Activation – The process of the passive surface of a metal to a chemically active state. Contrast with passivation.

Age Hardening – In a metal or alloy, a change in properties that generally occurs slowly at room temperature and more rapidly at higher temperatures, 500 – 900 °F. Hardness and strength are increased and ductility generally lowered. Usually follows cold working.

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 being hardened by cooling in air in fairly large sections, about 2 in. or more in diameter. Same as self-hardening steel.

Alloy Steel – Steel containing significant quantities of alloying elements (other than carbon and the commonly accepted amounts of manganese, silicon, sulpher and phosphorus) added to effect changes in the mechanical or physical properties.

Aluminum (Al) Melting point 660 °C (1220 °F)
It is the strongest de-oxidizer and combines with nitrogen, thus reducing the susceptibility to strain ageing. In small additions restrict grain growth. As Aluminum together with nitrogen nitride forms a high hardness, it is mostly an alloying element in nitriding steels. Aluminum improves the scale resistance and therefore often used as an alloying element in ferritic heat resisting steels. Because of the increase in the coarcivity is used as alloying element in Iron-Nickel Cobalt-Aluminum permanent magnet alloys.

Annealing – Heating to and holding at a suitable temperature an then cooling at a suitable rate, for such purposes as reducing hardness, improving machinability, facilitation 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, graphitising, intermediate annealing, isothermal annealing, malleablising, process annealing, quench annealing, recrystallisation annealing, and spheroidising. When applied to ferrous allows, the term ‘annealing’, without qualification, implies full annealing. When applied to nonferrous alloys, the term ‘annealing’ implies a heat treatment designed to soften a cold worked structure by recrystallisation or subsequent grain growth or to soften an age-hardened alloy by causing a nearly complete precipitation of the second phase in relatively coarse from. 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.

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.

Austenite – A solid solution of one or more elements in face-centered cubic iron.

Austenitising – Forming austenite by heating a ferrous alloy into the transformation range (partial austenitising) or above the transformation range (complete austenitising).

Average – Those dimensions obtained by averaging a number of measurements on a tube. For average wall pipe, the average wall is equal to the nominal wall.

Average Wall – A tube whose wall thickness is permitted to range over or under the specified nominal wall measurement within certain defined tolerances.

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Bend Radius – The inside radius of a bent section.

Bend Test – A test for determining relative 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 to 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 lined vessel so as to remove, by oxidation, most of the carbon, silicon and manganese.

Billet – A solid semi-finished round or square product that has been hot worked by forging, rolling or extrusion. An iron or steel billet has a minimum width or thickness of 1 ½ in. and the cross-sectional area varies from 21/4 to 36 sq. in. For nonferrous metals, it may also be a casting suitable for finished or semi-finished rolling or for extrusion.

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 forging.

Boron (B) Melting point 2040 °C (3704 °F)
Improves the deep hardening of constructional steels and produces therefore an increase in the core hardness of case hardening steels. With Boron austenitic 18/8 Chrome-Nickel steels can achieve higher elastic limits by the process of precipitation hardening, but the corrosion resistance is lowered. As Boron has a high neutron absorption cross-section, it is alloyed with steel for screening from nuclear installation.

Bright Annealing – Annealing in a protective medium to prevent discoloration of the bright surface.

Bright Drip – An acid solution into which articles are dipped to obtain a clean, 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.

Burning – (1) Permanently damaging a metal or alloy by heating to cause either incipient melting or inter-granular oxidation. See overheating. (2) In grinding 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 hardening metal balls.

Butt Welding – Joining two edges or ends by placing one against the other and welding them together.

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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.

Carbon (C)
Carbon is the foremost alloy element of steel and it has the farthest-reaching influence on it. In addition to carbon every unalloyed steel contains silicon, manganese, phosphorus and sulpher, which are introduced unintentionally during the manufacture. The addition of further alloy elements to produce specific, desired effects and the intentional increase of the contents of manganese and silicon gives rise to alloy steel. As the carbon content rises, the mechanical strength and the hardening properties of the steel improve, but its elasticity, forging, welding and cutting properties suffer. The carbon content has substantially no influence at all on the corrosion resistance to water, acids and hot gases.

Chromium (Cr) Melting point 1920 °C (3488 °F)
Increases the hardness and strength and only minimally reduces the elasticity. It improves the resistance to heat and non-scaling properties. With higher Chrome content the steels become corrosion resistant and with Carbon forms a high wear resisting Carbide. The welding properties deteriorate in pure Chromium steels with increasing Chromium content. Chromium is a strong Carbide former. The tensile strength of steel rises by 8 – 10 kg/mm2 per 1% Chromium. The yield point is likewise increased, however not at the same rate, but the notch impact value is lowered.

Cobalt (Co) Melting point 1492 °C (2718 °F)
Does not form carbide, it hinders the grain growth at higher temperatures and greatly improves the resistance to tempering and the hot tensile strength; it is therefore, often an alloy element of high-speed steel, hot work steels, heat resisting raw materials. It acts favorably on the graphitic formation, and greatly increases residual magnetism, coercive force, and thermal conductivity, therefore the alloy basis for high-grade permanent magnet steels and alloys. If subjected to neutron rays it forms a strong radioactive isotope Cobalt 60 for which reason it is undesirable in steels for atom reactors.

Columbium \ Niobium (Cb\Nb) Melting point 1950 °C (3542 °F)
Tantalum (Ta) Melting point 2977 °C (5391 °F)
These elements appear almost always together and are very difficult to separate from one another, so they are usually alloyed together, mainly as stabilizers.

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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.

Ductility – The ability of a material to deform to deform plastically without fracturing, being measured by elongation or reduction of area in a tensile test, by height cupping in an Erichsen test or by other means.

Dye Penetrant Inspection – Non-destructive inspection employing dye and sometimes black light to detect minute defects.

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Eccentricity – Variation of wall thickness in a given wall section.

Eddy-Current Testing – Nondestructive testing method in which eddy-current flow is inducted 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.

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.

Endurance Limit – Same as fatigue limit.

Etch Test – Exposure of a specimen to acid attack for the purpose of disclosing the presence of foreign matter of defects (segregation patterns or flow lines).

Extrusion – Production process in which steel is forced by compression through a die into solids (round or special shapes) or through a die and over a mandrel to form a tubular shape.

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Fatigue – The phenomenon leading to fracture under repeated or fluctuating stress 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.

Ferritic Stainless Steel – Ferritic stainless steels are divided into two classifications: hardenable and non-hardenable. When rapidly cooled from elevated temperatures, the non-hardenable grades (usually referred to as ferritic) have a ferritic microstructure. The hardenable grades will assume a martensitic microstructure when cooled quickly from elevated temperatures and are sometimes called martensitic stainless steels.

Fiber Stress – Local stress through small area (a point or line) on a section where the stress is not uniform, as in a beam under a bending load.

Finish – In the steel industry, 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 OD and the minimum machined ID as applied to tubular parts. Finish machine size represents the size of the part as it comes from the initial machining operation. From this size the tube mill can calculate a tube size which will be guaranteed to clean up upon machining.

Flame Annealing – Annealing in which the heat is applied directly by a flame.

Flame Hardening – A 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. This operation is followed by quenching.

Flanged End – In a flanged and tube, the tube wall has been belled or expanded until the wall of the tube end is at right angles with 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-in-Tubing – Welding which retains the bead or flash formed during welding.

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 arc between the members being welded.

Forging – Plastically deforming metal, usually hot, into desired shapes with compressive force, with or without dies.

Fracture Test – Breaking a specimen and examining the fractured surface with the unaided eye or with low-power microscope to determine such things as composition, grain size, case depth, soundness, or 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, sulpher or selenium to stainless steel.

Full Annealing – Annealing a ferrous alloy by austenitising and then cooling slowly through the transformation range.

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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.

Granular Fracture – A type of irregular surface produced when metal is broken, that is characterized by a rough, grain-like appearance as differentiated from a smooth silky, or fiber, type. It can be sub-classified into trans-granular and inter-granular forms. This type of fracture is frequently called crystalline fracture, but the inference that the metal has crystallized is not justified.

Grinding Cracks – Shallow cracks formed in the surface of relatively hard materials because of excessive grinding heat or the high sensitivity of the material.

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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 degree of resistance of a material to plastic deformation, usually determined by measuring resistance to penetration.

Heat-Affected Zone – That portion of the base metal which was not molted 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 work piece with an abrasive stick mounted in a holder.

Hot Finished Tubing – A product obtained by forging a hollow from a solid by means of rotary piercing, extruding centrifugal casting or other hot forming operations.

Hot Shortness – Brittleness in metal in the hot forming range.

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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 test.

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 – Steel formerly in a molten state, transferred to an ingot mould to solidify. After solidification, the resulting shape is called an ingot.

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Ladle – A large vessel into which molten metal or molten slag is received and handled. Molten metal may be transported short distances by carrying it in a ladle.

Ladle Analysis – The term applied to the chemical analysis representative of a heat or blow of steel and is the analysis reported to the purchaser. It is determined by analyzing (for such elements as have been specified) a test ingot sample obtained from various points of the heat or blow during the pouring of the steel from the ladle.

Longitudinal Direction – The principal direction of flow in a worked metal.

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Machinability – The relative ease of machining a metal.

Machining – In general, the cutting away of the surface of a metal by means of power driven machinery. Specifically, a method of conditioning steel by machining away the surface.

Macro-Etch – Etching of a metal surface fro 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.

Magnetic, Non-Magnetic – A material is magnetic when it is capable of being attracted by a magnet. Ferritic and martensitic stainless exhibit this capability, but in austenitic grades it is normally so low that they are considered non-magnetic.

Mandrel – (1) A rod used to retain the hollow cavity in metal products during working. (2) A metal bar around which other metals may be cast, bent, formed or shaped.

Manganese (Mn) Melting point 1244 °C (2271 °F)
Manganese improves the strength properties of steel, while only slightly impairing its elasticity: furthermore, manganese has a favorable influence on the forging and welding properties. A higher content of manganese in the presence of carbon increases the wear resistance very substantially. With up to 3% of Mn the tensile strength of the steels in increased by about 10 kg/mm2 for every percent of Mn; with contents above 3 to 8% the increase rises more slowly and at more than 8% of Mn it drops off again. The yield point behaves in a similar manner. Manganese increases substantially the depth of hardening.

Maximum and Minimum – the dimensions resulting after applying the proper tolerances to the nominal dimensions.

Mean – Intermediate between maximum and minimum actual dimensions.

Mechanical Properties – The properties of a material that reveal its elastic and inelastic behavior where force is applied, there by 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, which is used to contain or conduct fluids under pressure. It may be hot finished or cold drawn. It is commonly manufactured to consumer specifications covering chemical analysis, mechanical properties, and often to special dimensional tolerances.

Mechanical Working – Subjecting metal to pressure exerted by rolls, presses, hammers or dies to change its form, or to affect the structure and therefore the mechanical properties.

Metallurgy – The science which deals with the extraction of metals from their ores and the adaptation and application of the metals to the uses for which they are intended.

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 measurement.

Molybdenum (Mo) Melting point 2610 °C (4730 °F)
Molybdenum improves the tensile strength and especially the heat resistance and it has also a favorable influence on the welding properties. Steel with a higher Mo content tends to be difficult to forge. Molybdenum is frequently used in conjunction with chromium. The behavior of molybdenum resembles that of tungsten. When used in alloy steels in combination with chromium and nickel, molybdenum may produce high yield point and tensile strength values. Molybdenum has a strong tendency to form carbide and is the alloy element of choice in high speed and hot working steels, in austenitic corrosion-resistant steels, case hardening and heat-treating steels as well as in heat resistant steels, also in view of the diminuation to over-drawing brittleness

Multiple Lengths – A piece of length consisting of a combination of two or more unit lengths as designated by a customer.

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Nickel (Ni) Melting point 1453 °C (2809 °F)
Nickel raises the strength of steel less than does silicon or manganese, with the elasticity dropping only insignificantly. Ni ensures good through hardening, especially so when the steel contains also chromium. Chrome nickel steels are stainless and resistant to scaling and also heat resistant. Nickel does not impair the welding properties. Nickel increases the notch impact value of structural steels considerably, especially at low temperatures. In the sphere of steel alloying, nickel is especially suitable for use in austenitic steels, steels resistant to corrosion and scaling and in casehardening and heat-treating steels to improve their toughness.

Niobium/Columbium (Nb / Cb) Melting point 1950 °C (3542 °F)
Tantalum (Ta) Melting point 2977 °C (5391 °F)
These elements appear almost always together and are very difficult to separate from one another, so they are usually alloyed together, mainly as stabilizers.

Nitric Acid Test – A prolonged exposure of specimens to nitric acid under closely controlled conditions to determine relative resistance to attack by nitric acid in service. The tests give no information relevant to performance in contact with other corrosive media.

Nitrogen (N) Melting point –210 °C (-248 °F)
In austenitic steels, Nitrogen stabilizes the structure, increases the hardness and especially the yield point as well as the mechanical properties at high temperature. Nitrogen allows the achievement of high surface hardness through nitride formation during nitriding. Nitrogen is harmful because of ht lowering of toughness during the process of precipitation, the cause of age intensitivity and blue brittleness, as well as the possibility of releasing intergranular stress corrosion, in unalloyed steels.

Nominal – The Theoretical or stated value of the OD, ID or well dimension as specified by the customer.

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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-grained surface which develops in forming metals having course grains.

Ornamental Tubing – Tubing produced for an application in which it will not be subject to significant stresses of any kind. It is normally produced either with superior surface finish or with the capability of attaining superior finish in fabricating operation. This is usually stainless tubing.

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 a combination of working and heat-treating, the overheating is known as burning.

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Pass – The term given to a single passage of a tube or piece of steel though a roll stand or a drawing die.

Passivation – The changing of the chemically active surface of a metal to a much less reactive state. Contrast wit activation.

Physical Properties – The properties, other than mechanical properties, that pertain to the physics of a material; for example, density electrical conductivity, heat conductivity, thermal expansion.

Phosphorus (P) Melting point 44 °C (111 °F)
There are various kinds of phosphorous, viz white (yellow), red (purple), black phosphorus and others. Quite generally, phosphorus is considered to be detrimental to steel so that it is endeavored to keep the P content in high-grade steels at a maximum level of 0.03 to 0.05%.

Pickling – Removing surface oxides from metals by chemical or electrochemical reaction.

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.

Pitting – Forming small sharp cavities in a metal surface by non-uniform electro-deposition or by corrosion.

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 austenitising. For some nonferrous alloys, heating to a high temperature for a long time, in order to homogenize the structure before working.

Pressure Testing – Tubing produced for the purpose of containing or conducting liquids or gasses under pressure, or where subjected to external pressure.

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.

Proof Stress – The 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 gauge length). A test of this type is more commonly used in Europe than in the United States where it has been largely replaced by yield strength measurements.

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Quench Hardening – Hardening a ferrous alloy by austenitising and then cooling rapidly enough so that some or all of the austenite transforms to martensite.

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Recrystallisation – (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, stain-free grain structure from that existing in cold worked metal, usually accomplished by heating.

Recrystallisation Temperature – The approx. minimum temperature at which complete recrystallisation of a cold worked metal occurs within a specified time.

Reduction 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.

Rough Machining – Machining without regard to finish, usually to be followed by a subsequent operation.

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Scaling – Forming a thick layer of oxidation products on metals at high temperatures.

Secondary Hardening – Tempering certain alloy steels at certain temperatures so that the resulting hardness is greater that that obtained by tempering the same steel at some lower temperature for the same time.

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.

Silicon (Si) Melting point 1410 °C (2570 °F)
Like Manganese, Silicon is present in all steels since the iron ores used in their manufacture contain a varying amount of it. Further Silicon stemming from the refractory lining of the furnace is introduced into the melt during the manufacturing of steel. The term “Silicon Steels”, however, includes only steels having a Silicon content above 0.40% Si is not a metal but rather a so-called metalloid like, for example, phosphorus and sulpher. Silicon increases the mechanical strength, the resistance to scaling and the density; especially of cast steel. The elasticity is only insignificantly affected; while the tensile strength is increased by about 10 kg/mm2 for each percent of Si and the yield point is raised to a similar degree. Steel having a higher content of Silicon turns coarsely granular. A high silicon content, about 14%, enables steel to resist chemical attacks but it can no longer be forged.

Skelp – A plate of steel from which pipe is made. This is done by rolling the skelp longitudinally, into shape, and welding the edges together. Most commonly refers to furnace weld pipe than to electric weld pipe or tubing.

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 ally is left in a supersaturated, unstable state and may subsequently exhibit quench ageing.

Special Straightness – When material is desired to closer than standard straightness tolerances, it may be ordered to special straightness. Such straightening is done by machinery and may result in increased surface hardness in localized areas of the steel.

Specification – A document containing a number of designated measurements and/or tests to which tubing must conform for a specific requirement, such as length, I , D, OD, alloy content, tensile strength, etc.

Spot Welding – An electric resistance welding process in which the fusion is limited to a small area. The pieces being welded are pressed together between a pair of water-cooled electrodes through which an electrical current is passed during a very short interval so that fusion occurs over a small area at the interface between the pieces.

Stabilizing Treatment – Any treatment intended to stabilize the structure of an alloy or the dimensions of a part. (1) 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. (2) Transforming retained austenite in parts made from tool steel. (3) 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

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.

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 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-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’.

Strip - A flat rolled steel product which serves as the raw material for welded tubing. May be hot rolled or cold rolled.

Sulpher (S) Melting point 118 °C (244 °F)
Produces “red shortness”, makes steel brittle and is therefore harmful. Contents of 0.025% or 0.030% are permitted. Exceptions are the free machining steels to which is added up to 0.30% so that the small distributed sulphide inclusions disturb the metallic cohesion and therefore contribute to the formation of short turnings.

Sunk or Sink Drawn Tubing - Tubing drawn through a die with no inside mandrel to control I D or wall thickness. Only O D tolerance can be closely controlled.

Superficial Rockwell Hardness Test – Form of Rockwall hardness test using relatively light loads which produce minimum penetration. Used for determining surface hardness or hardness of thin section or small parts, or where large hardness impression might be harmful.

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Tack Welds – Small scattered wilds made to hold parts of a weldment in proper alignment while the final welds are being made.

Tantalum (Ta) Melting point 2977 °C (5391 °F)

Tapping – The act of draining molten metal from furnace to ladle.

Temper – (1) In heat treatment, reheating hardened steel or hardened cast iron to some temperature below the autoctoid 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 unadvisedly, 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 ort 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 though, 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.

Titanium (Ti) Melting point 1812 °C (3294 °F)
A very hard metal. Strong carbide former. Is an alloying element mainly in stainless steels for the stabilizing agent against intergranular corrosion; apart from this it has grain-refining properties.

Torsion – A twisting action resulting in shear 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 austenite forms during heating and transforms during cooling. The two ranges are distinct, sometimes overlapping but never coinciding. The two limiting temperatures of the ranges depend on the composition of the allow and on the rate of change of temperature, particularly during cooling.

Transverse – Literally ‘across’, usually signifying a direction or plane perpendicular to the direction of working.

Transverse Tension Test – A tension test for evaluating the mechanical properties of a material in a direction transverse to that of rolling. It is not generally applicable to tubular products except I very large sizes (8” OD and larger).

Trepanning – A type of boring where an annual cut is made into a solid material with the coincidental formation of a plug or solid cylinder.

Tungsten (Tu)
Wolfram (W) Melting point 3380 °C (6116 °F)
Tungsten improves the strength properties: It increases substantially the hardness and the life of cutting edges and is also responsible for high heat resistance values. Tungsten is therefore used as an alloy element for high speed and heat-treating steels. The tensile strength and yield point values of the steel are increased by about 4 kg/mm2 for every percent of Tu added. Tungsten has a very strong tendency to form carbide and is primarily used in heat resistant steels since it renders them resistant to over-drawing and heat.

Turning – A method for removing the surface from a circular work piece by bringing the cutting edge of a tool against it while the piece is rotated.

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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 15kc per sec.

Ultrasonic Testing – A method of detecting defects in tubes or welds by use of high frequency sound waves imparted by contact or immersion techniques.

Ultrasonic Waves – Waves of ultrasonic frequency. They include longitudinal, transverse, surface and standing waves.

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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.

Vanadium (V) Melting point 1730 °C (3146 °F)
A small addition improves the hot hardness and reduces the grain growth. Vanadium acts especially favorably in structural and tool steels. In high speed steel increases the cutting properties. Vanadium is a strong carbide former. Increases the tensile strength and yield point, especially however the hot hardness properties of the steels. Vanadium is preferred in combination with Chromium in structural and heat resisting steels and in combination with Tungsten in high-speed and hot work steels.

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Wall – Wall thickness or gauge. Specified in either fractions or decimals of an inch by a ‘wire gauge’ number. In the United States, the gauge used for tubing is the Birmingham Iron Gauge, designated “BWG’.

Welding – A process to join metals by the application of heat. Fusion welding, which includes gas, arc and resistance welding, requires that the parent metals be melted. This distinguishes fusion welding from brazing. In pressure welding, joining is accomplished by the use of heat and pressure without melting. The parts that are being welded are pressed together and heated simultaneously, so that recrystalisation occurs across the interface.

Wolfram (W) Melting point 3380 °C (6116 °F)
Tungsten (Tu)
Tungsten improves the strength properties: It increases substantially the hardness and the life of cutting edges and is also responsible for high heat resistance values. Tungsten is therefore used as an alloy element for high speed and heat-treating steels. The tensile strength and yield point values of the steel are increased by about 4 kg/mm2 for every percent of Tu added. Tungsten has a very strong tendency to form carbide and is primarily used in heat resistant steels since it renders them resistant to over-drawing and heat.

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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 yields 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.