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(1) Before finishing to final dimensions, repeatedly heating a ferrous or nonferrous part to or slightly above its normal operating temperature and then cooling to room temperature to ensure dimensional stability in service. (2) Transforming retained austenite in quenched hardenable steels, usually by cold treatment. (3) Heating a solution-treated stabilized grade of austenitic stainless steel to 870 to 900 °C (1600 to 1650 °F) to precipitate all carbon as TiC, NbC, or TaC so that sensitization is avoided on subsequent exposure to elevated temperature.
Thermal cutting of stacked metal plates arranged so that all the plates are severed by a single cut.
A foundry practice that makes use of both faces of a mold section, one face acting as the drag and the other as the cope. Sections, when assembled to other similar sections, form several tiers of mold cavities, all castings being poured together through a common sprue.
Milling cutters with alternate flutes of oppositely directed helixes.
Any of several steels containing at least 10.5% Cr as the principal alloying element; they usually exhibit passivity in aqueous environments.
Fastening two parts together permanently by recessing one part within the other and then causing plastic flow at the joint.
The general term used to denote all sheet metal pressworking. It includes blanking, shearing, hot or cold forming, drawing, bending, or coining.
A piece of rolling mill equipment containing one set of work rolls. In the usual sense, any pass of a cold- or hot-rolling mill. See also rolling mills.
standard electrode potential
The reversible potential for an electrode process when all products and reactions are at unit activity on a scale in which the potential for the standard hydrogen half-cell is zero.
A gold alloy containing 10% Cu; at one time used for legal coinage in the United States.
standard reference material
A reference material, the composition or properties of which are certified by a recognized standardizing agency or group.
A thin sheet of metal used as the cathode in electrolyte refining.
state of strain
A complete description of the deformation within a homogeneously deformed volume or at a point. The description requires, in general, the knowledge of the independent components of strain.
state of stress
A complete description of the stresses within a homogeneously stressed volume or at a point. The description requires, in general, the knowledge of the independent components of stress.
A term sometimes used to identify a form of hydrogen embrittlement in which a metal appears to fracture spontaneously under a steady stress less than the yield stress. There almost always is a delay between the application of stress (or exposure of the stressed metal to hydrogen) and the onset of cracking. More properly referred to as hydrogen-induced delayed cracking.
A hard structural constituent of cast iron that consists of a binary eutectic of ferrite, containing some phosphorus in solution, and iron phosphide (Fe3P). The eutectic consists of 10.2% P and 89.8% Fe. The melting temperature is 1050 °C (1920 °F).
A condition of brittleness that causes transcrystalline fracture in the coarse grain structure that results from prolonged annealing of thin sheets of low-carbon steel previously rolled at a temperature below about 705 °C (1300 °F). The fracture usually occurs at about 45° to the direction of rolling.
A type of drop hammer in which the ram is raised for each stroke by a double-action steam cylinder and the energy delivered to the workpiece is supplied by the velocity and weight of the ram and attached upper die driven downward by steam pressure. The energy delivered during each stroke can be varied.
The treatment of a sintered ferrous part in steam at temperatures between 510 and 595 °C (950 to 1100 °F) in order to produce a layer of black iron oxide (magnetite, or ferrous-ferric oxide, FeO·Fe2O3) on the exposed surface for the purpose of increasing hardness and wear resistance.
A cold reducing mill having two working rolls and two backup rolls, none of which is driven. The strip is drawn through the mill by a power reel in one direction as far as the strip will allow and then reversed by a second power reel, and so on until the desired thickness is attained.
An iron-base alloy, malleable in some temperature ranges as initially cast, containing manganese, usually carbon, and often other alloying elements. In carbon steel and low-alloy steel, the maximum carbon is about 2.0%; in high-alloy steel, about 2.5%. The dividing line between low-alloy and high-alloy steels is generally regarded as being at about 5% metallic alloying elements. Steel is said to be differentiated from two general classes of “irons”: the cast irons, on the high-carbon side and the relatively pure irons such as ingot iron, carbonyl iron, and electrolytic iron, on the low-carbon side. In some steels containing extremely low carbon, the manganese content is the principal differentiating factor, steel usually containing at least 0.25% and ingot iron considerably less.
Aging of metals at two or more temperatures, by steps, without cooling to room temperature after each step. See also aging , and compare with interrupted aging and progressive aging.
A powder metallurgy compact with one (dual step) or more (multistep) abrupt cross-sectional changes, usually obtained by pressing with split punches, each section of which uses a different pressure and a different rate of compaction. See also split punch.
Cleavage fractures that initiate on many parallel cleavage planes.
A pair of micrographs (or fractographs) of the same area, but taken from different angles so that the two micrographs when properly mounted and viewed reveal the structures of the objects in their three-dimensional relationships.
A silver alloy containing at least 92.5% Ag, the remainder being unspecified but usually copper. Sterling silver is used for flat and hollow tableware and for various items of jewelry.
A shop term for covered electrode.
See preferred term shielded metal arc welding.
Arc-shaped coil breaks, usually located near the center of sheet or strip.
(1) The rate of stress with respect to strain; the greater the stress required to produce a given strain, the stiffer the material is said to be. (2) The ability of a material or shape to resist elastic deflection. For identical shapes, the stiffness is proportional to the modulus of elasticity. For a given material, the stiffness increases with increasing moment of inertia, which is computed from cross-sectional dimensions.
A general term used to refer to a supply of metal in any form or shape and also to an individual piece of metal that is formed, forged, or machined to make parts.
A material used on the surfaces adjacent to the joint to limit the spread of soldering or brazing filler metal. See also resist.
A device in a bottom-pour ladle for controlling the flow of metal through the nozzle into a mold. The stopper rod consists of a steel rod, protective refractory sleeves, and a graphite stopper head.
(1) Applying a resist. (2) Depositing a metal (copper, for example) in localized areas to prevent carburization, decarburization, or nitriding in those areas. (3) Filling in a portion of a mold cavity to keep out molten metal.
Face milling a workpiece on both sides at once using two cutters spaced as required.
(1) Any bending, twisting, or stretching operation to correct any deviation from straightness in bars, tubes, or similar long parts or shapes. This deviation can be expressed as either camber (deviation from a straight line) or as total indicator reading (TIR) per unit of length. (2) A finishing operation for correcting misalignment in a forging or between various sections of a forging. See also roll straightening.
See preferred term direct current electrode negative (DCEN).
The unit of change in the size or shape of a body due to force. Also known as nominal strain. The term is also used in a broader sense to denote a dimensionless number that characterizes the change in dimensions of an object during a deformation or flow process. See also engineering strain and true strain.
A loss in ductility accompanied by an increase in hardness and strength that occurs when low-carbon steel (especially rimmed or capped steel) is aged following plastic deformation. The degree of embrittlement is a function of aging time and temperature, occurring in a matter of minutes at about 200 °C (400 °F), but requiring a few hours to a year at room temperature.
(1) Aging following plastic deformation. (2) The changes in ductility, hardness, yield point, and tensile strength that occur when a metal or alloy that has been cold worked is stored for some time. In steel, strain aging is characterized by a loss of ductility and a corresponding increase in hardness, yield point, and tensile strength.
The potential energy stored in a body by virtue of elastic deformation, equal to the work that must be done to produce this deformation.
An increase in hardness and strength of metals caused by plastic deformation at temperatures below the recrystallization range. Also known as work hardening.
See strain-hardening exponent.
The value of n in the relationship: = K n where is the true stress, is the true strain, and K, which is called the strength coefficient, is equal to the true stress at a true strain of 1.0. The strain-hardening exponent, also called “n-value,” is equal to the slope of the true stress/true strain curve up to maximum load, when plotted on log-log coordinates. The n-value relates to the ability of as sheet metal to be stretched in metalworking operations. The higher the n-value, the better the formability (stretchability).
The time rate of straining for the usual tensile test. Strain as measured directly on the specimen gage length is used for determining strain rate. Because strain is dimensionless, the units of strain rate are reciprocal time.
strain-rate sensitivity (m-value)
The increase in stress () needed to cause a certain increase in plastic strain rate () at a given level of plastic strain () and a given temperature (T):
(1) Rods sometimes used on gapframe metalforming presses to lessen the frame deflection. (2) Rods used to measure elastic strain and thus stresses, in frames of metalforming presses.
See state of strain.
A generic term describing continuous casting of one or more elongated shapes such as billets, blooms, or slabs; if two or more shapes are cast simultaneously, they are often of identical cross section.
A composite filler metal electrode consisting of stranded wires that may mechanically enclose materials to improve properties, stabilize the arc, or provide shielding.
(1) Current flowing through paths other than the intended circuit. (2) Current flowing in electrodeposition by way o an unplanned and undesired bipolar electrode that may be the tank itself or a poorly connected electrode.
Corrosion resulting from direct current flow through paths other than the intended circuit. For example, by an extraneous current in the earth.
The intensity of the internally distributed forces or components of forces that resist a change in the volume or shape of a material that is or has been subjected to external forces. Stress is expressed in force per unit area. Stress can be normal (tension or compression) or shear. See also compressive stress , engineering stress , mean stress , nominal stress , normal stress , residual stress , shear stress , tensile stress , and true stress.
One-half the algebraic difference between the maximum and minimum stresses in one cycle of a repetitively varying stress.
On a macromechanical level, the magnification of the level of an applied stress in the region of a notch, void, hole, or inclusion.
stress concentration factor (Kt)
A multiplying factor for applied stress that allows for the presence of a structural discontinuity such as a notch or hole; Kt equals the ratio of the greatest stress in the region of the discontinuity to the nominal stress for the entire section. Also called theoretical stress concentration factor.
Preferential attack of areas under stress in a corrosive environment, where such an environment alone would not have caused corrosion.
stress-corrosion cracking (SCC)
A cracking process that requires the simultaneous action of a corrodent and sustained tensile stress. This excludes corrosion-reduced sections that fail by fast fracture. It also excludes intercrystalline or transcrystalline corrosion, which can disintegrate an alloy without applied or residual stress. Stress-corrosion cracking may occur in combination with hydrogen embrittlement.
A scaling factor, usually denoted by the symbol K, used in linear-elastic fracture mechanics to describe the intensification of applied stress at the tip of a crack of known size and shape. At the onset of rapid crack propagation in any structure containing a crack, the factor is called the critical stress-intensity factor, or the fracture toughness. Various subscripts are used to denote different loading conditions or fracture toughnesses:
Kc Plane-stress fracture toughness. The value of stress intensity at which crack propagation becomes rapid in sections thinner than those in which plane-strain conditions prevail.
KI Stress-intensity factor for a loading condition that displaces the crack faces in a direction normal to the crack plane (also known as the opening mode of deformation).
KIc Plane-strain fracture toughness. The minimum value of Kc for any given material and condition
KId Dynamic fracture toughness. The fracture toughness determined under dynamic loading conditions; it is used as an approximation of KIc for very tough materials.
KIscc Threshold stress-intensity factor for stress-corrosion cracking. The critical plane-strain stress intensity at the onset of stress-corrosion cracking under specified conditions.
KQ Provisional value for plane-strain fracture toughness.
Kth Threshold stress intensity for stress-corrosion cracking. The critical stress intensity at the onset of stress-corrosion cracking under specified conditions.
K The range of the stress-intensity factor during a fatigue cycle. See also fatigue crack growth rate.
stress-intensity factor range (K)
In fatigue, the variation in the stress-intensity factor in a cycle, that is, Kmax – Kmin. See also fatigue crack growth rate.
Design features (such as sharp corners) or mechanical defects (such as notches) that act to intensify the stress at these locations.
See range of stress.
stress ratio (A or R)
The algebraic ratio of two specified stress values in a stress cycle. Two commonly used stress ratios are: (1) the ratio of the alternating stress amplitude to the mean stress, A = Sa/Sm; and (2) the ratio of the minimum stress to the maximum stress, R = Smin/Smax.
The time-dependent decrease in stress in a solid under constant constraint at constant temperature.
A plot of the remaining or relaxed stress as a function of time. The relaxed stress equals the initial stress minus the remaining stress. Also known as stress-time curve.
Cracking in the heat-affected zone or weld metal that occurs during the exposure of weldments to elevated temperatures during postweld heat treatment, in order to reduce residual stresses and improve toughness, or high-temperature service.
stress-relief heat treatment
Uniform heating of a structure or a portion thereof to a sufficient temperature to relieve the major portion of the residual stresses, followed by uniform cooling.
Heating to a suitable temperature, holding long enough to reduce residual stresses, and then cooling slowly enough to minimize the development of new residual stresses.
See creep-rupture strength.
See creep-rupture test.
See state of stress.
A graph in which corresponding values of stress and strain from a tension, compression, or torsion test are plotted against each other. Values of stress are usually plotted vertically (ordinates or y-axis) and values of strain horizontally (abscissas or x-axis). Also known as deformation curve and stress-strain diagram.
The leveling of a piece of sheet metal (that is, removing warp and distortion) by gripping it at both ends and subjecting it to a stress higher than its yield strength.
A process for straightening rod, tubing, and shapes by the application of tension at the ends of the stock. The products are elongated a definite amount to remove warpage.
Elongated markings that appear on the surface of some sheet materials when deformed just past the yield point. These markings lie approximately parallel to the direction of maximum shear stress and are the result of localized yielding. See also Lüders lines.
(1) A machine used to perform stretch forming operations. (2) A device adaptable to a conventional press for accomplishing stretch forming.
The shaping of a metal sheet or part, usually of uniform cross section, by first applying suitable tension or stretch and then wrapping it around a die of the desired shape.
The extension of the surface of a metal sheet in all directions. In stretching, the flange of the flat blank is securely clamped. Deformation is restricted to the area initially within the die. The stretching limit is the onset of metal failure.
A fatigue fracture feature, often observed in electron micrographs, that indicates the position of the crack front after each succeeding cycle of stress. The distance between striations indicates the advance of the crack front across that crystal during one stress cycle, and a line normal to the striations indicates the direction of local crack propagation. See also beach marks.
(1) A thin electrodeposited film of metal to be overlaid with other plated coatings. (2) A plating solution of high covering power and low efficiency designed to electroplate a thin, adherent film of metal.
Electrodepositing, under special conditions, a very thin film of metal that will facilitate further plating with another metal or with the same metal under different conditions.
Those areas on the faces of a set of metalforming dies that are designed to meet when the upper die and lower die are brought together. The striking surface helps protect impressions from impact shock and aids in maintaining longer die life.
In wrought materials, an elongated configuration of microconstituents or foreign material aligned in the direction of working. The term is commonly associated with elongated oxide or sulfide inclusions in steel.
A continuous weld bead made without appreciable transverse oscillation (weaving motion). Contrast with weave bead.
(1) A flat-rolled metal product of some maximum thickness and width arbitrarily dependent on the type of metal; narrower than sheet. (2) A roll-compacted metal powder product. See also roll compacting. (3) Removal of a powder metallurgy compact from the die. An alternative to ejecting or knockout.
A plate designed to remove, or strip, sheet metal stock from the punching members during the withdrawal cycle. Strippers are also used to guide small precision punches in close-tolerance dies to guide scrap away from dies and to assist in the cutting action. Strippers are made in two types: fixed and movable.
A punch that serves as the top or bottom of a metalforming die cavity and later moves farther into the die to eject the part or compact. See also ejector rod and knockout(3).
(1) Removing a coating from a metal surface. (2) Removing a foundry pattern from the mold or the core box from the core.
A piece of metal of any of several designs accepted as standard by the structural branch of the iron and steel industries.
As applied to a crystal, the shape and size of the unit cell and the location of all atoms within the unit cell. As applied to microstructure, the size, shape, and arrangement of phases. See also unit cell.
stud arc welding
An arc welding process that produces coalescence of metals by heating them with an arc between a metal stud, or similar part, and the other workpiece. When the surfaces to be joined are properly heated, they are brought together under pressure. Partial shielding may be obtained by the use of a ceramic ferrule surrounding the stud. Shielding gas or flux may or may not be used.
A general term for joining a metal stud or similar part to a workpiece. Welding may be accommodated by arc, resistance, friction, or other processes with or without external gas shielding.
An expendable pattern of foamed plastic, especially expanded polystyrene, used in manufacturing castings by the lost foam process. See also lost foam casting.
subboundary structure (subgrain structure)
A network or low-angle boundaries, usually with misorientations less that 1° within the main grains of a microstructure.
An annealing treatment in which a steel is heated to a temperature below the A1 temperature, then cooled slowly to room temperature. See also transformation temperature.
A portion of a crystal or grain, with an orientation slightly different from the orientation of neighboring portions of the same crystal.
submerged arc welding (SAW)
An arc welding process that produces coalescence of metals by heating them with an arc or arcs between a bare metal electrode or electrodes and the workpieces. The arc and molten metal are shielded by a blanket of granular, fusible material on the workpieces. Pressure is not used, and filler metal is obtained from the electrode and sometimes from a supplemental source (welding rod, flux, or metal granules).
A furnace used for liquid carburizing of parts by heating molten salt baths with the use of electrodes submerged in the ceramic lining. See also immersed-electrode furnace.
Particles that will pass through a 44 m (325 mesh) screen.
See preferred term subsieve fraction.
An alloying element with an atomic size and other features similar to the solvent that can replace or substitute for the solvent atoms in the lattice and form a significant region of solid solution in the phase diagram.
substitutional solid solution
A solid solution in which the solvent and solute atoms are located randomly at the atom sites in the crystal structure of the solution. See also interstitial solid solution.
The material, workpiece, or substance on which the coating is deposited.
Same as subboundary structure.
Formation of isolated particles of corrosion products beneath a metal surface. This results from the preferential reactions of certain alloy constituents to inward diffusion of oxygen, nitrogen, or sulfur.
The reaction of a metal or alloy with a sulfur-containing species to produce a sulfur compound that forms on or beneath the surface on the metal or alloy.
sulfide stress cracking (SSC)
Brittle fracture by cracking under the combined action of tensile stress and corrosion in the presence of water and hydrogen sulfide. See also environmental cracking.
An inverted container, holding a high concentration of sulfur dioxide gas, used in die casting to cover a pot of molten magnesium to prevent burning.
A macrographic method of examining for distribution of sulfide inclusions by placing a sheet of wet acidified photographic paper in contact with the polished sheet surface to be examined.
Synthetically produced diamond and cubic boron nitride (CBN) used in a wide variety of cutting and grinding applications.
Heat-resistant alloys based on nickel, iron-nickel, or cobalt that exhibit high strength and resistance to surface degradation at elevated temperatures.
A property of many metals, alloys, compounds, oxides, and organic materials at temperatures near absolute zero by virtue of which their electrical resistivity vanishes and they become strongly diamagnetic.
Cooling of a substance below the temperature at which a change of state would ordinarily take place without such a change of state occurring, for example, the cooling of a liquid below its freezing point without freezing taking place; this results in a metastable state.
superficial hardness test
See Rockwell superficial hardness test.
The portion of a metal powder that is composed of particles smaller than a specified size, usually 10 m.
A low-velocity abrading process very similar to honing; however, unlike honing, superfinishing processes focus primarily on the improvement of surface finish and much less on correction of geometric errors (dimensional accuracy). Also known as microhoning.
(1) Heating of a substance above the temperature at which a change of state would ordinarily take place without a change of state occurring, for example, the heating of a liquid above its boiling point without boiling taking place; this results in a metastable state. (2) Any increment of temperature above the melting point of a metal; sometimes construed to be any increment of temperature above normal casting temperatures introduced for the purpose of refining, alloying, or improving fluidity.
See ordered structure.
superplastic forming (SPF)
A strain rate sensitive sheet metal forming process that uses characteristics of materials exhibiting high tensile elongation. During superplastic forming, gas pressure is imposed on a superplastic sheet, causing the material to form into the die configuration. See also superplasticity.
The ability of certain metals (most notably aluminum- and titanium-base alloys) to develop extremely high tensile elongations at elevated temperatures and under controlled rates of deformation.
A metastable solution in which the dissolved material exceeds the amount the solvent can hold in normal equilibrium at the temperature and other conditions that prevail.
Rods or pins of precise length used to support the overhang of irregularly shaped punches in metal forming presses.
A plate that supports a draw ring or draw plate in a sheet metal forming press. It also serves as a spacer. See also draw plate and draw ring.
Irregularities or changes on the surface of a material due to machining or grinding operations. The types of surface alterations associated with metal removal practices include mechanical (for example, plastic deformation, hardness variations, cracks, etc.), metallurgical (for example, phase transformations, twinning, recrystallization, and untempered or overtempered martensite), chemical (for example, intergranular attack, embrittlement, and pitting), thermal (heat-affected zone, recast, or redeposited metal, and resolidified material), and electrical surface alterations (conductivity change or resistive heating).
Same as checks.
In tribology, damage to a solid surface resulting from mechanical contact with another substance, surface, or surfaces moving relatively to it and involving the displacement or removal of material. In certain contexts, wear is a form of surface damage in which material is progressively removed. In another context, surface damage involves a deterioration of function of a solid surface even though there is no material loss from that surface. Surface damage may therefore precede wear.
(1) The geometric irregularities in the surface of a solid material. Measurement of surface finish shall not include inherent structural irregularities unless these are the characteristics being measured. (2) Condition of a surface as a result of a final treatment. See also roughness.
Producing a plane surface by grinding.
A generic term covering several processes applicable to a suitable ferrous alloy that produces, by quench hardening only, a surface layer that is harder or more wear resistant than the core. There is no significant alteration of the chemical composition of the surface layer. The processes commonly used are carbonitriding, carburizing, induction hardening, flame hardening, nitriding, and nitrocarburizing. Use of the applicable specific process name is preferred.
The alteration of surface composition or structure by the use of energy or particle beams. Two types of surface modification methods commonly employed are ion implantation and laser surface processing.
Fine irregularities in the surface texture of a material, usually including those resulting from the inherent action of the production process. Surface roughness is usually reported as the arithmetic roughness average, Ra, and is given in micrometers or microinches.
The roughness, waviness, lay, and flaws associated with a surface. See also lay.
The deposition of filler metal (material) on a base metal (substrate) to obtain desired properties or dimensions, as opposed to making a joint. See also buildup , buttering , cladding , coating , and hardfacing.
A type of weld composed of one or more stringer or weave beads deposited on an unbroken surface to obtain desired properties or dimensions.
(1) The operation of reducing or changing the cross-sectional area of stock by the fast impact of revolving dies. (2) The tapering of bar, rod, wire, or tubing by forging, hammering, or squeezing; reducing a section by progressively tapering lengthwise until the entire section attains the smaller dimension of the taper.
Tapering bar, rod, wire, or tubing by forging, hammering, or squeezing; reducing a section by progressively tapering lengthwise until the entire section attains the smaller dimension of the taper. See also rotary swaging.
Intimate mixture of grinding chips and fine particles of abrasive and bond resulting from a grinding operation.
A soldering process variation in which two or more parts that have been precoated with solder are reheated and assembled into a joint without the use of additional solder.
A type of foundry pattern that is a template cut to the profile of the desired mold shape that, when revolved around a stake or spindle, produces that shape in the mold.
Swift cup test
A simulative test for determining formability of sheet metal in which circular blanks of various diameters are clamped in a die ring and deep drawn into a cup by a flat-bottomed cylindrical punch. The ratio of the largest blank diameter that can be drawn successfully to the cup diameter is known as the limiting drawing ratio (LDR) or deformation limit.
swing forging machine
Equipment for continuously hot reducing ingots, blooms, or billets to square flats, rounds, or rectangles by the crank-driven oscillating action of paired dies.
swing frame grinder
A grinding machine suspended by a chain at the center point so that it may be turned and swung in any direction for grinding of billets, large castings, or other heavy work. Principal use is removing surface imperfections and roughness.
synthetic cold-rolled sheet
A hot-rolled pickled sheet given a sufficient final temper pass to impart a surface approximating that of cold-rolled steel.