Glossary

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Aging	A change of the properties of certain metals and alloys that occurs at ambient or moderately elevated temperatures after hot working or a heat treatment (quench aging in ferrous alloys, natural or artificial aging) or cold working operation.
Aluminizing	High temperature (approx 900°C) pack or gaseous diffusion of aluminum into the surface of a component to enhance high temperature corrosion and oxidation resistance.
Annealing	A heat treatment process that softens the metal and produces desired changes in its microstructure. Vacuum annealing is referred to as bright annealing. The purposes of annealing include improving formability, machinability, dimensional stability, and various physical properties.
Annealing Temperature	Suitable Temperature at which a steel will be hold for annealing process
Artificial Aging	Aging above room temperature. See aging.
Atmosphere	The gaseous environment in which the metal being treated is heated for processing. Atmospheres are used to protect from chemical change or to alter the surface chemistry of steel through the addition or removal of carbon, nitrogen, hydrogen, and oxygen and to add certain metallic elements as chromium, silicon, sulfur, etc.
Austenitizing Temperature	The temperature at which the steel is hold for transforming into full austenite structure.
Austenitizing Time	Time from the begin until the end of soaking at austenitizing temperature.
Black Oxide	A dark black finish on a metal produced by immersing it in hot oxidizing salt or salt solution.
Blueing	Subjecting the scale-free surface of a steel to the action of air, steam, or other agents at a suitable temperature, thus forming a thin blue film of oxide and improving the appearance and resistance to corrosion.
Boronizing	The diffusion of boron into the surface of a component (usually steel) by a high temperature (approx. 900°C) gas or pack process. Produces hard phases within the surface (Typically 100µm deep).
Bright Annealing	Annealing in a protective medium to prevent discoloration of the bright surface.
Carbon Restoration	Replacing the carbon loss in the surface layer from previous processing by carburizing this layer to substantially the original carbon level. Some times called recarburizing.
Carbonitriding	A case hardening process in which a suitable ferrous material is heated (about 900°C by pack, gas, salt bath or plasma process) above the lower transformation temperature in a gaseous atmosphere of such composition as to cause simultaneous absorption of carbon and nitrogen by the surface and, by diffusion, create a concentration gradient. The process is completed by cooling at a rate that produces the desired properties in the workplace.
Carburizing	Absorption and diffusion of carbon into solid metal by heating (about 850 °C by pack, gas, salt bath or plasma process), to a temperature usually above Ac3, in contact with a suitable solids,liquids or gases material.
Carburizing Depth	The carburized depth of steel, often defined as the depth to which a certa in carbon content is reached .
Carburizing, Excessive	Adding higher carbon value to the surface of steel as it is.
Case depth	The surface layer depth of steel whose composition has been changed by heat treatment and the addition of carbon, nitrogen, chromium, or other material at high temperature.
Case Hardening	A generic term covering several processes applicable to steel that change the chemical composition of the surface layer by absorption of carbon, nitrogen, or a mixture of the two and, by diffusion, create a concentration gradient. The processes commonly used are carburizing and quench hardening, cyaniding, nitriding and carbonitriding, low pressure carburizing. The use of the applicable specific process name is preferred.
Chromizing	High temperature pack or gaseous diffusion of chromium into the surface of a component to enhance high temperature corrosion and oxidation resistance.
Compound Layer	A non-etching layer of iron nitrides formed at the surface of ferrous materials during nitriding or nitrocarburizing. Normally removed by grinding prior to component installation.
Cooling	Reduction of temperature of a piece of steel.
Cooling Agent	Medium for cooling and quenching.
Cooling Curve	A curve showing the relation between time and temperature during cooling of a material.
Cooling Rate	Change of temperature depending of time during cooling.
Cooling Temperature	Start temperature of a cooling process.
Cooling Time	Time span for two given temperatures during cooling process.
Decarburization	Removing carbon from the surface of a steel usually at high temperature, when in contact with certain types of atmosphere.
Decarburization Depth	Vertical distance from the surface of a decarburized piece of steel down to a point where the carbon content has its original value.
Decarburizing	The process of removing carbon from the surface of an iron -base alloy,mostly at higher temperature, when in contact with certain atmosphere in during the heat treatment process.
Diffusion Annealing	In ferrous alloys, annealing usually is done above the upper critical temperature, but the time-temperature cycles vary widely in both maximum temperature attained and in cooling rate employed, depending on composition, material condition, and results desired. Diffusion annealing will refine the crystalline.
Diffusion Layer	Layer which is formed during a thermochemical heat treatment in which the diffused elements ( e.g. nitrogen, carbon,) kept in solid solution or precipitated form. The amount of elements decreases continuously until they have reached the core values.
Dimensional Change	Change of dimensions of a piece of steel due to heat treatment procedure without distortion.
Direct Hardening	Heat treatment of steel with a subsequent direct quenching operation.
Direct Quenching	Quenching carburized parts directly from the carburizing operation.
Distortion	Change in size and dimension of steel as a result of the heat treatment.
Double Hardening	A double treatment in which a quench-hardened steel is quenched from two different austenitizing temperatures.
Dwell Time	Time from loading to unloading steel in a heat treatment furnace.
End-Quench Hardenability Test	A laboratory procedure for determining the hardenability of a steel or other ferrous alloy; widely referred to as the Jominy test. Hardenability is determined by heating a standard specimen in a fixture so that a stream of cold water impinges on one end, and, after cooling to room temperature is completed, measuring the hardness near the surface of the specimen at regularly spaced intervals along its length. The data is normally plotted as hardness versus distance from the quenched end.
Flame Hardening	A process of heating the surface layer of an iron-base alloy above the transformation temperature range by means of a high-temperature flame, followed by quenching.
Full Annealing	An imprecise term that denotes an annealing cycle to produce minimum strength and hardness. For the term to be meaningful, the composition and starting condition of the material and the time-temperature cycle used must be stated.
Graphitizing	Annealing in such a way that some or all of the carbon is precipitated as graphite.
Hardenability	In a ferrous alloy, the property that determines the depth and distribution of hardness induced by quenching.
Hardening	Any process of increasing hardness of metal by suitable treatment, usually involving heating and cooling.
Hardening and Tempering	A hardening cycle of steel is followed by a tempering cycle usually at temperatures above 550°C to develop higher toughness values at a certain tensile strength.
Hardening Depth	The hardened depth on carburized or nitrided parts, often defined as the depth to which the hardness exceeds 500 HV.
Hardness Increase	Highest achievable hardness of a piece of steel due to a certain heat treatment procedure.
Hardness Penetration	Thermal hardening treatment to achieve a hardness profile of a specific section of a piece of steel. A measure for the hardened layer is called hardness penetration depth.
Hardness Penetration Depth	Vertical distance from the surface of a hardened piece of steel down to a point where the hardness has a predetermined hardness value.
Hardness Profile	Hardness as a function of distance from a fixed reference point (usually from the surface).
Heat Temperature	Temperature of steel at the end of the heat cycle.
Heat Up	Increase of temperature in a piece of material.
Heating	Heating up steel until a given set point temperature over the complete cross- section has been reached.
Heating Duration	Time from begin to the end of heating.
Heating Temperature Curve	Temperature time depending curve of heated steel.
Heating Time	Time from the begin until the end of heating. The heating time is the sum of heating up and soaking.
Heating Up	Heating up a piece of steel until a given set point temperature has been reached.
Holding, Excessive	The portion of the thermal cycle in which the temperature of the object is maintained too long and subsequently creates a grain-size coarsening effect.
Induction Hardening	A surface-hardening process in which only the surface layer of a suitable ferrous work piece is heated above 900°C by electromagnetic induction to above the upper critical temperature and immediately quenched.
Internal oxidation	The formation of isolated particles of corrosion products beneath the surface of the metal or coating. This occurs as a result of preferential oxidation of certain alloy constituents by inward diffusion of oxygen, nitrogen, sulfur, etc.
Interrupted Quenching	A quenching procedure in which the work piece is removed from the first quench at a temperature substantially higher than that of the quenchant and is then subjected to a second quenching system having a different cooling rate than the first.
Ion nitriding	A method of surface hardening in which nitrogen ions are diffused into a work piece in a vacuum through the use of high-voltage electrical energy. Synonymous with plasma nitriding or glow-discharge nitriding.
Isothermal Transformation	A change in phase that takes place at a constant temperature. The time required for transformation to be completed, and in some instances the time delay before transformation begins, depends on the amount of supercooling below (or superheating above) the equilibrium temperature for the same transformation.
Maraging	A precipitation-hardening treatment applied to a special group of iron-base alloys to precipitate one or more intermetallic compounds in a matrix of essentially carbon-free martensite.
Martempering	A hardening procedure in which an austenitized ferrous work piece is quenched into an appropriate medium whose temperature is maintained substantially at the Ms of the work piece, held in the medium until its temperature is uniform throughout - but not long enough to permit bainite to form - and then cooled in air. The treatment is frequently followed by tempering. When the process is applied to carburized material, the controlling Ms temperature is that of the case. This variation of the process is frequently called marquenching.
Nitriding	A process of case hardening in which an iron-base alloy of special composition is heated in an atmosphere of ammonia or in contact with nitrogenous material.. A plasma process with a glow discharge in a nitrogen atmosphere is also applicable. Surface hardening is produced by the absorption of nitrogen without quenching.
Nitriding Depth	Case on nitrided parts, often defined as the depth to which the nitrogen value or the hardness exceeds a predetermined value.
Nitrocarburizing	Any of several processes in which both nitrogen and carbon are absorbed into the surface layers of a ferrous material at temperatures below the lower critical temperature and, by diffusion, create a concentration gradient. Nitrocarburizing is done mainly to provide an antiscuffing surface layer and to improve fatigue resistance.
Normalizing	Heating a ferrous alloy to a suitable temperature above the transformation range and then cooling in air to a temperature substantially below the transformation range.
Overheated	A metal is said to have been overheated if, after exposure to an unduly high temperature, it develops an undesirably coarse grain structure but is not permanently damaged. The structure damaged by overheating can be corrected by suitable heat treatment or by mechanical work or by a combination of the two. In this respect it differs from a burnt structure.
Plasma Nitriding	A method of surface hardening in which nitrogen ions are diffused into a work piece in a vacuum through the use of high-voltage electrical energy. Synonymous with plasma nitriding or glow-discharge nitriding.
Potential Hardness Increase	Employment of maximum hardness increase in the surface of a piece of metal by the use of optimal heat treating conditions.
Precipitation Hardening	Hardening caused by the precipitation of a constituent from a supersaturated solid solution.
Precipitation Heat Treatment	Artificial aging in which a constituent precipitates from a supersaturated solid solution.
Preheating	Heating before some further thermal or mechanical treatment. For tool steel, heating to an intermediate temperature, immediately before final austenitizing. For some nonferrous alloys, heating to a high temperature for a long time, to homogenize the structure before working. In welding and related processes, heating to an intermediate temperature for a short time immediately before welding, brazing, soldering, cutting, or thermal spraying.
Quench temperature	Start temperature of quenching of a piece of steel.
Quenching Time	Time from the begin until the end of a cooling process.
Recrystallization Annealing	Annealing cold-worked metal to produce a new grain structure without phase change.
Salt bath carburizing	Carburizing in salt.
Scaling (Scale)	Surface oxidation, partially adherent layers of corrosion products, left on metals by heating or casting in air or in other oxidizing atmospheres.
Secondary Hardness	The higher hardness developed by certain alloy steels when they are cooled from a tempering operation. This should always be followed by a second tempering operation. higher hardness is a result from precipitation of specific carbides and the transformation of retained austenite into martensite.
Siliconizing	Diffusing silicon into solid metal, usually steel, at elevated temperature during a heat treatment process.
Single Hardening	Single hardening treatment following after carburizing and cooling procedur below a temperature of AC1.
Soaking	Prolonged holding at a selected temperature to effect homogenization of structure or composition.
Soaking Time	Time from the begin until the end of warming up a piece of material.
Solution heat treatment	Heating an alloy to a suitable temperature, holding at that temperature long enough to cause one or more constituents to enter into solid solution, and then cooling rapidly enough to hold these constituents in solution.
Stabilizing treatment	Heating a solution-treated stabilized grade of austenitic stainless steel at 850°C to 900°C to precipitate all carbon so that sensitization is avoided on subsequent cooling to room temperature.
Stress, Relieving	Heating to suitable temperature, holding long enough to reduce residual stresses followed by sufficiently slow cooling to minimize development of new residual stresses.
Supercooling	Cooling below the temperature at which an equilibrium phase transformation takes place, without actually obtaining the transformation.
Superheating	Heating above the temperature at which an equilibrium phase transformation should occur without actually obtaining the transformation.
Surface Hardening	Conferring a superficial hardness to steel while maintaining a relatively soft core. The process commonly used are carbonitriding, carburizing, induction hardening, flame hardening, nitriding, nitrocarburizing and low pressure carburizing.
Temper	In heat treatment, reheating hardened steel or hardened cast iron to some temperature below the eutectoid temperature for the purpose of decreasing hardness and increasing toughness. The process also is sometimes applied to normalized steel. In tool steels, temper is sometimes used, but inadvisably, to denote carbon content. In nonferrous alloys and in some ferrous alloys (steels that cannot be hardened by heat treatment), the hardness and strength produced by mechanical or thermal treatment, or both, and characterized by a certain structure, mechanical properties, or reduction in area during cold working.
Temper Embrittlement	Embrittlement of alloy steels caused by holding within or cooling slowly through a temperature range just below the transformation range.
Tempering	Reheating quenched steel to a temperature below the critical range (<AC1), followed by any desired rate of cooling. Tempering is done (Once or multiple) to relieve quenching stresses, or to develop desired strength characteristics.
Tempering Temperature	Temperature on which a piece of steel will be hold for temper treatment.
Thermochemical Working	A general term covering a variety of processes (like aluminizing, carburizing, boronizing, carbonitriding, decarburizing, nitriding, plasma -nitriding,plasma-carburizing, siliconizing ect), combining controlled thermal and diffusion treatments to obtain specific properties.
Thermomechanical working	A general term covering a variety of processes combining controlled thermal and deformation treatments to obtain specific properties treatment.
Through Hardening	A treatment in which a piece of steel should be hardened over the complete cross section through the addition or removal of carbon, nitrogen, hydrogen, and oxygen and to add certain metallic elements as chromium, silicon, sulfur, etc.