MIG, MAG, TIG: which welding process for which part?
MIG, MAG, TIG, stick welding: how each arc welding process works, its strengths, its limits and the parts for which it is the right choice.
MIG, MAG, TIG: three acronyms heard in every workshop, often used interchangeably. Yet they are different processes that do not suit the same parts. Here is how they work and how to choose.
What they have in common: the electric arc
All three processes belong to arc welding: an electric arc between an electrode and the workpiece melts the metal. A shielding gas protects the weld pool from the air, whose oxygen and nitrogen would degrade the weld. What sets them apart: the type of electrode and the type of gas.
ISO 4063 assigns a number to each process, which you will find in welding procedure specifications:
| Process | ISO 4063 number | Electrode | Gas |
|---|---|---|---|
| MIG | 131 | consumable wire | inert (argon, helium) |
| MAG | 135 | solid consumable wire | active (argon + CO₂ mix, or CO₂) |
| MAG flux-cored | 136 | flux-cored wire | active |
| TIG | 141 | non-consumable tungsten | inert (argon) |
| Stick (MMA) | 111 | coated electrode | produced by the coating |
MIG and MAG: the wire that feeds itself
In MIG and MAG, the electrode is a metal wire fed continuously by a wire feeder, which melts and forms the filler metal. The welder, or the robot, only has to guide the torch: it is a fast, productive process that is easy to automate.
The only difference between the two is the gas:
- MIG (Metal Inert Gas) uses an inert gas that does not react with the pool. It is the process for aluminium and some non-ferrous alloys.
- MAG (Metal Active Gas) uses an active gas containing CO₂ (and sometimes oxygen). It stabilises the arc and improves penetration on steels. It is by far the most widespread process in steel fabrication.
In everyday language, people often say “MIG” when they mean MAG on steel. That does not matter in the workshop, but on a welding procedure, the distinction counts.
Strengths: high productivity, relatively quick to learn, suitable for all common thicknesses, ideal for automation. Limits: spatter to control, a less refined bead appearance than TIG, sensitive to draughts (the gas can be blown away).
TIG: precision
In TIG (Tungsten Inert Gas), the arc comes from a tungsten electrode that does not melt. The filler metal, when used, is added separately as a rod held in the welder’s other hand. The gas is inert, usually argon.
Strengths: very clean, precise welds with no spatter, excellent control of the pool; suited to thin material, stainless steel, aluminium, visible parts and demanding root runs. Limits: much slower than MIG/MAG and requires great dexterity, hence a highly qualified welder.
Stick welding
The oldest process: a metal rod surrounded by a coating which, as it burns, produces the gas shield and a slag. No gas bottle, simple equipment: it is the process of outdoor sites and repairs. With low productivity, it is rarely used in series production.
How to choose?
| Your part | Most common process |
|---|---|
| Structural steel, common thicknesses, series | MAG (135) |
| Aluminium | MIG (131), TIG (141) for thin or visible parts |
| Stainless steel, visible parts, thin material | TIG (141) |
| Thick material, high deposition rate | MAG flux-cored (136) |
| Outdoor site, repair | stick (111) |
And at Newstack Robotics?
Our robotic cell welds structural steel parts with MAG. It is the most widespread process-material combination in welded fabrication, and the one best suited to automation. No stainless steel, aluminium or TIG for now: our technical capabilities page sets out the scope.
Key takeaways
MIG and MAG are the same consumable-wire process, with an inert gas for aluminium (MIG) or an active gas for steel (MAG). TIG, slower and more precise, is reserved for thin parts, stainless steel and visible welds. For steel parts in series, MAG remains the reference choice. The technical terms in this article are defined in our welding glossary.