Permission ASM International Copyright © 2001 ASM International®. All Rights Reserved.
Recess in the corner of a metalforming die to allow for wrinkling or folding of the blank.
A term used to describe the placing of metal parts to be heat treated on a rack or tray. This is done to keep parts in a proper position to avoid heat-related distortions and to keep the parts separated.
radial draw forming
The forming of sheet metals by the simultaneous application of tangential stretch and radial compression forces. The operation is done gradually by tangential contact with the die member. This type of forming is characterized by very close dimensional control.
A process using two or more moving anvils or dies for producing shafts with constant or varying diameters along their length or tubes with internal or external variations. Often incorrectly referred to as rotary forging.
Lines on a fracture surface that radiate from the fracture origin and are visible to the unaided eye or at low magnification. Radial marks result from the intersection and connection of brittle fractures propagating at different levels. Also known as shear ledges. See also chevron pattern.
A general term for the alteration of properties of a material arising from exposure to ionizing radiation (penetrating radiation), such as x-rays, gamma rays, neutrons, heavy-particle radiation, or fission fragments in nuclear fuel material. See also neutron embrittlement.
An element that has at least one isotope that undergoes spontaneous nuclear disintegration to emit positive particles, negative particles, or rays.
(1) The property of the nuclei of some isotopes to spontaneously decay (lose energy). Usual mechanisms are emission of , , or other particles and splitting (fissioning). Gamma rays are frequently, but not always, given off in the process. (2) A particular component from a radioactive source, such as radioactivity.
A photographic shadow image resulting from uneven absorption of penetrating radiation in a test object. See also radiography.
A method of nondestructive inspection in which a test object is exposed to a beam of x-rays or rays and the resulting shadow image of the object is recorded on photographic film placed behind the object, or displayed on a viewing screen or television monitor (real-time radiography). Internal discontinuities are detected by observing and interpreting variations in the image caused by differences in thickness, density, or absorption within the test object. See also real-time radiography.
radius of bend
The radius of the cylindrical surface of the pin or mandrel that comes in contact with the inside surface of the bend during bending. In the case of free or semiguided bends to 180° in which a shim or block is used, the radius of bend is one-half the thickness of the shim or block.
The angular relationship between the tooth face, or a tangent to the tooth face at a given point, and a given reference plane or line.
The moving or falling part of a drop hammer or press to which one of the dies is attached; sometimes applied to the upper flat die of a steam hammer. Also referred to as the slide.
(1) Packing foundry sand, refractory, or other material into a compact mass. (2) The compacting of molding (foundry) sand in forming a mold.
A longitudinal welding sequence wherein the weld-bead increments are deposited at random to minimize distortion.
range of stress (Sr)
The algebraic difference between the maximum and minimum stress in one cycle–that is, Sr = Smax – Smin.
The cooling or quenching of liquid (molten) metals at rates that range from 104 to 108 °C/s.
rare earth metal
A group of 17 chemically similar metals that includes the elements scandium and yttrium (atomic numbers 21 and 39, respectively) and the lanthanide elements (atomic numbers 57 through 71).
Progressive cyclic inelastic deformation (growth, for example) that occurs when a component or structure is subjected to a cyclic secondary stress superimposed on a sustained primary stress. The process is called thermal ratcheting when cyclic strain is induced by cyclic changes in temperature, and isothermal ratcheting when cyclic strain is mechanical in origin (even though accompanied by cyclic changes in temperature).
Lines or markings on a fatigue fracture surface that results from the intersection and connection of fatigue fractures propagating from multiple origins. Ratchet marks are parallel to the overall direction of crack propagation and are visible to the unaided eye or at low magnification.
rate of strain hardening
Rate of change of true stress with respect to true strain in the plastic range.
A surface imperfection on a casting, occurring as one or more irregular lines, caused by expansion of sand in the mold. Compare with buckle (2).
The sintering of a metal powder mixture consisting of at least two components that chemically react during the treatment.
A metal that readily combines with oxygen at elevated temperatures to form very stable oxides, for example, titanium, zirconium, and beryllium. Reactive metals may also become embrittled by the interstitial absorption of oxygen, hydrogen, and nitrogen.
A method of nondestructive inspection in which a two-dimensional radiographic image can be immediately displayed on a viewing screen or television monitor. This technique does not involve the creation of a latent image; instead, the unabsorbed radiation is converted into an optical or electronic signal, which can be viewed immediately or can be processed in near real time with electronic and video equipment. See also radiography.
An operation in which a previously formed hole is sized and contoured accurately by using a rotary cutting tool (reamer) with one or more cutting elements (teeth). The principal support for the reamer during the cutting action is obtained from the workpiece.
(1) The increase in temperature that occurs after undercooling, because the rate of liberation of heat during transformation of a material exceeds the rate of dissipation of heat. (2) A phenomenon, associated with the transformation of iron to iron on cooling (supercooling) of iron or steel, that is revealed by the brightening (reglowing) of the metal surface owing to the sudden increase in temperature caused by the fast liberation of the latent heat of transformation. Contrast with decalescence.
(1) To increase the carbon content of molten cast iron or steel by adding carbonaceous material, high-carbon pig iron, or a high-carbon alloy. (2) To carburize a metal part to return surface carbon lost in processing; also known as carbon restoration.
A groove or depression in a surface.
(1) The time-dependent portion of the decrease in strain following unloading of a specimen at the same constant temperature as the initial test. Recovery is equal to the total decrease in strain minus the instantaneous recovery. (2) Reduction or removal of work-hardening effects in metals without motion of large-angle grain boundaries. (3) The proportion of the desired component obtained by processing an ore, usually expressed as a percentage.
(1) The formation of a new, strain-free grain structure from that existing in cold-worked metal, usually accomplished by heating. (2) The change from one crystal structure to another, as occurs on heating or cooling through a critical temperature. (3) A process, usually physical, by which one crystal species is grown at the expense of another or at the expense of others of the same substance but smaller in size. See also crystallization.
Annealing cold-worked metal to produce a new grain structure without phase change.
The approximate minimum temperature at which complete recrystallization of a cold-worked metal occurs within a specified time.
recrystallized grain size
(1) The grain size developed by heating cold-worked metal. The time and temperature are selected so that, although recrystallization is complete, essentially no grain growth occurs. (2) In aluminum and magnesium alloys, the grain size after recrystallization, without regard to grain growth or the recrystallized conditions. See also recrystallization.
Equipment for transferring heat from gaseous products of combustion to incoming air or fuel. The incoming material passes through pipes surrounded by a chamber through which the outgoing gases pass.
A residue, containing a high percentage of iron oxide, obtained in purifying bauxite in the production of alumina in the Bayer process.
This potential of a reversible oxidation-reduction electrode measured with respect to a reference electrode, corrected to the hydrogen electrode, in a given electrode.
The second and successive deep-drawing operations in which cup-like shells are deepened and reduced in cross-sectional dimensions. See also deep drawing.
(1) A compound that causes reduction, thereby itself becoming oxidized. (2) A chemical that, at high temperatures, lowers the state of oxidation of other batch chemicals.
(1) A furnace atmosphere that tends to remove oxygen from substances or materials placed in the furnace. (2) A chemically active protective atmosphere that at elevated temperature will reduce metal oxides to their metallic state. Reducing atmosphere is a relative term and such an atmosphere may be reducing to one oxide but not to another oxide.
(1) A gas flame produced with excess fuel in the inner flame. (2) A gas flame resulting from combustion of a mixture containing too much fuel or too little air. See also neutral flame and oxidizing flame.
(1) In cupping and deep drawing, a measure of the percentage decrease from blank diameter to cup diameter, or of diameter reduction in redrawing. (2) In forging, rolling, and drawing, either the ratio of the original to final cross-sectional area or the percentage decrease in cross-sectional area. (3) A reaction in which there is a decrease in valence resulting from a gain in electrons. Contrast with oxidation.
A pot or tank in which either a water solution of a salt or a fused salt is reduced electrolytically to form free metals or other substances.
reduction in area (RA)
The difference between the original cross-sectional area of a tensile specimen and the smallest area at or after fracture as specified for the material undergoing testing. Also known as reduction of area.
(1) A spool or hub for coiling or feeding wire or strip. (2) To straighten and planish a round bar by passing it between contoured rolls.
Transverse breaks or ridges on successive inner laps of a coil that results from crimping of the lead end of the coil into a gripping segmented mandrel. Also called reel kinks.
A nonpolarizable electrode with a known and highly reproducible potential used for potentiometric and voltammetric analyses. See also calomel electrode.
In materials characterization, a material of definite composition that closely resembles in chemical and physical nature the material with which an analyst expects to deal; used for calibration or standardization. See also standard reference material.
The branch of process metallurgy dealing with the purification of crude or impure metals. Compare with extractive metallurgy.
Melting of an electrodeposit followed by solidification. The surface has the appearance and physical characteristics of a hot dipped surface (especially tin or tin alloy plates). Also called flow brightening.
(1) A material (usually an inorganic, nonmetallic, ceramic material) of very high melting point with properties that make it suitable for such uses as furnace linings and kiln construction. (2) The quality of resisting heat.
(1) A heat-resistant alloy. (2) An alloy having an extremely high melting point. See also refractory metal. (3) An alloy difficult to work at elevated temperatures.
A metal having an extremely high melting point and low vapor pressure; for example, niobium, tantalum, molybdenum, tungsten, and rhenium.
Same as recuperator except that the gaseous products or combustion heat brick checkerwork in a chamber connected to the exhaust side of the furnace while the incoming air and fuel are being heated by the brick checkerwork in a second chamber, connected to the entrance side. At intervals, the gas flow is reversed so that incoming air and fuel contact hot checkerwork while that in the second chamber is being reheated by exhaust gases.
A device for controlling the delivery of welding or cutting gas at some substantially constant pressure.
A quantitative measure of the ability of a product or service to fulfill its intended function for a specified period of time.
Buffing or other abrasive treatment of the high points of an embossed metal surface to produce highlights that contrast with the finish in the recesses.
The magnetic induction remaining in a magnetic circuit after removal of the applied magnetizing force. Sometimes called remanent induction.
The application of pressure to a previously pressed and sintered powder metallurgy compact, usually for the purpose of improving some physical or mechanical property or for dimensional accuracy.
Small quantities of elements unintentionally present in an alloy.
(1) The stress existing in a body at rest, in equilibrium, at uniform temperature, and not subjected to external forces. Often caused by the forming or thermal processing curing process. (2) An internal stress not depending on external forces resulting from such factors as cold working, phase changes, or temperature gradients. (3) Stress present in a body that is free of external forces or thermal gradients. (4) Stress remaining in a structure or member as a result of thermal or mechanical treatment or both. Stress arises in fusion welding primarily because the weld metal contracts on cooling from the solidus to room temperature.
(1) The amount of energy per unit volume released on unloading. (2) The capacity of a material, by virtue of high yield strength and low elastic modulus, to exhibit considerable elastic recovery on release of load.
A grinding wheel bonded with a synthetic resin.
(1) Coating material used to mask or protect selected areas of a substrate from the action of an etchant, solder, or plating. (2) A material applied to prevent flow of brazing filler metal into unwanted areas.
A brazing process in which the heat required is obtained from the resistance to electric current flow in a circuit of which the workpiece is a part.
resistance seam welding
A resistance welding process that produces coalescence at the faying surfaces of overlapped parts progressively along a length of a joint. The weld may be made with overlapping weld nuggets, a continuous weld nugget, or by forging the joint as it is heated to the welding temperature by resistance to the flow of the welding current.
A soldering process in which the heat required is obtained from the resistance to electric current flow in a circuit of which the workpiece is a part.
resistance spot welding
A resistance welding process that produces coalescence at the faying surfaces of a joint by the heat obtained from resistance to the flow of welding current through the workpieces from electrodes that serve to concentrate the welding current and pressure at the weld areas.
A group of welding processes that produce coalescence of metals with resistance heating and pressure. See also flash welding , projection welding , resistance seam welding , and resistance spot welding.
resistance welding electrode
The part(s) of a resistance welding machine through which the welding current and, in most cases, force are applied directly to the work. The electrode may be in the form of a rotating wheel, rotating bar, cylinder, plate, clamp, chuck, or modification thereof.
Any external mechanical force that prevents a part from moving to accommodate changes in dimension due to thermal expansion or contraction. Often applied to weldments made while clamped in a fixture. Compare with constraint.
(1) The striking of a trimmed but slightly misaligned or otherwise faulty forging with one or more blows to improve alignment, improve surface condition, maintain close tolerances, increase hardness, or effect other improvements. (2) A sizing operation in which coining or stretching is used to correct or alter profiles and to counteract distortion. (3) A salvage operation following a primary forging operation in which the parts involved are rehit in the same forging die in which the pieces were last forged.
A vessel used for distillation of volatile materials, as in separation of some metals and in destructive distillation of coal.
A furnace in which the flame used for melting the metal does not impinge on the metal surface itself, but is reflected off the walls of the root of the furnace. The metal is actually melted by the generation of heat from the walls and the roof of the furnace.
Electrolytic cleaning in which a current is passed between electrodes through a solution, and the part is set up as the anode. Also called anodic cleaning.
Redrawing of a sheet metal part in a direction opposite to that of the original drawing.
See preferred term direct current electrode positive (DCEP).
A second drawing operation in a direction opposite to that of the original drawing.
Casting of a continuously stirred semisolid metal slurry. The process involves vigorous agitation of the melt during the early stages of solidification to break up solid dendrites into small spherulites. See also semisolid metal forming.
A long V-shaped or radiused indentation used to strengthen large sheet metal panels. (2) A long, usually thin protuberance used to provide flexural strength to a forging (as in a rib-web forging).
The engineering design, layout, and fabrication of pattern equipment for producing castings; including a study of the casting solidification program, feeding and gating, risering, skimmers, and fitting flasks.
A low-carbon steel containing sufficient iron oxide to give a continuous evolution of carbon monoxide while the ingot is solidifying, resulting in a case or rim of metal virtually free of voids. Sheet and strip products made from rimmed steel ingots have very good surface quality.
ring and circle shear
A cutting or shearing machine with two rotary-disk cutters driven in unison and equipped with a circle attachment for cutting inside circles or rings from sheet metal, where it is impossible to start the cut at the edge of the sheet. One cutter shaft is inclined to the other to provide cutting clearance so that the outside section remains flat and usable. See also circle shear and rotary shear.
The process of shaping weldless rings from pierced disks or shaping thick-wall ring-shaped blanks between rolls that control wall thickness, ring diameter, height, and contour.
A reservoir of molten metal connected to a casting to provide additional metal to the casting, required as the result of shrinkage before and during solidification.
(1) Plates or pieces inserted between the top of a metalforming press bed or bolster and the die to decrease the height of the die space. (2) Spacers placed between bed and housings to increase shut height on a four-piece tie-rod straight-side press.
A term used in fractography to describe a characteristic pattern of cleavage steps running parallel to the local direction of crack propagation on the fracture surfaces of grains that have separated by cleavage.
Joining of two or more members of a structure by means of metal rivets, the unheaded end being upset after the rivet is in place.
Heating an ore to effect some chemical change that will facilitate smelting.
An extra cathode or cathode extension that reduces the current density on what would otherwise be a high-current-density area on work being electroplated.
(1) A copper electrodeposit obtained from copper cyanide plating solution to which Rochelle salt (sodium potassium tartrate) has been added for grain refinement, better anode corrosion, and cathode efficiency. (2) The solution from which a Rochelle copper electrodeposit is obtained.
rock candy fracture
A fracture that exhibits separated-grain facets; most often used to describe an intergranular fracture in a large-grained metal.
A type of guillotine shear that utilizes a curved blade to shear sheet metal progressively from side to side by a rocker motion.
Rockwell hardness number
A number derived from the net increase in the depth of impression as the load on an indenter is increased from a fixed minor load to a major load and then returned to the minor load. Various scales of Rockwell hardness numbers have been developed based on the hardness of the materials to be evaluated. The scales are designated by alphabetic suffixes to the hardness designation. For example, 64 HRC represents the Rockwell hardness number of 64 on the Rockwell C scale. See also Rockwell superficial hardness number.
Rockwell hardness test
An indentation hardness test using a calibrated machine that utilizes the depth of indentation, under constant load, as a measure of hardness. Either a 120° diamond cone with a slightly rounded point or a 1.6 or 3.2 mm ( or in.) diam steel ball is used as the indenter.
Rockwell superficial hardness number
Like the Rockwell hardness number, the superficial Rockwell number is expressed by the symbol HR followed by a scale designation. For example, 81 HR30N represents the Rockwell superficial hardness number of 81 on the Rockwell 30N scale.
Rockwell superficial hardness test
The same test as used to determine the Rockwell hardness number except that smaller minor and major loads are used. In Rockwell testing, the minor load is 10 kgf, and the major load is 60, 100, or 150 kgf. In superficial Rockwell testing, the minor load is 3 kgf, and major loads are 15, 30, or 45 kgf. In both tests, the indenter may be either a diamond cone or a steel ball, depending principally on the characteristics of the material being tested.
A solid round metal section 9.5 mm ( in.) or greater in diameter, whose length is great in relation to its diameter.
(1) A hot mill for rolling rod. (2) A mill for fine grinding, somewhat similar to a ball mill, but employing long steel rods instead of balls to effect grinding.
Curving sheets, bars, and sections by means of rolls. See also bending rolls.
Progressive compacting of metal powders by use of a rolling mill.
roller hearth furnace
A modification of the pusher-type continuous furnace that provides for rollers in the hearth or muffle of the furnace whereby friction is greatly reduced and lightweight trays can be used repeatedly without risk of unacceptable distortion and damage to the work. See also pusher furnace.
roller leveler breaks
Obvious transverse breaks usually about 3 to 6 mm ( to in.) apart caused by the sheet metal fluting during roller leveling. These will not be removed by stretching.
roller leveler lines
Same as leveler lines.
Leveling by passing flat sheet metal stock through a machine having a series of small-diameter staggered rolls that are adjusted to produce repeated reverse bending.
roller stamping die
An engraved roller used for impressing designs and markings on sheet metal.
The flattening of metal sheets that have been rolled in packs by passing them separately through a two-high cold mill with virtually no deformation. Not to be confused with roller leveling.
A process of shaping stock between two driven rolls that rotate in opposite directions and have one or more matching sets of grooves in the rolls; used to produce finished parts or preforms for subsequent forging operations.
Metalforming through the use of power-driven rolls whose contour determines the shape of the product; sometimes used to denote power spinning.
The reduction of the cross-sectional area of metal stock, or the general shaping of metal products, through the use of rotating rolls. See also rolling mills.
Repeated stressing of a solid surface due to rolling contact between it and another solid surface or surfaces. Continued rolling-contact fatigue of bearing or gear surfaces may result in rolling-contact damage in the form of subsurface fatigue cracks and/or material pitting and spallation.
Machines used to decrease the cross-sectional area of metal stock and to produce certain desired shapes as the metal passes between rotating rolls mounted in a framework comprising a basic unit called a stand. Cylindrical rolls produce flat shapes; grooved rolls produce rounds, squares, and structural shapes. See also four-high mill , Sendzimir mill , and two-high mill.
The straightening of metal stock of various shapes by passing it through a series of staggered rolls, the rolls usually being in horizontal and vertical planes, or by reeling in two-roll straightening machines.
See preferred term thread rolling.
Solid-state welding in which metals are heated, then welded together by applying pressure, with rolls, sufficient to cause deformation at the faying surfaces. See also forge welding.
A crack in either the weld or heat-affected zone at the root of a weld.
(1) Rounded configuration of microconstituents in metals arranged in whorls or radiating from a center. (2) Strain gages arranged to indicate at a single position strains in three different directions.
A process in which the workpiece is pressed between a flat anvil and a swiveling (rocking) die with a conical working face; the platens move toward each other during forging. Also called orbital forging. Compare with radial forging.
A circular furnace constructed so that the hearth and workpieces rotate around the axis of the furnace during heating. Also called rotary hearth furnace.
A machine for forming powder metallurgy parts that is fitted with a rotating table carrying multiple die assemblies in which powder is compacted.
rotary retort furnace
A continuous-type furnace in which the work advances by means of an internal spiral, which gives good control of the retention time within the heated chamber.
A sheet metal cutting machine with two rotating-disk cutters mounted on parallel shafts driven in unison.
A swaging machine consisting of a power-driven ring that revolves at high speed, causing rollers to engage cam surfaces and force the dies to deliver hammerlike blows on the work at high frequency. Both straight and tapered sections can be produced.
A bulk forming process for reducing the cross-sectional area or otherwise changing the shape of bars, tubes, or wires by repeated radial blows with one or more pairs of opposed dies.
A highly reflective finish produced with rouge (finely divided, hydrated iron oxide) or other very fine abrasive, similar in appearance to the bright polish or mirror finish on sterling silver utensils.
A blank for a metalforming or drawing operation, usually of irregular outline, with necessary stock allowance for process metal, which is trimmed after forming or drawing to the desired size.
Grinding without regard to finish, usually to be followed by a subsequent operation.
The first stand (or several stands) of rolls through which a reheated billet passes in front of the finishing stands. See also rolling mills and stand.
Machining without regard to finish, usually to be followed by a subsequent operation.
(1) Relatively finely spaced surface irregularities, the heights, widths, and directions of which establish the predominant surface pattern. (2) The microscopic peak-to-valley distances of surface protuberances and depressions. See also surface roughness.
Forming a sheet metal wherein rubber or another resilient material is used as a functional die part. Processes in which rubber is employed only to contain the hydraulic fluid are not classified as rubber forming.
A sheet metal forming operation for shallow parts in which a confined, pliable rubber pad attached to the press slide (ram) is forced by hydraulic pressure to become a mating die for a punch or group of punches placed on the press bed or baseplate. Also known as the Guerin process. Variations of the Guerin process include the fluid-cell process , fluid forming , and Marforming process.
A grinding wheel made with a rubber bond.
(1) A channel through which molten metal flows from one receptacle to another. (2) The portion of the gate assembly of a casting that connects the sprue with the gate(s). (3) Parts of patterns and finished castings corresponding to the portion of the gate assembly described in (2).
A distribution box that divides molten metal into several streams before it enters the casting mold cavity.
(1) The unintentional escape of molten metal from a mold, crucible, or furnace. (2) An imperfection in a casting caused by the escape of metal from the mold.
The stress at failure. Also known as breaking stress or fracture stress.
A visible corrosion product consisting of hydrated oxides of iron. Applied only to ferrous alloys. See also white rust.