TIG Welding Explained: Precision for Stainless Steel and Aluminium
Knowledge · Welding in contract manufacturing
How does TIG welding work?
The arc burns between a tungsten electrode and the workpiece. The electrode does not melt; it only carries the arc. Argon shields the weld pool. The welder guides the torch with one hand and doses filler rod with the other, controlling heat and material addition independently; exactly this decoupling creates the superior control over the pool. Steel and stainless are welded with direct current; aluminium requires alternating current, whose positive half-wave breaks up the oxide layer that melts only above 2,000 °C while the metal beneath is liquid at 660 °C.
Where is TIG unbeatable?
In four situations. Visible seams: the fine, evenly rippled TIG seam is practically spatter-free and often needs no rework on stainless frames or panelling. Thin-walled parts from about 0.5 to 6 mm. Root passes in pipework and vessels, where the TIG root is dense, low-porosity and internally smooth. And materials that forgive nothing: high-alloy stainless steels, aluminium, titanium.
Where are the limits?
Speed and cost. A TIG welder deposits roughly a third to a fifth of a MAG process. On a machine frame with many metres of fillet weld TIG would be wasted money; such structures run under MAG. TIG also demands the most manual skill of all processes, which makes EN ISO 9606 qualifications particularly meaningful here.
What does TIG mean for distortion and rework?
Heat input per second is lower than MAG, but welding time is longer; thin sheets can still distort noticeably. For distortion-critical thin sheet, hand-held laser welding is worth evaluating; the physics are explained in the article on welding distortion. On rework, TIG shines: no spatter, nothing to grind. A practical tip: instead of prescribing TIG on the drawing, specify the seam requirement (visible seam, tightness, quality level to EN ISO 5817). The manufacturer can then TIG-weld the visible seams and run the rest economically with MAG.
TIG at a glance
| Feature | Value / classification |
|---|---|
| Process number (EN ISO 4063) | 141 |
| Electrode | tungsten, non-consumable |
| Shielding gas | argon, partly argon-helium |
| Current | DC for steel/stainless, AC for aluminium |
| Typical wall thickness | approx. 0.5 to 6 mm, thicker multi-pass |
| Strengths | seam quality, visible seams, root passes, thin walls |
| Limits | speed, cost, high skill requirement |
Frequently asked questions
What does TIG stand for?
Tungsten inert gas: a tungsten electrode plus inert shielding gas. The process number to EN ISO 4063 is 141; the German term is WIG (Wolfram-Inertgas).
Why is TIG so much slower than MAG?
Because filler is fed by hand as a rod while MAG feeds an endless wire mechanically. In return, TIG offers separate control of heat and filler and thus the higher seam quality.
Is a TIG seam stronger than a MAG seam?
Not fundamentally. Properly executed, both reach the strengths required by design and standard. TIG wins on purity, low porosity and appearance, not on strength.
When should I prescribe TIG on the drawing?
Only when the requirement demands it, such as visible seams or root passes with tightness requirements. Otherwise specify the seam quality and leave the process choice to the certified manufacturer.