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Abrasion – The process of rubbing, grinding, or wearing away by friction
Acid Steel – Steel melted in a furnace with an acid bottom and lining and under a slag containing an excess of an acid substance such as silica
Activation – The changing of the passive surface of a metal to a chemically active state. Contrast with passivation
Aging – In a metal or alloy, a change in properties that generally occurs slowly at room temperature and more rapidly at high temperature
Air Frame Tubing – This tubing is produced for aircraft structural parts. It is made to special surface quality, mechanical properties, and other characteristics required by Military Specifications (MIL-T…), SAE Aeronautical Materials Specifications (AMS…), and the American Society for Testing Materials (ASTM.)
Air-Hardening Steel – A steel containing sufficient carbon and other alloying elements to harden fully during cooling in air or other gaseous mediums from a temperature above its transformation range. The term should be restricted to steels that are capable of hardened by cooling in air in fairly large sections, about 2” or more in diameter. Same as self-hardening steel
Aircraft Quality – Steel which has a special cleanliness rating determined by magnetic particle testing. The terms “Aircraft Quality” and “Magnaflux Quality” are considered synonymous
Alclad – Composite sheet produced by bonding either corrosion-resistant aluminum alloy or aluminum of high purity to base metal of structurally stronger aluminum alloy
Alloy Steel – Steel containing significant quantities of alloying elements (other than carbon and the commonly accepted amounts of manganese, silicon, sulfur, and phosphorus) added to effect changes in the mechanical or physical properties
Aluminizing – Forming an aluminum or aluminum alloy coating on a metal by hot dipping, hot spraying, or diffusion
Anisotropy – The characteristic of exhibiting different values of a property in different directions with respect to a fixed reference system in the material
Annealing – Heating to and holding a suitable temperature and then cooling at a suitable rate, for such purposes as reducing hardness, improving machinability, facilitating cold working, producing a desired microstructure, or obtaining desired mechanical, physical, or other properties. When applicable, the following more specific terms should be used: black annealing, blue annealing, box annealing, bright annealing, flame annealing, graphitizing, intermediate annealing, isothermal annealing, malleablizing, process annealing, quench annealing, recrystalization annealing, and spheroidizing. When applied to nonferrous alloys, the term “annealing” implies a heat treatment designed to soften a cold worked structure by recrystalization or subsequent grain growth or to soften an age-hardened alloy by causing a nearly complete precipitation of the second phase in relatively coarse form. Any process of annealing will usually reduce stress, but if the treatment is applied for the sole purpose of such relief, it should be designated stress relieving See also Heat Treatment of Steel, Heat Treatment of Aluminum,
Atomic-Hydrogen Welding – Arc welding with heat from an arc between two tungsten or other suitable electrodes in a hydrogen atmosphere. The use of pressure and filler metal is optional
Attenuation – The fractional decrease of the intensity of an energy flux, including the reduction of intensity resulting from geometrical spreading, absorption, and scattering
Austempering – Quenching a ferrous alloy from a temperature above the transformation range, in a medium having a rate of heat abstraction high enough to prevent the formation of high-temperature transformation products, and then holding the alloy, until transformation is complete, at a temperature below that of pearlite formation and above that of martensite formation
Austenite – A solid solution of one or more elements in face-centered cubic iron
Austenitic Stainless Steel – Low carbon, iron-chromium-nickel stainless alloys containing more that 16% chromium, with sufficient nickel to provide an austenitic structure at normal temperatures. These alloys cannot be hardened by heat treatment, but can be hardened by cold working. They are normally nonmagnetic, but can be slightly magnetic depending upon composition and amount of cold working
Austenitizing – Forming austenite by heating a ferrous alloy into the transformation range (partial austenitizing) or above the transformation range (complete austenitizing)
Autofrettage – Prestressing a hollow metal cylinder by the use of momentary internal pressure exceeding the yield strength


Bainite – A decomposition product of austenite consisting of an aggregate of ferrite and carbide. In general, it forms at temperatures lower than those where very fine pearlite forms and higher than that where martensite begins to form on cooling. Its appearance is feathery if formed in the upper part of the temperature range; acicular, resembling tempered martensite, if formed in the lower part
Banded Structure – A segregated structure of nearly parallel bands aligned in the direction of working
Bark – The decarburized layer just beneath the scale that results from heating steel in an oxidizing atmosphere
Basic Steel – Steel melted in a furnace with a basic bottom and lining and under a slag containing an excess of a basic substance such as magnesia or lime
Bearing Load – A compressive load supported by a member, usually a tube or collar, along a line where contact is made with a pin, rivet, axle, or shaft
Bearing Quality Steels – Steels suitable for use in balls, rollers, and races of high-quality anti-friction bearings
Bearing Strength – The maximum bearing load at failure divided by the effective bearing area. In a pinned or riveted joint, the effective area is calculated as the product of the diameter of the hole and the thickness of the bearing member
Bend Radius – The inside radius of a bent section
Bend Test – A test for determining relatively ductility of metal that is to be formed, usually sheet, strip, plate, or wire, and for determining soundness and toughness of metal. The specimen is usually bent over a specified diameter through a specified angle for a specified number of cycles
Bessemer Process – A process for making steel by blowing air through molten pig iron contained in a refractory lines vessel so as to remove by oxidation most of the carbon, silicon, and manganese
Bevel – An angular cut on the I.D. or O.D. of a tube
Billet – A solid semi-finished round or square product that has been hot worked by foraging, rolling, or extrusion. An iron or steel billet has minimum width or thickness of 1-1/2” and the cross-sectional are varies from 2-1/4 to 36 sq. in. For nonferrous metals it may also be a casting suitable for finished or semi-finished rolling or for extrusion. As used in the manufacture or seamless tubes, it is a round bar with dimensions and other characteristics suitable for piercing into tubing
Blister – A defect in metal, on or near the surface, resulting from the expansion of gas in a subsurface zone. Very small blisters are called “pinheads” or “pepper blisters”
Bloom – A semi-finished hot rolled product, rectangular in cross section, produced on a blooming mill. For iron and steel, the width is not more than twice the thickness, and the cross-sectional area is usually not less than 36 sq. in. Iron and steel blooms are sometimes made by foraging
Blue Annealing – Heating hot rolled ferrous sheet in an open furnace to a temperature within the transformation range and then cooling in air, in order to soften the metal. The formation of a bluish oxide on the surface is incidental
Blue Brittleness – Brittleness exhibited by some steels after being heated to some temperature with the range of 300°F – 650°F, and more especially if the steel is worked at the elevated temperature. Killed steels are virtually free of this kind of brittleness
Bluing – Subjecting the scale-free surface of a ferrous alloy to the action of air, steam, or other agents at a suitable temperature, thus forming a thin blue film of oxide and improving the appearance and resistance to corrosion
Borescope – An optical device used for inspecting, under low magnification, the inside surface of tubes
Box Annealing – Annealing a metal or alloy in a sealed container under conditions that minimize oxidation. In box annealing a ferrous alloy, the charge is usually heated slowly to a temperature below the transformation range, but sometimes above or within it, and is then cooled slowly; this process is also called “close annealing” or “pot annealing”
Bright Annealing – Annealing in a protective medium to prevent discoloration of the bright surface
Brinell Hardness Test – A test for determining the hardness of a material by forcing a hard steel or carbide ball of specified diameter into it under a specified load
Brittle Fracture – Fracture with little or no plastic deformation
Broken Surface – A surface having innumerable minute cracks running normal to the direction of working
Burning(1) Permanently damaging a metal or alloy by heating to cause either incipient melting or intergranular oxidation. See also Overheating (2) In grinning, getting the work hot enough to cause discoloration or to change the microstructure by tempering or hardening
Burnishing – Smoothing surfaces through frictional contact between the work and some hard pieces of material such as hardened metal balls
Bus Conductor – A rigid conductor of any cross section, i.e., Aluminum Bus Pipe


Caburizing – Adding carbon to the surface of iron-base alloys by heating the metal below its melting point in contact with carbonaceous solids, liquids, or gases. Desired hardness and toughness properties are developed in the high carbon “case” by quenching and tempering
Camber(1) Deviation from edge straightness usually referring to the greatest deviation of side edge from a straight line. (2) Sometimes used to denote crown in rolls where the center diameter has been increased to compensate for deflection caused by the rolling pressure
Canning – A dished distortion in a flat or nearly flat surface, sometimes referred to as “oil canning”
Capped Steel – Semikilled steel cast in a bottle-top mold and covered with a cap fitting into the neck of the mold. The cap causes the top metal to solidify, and prevents the formation of an excessive number of gas voids with the ingot. Pressure is built up in the sealed-in molten metal and results in a surface condition much like that of rimmed steel
Carbide – A compound consisting of carbon and other elements
Carbide Precipitation – The phenomenon of carbides coming out of a solid solution, occurring in stainless steel when heated into the range of 800°F - 1600°F
Carbon Steel – Steel containing carbon up to about 2% and only residual quantities of other elements except those added for deoxidation, with silicon usually limited to 0.60% and manganese to about 1.65%. Also termed “plain carbon steel”, “ordinary steel”, and “straight carbon steel”
Carbonitriding – Introducing carbon and nitrogen into a solid ferrous alloy by holding above Ac₁ in an atmosphere that contains suitable gases such as hydrocarbons, carbon monoxide, and ammonia. The carbonitrided alloy is usually quench hardened
Case Hardening – Hardening a ferrous alloy so that the outer portion, or case, is made substantially harder than the inner portion, or core. Typical processes used for case hardening are carburizing, cyaniding, carbonitriding, nitriding, induction hardening, and flame hardening
Cavitation – The formation and instantaneous collapse of innumerable tiny voids or cavities within a liquid subjected to rapid and intense pressure changes. Cavitation produced by severe turbulent flow often leads to cavitation damage
Cavitation Damage – Wearing away of metal through the formation and collapse of cavities in liquid
Cementite – A compound of iron and carbon, known chemically as iron carbonide and having the approximate chemical formula Fe₃C. It is characterized by an orthorhombic crystal structure. When it occurs as a phase in steel, the chemical composition will be altered by the presence of manganese and other carbide-forming elements
Centrifugal Casting – A casting made of pouring metal into a mold that is rotated or revolved
Ceramic Tools – Cutting tools made from the fused, sintered, or cemented metallic oxides
Chamfer(1) A beveled surface to eliminate an otherwise sharp corner (2) A relieved angular cutting edge at a tooth corner
Charpy Impact Test – A pendulum-type single-blow impact test in which the specimen, usually notched, is supported at both ends as a simple beam and broken by a falling pendulum. The energy absorbed, as determined by the subsequent rise of the pendulum, is a measure of impact strength or notch toughness See also Impact Test
Check Analysis – An analysis of the metal after it has been rolled or forged into semi-finished or finished forms. It is not a check on the ladle analysis, but is a check against the chemistry ordered, i.e. Product Analysis
Chemical Milling – Removing metal stock by controlled selective chemical etching
Chloride Stress CrackingSee Stress-corrosion Cracking
Chromadizing (Chromodizing, Chromatizing) – Forming an acid surface to improve paint adhesion on aluminum or aluminum alloys, mainly aircraft skins, by treatment with a solution of chromic acid
Chromizing – A surface treatment at elevated temperature, generally carried out in pack, vapor, or salt bath, in which an alloy is formed by the inward diffusion of chromium into the base metal
Clad Metal – A composite metal containing two or three layers that have been bonded together. The bonding may have been accomplished by corolling, welding, casting, heavy chemical deposition, or heavy electroplating
Cleanup – The amount of metal removed required to obtain desired dimensions and complete removal of the inherent surface imperfections
Coefficient of Thermal Expansion – A physical property value representing the change in length per unit length, the change in area per unit area, or the change in volume per unit volume per one degree increase in temperature
Coil Breaks – Creases or ridges across metal sheet transverse to the direction of coiling, occasionally occurring when the metal has been coiled hot and uncoiled cold
Cold Drawing – A process in which the tube is drawn at room temperature through a die and over a mandrel to achieve its final size and to provide better surface finish, closer tolerances, lighter walls, smaller diameters, longer lengths, or a different combination of mechanical properties from those possible through hot finishing or direct welding
Cold Reduction – The reduction of sectional dimensions of a tube by any of a number of types of cold working operations
Cold Short – A condition of brittleness existing in some metals at temperatures below the recrystallization temperature
Cold Shut(1) A discontinuity that appears on the surface of cast metal as a result of two streams of liquid meeting and failing to unite (2) A portion of the surface of a foraging that is separated, in part, from the main body of metal by oxide
Cold Sinking – Similar to cold drawing, except that the tube is drawn through a die, but without an internal mandrel. Usually used only for making heavy wall or small tube, where drawing over a mandrel is impractical
Cold Working – Permanent strain produced by an external force in a metal below its recrystallization temperature
Columnar Structure – A coarse structure of parallel columns of grains, having the long axis perpendicular to the casting surface
Compressive Strength – The maximum compressive stress that a material is capable of developing, based on original area of cross section. in the case of a material which fails in compression by a shattering fracture, the compressive strength has a very definite value. In the case of materials which do not fail in compression by a shattering fracture, the value obtained for compressive strength is an arbitrary value depending upon the degree of distortion that is regarded as indicating complete failure of the material
Conditioning – The removal of surface defects (seams, laps, pits, etc) from steel. Conditioning is usually done when the steel is in semi-finished condition (bloom, billet, slab). It may be accomplished, after an inspection, by chipping, scarfing, grinding, or machining
Continuous Casting – A casting technique in which an ingot, billet, tube, or other shape is continuously solidified while it is being poured, so that its length is not determined by mold dimensions
Copper-Copper Sulfate Test – An intergranular corrosion test for stainless steels. The specimen is placed in boiling copper-copper-sulfate-sulfuric acid for 24 hours after which it is bent to expose any surface intergranular attack. This test is often preferred over the Huey test because it requires much less time
Corrosion – Chemical or electrochemical deterioration of a metal or alloy
Galvanic Corrosion – Corrosion associated with the presence of two dissimilar metals in a solution (electrolyte). In principle, it is similar to bath-type plating in the sense that the anode surface has lost metal (corroded)
Intergranular Corrosion – Corrosion which occurs preferentially along the grain boundaries of the alloy
Pitting Corrosion – Non-uniform corrosion usually forming small cavities in the metal surface
Corrosion Embrittlement – The severe loss of ductility of a metal resulting from corrosive attack, usually intergranular and often not visually apparent
Corrosion Fatigue – Effect of the application of repeated or fluctuating stresses in a corrosive environment characterized by shorter life than would be encountered as a result of either the repeated or fluctuating stresses alone or the corrosive environment alone
Corrosion Resistance – The ability to resist attack of corrosion
Covered Electrode – A filler-metal electrode, used in arc welding, consisting of a metal core wire with a relatively thick covering which provides protection for the molten metal from the atmosphere, improves the properties of the weld metal and stabilizes the arc. The covering is usually mineral or metal powders mixed with cellulose or other binder
Creep – Time-dependent strain occurring under stress. The creep strain occurring at a diminishing rate is called primary creep; that occurring at a minimum and almost constant rate, secondary creep; that occurring at an accelerating rate, tertiary creep
Creep Limit(1) The maximum stress that will cause less than a specified quantity of creep in a given time. (2) The maximum nominal stress under which the creep strain rate decreases continuously with time under constant load and at constant temperature. Sometimes used synonymously with creep strength
Creep Strength(1) The constant nominal stress that will cause a specified quantity of creep in a given time at constant temperature. (2) The constant nominal stress that will cause a specified creep rate at constant temperature
Crevice Erosion – A type of concentration-cell corrosion; corrosion of a metal that is caused by the concentration of dissolved salts, metal ions, oxygen, or other gases, and such, in crevices or pockets remote from the principal fluid stream, with a resultant building up of differential cells that ultimately cause deep pitting
Critical Cooling Rate – The minimum rate of continuous cooling just sufficient to prevent undesired transformations. For steel, the slowest rate at which it can be cooled from above the upper critical temperature to prevent the decomposition of austenite at any temperature above the Mₛ
Critical Point(1) The temperature or pressure at which a change in crystal structure, phase, or physical properties occurs. Same as transformation temperature. (2) In an equilibrium diagram, that specific value of composition, temperature and pressure, or combinations thereof, at which the phases of a heterogeneous systems are in equilibrium
Cross Rolling – The rolling of sheet so that the direction of rolling is changed about 90º from the direction of the previous rolling
Crown – Crown, in plates, sheets, or strips, is characterized by a greater thickness in the middle than at the edges. It may be caused by a deflecting (bending) of the rolls or by worn rolls
Cup Fracture (Cup-and-Cone Fracture) – Fracture, frequently seen in tensile test pieces of a ductile material in which the surface of failure on one portion shows a central flat area of failure in tension, with an exterior extended rim of failure in shear
Cut Length – Refers to product ordered to a specified length and permitting a tolerance of a standardized fraction of an inch over but nothing under the specified length
Cutting Speed – The linear or peripheral speed of relative motion between the tool and workpiece in the principal direction of cutting
Cyaniding – Introducing carbon and nitrogen into a solid ferrous alloy by holding above Ac1 in contact with molten cyanide of suitable composition. The cyanided alloy is usually quench hardened


Decarburization – The loss of carbon from the surface of an iron-base alloy as the result of heating in an environment which removes the carbon. In medium or high carbon steels, decarburization leads to a pronounced lowering of the fatigue limit
Dendrite – A crystal that has a tree-like branching pattern, being most evident in cast metals slowly cooled through the solidification range
Density – The mass-per-unit volume of a substance, usually expressed in the metals industry in pounds per cubic inch
Die Line – A longitudinal depression or protrusion formed on the surface of drawn or extruded material due to imperfections on the die surface
Outside Diameter (O.D., OD) – Specified in inches and fractions of an inch, or inches and decimals of an inch
Inside Diameter (I.D., ID) – Specified in the same units as O.D.
Mean Diameter – The average of two measurements of the diameter taken at right angles to each other
Wall – Wall thickness or gauge. Specified in either fractions or decimals of an inch or by a “wire gauge” number. In the United States, the most common gauge used for tube id the Birmingham iron gauge, designated “B.W.G.”
Nominal – The theoretical or stated value of the O.D., I.D., or wall dimension as specified by the customer
Maximum and Minimum – The dimensions resulting after applying the proper tolerances to the nominal dimensions
Minimum Wall – Generally, the lightest wall permitted within specified tolerances. A “minimum wall tube” is one whose wall thickness is not permitted to fall below the specified nominal measurement
Average Wall – A tube whose wall thickness is permitted to range over and under the specified nominal wall measurement within certain defined tolerances
Mean Wall – The average of two measurements of the wall thickness of a tubular product taken opposite each other
Direct Chill Casting (DC Casting) – A continuous method of making ingots or billets for sheet 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
Drawing(1) Forming recessed parts by forcing the plastic flow of metal in dies. (2) Reducing the cross section of wire or tubing by pulling it through a die. (3) A misnomer for tempering
Drop Forging – A forging made with a drop hammer
Drop Hammer – A forging hammer than depends on gravity for its force
Ductile Crack Propagation – Slow crack propagation that is accompanied by noticeable plastic deformation and requires energy to be supplied from outside the body
Ductility – The ability of a material to deform plastically without fracturing, being measured by elongation or reduction of area in a tensile test, by height of cupping in an Erichsen test or by other means
Duplex (Austenitic/Ferrite) Stainless Steel – A stainless steel whose microstructure at room temperature consists primarily of a near equal mixture of austenite and ferrite
Duralumin – (obsolete) — A term formerly applied to the class of age-hardenable aluminum-copper alloys containing manganese, magnesium, or silicon
Dye Penetrant Inspection – Non-destructive test employing dye or fluorescent chemical and sometimes black light to detect surface defects


Earing – The formation of scallops (ears) around the top edge of a drawn part caused by differences in the directional properties of the sheet metal used
Eccentricity – The displacement of the I.D. of the tube wall with respect to its O.D.; i.e., deviation from a common center. The permissible degree of eccentricity can be expressed by a plus and minus wall-thickness tolerance
Eddy-Current Testing – Nondestructive testing method in which eddy-current flow is induced in the test object. Changes in the flow caused by variations in the object are reflected into a nearby coil or coils for subsequent analysis by suitable instrumentation and techniques
Elastic Limit – The maximum stress to which a material may be subjected without any permanent strain remaining upon complete release of stress
Electric Furnace Process – One of the common methods used for melting and refining stainless and some alloy steels. It involves the use of electric power as the sole source of heat, thereby preventing contamination of the steel by impurities in the fuel as in other melting processes
Electric Resistance Welded Steel Tube – Tube made from strip, sheet, or bands by electric resistance heating and pressure, the strip being part of the electrical circuit. The electric current, which may be introduced into the strip through electrodes or by induction, generates the welding heat through the electrical resistance of the strip
As-Welded Hot Rolled – ERW tube exhibiting the pickled or shot-blasted surface of hot rolled strip
As-Welded Cold Rolled – ERW tube exhibiting the surface of cold rolled strip
As-Drawn – Tube that is unheat-treated and cold drawn, and has a scale-free, cold drawn surface
Bright Annealed – Welded tube normalized in a controlled atmosphere furnace and which exhibits a bright surface
Pickled – Tube that has had the scale from hot fabrication or heat treatment removed by one of several types of acid solutions
Gun Metal Finish – Welded tube normalized, annealed, or stress relieved in a controlled atmosphere furnace which exhibits a gun metal finish
Flash-In – Tube that is welded and still retains the I.D. bead or flash formed during the welding operation. It can be furnished in either as=welded, suck, or heat-treated condition
Flash-Removed – Welded tube from which the I.D. flash formed during the welding operation has been removed by some mechanical method. It can be furnished in either the As-Welded, sunk, or heat-treated condition
Special Smooth I.D. – A cold drawn tube in which special attention is paid to the internal surface. Depth of pits and scores in I.D. are guaranteed to be below published maximum depths. Micro-inch finish is guaranteed in ERW tubes
Electrical Conductivity – The capacity of a material to conduct electrical current. For aluminum, this capacity is expressed as a percentage of the international Annealed Copper Standard which has a resistivity of 1/38 ohm-mm2/meter at 20°C and an arbitrarily designed conductivity of unity
Electrical Resistivity – The electrical resistance of a body of a unit length and unit cross-sectional area or weight. The value of 1/38 ohm-mm2/meter at 20°C is the resistivity equivalent to the International Annealed Copper Standard (IACS) for 100% conductivity
Elongation – In tensile testing, the increase in the gauge length, measured after fracture of the specimen within the gauge length, usually expressed as a percentage of the original gauge length
End-Quench Hardenability Test (Jominy Test) – A laboratory procedure for determining the hardenability of a steel; widely referred to as the jominy test. The date are normally plotted as hardness versus distance from the quenched end
Endurance LimitSee Fatigue Limit
Erichsen Test – A cupping test in which a piece of sheet metal, restrained except at the center, is deformed by a cone-shaped spherical-end plunger until fracture occurs. The height of the cup in millimeters at fracture is a measure of the ductility
Etch Test – Exposure of a specimen to acid attack for the purpose of disclosing the presence of foreign matter, defects, segregation pattern, or flow lines
Exfoliation – A type of corrosion that progresses approximately parallel to the outer surface of the metal, causing layers of the metal to be elevated by the formation of corrosion product
Extrusion Seam – A seam in aluminum tube, pipe or hollow shape resulting from the pressure bonding at two or more edges in the course of extruding through a bridge, porthole die


Fatigue – The phenomenon leading to fracture under repeated or fluctuating stresses having a maximum value less than the tensile strength of the material. Fatigue fractures are progressive, beginning as minute cracks that grow under the action of the fluctuating stress
Fatigue Life – The number of cycles of stress that can be sustained prior to failure for a stated test condition
Fatigue Limit – The maximum stress below which a material can presumably endure an infinite number of stress cycles. If the stress is not completely reversed, the value of the mean stress, the minimum stress, or the stress ratio should be stated
Fatigue Strength – The maximum stress that can be sustained for a specified number of cycles without failure, the stress being completely reversed within each cycle unless otherwise stated
Ferrite – A solid solution of one or more elements in body-centered cubic iron. unless otherwise designated (for instance, as chromium ferrite), the solute is generally assumed to be carbon. on some equilibrium diagrams there are two ferrite regions separated by an austenite area. The lower area is alpha ferrite; the upper, delta ferrite. if there is no designation, alpha ferrite is assumed
Ferrite Banding – Parallel bands of free ferrite aligned in the direction of working. Sometimes referred to a ferrite streaks
Ferrite Stainless Steels – The designation used for certain straight chromium steels which exhibit microstructures consisting mainly of ferrite at ordinary temperatures. Ferritic stainless steels are divided into two classifications; hardenable, and non-hardenable. When rapidly cooled from elevated temperatures the non-hardenable grades (ferritic) have a ferritic microstructure. The hardenable grades (martenistic) will exhibit a martenistic microstructure when rapidly cooled
Fiber Stress – Local stress through a small area (a point or line) on a section where the stress is not uniform, as in a beam under a bending load
Finish – Refers to the type of surface condition desired or existing in the finished product
Finish Machine Size – Normally specified in terms of the maximum machined O.D. and the minimum machined I.D. as applied to tubular parts. Finish machine sizes represents the size of the part as it comes from the final machining operation. From this size the tube mill can calculate a tube size which will be guaranteed to clean up upon machining
Fish Eyes – Areas on a fractured steel surface having a characteristic white crystalline appearance
Flakes – Short discontinuous internal fissures in ferrous metals attributed to stresses produced by localized transformation and decreased solubility of hydrogen during cooling after hot working. in a fractured surface, flakes appear as bright silvery areas; on an etched surface they appear as short discontinuous cracks. Also called “shatter cracks” and “snowflakes”
Flame Annealing – Annealing in which the heat is applied directly by a flame
Flame Hardening – Quench hardening in which the heat is applied directly by a flame
Flanged End – In a flanged end, a tube has been belled or expanded and a flange turned over until the wall of the tube end is at right angle to the wall of the tube
Flare Test – A test applied to tubing, involving a tapered expansion over a cone. Similar to pin expansion test
Flash(1) In forging, the excess metal forced between the upper and lower dies. (2) In die casting, the fin of metal which results from leakage between the mating die surfaces. (3) In resistance butt welding, a fin formed perpendicular to the direction of applied pressure
Flash Welding – A resistance butt welding process in which the weld is produced over the entire abutting surface by pressure and heat, the heat being produced by electric arcs between the members being welded
Flux Leakage Test – Non-destructive test which uses magnetic lines of force to recognize any discontinuity in the test piece
Foil – Metal in sheet form less than 0.006 in. in thickness
Forging – Plastically deforming metal, usually hot, into desired shapes with compressive force, with or without dies
Fractography – Descriptive treatment of fracture, especially in metals, with specific reference to photographs of the fracture surface. Macrofractography involves photographs at low magnification; microfractography, at high magnification
Fracture Structure – As usually related to the tensile test, fracture strength or true breaking strength is defined as the load on the specimen at the time of fracture
Fracture Test – Breaking a specimen and examining the fractured surface with the unaided eye or with a low-power microscope to determine such things as composition, grain size, case depth, soundness, and presence of defects
Free Machining – Pertains to the machining characteristics of an alloy to which an ingredient has been introduced to give small broken chips, lower power consumption, better surface finish, and longer tool life; among such additions are sulphur or lead to steel, lead to brass, lead and bismuth to aluminum, and sulphur or selenium to stainless steel
Fretting (Fretting Corrosion) – Action that results in surface damage, especially in a corrosive environment, when there is relative motion between solid surfaces in contact under pressure
Full Annealing – Annealing a ferrous alloy by austenitizing and then cooling slowly through the transformation range. The austenitizing temperature to hypoeutectoid steel is usually above Ac₃; and for hypereutectoid steel, usually between Ac₁ and Ac_cm
Full Finished – Refers to stainless tube in which the weld has been processed to produce uniform strength and dimensions, and subsequently annealed to obtain proper corrosion resistance


Gages (Gauges) – A measurement of thickness. There are various standard gauges such as United Stated Standard Gauge (USS), Galvanized Sheet Gauge (GSG), and Birmingham Wire Gauge (BWG)
Galling – Developing a condition on the rubbing surface of one or both mating parts where excessive friction between high spots results in localized welding with substantial spalling and a further roughening of the surface
Galvanic Corrosion – Corrosion associated with the current of a galvanic cell consisting of two dissimilar conductors in an electrolyte or two similar conductors in dissimilar electrolytes. Where the two dissimilar metals are in contact, the resulting action is referred to as “couple action”
Grain Size – For metals, a measure of the areas or volumes of grains in a polycrystalline material, usually expressed as an average when the individual sizes are fairly uniform. Grain sizes are reported in terms of grains per unit area or volume, average diameter, or as a grain-size number derived from area measurements
Apparent Ferrite Grain Size – The average of the size of the ferrite grains as microscopically viewed in the normalized or annealed conditions
Austenitic Grain Size – Usually measured by the McQuaid-Ehn method, it represents the austenitic grain size of a material at a prescribed temperature above the upper critical, frequently 1700°F. For austenitic stainless steels the grain size does not change upon cooling and is that observed microscopically at room temperature
Granular Fracture – A type of irregular surface produced when metal is broken, that is characterized by a rough, grainlike appearance as differentiated from a smooth silky, or fibrous, type. it can be subclassified into transgranular and intergranular forms. This type of fracture is frequently called crystalline fracture, but the inference that the metal has crystallized is not justified
Graphitizing – Annealing a ferrous alloy in such a way that some or all of the carbon is precipitated as graphite
Gray Cast Iron – A cast iron that gives a gray fracture due to the presence of flake graphite, often called gray iron
Grinding Cracks – Shallow cracks formed in the surface of relatively hard materials because of excessive grinding heat or the high sensitivity of the material
Gun Drill – A drill, usually with one or more flutes and with coolant passages through the drill body, used for deep hole drilling


Hammer Forging – Forging in which the work is deformed by repeated blows. Compare with press forging
Hard Chromium – Chromium deposited for engineering purposes, such as increasing the wear resistance of sliding metal surfaces, rather than as a decorative coating. it is usually applied directly to basis metal and is customarily thicker than a decorative deposit
Hardenability – In a ferrous alloy, the property that determines the depth and distribution of hardness induced by quenching
Hardening – Increasing the hardness by suitable treatment, usually involving heating and cooling
Hardness – The Metals Handbook defines hardness as "Resistance of metal to plastic deformation, usually by indentation." However, the term may also refer to stiffness or temper, or to resistance to scratching, abrasion, or cutting. It is the property of a metal, which gives it the ability to resist being permanently, deformed (bent, broken, or have its shape changed), when a load is applied. The greater the hardness of the metal, the greater resistance it has to deformation.
Heat Analysis – Formerly known as ladle analysis
Heat Exchanger Tube – A tube for use in apparatus in which fluid inside the tube will be heated or cooled by fluid outside the tube. The term usually is not applied to coiled tubes for use in refrigerators or radiators
Heat Treatment of Aluminum – Aluminum alloys are divided into two distinct groups based on their reaction to thermal treatment. Heat-treatable tube alloys (2000, 6000, and 7000 series) can be strengthened by thermal treatment and subjected to repeated heat treatment cycles without harmful effects. Non-heat-treatable tube alloys (1000, 3000, and 5000 series) can be strengthened only by cold working.
Aging – Precipitation from solid solution resulting in a change in properties of an alloy, usually occurring slowly at room temperature (natural again) and more rapidly at elevated temperatures (artificial aging)
Age Hardening – An aging process which results in increased strength and hardness
Age Softening – The loss of strength and hardness at room temperature which takes places in certain alloys due to the spontaneous reduction of residual stresses in the strain hardened structure
Annealing – A thermal treatment to soften metal by removal of stress resulting from cold working or by coalescing precipitates from solid solution. Performed on all aluminum alloys at approximately 650°F soaking temperature
Homogenizing – A high-temperature soaking treatment to eliminate or reduce segregation by diffusion. Performed on the ingot at 900°F - 1000°F temperature range
Precipitation Hardening – The final step in solution heat treating. Artificial aging is performed at temperatures ranging from 240°F to 460°F depending upon heat-treatable aluminum alloy See also Aging
Solution Heat Treating – Heating an alloy at a suitable temperature for sufficient time to allow soluble constituents to enter into solid solution where they are retained in a super-saturated state after quenching. Performed in the temperature range of 825°F - 980°F depending upon heat-treatable aluminum allow, and followed by aging
Stabilizing – A thermal treatment to reduce internal stresses in order to promote dimensional and mechanical property stability. Applied only to 3000 and 5000 series alloys in cold worked temper. Performed at about 350°F See also Age Softening, Stress Relieving,
Stress Relieving – The reduction of the effects of internal residual stresses by thermal or mechanical means
Heat Treatment of Steel – A combination of heating and cooling operations applied to a metal or alloy in the solid state to obtain desired conditions or properties. Heating for the sole purpose of hot working is excluded from the meaning of this definition.
Age Hardening – An aging process that increases hardness and strength. Ordinarily ductility decreases. Age hardening usually follows rapid cooling or cold working. Hardening is a result of precipitation process, often sub-microscopic, which occurs when a supersaturated solid solution is naturally aged at atmospheric temperature or artificially aged in some specific range of elevated temperature. Aging occurs more rapidly at higher temperatures. (Synonymous with precipitation hardening)
Air Hardening – Heating a suitable grade of steel with high hardenability above the critical temperature range and then cooling in air for the purpose of hardening
Anneal – The annealing process is a combination of a heating cycle, a holding period, and a controlled cooling cycle. Annealing is used to obtain a variety of results, among which are: to soften or alter the grain structure of steel, to develop formability, machinability, and required mechanical properties, or to relieve residual stress. The temperatures and cooling rates used depend on which results are desired. It is generally desirable to use more specific terms in describing the anneal
Bright Anneal – Carried out in a controlled furnace atmosphere, so that surface oxidation is reduced to a minimum and the tube surface remains relatively bright
Dead Soft Anneal – A heat treatment applied to achieve maximum softness and ductility
Finish Anneal – Heating to a temperature above the upper critical (above 1650°F) and slow cooling below the lower critical, usually in a furnace See also Full Annealing
Soft Anneal – When maximum softness and ductility are required without change in grain structure, material should be ordered soft annealed. This process consists of heating to a temperature slightly below the critical temperature and cooling still in the air. Usually performed in the 1250°F to 1350°F range for carbon steel
Solution Anneal – Heating steel into a temperature range wherein certain elements or compound dissolve, followed by cooling at a rate sufficient to maintain these elements in solution at room temperature. The expression is normally applied to stainless and other special steels
Spheroidizing Anneal – A general term which refers to heat treatments that promote spheroidal or globular forms of carbide in carbon or alloy steels
Stabilizing Anneal – A treatment applied to austenitic stainless steels wherein carbides of various forms are deliberately precipitated. Sufficient additional time is provided at the elevated temperature to diffuse chromium into areas adjacent to the carbides (usually grin boundaries). This treatment is intended to lessen the change of intergranular corrosion
Stress Relief Anneal – Often referred to as “finish annealing” involves 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. Stress relieving normally takes place in the 950°F - 1150°F temperature range for carbon steel
Normalize – A process which consists of heating to a temperature approximately 100°F above the critical temperature (above 1650°F) and cooling in still air at room temperature. Normalizing is utilized to obtain moderate increases in hardness in medium carbon steels or to alter the weld microstructure in lower carbon steels
Quenching – A process or rapid cooling from an elevated temperature, by contact with liquid or gases. Quenched hardenable steels usually are extremely brittle and are not suitable for use unless subsequently tempered
Tempering – Reheating quenched or normalized steel to a temperature below the transformation range (lower critical) followed by any desired rate of cooling. Tempering reduces brittleness and develops the desired hardness, structure, and properties
Heat-affected Zone – That portion of the base metal which was not melted during brazing, cutting, or welding, but whose microstructure and physical properties were altered by the heat
Homogenizing – Holding at high temperature to eliminate or decrease chemical segregation by diffusion
Honing – Removing stock generally on the internal cylindrical surface of a workpiece with an abrasive stick mounted in a holder
Hot Finished Seamless Tubing – Tubing produced by rotary piercing, extrusion, and other hot working processes without subsequent cold finishing operations
Hot Rolled ERW Tubing – As-welded electric resistance welded tubing made from hot rolled strip, sheet, or bands
Hot Shortness – Brittleness in metal in the hot forming range
Hot Top – A reservoir, thermally insulated or heated, to hold molten metal on top of a mold to feed the ingot or casting as it contracts on solidifying to avoid having “pipe” or voids
Hot Working – The mechanical working of the metal above the recrystallization temperature
Huey Test – A corrosion test for stainless steels. The weight loss per unit area is measured after each 48-hour boils in 65% nitric acid. The test results are calculated to and reported as the average corrosion rate of the five oils in inches per month (ipm) corrosion rates. The test is used to determine the suitability of a material for nitric acid service. Since most of the weight loss id due to intergranular attack, the Huey test can be used as an indication of the resistance of a stainless steel to intergranular corrosion
Hydrogen Embrittlement – A condition of low ductility in metals resulting from the absorption of hydrogen


Immersed Scanning – In ultrasonic, a planned, systematic movement of the beam relative to the object being inspected, the search unit being coupled to this object through a column of liquid. in most cases the object and the search unit are submerged in water
Impact Energy (Impact Value) – The amount of energy required to fracture a material, usually measured by means of an Izod or Charpy test. The type of specimen and testing conditions affect the values and therefore should be specified
Impact Test – A test to determine the behavior of materials when subjected to high rates of loading, usually in bending, tension, or torsion. The quantity measured is the energy absorbed in breaking the specimen by a single blow, as in the Charpy or Izod tests
Inclusions – Nonmetallic materials in a solid metallic matrix
Induction Hardening – Quench hardening in which the heat is generated by electrical induction
Inert-Gas Shielded-arc Welding – Arc welding in an inert gas such as argon or helium
Ingot Iron – Commercially pure open-hearth iron
Ingot Mold – A mold in which ingots are cast. Mold may be circular, square, or rectangular in shape, with the walls of various thickness. Some molds are of larger cross sections at the bottom; others are larger at the top
Integral Finned Tubing – Tubing with raised surface fins formed from the wall of the tube itself
Intergranular Corrosion – A type of electrochemical corrosion that progresses preferentially along the grain boundaries of an alloy, usually because the grain boundary regions contain material anodic to the central regions of the grain
Internal Soundness – Refers to condition of inside of material- lack of defects, pipe, segregation, non-uniformity of composition
Interrupted Quenching – Quenching in which the metal object being quenched is removed from the quenching medium while the object is at a temperature substantially higher than that of the quenching medium
Investment Casting(1) Casting metal into a mold produced by surrounding (investing) an expendable pattern with a refractory slurry that sets at room temperature after which the wax, plastic, or frozen mercury pattern is removed through the use of heat. Also called precision casting, or lost-wax process. (2) A casting made by the process
Isothermal Transformation – A change in phase at any constant temperatureIzod Test
Izod Test – A pendulum type of single-blow impact test in which the specimen, usually notched, is fixed at one end and broken by a falling pendulum. The energy absorbed, as measured by the subsequent rise of the pendulum, is a measure of impact strength or notch toughness


Jominy Test – Hardenability test performed usually on alloy steels to determine depth and degree of hardness resulting from a standard end quenching method with cold water See also End-Quench Hardenability Test (Jominy Test)


Killed Steel – Steel deoxidized with a strong deoxidizing agent such as silicon or aluminum in order to reduce the oxygen content to such a level that no reaction occurs between carbon and oxygen during solidification
Kip – A load of 1,000 lbs.


Ladle – A large vessel into which molten steel is received and handled
Ladle Analysis – Chemical analysis obtained from a sample taken during the pouring of steel
Laminations – Metal defects with separation or weakness generally aligned parallel to the worked surface of the metal. May be the result of pipe, blisters, seams, inclusions, or segregation elongated and made directional by working. Lamination defects may also occur in metal-powder compacts
Lap – A surface defect, appearing as a seam, caused by folding over hot metal, fins, or sharp corners and then rolling or forging them into the surface, but not welding them
Light Metal – One of the low-density metals such as aluminum, magnesium, titanium, beryllium, or their alloys
Longitudinal Direction – The principal direction of flow in a worked metal
Low-hydrogen Electrode – A covered arc-welding electrode that provides an atmosphere around the arc and molten weld metal which is low in hydrogen


Machinability – The relative ease of machining a metal
Machinability Index – A relative measure of the machinability of an engineering material under specified standard conditions
Machining – The deliberate removal of metal by one or more of several processes
Macro-etch – Etching of a metal surface for accentuation of gross structural details and defects for observation by the unaided eye or at magnifications not exceeding ten diameters
Macrostructure – The structure of metals as revealed by examination of the etched surface of a polished specimen at a magnification not exceeding ten diameters
Magnaflux Test – This test is conducted by suitably magnetizing the material and applying a prepared wet or dry magnetic powder or fluid which adheres to it along lines of flux leakage. It shows the existence of surface and slightly sub-surface non-uniformities
Magnetic-Particle Inspection – A nondestructive method of inspection for determining the existence and extent of possible defects 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
Malleability – The property that determines the ease of deforming a metal when the material is subjected to rolling or hammering
Mandrel – A device used to retain a cavity in hollow metal products
Maraging – A process of improving the mechanical strength of certain ferrous alloys
Martempering – Quenching an austenitized ferrous alloy in a medium at a temperature in the upper part of the martensite range, or slightly above that range, and holding it in the medium until the temperature throughout the alloy is substantially uniform. The alloy is then allowed to cool in air through the martensite range
Martensite(1) In an alloy, a metastable transitional structure intermediate between two allotropic modifications whose abilities to dissolve a given solute differ considerably, the high-temperature phase having the greater solubility. The amount of the high-temperature phase transformed to martensite depends to a large extent upon the temperature attained in cooling, there being a rather distinct beginning temperature. (2) A metastable phase of steel, formed by a transformation of austenite below the Mₛ (or Ar”) temperature. It is an interstitial supersaturated solid solution of carbon in iron having a body-centered tetragonal lattice. Its microstructure is characterized by an acicular, or needle-like, pattern
McQuaid-Ehn Test – A special test for revealing the austenitic grain size of ferritic steels when the steel is heated to 1700°F and carburized. There are eight standard McQuaid-Ehn grain sizes – sizes 5 to 8 are considered fine grain and sizes 5 and under are considered coarse grain
Mechanical Properties – The properties of a material that reveal its elastic and inelastic behavior where force is applied, thereby indicating its suitability for mechanical applications; for example, modulus of elasticity, tensile strength, elongation, hardness, and fatigue limit
Mechanical Tubing – Used for a variety of mechanical and structural purposes, as opposed to pressure tubing. It may be hot or cold finished
Megapascal (MPA)) – A unit of pressure (forced divided by area) in the metric system. To convert MPAs to pounds per sq inch (PSI) multiply the metric unit by 145.0
Metallography – The science dealing with the constitution and structure of metals and alloys as revealed by the unaided eye or by such tools as low-powered magnification
Metric System of Measurements – In the metric system of measurements, the principle unit for length is the meter; the principle unit for volume, the liter; and the principle unit for weight, the gram. The following prefixes are used for subdivisions and multiples: milli = 1/1000; centi = 1/100; deci = 1/10; deca = 10; hector = 100; kilo = 1000. In abbreviations, the subdivisions are frequently used with a smaller letter and the multiples with a capital letter, although the practice is not universally followed everywhere the metric system is used. All the multiples and subdivisions are not used commercially. Those ordinarily used for length are kilometer, meter, centimeter, and millimeter; for are square meter, square centimeter, and square millimeter. The most commonly used for weights are the kilogram and gram. The metric system was legalized in the United States by an Act of Congress in 1866
Micro-Etch – Micro-etching is used for the examination of a sample under microscope. Etching solutions tend to reveal structural details because of preferential chemical attack on polished surface
Microcleanliness – Refers to the extent or quality of nonmetallic inclusions observed by examination under a microscope
Minimum Wall – Any wall having tolerances specified all on the plus side
Modulus of Elasticity – A measure of the rigidity of metal. Ratio of stress, within proportional limit, to corresponding strain. Specifically, the modulus obtained in tension or compression is Young’s modulus, stretch modulus or modulus of extensibility; the modulus obtained in torsion or shear is modulus of rigidity, shear modulus or modulus of torsion; the modulus covering the ratio of the mean normal stress to the change in volume per unit volume is the bulk modulus. The tangent modulus and secant modulus are not restricted within the proportional limit; the former is the slope of the stress-strain curve at a specified point; the latter is the slope of a line from the origin to a specified point on the stress-strain curve. Also called “elastic modulus” and “coefficient of elasticity”


Nitriding – Introducing nitrogen into a solid ferrous alloy by holding at a suitable temperature (below Ac₁ for ferritic steels) in contact with a nitrogenous material, usually ammonia of molten cyanide of appropriate composition. Quenching is not required to produce a hard case
Non-Destructive Testing – Methods of detecting without destroying or permanently changing the material being tested. Test methods include ultrasonic, eddy current, flux leakage, magnetic particle, liquid, and X-ray
Normalizing – Heating a ferrous alloy to a suitable temperature above the transformation range and then cooling in air to a temperature substantially below the transformation range
Notch Brittleness – Susceptibility of a material to brittle fracture at point of stress concentration
Notch Sensitivity – A measure of the reduction in strength of a metal caused by the presence of stress concentration


Open-Hearth Furnace – A reverberatory melting furnace with a shallow hearth and low roof. The flame passes over the charge in the hearth, causing the charge to be heated both by direct flame and radiation from the roof and sidewalls of the furnace. In ferrous industry, the furnace is regenerative
Orange Peel – A pebble-grain surface which develops in forming of metal having course grains
Ovality – The difference between the max and min outside diameters of any cross section of a tube. It is a measure of deviation from roundness
Overaging – Aging under conditions of time and temperature greater than those required to obtain max change in a certain property, so that the property is altered in direction of the initial value
Overheating – Heating a metal or alloy to such a high temperature that its properties are impaired. When the original properties cannot be restored by further heat treating., by mechanical working, or by combination of working heat treating, the overheating is know as burning
Oxalic Acid Etch Test – A quick metallographic test which is sometimes used to screen stainless before intergranular corrosion testing. This test is specified with a referee test such as the Copper-Copper Sulfate or Huey Test
Oxidation – Combination of substance with oxygen. Scale developed during heat treatment is a form of oxidation
Oxide – A compound consisting of oxygen and one or more metallic elements
Oxygen-Free Copper – Electrolytic copper free from cuprous oxide, produced without the sue of residual metallic or metalloidal deoxidizers


Pack Rolling – Hot rolling a pack of two or more sheets of metal; scale prevents their being welded together
Pancake Forging – A rough forged shape which may be obtained quickly with min of tooling. It usually requires considerable machining to attain the finish size
Passivation – The changing of the chemically active surface of a metal to a much less reactive state by the application of the proper chemical treatment, or by applying an induced electrical current and voltage for cathodic or anodic protection from corrosion
Pearlite – A lamellar aggregate of ferrite and cementite, often occurring in steel and case iron
Peening – Mechanical working of metal by hammer blows or shot impingement
Penetrant Inspection – A method of nondestructive testing for determining the existence and extent of discontinuities that are open to the surface in the part being inspected. The indications are made visible through the use of a dye or fluorescent chemical in the liquid employed as the inspection medium
Photomicrograph – A photographic reproduction of an object magnified more than ten times used to show microstructure characteristics of steel
Physical Properties – The properties, other than mechanical properties, that pertain to the physics of a material; for example, density, electrical conductivity, thermal expansion
Pickling – Removing surface oxides from metals by chemical or electrochemical reaction
Piercing – A seamless tube making method in which a hot billet is gripped and rotated by rolls or cones and directed over a piercer point which is held on the end of a mandrel bar
Pig Iron – High–carbon iron made by reduction of iron ore in the blast furnace
Pin Expansion Test – A test for determining the ability of tubes to be expanded, or for revealing the presence of cracks or other longitudinal weaknesses, made by forcing a tapered pin into the open end of a tube
Pipe(1) The central cavity formed by contraction in metal, especially ingots, during solidification. (2) The defect in wrought or case products resulting from such a cavity (3) An extrusion defect due to the oxidized surface of the billet flowing toward the center of the rod at the back end (4) A tubular metal product, cast or wrought
Pitting – Forming small sharp cavities in a metal surface by nonuniform electro-deposition or by corrosion
Planishing – Producing a smooth surface finish on metal by rapid succession of blows delivered by highly polished dies or by a hammer designed for the purpose, or by rolling in a planishing mill
Porosity – Unsoundness cause in cast metals by the presence of blowholes or shrinkage cavities
Postheating – Heating weldments immediately after welding, for tempering, for stress relieving, or for providing a controlled rate of cooling to prevent formation of a hard or brittle structure
Precipitation Hardening – Hardening caused by the precipitation of a constituent from a supersaturated solid solution
Preheating – Heating before some further thermal or mechanical treatment. For tool steel, heating to an intermediate temperature immediately before austenitizing. For some nonferrous alloys, heating to a high temperature for a long time, in order to homogenize the structure before working
Press Forging – Forging metal, usually hot, between dies in a press
Pressure Tubing – Tubing produced for the purpose of containing fluids or gas under pressure
Primes – Metal products, principally sheet and plate, of the highest quality and free from visible defects
Process Annealing – In the sheet and wire industries, heating a ferrous alloy to a temperature close to, but below, the lower limit of the transformation range and then cooling, in order to soften the alloy for further cold working
Product Analysis – Formerly known as check analysis
Profilometer – An instrument used for measuring surface finish. The vertical movement of stylus as it transverses the surface are amplified electromagnetically and recorded as the surface roughness
Proof Stress(1) The stress that will cause a specified small permanent set in a material (2) A specified stress to be applied to a member or structure to indicate its ability to withstand service loads
Proportional Limit – The maximum stress at which strain remains directly proportional to stress
Pulse-echo Method – A nondestructive test in which pulses of energy are directed into a part, and the time for the echo to return from one or more reflecting surfaces is measured
Pyrometer – An instrument of any of various types used for measuring temperatures


Quench Cracking (of Steel) – Cracking resulting from stresses produced during the austenite to martensite transformation during heat treating (quenching and tempering). Any condition that concentrates the stresses encountered in quenching will promote the formation of quench cracks (e.g. corners, hoves, or keyways; too fast a quench medium; excessive time delay from quench to temper)
Quench Hardening – Hardening a ferrous alloy by austenitizing and then cooling rapidly enough so that some or all of the austenite transforms to martensite. The austenitizing temperature for hypoeutectoid steels is usually above Ac3 and for hypereutectoid steels usually between Ac1 and Accm


Random Length – Tube produced to a permissible variation in length. (Frequently seven feet)
Recrystallization(1) The change from one crystal structure to another, as occurs on heating or cooling through a critical temperature. (2) The formation of a new, strain-free grain structure from that existing in cold worked metal, usually accomplished by heating
Recrystallization Temperature – The approximate minimum temperature at which complete recrystallization of a cold worked metal occurs within a specified time
Reduction of Area(1) Commonly, the difference, expressed as a percentage of original area, between the original cross-sectional area of a tensile test specimen and the minimum cross-sectional area measured after complete separation. (2) The difference, expressed as a percentage of original area, between original cross-sectional area and that after straining the specimen
Refractory Metal – A metal having an extremely high melting point. In the broad sense, it refers to metals having melting points above the range of iron, cobalt, and nickel
Residual Stress – Stress present in a body that is free of external forces or thermal gradients
Rimmed Steel – A low-carbon steel containing sufficient iron oxide to give a continuous evolution of carbon monoxide while the ingot is solidifying, resulting in a case or rim of metal virtually free of voids. Sheet and strip products made from the ingot have very good surface quality
Rockwell Hardness – The Rockwell scale is a hardness scale based on indentation hardness of a material. The Rockwell test determines the hardness by measuring the depth of penetration of an indenter under a large load compared to the penetration made by a preload. See also Hardness
Roller Leveling – Leveling by passing flat stock through a machine having a series of small-diameter staggered rolls
Roto-Rock (Tube Reducing, Rockrite) – A method of cold finishing tube in which a machine rolls or rocks a split die over a tube. This tube is supported on the inside of a tapered mandrel
Rough Machining – Machining without regard to finish, usually to be followed by a subsequent operation


Scab – A defect consisting of a flat volume of metal joined to a casting through a small area. It is usually set in a depression, a flat side being separated from the metal of the casting proper by a thin layer of sand
Scale – An oxide of iron which forms on the surface of hot steel
Scaling – Forming a thick layer of oxidation products on metals at high temperatures
Scalped Extrusion Ingot – A cast, solid, or hollow extrusion ingot which as been machined on the outside surface
Scarfing – Cutting surface areas of metal objects, ordinarily by using a gas torch. The operation permits surface defects to be cut from ingots, billets, or the edges of plate that is to be beveled for butt welding
Scleroscope Test – A hardness test where the loss in kinetic energy of a falling metal “tup”, absorbed by indentation upon impact of the tup on the metal being tested, is indicated by the height of rebound
Seam – On the surface of metal, an unwelded fold or lap which appears as a crack, usually resulting from a defect obtained in casting or in working
Secondary Hardening – Tempering certain alloy steels at certain temperatures so that the resulting hardness is greater than that obtained by tempering the same steel at some lower temperature for the same time
Segregation – Nonuniform distribution of alloying elements, impurities or microphases
Semikilled Steel – Steel that is completely deoxided and contains sufficient dissolved oxygen to react with the carbon to form carbon monoxide to offset solidification shrinkage
Sendzimir Mill – A mill having two works rolls of 1 to 21/2-in. diam. each, backed up by two rolls twice that diameter and each of these backed up by bearings on a shaft mounted eccentrically so that rotating it increases the pressure between bearings and backup rolls
Sensitization – Sensitization of stainless steel is defined as a susceptibility to preferential grain boundary attack. Material which exhibits grain boundary carbide precipitation may or may not be sensitized
Shear Strength – The stress required to produce fracture in the plane of cross section, the conditions of loading being such that the directions of force and of resistance are parallel and opposite although their paths are offset a specified minimum amount
Shell Molding – Forming a mold from thermosetting resin-bonded sand mixtures brought in contact with preheated (300° to 500°F) metal patterns, resulting in a firm shell with a cavity corresponding to the outline of the pattern. Also called “Croning process”
Shielded-arc Welding – Arc welding in which the arc and the weld metal are protected by a gaseous atmosphere, the products of decomposition of the electrode covering, or a blanket of fusible flux
Shore Hardness TestSee Scleroscope Test
Shortness – A form of brittleness in metal. It is designed as “cold”, “hot”, and “red”, to indicate the temperature range in which the brittleness occurs
Siliconizing – Diffusing silicon into solid metal, usually steel, at an elevated temperature
Skelp – A piece or strip of metal produced to a suitable thickness, width, and edge configuration, from which pipe or tubing is made
Skull – A layer of solidified metal or dross on the wall of a pouring vessel after the metal has been poured
Slack Quenching – The process of hardening steel by quenching from the austenitizing temperature at a rate slower than the critical cooling rate for the particular steel, resulting in incomplete hardening and the formation of one or more transformation products in addition to or instead of martensite
Soak – To hold an ingot, slab, bloom, billet or other piece of steel in a hot furnace, pit, or chamber to secure uniform temperature
Soaking Pit – A furnace or pit for the heating of ingot of steel to make their temperature uniform prior to rolling or forging
Solid Solution – A single solid homogeneous crystalline phase containing two or more chemical species
Solution Heat Treatment – Heating an alloy to a suitable temperature, holding at that temperature long enough to allow one or more constituents to enter into solid solution, and then cooling rapidly enough to hold the constituents in solution. The alloy is left in a supersaturated, unstable state, and may subsequently exhibit quench aging
Sorbite – (obsolete) — A fine mixture of ferrite and cementite produced either by regulating the rate of cooling of steel or tempering steel after hardening. The first type is very fine pearlite difficult to resolve under the microscope; the second type is tempered martensite
Spalling – The cracking and flaking of particles out of a surface
Special Smooth I.D. (SSID)See Electric Resistance Welded Steel Tube
Specification – A document defining the measurements, tests, and other requirements to which a product must conform: typically covering chemistry, mechanical properties, tolerances, finish, reports, marking and packaging
Spheroidizing – Heating and cooling to produce a spheroidal or globular form of carbide in steel. Spheroidizing methods frequently used are:
  1. Prolonged holding at a temperature just below Ae₁
  2. Heating and cooling alternately between temperatures that are just below Ae₁
  3. Heating to a temperature above Ae₁ or Ae₃ and then cooling very slowly in the furnace or holding at a temperature just below Ae₁
  4. Cooling at a suitable rate from the minimum temperature at which all carbide is dissolved, to prevent the reformation of a carbide network, and then reheating in accordance with methods 1 or 2 above. (Applicable to hypereutectoid steel containing a carbide network.)
Spinning – A type of forming (hot or cold) which involves rotating a tube at high speed against fixed or rolling tools for the purpose of altering shape
Spot Welding – Welding of lapped parts in which fusion is confined to a relatively small circular area. It is generally resistance welding, but may also be gas-shielded tungsten-arc, gas-shielded metal-arc, or submerged-arc welding
Stabilizing Treatment(1) Any treatment intended to stabilize the structure of an alloy of the dimensions of a part. (2) Heating austenitic stainless steels that contain titanium, columbium, or tantalum to a suitable temperature below that of a full anneal in order to inactivate the maximum amount of carbon by precipitation as a carbide of titanium, columbium, or tantalum. (3) Transforming retained austenite in parts made from tool steel. (4) Precipitating a constituent from a nonferrous solid solution to improve the workability, to decrease the tendency of certain alloys to age harden at room temperature, or to obtain dimensional stability
Stainless Steel – Steel containing 10.5% or more chromium. Other elements may be added
Standard Gold – A legally adopted alloy for coinage of gold. In the United States the alloy contains 10% Cu.
Steel – An iron-base alloy, malleable in some temperature range 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 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%; ingot iron contains considerably less
Sterling Silver – A silver alloy containing at least 95.2% Ag, the remainder being unspecified but usually copper
Strain – A measure of the change in the size or shape of a body, referred to its original size or shape. “Linear strain” is the change per unit length of a linear dimension. “True strain” (or “natural strain”) is the natural logarithm of the ratio of the length at the moment of observation to the original gauge length. “Conventional strain” is the linear strain referred to the original gauge length. “Shearing strain” (or “shear strain”) is the change in angle (expressed in radians) between two lines originally at right angles. When the term strain is used alone it usually refers to the linear strain in the direction of the applied stress
Strain Hardening – Modification of a metal structure by cold working, resulting in an increase in strength and hardness with loss of ductility
Stress – Force per unit area, often thought of as force acting through a small area within a plane. It can be divided into components, normal and parallel to the plane, called “normal stress” and “shear stress”, respectively. “True stress” denotes the stress where force and area are measured at the same time. “Conventional stress”, as applied to tension and compression tests, is force by the original area. “Nominal stress” is the stress computed by simple elasticity formulas, ignoring stress raisers and disregarding plastic flow; in a notch bend test, for example, it is bending moment divided by minimum section modulus
Stress Relieving – 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
Stress-corrosion Cracking – Failure by cracking under combined action or corrosion and stress, either external (applied) or internal (residual). Cracking may be either intergranular or transgranular depending on metal and corrosive medium
Stress-rupture Test – A tension test performed at constant temperature, the load being held at such a level as to cause rupture. Also known as “Creep-rupture test”
Stretcher Leveling – Leveling where a piece of metal is gripped at each end and subjected to a stress higher than its yield strength to remove warp and distortion. Sometimes called patent leveling
Stretcher Straightening – 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
Stretcher Strains – Elongated markings that appear on the surface of some 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. Same as Luders lines
Strip – A flat-rolled steel product which serves as the raw material for welded tube
Sunk (Sink Drawn) – Tube drawn through a die with no inside mandrel to control I.D. or wall thickness
Superalloy – An alloy developed for very high temperature service where relatively high stresses (tensile, thermal, vibratory, and shock) are encountered and where oxidation resistance is frequently required
Superficial Rockwell Hardness Test – Form of Rockwell hardness test using relatively light loads which produce minimum penetration. Used for determining surface hardness or hardness of thin sections or small parts, or where large hardness impression might be harmful
Swaged – A mechanical reduction of the cross sectional area of a metal performed hot or cold by forging, pressing or hammering


Tack Welds – Small scattered welds made to hold parts of a weldment in proper alignment while the final welds are being made
Tapping – The act of pouring molten metal from a furnace into a ladle
Teeming – Act of pouring molten metal from a ladle into an ingot mold
Temper(1) In heat treatment, reheating hardened steel or hardened cast iron to some temperature below the eutectoid temperature for the purpose of decreasing the hardness and increasing the toughness. The process also is sometimes applied to normalized steel. (2) In tool steels, “temper” is sometimes used, but inadvisedly, to denote the carbon content. (3) In nonferrous alloys and in some ferrous alloys (steels that cannot be hardened by heat treatment), the hardness and strength produced by mechanical or thermal treatment, or both, and characterized by a certain structure, mechanical properties, or reduction in area during cold working
Temper Brittleness – Brittleness that results when certain steels are held within, or are cooled slowly through, a certain range of temperature below the transformation range. The brittleness is revealed by notched-bar impact tests at or below room temperature
Tempering – Reheating a quench-hardened or normalized ferrous alloy to a temperature below the transformation range and then cooling at any rate desired
Tensile Strength – In tensile testing, the ratio of maximum load to original cross-sectional area. Also called ultimate strength
Thermal Conductivity – A measure of the ease with which heat is transmitted through material
Tolerance – Permissible variation
Tong Hold – The portion of a forging billet, usually on one end, that is gripped by the operator’s tongs. It is removed from the part at the end of the forging operation. Common to drop-hammer and press-type forging
Torsion – A twisting action resulting in sheer stresses and strains
Toughness – Ability of a metal to absorb energy and deform plastically before fracturing. It is usually measured by the energy absorbed in a notch impact test, but the area under the stress-strain curve in tensile testing is also a measure of toughness
Transformation Ranges (Transformation Temperature Ranges) – Those ranges of temperature within which austenite forms during heating and transforms during cooling. The two ranges are distinct, sometimes overlapping but never coinciding. The limiting temperatures of the ranges depend on the composition of the alloy and on the rate of change of temperature, particularly during cooling. See also Transformation Temperature
Transformation Temperature – The temperature at which a change in phase occurs. The term is sometimes used to denote the limiting temperature of a transformation range. The following symbols are used for irons and steels:
  • Accm – In hypereutectoid steel the temperature at which the solution of cementite in austenite is completed during heating
  • Ac1 – The temperature at which austenite begins to form during heating
  • Ac3 – The temperature at which transformation of ferrite to austenite is completed during heating
  • Ac4 – The temperature at which austenite transforms to delta ferrite during heating
  • Aecm, Ae1, Ae3, Ae4 – The temperature of phase changes at equilibrium
  • Arcm – In hypereutectoid steel, the temperature at which precipitation of cementite starts during cooling
  • Ar1 – The temperature at which transformation of austenite to ferrite or to ferrite plus cementite is completed during cooling
  • Ar3 – The temperature at which austenite begins to transform to ferrite during cooling
  • Ar4 – The temperature at which delta ferrite transforms to austenite during cooling
  • Ms (or Ar”) – The temperature at which transformation of austenite to martensite starts
  • during cooling
  • Mf – The temperature at which martensite formation finishes during cooling

Note: All these changes except the formation of martensite occur at lower temperatures during cooling than during heating, and depend on the rate of change of temperature

Transition Temperature(1) An arbitrarily defined temperature within the temperature range in which metal fracture characteristics determined usually by notched tests are changing rapidly such as a primarily fibrous (shear) to primarily crystalline (cleavage) fracture. Commonly used definitions are “transition temperature for 50% cleavage fracture”, “10-ft-lb transition temperature”, and “transition temperature for half maximum energy”. (2) Sometimes also used to denote the arbitrarily defined temperature in a range in which the ductility changes rapidly with temperature
Transverse – Literally, “across”, usually signifying a direction or plane perpendicular to the direction of working
Transverse Tension Test – A tension test for evaluating mechanical properties of a material in a direction transverse to that of rolling
Trepanning – A type of boring where an annular cut is made into a solid material with the coincidental formation of a plug or solid cylinder
Troosite – (obsolete) — A previously unresolvable rapidly etching fine aggregate of carbide and ferrite produced either by tempering martensite at low temperature or by quenching a steel at a rate slower than the critical cooling rate. Preferred terminology for the first product is tempered martensite; for the latter fine pearlite
Turning – A method for removing the surface from a work piece by bringing the cutting edge of a tool against it while the piece or tool is rotated


Ultimate Strength – The maximum conventional stress, tensile, compressive, or shear, that a material can withstand
Ultrasonic Frequency – A frequency, associated with elastic waves, that is greater than the highest audible frequency, generally regarded as being higher than 15 kc per sec.
Ultrasonic Waves – Waves of ultrasonic frequency. They include longitudinal, transverse, surface, and standing waves
Universal Mill – A rolling mill in which rolls with a vertical axis roll the edges of the metal stock between some of the passes through the horizontal rolls
Upsetting – A metal-work operation similar to forging, generally used to thicken the ends of tubes prior to threading


Vacuum Melting – Melting in a vacuum to prevent contamination from air, as well as to remove gases already dissolved in the metal; the solidification may also be carried out in a vacuum or at low pressure
Vickers Hardness Test – The Vickers test can be used for all metals and has one of the widest scales among hardness tests. See also Hardness


Wetting – A phenomenon involving a solid and a liquid in such intimate contact that the adhesive force between the two phases is greater than the cohesive force within the liquid. Thus a solid that is wetted, on being removed from the liquid bath, will have a thin continuous layer of liquid adhering to it. Foreign substances such as grease may prevent wetting. Addition agents, such as detergents, may induce wetting by lowering the surface tension of the liquid
Widmanstatten Structure – A structure characterized by a geometrical pattern resulting from the formation of a new phase along certain crystallographic planes of the parent solid solution. The orientation of the lattice in the new phase is related crystallographically to the orientation of the lattice in the parent phase. The structure was originally observed in meteorites but is readily produced in many other alloys with certain heat treatment
Work Hardening – Hardness developed in metal as a result of cold working
Wrought Iron – A commercial iron consisting of slag (iron silicate) fibers entrained in a ferrite matrix


Yield Point – The first stress in a material, usually less than the maximum attainable stress, at which an increase in strain occurs without an increase in stress. Only certain metals exhibit a yield point. If there is a decrease in stress after yielding, a distinction may be made between upper and lower yield points
Yield Strength – The stress at which a material exhibits a specified deviation from proportionality of stress and strain. An offset of 0.2% is used for many metals
Young’s ModulusSee Modulus of Elasticity