A B C DE F G H I J K L M N O P Q R Sa-Sq St-Sy T U V W X Y Z
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damage tolerance
(1) A design measure of crack growth rate. Cracks in damage-tolerant designed structures are not permitted to grow to critical size during expected service life. (2) The ability of a part component, such as an aerospace engine, to resist failure due to the presence of flaws, cracks, or other damage for a specified period of usage. The damage tolerance approach is used extensively in the aerospace industry.
damping
The loss in energy, as dissipated heat, that results when a material or material system is subjected to an oscillatory load or displacement.
damping capacity
The ability of a material to absorb vibration (cyclical stresses) by internal friction, converting the mechanical energy into heat.
daylight
The distance, in the open position, between the moving and the fixed tables or the platens of a hydraulic press. In the case of a multiplaten press, daylight is the distance between adjacent platens. Daylight provides space for removal of the molded/formed part from the mold/die.
dc casting
Same as direct chill casting.
dead soft
A temper of nonferrous alloys and some ferrous alloys corresponding to the condition of minimum hardness and tensile strength produced by full annealing.
dealloying
The selective corrosion of one or more components of a solid solution alloy. Also called parting or selective leaching . See also decarburization , decobaltification , denickelification , dezincification , and graphitic corrosion.
deburring
Removing burrs, sharp edges, or fins from metal parts by filing, grinding, or rolling the work in a barrel containing abrasives suspended in a suitable liquid medium. Sometimes called burring.
decalescence
A phenomenon, associated with the transformation of iron to iron on the heating (superheating) of iron or steel, revealed by the darkening of the metal surface owing to the sudden decrease in temperature caused by the fast absorption of the latent heat of transformation. Contrast with recalescence.
decarburization
Loss of carbon from the surface layer of a carbon-containing alloy due to reaction with one or more chemical substances in a medium that contacts the surface.
decobaltification
Corrosion in which cobalt is selectively leached from cobalt-base alloys or from cemented carbides with cobalt binders. See also dealloying and selective leaching.
decohesive rupture
A brittle fracture that exhibits little or no bulk plastic deformation and does not occur by dimple rupture, cleavage, or fatigue. This type of fracture is generally the result of a reactive environment or a unique microstructure and is associated almost exclusively with rupture along grain boundaries.
decomposition
Separation of a compound into its chemical elements or components.
decomposition potential (or voltage)
The potential of a metal surface necessary to decompose the electrolyte of a cell or a component thereof.
deep drawing
Forming deeply recessed parts by forcing sheet metal to undergo plastic flow between dies, usually without substantial thinning of the sheet.
deep etching
In metallography, macroetching, especially for steels, to determine the overall character of the material, that is, the presence of imperfections, such as seams, forging bursts, shrinkage-void remnants, cracks, and coring.
defect
(1) A discontinuity whose size, shape, orientation, or location makes it detrimental to the useful service of the part in which it occurs. (2) A discontinuity or discontinuities which by nature or accumulated effect (for example, total crack length) render a part or product unable to meet minimum applicable acceptance standards or specifications. This term designates rejectability. See also discontinuity and flaw.
defective
A quality control term, describing a unit of product or service containing at least one defect , or having several lesser imperfections that, in combination, cause the unit not to fulfill its anticipated function.
deflection
In metalforming and forging, the amount of deviation from a straight line or plane when a force is applied to a press member. Generally used to specify the allowable bending of the bed, slide, or frame at rated capacity with a load of predetermined distribution.
deformation
A change in the form of a body due to stress, thermal change, change in moisture, or other causes. Measured in units of length.
deformation bands
Parts of a crystal that have rotated differently during deformation to produce bands of varied orientation without individual grains.
deformation limit
In drawing, the limit of deformation is reached when the load required to deform the flange becomes greater than the load-carrying capacity of the cup wall. The deformation limit (limiting drawing ratio, LDR) is defined as the ratio of the maximum blank diameter that can be drawn into a cup without failure, to the diameter of the punch.
degasifier
A substance that can be added to molten metal to remove soluble gases that might otherwise be occluded or entrapped in the metal during solidification.
degassing
(1) A chemical reaction resulting from a compound added to molten metal to remove gases from the metal. Inert gases are often used in this operation. (2) A fluxing procedure used for aluminum alloys in which nitrogen, chlorine, chlorine and nitrogen, and chlorine and argon are bubbled up through the metal to remove dissolved hydrogen gases and oxides from the alloy. See also flux.
degradation
A deleterious change in the chemical structure, physical properties, or appearance of a material.
degreasing
The removal of grease and oils from a surface. Can be accomplished by immersion in liquid organic solvent, by solvent vapors condensing on the parts being cleaned (vapor degreasing), or by spraying the parts with solvent.
delayed yield
A phenomenon involving a delay in time between the application of a stress and the occurrence of the corresponding yield-point strain.
delta ferrite
See ferrite.
Demarest process
A fluid forming process in which cylindrical and conical sheet metal parts are formed by a modified rubber bulging punch. The punch, equipped with a hydraulic cell, is placed inside the workpiece, which in turn is placed inside the die. Hydraulic pressure expands the punch.
dendrite
A crystal that has a treelike branching pattern, being most evident in cast metals slowly cooled through the solidification range.
dendritic powder
Particles usually of electrolytic origin typically having the appearance of a pine tree.
denickelification
Corrosion in which nickel is selectively leached from nickel-containing alloys. Most commonly observed in copper-nickel alloys after extended service in fresh water. See also dealloying and selective leaching.
density, absolute
The mass per unit volume of a solid material, expressed in g/cm3, kg/m3, or lb/ft3.
density ratio
The ratio of the determined density of a powder compact to the absolute density of metal of the same composition, usually expressed as a percentage. Also referred to as percent theoretical density.
deoxidation
Removal of excess oxygen from the molten metal; usually accomplished by adding materials with a high affinity for oxygen.
deoxidation products
Those nonmetallic inclusions that form as a result of adding deoxidizing agents to molten metal.
deoxidized copper
Copper from which cuprous oxide has been removed by adding a deoxidizer , such as phosphorus, to the molten bath.
deoxidizer
A substance that can be added to molten metal to remove either free or combined oxygen.
deoxidizing
(1) The removal of oxygen from molten metals through the use of a suitable deoxidizer. (2) Sometimes refers to the removal of undesirable elements other than oxygen through the introduction of elements or compounds that readily react with them. (3) In metal finishing, the removal of oxide films from metal surfaces by chemical or electrochemical reaction.
dephosphorization
The elimination of phosphorus from molten steel.
depolarization
A decrease in the polarization of an electrode.
deposit corrosion
Corrosion occurring under or around a discontinuous deposit on a metallic surface. Also called poultice corrosion.
deposition efficiency (arc welding)
The ratio of the weight of deposited metal to the net weight of filler metal consumed, exclusive of stubs.
deposition sequence
The order in which the increments of weld metal are deposited.
depth of cut
The thickness of material removed from a workpiece in a single machining part.
depth of fusion
The distance that fusion extends into the base metal or previous pass from the surface melted during welding.
descaling
(1) Removing the thick layer of oxides formed on some metals at elevated temperatures. (2) A chemical or mechanical process for removing scale or investment material from castings.
desulfurizing
The removal of sulfur from molten metal by reaction with a suitable slag or by the addition of suitable compounds.
detonation flame spraying
A thermal spraying process variation in which the controlled explosion of a mixture of fuel gas, oxygen, and powdered coating material is utilized to melt and propel the material to the workpiece.
detritus
See wear debris.
developed blank
A sheet metal blank that yields a finished part without trimming or with the least amount of trimming.
dewaxing
In casting, the process of removing the expendable wax pattern from an investment mold or shell mold; usually accomplished by melting out the application of heat or dissolving the wax with an appropriate solvent.
dezincification
Corrosion in which zinc is selectively leached from zinc-containing alloys leaving a relatively weak layer of copper and copper oxide. Most commonly found in copper-zinc alloys containing less than 85% Cu after extended service in water containing dissolved oxygen. See also dealloying and selective leaching.
diamagnetic material
A material whose specific permeability is less than unity and is therefore repelled weakly by a magnet. Compare with ferromagnetic material and paramagnetic material.
diamond pyramid hardness test
See Vickers hardness test.
diamond tool
(1) A diamond, shaped or formed to the contour of a single-point cutting tool, for use in precision machining of nonferrous or nonmetallic materials. (2) An insert made from polycrystalline diamond compacts.
diamond wheels
A grinding wheel in which crushed and sized industrial diamonds are held in a resinoid, metal, or vitrified bond.
diaphragm
(1) A porous or permeable membrane separating anode and cathode compartments of an electrolytic cell from each other or from an intermediate compartment. (2) Universal die member made of rubber or similar material used to contain hydraulic fluid within the forming cavity and to transmit pressure to the part being formed.
dichromate treatment
A chromate conversion coating produced on magnesium alloys in a boiling solution of sodium dichromate.
didymium
A natural mixture of the rare-earth elements praseodymium and neodymium, often given the quasi-chemical symbol Di.
die
A tool, usually containing a cavity, that imparts shape to solid, molten, or powdered metal primarily because of the shape of the tool itself. Used in many press operations (including blanking, drawing, forging, and forming), in die casting, and in forming green powder metallurgy compacts. Die-casting and powder metallurgy dies are sometimes referred to as molds . See also forging dies.
die block
A block, often made of heat-treated steel, into which desired impressions are machined or sunk and from which closed-die forgings or sheet metal stampings are produced using hammers or presses. In forging, die blocks are usually used in pairs, with part of the impression in one of the blocks and the rest of the impression in the other. In sheet metal forming, the female die is used in conjunction with a male punch. See also closed-die forging.
die body
The stationary or fixed part of a powder pressing die.
die casting
(1) A casting made in a die. (2) A casting process in which molten metal is forced under high pressure into the cavity of a metal mold. See also cold chamber machine and hot chamber machine.
die cavity
The machined recess that gives a forging or stamping its shape.
die clearance
Clearance between a mated punch and die; commonly expressed as clearance per side. Also called clearance or punch-to-die clearance.
die cushion
A press accessory placed beneath or within a bolster plate or die block to provide an additional motion or pressure for stamping or forging operations; actuated by air, oil, rubber, springs, or a combination of these.
die forging
A forging that is formed to the required shape and size through working in machined impressions in specially prepared dies.
die forming
The shaping of solid or powdered metal by forcing it into or through the die cavity.
die holder
A plate or block, on which the die block is mounted, having holes or slots for fastening to the bolster plate or the bed of the press.
die impression
The portion of the die surface that shapes a forging or sheet metal part.
die insert
A relatively small die that contains part or all of the impression of a forging or sheet metal part and is fastened to the master die block.
die life
The productive life of a die impression, usually expressed as the number of units produced before the impression has worn beyond permitted tolerances.
die lubricant
(1) A lubricant applied to the working surfaces of dies and punches to facilitate drawing, pressing, stamping, and/or ejection. In powder metallurgy, the die lubricant is sometimes mixed into the powder before pressing into a compact. (2) A compound that is sprayed, swabbed, or otherwise applied on die surfaces or the workpiece during the forging or forming process to reduce friction. Lubricants also facilitate release of the part from the dies and provide thermal insulation. See also lubricant.
die match
The condition where dies, after having been set up in a press or other equipment, are in proper alignment relative to each other.
die opening
(1) In flash or upset welding, the distance between the electrodes, usually measured with the parts in contact before welding has commenced or immediately upon completion of the cycle but before upsetting. (2) In powder metallurgy, the entrance to the die cavity.
die proof
A casting of a die impression made to confirm the accuracy of the impression.
die radius
The radius on the exposed edge of a deep-drawing die, over which the sheet flows in forming drawn shells.
die set
A tool or tool holder consisting of a die base and punch plate for the attachment of a die and punch, respectively.
die shift
The condition that occurs after the dies have been set up in a forging unit in which a portion of the impression of one die is not in perfect alignment with the corresponding portion of the other die. This results in a mismatch in the forging, a condition that must be held within the specified tolerance.
die sinking
The machining of the die impressions to produce forgings of required shapes and dimensions.
die stamping
The general term for a sheet metal part that is formed, shaped, or cut by a die in a press in one or more operations.
die welding
See preferred terms forge welding and cold welding.
differential aeration cell
An electrolytic cell, the electromagnetic force of which is due to a difference in air (oxygen) concentration at one electrode as compared with that at another electrode of the same material. See also concentration cell.
differential coating
A coated product having a specified coating on one surface and a significantly lighter coating on the other surface (such as a hot dip galvanized product or electrolytic tin plate).
differential floatation
Separating a complex ore into two or more valuable minerals and gangue by flotation. Also called selective flotation.
differential heating
Heating that intentionally produces a temperature gradient within an object such that, after cooling, a desired stress distribution or variation in properties is present within the object.
diffusion
(1) Spreading of a constituent in a gas, liquid, or solid, tending to make the composition of all parts uniform. (2) The spontaneous movement of atoms or molecules to new sites within a material.
diffusion aid
A solid filler metal sometimes used in diffusion welding .
diffusion bonding
See preferred terms diffusion welding and diffusion brazing.
diffusion brazing
A brazing process that produces coalescence of metals by heating them to suitable temperatures and by using a filler metal or an in situ liquid phase. The filler metal may be distributed by capillary action or may be placed or formed at the faying surfaces. The filler metal is diffused with the base metal to the extent that the joint properties have been changed to approach those of the base metal. Pressure may or may not be applied.
diffusion coating
Any process whereby a base metal or alloy is either (1) coated with another metal or alloy and heated to a sufficient temperature in a suitable environment or (2) exposed to a gaseous or liquid medium containing the other metal or alloy, thus causing diffusion of the coating or of the other metal or alloy into the base metal with resultant changes in the composition and properties of its surface.
diffusion coefficient
A factor of proportionality representing the amount of substance diffusing across a unit area through a unit concentration gradient in unit time.
diffusion welding
A solid-state welding process that produces coalescence of the faying surfaces by the application of pressure at elevated temperature. The process does not involve macroscopic deformation, melting, or relative motion of parts. A solid filler metal (diffusion aid) may or may not be inserted between the faying surfaces. See also forge welding , hot pressure welding , and cold welding .
dilatometer
An instrument for measuring the linear expansion or contraction in a metal resulting from changes in such factors as temperature and allotropy.
dimple rupture
A fractographic term describing ductile fracture that occurs through the formation and coalescence of microvoids along the fracture path. The fracture surface of such a ductile fracture appears dimpled when observed at high magnification and usually is most clearly resolved when viewed in a scanning electron microscope.
dimpling
(1) The stretching of a relatively small, shallow indentation into sheet metal. (2) In aircraft, the stretching of metal into a conical flange for a countersunk head rivet.
dip brazing
A brazing process in which the heat required is furnished by a molten chemical or metal bath. When a molten chemical bath is used, the bath may act as a flux . When a molten metal bath is used, the bath provides the filler metal.
dip coat
(1) In the solid mold technique of investment casting, an extremely fine ceramic precoat applied as a slurry directly to the surface of the pattern to reproduce maximum surface smoothness. This coating is surrounded by coarser, less expensive, and more permeable investment to form the mold. (2) In the shell mold technique of investment casting, an extremely fine ceramic coating called the first coat, applied as a slurry directly to the surface of the pattern to reproduce maximum surface smoothness. The first coat is followed by other dip coats of different viscosity and usually containing different grading of ceramic particles. After each dip, coarser stucco material is applied to the still-wet coating. A buildup of several coats forms an investment shell mold. See also investment casting .
diphase cleaning
Removing soil by an emulsion that produces two phases in the cleaning tank: a solvent phase and an aqueous phase. Cleaning is effected by both solvent action and emulsification.
dip plating
Same as immersion plating.
dip soldering
A soldering process in which the heat required is furnished by a molten metal bath that provides the solder filler metal.
direct chill casting
A continuous method of making ingots for rolling or extrusion by pouring the metal into a short mold. The base of the mold is a platform that is gradually lowered while the metal solidifies, the frozen shell of metal acting as a retainer for the liquid metal below the wall of the mold. The ingot is usually cooled by the impingement of water directly on the mold or on the walls of the solid metal as it is lowered. The length of the ingot is limited by the depth to which the platform can be lowered; therefore, it is often called semicontinuous casting.
direct current arc furnace
An electric arc furnace in which a single electrode positioned at the center of the furnace roof is the cathode of the system. Current passes from the electrode through the charge or bath to a cathode located at the bottom of the furnace. Current from the bottom of the furnace then passes through the furnace refractories to a copper base plate to outside cables. Used in the production of ferroalloys, carbon and alloy steels, and stainless steels. See also arc furnace .
direct current electrode negative (DCEN)
The arrangement of direct current arc welding leads in which the work is the positive pole and the electrode is the negative pole of the welding arc. Also referred to as straight polarity.
direct current electrode positive (DCEP)
The arrangement of direct current arc welding leads in which the work is the negative pole and the electrode is the positive pole of the welding arc. Also referred to as reverse polarity.
direct current reverse polarity (DCRP)
See direct current electrode positive.
direct current straight polarity (DCSP)
See direct current electrode negative .
direct (forward) extrusion
See extrusion.
directional property
Property whose magnitude varies depending on the relation of the test axis to a specific direction within the metal. The variation results from preferred orientation or from fibering of constituents or inclusions.
directional solidification
Controlled solidification of molten metal in a casting so as to provide feed metal to the solidifying front of the casting.
direct quenching
(1) Quenching carburized parts directly from the carburizing operation. (2) Also used for quenching pearlitic malleable parts directly from the malleabilizing operation.
discontinuity
(1) Any interruption in the normal physical structure or configuration of a part, such as cracks, laps, seams, inclusions, or porosity. A discontinuity may or may not affect the utility of the part. (2) An interruption of the typical structure of a weldment, such as a lack of homogeneity in the mechanical, metallurgical, or physical characteristics of the material or weldment. A discontinuity is not necessarily a defect. See also defect and flaw.
discontinuous precipitation
Precipitation from a supersaturated solid solution in which the precipitate particles grow by short-range diffusion, accompanied by recrystallization of the matrix in the region of precipitation. Discontinuous precipitates grow into the matrix from nuclei near grain boundaries, forming cells of alternate lamellae of precipitate and depleted (and recrystallized) matrix. Often referred to as cellular or nodular precipitation. Compare with continuous precipitation and localized precipitation.
discontinuous yielding
The nonuniform plastic flow of a metal exhibiting a yield point in which plastic deformation is inhomogeneously distributed along the gage length. Under some circumstances, it may occur in metals not exhibiting a distinct yield point, either at the onset of or during plastic flow.
dishing
Forming a shallow concave surface, the area being large compared to the depth.
disk grinding
Grinding with the flat side of an abrasive disk or segmented wheel. Also called vertical-spindle surface grinding.
dislocation
A linear imperfection in a crystalline array of atoms. Two basic types are recognized: (1) an edge dislocation corresponds to the row of mismatched atoms along the edge formed by an extra, partial plane of atoms within the body of a crystal; (2) a screw dislocation corresponds to the axis of a spiral structure in a crystal, characterized by a distortion that joins normally parallel planes together to form a continuous helical ramp (with a pitch of one interplanar distance) winding about the dislocation. Most prevalent is the so-called mixed dislocation, which is any combination of an edge dislocation and a screw dislocation.
disordered structure
The crystal structure of a solid solution in which the atoms of different elements are randomly distributed relative to the available lattice sites. Contrast with ordered structure.
disordering
Forming a lattice arrangement in which the solute and solvent atoms of a solid solution occupy lattice sites at random. See also superlattice.
dispersing agent
A substance that increases the stability of a suspension of particles in a liquid medium by deflocculation of the primary particles.
dispersion hardening
See dispersion strengthening.
dispersion-strengthened material
A metallic material that contains a fine dispersion of nonmetallic phase(s), such as Al2O3, MgO, SiO2, CdO, ThO2, Y2O3, or ZrO2 singly or in combination, to increase the hot strength of the metallic matrix. Examples include dispersion-strengthened copper (Al2O3) used for welding electrodes, silver (CdO) used for electrical contacts, and nickel-chromium (Y2O3) superalloys used for gas turbine components. See also mechanical alloying.
dispersion strengthening
The strengthening of a metal or alloy by incorporating chemically stable submicron size particles of a nonmetallic phase that impede dislocation movement at elevated temperature.
dispersoid
Finely divided particles of relatively insoluble constituents visible in the microstructure of certain metallic alloys.
distortion
Any deviation from an original size, shape, or contour that occurs because of the application of stress or the release of residual stress.
disturbed metal
The cold-worked metal layer formed at a polished surface during the process of mechanical grinding and polishing.
divided cell
A cell containing a diaphragm or other means for physically separating the anolyte from the catholyte.
divorced eutectic
A metallographic appearance in which the two constituents of a eutectic structure appear as massive phases rather than the finely divided mixture characteristic of normal eutectics. Often, one of the constituents of the eutectics is continuous and indistinguishable from an accompanying proeutectic constituent.
domain, magnetic
A substructure in a ferromagnetic material within which all the elementary magnets (electron spins) are held aligned in one direction by interatomic forces; if isolated, a domain would be a saturated permanent magnet.
double-acting hammer
A forging hammer in which the ram is raised by admitting steam or air into a cylinder below the piston, and the blow intensified by admitting steam or air above the piston on the downward stroke.
double-action die
A die designed to perform more than one operation in a single stroke of the press.
double-action forming
Forming or drawing in which more than one action is achieved in a single stroke of the press.
double-action mechanical press
A press having two independent parallel movements by means of two slides, one moving within the other. The inner slide or plunger is usually operated by a crankshaft; the outer or blankholder slide, which dwells during the drawing operation, is usually operated by a toggle mechanism or by cams. See also slide.
double aging
Employment of two different aging treatments to control the type of precipitate formed from a supersaturated matrix in order to obtain the desired properties. The first aging treatment, sometimes referred to as intermediate or stabilizing, is usually carried out at higher temperature than the second.
double tempering
A treatment in which a quench-hardened ferrous metal is subjected to two complete tempering cycles, usually at substantially the same temperature, for the purpose of ensuring completion of the tempering reaction and promoting stability of the resulting microstructure.
double-welded joint
In arc and oxyfuel gas welding, any joint welded from both sides.
downgate
Same as sprue.
downhand welding
See flat-position welding.
down milling
See preferred term climb milling.
downsprue
Same as sprue.
Dow process
A process for the production of magnesium by electrolysis of molten magnesium chloride.
draft
(1) An angle or taper on the surface of a pattern, core box, punch, or die (or of the parts made with them) that facilitates removal of the parts from a mold or die cavity, or a core from a casting. (2) The change in cross section that occurs during rolling or cold drawing.
drag
The bottom section of a flask , mold , or pattern.
drag
(thermal cutting). The offset distance between the actual and the theoretical exit points of the cutting oxygen stream measured on the exit surface of the material.
drawability
A measure of the formability of a sheet metal subject to a drawing process. The term is usually used to indicate the ability of a metal to be deep drawn. See also drawing and deep drawing.
draw bead
An insert or riblike projection on the draw ring or hold-down surfaces that aids in controlling the rate of metal flow during deep draw operations. Draw beads are especially useful in controlling the rate of metal flow in irregularly shaped stampings.
drawbench
The stand that holds the die and draw head used in drawing of wire, rod, and tubing.
draw forging
See radial forging.
draw forming
A method of curving bars, tubes, or rolled or extruded sections in which the stock is bent around a rotating form block. Stock is bent by clamping it to the form block, then rotating the form block while the stock is pressed between the form block and a pressure die held against the periphery of the form block.
draw head
Set of rolls or dies mounted on a drawbench for forming a section from strip, tubing, or solid stock. See also Turk’s-head rolls.
drawing
A term used for a variety of forming operations, such as deep drawing a sheet metal blank; redrawing a tubular part; and drawing rod, wire, and tube. The usual drawing process with regard to sheet metal working in a press is a method for producing a cuplike form from a sheet metal disk by holding it firmly between blankholding surfaces to prevent the formation of wrinkles while the punch travel produces the required shape.
drawing compound
(1) A substance applied to prevent pickup and scoring during drawing or pressing operations by preventing metal-to-metal contact of the work and die. Also known as die lubricant . (2) In metalworking, a lubricant having extreme-pressure properties. See also extreme-pressure lubricant.
drawing out
A stretching operation resulting from forging a series of upsets along the length of the workpiece.
draw marks
See scoring , galling , and pickup.
drawn shell
An article formed by drawing sheet metal into a hollow structure having a predetermined geometrical configuration.
draw plate
(1) In metalforming, a circular plate with a hole in the center contoured to fit a forming punch; used to support the blank during the forming cycle. (2) In casting, a plate attached to a pattern to facilitate drawing of a pattern from the mold.
draw radius
The radius at the edge of a die or punch over which sheet metal is drawn.
draw ring
A ring-shaped die part (either the die ring itself or a separate ring) over which the inner edge of sheet metal is drawn by the punch.
draw stock
The forging operation in which the length of a metal mass (stock) is increased at the expense of its cross section; no upset is involved. The operation includes converting ingot to pressed bar using “V,” round, or flat dies.
dressing
(1) Cutting, breaking down, or crushing the surface of a grinding wheel to improve its cutting ability and accuracy. (2) Removing dulled grains from the cutting face of a grinding wheel to restore cutting quality.
drift
(1) A flat piece of steel of tapering width used to remove taper shank drills and other tools from their holders. (2) A tapered rod used to force mismated holes into line for riveting or bolting. Sometimes called a drift pin.
drilling
Hole making with a rotary end-cutting tool having one or more cutting lips and one or more helical or straight flutes or tubes for the ejection of chips and the passage of a cutting fluid.
drop forging
(1) The forging obtained by hammering metal in a pair of closed dies to produce the form in the finishing impression under a drop hammer. (2) Forging method requiring special dies for each shape.
drop hammer
A term generally applied to forging hammers in which energy for forging is provided by gravity, steam, or compressed air. See also air-lift hammer , board hammer , and steam hammer.
drop hammer forming
A process for producing shapes by the progressive deformation of sheet metal in matched dies under the repetitive blows of a gravity-drop or power-drop hammer. The process is restricted to relatively shallow parts and thin sheet from approximately 0.6 to 1.6 mm (0.024 to 0.064 in.).
droplet erosion
Erosive wear caused by the impingement of liquid droplets on a solid surface. See also erosion.
drop-through
An undesirable sagging or surface irregularity, usually encountered when brazing or welding near the solidus of the base metal, caused by overheating with rapid diffusion or alloying between the filler metal and the base metal.
dross
(1) The scum that forms on the surface of molten metal largely because of oxidation but sometimes because of the rising of impurities to the surface. (2) Oxide and other contaminants that form on the surface of molten solder.
dry corrosion
See gaseous corrosion.
dry cyaniding (obsolete)
Same as carbonitriding.
dry sand mold
A casting mold made of sand and then dried at 100 °C (212 °F) or above before being used. Contrast with green sand mold.
dry strength (casting)
The maximum strength of a molded sand specimen that has been thoroughly dried at 100 to 110 °C (220 to 230 °F) and cooled to room temperature. Also known as dry bond strength.
dual-phase steels
A class of high-strength low-alloy steels characterized by a tensile strength value of approximately 550 MPa (80 ksi) and by a microstructure consisting of about 20% hard martensite particles dispersed in a soft ductile ferrite matrix. The term dual phase refers to the predominance in the microstructure of two phases, ferrite and martensite. However, small amounts of other phases, such as bainite, pearlite, or retained austenite, may also be present.
ductile crack propagation
Slow crack propagation that is accompanied by noticeable plastic deformation and requires energy to be supplied from outside the body. Contrast with brittle crack propagation.
ductile fracture
Fracture characterized by tearing of metal accompanied by appreciable gross plastic deformation and expenditure of considerable energy. Contrast with brittle fracture.
ductile iron
A cast iron that has been treated while molten with an element such as magnesium or cerium to induce the formation of free graphite as nodules or spherulites, which imparts a measurable degree of ductility to the cast metal. Also known as nodular cast iron, spherulitic graphite cast iron, and spheroidal graphite (SG) iron.
ductility
The ability of a material to deform plastically without fracturing.
dummy block
In extrusion, a thick unattached disk placed between the ram and the billet to prevent overheating of the ram.
dummy cathode
(1) A cathode, usually corrugated to give variable current densities, that is plated at low current densities to preferentially remove impurities from a plating solution. (2) A substitute cathode that is used during adjustment of operating conditions.
duplex grain size
The simultaneous presence of two grain sizes in substantial amounts, with one grain size appreciably larger than the others. Also termed mixed grain size.
duplexing
Any two-furnace melting or refining process. Also called duplex melting or duplex processing.
duplex microstructure
A two-phase structure.
duplex stainless steels
Stainless steels having a fine-grained mixed microstructure of ferrite and austenite with a composition centered around 26Cr-6.5Ni.
duralumin (obsolete)
A term frequently applied to the class of age-hardenable aluminum-copper alloys containing manganese, magnesium, or silicon.
dusting
(1) A phenomenon, usually affecting carbon-base electrical motor brushes or other current-carrying contacts, wherein at low relative humidity or high applied current density, a powdery “dust” is produced during operation. (2) Applying a powder, such as sulfur to molten magnesium or graphite to a mold surface.
dynamic
Moving, or having high velocity. Frequently used with high strain rate (>0.1 s-1) testing of metal specimens.
dynamic creep
Creep that occurs under conditions of fluctuating load or fluctuating temperature.