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Making tack welds.
A weld made to hold parts of a weldment in proper alignment until the final welds are made.
The discarded portion of a crushed ore, separated during concentration.
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.
Arc welding in which two or more electrodes are in a plane parallel to the line of travel.
The forming of one or more identical bends having parallel axes by wiping sheet metal around one or more radius dies in a single operation. The sheet, which may have side flanges, is clamped against the radius die and then made to conform to the radius die by pressure from a rocker-plate die that moves along the periphery of the radius die. See also wiper forming (wiping).
A cylindrical or conical thread-cutting tool with one or more cutting elements having threads of a desired form on the periphery. By a combination of rotary and axial motions, the leading end cuts an internal thread, the tool deriving its principal support from the thread being produced.
The apparent density of a powder, obtained when the volume receptacle is tapped or vibrated during loading under specified conditions.
(1) Producing internal threads with a cylindrical cutting tool having two or more peripheral cutting elements shaped to cut threads of the desired size and form. By a combination of rotary and axial motion, the leading end of the tap cuts the thread while the tap is supported mainly by the thread it produces. See also tap. (2) Opening the outlet of a melting furnace to remove molten metal. (3) Removing molten metal from a furnace.
Surface discoloration of a metal caused by formation of a thin film of corrosion product.
A ladle in which, by means of an external spout, metal is removed from the bottom rather than the top of the ladle.
Pouring molten metal from a ladle into ingot molds. The term applies particularly to the specific operation of pouring either iron or steel into ingot molds.
(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.
See temper embrittlement.
Clusters of finely divided graphite, such as that found in malleable iron, that are formed as a result of decomposition of cementite, for example, by heating white cast iron above the ferrite-austenite transformation temperature and holding at these temperatures for a considerable period of time. Also known as annealing carbon.
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.
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.
The decomposition products that result from heating martensite below the ferrite-austenite transformation temperature.
tempered martensite embrittlement
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.
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.
In heat treatment, reheating hardened steel to some temperature below the eutectoid temperature to decrease hardness and/or increase toughness.
Light cold rolling of sheet steel to improve flatness, to minimize the formation of stretcher strains, and to obtain a specified hardness or temper.
In tensile testing, the ratio of maximum load to original cross-sectional area. Also called ultimate strength. Compare with yield strength.
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.
See tension testing.
The force or load that produces elongation.
A method of determining the behavior of materials subjected to uniaxial loading, which tends to stretch the material. A longitudinal specimen of known length and diameter is gripped at both ends and stretched at a slow, controlled rate until rupture occurs. Also known as tensile testing.
A solid solution having a restricted range of compositions, one end of the range being a pure component of an alloy system.
terminal solid solution
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.
An alloy that contains three principal elements.
The complete series of compositions produced by mixing three components in all proportions.
An alloy of lead containing 3 to 15% Sn, used as a hot dip coating for steel sheet or plate. The term long terne is used to describe terne-coated sheet, whereas short terne is used for terne-coated plate. Terne coatings, which are smooth and dull in appearance (terne means dull or tarnished in French), give the steel better corrosion resistance and enhance its ability to be formed, soldered, or painted.
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.
Exposure of a material or component to a given thermal condition or a programmed series of conditions for prescribed periods of time.
A method for determining transformations in a metal by noting the temperatures at which thermal arrests occur. These arrests are manifested by changes in slope of the plotted or 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 phase diagrams.
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.
(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.
thermal electromotive force
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.
Intergranular fracture of maraging steels with decreased toughness resulting from improper processing after hot working. Thermal embrittlement occurs upon heating above 1095 °C (2000 °F) and then slow cooling through the temperature range of 980 to 815 °C (1800 to 1500 °F), and has been attributed to precipitation of titanium carbides and titanium carbonitrides at austenite grain boundaries during cooling through the critical temperature range.
Fracture resulting from the presence of temperature gradients that vary with time in such a manner as to produce cyclic stresses in a structure.
A nondestructive test method in which heat-sensing devices are used to measure temperature variations in components, structures, systems, or physical processes. Thermal methods can be useful in the detection of subsurface flaws or voids, provided the depth of the flaw is not large compared to its diameter. Thermal inspection becomes less effective in the detection of subsurface flaws as the thickness of an object increases, because the possible depth of the defects increases.
thermally induced embrittlement
See thermomechanical working.
The development of a steep temperature gradient and accompanying high stresses within a material or structure.
A group of coating or welding processes in which finely divided metallic or nonmetallic materials are deposited in a molten or semimolten condition to form a coating. The surfacing material may be in the form of powder, rod, or wire. See also electric arc spraying , flame spraying , plasma spraying , and powder flame spraying.
Stresses in a material resulting from nonuniform temperature distribution.
Removal of material due to softening, melting, or evaporation during sliding or rolling. Thermal shock and high-temperature erosion may be included in the general description of thermal wear. Wear by diffusion of separate atoms from one body to the other, at high temperatures, is also sometimes denoted as thermal wear.
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.
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.
Removal of workpiece material–usually only burrs and fins–by exposure to hot fuel gases that are formed by igniting an explosive, combustible mixture of natural gas and oxygen. Also known as the thermal energy method.
Heat treatment for steels carried out in a medium suitably chosen to produce a change in the chemical composition of the object by exchange with the medium.
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 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.
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 irregularly shaped parts, thereby ensuring that the parts will receive an electroplated coating of uniform thickness. See also robber.
A term used to define a casting that has the minimum wall thickness to satisfy its service function.
Producing external threads on a cylindrical surface.
The production of threads by rolling the piece between two grooved die plates, one of which is in motion, or between rotating grooved circular rolls. Also known as roll threading.
A temper of nonferrous alloys and some ferrous alloys characterized by tensile strength and hardness about midway between those of half hard and full hard tempers.
The bending of a piece of metal or a structural member in which the object is placed across two supports and force is applied between and in opposition to them. See also V-bend die.
Threshold stress for stress-corrosion cracking. The critical gross section stress at the onset of stress-corrosion cracking under specified conditions.
(1) The relationship between the current density at a point on a surface and its distance from the counterelectrode. The greater the ratio of the surface resistivity shown by the electrode reaction to the volume resistivity of the electrolyte, the better is the throwing power of the process. (2) The ability of a plating solution to produce a uniform metal distribution on an irregularly shaped cathode. Compare with covering power.
Continuous bright lines on sheet or strip in the rolling direction.
Tungsten inert-gas welding; see preferred term gas tungsten arc welding.
A subgrain boundary consisting of an array of edge dislocations.
A casting mold, usually a book (permanent) mold, that rotates from a horizontal to a vertical position during pouring, which reduces agitation and thus the formation and entrapment of oxides.
tilt mold ingot
An ingot made in a tilt mold.
A quench in which the cooling rate of the part being quenched must be changed abruptly at some time during the cooling cycle.
A curve produced by plotting time against temperature.
time-temperature-transformation (TTT) diagram
See isothermal transformation (IT) diagram.
Coating metal with a very thin layer of molten solder or brazing filler metal.
A polymorphic modification of tin that causes it to crumble into a powder known as gray tin. It is generally accepted that the maximum rate of transformation occurs at about -40 °C (-40 °F), but transformation can occur at as high as about 13 °C (55 °F).
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.
Oxidizing impurities in molten tin by pouring it from one vessel to another in air, forming a dross that is mechanically separable.
A mechanical press in which the slide is actuated by one or more toggle links or mechanisms.
The specified permissible deviation from a specified nominal dimension, or the permissible variation in size or other quality characteristic of a part.
The extreme values (upper and lower) that define the range of permissible variation in size or other quality characteristic of a part.
The portion of a forging billet, usually on one end, that is gripped by the operator’s tongs. It is removed from the part at the end of the forging operation. Common to drop hammer and press-type forging.
A generic term applying to die assemblies and related items used for forming and forging metals.
Any of a class of carbon and alloy steels commonly used to make tools. Tool steels are characterized by high hardness and resistance to abrasion, often accompanied by high toughness and resistance to softening at elevated temperature. These attributes are generally attained with high carbon and alloy contents.
(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.
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.
A process for separating copper and nickel, in which their molten sulfides are separated into two liquid layers by the addition of sodium sulfide. The lower layer holds most of the nickel.
See preferred terms cutting torch (arc) , cutting torch (oxyfuel gas) , welding torch (arc) , and welding torch (oxyfuel gas).
A brazing process in which the heat required is furnished by a fuel gas flame.
A soldering process in which the heat required is furnished by a fuel gas flame.
(1) A twisting deformation of a solid or tubular body about an axis in which lines that were initially parallel to the axis become helices. (2) A twisting action resulting in shear stresses and strains.
In a body being twisted, the algebraic sum of the couples or the moments of the external forces about the axis of twist, or both.
The sum of the free carbon and combined carbon (including carbon in solution) in a ferrous alloy.
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.
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.
tough pitch copper
Copper containing from 0.02 to 0.04% O, obtained by refining copper in a reverberatory furnace.
Duplication of a three-dimensional form by means of a cutter controlled by a tracer that is directed by a master form.
Residual alloying elements that are introduced into steel when unidentified alloy steel is present in the scrap charge to a steelmaking furnace.
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.
Cracking or fracturing that occurs through or across a crystal. Also termed intracrystalline cracking.
Heat treatment of steels comprising austenitization followed by cooling under conditions such that the austenite transforms more or less completely into martensite and possibly into bainite.
A phenomenon, occurring chiefly in certain highly alloyed steels that have been heat treated to produce metastable austenite or metastable austenite plus martensite, whereby, 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 between about 20 and 500 °C (70 and 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 transformation.
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.
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:
Accm In hypereutectoid steel
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 ferrite during heating.
Aecm, Ae1, Ae3, Ae4 The temperatures of phase changes at equilibrium
Arcm In hypereutectoid steel
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 ferrite transforms to austenite during cooling.
Ar’ The temperature at which transformation of austenite to pearlite starts during cooling.
Mf The temperature at which transformation of austenite to martensite is completed during cooling.
Ms(or Ar”) The temperature at which transformation of austenite to martensite starts during cooling.
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.
Through or across crystals or grains. Also called intracrystalline or transcrystalline.
Cracking or fracturing that occurs through or across a crystal or grain. Also called transcrystalline cracking. Contrast with intergranular cracking.
Fracture through or across the crystals or grains of a material. Also called transcrystalline fracture or intracrystalline fracture. Contrast with intergranular fracture.
An unstable crystallographic configuration that forms as an intermediate step in a solid-state reaction such as precipitation from solid solution or eutectoid decomposition.
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.
A nonequilibrium state that appears in a chemical system in the course of transformation between two equilibrium states.
At a stated pressure, the temperature (or at a stated temperature, the pressure) at which two solid phases exist in equilibrium–that is, an allotropic transformation temperature (or pressure).
In precipitation from solid solution, a metastable precipitate that is coherent with the matrix.
(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, such as the ductile-to-brittle transition temperature (DBTT). The DBTT can be assessed in several ways, the most common being the temperature for 50% ductile and 50% brittle fracture (50% fracture appearance transition temperature, or FATT), or the lowest temperature at which the fracture is 100% ductile (100% fibrous criterion). (2) Sometimes used to denote an arbitrarily defined temperature within a range in which the ductility changes rapidly with temperature.
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.
transverse rolling machine
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.
transverse rupture strength (TRS)
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: 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.
Visible projections of electrodeposited metal formed at sites of high current density.
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.
In a triaxial stress state, the ratio of the smallest to the largest principal stress, all stresses being tensile.
A state of stress in which none of the three principal stresses is zero. See also principal stress (normal).
(1) The science and technology of interacting surfaces in relative motion and of the practices related thereto. (2) The science concerned with the design, friction, lubrication, and wear of contacting surfaces that move relative to each other (as in bearings, cams, or gears, for example).
The portion of the trimmers through which a forging is pushed to shear off the flash.
The punch press die used for trimming flash from a forging.
The upper portion of the trimmer that contacts the forging and pushes it through the trimmer blades; the lower end of the trimmer punch is generally shaped to fit the surface of the forging against which it pushes.
The combination of trimmer punch, trimmer blades, and perhaps trimming shoe used to remove the flash from the forging.
(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.
A power press suitable for trimming flash from forgings.
The holder used to support trimmers. Sometimes called trimming chair.
A mechanical or hydraulic press having three slides with three motions properly synchronized for triple-action drawing, redrawing, and forming. Usually, two slides–the blankholder slide and the plunger–are located above and a lower slide is located within the bed of the press. See also hydraulic press , mechanical press , and slide.
(1) A point on a phase diagram where three phases of a substance coexist in equilibrium. (2) The intersection of the boundaries of three adjoining grains, as observed in a metallographic section.
A commercial steel product exhibiting transformation-induced plasticity.
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.
A unit of weight for precious metals that is equal to 31.1034768 g (1.0971699 oz avoirdupois).
true current density
See preferred term local current density.
(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.
The value obtained by dividing the load applied to a member at a given instant by the cross-sectional area over which it acts.
The removal of the outside layer of abrasive grains on a grinding wheel for the purpose of restoring its face.
The formation of localized corrosion products scattered over the surface in the form of knoblike mounds called tubercles. The formation of tubercles is usually associated with biological corrosion.
Reducing both the diameter and wall thickness of tubing with a mandrel and a pair of rolls. See also spinning.
Drawing tubing through a die or passing it through rolls without the use of an interior tool (such as a mandrel or plug) to control inside diameter; sinking generally produces a tube of increased wall thickness and length.
A semifinished tube suitable for subsequent reduction and finishing.
Rotating workpieces, usually castings or forgings, in a barrel partly filled with metal slugs or abrasives, to remove sand, scale, or fins. It may be done dry, or with an aqueous solution added to the contents of the barrel. See also barrel finishing.
Four undriven working rolls, arranged in a square or rectangular pattern, through which metal strip, wire, or tubing is drawn to form square or rectangular sections.
Removing material by forcing a single-point cutting tool against the surface of a rotating workpiece. The tool may or may not be moved toward or along the axis of rotation while it cuts away material.
An opening in a cupola, blast furnace, or converter for the introduction of air or inert gas.
Two portions of a crystal with a definite orientation relationship; one may be regarded as the parent, the other as the twin. The orientation of the twin is a mirror image of the orientation of the parent across a twinning plane or an orientation that can be derived by rotating the twin portion about a twinning axis. See also annealing twin and mechanical twin.
Bands across a crystal grain, observed on a polished and etched section, where crystallographic orientations have a mirror-image relationship to the orientation of the matrix grain across a composition plane that is usually parallel to the sides of the band.
A subgrain boundary consisting of an array of screw dislocations.
A type of rolling mill in which only two rolls, the working rolls, are contained in a single housing. Compare with four-high mill and cluster mill.
Any of a series of alloys containing lead (58.5 to 95%), antimony (2.5 to 25%), and tin (2.5 to 20%) used to make printing type. Small amounts of copper (1.5 to 2.0%) are added to increase hardness in some applications.