Welding Terminology: How To Successful Understand Key Terms

Welding Terminology is the backbone of any productive conversation between welding professionals. It provides a unified language that brings clarity and precision to the craft.

For both the seasoned welder and the curious enthusiast, a well-rounded understanding of these terms can make all the difference.

So, let’s delve into some of the must-know terms in welding from A to Z that can sharpen your skills and knowledge.

Here's What You Will Learn

Welding Terminology A – C

Welding Terminology A

Arc: The physical gap between the end of the electrode and the workpiece where the welding takes place, often producing a bright light.
Arc Blow: The deflection of the arc from its intended path due to magnetic forces.
Arc Cutting: Using an arc to cut through metals, often done using a carbon electrode.
Arc Length: The distance between the tip of the electrode and the weld pool.
Arc Strike: A mark left on the base metal where an arc was struck but not followed by a weld bead.
Arc Time: The time during which an arc is maintained in welding.
Arc Voltage: The voltage drop across the welding arc.
Autogenous Weld: A weld made without the addition of filler material.
AWS: Stands for American Welding Society, which sets standards for welding.
Axial Force: In resistance welding, it’s the force applied along the electrode axis.
Alloying Element: Elements added to a metal to improve its properties.
Aluminum Welding: A process that involves joining pieces of aluminum using various welding techniques.
AC (Alternating Current): Current that periodically reverses direction. Some welding processes, like TIG (Tungsten Inert Gas) welding of aluminum, utilize AC.
Amperage (or Current): The amount of electrical current flowing during the welding process.
Annealing: The process of heating a material to a specific temperature and then cooling it to soften and reduce brittleness.
Anti-Spatter: A spray or compound applied before welding to prevent spatter from sticking to surfaces.
Arc Decay Time: The time it takes for the welding arc to extinguish after the welding current stops.
Arc Energy: The amount of energy produced by the welding arc, typically measured in Joules per millimeter.
Arc Force: The current increase with a decrease in arc length during welding.
Arc Initiation: The method or action of starting the welding arc.
Arc Stability: The ability of the arc to maintain a consistent and uninterrupted flow during welding.
As-Welded: Refers to the condition of a weldment after welding but before any post-weld heat treatment or finishing operations.
Arcing Time: The actual time an arc is maintained during the welding process.
Atomizing: Breaking up a stream of molten metal into fine particles.
Automatic Welding: A welding process that utilizes equipment which welds without the constant adjusting of controls by a welder or operator.
Autogenous Fusion: Fusion without the addition of filler material.
Arc Spot Weld: A spot weld made by an arc welding process.
Arcing Gas: The gas that sustains the welding arc. This might be an external shielding gas or a gas produced by the decomposition of the flux or electrode covering.
Arc Column: The constricted area of the welding arc.
Arc Braze Welding: A process in which brazing and arc welding are combined, using equipment and techniques common to arc welding.
Arcing: The process of establishing and maintaining an electric arc.
Ambient Temperature: The temperature of the surrounding environment.
Adherent Spatter: Spatter that is attached to but not fused with the base metal or previous weld bead.
Afterflow Time: The duration for which shielding gas continues to flow after the arc has been terminated.
Adaptive Control: A system that can modify its operation in real-time to adjust to variations in the welding process.
Arc Balance: In AC TIG welding of aluminum, it refers to the balance between the electrode positive and electrode negative portions of the AC cycle.
Arc End Crater: A depression at the end of a weld bead where the welding arc was terminated.
Arc Length Control: An automatic system that adjusts the arc length during welding.
Arc Penetration: The depth to which the arc heat has melted the joint.

Welding Terminology B

Backhand Welding: A welding technique where the welding torch or electrode is directed opposite to the progression of welding.
Backing: Material placed at the root of a weld joint to support and shield the molten weld metal. It can be removed after welding or left in place.
Backing Weld: A weld that’s deposited at the back of a single groove weld.
Backstep Sequence: A sequence in which weld beads are deposited in a direction opposite to the progression of welding.
Back Gouging: The removal of weld and base metal from the welded joint’s reverse side to ensure complete penetration upon subsequent welding from that side.
Bare Electrode: An electrode without any coating or covering, other than that which might result from the normal finishing processes.
Base Metal: The primary metal or material that is being welded or cut.
Bead: A deposit of weld metal from a single pass.
Bead Weld: A type of weld composed of one or more string or weave beads.
Brazing: A process of joining metals in which a filler metal is melted and drawn into a capillary formed by the assembly of two or more workpieces. The melting point of the filler metal is above 840°F (450°C) but below the melting point of the workpieces.
Butt Joint: A joint between two members aligned approximately in the same plane.
Butt Weld: A weld in a butt joint.
Build-Up: The addition of weld metal on a surface to increase its dimensions.
Burn-Through: Melting through the base metal, often leading to a hole, during the welding process.
Burn-Off Rate: The rate at which the electrode melts.
Buttering: A technique where a layer of weld metal is deposited to change the chemical composition of the surface. This is often done before completing the weld with a different filler material.
Brazed Joint: A joint united by brazing.
Brazing Preweld Heat: The heat applied to an assembly before brazing to ensure the required brazing temperature is reached rapidly upon applying the brazing filler metal.
Brazing Flux: A material used during brazing to prevent, dissolve, or remove oxides and other undesirable surface substances.
Brittle Fracture: A fracture characterized by a relatively smooth and shiny appearance, which occurs with little or no plastic deformation.
Break Test: A destructive test for assessing the soundness or the adherence of cladding, overlays, surfacing, or bonds.
Burr: A sharp protruding edge on metal after it’s been cut or drilled.
Bevel Angle: The angle formed between the prepared edge of a member and a plane perpendicular to the surface.
Bond: The union of materials by adhesion and/or cohesion.

Welding Terminology C

Camber: The deviation of a side edge from a straight line. It’s the amount by which a side edge is curved.
Cap Pass: The final layer or layers of weld material deposited on a joint to produce the desired shape and contour.
Carburizing Flame: An oxyfuel flame that has an excess of acetylene, which can introduce carbon into the weld.
Carbon Arc Welding (CAW): A process that uses an arc between a carbon electrode and the workpiece.
Cavity: A hole in the weld metal caused by the escape of gas or shrinkage.
Chipping: The process of removing slag, spatter, or excess weld metal using a chipping hammer.
Cladding: A layer of corrosion-resistant or wear-resistant material applied over a different material.
Cleaning: The removal of contaminants like oil, grease, rust, or oxide from the base metal or weld.
Coalescence: The process of merging or growing together of small particles into a single solid mass.
Cold Crack: Cracks that form after the metal has cooled, usually below the transformation temperature.
Cold Lap: An overlap of weld metal on the base metal or previously deposited weld metal without adequate fusion.
Cold Welding: Joining processes that join materials at approximately room temperature, without melting.
Complete Joint Penetration (CJP): When the weld metal fully extends through the joint thickness.
Concavity: The depression of a weld surface below the plane of the adjoining surfaces.
Consumable Electrode: An electrode that’s consumed during the welding process, contributing to the weld metal.
Contactor: An electromagnetic switch used to initiate the current flow in welding machines.
Continuous Weld: A weld that extends continuously from the start to the finish of a joint.
Convexity: The amount by which a weld surface extends above the plane of the adjoining surfaces.
Cover Pass: Another term for the cap pass.
Crater: A depression at the end of a weld bead.
Crater Crack: A crack that forms in the crater of a weld bead.
Cross Contamination: Unwanted transfer of material from the electrode, filler, or base metal during welding.
Current: The flow of electricity in a circuit. It can be Direct Current (DC) or Alternating Current (AC).
Curing: In relation to welding, it can refer to the hardening process of some resin-based materials.
Cutting Torch: A tool used in oxyfuel processes to cut through metals by using the heat of an oxygen-fuel flame to bring the metal to its ignition temperature.

Welding Terminology D – F

Welding Terminology D

DC (Direct Current): An electric current that flows in one direction.
DCEN (Direct Current Electrode Negative): Also known as “straight polarity”, this is when the electrode is the negative terminal in DC welding.
DCEP (Direct Current Electrode Positive): Also known as “reverse polarity”, this is when the electrode is the positive terminal in DC welding.
Dead Man Switch: A safety feature found on some welding equipment that requires continuous pressure by the operator. If released, it stops the operation.
Deposition Efficiency: The ratio of the weight of deposited weld metal to the weight of filler metal consumed.
Deposition Rate: The rate at which the filler metal is deposited during the welding process, often expressed in pounds per hour or kilograms per hour.
Die Penetrant Inspection: A non-destructive testing method that uses a liquid penetrant to detect surface defects in non-porous materials.
Diffusible Hydrogen: Hydrogen that can diffuse or move within a metal, often a concern in welding because of the potential for hydrogen-induced cracking.
Direct Arc Welding: A welding process where the arc is struck directly between the workpiece and the electrode.
Distortion: The warping or deformation of a weldment due to the effects of thermal expansion and contraction.
Drag Angle: The angle between the electrode and a line perpendicular to the base plate in the direction of welding.
Drop-Through: A defect in spot or seam welding where an excessive amount of material melts and drops out of the weld zone.
Ductility: The ability of a material to deform plastically without fracturing, often measured by the material’s ability to be elongated in a tensile test.
Duty Cycle: A rating that indicates the amount of time, within a 10-minute period, a welding machine can be operated at its rated output without overheating.
Dwell Time: In resistance welding, it’s the time during which the current is off between the impulses.
Dynamic Properties: Properties of materials measured with the material subjected to dynamic or rapidly applied loads, such as impact tests.
Double V-Groove Weld: A type of joint where both pieces have a V-shaped edge, creating a double V when joined.
Double Arcing: In submerged arc welding, using two arcs between a single electrode and the workpiece or between two electrodes and the workpiece.
Downhand Welding: Also known as “downward welding”, it’s a technique where welding is performed from the top side of the joint, and the molten metal is deposited downward.
Drag: In welding, it refers to the amount the electrode is angled back from the direction of travel.
Dross: The waste or impurities that form on the surface of molten metal, often requiring removal after cutting operations.
Dryback: The distance or space behind the arc in which slag melts but remains on the surface of the weld bead.
Dry Rod Oven: An oven used to store electrodes and keep them free from moisture.
Duplex Stainless Steel: A type of stainless steel that contains a mix of austenite and ferrite phases, offering a combination of good strength and corrosion resistance.

Welding Terminology E

EAC (Exposure to Atmospheric Conditions): Refers to electrodes that have been exposed to moisture or other conditions that might degrade their performance.
Edge Joint: A joint between the edges of two or more parallel or nearly parallel members.
Edge Weld: A weld along the edge of a piece of material.
Efficiency: The effective power output of a welding machine as a percentage of its input.
Electrode: A conductor through which an electric current enters or exits a nonmetallic medium, like an arc welding circuit.
Electrode Extension: The length of the wire/electrode sticking out past the end of the contact tip in wire welding.
Electrode Force: In resistance welding, the force with which the electrode is applied to the workpieces.
Electrode Holder: A device that holds the electrode and provides an electrical connection to the welding cable.
Electrode Lead: The cable that connects the electrode holder to the welding machine.
Electroslag Welding (ESW): A welding process where the heat needed to melt the workpieces is produced by a molten slag.
Elongation: The increase in length of a test specimen after it has been pulled in a tensile test, usually expressed as a percentage of the original length.
Exothermic Reaction: A reaction that releases heat. In welding, certain processes use exothermic reactions to produce the heat needed to melt metal.
External Longitudinal Seam: The seam on the outside of a pipe or tube running parallel to its long axis.
Extrusion: A defect where metal is squeezed out from the weld.
Eye Hazard Area: An area within which there’s a possibility of eye injury due to the welding process.
EZ (End of Run): The point where a welding pass ends.
End Crater: The depression at the end of a run or weld bead.
Equivalent Diameter: For a non-circular weld, the diameter of a circle that would have the same cross-sectional area.
Expansion Coefficient: A measure of how much a material will expand (or contract) for each degree of temperature change.
Erosion: The gradual wearing away of a material due to thermal or mechanical action, often seen in the context of electrode wear in some welding processes.
Expulsion: The ejection of molten metal from the weld, usually seen in resistance welding.
Electrical Stickout: In gas metal arc welding and flux cored arc welding, the distance from the tip of the contact tube to the un-melted electrode end.
Electrolytic Cleaning: A process to clean metals using an electrolyte and electric current.
Encapsulation: Enclosing or sealing off an area or substance, often referring to sealing off hazardous materials.

Welding Terminology F

Face: The exposed surface of a weld, on the side from which welding was done.
Face Reinforcement: Weld reinforcement on the face of a weld.
Faying Surface: The surface of a member that is in contact with another member to which it is joined.
Feathering: The tapering of a crack or groove.
Ferrite: A microconstituent or phase in steel, primarily a solid solution of carbon in body-centered cubic iron.
Filler Metal: Metal added during the welding process to provide some or all of the weld metal. This can be in the form of rods, wires, and electrodes.
Fillets: A type of weld used to join two surfaces at approximately right angles to each other in a lap, tee, or corner joint.
Flame Cutting: An oxyfuel gas cutting process used to sever metal by means of a chemical reaction of oxygen with the base metal at elevated temperatures.
Flame Hardening: A process where the surface of a metal part is heated by a direct flame and then quenched, increasing its hardness.
Flare Bevel Groove: A groove melted into the surface of a flanged edge.
Flare V-Groove: A groove melted into the surface of one member of a lap joint.
Flash: The metal that is expelled from the base metal during the formation of a forge or resistance weld.
Flashback: The flame burning inside the torch or back into the hose. It is a dangerous condition.
Flat Position: The position of welding where the welding is done from the upper side of the joint, and the face of the weld is approximately horizontal.
Flux: A material used to prevent, dissolve, or facilitate the removal of oxides and other undesirable substances.
Flux Cored Arc Welding (FCAW): An arc welding process that uses a tubular electrode filled with flux.
Fluxing: The act of using a flux to clean the base metal or to shield the weld.
Forehand Welding: A technique where the welding torch or gun is pointed back at the completed weld.
Forge Welding: A process in which metals are heated in a forge and then hammered or pressed together.
Free Machining: Refers to steels that have additives that make them easier to machine.
Fusion: The melting together of metal parts to produce a weld.
Fusion Zone: The area of base metal melted as determined on the cross-section of a weld.
Fusion Welding: Any welding process that uses fusion of the base metal to make the weld.
Fume Extraction: The process of removing welding fumes from the working area, typically using a fume hood or similar equipment.
Fume Plume: The visible cloud of gas, fume, and particulates that rises from the welding or cutting arc.

Welding Terminology G – I

Welding Terminology G

Galvanic Corrosion: Corrosion that occurs when dissimilar metals are in contact in an electrolyte.
Gas Metal Arc Welding (GMAW): Often referred to as MIG (Metal Inert Gas) welding. It’s an arc welding process that uses an externally supplied gas for shielding and a continuously fed filler metal.
Gas Nozzle: The component in a welding gun or torch through which shielding gas flows to protect the weld pool from contamination.
Gas Pocket: A type of weld discontinuity where gas is trapped, leading to voids in the weld.
Gas Tungsten Arc Welding (GTAW): Also known as TIG (Tungsten Inert Gas) welding. An arc welding process that uses a non-consumable tungsten electrode and an inert gas for shielding.
Gas Welding: A group of welding processes in which the welding heat is obtained from a gas flame.
Globular Transfer: A type of metal transfer in GMAW where the metal transfers across the arc in large droplets.
Gouging: Removing weld metal or base metal by using an arc cutting process.
Grain Refinement: Altering the microstructure of a metal to produce finer grains, which often results in improved mechanical properties.
Grinding: The process of removing metal using an abrasive wheel.
Ground Connection: The connection of the welding circuit to the workpiece.
Ground Lead: The cable that connects the workpiece or the workpiece table to the welding machine, completing the electrical circuit.
Groove: The space or gap prepared between two workpieces to be joined by a groove weld.
Groove Angle: The total angle of the groove between parts to be joined by a groove weld.
Groove Face: The surface of the base metal that will be molten during welding.
Groove Radius: Used for U-groove and J-groove weld preparations, it’s the radius used to form the bottom of the groove.
Groove Weld: A weld made in the groove between two workpieces to form a joint.
Guarded Electrode: An electrode equipped with a shield or guard to prevent accidental electrical contact.
Gun: A device used in semi-automatic and automatic welding operations which holds the electrode and may also guide it into the weld.
Guide Tube: A tube used to guide the electrode wire from the wire feeder to the gun.
Gas Flow Rate: The rate at which shielding gas flows during the welding process, usually measured in liters per minute (L/min) or cubic feet per hour (CFH).
Gas Lens: A device often used in GTAW to improve the shielding gas coverage by directing its flow.
Gas Cup: The component surrounding the electrode in GTAW, directing the flow of shielding gas to the weld area.

Welding Terminology H

Hardfacing: The application of wear-resistant weld metals to a surface to increase its resistance to abrasion, impact, erosion, and other forms of wear.
Hardness: A measure of a material’s resistance to localized deformation, usually in the form of a dent or scratch.
Hardness Test: A test used to measure the hardness of a material, such as the Rockwell or Brinell hardness tests.
Heat-Affected Zone (HAZ): The portion of the base metal immediately adjacent to the weld zone that has not been melted but has undergone structural changes due to the heat of welding.
Heat Input: The amount of energy introduced into the workpiece during welding, typically measured in joules per millimeter or kilojoules per inch.
Heat Sink: A mass of metal (or other material) used to absorb and dissipate heat from the weld zone, helping to control the heat input and prevent distortion or burn-through.
Heat Treatment: A process of heating and cooling a material to achieve desired changes in its mechanical properties, hardness, or microstructure.
Helix Angle: The angle of the spiral of an electrode relative to its axis.
Hot Cracking: Cracking that occurs when the metal is near its melting point, typically during the solidification process.
Hot Pass: In multi-pass welding, the second pass that is made immediately after the root pass.
Hot Shortness: A condition where the metal becomes brittle while hot, leading to cracking during solidification.
Hot Working: Deforming metal at a temperature high enough to avoid strain hardening.
Hydrogen Embrittlement: A phenomenon where metals, particularly high-strength steels, become brittle due to the absorption and diffusion of hydrogen.
Hydrogen Induced Cracking (HIC): Cracking caused by the presence of diffusible hydrogen in metals.
Hydrostatic Pressure Test: A test where a component, such as a pipe or vessel, is filled with a liquid and pressurized to check for leaks or to ensure structural integrity.
Hot Wire Gas Tungsten Arc Welding: A variation of GTAW where the filler metal wire is electrically heated before entering the weld pool.
Hood: A protective device worn over the head and neck to shield the face and eyes from radiation, sparks, and spatter during welding.
Hot Spot: An area of concentrated heat.
Hypoeutectoid Steel: Steel that has a carbon content less than the eutectoid composition (usually less than 0.77% carbon).
Hypereutectoid Steel: Steel that has a carbon content greater than the eutectoid composition (usually more than 0.77% carbon).
Homogenization: The process of creating a uniform composition throughout a material by heat treatment or other means.

Welding Terminology I

Inclusion: A non-metallic particle or material trapped inside the metal, which can be a source of weakness or defect in the weld.
Inert Gas: A gas that does not react with other substances under the conditions of welding, typically used for shielding in processes like TIG (GTAW) and MIG (GMAW).
Intergranular Corrosion: Corrosion that occurs along the grain boundaries of a material, particularly in stainless steels under certain conditions.
Intermittent Weld: A weld that consists of a series of short welds separated by unwelded spaces.
Interpass Temperature: The temperature of the weld area between the completion of one weld pass and the beginning of the next.
Inverter: An electronic device that converts direct current (DC) to alternating current (AC), often used in modern welding machines for power efficiency and control.
Impact Strength: The ability of a material to resist fracture under sudden, forceful impact.
Inductance: The property of an electrical circuit to oppose a change in current, often used in welding machines to control the arc characteristics.
Infrared Radiation: Electromagnetic radiation in wavelengths longer than those of visible light but shorter than those of microwaves. It can be a source of harmful exposure during welding.
Initial Preheat Temperature: The temperature to which the base metal should be heated before starting the welding process.
Ion: An atom or group of atoms that has gained or lost electrons, becoming electrically charged.
Ionization Potential: The amount of energy required to remove an electron from an atom, relevant in the formation of a welding arc.
Iron Powder Electrode: A type of electrode coated with iron powder to increase its deposition rate.
Isotropic: Having identical properties in all directions. In the context of materials, it refers to having the same properties regardless of the direction of measurement.
Isothermal Transformation: A transformation in metal that occurs at a constant temperature.
Internal Longitudinal Seam: A seam inside a tubular product, like a pipe, running parallel to its long axis.
Intrinsic Safety: A design approach where the energy available in the system is always low enough that ignition of a hazardous atmosphere (like explosive gases) cannot occur.
Inspection: The process of examining a weld for defects or to ensure it meets specifications and standards.
Instantaneous Ignition Temperature: The minimum temperature at which a substance will ignite without an external ignition source.
Intercritical Heat Treatment: A heat treatment that involves heating the steel into a temperature range where both ferrite and austenite are present.
Inlay: A layer of a specific material or alloy added to a base metal surface for improved properties.

Welding Terminology J – L

Welding Terminology J

Joint: The junction of members or the edges of members which are to be joined or have been joined.
Joint Design: The specific configuration in which two or more workpieces are to be joined by welding.
Joint Efficiency: A factor representing the strength of a welded joint in comparison to the base metal.
Joint Penetration: The depth that a weld extends into a joint, from its face into the joint.
Joggle Joint: A joint where one piece is notched and the other piece is formed to match, so they fit together.
Joule: A unit of energy, used to describe heat input during welding.
Joint Preparation: The operations involved in getting the edges of the workpiece into the best condition for welding.
Joint Root: The part of a joint to be welded where the members approach closest to each other. In cross section, the joint root may be either a point, a line, or an area.
Jump Welding: The practice of making non-sequential welds in a pattern that distributes the heat and minimizes distortion.
Jig: A device used to hold parts in a specific alignment during welding.
Joule Heating: Refers to the process of producing heat by passing current through a resistor; in welding, the workpiece can act as the resistor.
J-Bevel: A type of edge preparation where one piece has a side beveled in the shape of the letter J.
Jack Stand: A supporting stand that can be adjusted in height, used to support pipes or other materials during the welding process.
Jet Welding: A welding process where a jet of molten metal is forced between two workpieces to be joined.

Welding Terminology K

Keyhole: A hole that forms in the base metal just in front of the arc and then solidifies behind the arc in some welding processes, such as in plasma arc or keyhole GTAW.
Killed Steel: Steel that has been deoxidized with elements like silicon or aluminum before casting to prevent the evolution of gas during solidification.
Kerf: The gap made by cutting a piece of metal, which may need to be considered when fitting pieces together.
Kicker: A small tack weld used to hold pieces in place before welding.
Knockout: A test performed to determine the adhesion of a coating or lining.
Knoop Hardness Test: A micro-hardness test using a diamond indenter with a rhombohedral point.
KVA (Kilovolt-Ampere): A unit of apparent power in an electrical circuit. Some welding equipment is rated by KVA.
Kilowatt (kW): A unit of power representing a thousand watts, often used in reference to the power usage of welding machines.
Kneading Action: The deformation and flow of metal during the friction welding process.
Knurling: A process of producing a regular pattern of small, raised areas on a surface for grip, not exclusive to welding but may be seen on welding tools or components.

Welding Terminology L

Lamellar Tearing: A type of crack that occurs in the through-thickness direction of plate materials, typically resulting from welding.
Lap Joint: A joint between two overlapping members.
Laser Beam Welding (LBW): A welding process where fusion is produced using the energy from a laser.
Lateral Deflection: The sideways movement of a beam under load.
Lath Martensite: A type of martensite structure found in steel, which is plate-like in shape.
Leg: The distance from the joint root to the toe of the fillet weld.
Leg Length: The length of one side of a right-triangle-shaped weld, specifically a fillet weld.
Levelling: The process of making a surface flat or even.
Line Energy: The amount of energy per unit length of weld, often used in context with laser and electron beam welding.
Liquid Penetrant Inspection (LPI): A non-destructive testing method used to detect surface defects in materials. It involves applying a liquid to the surface and checking for its seepage into defects.
Liner: A component in a welding torch that guides the welding wire from the wire feeder to the contact tip.
Live Tinning: The process of coating a metal with molten solder.
Longitudinal Crack: A crack that runs lengthwise in a weld or material.
Low Alloy Steel: Steel alloyed with other elements, typically at less than 10%.
Low-Hydrogen Electrode: An electrode designed to minimize the amount of hydrogen introduced into the weld. Used to prevent hydrogen-induced cracking.
Lug: A projection on a component or part to aid in its alignment or attachment.
Lamination: Imperfections in metals in the shape of thin layers, often parallel to the worked surface.
Lancing: Cutting a metal by a jet of oxygen after the metal has been heated to its ignition temperature.
Lead: In welding torch movement, the angle between a perpendicular to the base metal surface and a line through the center of the electrode.
Leakage Current: Any current, often unwanted, that flows outside the primary current path.

Welding Terminology M – O

Welding Terminology M

Macrostructure: The structure of metals as revealed by macroscopic examination.
Magnetic Arc Blow: Deflection of the welding arc caused by the workpiece’s magnetic fields.
Manual Welding: Welding wherein the entire welding operation is performed and controlled by hand.
Martensite: A hard, brittle form of steel resulting when steel is cooled very rapidly.
Matching Weld Metal: Weld metal with mechanical properties closely approximating those of the base metal.
Metal Active Gas (MAG) Welding: Another term for GMAW (Gas Metal Arc Welding) when a reactive gas is used.
Metal Cored Electrode: A type of electrode used in arc welding that consists of a hollow metal electrode containing flux.
Metal Inert Gas (MIG) Welding: Another term for GMAW, specifically when an inert shielding gas is used.
Microstructure: The structure of polished and etched metal viewed under high magnification, often showing details of the grain boundaries and phases.
Miller Process: A process that uses an electric arc to turn oxygen in the air into ozone, which then acts to increase the heat of the welding arc.
MMAW (Manual Metal Arc Welding): Another term for SMAW (Shielded Metal Arc Welding) or stick welding.
Molten Pool: The liquid area in a weld where base and filler metal are combined.
Monel: A series of nickel-copper alloys, known for their resistance to corrosion.
Multi-pass Weld: A weld in which multiple layers (passes) are applied to achieve the desired size or to fill a large groove.
Multiphase Steel: Steel containing more than one type of microstructural phase.
Multi-run Weld: Another term for multi-pass weld.
Muntz Metal: A type of brass containing about 60% copper and 40% zinc.
MIG Gun: The handheld tool used in MIG welding to feed the wire electrode and deliver the shielding gas to the weld zone.
Machining: The process of removing material to shape an object, not specific to welding but often used in conjunction with it.
Mechanized Welding: Welding with equipment that automatically controls one or more of the welding operations.

Welding Terminology N

Neutral Flame: In oxyfuel gas welding or cutting, a flame in which the oxygen and fuel gas volumes are balanced, resulting in a flame with a rounded cone.
Nick Break Test: A type of destructive test used to reveal the quality of a weld, especially for potential slag inclusions.
Nondestructive Examination/Testing (NDE/NDT): Testing methods used to inspect welding work without damaging the welded component. Methods include radiographic, ultrasonic, magnetic particle, and liquid penetrant inspections.
Notch Toughness: The ability of a material to absorb energy in the presence of a notch or crack.
Nozzle: The component of a welding torch through which the shielding gas flows.
Normalized: A heat treatment process where a metal is heated to a specific temperature and then allowed to cool in still air. It’s used to refine the grain structure and improve the metal’s mechanical properties.
Nugget: The solidified molten zone in resistance spot and resistance seam welding.
Narrow Gap Welding: A welding technique where the groove between the pieces to be joined is narrower than in traditional V-groove designs.
Non-Ferrous: Metals that do not contain significant amounts of iron. Examples include copper, aluminum, and zinc.
Notch Sensitivity: The tendency of a material to fracture at notches or other stress concentrators when subjected to stress.
Nozzle Contact Distance: The distance from the end of the welding torch nozzle to the workpiece.
Nucleation: The formation of small, initial sites (nuclei) on which growth can occur, like the beginning formation of grains during the solidification of weld metal.
Neutral Axis: In bend testing, the axis where there’s no stretching or compression.
Nickel-Based Alloys: Alloys predominantly made of nickel, known for their high-temperature strength and corrosion resistance.
Non-Consumable Electrode: An electrode that is not consumed (or melted) during the welding process, such as in Tungsten Inert Gas (TIG) welding.

Welding Terminology O

Open-Circuit Voltage (OCV): The voltage present at the output terminals of a welding power source when no current is flowing.
Orifice: An opening or hole, such as the one in a cutting torch through which the oxygen flows to perform the cutting action.
Oxidation: The process of combining with oxygen, often resulting in a form of corrosion.
Oxyacetylene Welding (OAW): A welding process wherein coalescence is produced by heating with an oxyacetylene flame.
Oxyfuel Gas Welding (OFW): A group of welding processes that produce coalescence by heating with an oxyfuel gas flame or flames, with or without the application of pressure, and with or without the use of filler metal.
Overlap: The protrusion of weld metal beyond the weld toe or weld root.
Overwelding: Applying more weld metal than is necessary to meet the required specifications.
Oxide: A compound formed when oxygen combines with another element.
Out-of-Position: Welding in any position other than the flat or downhand.
Oxygen Cutting: A process where a jet of pure oxygen is directed onto preheated metal to burn away a narrow path.
Ozone: A toxic gas produced by the action of ultraviolet rays from the welding arc on oxygen in the air.
Oscillator: A device used to move the welding or cutting torch in a controlled, repetitive pattern.
Oversize Electrode: An electrode that is larger in diameter than the specifications or standards call for.
Oxygen Lance: A pipe or tube used to direct a stream of oxygen onto a spot being cut or heated.
Overlay: A layer of weld metal applied to a base metal or to a previously deposited weld material to obtain desired properties or dimensions.

Welding Terminology P – R

Welding Terminology P

Peening: The mechanical working of metal, often using a hammer, to counteract the effects of stresses in a weld.
Penetration: The depth below the original surface that weld metal extends in the base metal.
Plasma: In the context of welding, it refers to a hot, highly ionized gas used in plasma arc systems.
Plasma Arc Welding (PAW): A process which melts and joins metals by heating them with a plasma arc between a tungsten electrode and the workpiece.
Plug Weld: A circular weld made through one member of a lap or tee joint joining that member to the other.
Porosity: Cavity-type discontinuities formed by gas entrapment during the solidification of the weld.
Postheating: The application of heat to a weld or base metal immediately after welding.
Postweld Heat Treatment (PWHT): Any heat treatment after welding, often done to improve the properties of the weld and adjacent base metal.
Puddle: The molten pool of metal in a weld area.
Pulse Welding: A variation of the welding process where the current is pulsed between high and low levels, typically used to control heat input.
Pass: A single progression of a welding or cutting torch along the joint or across the workpiece.
Purge: To displace the air in an area with an inert gas, often done to ensure a clean weld or cut.
Penetration Profile: The shape of the weld bead cross section.
Preheating: Applying heat to the base metal immediately before welding.
Push Angle: When the welding gun is angled in the direction of progression.
Porosity Test: A test to detect the presence of porosity in welds.
Polarity: In electric welding, it’s the direction of current flow. Direct current electrode negative (DCEN) means the electrode is the negative pole in the circuit, and direct current electrode positive (DCEP) means it’s the positive pole.
Passivation: The process or state in which a material becomes passive, or non-reactive, often referring to metals that naturally form an oxide layer for protection against corrosion.
Pitting: Small holes or cavities on the surface of a metal, usually from corrosion.
Protective Atmosphere: A controlled environment, often an inert or reduced-oxygen atmosphere, used in some welding processes to prevent oxidation of the workpiece.

Welding Terminology Q

Quenching: The rapid cooling of metal, often in water or oil, after it has been heated to a specific temperature. This process is used to harden certain metals.
Quenched and Tempered: Describes steel that has been heated to a high temperature, quenched rapidly, and then reheated to a lower temperature to achieve desired mechanical properties.
Quality Control (QC): The methods and procedures used to ensure that weldments meet specified requirements.
Quality Assurance (QA): The systematic actions necessary to provide confidence that a product or service will satisfy given requirements for quality.
Qualification: The demonstration of ability to meet specified standards. In welding, it can refer to the process by which a welder or welding procedure is tested and proven capable of producing welds of acceptable quality.
Qualified Weld: A weld that meets the acceptance criteria specified in a code or standard.
Quench Cracks: Cracks that form in metals due to the stresses induced by rapid cooling or quenching.
Quick-Release Clamp: A device that rapidly clamps and releases workpieces or welding equipment.
Quality Factor: A numerical value used to modify the radiographic film response to radiation of a specified energy compared to the response to radiation of a standard energy.
Quantitative Analysis: In the context of welding and metallurgy, it refers to the precise determination of elemental composition or concentration of components.

Welding Terminology R

Root: The points in a joint to be welded where the members are closest together.
Root Opening: The separation between the pieces to be joined at the root.
Root Penetration: Depth to which weld metal extends into the root of a joint.
Root Pass: The first pass of a multi-pass weld.
Reinforcement: Weld metal in excess of the quantity required to fill a joint.
Residual Stress: Stresses remaining in a metal object, even after the original cause of the stress (such as external force or heat) has been removed.
Reverse Polarity: Direct current electrode positive (DCEP) in arc welding. In this setup, the workpiece is the negative terminal.
Rod: A form of filler metal, commonly used in brazing and gas tungsten arc welding.
Run-off Tab: A small piece of metal temporarily attached to the end of a joint to allow the weld to be carried past the end of the actual joint.
Run-on Tab: A piece of metal temporarily attached to the start of a joint to facilitate starting the weld without defects.
Radiographic Testing: A non-destructive test method where the part is exposed to X-rays or gamma rays. The radiation that passes through the part strikes a piece of radiographic film, creating an image of the part’s internal structure.
Refractory: Materials that are resistant to heat, often used in situations where high-temperature resistance is essential.
Repair Welding: The welding process done to repair defects in a metal piece.
Resistance Welding (RW): A group of welding processes that produce coalescence with heat from resistance to electric current in a circuit of which the workpiece is a part, and by application of pressure.
Rust: The common name for iron oxide, which is formed when iron or steel reacts with oxygen and moisture.
Racking: A distortion due to uneven contraction of the weld and adjacent base metal during cooling.
Re-melt: A procedure in which a completed weld or portion of it is remelted without the addition of filler metal.
Root Face: A portion of the groove face adjacent to the root of the joint.
Rutile: A naturally occurring mineral used in making coatings for certain types of electrodes.
Return Current Lead: The electrical connection from the workpiece back to the welding power source.

Welding Terminology S – U

Welding Terminology S

Seam Weld: A type of weld situated at the flat side of two pieces of metal that have been joined edge to edge.
Shielded Metal Arc Welding (SMAW): A process that uses a consumable electrode coated in flux to lay the weld.
Shielding Gas: Protective gas used to prevent the molten weld from reacting with the atmosphere, resulting in oxidation.
Slag: The residue left on the weld bead from the flux in shielded metal arc welding or flux-cored arc welding.
Spatter: Small particles or droplets of molten material that are scattered around the weld bead.
Spot Weld: A weld made by resistance welding between overlapping pieces of metal.
Stainless Steel: A steel alloy that contains a minimum of 10.5% chromium, known for its resistance to rust and staining.
Stress Relief: A process where the welded item is heated to a lower temperature, held for a period of time, and then cooled slowly to reduce internal stresses.
Submerged Arc Welding (SAW): A welding process that uses a granular flux to cover the weld.
Surfacing: The process of applying a layer of weld metal to a base metal or a previously deposited weld metal for the primary purpose of obtaining desired wear and corrosion resistance properties.
Stringer Bead: A type of weld bead made without any weaving motion, laid in a straight line.
Stick Welding: Another term for Shielded Metal Arc Welding (SMAW) because the electrode used looks like a stick.
Strike (or Striking) the Arc: The action to initiate the welding arc. Typically done by making brief contact of the electrode with the workpiece.
Stud Welding: A process where a metal stud is placed against the workpiece and an arc is struck, melting the end of the stud and a portion of the base metal.
Solidus: The highest temperature at which a material is completely solid.
Solvent Cleaning: A process that removes oil, grease, or other contaminants using organic solvents.
Soak Time: The period during which a material is held at a specific temperature to ensure uniform temperature throughout the material.
Soft Soldering: A process in which a filler metal with a melting point below 800°F (427°C) is used to join metals.
Spool Gun: A type of welding gun, especially used in MIG welding, where the wire spool is located on the gun itself, allowing for more flexibility in welding materials like aluminum.
Stitch Welding: Producing a weld by making intermittent welds in a joint.

Welding Terminology T

Tack Weld: A short weld made to hold parts of a weldment in proper alignment until the final welds are made.
Tandem Welding: The use of two or more welding arcs to make a joint, typically used in submerged arc welding.
Tensile Strength: The maximum load in tension (pulling apart) which a material can withstand before breaking or fracturing.
Thermal Conductivity: The ability of a material to conduct heat.
Thermal Cutting: Processes that use heat to sever metals by melting or by oxidation.
Thermal Stress: Stress introduced by a temperature gradient within a material.
Throat of Weld: The distance from the weld root to the point on the weld face of the triangle’s hypotenuse. This is used in fillet welds.
TIG (Tungsten Inert Gas) Welding: Another term for Gas Tungsten Arc Welding (GTAW). It uses a non-consumable tungsten electrode to make the weld.
Toe of Weld: The junction between the face of a weld and the base metal.
Travel Speed: The speed at which a welding torch or electrode moves along a joint.
Turbulent Flow: A flow regime characterized by chaotic, stochastic property changes, such as low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time.
Twist: A form of distortion in which a plate’s two diagonally opposite corners lift while the other two corners remain either flat or past the original level.
Two-Run Weld: A weld in which two layers are applied to ensure full penetration and complete fusion.
Transition Current: The current at which a transition occurs between different modes of metal transfer.
Travel Angle: The angle relative to the gun or electrode’s direction to the welding direction.
Through Thickness: The direction or plane perpendicular to the surface of a plate or sheet.
Transverse Crack: A crack in a weld or heat-affected zone that is generally perpendicular to the direction of the primary stress causing it.
T-joint: A joint between two members located approximately at right angles to each other in the form of a “T”.
Tack (or Tacking): Temporary points of welding intended to hold parts together before final welding.
Tip Recess: The distance the welding tip extends beyond the nozzle in a MIG gun.

Welding Terminology U

Ultrasonic Testing (UT): A non-destructive testing method that uses high-frequency sound waves to detect imperfections in materials or to measure material thickness.
Undercut: A groove melted into the base metal adjacent to the toe or root of a weld and left unfilled by weld metal.
Underfill: A condition in which a weld face or root surface is below the adjacent surface of the base metal.
U-groove Weld: A type of joint design where one or both pieces to be joined have a U-shaped groove to accommodate the filler material.
Ultrasonic Welding: A welding process that uses ultrasonic vibrations to join materials together. Commonly used with plastics and thin sheets of metal.
Up-slope: A feature of some welding power supplies, especially in TIG welding, where the amperage gradually increases from a preset starting point to the preset maximum to initiate the arc without causing a high amperage surge.
Underbead Crack: A type of crack that appears beneath the weld bead. It’s typically in the heat-affected zone (HAZ) and not visible on the surface.
Up-hand Welding: Another term for vertical welding where welding is done from the bottom up.
Ultrasonic Cleaning: A cleaning process that uses ultrasonic waves along with a cleaning solvent or water to clean the surfaces of parts, especially to remove contaminants or residue.
Upset: The deformation or displacement of material to produce a complete joint, especially in resistance welding.
Upset Welding (UW): A resistance welding process where coalescence is produced by the heat obtained from resistance to electric current between the area of contact of the parts to be joined, combined with pressure.
Upsetting Temperature: The temperature at which materials are heated to prior to the upsetting process to ensure proper coalescence.
Upward Welding: Similar to up-hand welding; it is a welding technique where the direction of welding is upward.
Undercooling: The difference between the liquidus temperature of a metal and the temperature at which solidification completes.
Underwater Welding: The process of welding at elevated pressures, usually underwater. It can be either “wet” underwater welding or “dry” hyperbaric welding inside a specially constructed positive pressure enclosure.

Welding Terminology V – Z

Welding Terminology V

V-groove: A type of joint design where the edges of both pieces to be joined are beveled, typically in the shape of a “V”.
Vacuum Arc Remelting (VAR): A secondary melting process for the production of metal ingots with elevated chemical and mechanical homogeneity.
Vacuum Brazing: A brazing process that is carried out in a chamber or retort under very low atmospheric conditions (vacuum).
Valence Electron: An electron in the outermost shell of an atom that can participate in forming chemical bonds.
Voltage: Electrical potential difference, electric pressure, or electric tension. In welding, it affects the height and width of the welding arc.
Volt-Ampere Curve: A graph showing the relationship between arc voltage and welding current.
Vickers Hardness Test: A microhardness test method that uses a square-based diamond pyramid indenter.
Vertical Welding: A welding process where the progression of welding is done vertically, either upward or downward.
Viscosity: A measure of a fluid’s resistance to gradual deformation by shear or tensile stress.
Volume Welding: A term used to describe welding processes that are designed to deposit a large volume of weld metal, often used in heavy industrial applications.
Vent: An opening provided to allow gases to escape from a mold or core.
Volatile: A substance that easily evaporates at room temperatures.
Voltage Drop: The reduction in electrical potential as electric current moves through a resistance.
Vapor Shield: Gases which protect the molten weld from the surrounding atmosphere.
Variable Polarity Plasma Arc Welding (VPPAW): A welding process where the polarity of the welding current changes frequently, providing cleaning during the electrode positive portion and deep penetration during the electrode negative portion.

Welding Terminology W

Weld: The union of materials (usually metals) produced by heating to a suitable temperature, with or without the application of pressure, and with or without the use of filler metal.
Welder: A person who performs the welding operation.
Weldability: The ability of a material to be welded under the fabrication conditions imposed into a specific, suitably designed structure and to perform satisfactorily in the intended service.
Welding Arc: The discharge of electric current, flowing between the electrode and the workpiece, which provides the heat needed for the welding process.
Weldment: An assembly of parts joined by welding.
Weld Pass: A single progression of welding along a joint. The result of a pass is a weld bead.
Weld Pool: The localized volume of molten metal in a weld prior to its solidification as weld metal.
Welding Electrode: A form of welding filler metal, normally packaged as rods or wire spools, that carries the electric current for arc welding.
Welding Gun: A type of torch where the wire electrode, shielding gas, and welding current are fed through a flexible conduit to the welding gun.
Weld Toe: The point where the weld face meets the base metal.
Weaving: Oscillating the electrode from side to side as you move along the joint in arc welding.
Whipping: A technique in stick welding, where the electrode is quickly moved in and out of the arc.
Work Angle: The angle between a perpendicular line to the base plate and the electrode axis.
Workpiece: The item being welded.
Welding Procedure Specification (WPS): A document that details the welding variables used to make a specific type of weld.
Weld Reinforcement: The metal in a joint weld that is in excess of what is required to fill the joint.
Weld Root: The points at which the back of a weld intersects the base metal surfaces.
Weld Throat: The thickness of the weakest point in a weld.
Welding Helmet: A protective helmet used by welders to protect the eyes and face from harmful rays, sparks, and spatter produced during welding.
Weld Backing: Material that supports the weld during welding. It may or may not become part of the finished weld.

Welding Terminology X

X-ray Inspection: A non-destructive testing method that uses X-rays to detect internal defects in materials. The intensity of transmitted X-rays is monitored after passing through the material, and variations in the transmitted intensity can indicate defects.
X-ray Radiography: A technique similar to X-ray inspection, where X-rays are used to produce a radiograph of a weld, revealing any internal flaws or inconsistencies.
X-groove: A type of joint groove that is in the shape of an “X”. This might be used in certain types of weld preparations.
X-factor: In metallurgy, this refers to the crack susceptibility factor in welds, especially those in high-strength steels.

Welding Terminology Y

Yield Point: The point on a stress-strain curve at which the material begins to deform plastically after elastic deformation. Once this point is passed, the material will not return to its original shape after the removal of the load.
Yield Strength: The amount of stress that a material can absorb before beginning to experience permanent deformation.
Y-groove: A type of joint groove that is in the shape of a “Y”. This might be used in certain types of weld preparations.
Yoke: A structural frame in resistance welding machines to which the welding transformers and electrodes are attached.
Young’s Modulus (Modulus of Elasticity): A measure of the stiffness of a material. It defines the relationship between stress (force per unit area) and strain (proportional deformation) in materials.
Yttrium: An element sometimes used in tungsten electrodes for TIG (tungsten inert gas) welding.

Welding Terminology Z

Zinc: A metal frequently used as a coating on steel (galvanized steel) to provide corrosion resistance. When welding, care must be taken due to the toxic fumes produced by burning zinc.
Zirconium: An element sometimes used in tungsten electrodes for TIG (Tungsten Inert Gas) welding. Zirconium tungsten electrodes can provide stable arcs for AC welding.
Zweisspunt (Z-point): Refers to the inflection point on a stress-strain curve, indicating the end of the uniform elongation in some metals.
Zone Refining: A metallurgical process used to purify metals by moving a narrow molten zone through a long single crystal. As the zone moves, impurities are moved along with it and segregated at one end.
Z-loss: A loss in the thickness of a coating or metal due to corrosion.
Zero-Current Welding: A type of resistance welding where the weld is made at the moment of zero current during alternating current waveforms.
Zig-zag Welding: A technique where the welding torch or electrode moves in a zig-zag pattern to spread out the weld deposit.
Zircon: A mineral that is a source of zirconium and is used in some refractory applications.

Other Welding Terminology

1G, 2G, 3G, 4G: These are welding position designations. For example, 1G refers to a flat welding position, 2G to a horizontal, 3G to vertical, and 4G to overhead.
2F, 3F, 4F: These are fillet weld position designations similar to the groove weld designations. 2F is a horizontal fillet, 3F is a vertical fillet, and 4F is an overhead fillet.
308L, 316L: Examples of specific stainless steel electrode designations, where the numbers refer to the type of stainless steel alloy.
6010, 6011, 7018: Examples of common electrode classifications for Shielded Metal Arc Welding (SMAW). The numbers provide information about the electrode’s usability, tensile strength, welding position, and flux composition.
6G: A welding position that refers to a pipe that’s fixed at a 45-degree angle – it’s a combination of both the horizontal (2G) and vertical (5G) positions.
9% Nickel Steel: A type of steel that contains approximately 9% nickel, commonly used for making liquefied natural gas (LNG) storage tanks because of its superior toughness at low temperatures.
10X and 40X: These can refer to magnification levels used in microscopic inspection of welds and metallurgical samples.
21-6-9: Refers to a specific type of stainless steel alloyed with 21% chromium, 6% nickel, and 9% manganese.

Conclusion

As we’ve seen, these terms offer a clearer path to understanding intricate processes and ensuring communication accuracy. So, as you step forward in your welding endeavors, remember to keep these terms at your fingertips.

They not only guide your hand but also elevate the entire welding community through shared understanding and precision. Keep practicing, stay curious, and let the language of welding be your steadfast ally.

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