A Beginner's Guide to MIG or Metal Inert Gas Welding
August 24, 2022
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A Beginner's Guide to MIG or Metal Inert Gas Welding

MIG welding is one of the most widely used welding processes in the world — accounting for more than 50% of all welded metal produced globally. Its combination of versatility, speed, ease of use, and suitability for automation has made it the standard process across automotive manufacturing, structural fabrication, shipbuilding, and general engineering. This guide explains what MIG welding is, how it works, the different metal transfer modes, key components, and the advantages and limitations of the process.

What Is MIG Welding?

MIG welding (Metal Inert Gas welding) is an arc welding process that fuses metals together using a continuously fed consumable wire electrode shielded by an inert gas. It is one of two sub-types of Gas Metal Arc Welding (GMAW) — the other being Metal Active Gas (MAG) welding. The distinction comes from the type of shielding gas used: inert gas (such as argon) for MIG, active gas (such as CO₂ or argon/CO₂ mixtures) for MAG. The process and equipment are otherwise the same. The choice of shielding gas depends on the metals being welded and the transfer mode being used.

MIG welding was developed in 1948 by the Battelle Memorial Institute and patented in 1949. In the decades since, advances in power source technology — particularly pulse MIG and synergic control — have significantly extended its capability and range of applications.

What Metals Can Be MIG Welded?

MIG welding works on almost all conductive metals, including mild steel, stainless steel, aluminium, copper, magnesium, bronze, and nickel alloys. It is suitable for most material thicknesses — from thin sheet through to heavy plate — although the transfer mode, filler metal, and shielding gas must be matched to the material and thickness. For aluminium-specific MIG welding guidance, see our article on aluminium MIG troubleshooting and our aluminium filler alloy selection guide.

How MIG Welding Works

When the torch trigger is pressed, three things happen simultaneously:

  • Welding wire is fed from the spool through the liner to the contact tip at a pre-set speed
  • An electrical arc is created between the wire and the workpiece, melting both the wire and the base material to form the weld pool
  • Shielding gas flows from the nozzle surrounding the contact tip, protecting the molten weld pool from atmospheric oxygen and nitrogen

The joint is formed as the weld pool solidifies — a mixture of the filler wire and the melted base material. The operator moves the torch along the joint at a controlled travel speed, depositing the weld bead. The quality of the result depends on the correct combination of wire feed speed, voltage, travel speed, torch angle, and shielding gas selection.

Metal Transfer Modes

The method by which the filler wire is transferred into the weld pool varies with voltage, current, shielding gas, and wire diameter. The transfer mode directly affects penetration profile, spatter level, positional capability, and material thickness range. There are four principal transfer modes:

Short circuit (dip transfer)

The wire feed speed is set so that the wire physically touches the weld pool, creating a short circuit that melts the wire tip and deposits metal in the pool. This cycle repeats 20–200 times per second. Short circuit transfer is a low-voltage, low-heat-input method — all positional, and the correct choice for thin materials and positional work where heat input must be minimised. Typical shielding gas is 75–85% argon / CO₂.

Globular transfer

A continuous arc is maintained and metal transfers as large droplets — larger in diameter than the wire itself. Globular transfer requires high heat input and produces significant spatter. Because the droplets fall by gravity, it is limited to flat and horizontal positions. Typical shielding gas is pure CO₂, making it the lowest-cost transfer mode, but post-weld cleaning requirements can offset this advantage.

Spray transfer

At high voltage (typically above 25 V for 1.2 mm wire) and wire feed speeds giving more than 250 A, the arc burns continuously and metal transfers as a fine spray of small droplets. Spray transfer produces clean, aesthetically good welds with low spatter and good penetration. It is limited to flat and horizontal positions on most materials, though it can be used positionally on aluminium. Typical shielding gas is high-argon mixture (80% Ar or above).

Pulse transfer

Pulse transfer requires a pulse MIG power source. The output alternates between a background current (which maintains the arc without transferring metal) and a peak current (during which spray transfer occurs). The average current is below the threshold normally required for spray transfer, giving a smaller weld pool that can be controlled in all positions. Pulse MIG produces clean welds with minimal spatter and a reduced heat-affected zone, and is suitable for thin and thick materials alike. Typical shielding gas is argon or high-argon mixture. For heavy industrial applications, see our article on pulse MIG technology in heavy industrial welding.

Transfer Mode Heat Input  Positions Spatter Typical Application
Short circuit / dip Low All positions Low–medium Thin sheet, positional welding
Globular High Flat/horizontal only High Low-cost structural welding
Spray High Flat/horizontal only Very low Thick section, high deposition
Pulse Controlled All positions Minimal Thin to thick, quality-critical


Key MIG Welding Components

Wire electrode and filler metal

The wire electrode serves as both the arc source and the filler metal for the joint. It is fed through a copper contact tip in the torch, which conducts current into the wire. Wire diameter typically ranges from 0.8 mm to 1.6 mm depending on the material thickness and transfer mode. The filler metal must be compatible with the base material — generally matching in alloy type — and the mechanical properties of the weld metal should meet or exceed the base material requirements. For filler metal selection guidance, see our welding consumables selection guide. ESAB's OK AristoRod range covers the full spectrum of mild and low-alloy steel MIG wire requirements.

Shielding gas

The shielding gas protects the molten weld pool from atmospheric oxygen and nitrogen. The three most common gases are argon, helium, and CO₂, used individually or in mixtures. The correct gas selection depends on the base material, transfer mode, and required weld properties. For detailed shielding gas guidance, see our article on shielding gas management in wire welding. For aluminium, see our article on argon vs helium for aluminium welding.

Welding torch

The MIG torch carries the welding current, wire, and shielding gas to the weld joint. The contact tip guides the wire and conducts the welding current — it is a consumable that requires regular replacement. Nozzle condition, contact tip bore diameter, and liner integrity all directly affect arc stability and weld quality. For torch consumable guidance, see our article on nozzle selection for MIG welding. For heavy industrial applications, ESAB's RobustFeed Edge with the PP 350W Inline Push-Pull torch delivers best-in-class feeding performance for demanding applications.

Power source

MIG welding uses a constant-voltage (CV) power source, which maintains a relatively stable arc voltage regardless of variations in arc length. The wire feed speed controls the welding current — faster feed speed gives higher current. Power source selection depends on material thickness, material type, duty cycle requirements, and the transfer modes required. For heavy industrial MIG welding, ESAB's Warrior Edge 500 DX and Aristo 500ix deliver the full range of MIG transfer modes including advanced pulse and SPEED WeldMode. For wire feeding in production environments, see our article on wire feeders in heavy industrial welding.

Advantages of MIG Welding

  • Versatility — suitable for most metals, material thicknesses, and welding positions (depending on transfer mode). The most widely applicable arc welding process
  • High productivity — continuous wire feed eliminates the stop-start of stick welding electrode changes, increasing arc-on time and deposition rate
  • Automation capability — MIG welding can be readily mechanised or fully automated. More than any other process, MIG welding lends itself to robotic and automated applications. See our ESAB robotic welding solutions
  • Good weld appearance — minimal spatter (particularly in pulse and spray transfer modes) and a clean, consistent bead profile reduce post-weld cleaning and finishing time
  • Ease of use — the continuous wire feed and automatic shielding gas control make MIG welding accessible to less experienced operators more quickly than TIG or stick welding

Disadvantages of MIG Welding

  • Burn-through on thin materials — globular and spray transfer modes can burn through thin base metals. Short circuit or pulse transfer should be used for thin sheet
  • Lack of fusion risk — more prevalent in thicker materials when heat input is insufficient for the joint geometry. Spray or pulse transfer is recommended for thicker sections to ensure adequate sidewall fusion
  • Shielding gas dependency — the requirement for shielding gas increases consumable cost (particularly when high-argon mixtures are specified) and limits outdoor use where wind can displace the gas shield. For outdoor or site welding applications, flux-cored wire may be a better choice
  • Positional limitations — globular and spray transfer modes are limited to flat and horizontal positions. Pulse or short circuit transfer is required for positional work

MIG Welding Applications

MIG welding is the primary welding method in global manufacturing — used across automotive production lines, structural fabrication, shipbuilding, pressure vessel manufacture, pipeline welding, and general engineering workshops. Its suitability for automation makes it the dominant process in high-volume production environments, where robotic MIG welding systems deliver consistent quality at speeds and duty cycles that manual welding cannot match.

ESAB MIG Welding Equipment and Consumables

  • Warrior Edge 500 DX — advanced multiprocess MIG power source with Pulse, SPEED, THIN, ROOT, and CRAFT WeldModes
  • Warrior CC/CV — heavy industrial multiprocess welder for daily production MIG welding
  • Aristo 500ix — portable heavy industrial pulse MIG power source for precision and complex applications
  • RobustFeed Edge — wire feeder with TrueFlow digital gas control and PreciDrive precision wire drive
  • OK AristoRod 12.50 — non-copper-coated solid MIG wire for structural and general fabrication steels
  • OK Tubrod 15.14 — all-positional rutile flux-cored wire for mild steel

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