the metal below the austenite phase to restore ductility after cold working.
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quenching
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The soaking of a metal at a high temperature above the recystallization phase, followed by a rapid cooling process. The quenching of steel creates martensite.
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quenching medium
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The liquid or air substance used to cool a metal during quenching. Water, saltwater, air, and oil are common quenching mediums.
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recovery annealing
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An annealing process that attempts to partially restore the original grain structure of the metal and still preserve the strain hardening that has developed.
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scaling
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The development of an unwanted rough coating on the surface of the metal.
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soaking
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The heating of a metal at a constant temperature for a suitable duration of time.
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strain hardening
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The increase of hardness and strength in steel caused by the cold working of the metal.
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stress relieving
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An annealing process that heats the metal below the austenite phase to reduce distortions or changes in dimensions that might occur after shaping.
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surface hardening
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Any heat-treatment method used to alter the properties within the surface or localized area of a metal.
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tempered martensite
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Martensite steel that has been tempered to improve ductility and toughness.
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tempering
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The steady heating of martensite steel at a temperature below the recrystallization phase, followed by a gradual cooling process.
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toughness
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The amount of energy a material can absorb before it breaks.
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