MAG, MIG, TIG or Laser? Welding Processes Compared
Knowledge · Welding in contract manufacturing
How do the processes differ in principle?
All four join metal by local melting; they differ in energy source and filler. In MAG welding (process 135, metal active gas) and MIG welding (process 131, metal inert gas) the arc burns between a continuously fed wire electrode and the workpiece; the wire is also the filler. MAG uses active shielding gas (CO₂ or mixed gas M21 with 82 % argon / 18 % CO₂), MIG uses pure inert gas such as argon. In TIG welding (process 141, tungsten inert gas) the arc burns on a non-consumable tungsten electrode and filler rod is fed by hand. In hand-held laser welding a fibre laser replaces the arc and concentrates the energy on a spot below one millimetre.
When is MAG the right choice?
Whenever steel needs joining economically with high deposition rates. MAG achieves several kilograms of weld metal per hour and is unbeatable on structural steels (S235, S355) and thicker plate. Load-bearing structures to EN 1090-2 are welded almost exclusively with MAG. Its limits: more spatter than TIG, rougher seam appearance, unsuitable for aluminium.
When MIG instead of MAG?
As soon as non-ferrous metals are involved. Under pure argon, aluminium, copper and brass weld cleanly and without oxidation. For steel MIG offers no advantage and is practically never used.
Where does TIG earn its money?
Wherever seam quality outranks speed: visible seams, thin-walled parts from about 0.5 to 6 mm, root passes in pipework and vessels, and demanding materials such as stainless steel and titanium. The price is speed: TIG is several times slower than MAG and demands the most manual skill.
What can hand-held laser welding do that the others cannot?
Combine low heat input with high travel speed: a narrow heat-affected zone, far less distortion, and clean narrow seams on visible parts that often need no grinding. Its sweet spot is thin sheet up to about 4 mm, stainless visible parts and housings. It does not replace the classic processes: thick sections and EN 1090 structures remain MAG and TIG territory.
The decision table
| Criterion | MAG (135) | MIG (131) | TIG (141) | Hand-held laser |
|---|---|---|---|---|
| Shielding gas | active (CO₂, M21) | inert (argon) | inert (argon) | argon / crossjet |
| Ideal materials | structural & fine-grain steel, stainless | aluminium, copper, brass | stainless, aluminium, special alloys | stainless, steel, thin sheet |
| Typical thickness | from ~0.8 mm, unlimited multi-pass | from ~1 mm | ~0.5 to 6 mm | ~0.5 to 4 mm |
| Speed | high | high | low | high |
| Seam appearance | good, some spatter | good | excellent | excellent, narrow |
| Distortion tendency | medium to high | medium | medium | low |
| Typical use | frames, EN 1090 steelwork | aluminium assemblies | visible seams, pipes, vessels | visible parts, housings, thin sheet |
How do you decide in a specific case?
Ask in this order: material (aluminium rules out MAG, plain steel makes MIG pointless), seam requirement (load-bearing, tight, visible?), sheet thickness and distortion sensitivity, then quantity. A practical tip: do not prescribe the process on the drawing unless a standard requires it. Specifying the seam via EN ISO 5817 quality level leaves the manufacturer free to choose the most economical process.
Frequently asked questions
What is the difference between MIG and MAG?
The shielding gas and therefore the application: MAG uses active CO₂-bearing gas for steel, MIG uses inert argon for aluminium and other non-ferrous metals. Equipment and principle are identical.
Which welding process is best for stainless steel?
TIG or hand-held laser for visible seams and thin walls, MAG with low-CO₂ mixed gas for load-bearing stainless structures with larger sections. Seam requirement and thickness decide.
Can aluminium be MAG-welded?
Practically no. Active gas causes porosity and an unstable process on aluminium. Aluminium is MIG- or TIG-welded, thin parts also with the hand-held laser.
Who may weld load-bearing structures?
Companies certified to EN 1090-1 with welders qualified to EN ISO 9606-1 under a qualified welding coordinator. Execution class EXC 2 is the usual standard in mechanical and structural engineering.