• 7/28/2019 Technical Terms for Tubing


    Technical Terms for

    TubingPlease note that the definitions below are provided for reference purposes only.

    Annealing - A general term referring to the thermal treatment process involvingheating and cooling, usually applied to change mechanical or physical properties,

    produce a desired microstructure.

    Annealing (Bright Annealing) - An annealing process usually carried out in a

    controlled atmosphere furnace using a reducing atmosphere to achieve desiredmechanical properties with minimum surface oxidation. The tube surface is

    relatively bright.

    Annealing (Normalizing) - An annealing process in which a steel is heated to a

    temperature that is above the upper transformation range and then cooled in air. A

    slight surface oxidation occurs during this process. The tube surface has a black orblue color.

    Annealing (Solution Annealing) - An annealing process in which stainless steel is

    heated to a suitable temperature to ensure the solution of constituents, such as

    chromium carbides, and cooled rapidly to hold these constituents in solution.

    Carbon Steel Tube - Steel tube containing only residual quantities of elements

    other than carbon and manganese. Typical industrial AISI designate grades

    include 1008, 1010, 1020, 1026, 1030, 1035 etc.

    Cold Drawing - The process of pulling a tube through a die and over a mandrel toreduce its diameter and/or wall thickness to a specific outside diameter, insidediameter or wall thickness. Higher tensile properties, tighter dementional

    tolerances, and improved surface finish are obtained due to the cold working at

    room temperature.

    Decarburization - The loss of carbon from the surface of ferrous alloy as a result

    of heating in a medium that reacts with the carbon.

    Dimensions of Tubing - A round tube section has three dimensions, any two of

    which may be measured. The three dimensions are outside diameter (OD), inside

    diameter (ID), and wall thickness (t or W).Nominalas applied to any of thesedimensions refers to the theoretical or stated single value of that dimension. The

    dimensions ordinarily specified by the customer are termed "nominal".Maximum

    and Minimum referring to the greatest and least values of any dimension.Averagedimensions are those secured by averaging a series of micrometer readings.

    Elongation - The amount of permanent extension in the vicinity of the fracture in

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    the tension test; usually expressed as a percentage of the original gauge length.

    Fatigue - The tendency for a metal to break at a point that is considerably below

    the ultimate tensile strength due to the conditions of repeated cyclic stressingconsiderably below the ultimate tensile strength.

    Formability - The ease with which a metal can be shaped through plastic

    deformation. Evaluation of the formability of a metal involves measurement of

    strength, ductility, and the amount of deformation required to cause fracture.

    Hardenability - In a ferrous alloy, the property that determines the depth and

    distribution of hardness induced by quenching.

    Hardness - Resistance of metal to plastic deformation. Various hardness tests such

    as Rockwell, Brinell, Vickers and Knoop may be used.

    Heat-Affected Zone (HAZ) - That portion of the base metal that was not meltedduring welding, but whose microstructure and mechanical properties were alteredby the heat.

    High-Strength Low-Alloy (HSLA) Steels - Steels designed to provide better

    mechanical properties and/or greater resistance to atmospheric corrosion than

    conventional carbon steels. They are not considered to be alloy steels in the

    normal sense because they are designed to meet specific mechanical propertiesrather than a chemical composition.

    Typical HSLA steels have minimum yield strengths 50 ksi, 60 ksi, 70 ksi or 80


    The chemical composition of the specific HSLA steel may vary for differentproduct thickness to meet mechanical property requirements. The HSLA steels

    have low carbon contents (0.05 to ~0.20% C) in order to produce adequate

    formability and weldability. Small quantities of chromium, nickel, molybdenum,copper, nitrogen, vanadium, niobium and titanium are used in various


    Impact Test - A test to determine the energy absorbed in fracturing a test bar at

    high velocity. The typical test for tubing is a notch test with an artificial notch

    present and tested at the various temperatures.

    Imperfection - When referring to the physical condition of a product, any

    departure of a quality characteristic from its intended level or state. When

    referring to the dimensional condition of a product, any dimensional characteristicthat is out of intended range. The existence of an imperfection does not imply

    nonconformance, nor does it have any implication as to the usability of a product

    in service. An imperfection should be rated on a scale of severity, in accordance

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    with applicable specifications, to establish whether or not the product is of

    acceptable quality.

    Inclusion - A physical and mechanical discontinuity occurring within a metal

    product, usually consisting of nonmetallic foreign material. Inclusions are often

    capable of transmitting some structural stresses and energy fields, but to anoticeably different degree than from the parent material. The foreign particles areusually compounds, such as oxides, sulfides, silicates or combination of these.

    Killed Steel - During the steel making process, the molten metal as it comes from

    the furnace contains more or less oxygen in the form of dissolved oxides, the

    amount varying with the composition desired and with certain conditions of steel

    making. If certain elements such as manganese, silicon or aluminum are added insufficient amounts to molten steel in the ladle, the metal will solidify quietly

    without evolution of gases. When processing rimmed steel and semi-killed steel,

    killed steel is one of the methods of deoxidizing. Killed steel is deoxidized with

    strong deoxidizing agent(s) to reduce the oxygen content to a minimum so that noreaction occurs between carbon and oxygen during solidification. Usually, killed

    steel has the best internal cleanliness condition.

    Mechanical Properties - The properties of a material that reveal its elastic and

    inelastic behavior when force is applied, thereby indicating its suitability for

    mechanical applications; for example tensile strength, yield strength, elongation,

    hardness, and fatigue limit.

    Physical Properties - Properties of a material that are relatively insensitive to

    structure and can be measured without the application of force; for example,

    density, electrical conductivity, coefficient of thermal expansion, magneticpermeability.

    Residual Stress - Macroscopic stresses that are set up within a metal as the result

    of non-uniform plastic deformation. This deformation may be caused by cold

    working or by drastic gradients of temperature from quenching or welding.

    Stainless - A trade name given to alloy steel that is corrosion and heat resistant.

    The chief alloying elements are chromium, nickel, molybdenum. By AISI

    definition, a steel is called "Stainless" when it contains 10.5 % or more chromium.

    Stress Relieving - A process of reducing residual stresses in a metal by heating thepart to a suitable temperature and holding for a sufficient time. This treatment

    may be applied to relieve stresses induced by cold working or welding.

    Tensile Strength - The value obtained by dividing the maximum load observed

    during tensile straining until breakage occurs by the specimen cross-sectional areabefore straining. Also called "ultimate strength".

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    Tubing - A non-standardized hollow shaped product with a relatively uniform

    wall thickness, generally round and manufactured to specified requirements or

    dimensions. Chemical composition, mechanical properties and othercharacteristics may be required for applications in automotive, mechanical,

    pressure or structural uses. It is generally specified to two dimensions, i.e., outside

    diameter (OD) and wall, inside diameter (ID) and wall, or OD and ID.

    Welding, Electric Resistance - The method of joining metals by passage of an

    electric current through the metal, whereby the resistance of the metal results in a

    temperature increase at the joining surfaces sufficient to weld. Upset pressure is

    also applied to insure sound contact of the surfaces to be welded.

    Welding, Induction - A form of electric resistance welding wherein the welding

    heat is generated within the metal by resistance to the flow of an electric current

    induced in the metal by means of a circumferential coil.

    Welding, Inert Arc - Arc welding in an atmosphere of an inert gas which serves toprotect the molten puddle from contamination and oxidation by preventing airfrom coming in contact with the metal while it is at elevated temperatures.

    Yield Strength - The stress at which a material exhibits a specified limiting

    deviation from proportionality of stress to strain. An offset of 0.2 %. is used for