A chemical element that is added to steel to modify sulfide type inclusion size, morphology and distribution. The resulting sulfide type inclusions are finer and remain ellipsoidal in shape following hot working, thereby improving transverse properties.
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, the hardness and strength produced by mechanical and/or thermal treatment and characterized by certain structure, mechanical properties or reduction of area during cold working.
The same as annealing carbon.
A thin, tightly adhering oxide skin that forms when steel is tempered at a low temperature or for a short time in air or a mildly oxidizing atmosphere. The color, which ranges from straw to blue depending on the thickness of the oxide skin, varies with both tempering time and temperature.
Embrittlement of alloy steels caused by holding within or cooling slowly through a temperature range just below the transformation range. Embrittlement is the result of the segregation at grain boundaries of impurities such as arsenic, antimony, phosphorus, and tin; it is usually manifested as an upward shift in ductile-to-brittle transition by retempering above the critical temperature range, then cooling rapidly.
Degree of warmth or coldness in relation to temperatures upon which temperature scales are based. Accepted scales include Centigrade, Fahrenheit and Kelvin, among others.
Fahrenheit: 32 degrees on the Fahrenheit scale (denoted 32°F) is the temperature at which water freezes, and 180° hotter is the temperature at which water boils.
Celcius: 0 degrees on the Celcius scale (denoted 0°C) is the temperature at which water freezes, and 100° hotter is the temperature at which water boils.
kelvin: 0 on the Kelvin scale (denoted 0 K or 0 kelvin) is the temperature at which all atomic motion ceases, and is equal to -273°C. It uses the same unit increment as the Celcius scale, making the temperature at which water freezes equal to 273 K.
Tempered Martensite Embrittlement
Embrittlement of ultra-high-strength steels caused by tempering in the temperature range 205°C–400°C (400°F–750°F); also called 350°C or 500°F embrittlement. Thought to result from the combined effects of cementite precipitation on prior-austenite grain boundaries or interlath boundaries and the segregation of impurities at prior-austenite grain boundaries.
A treatment consisting of heating uniformly to some predetermined temperature under the critical range, holding at that temperature a designated period of time and then cooling in air or liquid. This treatment is used to produce one or more of the following end results: A) to soften material for subsequent machining or cold working, B) to improve ductility and relieve stresses resulting from prior treatment or cold working, and C) to produce the desired mechanical properties or structure in the second step of a double treatment.
The maximum stress in uniaxial tension testing which a material will withstand prior to fracture. The ultimate tensile strength is calculated from the maximum load applied during the test divided by the original cross-sectional area. Compare with Yield Strength.
Axial forces per unit area applied to a body, tending to extend it.
A method for determining transformations in a metal by noting the temperatures at which thermal arrests occur. These arrests are manifested by changes in the slope of the plotted mechanically-traced heating and cooling curves. When such data are secured under nearly equilibrium conditions of heating and cooling, the method is commonly used for determining certain critical temperatures required for the construction of equilibrium diagrams.
Thermal Barrier Coating
The property of matter by which heat energy is transmitted through particles in contact. For engineering purposes, the amount of heat conducted through refractories is usually given in Btu per hour for one square foot of area, for a temperature difference of one degree Fahrenheit, and for a thickness of one inch (Btu/hr×ft×F/in).
Thermal Diffusion (TD)
Thermal Electromotive Force
(1) Fracture resulting from the presence of temperature gradients that vary with time in such a manner as to produce cyclic stresses in a structure.
(2) Failure resulting from rapid cycles of alternate heating and cooling.
Stress developed by rapid and uneven heating of a material.
A process in which coating material is heated and accelerated from a spray torch towards the work piece. The deposited material forms a coating on the surface.
A heat treatment carried out in a medium suitably chosen to produce a change in the chemical composition of the object by exchange with the medium.
Thermochemically Formed Coatings
Thermo-Reactive Diffusion (TRD)
A salt bath treatment at about 900°C for high-carbon tool steels. Produces a very hard layer of vanadium carbide, typically .0002-.0003” thick. The shortened name of this process is “thermal diffusion” (TD).
A device for measuring temperatures, consisting of lengths of two dissimilar metals or alloys that are electrically joined at one end and connected to a voltage-measuring instrument at the other end. When one junction is hotter than the other, a thermal electromotive force is produced that is roughly proportional to the difference in temperature between the hot and cold junctions.
A general term covering a variety of processes combining controlled thermal and deformation treatments to obtain specific properties. Same as thermo-mechanical treatment.
A term used to describe a quench in which the cooling rate of the part being quenched must be changed abruptly at some time during the cooling cycle.
Time-Temperature-Transformation (TTT) Diagram
A metallic element that is added to boron steels because it combines with oxygen and nitrogen, which increases the effectiveness of boron. Titanium, as titanium nitride, also provides grain size control at elevated temperatures in microalloy steels. In excess, titanium is detrimental to machinability and internal cleanness.
Titanium Nitride (TiN)
The permissible deviation of a dimension from the nominal or desired value. The minimum clearance between mating parts.
Total Indicator Reading
See preferred term: total indicator variation.
Total Indicator Variation
The difference between the maximum and minimum indicator readings during a checking cycle.
In a plasma torch, the plasma jet is emitted from the torch, and the current flows from the internal cathode to the internal anode represented by the nozzle of the torch. When the jet is carried to another anode with it being electrically favorable to do so, the current will then transfer to the second anode—usually the work piece—and the arc is said to be transferred.
Those ranges of temperature within which a phase forms during heating and transforms during cooling. The two ranges are distinct; sometimes overlapping but never coinciding. The limiting temperatures of the ranges depend on the composition of the alloy and on the rate of change of temperature, particularly during cooling. See transformation temperature.
The temperature at which a change in phase occurs. The term is sometimes used to denote the limiting temperature of a transformation range. The following symbols are used for iron and steels:
Accm – In hypereutectoid steel, the temperature at which the solution of cementite in austenite is completed during heating.
Ac1 – The temperature at which austenite begins to form during heating.
Ac3 – The temperature at which transformation of ferrite to austenite is completed during heating.
Ac4 – The temperature at which austenite transforms to delta ferrite during heating.
Aecm, Ae1, Ae3, Ae4 – The temperature of phase changes at equilibrium.
Arcm – In hypereutectoid steel, the temperature at which precipitation of cementite starts during cooling.
Ar1 – The temperature at which transformation of austenite to ferrite or to ferrite plus cementite is completed during cooling.
Ar3 – The temperature at which austenite begins to transform to ferrite during cooling.
Ar4 – The temperature at which delta ferrite transforms to austenite during cooling.
Ar’ – The temperature at which transformation of austenite to pearlite starts during cooling.
f – The temperature at which transformation of austenite to martensite finishes during cooling.
s (or Ar”) – The temperature at which transformation of austenite to martensite starts during cooling.
Note: All these changes except the formation of martensite occur at lower temperatures during cooling than during heating, and depend on the rate of change of temperature.
A phenomenon, that occurs chiefly in certain highly alloyed steels that have been heat treated to produce metastable austenite and/or martensite, in which on subsequent deformation part of the austenite undergoes strain-induced transformation to martensite. Steels capable of transforming in this manner—commonly referred to as TRIP steels—are highly plastic after heat treatment, but exhibit a very high rate of strain hardening, and thus have high tensile and yield strengths after plastic deformation at temperatures ~20°C–500°C (70°F–930°F). Cooling to -195°C (-320°F) may or may not be required to complete the transformation to martensite. Tempering usually is done following the transformation.
Through or across crystals or grains. Also called intracrystalline or transcrystalline.
(1) An arbitrarily defined temperature that lies within the temperature range in which metal fracture characteristics (as usually determined by tests of notched specimens) change rapidly (e.g. from primarily fibrous [shear] to primarily crystalline [cleavage] fracture). Commonly used definitions are “transition temperature for 50% cleavage fracture”, “10 ft × lbf transition temperature”, and “transition temperature for half maximum energy.”
(2) Sometimes used to denote an arbitrarily defined temperature within a range in which the ductility changes rapidly with temperature.
Transmission Electron Microscopy (TEM)
Applied to thin and thick film analysis, it permits observation of smaller features such as microcolumnar voids and patterns of dislocations in the bulk.
Transparent Electrical Conductors
Include transparent conductive oxide (TCO) films such as indium trioxide (In2O3), tin dioxide (SnO2), zinc oxide (ZnO) and an alloy of indium oxide and tin oxide (ITO). These have numerous applications such as heaters on windows for defrosting, antistatic coatings on display screens, electrodes on flat panel displays and electrochromic devices, and electrodes on both flexible (resistive screen) and rigid (capacitive screen) touch screens. Electrical resistivity for the TCO films can vary from more than 1,000 ohms per “square” to fewer than 10 ohms per square with good optical transmission.
This condition applies to a wall entity during a CFD analysis of a particulate two-phase flow. A particle touches the wall entity and its momentum and energy are assumed to be completely lost to the wall entity while the mass is assumed to be lost to the fluid.
TRIP (Transformation-Induced Plasticity) Steel
(obsolete term!) A previously unresolved, rapidly-etching fine aggregate of carbide and ferrite produced either by tempering martensite at a low temperature or by quenching a steel at a rate slower than the critical cooling rate. Preferred terminology for the first product is tempered martensite; for the latter, fine pearlite.
A solid lubricant, stable to 500°C, that is applied at ambient temperature for use at high vacuum, cryogenic or high temperatures. It is 0.5 microns thick. It extends bearing life and prevents galling, fretting and seizing. Can be applied to miniature ball races in assembled condition. It was developed by NASA for use in deep space. It is used in the plastics industry as a permanent release coating.
Technical terminology for the type of flow which occurs when the Reynolds Number exceeds 2000. In contrast to laminar flow, turbulent flow can be described as an irregular and random-looking motion.
A particular type of analysis where two of the three phases (gas, liquid and solid) are modeled together. The numerical equations are modified to produce an interaction between the two phases.