Acetone – A colorless, flammable and unstable liquid used to stabilize acetylene under pressure.

Acetylene – A colorless hydrocarbon gas with the formula C2H2. It is used a fuel in oxyacetylene welding.

Alloy – A mixture of elements of at least one metal. For example mild steel and chromium to make stainless steel.

Alternating Current – An electric current that reverses back and forth, following the pattern of a sine wave. This is erratic compared to direct current.

Amperage – A measurement of the flow of electricity which defines how much heat you get.

Arc – The electric arc is created between the electrode and the base metal to melt the metal.

Arc Blow – When an arc moves from its desired path. This can happen in DC welding and is caused by magnetism.

Arc Cutting – Cutting processes where metals are cut just by using the force of the arc.

Arc Gouging –  Where metal is cut with an arc from a carbon electrode.

Arc Voltage – The voltage the runs across the arc

Arc Welding – Where an electric arc is used to fuse metals together

Automatic Welding – Welds that are created by robots

Back Pass – A pass that lays a back weld.

Back Weld – Laying a weld on the back of a single groove weld

Backhand Technique – The opposite of push welding, also known as pull welding, where the electrode points in the opposite direction to the direction of the weld.

Backup Strip – A strip of metal used used to keep molten metal in the weld root and help prevent the base metal from warping.

Bare Metal-Arc Welding – Arc welding process where an unshielded arc produces heat between the workpiece and an electrode that is just lightly coated. In this the filler metal is produced by the electrode.

Base Metal – The primary piece of metal that you are welding.

Bead – The filler metal that is deposited on the base metal during the welding process.

Bevel – When an angle is cut into the base metal to allow for more filler metal.

Bond – Where a welding metal and base metal are connected

Brazing – Welding processes where the filler metal is melted above 800 ºF  and is below the base metal. It is then moved into the joint by capillary attraction.

Brush – A steel wire bristled brush is an important tool to have to clean rust, oil or dirt off the surface of metal.

Buckling – Distortion of the metal caused by heat.

Butt Joint – A basic welding joint where two pieces of metal are flat and butted against each other.

Cap – The final bead on a groove weld

Capillary Attraction – Where the the liquid filler metal flows through the narrow joint to be brazed.

Carbon-Arc Welding – The weld is formed by an arc which is produced between the base metal and a carob electrode.

Carburizing Flame – AKA Reducing flame, this is an oxyacetylene flame which contains an excess of acetylene.

Coalescence – Where metals are fused together

Coated Electrode – A welding rod with flux on the filler metal. This flux can be painted on, and shields the arc upon burning.

Concavity – The distance where a weld bead sags inwards

Cone – The cone shaped section of a flame next to the tip.

Convexity – The distance where a weld bead protrudes from the joint.

Corner Joint – Where you weld a butt joint at a 90 degree angle.

Crack – A crack where the weld fractures

Critical Temperature – Where your base metal changes from solid to liquid

Current – Current is the flow of electricity measured in amps.

Cutting Torch– Used to control the gases for cutting metal

Cylinder – Where gases are stored for various types of welding.

Defect – Any defect with the weld, e.g. porosity or cracks.

Depth of Fusion – The depth that the filler metal penetrates from the surface of the metal

Direct Current – Direct current is where the current flows in one continuous direct, from negative to positive.

Direct Current Electrode Negative – Electricity flows out of the electrode into the work piece. This gives less penetration.

Direct Current Electrode Positive – Electricity flows into the electrode, leading to more heat and penetration.

Ductility – Where metal is bent and becomes permanently deformed without breaking.

Duty Cycle – The time that a welder can operate on a given amperage within a 10 minute period before overheating.

e.g. 20% @ 90A would mean 2 minutes of welding at 90A.

Edge Joint – The joint created where the edges of 2 pieces of metal are butted against each other at 90 degrees.

Edge Preparation – Preparing the edge for welding. e.g. by grinding the surface.

Electrode – The arc is created between the electrode and the work piece. The electrode is different depending on which type of welding process you’re performing. For example, in MIG welding the electrode is wire, while in Stick welding it’s a welding rod.

Electrode Holder – A clamp that holds the electrode in place.

Face – The exposed surface of the base metal where the weld is performed.

Face reinforcement – Reinforcing the weld on the face surface.

Fan – Most welders contain fans to prevent them from overheating which affects duty cycle.

Ferrous Metal – Referring to Iron or an Iron alloy.

Filler Metal – The metal that is melted and added to the weld puddle during a weld.

Flash Burn – The welding arc produces ultraviolet radiation which you must protect yourself against. Flash burn is when the radiation burns your skin and can seriously damage your eyes if you don’t wear the correct safety equipment.

Fillet Weld – A common type of weld, mostly used in T joints, that joins two surfaces together at approximately 90 degrees.

Flow Meter – Used to regulate the pressure and the flow of gas from a gas cylinder.

Flux – Cleans metal to be welded and releases gas when burned to protect the weld pool from contamination (see Flux Cored Arc Welding).

Flux Cored Arc Welding (FCAW) – Similar to MIG welding, this uses a wire electrode as the filler metal but has a flux core which burns to produce the shielding gas, so there is no need for a gas cylinder.

Forge Welding – Welding process where the weld is achieved by heating in a furnace.

Fusion – The complete merging with the base metal when welding.

Galvanized – Galvanised steel is where steel is coated with Zinc so that it isn’t corrosive. When welding galvanized steel you need to burn through this layer of Zinc first so make sure your work environment is well-ventilated.

Gas Metal Arc Welding/GMAW – See MIG 

Gas Pocket – A weld cavity that is produced by gas that is released as the metal cools

Gas Tungsten Arc Welding/GTAW – See TIG

Groove Weld – Where the section you are welding is bevelled to achieve more penetration and a stronger weld.

Impact Test – Where a number of hammer blows are applied to a weld to test its durability.

Inert Gas – A gas that does not have a chemical reaction with the metal.

Inverter – A lighter and more efficient power source used in welders.

Jig – Jigs are used to hold metal into place when fabricating

Joint – The point where two base metals meet to be welded together. The “big five” examples are: Butt joint, lap joint, T joint, edge joint and corner joint.

Lap Joint – A joint where two pieces of metal overlap.

Liquidis – The lowest temperature that a metal is a liquid.

Machine Welding – Welds that are performed by a machine/robot.

Manual Welding – Welds that are performed by a person.

Melting Range – The range of temperatures between liquidus and solidus.

Melting Point – The point when the metal transfers from solidus to liquid.

MIG – MIG is a popular type of welding that uses a spool of solid wire that is fed through a welding gun by pulling a trigger. This forms an arc with the base metal and melts into the weld pool. Shielding gas is used to project the wire from contamination. See More.

Multipass Weld  – When you weld cross a joint more than once.

Non Ferrous – Metal that does not contain iron.

Open Circuit – Where no current flows because the welding circuit is not complete

Oscillate – Moving side to side and zig-zagging the weld to deposit more filer metal.

Overhead Position – Where a horizontal weld is performed from standing underneath the joint.

Parent Metal – The primary piece of metal that you are welding on.

Pass – Welding across the axis of a weld from point a to point b.

Peening – Working the metal by beating it with a hammer.

Penetration – The depth of the weld into the base metal.

Plug Weld – Welding into a hole in the metal on a lap joint where the surface of the bottom piece of metal is visible through the hole.

Porosity – Pockets of gas in the weld, often as a result of shielding gas not properly protecting the weld.

Ports – Small holes in the MIG gun where the shielding gas is released.

Pre Heating – Heating the metal before starting to weld on it. This can improve the weld if the room temperature is very cold.

Puddle – AKA the pool. This is where the filler metal melts and combines with the base metal.

Quench – Suddenly cooling metal to increase its hardness.

Radiation – Radiation is emitted from the arc that is highly dangerous. Make sure that your skin and eyes are covered!

Rods – In stick welding, the electrode is a welding rod.

Root Crack – A crack in the weld or base metal found at the root.

Root Opening – The gap between two bevelled pieces of metal.

Seam Weld – The seam is the line where two pieces of metal join. You should generally try to deposit the filler metal equally on either side of the seam.

Semi-Automatic Welding – Welding that requires a machine (e.g. TIG), but also requires a person to operate it.

Seventy Five/Twenty Five – A reference to shielding gas – 75% Argon and 25% Carbon, my preferred choice of gas for MIG welding.

Shielding Gas – Gas used in MIG welding to surround the wire electrode in order to protect the weld from contamination.

Slag – Slag is solidified flux which is left on the weld once it cool. This should be removed from the weld by either a wire brush, hammer or angle grinder.

Slag Inclusion – Slag inclusion is a weld defect whereby the slag is not properly cleaned from the weld before making another pass, reducing the strength of the weld.

Slot Weld – An elongated plug weld.

Soapstone – Stone that is useful for marking steel.

Solidus – The maximum temperature that a metal is a solid

Spatter – During arc welding the arc sometimes blows filler metal onto the base metal away from the weld pool.

Steel – Alloy of iron with carbon added.

Stick Welding/SMAW – Arc welding that uses a consumable flux coated electrode with a metal core.

Sticking – When the welding rod doesn’t form an arc and sticks to the base metal, usually because the temperature is too low.

Stick Out – The distance that the wire electrode protrudes from the MIG gun.

Stringer Bead – A stringer bead is where you perform a push or pull weld straight across the seam without oscillating.

Surfacing – Depositing filler metal to rebuild equipment that has worn down.

Tack Weld – A small, weak weld that is used to temporarily hold metal in place until it is welded permanently.

Tee Joint – 2 plates of metal that joint to form a T shape.

Tempering –  Reheating steel and then quickly cooling it to increase the strength of the steel.

Tensile Strength – The strength of the metal, measured by it’s ability to resist tension in tensile strength per square inch. e.g. a 6010 welding rod has 60,000 lbs of tensile strength.

TIG – Also know as GTAW/Gas Tungsten Arc Welding, uses a torch with a non-consumable tungsten electrode while feeding a filler rod into the weld pool. It requires a lot of skill as one hand is used to hold the torch, another to hold the electrode and a foot pedal to feed the wire. TIG is a precise type of welding and the ideal process where intricate and smooth welds are required.

Tungsten – Tungsten is used as an electrode in TIG welding. It has a very high melting point so it doesn’t burn up as you use it.

Undercut – A groove that is cut into the base metal with the arc. This is a weld defect and should be filled in with filler metal.

Underfill – When not enough filler metal is deposited into the weld.

Visual Inspection – A weld test where a qualified inspector will examine the quality of the weld. Things to look for include underfill, undercut and porosity.

Voltage – Voltage is the flow of electric force through a conductor.

Warping – When the heat of the weld bends and deforms the base metal

Weave Bead – A weld bead where the torch is oscillated back and forth across the weld.

Weld – Where two metals are fused together.

Weld Blanket – Heat resistant blanket used to protect the area around the work space from damage cause by heat.

Weld Defect – A weakness in the weld.

Weld Gauge – Used to measure the distance from the root of the weld to the face of the weld.

Weld Gun – Used in MIG and FCAW to feed wire into the weld pool.

Weld Symbol – The symbol which shows you which type of weld you need to perform.

Wire Feed Speed – The rate at which wire is released from the welder into the weld.

Welder Certification – Document showing that the welder can weld to industry standards.

Welding Tip – The tip of a weld gun

Welding Torch – Used in gas welding to control the gas flow.