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The relative ease of machining a metal.
A relative measure of the machinability of an engineering material under specified standard conditions. Also known as machinability rating.
Forging performed in upsetters or horizontal forging machines.
Welding with equipment that performs the welding operation under the constant observation and control of a welding operator. The equipment may or may not load and unload the workpiece. See also automatic welding.
Removing material from a metal part, usually using a cutting tool, and usually using a power-driven machine.
See finish allowance.
Irregularities or changes on the surface of a material due to machining or grinding operations that may deleteriously affect the performance of the material/part.
Residual stress caused by machining.
A graphic representation of the surface of a prepared specimen at a magnification not exceeding 25×. When photographed, the reproduction is known as a photomacrograph.
A term applied to such hardness testing procedures as the Rockwell or Brinell hardness tests to distinguish them from microindentation hardness tests such as the Knoop or Vickers tests.
Residual stress in a material in a distance comparable to the gage length of strain measurement devices (as opposed to stresses within very small, specific regions, such as individual grains). Compare with microscopic stress.
Isolated, clustered, or interconnected voids in a casting that are detectable macroscopically. Such voids are usually associated with abrupt changes in section size and are caused by feeding that is insufficient to compensate for solidification shrinkage.
The structure of metals as revealed by macroscopic examination of the etched surface of a polished specimen.
magnetically hard alloy
See permanent magnet material.
magnetically soft alloy
See soft magnetic material.
A nondestructive method of inspection to determine the existence of variations in magnetic flux in ferromagnetic materials of constant cross section, such as might be caused by discontinuities and variations in hardness. The variations are usually indicated by a change in pattern on an oscilloscope screen.
A nondestructive method of inspection for determining the existence and extent of surface cracks and similar imperfections in ferromagnetic materials. Finely divided magnetic particles, applied to the magnetized part, are attracted to and outline the pattern of any magnetic leakage fields created by discontinuities.
The area on a magnetized part at which the magnetic field leaves or enters the part. It is a point of maximum attraction in a magnet.
A device used to separate magnetic from less magnetic or nonmagnetic materials. The crushed material is conveyed on a belt past a magnet.
A force field, resulting from the flow of electric currents or from magnetized bodies, that produces magnetic induction.
Changes in dimensions of a body resulting from application of a magnetic field.
The characteristic of metals that permits plastic deformation in compression without fracture. See also ductility.
Annealing white iron in such a way that some or all of the combined carbon is transformed into graphite or, in some cases, so that part of the carbon is removed completely.
A cast iron made by prolonged annealing of white iron in which decarburization, graphitization, or both take place to eliminate some or all of the cementite. The graphite is in the form of temper carbon. If decarburization is the predominant reaction, the product will exhibit a light fracture surface; hence whiteheart malleable. Otherwise, the fracture surface will be dark; hence blackheart malleable. Only the blackheart malleable is produced in the United States. Ferritic malleable has a predominantly ferritic matrix; pearlitic malleable may contain pearlite, spheroidite, or tempered martensite, depending on heat treatment and desired hardness.
(1) A blunt-ended tool or rod used to retain the cavity in a hollow metal product during working. (2) A metal bar around which other metal may be cast, bent, formed, or shaped. (3) A shaft or bar for holding work to be machined. (4) A form, such as a mold or matrix, used as a cathode in electroforming.
The process of rolling or forging a hollow blank over a mandrel to produce a weldless, seamless ring or tube. See also radial forging.
A process for piercing tube billets in making seamless tubing. The billet is rotated between two heavy rolls mounted at an angle and is forced over a fixed mandrel.
A welding operation performed and controlled completely by hand. See also automatic welding , machine welding , and semiautomatic welding.
A precipitation-hardening treatment applied to a special group of high-nickel iron-base alloys (maraging steels) to precipitate one or more intermetallic compounds in a matrix of essentially carbon-free martensite.
A rubber-pad forming process developed to form wrinkle-free shrink flanges and deep-drawn shells. It differs from the Guerin process in that the sheet metal blank is clamped between the rubber pad and the blankholder before forming begins.
(1) A hardening procedure in which an austenitized ferrous material is quenched into an appropriate medium at a temperature just above the martensite start temperature of the material, held in the medium until the temperature is uniform throughout, although not long enough for bainite to form, then cooled in air. The treatment is frequently followed by tempering. (2) When the process is applied to carburized material, the controlling martensite start temperature is that of the case. This variation of the process is frequently called marquenching.
A generic term for microstructures formed by diffusionless phase transformation in which the parent and product phases have a specific crystallographic relationship. Martensite is characterized by an acicular pattern in the microstructure in both ferrous and nonferrous alloys. In alloys where the solute atoms occupy interstitial positions in the martensitic lattice (such as carbon in iron), the structure is hard and highly strained; but where the solute atoms occupy substitutional positions (such as nickel in iron), the martensite is soft and ductile. The amount of high-temperature phase that transforms to martensite on cooling depends to a large extent on the lowest temperature attained, there being a rather distinct beginning temperature (Ms) and a temperature at which the transformation is essentially complete (Mf). See also lath martensite , plate martensite , and tempered martensite.
The interval between the martensite start (Ms) and the martensite finish (Mf) temperatures.
A platelike constituent having an appearance and a mechanism of formation similar to that of martensite. See also lath martensite and plate martensite.
A reaction that takes place in some metals on cooling, with the formation of an acicular structure called martensite.
An alloy, rich in one or more desired addition elements, that is added to a metal melt to raise the percentage of a desired constituent.
master alloy powder
A prealloyed metal powder of high concentration of alloy content, designed to be diluted when mixed with a base powder to produce the desired composition. See also prealloyed powder.
In foundry practice, a pattern embodying a double contraction allowance in its construction, used for making castings to be employed as patterns in production work.
A condition in which a point in one metalforming or forging die half is aligned properly with the corresponding point in the opposite die half within specified tolerance.
Two edges of the die face that are machined exactly at 90° to each other, and from which all dimensions are taken in laying out the die impression and aligning the dies in the forging equipment. Also referred to as match lines.
A plate of metal or other material on which patterns for metal casting are mounted (or formed as an integral part) to facilitate molding. The pattern is divided along its parting plane by the plate.
The use of various analytical methods (spectroscopy, microscopy, chromatography, etc.) to describe those features of composition (both bulk and surface) and structure (including defects) of a material that are significant for a particular preparation, study of properties, or use. Test methods that yield information primarily related to materials properties, such as thermal, electrical, and mechanical properties, are excluded from this definition.
The continuous or principal phase in which another constituent is dispersed.
An intermediate product of smelting ; an impure metallic sulfide mixture made by melting a roasted sulfide ore, such as an ore of copper, lead, or nickel.
(1) A dull texture produced by rolling sheet or strip between rolls that have been roughened by blasting. (2) A dull finish characteristic of some electrodeposits, such as cadmium or tin.
maximum stress (Smax)
The stress having the highest algebraic value in the stress cycle, tensile stress being considered positive and compressive stress negative. The nominal stress is used most commonly.
maximum stress intensity factor (Kmax)
The maximum value of the stress-intensity factor in a fatigue cycle.
McQuaid-Ehn grain size
The austenitic grain size developed in steels by carburizing at 927 °C (1700 °F) followed by slow cooling. Eight standard McQuaid-Ehn grain sizes rate the structure, from No. 8, the finest, to No. 1, the coarsest. The use of standardized ASTM methods for determining grain size is recommended.
mean stress (Sm)
The algebraic average of the maximum and minimum stresses in one cycle, that is, Sm = (Smax + Smin)/2. Also referred to as steady component of stress.
mechanical alloying (MA)
An alternate cold welding and shearing of particles of two or more species of greatly differing hardness. The operation is carried out in high-intensity ball mills, such as attritors, and is the preferred method of producing oxide-dispersion-strengthened (ODS) materials. See also attritor grinding and dispersion-strengthened material.
Energy absorbed in a complete cycle of loading and unloading within the elastic limit and represented by the closed loop of the stress-strain curves for loading and unloading. Sometimes referred to as elastic, but more properly, mechanical.
The science and technology dealing with the behavior of metals when subjected to applied forces; often considered to be restricted to plastic working or shaping of metals.
Plating wherein fine metal powders are peened onto the work by tumbling or other means. The process is used primarily to provide ferrous parts with coatings of zinc, cadmium, tin, and alloys of these metals in various combinations.
A process that yields a specularly reflecting surface entirely by the action of machining tools, which are usually the points of abrasive particles suspended in a liquid among the fibers of a polishing cloth.
A press whose slide is operated by a crank, eccentric, cam, toggle links, or other mechanical device.
The properties of a material that reveal its elastic and inelastic behavior when force is applied, thereby indicating its suitability for mechanical applications; for example, modulus of elasticity, tensile strength, elongation, hardness, and fatigue limit. Compare with physical properties.
The methods by which the mechanical properties of a metal are determined.
A twin formed in a crystal by simple shear under external heating.
The subjecting of metals to pressure exerted by rolls, hammers, or presses in order to change the shape or physical properties of the metal.
median fatigue life
The middle value when all of the observed fatigue life values of the individual specimens in a group tested under identical conditions are arranged in order of magnitude. When an even number of specimens are tested, the average of the two middlemost values is used. Use of the sample median rather than the arithmetic mean (that is, the average) is usually preferred.
median fatigue strength at N cycles
An estimate of the stress level at which 50% of the population would survive N cycles. The estimate is derived from a particular point of the fatigue life distribution, since there is no test procedure by which a frequency distribution of fatigue strengths at N cycles can be directly observed. Also known as fatigue strength at N cycles.
The temperature at which a pure metal, compound, or eutectic changes from solid to liquid; the temperature at which the liquid and the solid are at equilibrium.
The range of temperatures over which an alloy other than a compound or eutectic changes from solid to liquid; the range of temperatures from solidus to liquidus at any given composition on a phase diagram.
See melting point.
Complete joint penetration for a joint welded from one side.
merchant mill (obsolete)
A mill, consisting of a group of stands of three rolls each arranged in a straight line and driven by one power unit, used to roll rounds, squares or flats of smaller dimensions than would be rolled on a bar mill.
(1) The number of screen openings per linear inch of screen; also called mesh size. (2) The screen number on the finest screen of a specified standard screen scale through which almost all of the particles of a powder sample will pass. See also sieve analysis and sieve classification.
mesh-belt conveyor furnace
A continuously operating furnace that uses a conveyor belt for the transport of the charge.
(1) An opaque lustrous elemental chemical substance that is a good conductor of heat and electricity and, when polished, a good reflector of light. Most elemental metals are malleable and ductile and are, in general, denser than the other elemental substances. (2) As to structure, metals may be distinguished from nonmetals by their atomic binding and electron availability. Metallic atoms tend to lose electrons from the outer shells, the positive ions thus formed being held together by the electron gas produced by the separation. The ability of these “free electrons” to carry an electric current, and the fact that this ability decreases as temperature increases, establish the prime distinctions of a metallic solid. (3) From a chemical viewpoint, an elemental substance whose hydroxide is alkaline. (4) An alloy.
metal arc cutting
Any of a group of arc cutting processes that severs metals by melting them with the heat of an arc between a metal electrode and the base metal. See also gas metal arc cutting and shielded metal arc cutting.
metal arc welding
Any of a group of arc welding processes in which metals are fused together using the heat of an arc between a metal electrode and the work. Use of the specific process name is preferred.
metal cored electrode
A composite filler metal welding electrode consisting of a metal tube or other hollow configuration containing alloying ingredients. Minor amounts of ingredients facilitate arc stabilization and fluxing of oxides. External shielding gas may or may not be used.
Accelerated deterioration of metals in carbonaceous gases at elevated temperatures to form a dustlike corrosion product.
An electrode used in arc welding or cutting that consists of a metal wire or rod that is either bare or covered with a suitable covering or coating.
A noncrystalline metal or alloy, commonly produced by drastic supercooling of a molten alloy, by molecular deposition, which involves growth from the vapor phase (e.g., thermal evaporation and sputtering) or from a liquid phase (e.g., electroless deposition and electrodeposition), or by external action techniques (e.g., ion implantation and ion beam mixing).
Forming a metallic coating by atomized spraying with molten metal or by vacuum deposition. Also called spray metallizing.
An optical instrument designed for visual observation and photomicrography of prepared surfaces of opaque materials at magnifications of 25 to approximately 2000×. The instrument consists of a high-intensity illuminating source, a microscope, and a camera bellows. On some instruments, provisions are made for examination of specimen surfaces using polarized light, phase contrast, oblique illumination, dark-field illumination, and bright-field illumination.
The study of the structure of metals and alloys by various methods, especially by optical and electron microscopy.
The principal bond that holds metal together and is formed between base metals and filler metals in all welding processes. This is a primary bond arising from the increased spatial extension of the valence electron wave functions when an aggregate of metal atoms is brought close together. Also referred to as metallic bond.
A coke, usually low in sulfur, having a very high compressive strength at elevated temperatures; used in metallurgical furnaces not only as fuel, but also to support the weight of the charge.
The science and technology of metals and alloys. Process metallurgy is concerned with the extraction of metals from their ores and with refining of metals; physical metallurgy, with the physical and mechanical properties of metals as affected by composition, processing, and environmental conditions; and mechanical metallurgy, with the response of metals to applied forces.
A material that consists of a nonmetallic reinforcement, such as ceramic fibers or filaments, incorporated into a metallic matrix.
A surface condition in metal castings in which metal or metal oxides have filled voids between sand grains without displacing them.
Elemental metals or alloy particles, usually in the size range of 0.1 to 1000 m.
metal powder cutting
A technique that supplements an oxyfuel torch with a stream of iron or blended iron-aluminum powder to facilitate flame cutting of difficult-to-cut materials. The powdered material propagates and accelerates the oxidation reaction, as well as the melting and spalling action of the materials to be cut.
Coating metal objects by spraying molten metal against their surfaces. See also thermal spraying.
(1) Of a material not truly stable with respect to some transition, conversion, or reaction but stabilized kinetically either by rapid cooling or by some molecular characteristics as, for example, by the extremely high viscosity of polymers. (2) Possessing a state of pseudoequilibrium that has a free energy higher than that of the true equilibrium state.
For any alloy system, the temperature at which martensite formation on cooling is essentially finished. See also transformation temperature for the definition applicable to ferrous alloys.
A crack of microscopic proportions. Also termed microfissure.
A crack of microscopic proportions.
A graphic reproduction of the surface of a specimen at a magnification greater than 25×. If produced by photographic means it is called a photomicrograph (not a microphotograph).
The hardness of a material as determined by forcing an indenter such as a Vickers or Knoop indenter into the surface of a material under very light load; usually, the indentations are so small that they must be measured with a microscope. Capable of determining hardnesses of different microconstituents within a structure, or of measuring steep hardness gradients such as those encountered in case hardening. See also microhardness test.
A commonly used term for the more technically correct term microindentation hardness number.
A microindentation hardness test using a calibrated machine to force a diamond indenter of specific geometry, under a test load of 1 to 1000 gram-force, into the surface of the test material and to measure the diagonal or diagonals optically. See also Knoop hardness test and Vickers hardness test.
(1) In hardness testing, the small residual impression left in a solid surface when an indenter, typically a pyramidal diamond stylus, is withdrawn after penetrating the surface. Typically, the dimensions of the microindentations are measured to determine microindentation hardness number. (2) The process of indenting a solid surface, using a hard stylus of prescribed geometry and under a slowly applied normal force, usually for the purpose of determining its microindentation hardness number. See also Knoop hardness number , microindentation hardness number , and Vickers hardness number.
microindentation hardness number
A numerical quantity, usually stated in units of pressure (kg/mm2), that expresses the resistance to penetration of a solid surface by a hard indenter of prescribed geometry and under a specified, slowly applied normal force. The prefix “micro” indicates that the indentations produced are typically between 10.0 and 200.0 m across. See also Knoop hardness number , nanohardness test , and Vickers hardness number.
Visible at magnifications above 25×.
Residual stress in a material within a distance comparable to the grain size. See also macroscopic stress.
Segregation within a grain, crystal, or small particle. See also coring.
A casting imperfection, not detectable microspically, consisting of interdendritic voids. Microshrinkage results from contraction during solidification where the opportunity to supply filler material is inadequate to compensate for shrinkage. Alloys with wide ranges in solidification temperature are particularly susceptible.
The strain over a gage length comparable to interatomic distances. These are the strains being averaged by the macrostrain measurement. Microstrain is not measurable by existing techniques. Variance of the microstrain distribution can, however, be measured by x-ray diffraction.
Same as microscopic stress.
The structure of an object, organism, of material as revealed by a microscope at magnifications greater than 25×.
A product intermediate between concentrate and tailing and containing enough of a valuable mineral to make retreatment profitable.
Metal inert-gas welding; see preferred term gas metal arc welding.
Carbon steel with a maximum of about 0.25% C and containing 0.4 to 0.7% Mn, 0.1 to 0.5% Si, and some residuals of sulfur, phosphorus, and/or other elements.
(1) A factory in which metals are hot worked, cold worked, or melted and cast into standard shapes suitable for secondary fabrication into commercial products. (2) A production line, usually of four or more stands, for hot or cold rolling metal standard shapes such as bar, rod, plate, sheet, or strip. (3) A single machine or hot rolling, cold rolling, or extruding metal; examples include blooming mill, cluster mill, four-high mill, and Sendzimir mill. (4) A shop term for a milling cutter. (5) A machine or group of machines for grinding or crushing ores and other minerals. (6) A machine for grinding or mixing material, for example, a ball mill and a paint mill. (7) Grinding or mixing a material, for example, milling a powder metallurgy material.
The normal edge produced in hot rolling of sheet metal. This edge is customarily removed when hot rolled sheets are further processed into cold rolled sheets.
A system for identifying planes and directions in any crystal system by means of sets of integers. The indices of a plane are related to the intercepts of that plane with the axes of a unit cell; the indices of a direction, to the multiples of lattice parameter that represent the coordinates of a point on a line parallel to the direction and passing through the arbitrarily chosen origin of a unit cell.
A nonstandard (and typically nonuniform) surface finish on mill products that are delivered without being subjected to a special surface treatment (other than a corrosion-preventive treatment) after the final working or heat-treating step.
Removing metal with a milling cutter.
milling (powder technology)
The mechanical comminution of a material, usually in a ball mill, to alter the size or shape of the individual particles, to coat one component of a mixture with another, or to create uniform distributions of components.
A rotary cutting tool provided with one or more cutting elements, called teeth, that intermittently engage the workpiece and remove material by relative movement of the workpiece and cutter.
Any commercial product of a mill.
The heavy oxide layer that forms during the hot fabrication or heat treatment of metals.
Physical and chemical concentration of raw ore into a product from which a metal can be recovered at a profit.
A hot dip galvanized coating of very small grain size, which makes the spangle less visible when the part is subsequently painted.
minimum bend radius
The minimum radius over which a metal product can be bent to a given angle without fracture.
minimum stress (Smin)
In fatigue, the stress having the lowest algebraic value in the cycle, tensile stress being considered positive and compressive stress negative.
minimum stress-intensity factor (Kmin)
In fatigue, the minimum value of the stress-intensity factor in a cycle. This value corresponds to the minimum load when the load ratio is >0 and is taken to be zero when the load ratio is 0.
The portion of a powder sample that passes through a standard sieve of a specified number. See also plus sieve and sieve analysis.
An natural mixture of rare-earth elements (atomic numbers 57 through 71) in metallic form. It contains about 50% Ce, the remainder being principally lanthanum and neodymium.
The misalignment or error in register of a pair of forging dies; also applied to the condition of the resulting forging.
Denotes an irregularity on a cast metal surface caused by incomplete filling of the mold due to low pouring temperatures, gas back pressure from inadequate venting of the mold, and inadequate gating.
The potential of a specimen (or specimens in a galvanic couple) when two or more electrochemical reactions are occurring. Also called galvanic couple potential.
In powder metallurgy, the thorough intermingling of powders of two or more different materials (not to be confused with blending ).
Treatment of molten hypoeutectic (8 to 13% Si) or hypereutectic (13 to 19% Si) aluminum-silicon alloys to improve mechanical properties of the solid alloy by refinement of the size and distribution of the silicon phase. Involves additions of small percentages of sodium, strontium, or calcium (hypoeutectic alloys) or of phosphorus (hypereutectic alloys).
modulus of elasticity (E)
(1) The measure of rigidity or stiffness of a material; the ratio of stress, below the proportional limit, to the corresponding strain. If a tensile stress of 13.8 MPa (2.0 ksi) results in an elongation of 1.0%, the modulus of elasticity is 13.8 MPa (2.0 ksi) divided by 0.01, or 1380 MPa (200 ksi). (2) In terms of the stress-strain curve, the modulus of elasticity is the slope of the stress-strain curve in the range of linear proportionality of stress to strain. Also known as Young’s modulus. For materials that do not conform to Hooke’s law throughout the elastic range, the slope of either the tangent to the stress-strain curve at the origin or at low stress, the secant drawn from the origin to any specified point on the stress-strain curve, or the chord connecting any two specific points on the stress-strain curve is usually taken to be the modulus of elasticity. In these cases, the modulus is referred to as the tangent modulus, secant modulus, or chord modulus, respectively.
modulus of resilience
The amount of energy stored in a material when loaded to its elastic limit. It is determined by measuring the area under the stress-strain curve up to the elastic limit. See also resilience and strain energy.
modulus of rigidity
See shear modulus.
modulus of rupture
Nominal stress at fracture in a bend test or torsion test. In bending, modulus of rupture is the bending moment at fracture divided by the section modulus. In torsion, modulus of rupture is the torque at fracture divided by the polar section modulus.
The hardness of a body according to a scale proposed by Mohs, based on ten minerals, each of which would scratch the one below it. These minerals, in decreasing order of hardness, are:
Othoclase (feldspar) 6
(1) The form, made of sand, metal, or refractory material, that contains the cavity into which molten metal is poured to produce a casting of desired shape. (2) A die.
The space in a mold that is filled with liquid metal to form the casting upon solidification. The channel through which liquid metal enters the mold cavity (sprue, runner, gates) and reservoirs for liquid metal (risers) are not considered part of the mold cavity proper.
A machine for making sand molds by mechanically compacting sand around a pattern.
A press used to form powder metallurgy compacts.
Foundry sands containing more than 5% natural clay, usually between 8 and 20%.
Wood or metal form that is slipped over a sand mold for support during pouring of a casting.
An aqueous or alcoholic emulsion or suspension of various materials used to coat the surface of a casting mold cavity.
molten weld pool
The liquid state of a weld prior to solidification as weld metal.
A process for extracting and purifying nickel. The main features consist of forming nickel carbonyl by reaction of finely divided reduced metal with carbon monoxide, then decomposing the nickel carbonyl to deposit purified nickel on small nickel pellets.
An isothermal reversible reaction in a binary system, in which a liquid on cooling decomposes into a second liquid of a different composition and a solid. It differs from a eutectic in that only one of the two products of the reaction is below its freezing range.
The ability of a solid to exist in two or more forms (crystal structures), but in which one form is the stable modification at all temperatures and pressures. Ferrite and martensite are a monotropic pair below the temperature at which austenite begins to form, for example, in steels. Alternate spelling is monotrophism.
The characteristic shape, form, or surface texture or contours of the crystals, grains, or particles of (or in) a material, generally on a microscopic scale.
In crystals, a substructure in which adjoining regions have only slightly different orientations.
mottled cast iron
Iron that consists of a mixture of variable proportions of gray cast iron and white cast iron; such a material has a mottled fracture appearance.
A means by which a specimen for metallographic examination may be held during preparation of a section surface. The specimen can be embedded in plastic or secured mechanically in clamps.
Thermosetting or thermoplastic resins used to mount metallographic specimens.
For any alloy system, the temperature at which martensite starts to form on cooling. See transformation temperature for the definition applicable to ferrous alloys.
The mixing and kneading of foundry molding sand with moisture and clay to develop suitable properties for molding.
Any stress state in which two or three principal stresses are not zero.
A piece of stock for forging that is cut from bar or billet lengths to provide the exact amount of material for a single workpiece.
A weld made by depositing filler metal with two or more successive passes.
A press with individual slides, built into the main slide or connected to individual eccentrics on the main shaft, that can be adjusted to vary the length of stroke and the timing. See also slide.
multiple spot welding
Spot welding in which several spots are made during one complete cycle of the welding machine.
See strain-rate sensitivity.