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The plane or system of planes of a crystalline phase along which some phenomenon, such as twinning or transformation, occurs.
See austenitic manganese steel.
An electrode immersed in a suitable electrolyte, designed for measurements of electrode potential.
A temper of nonferrous alloys and some ferrous alloys characterized by tensile strength about midway between those of dead soft and full hard tempers.
A commercial process for winning aluminum from alumina by electrolytic reduction of a fused bath of alumina dissolved in cryolite.
A machine that applies a sharp blow to the work area through the fall of a ram onto an anvil. The ram can be driven by gravity or power. See also gravity hammer.
Forging in which the work is deformed by repeated blows.
The working of metal sheet into a desired shape over a form or on a high-speed hammer and a similar anvil to produce the required dishing or thinning.
Forge welding by hammering.
A small manual folding machine designed to bend sheet metal, similar in design and purpose to a press brake.
hand forge (smith forge)
A forging operation in which forming is accomplished on dies that are generally flat. The piece is shaped roughly to the required contour with little or no lateral confinement; operations involving mandrels are included. The term hand forge refers to the operation performed, while hand forging applies to the part produced.
Irregular breaks caused by improper handling of metal sheets during processing. These breaks result from bending or sagging of the sheets during handling.
Chromium electrodeposited for engineering purposes (such as to increase the wear resistance of sliding metal surfaces) rather than as a decorative coating. It is usually applied directly to substrate and is customarily thicker (>1.2 m, or 0.05 mil) than a decorative deposit, but not necessarily harder.
An imprecise term applied to drawn products, such as wire and tubing, that indicates substantial cold reduction without subsequent annealing. Compare with light drawn.
The relative ability of a ferrous alloy to form martensite when quenched from a temperature above the upper critical temperature. Hardenability is commonly measured as the distance below a quenched surface at which the metal exhibits a specific hardness (50 HRC, for example) or a specific percentage of martensite in the microstructure.
An alloy rich in one or more alloying elements that is added to a melt to permit closer control of composition than is possible by the addition of pure metals, or to introduce refractory elements not readily alloyed with the base metal. Sometimes called master alloy or rich alloy.
Increasing hardness of metals by suitable treatment, usually involving heating and cooling. When applicable, the following, more specific terms should be used: age hardening , case hardening , flame hardening , induction hardening , precipitation hardening , and quench hardening.
The application of a hard, wear-resistant material to the surface of a component by welding, spraying, or allied welding processes to reduce wear or loss of material by abrasion, impact, erosion, galling, and cavitation. See also surfacing.
Wear-resistant materials available as bare welding rod, flux-coated rod, long-length solid wires, long-length tubular wires, or powders that are deposited by hardfacing.
A collective term that designates a sintered material with high hardness, strength, and wear resistance and is characterized by a tough metallic binder phase and particles of carbides, borides, or nitrides of the refractory metals. The term is in general use abroad, while for the carbides the term cemented carbide is preferred in the U.S., and the boride and nitride materials are usually categorized as cermets.
A measure of the resistance of a material to surface indentation or abrasion; may be thought of as a function of the stress required to produce some specified type of surface deformation. There is no absolute scale for hardness; therefore, to express hardness quantitatively, each type of test has its own scale of arbitrarily defined hardness. Indentation hardness can be measured by Brinell, Rockwell, Vickers, Knoop, and Scleroscope hardness tests.
A term erroneously used to denote silver-base brazing filler metals.
See preferred terms surfacing or hardfacing.
Same as full hard temper.
A four-electrode cell for measurement of electrolyte resistance and electrode polarization during electrolysis.
Carbon, carbon-boron, or alloy steel produced to specified limits of hardenability; the chemical composition range may be slightly different from that of the corresponding grade of ordinary carbon or alloy steel.
The upsetting of wire, rod, or bar stock in dies to form parts that usually contain portions that are greater in cross-sectional area than the original wire, rod, or bar.
The bottom portions of certain furnaces, such as blast furnaces, air furnaces, and other reverberatory furnaces, that support the charge and sometimes collect and hold molten metal.
A stated tonnage of metal obtained from a period of continuous melting in a cupola or furnace, or the melting period required to handle this tonnage.
heat-affected zone (HAZ)
That portion of the base metal that was not melted during brazing, cutting, or welding, but whose microstructure and mechanical properties were altered by the heat.
A pattern of parallel surface cracks that are formed by alternate rapid heating and cooling of the extreme surface metal, sometimes found on forging dies and piercing punches. There may be two sets of parallel cracks, one set perpendicular to the other.
An alloy developed for very-high-temperature service where relatively high stresses (tensile, thermal, vibratory, or shock) are encountered and where oxidation resistance is frequently required.
A material that absorbs or transfers heat away from a critical element or part.
Coloration of a metal surface through oxidation by heating to reveal details of the microstructure.
heat treatable alloy
An alloy that can be hardened by heat treatment.
heat treating film
A thin coating or film, usually an oxide, formed on the surface of a metal during heat treatment.
Heating and cooling a solid metal or alloy in such a way as to obtain desired conditions or properties. Heating for the sole purpose of hot working is excluded from the meaning of this definition.
A sintered tungsten alloy with nickel, copper, and/or iron, the tungsten content being at least 90 wt% and the density being at least 16.8 g/cm3.
Synonymous with base.
A block or plate usually mounted on or attached to a lower die in a forming or forging press that serves to prevent or minimize the deflection of punches or cams.
A bend of 180° made in two steps. First, a sharp-angle bend is made; next the bend is closed using a flat punch and a die.
A common abbreviation for high-energy-rate forging or high-energy-rate forming.
Same as chevron pattern.
Copper that, in the annealed condition, has a minimum electrical conductivity of 100% IACS as determined by ASTM test methods.
Fatigue that occurs at relatively large numbers of cycles. The arbitrary, but commonly accepted, dividing line between high-cycle fatigue and low-cycle fatigue is considered to be about 104 to 105 cycles. In practice, this distinction is made by determining whether the dominant component of the strain imposed during cyclic loading is elastic (high cycle) or plastic (low cycle), which in turn depends on the properties of the metal and on the magnitude of the nominal stress.
high-energy-rate forging (HERF)
A closed-die hot- or cold-forging process in which the stored energy of high-pressure gas is used to accelerate a ram to unusually high velocities in order to effect deformation of the workpiece. Ideally, the final configuration of the forging is developed in one blow or, at most, a few blows. In high-energy-rate forging, the velocity of the ram, rather than its mass, generates the major forging force. Also known as HERF processing, high-velocity forging, and high-speed forging.
A group of forming processes that applies a high rate of strain to the material being formed through the application of high rates of energy transfer. See also explosive forming , high-energy-rate forging , and electromagnetic forming.
high frequency resistance welding
A group of resistance welding process variations that uses high frequency welding current to concentrate the welding heat at the desired location.
Buffing or polishing selected areas of a complex shape to increase the luster or change the color of those areas.
high residual phosphorus copper
Deoxidized copper with residual phosphorus present in amounts (usually 0.013 to 0.04%) generally sufficient to decrease appreciably the conductivity of the copper.
High-productivity machining processes that achieve cutting speeds in excess of 600 m/min (2000 sfm) and up to 18,000 m/min (60,000 sfm).
high-strength low-alloy (HSLA) steels
Steels designed to provide better mechanical properties and/or greater resistance to atmospheric corrosion than conventional carbon steels. They are not considered to be alloy steels in the normal sense because they are designed to meet specific mechanical properties rather than a chemical composition (HSLA steels have yield strengths greater than 275 MPa, or 40 ksi). The chemical composition of a specific HSLA steel may vary for different product thicknesses to meet mechanical property requirements. The HSLA steels have low carbon contents (0.05 to 0.25% C) in order to produce adequate formability and weldability, and they have manganese contents up to 2.0%. Small quantities of chromium, nickel, molybdenum, copper, nitrogen, vanadium, niobium, titanium, and zirconium are used in various combinations.
high-temperature hydrogen attack
A loss of strength and ductility of steel by high-temperature reaction of absorbed hydrogen with carbides in the steel resulting in decarburization and internal fissuring.
Contraction where the shape will not permit a metal casting to contract in certain regions in keeping with the coefficient of expansion.
See hot isostatic pressing.
A rotary cutting tool with its teeth arranged along a helical thread, used for generating gear teeth or other evenly spaced forms on the periphery of a cylindrical workpiece. The hob and the workpiece are rotated in timed relationship to each other while the hob is fed axially or tangentially across or radially into the workpiece. Hobs should not be confused with multiple-thread milling cutters, rack cutters, and similar tools, where the teeth are not arranged along a helical thread.
Machining a part from bar stock, plate, or a simple forging in which much of the original stock is removed.
holddown plate (pressure pad)
A pressurized plate designed to hold the workpiece down during a press operation. In practice, this plate often serves as a stripper and is also called a stripper plate.
In heat treating of metals, that portion of the thermal cycle during which the temperature of the object is maintained constant.
A furnace into which molten metal can be transferred to be held at the proper temperature until it can be used to make castings.
In heat treating of metals, the constant temperature at which the object is maintained.
Time for which the temperature of the heat treated metal object is maintained constant.
hole expansion test
A simulative test in which a flat metal sheet specimen with a circular hole in its center is clamped between annular die plates and deformed by a punch, which expands and ultimately cracks the edge of the hole.
The forming of an integral collar around the periphery of a previously formed hole in a sheet metal part.
Discontinuities in a coating (such as porosity, cracks, gaps, and similar flaws) that allow areas of substrate to be exposed to any corrosive environment that contacts the coated surface.
Use of a carburizing process to convert a low-carbon ferrous alloy to one of uniform and higher carbon content throughout the section.
A heat treating practice whereby a metal object is held at high temperature to eliminate or decrease chemical segregation by diffusion.
A low-speed finishing process used chiefly to produce uniform high dimensional accuracy and fine finish, most often on inside cylindrical surfaces. In honing, very thin layers of stock are removed by simultaneously rotating and reciprocating a bonded abrasive stone or stick that is pressed against the surface being honed with lighter force than is typical of grinding.
A generalization applicable to all solid material, which states that stress is directly proportional to strain and is expressed as: where E is the modulus of elasticity or Young’s modulus. The constant relationship between stress and strain applies only below the proportional limit. See also modulus of elasticity.
An electrolytic refining process for aluminum, using three liquid layers in the reduction cell.
(1) In a resistance welding machine, a cylindrical arm or beam that transmits the electrode pressure and usually conducts the welding current. (2) A cone-shaped member that transmits ultrasonic energy from a transducer to a welding or machining tool. See also ultrasonic impact grinding and ultrasonic welding.
A mechanical metal forming press equipped with or arranged for a cantilever block or horn that acts as the die or support for the die, used in forming, piercing, setting down, or riveting hollow cylinders and odd-shaped work.
The distance between adjacent surfaces of the horns of a resistance welding machine.
hot box process
In foundry practice, resin-base (furan or phenolic) binder process for molding sands similar to shell coremaking; cores produced with it are solid unless mandrelled out.
hot chamber machine
A die casting machine in which the metal chamber under pressure is immersed in the molten metal in a furnace. The chamber is sometimes called a gooseneck, and the machine is sometimes called a gooseneck machine.
(1) A high-temperature thermomechanical treatment consisting of deforming a metal above its transformation temperature and cooling fast enough to preserve some or all of the deformed structure. (2) A general term synonymous with warm working.
An accelerated corrosion of metal surfaces that results from the combined effect of oxidation and reactions with sulfur compounds and other contaminants, such as chlorides, to form a molten salt on a metal surface that fluxes, destroys, or disrupts the normal protective oxide. See also gaseous corrosion.
A crack that develops in a weldment or casting during solidification.
A hot forging process in which both the dies and the forging stock are heated; typical die temperatures are 110 to 225 °C (200 to 400 °F) lower than the temperature of the stock. Compare with isothermal forging.
Covering a surface by dipping the surface to be coated into a molten bath of the coating material. See also hot dip coating.
hot dip coating
A metallic coating obtained by dipping the substrate into a molten metal.
A process whereby a heated billet is forced to flow through a shaped die opening. The temperature at which extrusion is performed depends on the material being extruded. Hot extrusion is used to produce long, straight metal products of constant cross section, such as bars, solid and hollow sections, tubes, wires, and strips, from materials that cannot be formed by cold extrusion.
(1) A forging process in which the die and/or forging stock are heated. See also hot-die forging and isothermal forging. (2) The plastic deformation of a pressed and/or sintered powder compact in at least two directions at temperatures above the recrystallization temperature.
See hot working.
hot isostatic pressing
(1) A process for simultaneously heating and forming a compact in which the powder is contained in a sealed flexible sheet metal or glass enclosure and the so-contained powder is subjected to equal pressure from all directions at a temperature high enough to permit plastic deformation and sintering to take place. (2) A process that subjects a component (casting, powder forgings, etc.) to both elevated temperature and isostatic gas pressure in an autoclave. The most widely used pressurizing gas is argon. When castings are hot isostatically pressed, the simultaneous application of heat and pressure virtually eliminates internal voids and microporosity through a combination of plastic deformation, creep, and diffusion.
A production line or facility for hot rolling of metals.
hot press forging
Plastically deforming metals between dies in presses at temperatures high enough to avoid strain hardening.
Simultaneous heating and forming of a powder compact. See also pressure sintering.
hot pressure welding
A solid-state welding process that produces coalescence of materials with heat and application of pressure sufficient to produce macrodeformation of the base material. Vacuum or other shielding media may be used. See also diffusion welding and forge welding. Compare with cold welding.
An imprecise term for various quenching procedures in which a quenching medium is maintained at a prescribed temperature above 70 °C (160 °F).
A tendency for some alloys to separate along grain boundaries when stressed or deformed at temperatures near the melting point. Hot shortness is caused by a low-melting constituent, often present only in minute amounts, that is segregated at grain boundaries.
A fracture formed in a metal during solidification because of hindered contraction.
(1) A reservoir, thermally insulated or heated, that holds molten metal on top of a mold for feeding of the ingot or casting as it contracts on solidifying, thus preventing formation of pipe or voids. (2) A refractory-lined steel or iron casting that is inserted into the tip of the mold and is supported at various heights to feed the ingot as it solidifies.
The removal of flash or excess metal from a hot part (such as a forging) in a trimming press.
hot upset forging
A bulk forming process for enlarging and reshaping some of the cross-sectional area of a bar, tube, or other product form of uniform (usually round) section. It is accomplished by holding the heated forging stock between grooved dies and applying pressure to the end of the stock, in the direction of its axis, by the use of a heading tool, which spreads (upsets) the end by metal displacement. Also called hot heading or hot upsetting. See also heading and upsetting.
The structure of a material worked at a temperature higher than the recrystallization temperature.
(1) The plastic deformation of metal at such a temperature and strain rate that recrystallization takes place simultaneously with the deformation, thus avoiding any strain hardening. Also referred to as hot forging and hot forming. (2) Controlled mechanical operations for shaping a product at temperatures above the recrystallization temperature. Contrast with cold working.
The production of forging die cavities by pressing a male master plug, known as a hub, into a block of metal.
A special electrodeposition cell giving a range of known current densities for test work.
A gravity-drop forging hammer that uses hydraulic pressure to lift the hammer between strokes.
hydraulic-mechanical press brake
A mechanical press brake that uses hydraulic cylinders attached to mechanical linkages to power the ram through its working stroke.
A press in which fluid pressure is used to actuate and control the ram. Hydraulic presses are used for both open- and closed-die forging.
Removal of material by the impingement of a high-velocity fluid against a workpiece. See also waterjet/abrasive waterjet machining.
hydrogen-assisted cracking (HAC)
See hydrogen embrittlement.
hydrogen-assisted stress-corrosion cracking (HSCC)
See hydrogen embrittlement.
The formation of blisters on or below a metal surface from excessive internal hydrogen pressure. Hydrogen may be formed during cleaning, plating, or corrosion.
A term sometimes used to denote brazing in a hydrogen-containing atmosphere, usually in a furnace; use of the appropriate process name is preferred.
A general term for the embrittlement, cracking, blistering, and hydride formation that can occur when hydrogen is present in some metals.
A process resulting in a decrease of the toughness or ductility of a metal due to the presence of atomic hydrogen. Hydrogen embrittlement has been recognized classically as being of two types. The first, known as internal hydrogen embrittlement, occurs when the hydrogen enters molten metal which becomes supersaturated with hydrogen immediately after solidification. The second type, environmental hydrogen embrittlement, results from hydrogen being absorbed by solid metals. This can occur during elevated-temperature thermal treatments and in service during electroplating, contact with maintenance chemicals, corrosion reactions, cathodic protection, and operating in high-pressure hydrogen. In the absence of residual stress or external loading, environmental hydrogen embrittlement is manifested in various forms, such as blistering, internal cracking, hydride formation, and reduced ductility. With a tensile stress or stress-intensity factor exceeding a specific threshold, the atomic hydrogen interacts with the metal to induce subcritical crack growth leading to fracture. In the absence of a corrosion reaction (polarized cathodically), the usual term used is hydrogen-assisted cracking (HAC) or hydrogen stress cracking (HSC). In the presence of active corrosion, usually as pits or crevices (polarized anodically), the cracking is generally called stress-corrosion cracking (SCC), but should more properly be called hydrogen-assisted stress-corrosion cracking (HSCC). Thus, HSC and electrochemically anodic SCC can operate separately or in combination (HSCC). In some metals, such as high-strength steels, the mechanism is believed to be all, or nearly all, HSC. The participating mechanism of HSC is not always recognized and may be evaluated under the generic heading of SCC.
hydrogen-induced cracking (HIC)
Same as hydrogen embrittlement.
hydrogen-induced delayed cracking
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 is usually a delay between the application of stress (or exposure of the stressed metal to hydrogen) and the onset of cracking. Also referred to as static fatigue.
The loss in weight of metal powder or a compact caused by heating a representative sample according to a specified procedure in a purified hydrogen atmosphere. Broadly, a measure of the oxygen content of the sample when applied to materials containing only such oxides as are reducible with hydrogen and no hydride-forming element.
In electroplating, overvoltage associated with the liberation of hydrogen gas.
hydrogen stress cracking (HSC)
See hydrogen embrittlement.
Industrial winning or refining of metals using water or an aqueous solution.
A method of extruding a billet through a die by pressurized fluid instead of the ram used in conventional extrusion.
A special case of isostatic pressing that uses a liquid such as water or oil as a pressure transducing medium and is therefore limited to near room-temperature operation.
Three equal and mutually perpendicular tensile stresses.
In an alloy system exhibiting a eutectic, any alloy whose composition has an excess of alloying element compared with the eutectic composition and whose equilibrium microstructure contains some eutectic structure.
In an alloy system exhibiting a eutectoid, any alloy whose composition has an excess of alloying element compared with the eutectoid composition, and whose equilibrium microstructure contains some eutectoid structure.
In an alloy system exhibiting a eutectic, any alloy whose composition has an excess of base metal compared with the eutectic composition and whose equilibrium microstructure contains some eutectic structure.
In an alloy system exhibiting a eutectoid, any alloy whose composition has an excess of base metal compared with the eutectoid composition and whose equilibrium microstructure contains some eutectoid structure.
The lag of the magnetization of a substance behind any cyclic variation of the applied magnetizing field.
The phenomenon of permanently absorbed or lost energy that occurs during any cycle of loading or unloading when a material is subjected to repeated loading.