Welding Industry Terms and Definitions

Actual throat: The shortest distance between the weld root and the face of a fillet weld.

Air carbon arc cutting (CAC-A): A carbon arc cut-ting process variation that removes molten metal with a jet of air.

Arc blow: The deflection of an arc from its normal path because of magnetic forces.

Arc length: The distance from the tip of the welding electrode to the adjacent surface of the weld pool.

Arc strike: A discontinuity resulting from an arc, consisting of any localized re-melted metal, heat-affected metal,

or change in the surface profile of any metal object.

Arc welding (AW): A group of welding processes that produces coalescence of work pieces by heating them with

an arc. The processes are used with or without the application of pressure and with or without filler metal.

Autogenous weld: A fusion weld made without filler metal.

Back-gouging: The removal of weld metal and base metal from the weld root side of a welded joint to facilitate

complete fusion and complete joint penetration upon subsequent welding from that side.

Backing: A material or device placed against the back-side of the joint, or at both sides of a weld in welding, to

sup-port and retain molten weld metal.

Base metal: The metal or alloy that is welded or cut.

Bevel angle: The angle between the bevel of a joint member and a plane perpendicular to the surface of the

member.

Burn-through: A non-standard term for excessive visible root reinforcement in a joint welded from one side or a

hole through the root bead. Also, a common term used to reflect the act of penetrating a thin component with

the welding arc while hot tap welding or in-service welding.

Constant current power supply: An arc welding power source with a volt-ampere relationship yielding a small

welding current change from a large arc voltage change. (SMAW/GTAW)

Constant voltage power supply: An arc welding power source with a volt-ampere relationship yielding a large

welding current change from a small voltage change. (GMAW/FCAW)

Crack: A fracture type discontinuity characterized by a sharp tip and high ratio of length and width to opening displacement.

Defect: A discontinuity or discontinuities that by nature or accumulated effect (for example total crack length)

render a part or product unable to meet minimum applicable acceptance standards or specifications. The term

designates the state of being rejectable.

Direct current electrode negative (DCEN): The arrangement of direct current arc welding leads in which the

electrode is the negative pole and workpiece is the positive pole of the welding arc. Commonly known as straight

polarity.

Direct current electrode positive (DCEP): The arrangement of direct current arc welding leads in which the

electrode is the positive pole and the workpiece is the negative pole of the welding arc. Commonly known as

reverse polarity.

Discontinuity: An interruption of the typical structure of a material, such as a lack of homogeneity in its

mechanical, metallurgical, or physical characteristics. A dis-continuity is not necessarily a defect.

Distortion: The change in shape or dimensions, temporary or permanent, of a part as a result of heating or

welding.

Filler metal: The metal or alloy to be added in making a welded joint.

Fillet weld size: For equal leg fillet welds, the leg lengths of the largest isosceles right triangle that can be inscribed

within the fillet weld cross section.

Fusion line: A non-standard term for weld interface.

Groove angle: The total included angle of the groove between workpieces.

Heat affected zone (HAZ): The portion of the base metal whose mechanical properties or microstructure have

been altered by the heat of welding or thermal cutting.

Heat input: the energy supplied by the welding arc to the workpiece. Heat input is calculated as follows: heat

input = (V × i)/60v, where V = voltage, i = amperage, v =weld travel speed (in./min.)

Hot cracking: Cracking formed at temperatures near the completion of solidification.

Inclusion: Entrapped foreign solid material, such as slag, flux, tungsten, or oxide.

Incomplete fusion: A weld discontinuity in which complete coalescence did not occur between weld metal and

fusion faces or adjoining weld beads.

Incomplete joint penetration: A joint root condition in a groove weld in which weld metal does not extend

through the joint thickness.

Inspector: An individual who is qualified and certified to perform inspections under the proper inspection code or

who holds a valid and current National Board Commission.

Interpass temperature, welding: In multi-pass weld, the temperature of the weld area between weld passes.

IQI: Image quality indicator. “Penetrameter” is another common term for IQI.

Joint penetration: The distance the weld metal extends from the weld face into a joint, exclusive of weld

reinforcement.

Joint type: A weld joint classification based on five basic joint configurations such as a butt joint, corner joint, edge

joint, lap joint, and t-joint.

Lack of fusion (LOF): A non-standard term indicating a weld discontinuity in which fusion did not occur between

weld metal and fusion faces or adjoining weld beads.

Lamellar tear: A subsurface terrace and step-like crack in the base metal with a basic orientation parallel to the

wrought surface caused by tensile stresses in the through-thickness direction of the base metal weakened by the

presence of small dispersed, planar shaped, nonmetallic inclusions parallel to the metal surface.

Lamination: A type of discontinuity with separation or weakness generally aligned parallel to the worked surface

of a metal.

Linear discontinuity: A discontinuity with a length that is substantially greater than its width.

Longitudinal crack: A crack with its major axis orientation approximately parallel to the weld axis.

Nondestructive examination (NDE): The act of determining the suitability of some material or component for its

intended purpose using techniques that do not affect its serviceability.

Overlap: The protrusion of weld metal beyond the weld toe or weld root.

Oxyacetylene cutting (OFC-A): An oxygen gas cutting process variation that uses acetylene as the fuel gas.

PMI (Positive Materials Identification): Any physical evaluation or test of a material (electrode, wire, flux, weld

deposit, base metal, etc.), which has been or will be placed into service, to demonstrate it is consistent with the

selected or specified alloy material designated by the owner/user. These evaluations or tests may provide either

qualitative or quantitative information that is sufficient to verify the nominal alloy composition.

Peening: The mechanical working of metals using impact blows.

Penetrameter: Old terminology for IQI still in use today but not recognized by the codes and standards.

Porosity: Cavity-type discontinuities formed by gas entrapment during solidification or in thermal spray deposit.

Preheat: Metal temperature value achieved in a base metal or substrate prior to initiating the thermal operations.

Recordable indication: Recording on a data sheet of an indication or condition that does not necessarily exceed

the rejection criteria but in terms of code, contract or procedure will be documented.

Reportable indication: Recording on a data sheet of an indication that exceeds the reject flaw size criteria and

needs not only documentation, but also notification to the appropriate authority to be corrected. All reportable

indications are recordable indications but not vice-versa.

Root face: The portion of the groove face within the joint root.

Root opening: A separation at the joint root between the workpieces.

Shielding gas: Protective gas used to prevent or reduce atmospheric contamination.

Slag: A nonmetallic product resulting from the mutual dissolution of flux and nonmetallic impurities in some

welding and brazing processes.

Slag inclusion: A discontinuity consisting of slag entrapped in the weld metal or at the weld interface.

Spatter: The metal particles expelled during fusion welding that do not form a part of the weld.

Tack weld: A weld made to hold the parts of a weldment in proper alignment until the final welds are made.

Throat theoretical: The distance from the beginning of the joint root perpendicular to the hypotenuse of the

largest right triangle that can be inscribed within the cross-section of a fillet weld. This dimension is based on the

assumption that the root opening is equal to zero.

Transverse crack: A crack with its major axis oriented approximately perpendicular to the weld axis.

Travel angle: The angle less than 90 degrees between the electrode axis and a line perpendicular to the weld axis,

in a plane determined by the electrode axis and the weld axis.

Tungsten inclusion: A discontinuity consisting of tungsten entrapped in weld metal.

Undercut: A groove melted into the base metal adjacent to the weld toe or weld root and left unfilled by weld

metal.

Underfill: A condition in which the weld joint is incompletely filled when compared to the intended design.

Welder certification: Written verification that a welder has produced welds meeting a prescribed standard of

welder performance.

Welding: A joining process that produces coalescence of base metals by heating them to the welding

temperature, with or without the application of pressure or by the application of pressure alone, and with or

without the use of filler metal.

Welding engineer: An individual who holds an engineering degree and is knowledgeable and experienced in the

engineering disciplines associated with welding.

Weldment: An assembly whose component parts are joined by welding.

Weld joint: The junction of members or the edges of members which are to be joined or have been joined by

welding.

Weld reinforcement: Weld metal in excess of the quantity required to fill a joint.

Weld toe: The junction of the weld face and the base metal.