"Should this job be MIG or TIG?" It is the most-asked question on the shop floor and the one most often settled by habit rather than process logic. The two are not substitutes; they represent a trade-off between productivity and quality. MIG/MAG wins on deposition rate and speed, TIG wins on bead appearance, precision and material flexibility. This article settles the choice with a parameter table, a cost model and eight representative applications.
1. The fundamental difference
| Item | MIG/MAG (GMAW) | TIG (GTAW) |
|---|---|---|
| Electrode | The wire itself is a consumable electrode, fed continuously | A tungsten electrode that does not melt; filler is added by hand or by a separate feeder |
| Shielding gas | CO2, or Ar+CO2 / Ar+O2 mixes | Pure argon, or argon-helium and argon-hydrogen mixes |
| Deposition rate | High — typically 3–8 kg/h | Low — typically 0.5–1.5 kg/h |
| Thickness range | From 1 mm up; efficient multi-pass on thick plate | From 0.5 mm; unbeatable on thin plate and root passes, inefficient on thick plate |
| Operator skill | Lower — quick to learn, suited to volume production | Higher — requires two-hand coordination and steady arc length |
| Spatter | CO2 short-circuit transfer spatters; pulse and spray transfer barely do | Essentially none |
| Bead appearance | Good, but with visible reinforcement and possible undercut | Excellent — even ripple pattern, usually needs no grinding |
| Heat input control | Fair | Excellent; pulsed current controls heat input precisely |
In one line: MIG/MAG is the process for putting metal down; TIG is the process for joining metal precisely.
2. The cost model: which is actually more expensive
Most people assume TIG costs more, but the real structure is worth unpacking. Take 10 m of weld on 6 mm carbon steel:
| Cost item | MAG (Ar+CO2, 1.2 mm wire) | TIG (pure argon, 2.4 mm filler) |
|---|---|---|
| Arc time | about 22 min | about 75 min |
| Labour (at 60 CNY/h) | 22 CNY | 75 CNY |
| Filler metal | 1.1 kg, about 11 CNY | 0.6 kg, about 18 CNY |
| Shielding gas | about 8 CNY | about 25 CNY |
| Post-weld grinding | 15–25 min, about 20 CNY | almost none, about 3 CNY |
| Total per part | about 61 CNY | about 121 CNY |
Conclusion: on carbon steel above 6 mm, MAG costs roughly half of TIG all-in. Switch to a 2 mm stainless cosmetic panel, though, and TIG's advantage in rework and grinding pulls the gap back and can even reverse it — because MAG on thin sheet burns through and distorts very easily.
3. Eight representative applications
| Application | Recommended process | Why |
|---|---|---|
| Carbon steel fabrications above 6 mm, steel structures, agricultural machinery | MAG (Ar+CO2 mix) | Productivity first, lowest cost |
| 3–6 mm plate where appearance matters | Pulsed MAG | Almost no spatter and a near-TIG bead, without giving up speed |
| Sheet below 2 mm, stainless worktops | DC pulsed TIG | Controlled heat input, no distortion or burn-through |
| Pipe root passes, single-side welding with two-sided formation | TIG root + MAG fill and cap | The industry standard combination — quality and output together |
| Aluminium | AC TIG, or MIG with a push-pull gun | Aluminium needs AC oxide cleaning; thick aluminium is faster with MIG |
| Titanium, copper, nickel alloys | TIG | Shielding requirements are extreme and TIG back-purging is more reliable |
| Multi-pass thick plate above 20 mm | MAG or submerged arc | TIG deposition is too low to be economical |
| Repair, one-offs, all-position work | MMA (stick) or TIG | Simple equipment, flexible position capability |
4. Is pulsed capability worth the money
This is the most common question at purchase time. Pulsed MIG/MAG — such as the Icyrobot NBM-350D single-pulse and 350DP double-pulse units — switches between peak and background current to give spatter-free metal transfer at lower average heat input. Three signals that it pays for itself:
- Your work is mostly 2–6 mm sheet, where conventional short-circuit transfer spatters badly and grinding is expensive.
- Welds go straight to painting or are visible on the finished product, so spatter must be removed.
- Stainless or aluminium make up a large share of your work, where heat input drives distortion.
If you weld nothing but 8 mm-plus carbon steel that gets machined afterwards, a conventional NB-350A or NB-500A is enough — do not pay for pulse you will never use.
5. Getting the gas right
- Pure CO2 — cheapest, deepest penetration, but heavy spatter and a rough bead. Fine for filling thick plate where appearance does not matter.
- Argon + 20% CO2 — the general-purpose carbon steel mix. Much less spatter and a good bead; the usual compromise.
- Argon + 2–5% O2 — common for stainless and low-alloy steel; stable arc and good wetting.
- Pure argon — standard for TIG. Used for MIG on aluminium; on carbon steel it causes arc wander and undercut.
- Argon + helium — for thick aluminium and copper, adding heat input and penetration.
One reminder: more flow is not better. Outdoors or in draughts, shield the area and run 20–25 L/min; indoors 12–18 L/min is normally enough. Excessive flow turns turbulent and pulls air in, which causes the very porosity you were trying to prevent.
6. Frequently asked questions
What is the difference between MIG and MAG?
It comes down to the shielding gas. MIG uses inert gas (argon, helium) and is used mainly for aluminium, copper and stainless. MAG uses active gas (CO2 or CO2/O2 mixtures) and is used mainly for carbon and low-alloy steel. The equipment is largely the same, which is why both are usually called gas metal arc welding.
Is TIG too slow for thin sheet?
On thin material the heat input ceiling is low anyway, so MAG has to run at reduced parameters with skip welding, which erodes its speed advantage. Add TIG's near-zero grinding and rework, and overall cycle time is often no worse. For cosmetic stainless below 3 mm, TIG usually ships faster.
Can one machine do both MIG and TIG?
Some multi-process inverters can, but TIG needs HF or lift start with pre-flow and downslope control, while MIG needs a wire feeder and constant-voltage characteristics — different demands on the power source. If you run a lot of both, buy two machines: see our MIG/MAG welders and TIG welders.
Why is my MAG weld porous?
Work through it in order: gas flow and leaks in the line (the most common cause), rust, oil or galvanising on the work, excessive stick-out, a blocked nozzle causing turbulent shielding, or draughts above 2 m/s. Galvanised steel must have the coating ground off and the area well ventilated.
Conclusion
The decision rule is simple: thick plate, volume, cost-sensitive — MAG; thin sheet, cosmetic, exotic materials — TIG; both — run two machines, or TIG root plus MAG fill. Icyrobot builds the full gas-shielded range from the NB-350A to the double-pulse NBM-350DP, alongside DC pulsed TIG and AC/DC TIG sets. For a configuration matched to your actual parts, talk to our engineers. Welding procedure and qualification references are published by the American Welding Society.
