// jargon, decoded
Welding glossary.
Welding has a language all its own. Here's a plain-English A–Z of the terms you'll meet on a machine dial, a consumable label or a spec sheet — duty cycle and polarity, shielding gas and tungsten types, amperage, MIG, TIG and MMA. Not sure what you need? Ask us — we weld too.
A
Amperage (welding current)
The welding current, measured in amps. It largely controls heat and penetration — more amps for thicker metal, fewer for thin — and is matched to the material thickness and to the wire or electrode size.
Arc
The sustained electrical discharge between the electrode and the workpiece. The arc produces the intense heat that melts and joins the metal.
Arc eye (flash burn)
A painful, gritty inflammation of the eye caused by ultraviolet light from the arc — often felt hours later. It's entirely preventable by always using a helmet with the correct shade, even for a quick tack. See our PPE range.
C
CFH (cubic feet per hour)
The unit for shielding-gas flow rate, set on the regulator. Too low and the weld is left unprotected; too high and the turbulence actually draws air in. Typical MIG flow is around 10–15 CFH, more in a draught.
Consumables
The parts used up during welding — wire, rods, contact tips, shrouds, nozzles and gas — that need regular restocking, as opposed to the welder itself. Our consumables guide covers what to keep on the shelf.
Contact tip
The small copper consumable at the end of a MIG torch that transfers current to the wire as it feeds through. It wears with use and is one of the most frequently replaced parts on a MIG setup.
D
Duty cycle
The proportion of a ten-minute period a welder can run at a given output before it has to cool, shown as a percentage. For example, 60% at 200A means six minutes welding, four minutes resting. A higher duty cycle matters for long, continuous welds.
E
Electrode
The component that carries the welding current to the arc. In MMA it's a consumable coated rod; in TIG it's a non-consumable tungsten; in MIG the continuously fed wire is itself the electrode.
F
Filler metal
The added metal that fills a weld joint — MIG wire, a TIG rod or an MMA electrode — chosen to match the base material so the finished joint has the right strength and appearance.
Flux
A coating or core that shields the molten weld from the air and helps clean it, forming a protective slag layer that's chipped off afterwards. It's what makes MMA rods and flux-cored wire work without a gas bottle.
Flux-cored wire (FCAW)
A tubular MIG wire filled with flux that shields the weld from inside, so it can be run without a separate gas bottle. That makes it handy outdoors and on thicker or less clean steel.
G
Gasless MIG
MIG welding using self-shielded flux-cored wire instead of a gas bottle. It's convenient and tolerant of wind, at the cost of more spatter and slag to clean up than gas-shielded MIG.
Globular transfer
A MIG metal-transfer mode where large, irregular droplets cross the arc, giving more spatter. It sits between short-circuit and spray transfer and is generally avoided where appearance matters.
M
MIG / MAG welding
Gas Metal Arc Welding — a continuously fed wire melts under a shielding gas. It's fast and easy to learn, making it the most common process for general fabrication. Strictly, MIG uses an inert gas and MAG uses an active gas such as CO2 or a mix, but the terms are often used interchangeably. New to it? See our first MIG setup guide.
MMA / Stick welding
Manual Metal Arc welding using a flux-coated consumable rod. It's simple, portable and tolerant of wind and dirty metal, which keeps it popular for site work and repairs.
O
OCV (open-circuit voltage)
The voltage a welder produces before the arc is struck. A higher OCV makes an electrode easier to start, which is one reason some rods specify a minimum OCV.
P
Penetration
How deeply the weld fuses into the base metal. Enough penetration gives a strong joint; too little leaves it weak, and too much can burn through thin material — so it's balanced through current, speed and technique.
Polarity (DCEN / DCEP)
The direction of DC current through the circuit. DCEP (electrode positive) gives more penetration and suits most MMA and MIG; DCEN (electrode negative) is used for steel TIG. AC is used for aluminium TIG. Getting polarity right is essential — many MMA rods and gasless wires specify it.
Porosity
Gas bubbles trapped in a weld as it solidifies, leaving holes that weaken it. It's usually caused by lost gas shielding, a draught blowing the gas away, or dirty or damp metal.
PPE
Personal protective equipment for welding — an auto-darkening helmet, gauntlets, fire-resistant clothing and respiratory protection — guarding against arc light, heat, sparks and fume. Our PPE essentials article runs through the basics.
R
Regulator
The device fitted to a gas cylinder that reduces high bottle pressure to a safe, steady working flow, with gauges showing bottle contents and flow rate. The right regulator depends on the gas and cylinder.
S
Shade number
The darkness rating of a welding lens — a higher number is darker. The right shade depends on the process and current; most arc welding falls between shade 9 and 13. Auto-darkening helmets switch shade the instant the arc strikes.
Shielding gas
Gas that surrounds the arc and molten pool to keep air out and prevent porosity. Pure argon is used for TIG and aluminium; argon/CO2 mixes or straight CO2 for steel MIG. Our choosing shielding gas article goes deeper.
Short-circuit transfer (dip)
A low-energy MIG mode where the wire repeatedly touches the weld pool and short-circuits, giving a cooler arc. It's well suited to thin sheet and out-of-position welding.
Slag
The glassy layer that forms over a weld from the flux on MMA rods or flux-cored wire. It protects the cooling weld and is chipped and wire-brushed off before the next pass or before painting.
Spatter
Droplets of molten metal thrown from the arc that stick to the surrounding surface. Correct settings and anti-spatter spray reduce it; whatever's left is cleaned off as part of finishing.
Spray transfer
A high-energy MIG mode where fine droplets stream across the arc, giving deep penetration and very little spatter on thicker steel. It needs an argon-rich gas and is too hot for thin sheet.
Stick-out
The length of MIG wire protruding from the contact tip to the work. Keeping it consistent — roughly 10mm — keeps the arc stable and the bead even.
Stringer & weave beads
A stringer bead is run more or less straight with little side-to-side motion; a weave bead moves the torch across the joint to fill a wider gap or cap a multi-pass weld.
T
Tungsten electrode
The non-consumable electrode used in TIG welding, colour-coded by type. Green is pure tungsten for aluminium on AC; 2% lanthanated (blue) and ceriated (grey) are versatile all-rounders for steel and aluminium. The tip is ground to suit the job.
TIG / GTAW welding
Gas Tungsten Arc Welding — a precise, clean process using a non-consumable tungsten electrode with separate filler added by hand, under inert gas. It's ideal for stainless, aluminium and fine, visible work.
U
Undercut
A groove melted into the base metal at the edge of a weld that isn't then filled, leaving a weak point. It's usually caused by too much current or a poor torch angle, and is corrected by adjusting technique.
W
Wire feed speed
How fast a MIG machine feeds wire, which on most welders also sets the current. Balanced against voltage, it controls bead size and penetration — too fast stubs the wire into the work, too slow burns back to the tip.
Stuck on a term?
If a machine setting, gas or consumable label has you guessing, ask us — the people answering weld for a living and stock the kit.