Glossary of Terms

Boiler and boiler tube industry terms and their definitions.


Age HardeningSee Heat Treatment.
Air Frame TubingThis tubing is produced for aircraft structural parts. This tubing is made to special surface quality, mechanical properties and other characteristics required by Military Specifications (MIL-T - . . . ) and SAE Aeronautical Materials Specifications. (AMS.).
Air HardeningSee Heat Treatment.
Aircraft QualityIs a steel which has a special cleanliness rating determined by magnetic particle testing. The terms Aircraft Quality and Magnafux Quality are considered synonymous.
Alloy SteelAll steels contain carbon and small amounts of silicon, sulfur, manganese, and phosphorus. Steels which contain intentional additions of elements other than these, or in which silicon and manganese are present in large amounts for the express purpose of improving or altering any of the physical or mechanical properties of the steel, are termed alloy steels.
AnnealingSee Heat Treatment.
Austenitic Stainless SteelLow carbon, iron-chromium-nickel stainless alloys containing more than 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 non-magnetic, but can be slightly magnetic depending upon composition and amount of cold working.
Average WallSee dimensions.



Bearing Quality SteelsSteels suitable for use in balls, rollers, and races of high quality anti-friction bearings.
BevelAn angular cut on the I.D. or O.D. of a tube end.
BilletAs used in the manufacture of seamless tubes, a round bar with dimensions and other characteristics suitable for piercing into tubing.
BloomA semi-finished piece of steel, resulting from the rolling or forging of an ingot. A bloom is square or not more than twice as wide as thick, and usually not less than 36-sq. in. in cross-sectional area.
BorescopeAn optical device used for inspecting under low magnification the inside surface of tubes.
Bright AnnealSee heat treatment
Brinell HardnessSee hardness



CamberThe amount of curvature or deviation form exact straightness over any specified length of tubing.
Capped SteelSemi-killed steel which has characteristics similar to those of rimmed steels but to a degree intermediate between rimmed and killed steel. The capping operation limits the time of gas evolution and prevents the formation of an excessive number of gas voids within the ingot.
CarbideA compound consisting of carbon and other elements.
Carbide PrecipitationThe phenomenon of carbides coming out of a solid solution, occurring in stainless steel when heated into the range of 800-1600 degrees Fahrenheit.
Carbon SteelA steel consisting of essentially iron, carbon, manganese, and silicon. Carbon steel has no minimum content required for aluminum, chromium, cobalt, columbium, molybdenum, nickel, titanium, tungsten, vanadium, zicronium or any other element added to obtain alloying effect. Small quantities of certain residual elements are considered incidental.
CarburizingAdding carbon to the surface of iron-based 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.
Case HardeningA heat treatment in which the surface (case) of an iron-base alloy is made harder than the interior (core). Any of the following methods may be employed: flame hardening, induction hardening, carburizing, cyaniding, or nitriding.
Charpy Impact TestSee Impact Testing.
Check AnalysisAn 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.
Chloride Stress CrackingSee Stress Corrosion Cracking
CleanupThe amount of metal removal required to obtain desired dimensions and complete removal of inherent surface imperfections.
Coefficient of Thermal ExpansionA 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.
Cold DrawingA process in which tubing 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 ReductionThe reduction of sectional dimensions of a tube by any of a number of types of cold-working operations.
Cold SinkingSimilar 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 tubing, where drawing over a mandrel is impractical. Only outside diameter is closely controlled.
Cold WorkingPermanent plastic deformation of a metal below its recrystallization temperature.
ConditioningThe 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.
Copper-Copper Sulfate TestAn 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.
CorrosionChemical or electrochemical deterioration of a metal or alloy.
CorrosionPitting Corrosion - Non-uniform corrosion usually forming small cavities in the metal surface.
Corrosion IntergranularIntergranular Corrosion - Corrosion which occurs preferentially along the grain boundaries of the alloy.
Corrosion ResistanceThe ability to resist attack by corrosion.
Corrosion-GalvanicCorrosion 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).
Creep StrengthThe constant nominal stress that will cause a specified quantity of creep in a given time at a constant temperature. It is a measure of a tubes ability to withstand prolonged stress or load without significant continuous deformation. In steels it is an important factor only at elevated temperatures.
CrownCrown, in plates, sheet, 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.
Cut LengthRefers to tubing ordered to a specified length and permitting a tolerance of a standardized fraction of an inch over but nothing under the specified length.
CyanidingA process in which an iron-base alloy is heated in contact with a cyanide salt so that the surface absorbs carbon and nitrogen. Cyaniding is followed by quenching and tempering to produce a case with a desired combination of hardness and toughness.



DecarburizationThe loss of carbon forms 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.
DensityThe mass per unit volume of a substance, usually expressed in the tubing industry in pounds per cubic inch.
DimensionsO.D . - Outside Diameter. Specified in inches and fractions of an inch, or inches and decimals of an inch.
DimensionsI.D. - Inside Diameter. Specified in the same units as O.D.
DuctilityThe ability of a tube to deform plastically. Frequently, elongation during tensile testing is used as a measurement of this property.
Dye Penetrant InspectionNon-destructive test employing dye or fluorescent chemical and sometimes black light to detect surface defects.



EccentricityThe displacement of the I.D. of the tube with respect to its O.D. Eccentricity results in the variation of wall thickness normal to seamless tubing.
Eddy CurrentNon-destructive testing method using eddy current flow for the purpose of recognizing a discontinuity in the piece being tested.
Elastic LimitA measure of the maximum stress that may be applied to a tube without leaving a permanent deformation or strain after the stress is released.
Electric Furnace ProcessOne 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 Tubing (ERW)Tubing 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.
ERW Tubing - As DrawnAs Drawn tubing is unheat-treated, cold drawn tubing and has a scale free cold drawn surface.
ERW Tubing - As Welded Cold RolledAs Welded Cold Rolled - ERW tubing exhibiting the surface of cold rolled strip.
ERW Tubing - As Welded Hot RolledAs Welded Hot Rolled - ERW tubing exhibiting the pickled or shot blasted surface of hot rolled strip.
ERW Tubing - Bright AnnealedBright Annealed - Welded tubing normalized in a controlled atmosphere furnace and which exhibits a bright surface.
ERW Tubing - Flash InFlash-In tubing us welded tubing which still retains the I.D. bead or flash formed during the welding operation. It can be furnished in either the as-welded, sunk, or heat-treated condition.
ERW Tubing - Flash RemovedFlash-Removed - Welded tubing 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.
ERW Tubing - Gun MetalGun Metal Finish - Welded tubing normalized, annealed, or stress relieved in a controlled atmosphere furnace which exhibits a gun metal finish.
ERW Tubing - PickledPickled tubing has had the scale from hot fabrication or heat treatment removed by one of several types of acid solutions.
ERW Tubing - Special Smooth I.D.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. Microinch finish is guaranteed in ERW tubes.
ElongationThe amount of permanent stretch, usually referring to a measurement of a specimen after fracture in a tensile test. It is expressed as a percentage of the original gage length.
Endurance LimitThe maximum stress below which a material can presumably endure an infinite number of stress cycles.
Etch TestExposure of a specimen to acid attack for the purpose of disclosing the presence to foreign matter, defects, segregation pattern, or flow lines.
ExtrusionProduction process in which steel is forced by compression through a die into solids (round or special shape) or through a die and over a mandrel to form a tubular shape.



Fatigue LimitSynonymous with Endurance Limit
Ferritic Stainless SteelsThe 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 (martensitic) will exhibit a martensitic microstructure when rapidly cooled.
FinishIn the steel industry, refers to the type of surface condition desired or existing in the finished product.
Finish AnnealSee Heat Treatment.
Finish Machine SizeNormally specified in terms of the maximum machined O.D. and the minimum machined I.D. as applied to tubular parts. Finish machine size represents the size or the part as it comes form the final machining operation. From this size the tube mill can calculate a tube size which will be guaranteed to cleanup upon machining.
Flame HardeningA process of heating the surface layer of an iron-base alloy above the transformation temperature range by means of the flame of a high temperature torch, followed by quenching.
Flanged EndIn a flanged end the tube has been belled or expanded and a flange turned over until the wall of the tube end is at right angles to the wall of the tube.
Flash Removed-See Electric Resistance Welded Tubing.
Flash-In TubingSee Electric Resistance Welded Tubing.
Flux Leakage TestNon-destructive test which uses magnetic lines of force to recognize any discontinuity in the test piece.
ForgingUsed as a general term to describe the rolling, pressing, or hammering of steel which displaces the metal under compression by a locally applied force, usually at hot working temperatures.
Fracture StrengthAs 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.
Full AnnealSee Heat Treatment.



GaugesA measurement of thickness. There are various standard gages such as United States Standard Gage (USS), Galvanized Sheet Gage (GSG), Birmingham Wire Gage (BWG).
Grain SizeA measure of the size of individual metallic crystals usually expressed as an average. Grain size is reported as a number in accordance with procedures described in ASTM Grain size specifications.
Grain Size - Apparent FerriteApparent Ferrite Grain Size is average of the size of the ferrite grains as microscopically viewed in the normalized or annealed condition.
Grain Size - AusteniticAustenitic Grain Size, which is usually measurement by the McQuaid-Ehn method, represents the austenitic grain size of a material at a prescribed temperature above the upper critical, frequeintly 1700F. For austenitic stainless steels the grain size does not change upon cooling and is that observed microscopically at room temperature.



HardenabilityThe property in steel that determines the depth and distribution of hardness induced by cooling from a suitable elevated temperature. The hardness can vary with the cooling rate.
HardnessA measure of the degree of a materials resistance to indentation. It is usually determined by measuring resistance to penetration, by such tests as Brinell, Rockwell, and Vickers.
Heat TreatmentA 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. See various types below.
Heat Treatment - Age HardeningAge Hardening - Hardening by aging, usually after rapid cooling or cold working. Hardening is a result of a precipitation process, often submicroscopic, 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)
Heat Treatment - Air HardeningAir 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.
Heat Treatment - Air HardeningAir 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.
Heat Treatment - Air HardeningAir 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.
Heat Treatment - AnnealingAnnealing - Annealing is a heat treatment process which usually involves a relatively slow cooling after holding the material for some time at the annealing temperature. The purpose of the annealing treatment may include the following: (a) to induce softness: (b) to remove internal stresses: (c) to refine the grain size: (d) to modify physical and/or mechanical properties: (e) to produce a definite microstructure: (f) to improve machinability. It is generally desirable to use more specific terms in describing the heat treatment to be used, e.g., finish anneal, full anneal, or medium anneal, as applicable.
Heat Treatment - Bright AnnealBright Anneal - Carried out in a controlled furnace atmosphere, so that surface oxidation is reduced to a minimum and the tube surface remains relatively bright.
Heat Treatment - Dead SoftA heat treatment applied to achieve maximum softness and ductility
Heat Treatment - DrawingDrawing - Synonymous with TEMPERING, which is preferable.
Heat Treatment - Finish AnnealFinish Anneal - Heating of cold-worked tubing to a temperature below the lower critical, usually 950F. Generally this treatment will relieve peak stresses without altering hardness to any extent.
Heat Treatment - Full AnnealFull Anneal - Heating to a temperature above the upper critical and slow cooling below the lower critical.
Heat Treatment - IsothermalIsothermal Anneal - Austenitizing a heat treatable alloy and cooling to and holding within the range of temperature at which austenite transforms to a relatively soft ferrite-carbide aggregate.
Heat Treatment - Medium AnnealMedium Anneal - Subjecting tubing to a subcritical temperature to obtain specific mechanical properties.
Heat Treatment - NormalizeNormalize - Normalizing is a process which consists of heating to a temperature approximately 100F above the upper critical temperature and cooling in still air.
Heat Treatment - QuenchingQuenching - A process of rapid cooling from an elevated temperature, by contact with liquids or gases.
Heat Treatment - Soft AnnealSoft Anneal - A high temperature stress relieving anneal usually preformed in the temperature range of 1250 to 1350F. This anneal reduces hardness and strength of a cold worked steel to achieve near maximum softness.
Heat Treatment - Solution AnnealSolution Anneal - Heating steel into a temperature range wherein certain elements or compounds 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.
Heat Treatment - Spheroidizing AnnealSpheroidizing Anneal - A general term which refers to heat treatments that promote spheroidal or globular forms of carbide in carbon or alloy steels.
Heat Treatment - Stabilizing AnnealStabilizing 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 the areas adjacent to the carbides (usually grain boundaries). This treatment is intended to lessen the chance of intergranular corrosion.
Heat Treatment - Stress RelievingStress Relieving - A heat treatment which reduces internal residual stresses that have been induced in metals by casting, quenching, welding, cold working, etc. The metal is soaked at a suitable temperature for a sufficient time to allow readjustment of stresses. The temperature of stress relieving is always below the transformation range. Finish anneal, medium anneal, and soft anneal (sub-critical) describe specific types of stress relief anneals.
Heat Treatment - TemperingTempering - Reheating quenched or normalized steel to a temperature below the transformation range (lower critical) followed by any desired rate of cooling.
Hot Finished Seamless TubingTubing produced by rotary piercing, extrusion, and other hot working processes without subsequent cold finishing operations.
Hot Rolled ERW TubingAs welded electric resistance welded tubing made from hot rolled strip, sheet, or bands.
Hot Shortness (Red Shortness)A condition encountered in some metals wherein ductility is lessened at hot working temperatures.
Hot WorkingThe mechanical working of metal above the recrystallization temperature.
Huey TestA corrosion test for stainless steels. The weight loss per unit area is measured after each of five 48-hour boils in 65% nitric acid. The test results are calculated to and reported as the average corrosion rate of the five boils in inches per month (imp) corrosion rates. The test is used to determine the suitability of a material for nitric acid service. Since most of the weight loss is due to intergranular attack, the Huey test can be used as an indication of the resistance of a stainless steel to intergranular corrosion.
Hydrostatic TestA test in which a liquid, usually water, under pressure, is used internally to detect and locate leaks in a tube of a fabricated structure.



Impact TestingThere are several methods of determining the toughness of a steel, but the Izod and Charpy notched-bar tests are used quite widely. In both tests, the samples are cooled or heated to the desired test temperature, then struck once with a pendulum which fractures the specimen. The energy required to fracture the specimen, the impact strength, is measured in foot-pounds.
InclusionsParticles of nonmetallic impurities, usually oxides, sulfides, silicates, which are mechanically held in metals and alloys during solidification.
Induction HeatingA process of heating by electrical induction.
IngotA cast metal shape suitable for subsequent rolling or forging.
Ingot MoldA mold in which ingots are cast. Molds may be circular, square, or rectangular in shape, with walls of various thicknesses. Some molds are of larger cross section at the bottom: others are larger at the top.
Integral Finned TubingTubing with raised surface fins formed from the wall of the tube itself.
Intergranular CorrosionA 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 SoundnessRefers to condition of inside of material lack of defects, pipe, segregation, non-uniformity of composition.
Isothermal AnnealSee Heat Treatment.
Izod Impact TestSee Impact Strength Testing.



Jominy TestHardenability test performed usually on alloy steels to determine depth and degree of hardness resulting form a standard end quenching method with cold water.



Killed SteelSteel deoxidized with an agent such as silicon or aluminum to reduce the free oxygen content so that no harmful reaction occurs between carbon and oxygen during solidification.



LadleA large vessel into which molten steel or molten slag is received and handled.
Ladle AnalysisChemical analysis obtained form a sample taken during the pouring of the steel.
LaminationsDefects resulting form the presence of blisters, seams, or foreign inclusions aligned parallel to the worked surface of a metal.
LapA surface defect caused from folding the surface of an ingot, bloom, or bar during hot rolling operations and then rolling or forging the fold into the surface.



MachinabilityA measure of the relative ease with which steel may be machined.
MachiningThe deliberate removal of metal by one or more of several processes.
MacroetchA testing procedure for locating and identifying porosity, pipes, bursts, unsoundness, inclusions, segregations, carburization, flow lines from hot working, etc. Surface of the test piece should be reasonably smooth or even polished. After applying a suitable etching solution, the structure developed by the action of the reagent may be observed without a microscope.
Magnaflux TestThis test is conducted by suitably magnetizing the material and applying a prepared wet or dry magnetic power or fluid which adheres to it along lines of flux leakage. It shows the existence of surface and slightly subsurface non-uniformities.
MalleabilityThe property that determines the ease of deforming a metal when the material is subjected to rolling or hammering. The more malleable metals can be hammered or rolled into thin sheet more easily than others.
Mandrel(1) A device used to retain the cavity in hollow metal products during workout. (2) A metal bar around which other metal may be cast, bent, formed, or shaped.
MaragingA process of improving the mechanical strength of certain ferrous alloys. The name was derived from two hardening reactions: martensite and aging. The maraging strengthening mechanism is based on the age hardening (precipitation hardening) of extra-low carbon martensite.
MartensiteA constituent in quenched steel formed without diffusion and only during rapid cooling below the martensitic start (Ms) temperature. Martensite is the hardest of the transformation products of austenite.
McQuaid-Ehn TestA special test for revealing the austenitic grain size of ferretic steels when the steel is heated to 1700F and carburized. There are eight standard McQuaid-Ehn grain sizes - sizes 5 to 8 are considered fine grain and sizes under 5 are considered coarse grain.
Mechanical PropertiesThose properties of a material that reveal the elastic and in-elastic reaction when force is applied, or that involve the relationship between stress and strain for example, the modulus of elasticity hardness, tensile strength and fatigue limit. These properties have often been referred to as physical properties, but the term mechanical properties is correct.
Mechanical TubingUsed for a variety of mechanical and structural purposes, as opposed to pressure tubing, which is used to contain or conduct fluids or gases under pressure. It may be hot finished or cold drawn. It is commonly manufactured to consumer specifications covering chemical analysis and mechanical properties.
MetallographyThe 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, optical microscope, electron microscope and diffraction or X-ray techniques.
Metric System of MeasurementsIn the metric system of measurements, the principal unit for length is the meter: the principal unit for volume, the liter: and the principal unit for weight, the gram. The following prefixes are used for sub-divisions and multiples: milli = 1/1000: centi = 1/100: deci = 1/10: deca 10: hecto = 100: kilo = 1000. In abbreviations, the sub-divisions are frequently used with a smaller letter and the multiples with a capital letter, although this practice is not universally followed everywhere the metric system is used. All the multiples and the sub-divisions are not used commercially. Those ordinarily used for length are kilometer, meter, centimeter, and millimeter: for area square meter, square centimeter, and square millimeter: for volume, cubic meters, cubic decimeter (liter), cubic centimeter, and cubic millimeter. The most commonly used weights are the kilogram and gram. The metric system was legalized in the United States by an Act of Congress in 1866.
Micro-EtchMicro-etching is used for the examination of a sample under a microscope. Etching solutions tend to reveal structural details because of preferential chemical attack on the polished surface.
MicrocleanlinessRefers to the extent or quality of nonmetallic inclusions observed by examination under a microscope.
Minimum WallAny wall having tolerances specified all on the plus side.
Modulus of ElasticityThe ratio of stress applied to a material and the resulting strain occurring at the stresses below the elastic limit.



NitridingA process of case hardening in which a ferrous alloy, usually of special composition, is heated in an atmosphere of cracked ammonia or in contact with nitrogenous material to produce surface hardening without quenching by the absorption of nitrogen. Nitriding is normally conducted in a range from 900 to 1000F.
Non-Destructive TestingMethods of detecting defects without destroying or permanently changing the material being tested. Test methods include ultrasonic, eddy current, flux leakage, magnetic particle, liquid, penetrant, and X-ray.
Notch BrittlenessSusceptibility of a material to brittle fracture at points of stress concentration.
Notch SensitivityA measure of the reduction in strength of a metal caused by the presence of stress concentration.



OvalityThe difference between the maximum and minimum outside diameters of any one cross section of a tube. It is a measure of deviation from roundness.
Oxalic Acid Etch TestA quick metallographic test which is sometimes used to screen stainless steels before intergranular corrosion testing. This test is specified with a referee test such as the Copper-Copper Sulfate or Huey test.
OxidationIn its simplest terms, oxidation means the combination of any substance with oxygen. Scale developed during heat treatment is a form of oxidation.
OxideA compound consisting of oxygen and one or more metallic elements.



PassivateThe changing of the chemically active surface of a metal to a much less active state by the application of the proper chemical treatment or by applying an induced electrical current and voltage for cathodic or anodic protection form corrosion. An example of chemically passivating stainless steel would be to immerse stainless in a hot solution of approximately 10 to 20 percent by volume nitric acid and water.
PhotomicrographA photographic reproduction of an object magnified more than ten times used to show microstructure characteristics of steel.
Physical PropertiesThose properties not specifically related to reaction to external forces. These include such properties as density, electrical resistance, co-efficient of thermal conductivity.
PicklingUse of solutions, usually acids, to remove surface oxides form a tube, may also be used to produce a desired surface finish.
PiercingA seamless tubemaking method in which a hot billet is gripped and rotated by rolls or cones and directed over a piercer point is held on the end of a mandrel bar.
PitA sharp, usually small, depression in the surface of metal.
PorosityUnsoundness caused in cast metals by the presence of blowholes or shrinkage cavities.
Pressure TubingTubing produced for the purpose of containing or conducting fluids or gases under pressure.
ProfilometerAn instrument used for measuring surface finish. The vertical movements of a stylus as it traverses the surfaces are amplified electromagnetically and recorded (or indicated) as the surface roughness.
Proof StressThe load per square inch of the original cross-sectional area which, when removed, has caused a permanent elongation not exceeding a defined amount (usually 0.0001 per inch of gage length). A test of this type is more commonly used in Europe than in this country, where it largely has been replaced by yield strength measurements.
PyrometerAn instrument of any of various types used for measuring temperatures.



QuenchingSee Heat Treatment.



Random LengthTubing produced to a permissible variation in length. (Frequently seven feet.)
RecrystallizationThe reversion of distorted cold worked microstructure to a new, strain-free structure during annealing.
Reduction of AreaA measure of ductility determined in a tensile test. It is the maximum reduction, at the fracture, of the cross section area of a specimen, as compared with its original cross section area.
Rimmed SteelA steel which forms a relatively clean outer layer (rim) during solidification. Sheet and strip made from such steel has good surface quality and is frequently used for ERW tubing.
Rockwell HardnessSee Hardness.
Roto-Rock (Tube Reducing or Rockrite)A method of cold finishing tubing in which a machine rolls or rocks a split die over a tube. The tube is supported on the inside by a tapered mandrel.



ScaleAn oxide of iron which forms on the surface of hot steel.
SeamA tight, but unwelded imperfection on the surface of a wrought metal product.
SegregationNonuniform distribution of alloying elements, impurities, or microphases.
Semi-Killed SteelSteel that is incompletely deoxidized to permit the evolution of carbon monoxide, thereby offsetting solidification shrinkage.
SensitizationSensitization of stainless steel is defined as a susceptibility of preferential grain boundary attack. Material which exhibits grain boundary carbide precipitation may or may not be sensitized.
SoakTo hold an ingot, slab, bloom, billet, or other piece of steel in a hot furnace, pit, or chamber to secure uniform temperature.
Soaking PitA furnace or pit for the heating of ingots of steel to make their temperature uniform prior to rolling or forging.
Soft AnnealSee Heat Treatment.
SpecificationA 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.
Spheroidize AnnealSee Heat Treatment.
SpinningA 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, size, etc.
Stabilizing AnnealSee Heat Treatment.
Stress Corrosion CrackingCracking of metals under combined action of temperature, corrosion, and stress. The stress can be either applied or residual. Austenitic stainless steels are either applied or residual. Austenitic stainless steels are especially susceptible to cracking in chloride containing and some caustic environments.
Stress Relief AnnealSee Heat Treatment.
StripA flat-rolled steel product which serves as the raw material for welded tubing.
Sunk or Sink DrawnTubing drawn through a die with no inside mandrel to control I.D. or wall thickness.
SwagedA mechanical reduction of the cross sectional area of a metal, preformed hot or cold by forging, pressing, or hammering.



TappingThe act of pouring molten metal form a furnace into a ladle.
TeemingAct of pouring molten metal from a ladle into an ingot mold.
TemperingSee Heat Treatment.
Tensile StrengthThe maximum load per square inch of original cross-sectional area carried during a tension test to failure of the specimen. This test is preferred over the formerly-used ultimate strength.
Thermal ConductivityA measure of the ease with which heat is transmitted through a material.
TolerancePermissible variation.
TorsionA twisting action resulting in shear stresses and strains.
ToughnessA measure of ability to absorb energy and deform plastically before fracturing.
Transformation TemperatureThe temperature at which a change in phase occurs in steels. The term is sometimes used to denote the limiting temperature of a transformation range.
Transverse Tension TestA tension test for evaluating mechanical properties of a material in a direction transverse to that of rolling.
TurningA 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 StrengthSee tensile strength.
Ultrasonic TestingThe method of detecting defects in tubes or welds by passing high frequency sound waves into a material then monitoring and evaluating the reflected signals.
UpsettingA metal-working operation similar to forging, generally used to thicken the ends of tubes prior to threading.



Vickers Hardness TestSee Hardness.



WallWall Thickness or Gage. Specified in either fractions or decimals of an inch or by a wire gage number. In the United States, the most common gage used for tubing is the Birmingham iron wire gage, designated B.W.G..
Wall - AverageAverage Wall - A tube whose wall thickness is permitted to range over and under the specified nominal wall measurement within certain defined tolerances.
Wall - Maximum or MinimumMaximum and Minimum - The dimensions resulting after applying the proper tolerances to the nominal dimensions.
Wall - MinimumMinimum 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.
Wall - NominalNominal - The theoretical or stated value of the O.D., I.D., or wall dimension as specified by the customer.
Work HardeningHardness developed in metal as a result of cold working. See cold working.



Yield PointThe first stress in a material measured as load per unit of original cross-sectional area at which an increase in strain occurs without an increase in stress.
Yield StrengthThe stress at which a material exhibits a specified deviation from proportionality of stress and strain. An offset of 0.2% is most frequently used.