Mechanical Engineering Dictionary-Welding Processes

Important Terms and their Meaning of Mechanical Engineering-Welding Processes:



ARC – A sustained electric discharge, where current flows through the gap between two electrodes.

ARC CUTTING – Process which melts the metals to cut with the heat of an arc between an electrode and the base metal.

ARC EYE – A burn on the exterior surface of the operators eye, due to its exposure to an open arc. Also called FLASH EYE.

ARC GAP – Distance between the tips of two electrodes, normally between an electrode and the workpiece. Also known as ARC LENGTH.

ARC PLASMA – A gas that has been heated to an at least partially ionized condition, enabling it to conduct an electric current.

ARC SPOT WELD – Spot welding made by an arc welding process.

ARC WELDING – A group of welding processes which produces coalescence of metals by heating them with an arc, with or without the application of pressure, and with or without the use of filler metal.

ATOMIC HYDROGEN WELDING – An arc welding process which produces coalescence of metals by heating them with an electric arc maintained between electrodes in an atmosphere of hydrogen. Shielding is provided by hydrogen.

AUTOGENOUS WELD – A fusion weld made without the addition of filler metal.

AUTOMATIC OXYGEN CUTTING – Cutting with an equipment without constant observation and adjustment of the controls by an operator.

AUTOMATIC WELDING – Welding which permits the operation without adjustment of controls by an operator.

BACKHAND WELDING – A welding technique in which the welding torch or gun is directed opposite to the progress of welding.

BACK WELD – A weld deposited at the back of a single groove weld.

BARE ELECTRODE – A filler metal electrode of a single metal or alloy, produced into a wire, strip or bar form and without any coating or covering on it.

BARE METAL ARC WELDING – Process which produces coalescence of metals by heating them with an electric arc between a bare or lightly coated metal electrode and the work piece.

BASE METAL – The metal to be welded, brazed, soldered or cut.

BLIND JOINT – A joint, no portion of which is visible.

BORAX – is the old standard flux for brazing, exists in two forms—ordinary borax and amorphous or fused borax.

BRAZING – A group of welding processes that produces coalescence of materials by heating them to the brazing temperature, using a filler metal having a liquidus above 450°C and below the solidus of the base metal.

BUTT JOINT – A joint between two members aligned approximately in the same plane.

CARBON ARC CUTTING – Cutting of base metals by melting them with the heat of an arc produced between a carbon electrode and the base metal.

CARBON ELECTRODE – A non-filler metal electrode used in arc welding or cutting, consisting of a carbon or graphite rod, which may be coated with copper or other coatings.

CARBON ARC WELDING – A brazing process that produces coalescence of metals by heating them with an electric arc produced between two carbon electrodes. The filler material is distributed in the joint by capillary action.

COLD WELDING – A solid state welding process in which pressure is applied at room temperature to produce coalescence of metals with substantial deformation at the weld.

COMPOSITE ELECTRODE – Multi component filler metal electrodes in various physical forms such as standard wires, tubes and covered wire.

CONTINUOUS WELD – A weld that extends continuously from one end of a joint to the other.

COVERED ELECTRODE – An electrode consisting of a core of a bare electrode or metal cored electrode to which a covering, sufficient to provide a slag layer on the weld metal, has been applied.

COVER PLATE (eye protection) – A removable pane of colourless glass, plastic coated glass or plastic that covers the filter plate and protects it from weld spatter, pitting or scratching when used in a helmet, hood or goggles.

CRATER – A depression at the termination of a weld bead.

DECARBURIZING FLAME – A flame which removes carbon from the molten metal.

DEPOSITION EFFICIENCY (arc welding) – Ratio of the weight of deposited metal to the net weight of the filler metal consumed, exclusive of stubs i.e., left out electrode bits.

DEPTH OF FUSION – Distance that fusion extends into the base metal or previous pass from the surface melted during welding.

DIFFUSION WELDING – A solid state welding process that produces coalescence of the faying surfaces by the application of pressure at elevated temperature.

EDGE JOINT – A joint between the edges of two or more parallel or nearly parallel members.

ELECTROGAS WELDING – Arc welding in which coalescence is affected by heating the metals with an arc produced between a continuous filler metal electrode and the work. Shielding is by inert gas.

ELECTRO SLAG WELDING – A welding process producing coalescence of metals with molten slag that melts the filler metal and the surfaces of the work-pieces. The weld pool is shielded by slag.

EMISSIVE ELECTRODE – A filler metal electrode consisting of a core of a bare electrode or a composite electrode to which a very light coating has been applied to produce a stable arc.

EXPLOSION WELDING – A solid state welding process in which coalescence is affected by high velocity movement of the work-pieces, produced by a controlled detonation.

FACE SHIELD (eye protection) – Device positioned in front of the eyes and over all or a portion of the face to protect the eyes and face.

FILLET WELD – A weld of approximately triangular cross-section joining two surfaces approximately at right-angles to each other in a lap joint, T joint or corner joint.

FILLER METAL – Metal to be added in making a welded, brazed or soldered joint.

FIRE CRACKER WELDING – Shielded metal arc welding process in which a length of covered electrode is placed along the joint in contact with the work-pieces. During welding, a stationary electrode is consumed as the arc travels the length of the electrode.

FISH EYE – A discontinuity found on the fracture surface of a weld in steel. It consists of a small pore or inclusion surrounded by an approximately round bright area.

FLOW WELDING – Process which produces coalescence of metals by heating them with molten filler metal poured over the surfaces to be welded until the welding temperature is attained and until sufficient filler metal has been added.

FLUX – Material used in welding to prevent, dissolve or facilitate removal of oxides and other undesirable surface substances.

FLUX CORED ARC WELDING – Process in which coalescence of metals is effected by heating them with an arc between a continuous filler metal (consumable) electrode and the work. Shielding is by the flux contained within the tubular electrode.

FLUX CORED ELECTRODE – A composite hollow filler metal electrode containing within it ingredients to provide such functions as shielding atmosphere, deoxidation, arc stabilization and slag formation.

FOREHAND WELDING – A welding technique in which the welding torch or gun is directed toward the progress of welding.

FORGE WELDING – Process that produces coalescence of metals by heating them in air in a forge and by applying pressure or blows sufficient to cause permanent deformation at the surface.

FUSION – Melting together of filler metal and base metal (substrate) or of base metal only which results in coalescence.

FUSION WELDING – Arc welding process that uses fusion of the base metal to make the weld.

FUSION ZONE – Area of base metal melted as determined on the cross-section of a weld.

GAS METAL ARC CUTTING – Process in which metals are severed by melting them with the heat of an arc produced between a continuous filler metal electrode and the workpiece. Shielding is obtained entirely from an externally supplied gas.

GAS CARBON ARC WELDING – Process which produces coalescence of metals by heating them with an electric arc between a carbon electrode and the workpiece. Shielding is effected by a gas or gas mixture.

GAS METAL ARC WELDING – Process that produces coalescence of metals by heating them with an arc between a continuous filler metal electrode and the workpiece. Shielding is obtained by external gas supply.

GAS REGULATOR – A device for controlling the delivery of gas at some substantially constant pressure.

GAS TUNGSTEN ARC CUTTING – Process in which materials are severed by melting them with an arc produced by a tungsten electrode and the workpiece. Shielding is effected by a gas.

GAS TUNGSTEN ARC WELDING – Process that produces coalescence of metals by heating them with an arc produced between a tungsten (non-consumable) electrode and the workpiece. Shielding is obtained from a gas.

GAS WELDING – Process in which heat is furnished by a flame resulting from the combustion of a fuel gas, such as acetylene or hydrogen with oxygen; oxyacetylene being capable of producing the highest temperature flame is the most used.

GLOBULAR TRANSFER – Transfer of molten metal in large drops from a consumable electrode across the arc in arc welding.

GOUGING – The forming of a bevel or groove by material removal.

HAND SHIELD – A protective device, used in arc welding, for shielding the eyes, face and neck. A hand shield is equipped with a suitable filter plate and is designed to be held by hand.

HEAT AFFECTED ZONE – The portion of the base metal that has not been melted, but whose mechanical properties or microstructure have been altered by the heat of welding, brazing, soldering or cutting.

HELMET (eye protection) – Device designed to be worn on the head to protect eyes, face and neck from arc radiation, radiated heat, spatter, or other harmful matter expelled during arc welding.

HOT PRESSURE WELDING – Process that produces coalescence of metals with heat and application of pressure sufficient to produce macro-deformation of the base metal. Vacuum or other shielding media is used.

HOTWIRE WELDING – Arc welding process in which a filler metal wire is resistance heated by current flowing through the wire as it is fed into the weld pool.

INERT GAS – A gas which does not normally combine chemically with the base metal or filler metal.

INTERMITTENT WELD – A weld in which the continuity is broken by recurring unwelded spaces.

JOINT – Junction of members or the edges of members which are to be joined or have been joined.

JOINT EFFICIENCY – The ratio of the strength of a joint to the strength of the base metal expressed in per cent.

KERF – Width of the cut produced during a cutting process.

LAP JOINT – A joint formed between two overlapping members in parallel planes.

LASER BEAM CUTTING – Process that severs materials by melting or vaporizing them with the heat obtained from a laser beam, with or without the application of gas jets to augment the removal of material.

LASER BEAM WELDING – Process that produces coalescence of materials with the heat obtained from the application of a concentrated coherent light beam impinging upon the joint.

LIGHTLY COATED ELECTRODE – A filler metal electrode consisting of a metal wire with light coating applied subsequent to the drawing operation, primarily for stabilizing the arc.

MACHINE OXYGEN CUTTING – Cutting with an equipment that performs the operation under the constant observation and control of an oxygen cutting operator.

MACHINE WELDING – Welding with an equipment which performs the operation under the constant observation and control of a welding operator.

MANUAL WELDING – Welding performed and controlled completely by hand.

MELTING POINT – The temperature at which a metal melts.

MELTING RANGE – Temperature range between solidus and liquidus.

MELTING RATE – The weight or length of electrode melted in unit time.

METAL ARC CUTTING – Processes that sever metals by melting them with the heat of an arc between a metal electrode and the base metal.

METAL BATH BRAZING – is a dip process wherein the filler metal is obtained from the molten metal bath. This is confined to joining comparatively small work such as joints in wire.

METAL CORED ELECTRODE – A composite filler metal electrode consisting of a metal tube or other hollow configuration containing alloying ingredients.

METAL ELECTRODE – A filler or non-filler metal wire or rod, either bare or covered, used in an arc welding or cutting.

METAL POWDER CUTTING – An oxygen cutting process that severs metals through the use of powder such as iron, to facilitate cutting.

NEUTRAL FLAME – An oxyfuel gas flame in which the proportion used is neither oxidizing nor reducing.

NON-DESTRUCTIVE TESTING – Testing of welds or metal without causing any damage to the item being tested.

OVER WELDING – Depositing more filler metal than required.

OXYACETYLENE CUTTING – Process that severs metals by the chemical reaction of oxygen with the base metal at elevated temperatures caused by combustion of acetylene with oxygen.

OXYACETYLENE WELDING – Process that produces coalescence of metals by heating them with the flame obtained by combustion of acetylene with oxygen.

OXY FUEL CUTTING – A group of cutting processes used to sever metals by means of the chemical reaction of oxygen with the base metal at elevated temperatures produced by flames obtained from combustion of fuel gas and oxygen e.g., oxy hydrogen cutting, oxy natural gas cutting, oxy propane cutting.

OXY FUEL GAS WELDING – A group of welding processes that produces coalescence by heating materials with an oxyfuel gas flame or flames with or without the application of pressure and with or without the use of filler metal e.g., oxy hydrogen welding.

OXYGEN LANCE CUTTING – An oxygen cutting process used to sever metals with oxygen supplied through a consumable lance. The preheat to start cutting is obtained by other means.

PLASMA ARC CUTTING – Process that severs metal by melting a localized area with a constricted arc and removing the molten material with high velocity jet of hot, ionized gas issuing from the constricted orifice.

PLASMA ARC WELDING – Process that produces coalescence of metals by heating them with a constricted arc between an electrode and the workpiece (transferred arc) or the electrode and the constricting nozzle (non-transferred arc). Shielding is obtained from the hot ionized gas issuing from the orifice which may be supplemented by an auxiliary source of shielding gas.

PLUG WELD – A weld made in a circular hole or one member of a joint, fusing that member to another member.

POROSITY – Cavity type discontinuities formed by gas entrapment during solidification.

POST HEATING – Application of heat to an assembly after a welding, brazing, soldering, thermal spraying or thermal cutting.

PRE HEATING – Application of heat to the base metal immediately before welding, brazing, soldering, thermal spraying and cutting.

PRESSURE GAS WELDING – An oxyfuel gas welding which produces coalescence simultaneously over the entire area of faying surfaces by heating them with gas flames obtained from combustion of a fuel gas with oxygen and by the application of pressure, without the use of filler metal.

PROJECTION WELDING – is a modification of spot welding in which the current and pressure are localized at the weld section by the use of embossed, machined, or coined projections on one or both pieces of the work.

PROTECTIVE ATMOSPHERE – Gas or vacuum envelope surrounding the work-pieces used to prevent or facilitate removal of oxides and detriment surface substances.

RANDOM INTERMITTENT WELDS – Intermittent welds on one or both sides of a joint in which the weld increments are made without regard to spacing.

PULSED POWER WELDING – An arc welding process variation in which the power is cyclically programmed to pulse so that effective but short duration values of a parameter can be utilized. Also called PULSED VOLTAGE or PULSED CURRENT WELDING e.g., gas metal arc welding (pulsed arc), gas tungsten arc welding (pulsed arc).

REDUCING ATMOSPHERE – A chemically active protective atmosphere which at elevated temperature will reduce metal oxides to their metallic state.

REDUCING FLAME – A gas flame having a reducing effect owing to excess fuel gas.

RESIDUAL STRESS – Stress present in a member that is free to external forces or thermal gradients.

RESISTANCE BRAZING – is an electric brazing process wherein the heat is obtained by passing an electric current through the parts being brazed.

RESISTANCE WELDING – In this, the metal parts to be joined are heated by their resistance to the flow of an electric current e.g., spot welding, seam welding.

ROLL WELDING – A solid state welding process that produces coalescence of metals by heating and by applying pressure with rolls sufficient to cause deformation at the faying surfaces.

SEAL WELD – Any weld designed primarily to provide a specific degree of tightness against leakage.

SEAM WELD – A continuous weld between or upon overlapping members, in which coalescence may start and occur on the faying surfaces, or may have proceeded from the outer surface of one member.

SEMI AUTOMATIC ARC WELDING – Arc welding with equipment that controls only the filler metal feed. The advance of the welding is manually controlled.

SEMI BLIND JOINT – A joint in which one extremity of the joint is not visible.

SERIES SUBMERGED ARC WELDING – A submerged arc welding process variation in which electric current is established between two consumable electrodes which meet just above the surface of the work-pieces which are not part of the electric circuit.

SHIELDED CARBON ARC WELDING – A carbon arc welding process in which shielding is effected by the combustion of a solid material fed into the arc or from a blanket of flux on the work-pieces or both.

SHIELDED METAL ARC CUTTING/WELDING – Cutting or welding effected by heating the work-pieces with an arc between a covered metal electrode and the workpiece. Shielding is obtained from decomposition of the electrode covering,

SHIELDING GAS – Protective gas used to prevent atmospheric contamination.

SHORT CIRCUITING TRANSFER ARC WELDING – Metal transfer in which molten metal from a consumable electrode is deposited during repeated short circuits.

SHRINKAGE VOID – A cavity type discontinuity normally formed by shrinkage during solidification.

SILVER BRAZING – Brazing process that employs silver alloys. Also called hard soldering or silver soldering.

SLAG INCLUSION – Non-metallic material entrapped in weld metal or between weld metal and base metal.

SLOT WELD – A weld made in an elongated hole in one member of a joint fusing that member to another member. The hole may be open at one end.

SOLDER – A filler metal used in soldering which has a liquidus not exceeding 450°C.

SOLDERING – A group of welding processes that produces coalescence of materials by heating them to a suitable temperature and by using a filler metal having a liquidus not exceeding 450°C and below the solidus of the base metals.

SOLID STATE WELDING – A group of welding processes that produces coalescence at temperatures essentially below the melting point of the base metal being joined, without the addition of a brazing filler metal. Pressure may or may not be used.

SPATTER – The metal particles expelled during fusion welding, that do not form a part of the weld.

SPELTER – is common brass, the first material used to make a brazed joint in ferrous material.

SPOT WELD – Weld made between or upon overlapping members in which coalescence may start and occur on the faying surfaces or may proceed from the surface of one member. The weld cross section (plan) is approximately circular.

SPRAY TRANSFER ARC WELDING – Metal transfer in which molten metal from a consumable electrode is propelled axially across the arc in small droplets.

STACK CUTTING – Thermal cutting of stacked metal plates arranged so that all the plates are severed by a single cut.

STAGGERED INTERMITTENT WELD – An intermittent weld on both sides of a joint in which the weld increments on one side are alternated with respect to those on the other side.

STRINGER BEAD – A type of weld bead made without appreciable weaving motion.

STUD WELDING – A general form for the joining of a metal stud or similar part to a workpiece. Welding may be effected by arc, resistance, friction or other suitable process, with or without external gas shielding.

SUBMERGED ARC WELDING – An arc welding process in which the arc and molten metal are shielded by a blanket of granular, fusible material on the work-pieces.

SURFACING – Application by welding, brazing or thermal spraying of a layer(s) of material to a surface to obtain desired properties or dimensions as opposed to making a joint.

TACK WELD – A weld made to hold parts of a weldment in proper alignment until final welds are made.

THERMIT MIXTURE – A mixture of metal oxide and finely divided aluminium with the addition of alloying metals as required.

THERMIT WELDING – Welding process that produces coalescence of metals by heating them with superheated liquid metal from a chemical reaction between a metal oxide and aluminium, with or without the application of pressure.

T-JOINT – A joint between two members located approximately at right angles to each other in the form of a T.

TORCH BRAZING – A brazing process in which the heat required is furnished by a fuel gas flame.

TWIN CARBON ARC WELDING – Process that produces coalescence of metals by heating them with an electric arc between two carbon electrodes. No shielding is used.

UNDER WELDING – Depositing less filler material than required.

WEAVE BEAD – A type of weld bead made with transverse oscillation.

WELD – A localized coalescence of metals or non-metals produced either by heating the materials 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 material.


WELDING ELECTRODE – A component of the welding circuit through which current is conducted and which terminates at the arc, molten conductive slag or base metal.


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