Permission ASM International Copyright © 2001 ASM International®. All Rights Reserved.
In a lathe tool, the surface against which the chips bear as they are formed.
Milling a surface that is perpendicular to the cutter axis.
Cutters that can be mounted directly on and driven from the machine spindle nose.
(1) In machining, generating a surface on a rotating workpiece by the traverse of a tool perpendicular to the axis of rotation. (2) In foundry practice, any material applied in a wet or dry condition to the face of a mold or core to improve the surface of the casting. See also mold wash. (3) For abrasion resistance, see preferred term hardfacing.
A general term used to imply that a part in service (a) has become completely inoperable, (b) is still operable but incapable of satisfactorily performing its intended function, or (c) has deteriorated seriously, to the point that it has become unreliable or unsafe for continued use.
A structural or chemical process, such as corrosion or fatigue, that causes failure.
An insert put in either member of a die set to increase the strength and improve the life of the die.
(1) Damage to a solid bearing surface characterized by indentations not caused by plastic deformation resulting from overload, but thought to be due to other causes such as fretting corrosion. (2) Local spots appearing when the protective film on a metal is broken continually by repeated impacts, usually in the presence of corrosive agents. The appearance is generally similar to that produced by brinelling but corrosion products are usually visible. It may result from fretting corrosion. This term should be avoided when a more precise description is possible. False brinelling (race fretting) can be distinguished from true brinelling because in false brinelling, surface material is removed so that original finishing marks are removed. The borders of a false brinell mark are sharply defined, whereas a dent caused by a rolling element does not have sharp edges and the finishing marks are visible in the bottom of the dent.
The phenomenon leading to fracture under repeated or fluctuating stresses having a maximum value less than the ultimate tensile strength of the material. Fatigue failure generally occurs at loads that applied statically would produce little perceptible effect. Fatigue fractures are progressive, beginning as minute cracks that grow under the action of the fluctuating stress.
fatigue crack growth rate (da/dN)
The rate of crack extension caused by constant-amplitude fatigue loading, expressed in terms of crack extension per cycle of load application, and plotted logarithmically against the stress-intensity factor range, K.
Failure that occurs when a specimen undergoing fatigue completely fractures into two parts or has softened or been otherwise significantly reduced in stiffness by thermal heating or cracking.
fatigue life (N)
(1) The number of cycles of stress or strain of a specified character that a given specimen sustains before failure of a specified nature occurs. (2) The number of cycles of deformation required to bring about failure of a test specimen under a given set of oscillating conditions (stresses or strains). See also S-N curve.
The maximum stress that presumably leads to fatigue fracture in a specified number of stress cycles. The value of the maximum stress and the stress ratio also should be stated. See also endurance limit.
fatigue notch factor (Kf)
The ratio of the fatigue strength of an unnotched specimen to the fatigue strength of a notched specimen of the same material and condition; both strengths are determined at the same number of stress cycles.
fatigue notch sensitivity (q)
An estimate of the effect of a notch or hole of a given size and shape on the fatigue properties of a material, measured by q = (Kf – 1)/(Kt – 1) where Kf is the fatigue notch factor and Kt is the stress-concentration factor. A material is said to be fully notch sensitive if q approaches a value of 1.0; it is not notch sensitive if the ratio approaches 0.
The ratio of fatigue strength to tensile strength. Mean stress and alternating stress must be stated.
The maximum cyclical stress a material can withstand for a given number of cycles before failure occurs.
fatigue strength at N cycles (SN)
A hypothetical value of stress for failure at exactly N cycles as determined from an S-N curve. The value of SN thus determined is subject to the same conditions as those that apply to the S-N curve. The value of SN that is commonly found in the literature is the hypothetical value of maximum stress, Smax, minimum stress Smin, or stress amplitude, Sa, at which 50% of the specimens of a given sample could survive N stress cycles in which the mean stress Sm = 0. This is also known as the median fatigue strength at N cycles. See also S-N curve.
fatigue-strength reduction factor
The ratio of the fatigue strength of a member or specimen with no stress concentration to the fatigue strength with stress concentration. This factor has no meaning unless the stress range and the shape, size, and material of the member or specimen are stated.
Parallel lines frequently observed in electron microscope fractographs or fatigue fracture surfaces. The lines are transverse to the direction of local crack propagation; the distance between successive lines represents the advance of the crack front during the one cycle of stress variation.
A method for determining the range of alternating (fluctuating) stresses a material can withstand without failing.
(1) Removal of particles detached by fatigue arising from cyclic stress variations. (2) Wear of a solid surface caused by fracture arising from material fatigue. See also spalling.
The mating surface of a member that is in contact with or in close proximity to another member to which it is to be joined.
The rate at which a cutting tool or grinding wheel advances along or into the surface of a workpiece, the direction of advance depending on the type of operation involved.
feeder (feeder head, feedhead)
In foundry practice, a riser.
(1) In casting, providing molten metal to a region undergoing solidification, usually at a rate sufficient to fill the mold cavity ahead of the solidification front and to compensate for any shrinkage accompanying solidification. (2) Conveying metal stock or workpieces to a location for use or processing, such as wire to a consumable electrode, strip to a die, or workpieces to an assembler.
Linear marks on a machined or ground surface that are spaced at intervals equal to the feed per revolution or per stroke.
(1) A material that macroscopically has properties similar to those of a ferromagnetic material but that microscopically also resembles an antiferromagnetic material in that some of the elementary magnetic moments are aligned antiparallel. If the moments are of different magnitudes, the material may still have a large resultant magnetization. (2) A material in which unequal magnetic moments are lined up antiparallel to each other. Permeabilities are of the same order of magnitude as those of ferromagnetic materials, but are lower than they would be if all atomic moments were parallel and in the same direction. Under ordinary conditions the magnetic characteristics of ferrimagnetic materials are quite similar to those of ferromagnetic material.
(1) A solid solution of one or more elements in body-centered cubic iron. Unless otherwise designated (for instance, as chromium ferrite), the solute is generally assumed to be carbon. On some equilibrium diagrams, there are two ferrite regions separated by an austenite area. The lower area is ferrite; the upper, ferrite. If there is no designation, ferrite is assumed. (2) An essentially carbon-free solid solution in which iron is the solvent and which is characterized by a body-centered cubic crystal structure. Fully ferritic steels are only obtained when the carbon content is quite low. The most obvious microstructural features in such metals are the ferrite grain boundaries.
Parallel bands of free ferrite aligned in the direction of working. Sometimes referred to as ferrite streaks.
An arbitrary, standardized value designating the ferrite content of an austenitic stainless steel weld metal. This value directly replaces percent ferrite or volume percent ferrite and is determined by the magnetic test described in AWS A4.2
Inhomogeneous distribution of ferrite and pearlite aligned in filaments or plates parallel to the direction of working.
Same as ferrite banding.
ferritic grain size
The grain size of the ferritic matrix of a steel.
See malleable iron.
A treatment given as-cast gray or ductile (nodular) iron to produce an essentially ferritic matrix. For the term to be meaningful, the final microstructure desired or the time-temperature cycle used must be specified.
An alloy of iron that contains a sufficient amount of one or more other chemical elements to be useful as an agent for introducing these elements into molten metal, especially into steel or cast iron.
A crystalline material that exhibits spontaneous electrical polarization, hysteresis, and piezoelectric properties.
The phenomenon whereby certain crystals may exhibit a spontaneous dipole moment (which is called ferroelectric by analogy with ferromagnetism exhibiting a permanent magnetic moment). Ferroelectric crystals often show several Curie points, domain structures, and hysteresis, much as do ferromagnetic crystals.
An instrument used to determine the size distribution of wear particles in lubricating oils of mechanical systems. The technique relies on the debris being capable of being attracted to a magnet.
A material that in general exhibits the phenomena of hysteresis and saturation, and whose permeability is dependent on the magnetizing force. Microscopically, the elementary magnets are aligned parallel in volumes called domains (see domain, magnetic ). The unmagnetized condition of a ferromagnetic material results from the overall neutralization of the magnetization of the domains to produce zero external magnetization.
A property exhibited by certain metals, alloys, and compounds of the transition (iron group), rare-earth, and actinide elements in which, below a certain temperature termed the Curie temperature, the atomic magnetic moments tend to line up in a common direction. Ferromagnetism is characterized by the strong attraction of one magnetized body for another. See also Curie temperature. Compare with paramagnetism.
Metallic materials in which the principal component is iron.
(1) The characteristic of wrought metal that indicates directional properties and is revealed by etching of a longitudinal section or is manifested by the fibrous or woody appearance of a fracture. It is caused chiefly by extension of the constituents of the metal, both metallic and nonmetallic, in the direction of working. (2) The pattern of preferred orientation of metal crystals after a given deformation process, usually wiredrawing. See also fibering and preferred orientation.
Elongation and alignment of internal boundaries, second phases, and inclusions in particular directions corresponding to the direction of metal flow during deformation processing.
The technology of producing solid bodies from fibers or chopped filaments, with or without a metal matrix. The fibers may consist of such nonmetals as graphite or aluminum oxide, or of such metals as tungsten or boron. See also metal-matrix composites.
Local stress through a small area (a point or line) on a section where the stress is not uniform, as in a beam under a bending load.
A gray and amorphous fracture that results when a metal is sufficiently ductile for the crystals to elongate before fracture occurs. When a fibrous fracture is obtained in an impact test, it may be regarded as definite evidence of toughness of the metal. See also crystalline fracture and silky fracture.
(1) In forgings, a structure revealed as laminations, not necessarily detrimental, on an etched section or as a ropy appearance on a fracture. It is not to be confused with silky or ductile fracture of a clean metal. (2) In wrought iron, a structure consisting of slag fibers embedded in ferrite. (3) In rolled steel plate stock, a uniform, fine-grained structure on a fractured surface, free of laminations or shale-type discontinuities.
A fine network of shrinkage cavities, occasionally found in steel castings, that produces a radiographic image resembling lace.
Hardness as determined by the use of a steel file of standardized hardness on the assumption that a material that cannot be cut with the file is as hard as, or harder than, the file. Files covering a range of hardnesses may be employed; the most common are files heat treated to approximately 67 to 70 HRC.
Corrosion that occurs under some coatings in the form of randomly distributed thread-like filaments.
Metal added in making a brazed, soldered, or welded joint. See also brazing filler metal , electrode (welding) , solder , welding rod , and welding wire.
(1) Concave corner piece usually used at the intersection of casting sections. Also the radius of metal at such junctions as opposed to an abrupt angular junction. (2) A radius (curvature) imparted to inside meeting surfaces.
An imprecise term used to denote the last anneal given to a nonferrous alloy prior to shipment.
A polishing process in which the primary objective is to produce a final surface suitable for microscopic examination.
A measure of the purity of gold or silver expressed in parts per thousand.
(1) The product that passes through the finest screen in sorting crushed or ground material. (2) Sand grains that are substantially smaller than the predominating size in a batch or lot of foundry sand. (3) The portion of a powder composed of particles smaller than a specified size, usually 44 m (325 mesh).
Silver with a fineness of three nines (999); equivalent to a minimum content of 99.9% Ag with the remaining content unrestricted.
(1) Surface condition, quality, or appearance of a metal. (2) Stock on a forging or casting to be removed in finish machining. (3) The forging operation in which the part is forged into its final shape in the finish die. If only one finish operation is scheduled to be performed in the finish die, this operation will be identified simply as finish; first, second, or third finish designations are so termed when one or more finish operations are to be performed in the same finish die.
(1) The amount of excess metal surrounding the intended final configuration of a formed part; sometimes called forging envelope, machining allowance, or cleanup allowance. (2) Amount of stock left on the surface of a casting for machining.
A subcritical annealing treatment applied to cold-worked low- or medium-carbon steel. Finish annealing, which is a compromise treatment, lowers residual stresses, thereby minimizing the risk of distortion in machining while retaining most of the benefits to machinability contributed by cold working. Compare with final annealing.
Steel that is ready for the market and has been processed beyond the stages of billets, blooms, sheet bars, slabs, and wire rods.
finisher (finishing impression)
The die impression that imparts the final shape to a forged part.
The final grinding action on a workpiece, of which the objectives are surface finish and dimensional accuracy.
The die set used in the last forging step.
The temperature at which hot working is completed.
A machining process analogous to finish grinding.
A variation of the shielded metal arc welding process in which a length of covered electrode is placed along the joint in contact with the workpieces. During the welding operation, the stationary electrode is consumed as the arc travels the length of the electrode.
Copper that has been refined by the use of a furnace process only, including refinery shapes and, by extension, fabricators’ products made therefrom. Usually, when this term is used alone it refers to fire-refined tough pitch copper without elements other than oxygen being present in significant amounts.
A type of dendrite.
An area on a steel fracture surface having a characteristic white crystalline appearance.
fisheye (weld defect)
A discontinuity found on the fracture surface of a weld in steel that consists of a small pore or inclusion surrounded by an approximately round, bright area.
A scaly appearance in a porcelain enamel coating in which the evolution of hydrogen from the base metal (iron or steel) causes loss of adhesion between the enamel and the base metal. The scales are somewhat like blisters that have cracked partway around the perimeter but still remain attached to the coating around the rest of the perimeter.
(1) In roll forging, the excess trailing end of a forging. It is often used, before being trimmed off, as a tong hold for a subsequent forging operation. (2) In hot rolling or extrusion, the imperfectly shaped trailing end of a bar or special section that must be cut off and discarded as mill scrap.
A small cracklike weld discontinuity with only slight separation (opening displacement) of the fracture surfaces. The prefixes macro or micro indicate relative size.
Grinding in which the wheel is fed into the work, or vice versa, by given increments or at a given rate.
fixed position welding
Welding in which the work is held in a stationary position.
A device designed to hold parts to be joined in proper relation to each other.
A short, discontinuous internal crack in ferrous metals attributed to stresses produced by localized transformation and hydrogen-solubility effects during cooling after hot working. In fracture surfaces, flakes appear as bright, silvery areas with a coarse texture. In deep acid-etched transverse sections, they appear as discontinuities that are usually in the midway to center location of the section. Also termed hairline cracks and shatter cracks.
Graphitic carbon, in the form of platelets, occurring in the microstructure of gray iron.
(1) The removal of material from a surface in the form of flakes or scalelike particles. (2) A form of pitting resulting from fatigue. See also spalling.
Annealing in which the heat is applied directly by a flame.
Cleaning metal surfaces of scale, rust, dirt, and moisture by use of a gas flame.
See preferred term oxygen cutting.
A process for hardening the surfaces of hardenable ferrous alloys in which an intense flame is used to heat the surface layers above the upper transformation temperature, whereupon the workpiece is immediately quenched.
A thermal spraying process in which an oxyfuel gas flame is the source of heat for melting the surfacing material. Compressed gas may or may not be used for atomizing and propelling the surfacing material to the substrate.
Correcting distortion in metal structures by localized heating with a gas flame.
The end surface of a tool that is adjacent to the cutting edge and below it when the tool is in a horizontal position, as for turning.
The loss of relief on the flank of the tool behind the cutting edge due to rubbing contact between the work and the tool during cutting; measured in terms of linear dimension behind the original cutting edge.
A test applied to tubing, involving tapered expansion over a cone. Similar to pin expansion test.
(1) Forming an outward acute-angle flange on a tubular part. (2) Forming a flange by using the head of a hydraulic press.
(1) In forging, metal in excess of that required to fill the blocking or finishing forging impression of a set of dies completely. Flash extends out from the body of the forging as a thin plate at the line where the dies meet and is subsequently removed by trimming. Because it cools faster than the body of the component during forging, flash can serve to restrict metal flow at the line where dies meet, thus ensuring complete filling of the impression. See also closed-die forging. (2) In casting, a fin of metal that results from leakage between mating mold surfaces. (3) In welding, the material that is expelled or squeezed out of a weld joint and that forms around the weld.
A recession of the welding or cutting torch flame into or back of the mixing chamber of the torch.
That portion of flash remaining on a forged part after trimming; usually included in the normal forging tolerances.
In flash welding, the heating portion of the cycle, consisting of a series of rapidly recurring localized short circuits followed by molten metal expulsions, during which time the surfaces to be welded are moved one toward the other at a predetermined speed.
Configuration in the blocking or finishing impression of forging dies designed to restrict or to encourage the growth of flash at the parting line, whichever may be required in a particular case to ensure complete filling of the impression.
The line left on a forging after the flash has been trimmed off.
A very thin final electrodeposited film of metal.
A resistance welding process that produces coalescence at the faying surfaces of abutting members by a flashing action and by the application of pressure after heating is substantially completed. The flashing action, caused by the very high current densities at small contacts between the parts, forcibly expels the material from the joint as the parts are slowly moved together. The weld is completed by a rapid upsetting of the workpieces.
A metal or wood frame used for making and holding a sand mold. The upper part is called the cope; the lower, the drag. See also blind riser.
Forging metal between flat or simple-contour dies by repeated strokes and manipulation of the workpiece. Also known as open-die forging , hand forging, or smith forging.
A rotary end-cutting tool constructed from a flat piece of material, provided with suitable cutting lips at the cutting end.
flat edge trimmer
A machine for trimming notched edges on shells. The slide is cam driven so as to obtain a brief dwell at the bottom of the stroke, at which time the die, sometimes called a shimmy die, oscillates to trim the part.
Welding from the upper side, the face of the weld being horizontal. Also called downhand welding.
(1) A preliminary operation performed on forging stock to position the metal for a subsequent forging operation. (2) The removal of irregularities or distortion in sheets or plates by a method such as roller leveling or stretcher leveling.
Dies used to flatten sheet metal hems, that is, dies that can flatten a bend by closing it. These dies consist of a top and bottom die with a flat surface that can close one section (flange) to another (hem, seam).
A quality test for tubing in which a specimen is flattened to a specified height between parallel plates.
A roughly rectangular or square mill product, narrower than strip, in which all surfaces are rolled or drawn without any previous slitting, shearing, or sawing.
A nonspecific term often used to imply a crack-like discontinuity. See preferred terms discontinuity and defect.
An adjustable pressure-control cam of spring steel strips used to obtain varying pressure during a forming cycle.
A movable jump roll designed to push up against a metal sheet as it passes through a roller leveler. The flex roll can be adjusted to deflect the sheet any amount up to the roll diameter.
Passing metal sheets through a flex roll unit to minimize yield-point elongation in order to reduce the tendency for stretcher strains to appear during forming.
A property of solid material that indicates its ability to withstand a flexural or transverse load.
(1) In metalforming, a die mounted in a die holder or punch mounted in its holder such that a slight amount of motion compensates for tolerance in the die parts, the work, or the press. (2) A die mounted on heavy springs to allow vertical motion in some trimming, shearing, and forming operations.
In tube drawing, an unsupported mandrel that locates itself at the die inside the tube, causing a reduction in wall thickness while the die is reducing the outside diameter of the tube.
A forging in which the top and bottom die impressions are identical, permitting the forging to be turned upside down during the forging operation.
Forming cylindrical, conical and curvilinear shaped parts by power spinning over a rotating mandrel. See also spinning.
The concentration of valuable minerals from ores by agitation of the ground material with water, oil, and flotation chemicals. The valuable minerals are generally wetted by the oil, lifted to the surface by clinging air bubbles, and then floated off.
Movement (slipping or sliding) of essentially parallel planes within an element of a material in parallel directions; occurs under the action of shear stress. Continuous action in this manner, at constant volume and without disintegration of the material, is termed yield, creep, or plastic deformation.
(1) In casting, a characteristic of a foundry sand mixture that enables it to move under pressure or vibration so that it makes intimate contact with all surfaces of the pattern or core box. (2) In welding, brazing, or soldering, the ability of molten filler metal to flow or spread over a metal surface.
(1) Melting of an electrodeposit, followed by solidification, especially of tin plate. (2) Fusion (melting) of a chemically or mechanically deposited metallic coating on a substrate, particularly as it pertains to soldering.
(1) Texture showing the direction of metal flow during hot or cold working. Flow lines can often be revealed by etching the surface or a section of a metal part. See accompanying macrograph. (2) In mechanical metallurgy, paths followed by minute volumes of metal during deformation.
The stress required to produce plastic deformation in a solid metal.
A forging defect caused by metal flow past the base of a rib with resulting rupture of the grain structure.
A modification of the Guerin process for forming sheet metal, the fluid-cell process uses higher pressure and is primarily designed for forming slightly deeper parts, using a rubber pad as either the die or punch. A flexible hydraulic fluid cell forces an auxiliary rubber pad to follow the contour of the form block and exert a nearly uniform pressure at all points on the workpiece. See also fluid forming and rubber-pad forming.
A modification of the Guerin process , fluid forming differs from the fluid-cell process in that the die cavity, called a pressure dome, is not completely filled with rubber, but with hydraulic fluid retained by cup-shaped rubber diaphragm. See also rubber-pad forming.
The ability of liquid metal to run into and fill a mold cavity.
A contained mass of a finely divided solid that behaves like a fluid when brought into suspension in a moving gas or liquid.
fluorescent magnetic-particle inspection
Inspection with either dry magnetic particles or those in a liquid suspension, the particles being coated with a fluorescent substance to increase the visibility of the indications.
fluorescent penetrant inspection
Inspection using a fluorescent liquid that will penetrate any surface opening; after the surface has been wiped clean, the location of any surface flaws may be detected by the fluorescence, under ultraviolet light, of back-seepage of the fluid.
An inspection procedure in which the radiographic image of the subject is viewed on a fluorescent screen, normally limited to low-density materials or thin sections of metals because of the low light output of the fluorescent screen at safe levels of radiation.
(1) As applied to drills, reamers, and taps, the channels or grooves formed in the body of the tool to provide cutting edges and to permit passage of cutting fluid and chips. (2) As applied to milling cutters and hobs, the chip space between the back of one tooth and the face of the following tooth.
Elongated grooves or voids that connect widely spaced cleavage planes.
(1) Forming longitudinal recesses in a cylindrical part, or radial recesses in a conical part. (2) A series of sharp parallel kinks or creases occurring in the arc when sheet metal is roll formed into a cylindrical shape. (3) Grinding the grooves of a twist drill or tap.
(1) In metal refining, a material added to a melt to remove undesirable substances, like sand, ash, or dirt. Fluxing of the melt facilitates the agglomeration and separation of such undesirable constituents from the melt. It is also used as a protective covering for certain molten metal baths. Lime or limestone is generally used to remove sand, as in iron smelting; sand, to remove iron oxide in copper refining. (2) In brazing, cutting, soldering, or welding, material used to prevent the formation of, or to dissolve and facilitate removal of, oxides and other undesirable substances.
flux cored arc welding (FCAW)
An arc welding process that joins metal by heating them with an arc between a continuous tubular filler-metal electrode and the work. Shielding is provided by a flux contained within the consumable tubular electrode. Additional shielding may or may not be obtained from an externally supplied gas or gas mixture. See also flux cored electrode.
flux cored electrode
A composite filler metal electrode consisting of a metal tube or other hollow configuration containing ingredients to provide such functions as shielding atmosphere, deoxidation, arc stabilization, and slag formation. Minor amounts of alloying materials may be included in the core. External shielding may or may not be used.
In magnetism, the number of flux lines per unit area passing through a cross section at right angles. It is given by B = H, where and H are permeability and magnetic-field intensity, respectively.
Imaginary lines used as a means of explaining the behavior of magnetic and other fields. Their concept is based on the pattern of lines produced when magnetic particles are sprinkled over a permanent magnet. Sometimes called magnetic lines of force.
Cutting with a single-tooth milling cutter.
A machine for cutting continuous rolled products to length that does not require a halt in rolling, but rather moves along the runout table at the same speed as the product while performing the cutting, and then returns to the starting point in time to cut the next piece.
Quenching in a fine vapor or mist.
Metal in sheet form less than 0.15 mm (0.006 in.) thick.
(1) A defect in metal, usually on or near the surface, caused by continued fabrication of overlapping surfaces. (2) A forging defect caused by folding metal back onto its own surface during its flow in the die cavity. See also lap.
In foundry practice, a board contoured to a pattern to facilitate the making of a sand mold.
A progressive die consisting of two or more parts in a single holder; used with a separate lower die to perform more than one operation (such as piercing and blanking) on a part in two or more stations.
A quench utilizing blasts of compressed air against relatively small parts such as a gear.
Term used to describe the relative ability of material to deform without fracture. Also describes the resistance to flow from deformation. See also formability.
forged roll Scleroscope hardness number (HFRSc or HFRSd)
A number related to the height of rebound of a diamond-tipped hammer dropped on a forged steel roll. It is measured on a scale determined by dividing into 100 units the average rebound of a hammer from a forged steel roll of accepted maximum hardness. See also Scleroscope hardness number and Scleroscope hardness test.
The macrostructure through a suitable section of a forging that reveals direction of working.
Solid-state welding in which metals are heated in a forge (in air) and then welded together by applying pressure or blows sufficient to cause permanent deformation at the interface.
The process of working metal to a desired shape by impact or pressure in hammers, forging machines (upsetters), presses, rolls, and related forming equipment. Forging hammers, counterblow equipment, and high-energy-rate forging machines apply impact to the workpiece, while most other types of forging equipment apply squeeze pressure in shaping the stock. Some metals can be forged at room temperature, but most are made more plastic for forging by heating. Specific forging processes defined in this glossary include closed-die forging , high-energy-rate forging , hot upset forging , isothermal forging , open-die forging , powder forging , precision forging , radial forging , ring rolling , roll forging , rotary forging , and rotary swaging.
A wrought metal slug used as forging stock.
Forms for making forgings; they generally consist of a top and bottom die. The simplest will form a completed forging in a single impression; the most complex, consisting of several die inserts, may have a number of impressions for the progressive working of complicated shapes. Forging dies are usually in pairs, with part of the impression in one of the blocks and the rest of the impression in the other block.
See finish allowance.
A cast metal slug used as forging stock.
forging machine (upsetter or header)
A type of forging equipment, related to the mechanical press , in which the principal forming energy is applied horizontally to the workpiece, which is gripped and held by prior action of the dies. See also heading , hot upset forging , and upsetting.
In forging, the plane that includes the principal die face and that is perpendicular to the direction of ram travel. When parting surfaces of the dies are flat, the forging plane coincides with the parting line.
Temperature range in which a metal can be forged successfully.
Power-driven rolls used in preforming bar or billet stock that have shaped contours and notches for introduction of the work. See also roll forging.
A wrought rod, bar, or other section suitable for subsequent change in cross section by forging.
The ease with which a metal can be shaped through plastic deformation. Evaluation of the formability of a metal involves measurement of strength, ductility, and the amount of deformation required to cause fracture. The term workability is used interchangeably with formability; however, formability refers to the shaping of sheet metal, while workability refers to shaping materials by bulk forming. See also forgeability.
Tooling, usually the male part, used for forming sheet metal contours; generally used in rubber-pad forming.
Any cutter, profile sharpened or cam relieved, shaped to produce a specified form on the work.
A die used to change the shape of a sheet metal blank with minimal plastic flow.
Grinding with a wheel having a contour on its cutting face that is a mating fit to the desired form.
(1) Making a change, with the exception of shearing or blanking, in the shape or contour of a metal part without intentionally altering its thickness. (2) The plastic deformation of a billet or a blanked sheet between tools (dies) to obtain the final configuration. Metalforming processes are typically classified as bulk forming and sheet forming. Also referred to as metalworking.
forming limit diagram (FLD)
A diagram in which the major strains at the onset of necking in sheet metal are plotted vertically and the corresponding minor strains are plotted horizontally. The onset-of-failure line divides all possible strain combinations into two zones: the safe zone (in which failure during forming is not expected) and the failure zone (in which failure during forming is expected).
A cutter so relieved that by grinding only the tooth face of the original form is maintained throughout its life.
Hot rolling to produce bars having contoured cross sections; not to be confused with roll forming of sheet metal or with roll forging.
A single-edge, nonrotating cutting tool, circular or flat, that produces its inverse or reverse form counterpart upon a workpiece.
Same as direct extrusion. See extrusion.
An accumulation of deposits. This term includes accumulation and growth of marine organisms on a submerged metal surface and also includes the accumulation of deposits (usually inorganic) on heat exchanger tubing. See also biological corrosion.
A commercial establishment or building where metal castings are produced.
Metal in the form of gates, sprues, runners, risers, and scrapped castings of known composition returned to the furnace for remelting.
A type of rolling mill, commonly used for flat-rolled mill products, in which two large-diameter backup rolls are employed to reinforce two smaller work rolls, which are in contact with the product. Either the work rolls or the backup rolls may be driven. Compare with two-high mill and cluster mill.
A press whose slide is actuated by four connections and four cranks, eccentrics, or cylinders, the chief merit being to equalize the pressure at the corners of the slides.
Descriptive treatment of fracture of materials, with specific reference to photographs of the fracture surface. Macrofractography involves photographs at low magnification (<25×); microfractography, photographs at high magnification (>25×).
The irregular surface produced when a piece of metal is broken. See also brittle fracture , cleavage fracture , crystalline fracture , decohesive rupture , dimple rupture , ductile fracture , fibrous fracture , granular fracture , intergranular fracture , silky fracture , and transgranular fracture.
fracture grain size
Grain size determined by comparing a fracture of a specimen with a set of standard fractures. For steel, a fully martensitic specimen is generally used, and the depth of hardening and the prior austenitic grain size are determined.
A quantitative analysis for evaluating structural behavior in terms of applied stress, crack length, and specimen or machine component geometry. See also linear elastic fracture mechanics.
The normal stress at the beginning of fracture. Calculated from the load at the beginning of fracture during a tension test and the original cross-sectional area of the specimen.
The true, normal stress on the minimum cross-sectional area at the beginning of fracture. The term usually applies to tension tests of unnotched specimens.
fracture surface markings
Fracture surface features that may be used to determine the fracture origin location and the nature of the stress that produced the fracture.
Test in which a specimen is broken and its fracture surface is examined with the unaided eye or with a low-power microscope to determine such factors as composition, grain size, case depth, or discontinuities.
A generic term for measures of resistance to extension of a crack. The term is sometimes restricted to results of fracture mechanics tests, which are directly applicable in fracture control. However, the term commonly includes results from simple tests of notched or precracked specimens not based on fracture mechanics analysis. Results from tests of the latter type are often useful for fracture control, based on either service experience or empirical correlations with fracture mechanics tests. See also stress-intensity factor.
The subdivision of a grain into small, discrete crystallite outlined by a heavily deformed network of intersecting slip bands as a result of cold working. These small crystals or fragments differ in orientation and tend to rotate to a stable orientation determined by the slip systems.
A type of segregation revealed as dark spots on a macroetched specimen of a consumable-electrode vacuum-arc-remelted alloy.
The bend obtained by applying forces to the ends of a specimen without the application of force at the point of maximum bending.
The part of the total carbon in steel or cast iron that is present in elemental form as graphite or temper carbon. Contrast with combined carbon.
(1) Ferrite that is formed directly from the decomposition of hypoeutectoid austenite during cooling, without the simultaneous formation of cementite. (2) Ferrite formed into separate grains and not intimately associated with carbides as in pearlite. Also called proeutectoid ferrite.
Pertains to the machining characteristics of an alloy to which one or more ingredients have been introduced to produce small broken chips, lower power consumption, better surface finish, and longer tool life; among such additions are sulfur or lead to steel, lead to brass, lead and bismuth to aluminum, and sulfur or selenium to stainless steel.
See preferred term liquidus and solidus. See also melting point.
That temperature range between liquidus and solidus temperatures in which molten and solid constituents coexist.
A type of wear that occurs between tight-fitting surfaces subjected to cyclic relative motion of extremely small amplitude. Usually, fretting is accompanied by corrosion, especially of the very fine wear debris. Also referred to as fretting corrosion and false brinelling (in rolling-element bearings).
(1) The accelerated deterioration at the interface between contacting surfaces as the result of corrosion and slight oscillatory movement between the two surfaces. (2) A form of fretting in which chemical reaction predominates. Fretting corrosion is often characterized by the removal of particles and subsequent formation of oxides, which are often abrasive and so increase the wear. Fretting corrosion can involve other chemical reaction products, which may not be abrasive.
(1) Fatigue fracture that initiates at a surface area where fretting has occurred. The progressive damage to a solid surface that arises from fretting. Note: If particles of wear debris are produced, then the term fretting wear may be applied.
Wear arising as a result of fretting.
The resisting force tangential to the common boundary between two bodies when, under the action of an external force, one body moves or tends to move relative to the surface of the other.
See coefficient of friction.
friction welding (FRW)
A solid-state welding process that produces coalescence of materials under compressive force contact of workpieces rotating or moving relative to one another to produce heat and plastically displace material from the faying surfaces.
Gases usually used with oxygen for heating such as acetylene, natural gas, hydrogen, propane, stabilized methylacetylene propadiene, and other synthetic fuels and hydrocarbons.
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.
Mild waviness down the center of a metal sheet or strip.
fuller (fullering impression)
Portion of the die used in hammer forging primarily to reduce the cross section and to lengthen a portion of the forging stock. The fullering impression is often used in conjunction with an edger (edging impression).
A temper of nonferrous alloys and some ferrous alloys corresponding approximately to a cold-worked state beyond which the material can no longer be formed by bending. In specifications, a full hard temper is commonly defined in terms of minimum hardness or minimum tensile strength (or, alternatively, a range of hardness or strength) corresponding to a specific percentage of cold reduction following a full anneal. For aluminum, a full hard temper is equivalent to a reduction of 75% from dead soft ; for austenitic stainless steels, a reduction of about 50 to 55%.
A trade name for an expendable pattern casting process in which the polystyrene pattern is vaporized by the molten metal as the mold is poured. See also lost foam casting.
A mass-production brazing process in which the filler metal is preplaced on the joint, then the entire assembly is heated to brazing temperature in a furnace.
fused spray deposit
A self-fluxing spray deposit which is deposited by conventional thermal spraying and subsequently fused using either a heating torch or a furnace.
See preferred terms fusion zone , nugget , and weld interface.
A group of binary, ternary, quaternary, and quinary alloys containing bismuth, lead, tin, cadmium, and indium. The term “fusible alloy” refers to any of more than 100 alloys that melt at relatively low temperatures, that is, below the melting point of tin-lead solder (183 °C, or 360 °F). The melting points of these alloys range as low as 47 °C (116 °F).
The melting together of filler metal and base metal (substrate), or of base metal only, which results in coalescence. See also depth of fusion.
Any welding process that uses fusion of the base metal to make the weld.
The area of base metal melted as determined on the cross section of a weld.