MIG/MAG welding (known in Turkey as "gazaltı kaynağı", literally "under-gas welding") is a process in which an arc is formed between a wire electrode fed continuously from a spool and the workpiece, with the weld area protected by a shielding gas. In international literature it is referred to as GMAW (Gas Metal Arc Welding); in EN ISO 4063 it is designated 131 (MIG) or 135 (MAG) depending on the gas used.
Thanks to its high productivity, ease of learning and suitability for robotic automation, it is the most widely used process in industrial welded fabrication.
The Difference Between MIG and MAG
- MAG (Metal Active Gas, 135): Uses active gases such as CO₂ or Ar/CO₂ mixtures. It is the standard for carbon and low-alloy steels.
- MIG (Metal Inert Gas, 131): Uses inert gases such as argon or argon-helium. It is preferred for aluminium and other non-ferrous metals.
We explain which gas to use and when in detail in our article on shielding gas selection.
Components of a MIG/MAG Welding Machine
- Power source: A constant-voltage (CV) inverter or transformer-type machine.
- Wire feeder: Delivers the wire to the torch at the set speed; wire feed speed determines the welding current.
- Torch and cable assembly: Carries the wire, current and gas to the weld area.
- Gas cylinder and regulator: Sets the gas flow rate (typically 12–18 l/min).
Metal Transfer Modes
| Transfer Mode | Current / Voltage | Use |
|---|---|---|
| Short-circuit (dip) | Low | Thin sheet, root passes, all positions |
| Globular | Medium | Generally undesirable; high spatter |
| Spray arc | High | Thick sections, horizontal and flat positions, high deposition |
| Pulsed | Variable | Aluminium, stainless steel, low heat input and minimal spatter |
How Is MIG/MAG Welding Done?
- Wire and gas selection: For structural steel, G3Si1 (SG2) wire and M21 (Ar/18% CO₂) gas are generally used.
- Parameter setting: Wire feed speed (current), voltage and gas flow rate are set according to material thickness. For detailed values, see our article on MIG/MAG welding parameters.
- Stick-out: The distance between the contact tip and the workpiece is generally kept at 10–15 mm.
- Torch angle and direction: A 10–15° push angle gives a flatter, wider bead; a drag angle gives deeper penetration.
- Inspection: The weld is checked by visual inspection; NDT is applied on critical work.
Advantages and Limitations
| Advantages | Limitations |
|---|---|
| High welding speed and deposition rate | Outdoors, wind disrupts the gas shield |
| No slag, minimal cleaning | Torch size can make access difficult in tight spaces |
| Highly suited to robotics and automation | Risk of lack of fusion if set incorrectly |
| Can be used on steel, stainless steel and aluminium | Equipment is more complex than for stick welding |
Common Defects
- Porosity: Insufficient or excessive gas flow, contaminated surfaces, draughts.
- Lack of fusion: Low voltage, fast travel speed or incorrect torch angle; particular care is needed with short-circuit transfer.
- Excessive spatter: Imbalance between voltage and wire feed speed, or a high CO₂ content.
- Undercut: Excessive current and voltage.
For defect types and their repair, see our article on welding defects.
At ArmaWeld: We apply MAG and robotic MAG welding to chassis, structural steelwork and machine parts under approved WPSs. For series work, robotic welding delivers repeatable quality and short cycle times.
Frequently Asked Questions
Which gas is used in MIG/MAG welding?
For structural steels, the most common gas is a mixture of argon and 15–25% CO₂ (EN ISO 14175 M21). 100% CO₂ is more economical but increases spatter. Pure argon is used for aluminium.
What is the difference between MIG/MAG welding and stick welding?
In MIG/MAG welding the wire is fed continuously and shielded by gas; it is faster and produces no slag. Stick welding can be done with simpler equipment, even on windy sites, but it is slow and slag must be removed after each electrode.
What does wire feed speed determine in MIG/MAG welding?
On constant-voltage machines, wire feed speed determines the welding current. As wire feed speed increases, current and deposition rate rise; voltage, meanwhile, affects arc length and bead width.
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