o tempered martensite embrittlement o Embrittlement of high-strength alloy steels caused by tempering in the temperature range of 205 to 370 °C 400 to 700 °F; also called 350 °C or 500
Trang 2o sweep
o A type of foundry pattern that is a template cut to the profile of the desired mold shape that, when revolved around a stake or spindle, produces that shape in the mold
o Swift cup test
o A simulative test for determining formability of sheet metal in which circular blanks of various diameters are clamped in a die ring and deep drawn into a cup by a flat-bottomed cylindrical punch The ratio of the largest blank diameter that can be drawn successfully to the cup diameter
is known as the limiting drawing ratio (LDR) or deformation limit
o swing forging machine
o Equipment for continuously hot reducing ingots, blooms, or billets to square flats, rounds, or rectangles by the crank-driven oscillating action of paired dies
o swing frame grinder
o A grinding machine suspended by a chain at the center point so that it may be turned and swung
in any direction for grinding of billets, large castings, or other heavy work Principal use is removing surface imperfections and roughness
o synthetic cold-rolled sheet
o A hot-rolled pickled sheet given a sufficient final temper pass to impart a surface approximating that of cold-rolled steel
o A rolling mill consisting of two or more stands arranged so that the metal being processed travels
in a straight line from stand to stand In continuous rolling, the various stands are synchronized
so that the strip can be rolled in all stands simultaneously Contrast with single-stand mill See also rolling mills
Trang 3o temper
o (1) 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 (2) In tool steels, temper is sometimes used, but inadvisedly, to denote the carbon content (3) 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 (4) To moisten green sand for casting molds with water
of time Also known as annealing carbon
o temper color
o A thin, tightly adhering oxide skin (only a few molecules thick) 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
o tempered layer
o A surface or subsurface layer in a steel specimen that has been tempered by heating during some stage of the metallographic preparation sequence (usually grinding) When observed in a section after etching, the layer appears darker than the base material
o tempered martensite
o The decomposition products that result from heating martensite below the ferrite-austenite transformation temperature
o tempered martensite embrittlement
o Embrittlement of high-strength alloy steels caused by tempering in the temperature range of 205
to 370 °C (400 to 700 °F); also called 350 °C or 500 °F embrittlement Tempered martensite embrittlement is 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 It differs from temper embrittlement in the strength of the material and the temperature exposure range In temper embrittlement, the steel is usually tempered at a relatively high temperature, producing lower strength and hardness, and embrittlement occurs upon slow cooling after tempering and during service at temperatures within the embrittlement range In tempered martensite embrittlement, the steel is tempered within the embrittlement range, and service exposure is usually at room temperature
o temper embrittlement
o Embrittlement of low-alloy steels caused by holding within or cooling slowly through a temperature range (generally 300 to 600 °C, or 570 to 1110 °F) 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 temperature Temper embrittlement can be reversed by retempering above the critical temperature range, then cooling rapidly Compare with tempered martensite embrittlement
o tempering
o In heat treatment, reheating hardened steel to some temperature below the eutectoid temperature
to decrease hardness and/or increase toughness
Trang 4o A stress that causes two parts of an elastic body, on either side of a typical stress plane, to pull apart Contrast with compressive stress
o terminal phase
o A solid solution having a restricted range of compositions, one end of the range being a pure component of an alloy system
o terminal solid solution
o In a multicomponent system, any solid phase of limited composition range that includes the composition of one of the components of the system See also solid solution
or painted
o tertiary creep
o See creep
o texture
o In a polycrystalline aggregate, the state of distribution of crystal orientations In the usual sense, it
is synonymous with preferred orientation , in which the distribution is not random Not to be confused with surface texture See also fiber
o thermal cutting
o A group of cutting processes that melts the metal (material) to be cut See also air carbon arc cutting , arc cutting , carbon arc cutting , electron beam cutting , laser beam cutting , metal powder cutting , oxyfuel gas cutting , oxygen arc cutting , oxygen cutting , and plasma arc cutting
o thermal decomposition
o (1) The decomposition of a compound into its elemental species at elevated temperatures (2) A process whereby fine solid particles can be produced from a gaseous compound See also carbonyl powder
o thermal electromotive force
o The electromotive force generated in a circuit containing two dissimilar metals when one junction
is at a temperature different from that of the other See also thermocouple
Trang 5has been attributed to precipitation of titanium carbides and titanium carbonitrides at austenite grain boundaries during cooling through the critical temperature range
o thermally induced embrittlement
o thermit reactions
o Strongly exothermic self-propagating reactions such as that where finely divided aluminum reacts with a metal oxide A mixture of aluminum and iron oxide produces sufficient heat to weld steel, the filler metal being produced in the reaction See also thermit welding
o thermit welding
o A welding process that produces coalescence of metals by heating them with superheated liquid metal from a chemical reaction between a metal oxide and aluminum, with or without the application of pressure Filler metal is obtained from the liquid metal
o thermomechanical working
o A general term covering a variety of metalforming processes combining controlled thermal and deformation treatments to obtain synergistic effects, such as improvement in strength without loss of toughness Same as thermal-mechanical treatment
o thief
o A racking device or nonfunctional pattern area used in the electroplating process to provide a more uniform current density on plated parts Thieves absorb the unevenly distributed current on
Trang 6irregularly shaped parts, thereby ensuring that the parts will receive an electroplated coating of uniform thickness See also robber
o tilt mold ingot
o An ingot made in a tilt mold
o tint etching
o Immersing metallographic specimens in specially formulated chemical etchants in order to produce a stable film on the specimen surface When viewed under an optical microscope, these surface films produce colors that correspond to the various phases in the alloy Also known as color etching
o tin tossing
o Oxidizing impurities in molten tin by pouring it from one vessel to another in air, forming a dross that is mechanically separable
Trang 7o tooth
o (1) A projection on a multipoint tool (such as on a saw, milling cutter, or file) designed to produce cutting (2) A projection on the periphery of a wheel or segment thereof as on a gear, spline, or sprocket, for example designed to engage another mechanism and thereby transmit force or motion, or both A similar projection on a flat member such as a rack
o tooth point
o The chamfered cutting edge of a face milling blade, to which a flat is sometimes added to produce
a shaving effect and to improve finish
o The total amount of permanent extension of a test piece broken in a tensile test usually expressed
as a percentage over a fixed gage length See also elongation, percent
o toughness
o Ability of a material to absorb energy and deform plastically before fracturing Toughness is proportional to the area under the stress-strain curve from the origin to the breaking point In metals, toughness is usually measured by the energy absorbed in a notch impact test See also impact test
o tough pitch copper
o Copper containing from 0.02 to 0.04% O, obtained by refining copper in a reverberatory furnace
o tracer milling
Trang 8o Duplication of a three-dimensional form by means of a cutter controlled by a tracer that is directed by a master form
o tramp alloys
o Residual alloying elements that are introduced into steel when unidentified alloy steel is present
in the scrap charge to a steelmaking furnace
o tramp element
o Contaminant in the components of a furnace charge, or in the molten metal or castings, whose presence is thought to be either unimportant or undesirable to the quality of the casting Also called trace element
o transformation ranges
o Those ranges of temperature within which austenite 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 also transformation temperature
o transformation temperature
o The temperature at which a change in phase occurs This term is sometimes used to denote the limiting temperature of a transformation range The following symbols are used for irons and steels:
Ac cm In hypereutectoid steel
Ac 1 The temperature at which austenite begins to form during heating
Ac 3 The temperature at which transformation of ferrite to austenite is completed during heating
Ac 4 The temperature at which austenite transforms to ferrite during heating
Ae cm , Ae 1 , Ae 3 ,
Ae 4
The temperatures of phase changes at equilibrium
Ar cm In hypereutectoid steel
Ar 1 The temperature at which transformation of austenite to ferrite or to ferrite plus cementite is
completed during cooling
Ar 3 The temperature at which austenite begins to transform to ferrite during cooling
Ar 4 The temperature at which ferrite transforms to austenite during cooling
Ar' The temperature at which transformation of austenite to pearlite starts during cooling
M f The temperature at which transformation of austenite to martensite is completed during
cooling
M s (or Ar'') The temperature at which transformation of austenite to martensite starts during cooling
Trang 9o NOTE: All these changes, except formation of martensite, occur at lower temperatures during cooling than during heating, and depend on the rate of change of temperature
o Fracture through or across the crystals or grains of a material Also called transcrystalline fracture
or intracrystalline fracture Contrast with intergranular fracture
o transition lattice
o An unstable crystallographic configuration that forms as an intermediate step in a solid-state reaction such as precipitation from solid solution or eutectoid decomposition
o transition metal
o A metal in which the available electron energy levels are occupied in such a way that the d-band
contains less than its maximum number of ten electrons per atom, for example, iron, cobalt, nickel, and tungsten The distinctive properties of the transition metals result from the
incompletely filled d-levels
o transverse direction
o Literally, "across," usually signifying a direction or plane perpendicular to the direction of working In rolled plate or sheet, the direction across the width is often called long transverse; the direction through the thickness, short transverse
o transverse rolling machine
o Equipment for producing complex preforms or finished forgings from round billets inserted transversely between two or three rolls that rotate in the same direction and drive the billet The rolls, carrying replaceable die segments with appropriate impressions, make several revolutions for each rotation of the workpiece
o transverse rupture strength (TRS)
o The stress, calculated from the bending stress formula, required to break a powder metallurgy specimen of a given dimension The specimen is supported near its ends with a load applied midway between the fixed centerline of the supports From the value of the break load, the TRS can be calculated using:
o where F is the load at fracture, L is the span between supports, and W and H are the width and
height of the test bar, respectively
o trees
o Visible projections of electrodeposited metal formed at sites of high current density
o trepanning
Trang 10o A machining process for producing a circular hole or groove in solid stock, or for producing a disk, cylinder, or tube from solid stock, by the action of a tool containing one or more cutters (usually single-point) revolving around a center
o trimmers
o The combination of trimmer punch, trimmer blades, and perhaps trimming shoe used to remove the flash from the forging
o trimming
o (1) In forging, removing any parting-line flash or excess material from the part with a trimmer in
a trim press; can be done hot or cold (2) In drawing, shearing the irregular edge of the drawn part (3) In casting, the removal of gates, risers, and fins
o A previously unresolvable, rapidly etching, fine aggregate of carbide and ferrite produced either
by tempering martensite at 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
o Troy ounce
o A unit of weight for precious metals that is equal to 31.1034768 g (1.0971699 oz avoirdupois)
o true current density
o See preferred term local current density
o true strain
o (1) The ratio of the change in dimension, resulting from a given load increment, to the magnitude
of the dimension immediately prior to applying the load increment (2) In a body subjected to axial force, the natural logarithm of the ratio of the gage length at the moment of observation to the original gage length Also known as natural strain
o true stress