MIG Welding Guide: Settings, Wire, Gas and Technique for Australian Industry

MIG welding is the most widely used welding process in Australian workshops. It's fast, versatile, and produces clean welds on mild steel, stainless and aluminium. It's the go-to process for everything from automotive panels and trailer fabrication to structural steel and general maintenance work.

This guide covers everything you need to set up and run a MIG welder confidently — shielding gas selection, wire choice, voltage and wire speed settings, technique, and how to diagnose common problems. Whether you're just getting started or want to sharpen your skills, this is the reference you'll come back to.

What Is MIG Welding and How Does It Work?

MIG stands for Metal Inert Gas — the formal technical term is Gas Metal Arc Welding (GMAW). A continuous wire electrode is fed through the torch and melts into the weld pool as an electric arc forms between the wire tip and the base metal. A shielding gas — supplied from a cylinder — blankets the weld pool and protects it from atmospheric contamination.

The process is semi-automatic: the wire feeds automatically at a set speed, so the welder controls the torch position, travel speed, and angle while the machine handles the rest. This makes MIG more forgiving to learn than TIG, and considerably faster than stick welding for most applications.

Key components of a MIG welding setup

AIMS stocks a full range of MIG welding machines for Australian workshops — from compact inverter units for single-phase 240V circuits through to industrial three-phase machines for production environments. Browse MIG welders at AIMS.

Gas MIG vs Gasless MIG Welding: Which Should You Use?

This is the most important decision when setting up for MIG welding. The two approaches use completely different consumables, different machine polarity settings, and different technique. Getting them mixed up — particularly the polarity — is the single most common mistake beginners make.

Gas MIG welding (GMAW)

Gas MIG uses a solid wire electrode and an external shielding gas cylinder. The gas protects the weld pool from the atmosphere, producing clean welds with minimal spatter and no slag. It's the standard process for workshop welding on mild steel, stainless and aluminium.

• Cleaner welds, less spatter
• No slag to chip and brush off
• Better penetration and fusion on thinner materials
• Requires an upright gas cylinder — limited portability
• Outdoor use is difficult: wind disrupts shielding gas coverage
• Running cost includes gas — roughly $40–100 per cylinder fill depending on size

Gasless MIG welding (FCAW-S: flux-cored arc welding, self-shielded)

Gasless welding uses a tubular wire with a flux compound inside. When the arc burns, the flux produces its own shielding gas and leaves a slag layer over the weld bead — similar in function to the flux coating on a stick electrode. No external gas cylinder is needed.

• Truly portable — no cylinder to carry or fill
• Works in windy conditions outdoors; popular for farm and site work
• More spatter than gas MIG
• Slag must be chipped and wire-brushed between passes
• Weld appearance is rougher
• Wire cost is higher than equivalent solid wire
• Generally suited to mild steel only (most commonly available gasless wires)

Gas MIG vs gasless: at a glance

For a detailed comparison of MIG against TIG and stick welding, including process selection by application, see our MIG vs TIG vs Stick Welding guide.

Shielding Gas Selection for MIG Welding

The shielding gas affects arc stability, spatter level, bead profile, penetration depth, and weld quality. Choosing the right mix for your material and application matters — using the wrong gas produces poor results even with everything else set correctly.

Common shielding gas mixes for MIG welding

C25 (75% Argon / 25% CO₂) is the de facto standard for mild steel MIG welding in Australian workshops. Most fabrication shops run C25 exclusively for carbon steel work. Pure CO₂ is cheaper per litre but the extra spatter and cleanup time typically offset the saving in production environments.

Gas flow rates

The standard flow rate for most MIG applications is 10–15 L/min. For flat position indoor welding on thin to medium material, 10–12 L/min is adequate. Increase to 14–16 L/min for overhead or vertical positions, larger weld pools, or wider torch nozzles. Outdoors, draught shields or higher flow (16–20 L/min) may be needed — though gasless welding is a better choice in genuinely windy conditions.

Don't crank flow rate excessively. Very high flow rates (above 25 L/min) create turbulence that can actually draw air into the shielding envelope and cause porosity — the opposite of the intended effect.

Gas cylinders in Australia

Australian cylinders are supplied by BOC (Supagas), Air Liquide, and independent welding suppliers. Cylinder sizes commonly available include D (2m³), E (4m³), and G (10m³). For workshop use, an E or G cylinder on a rental agreement minimises refill downtime. Check that your regulator is appropriate for the gas mix — CO₂ and mixed gas regulators differ in outlet pressure rating.

For more information on welding consumables including gas and wire grades, see our Welding Consumables Guide.

MIG Wire Selection: Type, Alloy and Diameter

Wire selection is the second major variable after shielding gas. The wire alloy must match the base metal, and the diameter must suit the material thickness and your machine's drive roll configuration.

Solid MIG wire types

Gasless (flux-cored) wire types

Wire diameter selection

Wire diameter controls the current range your machine will run at a given wire feed speed. Thinner wire at a given feed speed draws lower current — correct for thin material. Heavier wire draws higher current for the same feed speed — better for thick material and higher deposition.

Most hobbyist and trade machines in Australian workshops run 0.8mm as the standard wire. 0.9mm is common in fabrication shops running 180–220A machines. 0.6mm requires a dedicated drive roll and is mainly used for automotive body work.

Browse MIG welding wire at AIMS — solid wire, stainless, aluminium and flux-core available in 0.6, 0.8, 0.9 and 1.2mm diameters.

Machine Setup: Drive Rolls, Liners and Contact Tips

A well-set-up machine feeds wire smoothly and consistently. Poor setup leads to erratic wire feeding, bird-nesting (wire tangling in the drive mechanism), and inconsistent arc behaviour. Get this right before adjusting voltage and wire speed.

Drive rolls

Drive rolls grip the wire and push it through the liner to the torch. The roll groove must match the wire type:

• V-groove rolls — for solid hard wire (mild steel, stainless). The groove forms a V-channel that centres the round wire.
• U-groove rolls — for soft wire (aluminium) and flux-cored wire. The rounded groove prevents deforming soft wire.
• Knurled rolls — for flux-cored wire in demanding production settings. Provides aggressive grip on the textured tube.

Drive roll tension is a balance. Too tight deforms the wire, creates shavings that clog the liner, and can cause bird-nesting. Too loose causes the wire to slip and feed intermittently. The standard test: hold a folded rag against the wire exiting the torch and increase tension until the wire feeds without slipping under moderate resistance, then back off half a turn.

Torch liners

The liner runs the length of the torch cable and guides the wire from the drive rolls to the contact tip. Liner material must match the wire:

• Steel spiral liner — for mild steel and stainless wire. Durable and cheap to replace.
• Teflon (PTFE) liner — mandatory for aluminium wire. Aluminium wire is soft and catches on steel liners, causing bird-nesting at the drive rolls. Never use a steel liner for aluminium.

Liners need periodic replacement. A kinked or clogged liner is a common cause of feeding problems. Cut the new liner slightly long and trim to the torch fitting — an undersized liner leaves an unsupported gap that catches wire.

Contact tips

The contact tip transfers current from the torch body to the wire. It must match the wire diameter exactly — a 0.8mm wire runs through a 0.8mm tip. A tip that's too large allows the wire to wander, causing arc instability and spatter. A tip that's too small causes burnbacks (the wire fuses to the tip).

Contact tips are a wear item. In production welding they're replaced regularly; in workshop use, check for elliptical wear (the bore becomes oval) and replace when arc behaviour becomes erratic or spatter increases suddenly. Always carry spare tips in the wire size you're running.

Browse MIG consumables at AIMS — contact tips, liners, nozzles and drive rolls in all common sizes.

Stick-out (contact tip-to-work distance)

Stick-out — also called CTWD (Contact Tip to Work Distance) — is the distance from the contact tip to the weld pool. The standard for solid wire MIG is 10–15mm. For flux-cored wire, 15–20mm is typical.

Longer stick-out increases electrical resistance in the wire, producing a hotter arc at the same settings. Shorter stick-out reduces resistance and cools the arc. Most beginners run stick-out too long — keep it consistent in the 10–15mm range and your settings charts will work as published.

Browse MIG torches at AIMS — 150A to 500A, push and spool gun configurations available.

Setting Wire Speed and Voltage by Material

MIG welding has two primary settings: wire feed speed (WFS) and voltage. Understanding what each controls is the key to dialling in any machine:

• Wire feed speed = current (amperage). Increasing WFS feeds more wire per second, which draws more current. Use WFS to control penetration and deposition rate. Thicker material requires higher WFS.
• Voltage = arc length. Higher voltage spreads the arc and produces a wider, flatter bead. Lower voltage makes the arc more concentrated and the bead narrower and more convex.

The two settings are interdependent. If you change WFS significantly, you'll usually need to adjust voltage to match. Most machines have a settings chart printed on the inside of the wire compartment door — use it as your starting point, then fine-tune by listening and looking.

Settings reference table — mild steel, ER70S-6, C25 gas

These figures are starting points. Your specific machine, liner length, contact tip condition, gas flow and work angle all affect the result. Always test on scrap material of the same type and thickness before committing to the job.

Australian power circuit considerations

Most Australian workshops run on single-phase 240V supply. Entry-level and mid-range MIG machines (up to approximately 180A output) run on a standard 15A circuit — the orange-plug socket common in workshops and garages. Smaller machines (up to ~130A) may run on a 10A household circuit. Check your machine's plug type and the circuit rating before purchase to avoid nuisance trips at higher outputs. Three-phase 415V supply is needed for larger industrial machines (250A+). If you're setting up a new workshop, wiring a 15A circuit is a modest investment that opens up the full range of trade-grade equipment.

MIG Welding Technique

Correct technique is what separates consistent, professional welds from erratic results with identical settings. The main variables are torch angle, travel speed, stick-out, and movement pattern.

Torch angles

Two angles define torch position:

• Work angle — the angle from vertical, measured perpendicular to the weld joint. For a flat butt weld, 90° (perpendicular) is the starting point. For a fillet weld (T-joint), 45° between the two plates. For a lap joint, 60–70° toward the vertical plate.
• Travel angle — the torch tilt in the direction of travel. For gas MIG, use a push angle of 10–15° (torch tilted forward in the direction of travel). For gasless flux-core, use a drag/pull angle of 10–15° (torch tilted back toward the completed weld).

Travel speed

Travel speed determines bead width, build-up and penetration. As a general guide:

• Too fast — narrow, undercut bead with poor fusion at the toes. The weld looks thin and ropey.
• Too slow — excessive build-up, sagging on vertical work, and burn-through risk on thin material. The pool becomes large and uncontrollable.
• Correct — the weld pool stays roughly 1.5–2× the wire diameter in diameter, and the bead width is consistent. On flat work, the leading edge of the pool stays slightly ahead of the wire tip.

Maintain a consistent pace. Stopping and restarting within a bead causes cold laps and poor fusion. If you need to reposition, stop cleanly, dress the crater, and restart slightly behind the stop point to overlap the previous bead.

Torch movement patterns

• Stringer bead — straight, no side-to-side movement. Fastest, best penetration, the default for most flat and horizontal welding. Best for multi-pass work where weave can cause inter-run contamination.
• Z-weave (zig-zag) — moves the torch in a Z-pattern to widen the bead. Useful for covering gaps or filling wide joints. Pause slightly at each edge to prevent undercut.
• C-weave / crescent weave — a looping crescent motion. Common on vertical and overhead positions where more control over the pool is needed.

Tack welding and distortion control

Always tack weld before running full beads on any joint longer than about 100mm. Tacks hold the joint in position while the full weld is run, preventing distortion caused by differential thermal expansion. For longer joints, use a backstep welding sequence — weld short segments from the finish end back to the start — to reduce cumulative distortion.

Starting and stopping

Always start and finish on the base metal, not in mid-air. Run in at the joint start and run out onto a scrap run-off tab if possible — particularly important for structural work. Fill the crater at the stop point by pausing with the trigger before releasing, or by reversing slightly into the completed weld. Unfilled craters are stress concentration points.

Welding Positions

Positional welding — anything other than flat — introduces gravity effects on the weld pool. MIG is the most forgiving process for positional work due to the continuous wire feed and consistent arc energy.

Vertical-up is the standard approach for welding vertical joints on structural steel in Australia — it produces better penetration than vertical-down for medium and heavy plate. Vertical-down (downhill) is sometimes used on sheet metal (ute trays, body panels) where travel speed and reduced heat input are beneficial.

Coded welding positions in Australian industry are qualified under AS/NZS 2980: 2007 — Qualification of welding procedures for the welding of steel, and welder qualifications under AS 2980. For structural steel work subject to inspection, welding procedures must be qualified — check with your welding inspector or fabrication supervisor.

Welding Mild Steel, Stainless Steel and Aluminium

While MIG is a versatile process, the requirements differ significantly between materials. Using the wrong wire, gas, or setup for the base metal is a guaranteed way to produce defective welds.

Mild steel

Mild steel is the most forgiving base metal for MIG welding. ER70S-6 wire with C25 gas is the standard combination for general fabrication. The main failure points are surface contamination and joint prep:

• Mill scale, rust, paint, oil and galvanising all cause porosity and inclusion defects. Remove contamination from the weld zone and the area clamped by the earth — at minimum 20–30mm either side of the joint.
• Use an angle grinder with a flap disc or grinding disc to remove scale and rust. Wire brush after grinding to remove loose particles before welding.
• For galvanised steel, remove the zinc coating from the weld zone — zinc fumes are hazardous. Work with excellent ventilation and respiratory protection, and consider the welding consumables guide for low-fuming wire options.

AS/NZS 1554.1 covers welding of steel structures in Australia, including preheat requirements for higher-carbon steels. Most common mild steel (AS/NZS 3678 Grade 250/350) requires no preheat for material up to ~25mm at ambient temperatures above 5°C.

Stainless steel

MIG welding stainless requires specific consumables and technique:

• Wire: ER308L for 304 stainless; ER316L for 316 stainless. The "L" (low carbon) grade minimises carbide precipitation (sensitisation) at the heat-affected zone.
• Gas: 98% Argon / 2% CO₂ is the standard. Tri-mix (Ar/He/CO₂) for heavier section or when faster travel speeds are needed. Never use C25 on stainless — the higher CO₂ level causes excessive carbon pickup and discolouration.
• No cross-contamination: Dedicate brushes, grinding discs and tools to stainless only. A carbon steel grinding disc on stainless embeds iron particles that cause rust staining and can compromise corrosion resistance.
• Heat input: Stainless has low thermal conductivity and is sensitive to heat. Keep travel speed up, use stringer beads where possible, and avoid letting the interpass temperature exceed 150°C (hand-warm test) between passes on multi-pass welds.

Structural stainless welding is covered by AS/NZS 1554.6. Food-grade applications (AS 4020) may impose additional requirements on consumable traceability and post-weld finishing.

Aluminium

Aluminium MIG is achievable with the right setup, but aluminium is less forgiving than steel and demands careful preparation:

• Wire: ER4043 for general welding, castings and heat-treatable alloys. ER5356 for structural joints and applications requiring better strength or where post-weld anodising is needed (ER4043 produces a darker anodised finish).
• Gas: Pure Argon — mandatory. Any CO₂ in the shielding gas causes excessive porosity and poor bead appearance on aluminium.
• Liner: Teflon (PTFE) liner — mandatory. Aluminium wire is soft and catches on steel spiral liners, causing bird-nesting at the drive rolls.
• Drive rolls: U-groove rolls, set to the minimum pressure that still feeds reliably — aluminium deforms easily.
• Spool gun: For torch cable runs over about 3 metres, a spool gun (with the wire spool mounted directly at the gun) eliminates the feeding problems that come with pushing soft aluminium wire through a long liner.
• Cleaning: Clean the weld zone with acetone or a fast-evaporating solvent degreaser, then with a dedicated stainless steel wire brush (not carbon steel). Aluminium oxide forms on the surface within minutes of cleaning — weld promptly after prep.
• Technique: Push angle only — aluminium has no slag, so there's no reason to drag. Higher travel speed than steel to keep up with the faster-moving molten pool.

Pre-heat for aluminium is sometimes used on thicker sections (above 6mm) to improve fusion and reduce cracking risk — mild preheat to 80–100°C is sufficient and can be achieved with a propane torch.

Common MIG Welding Problems and How to Fix Them

Most MIG welding defects have identifiable causes. The table below covers the problems technicians encounter most often in Australian workshops.

Duty Cycle and Machine Selection

Understanding duty cycle prevents you from damaging your machine and helps you choose the right welder for the work you actually do.

What is duty cycle?

Duty cycle is the percentage of a 10-minute cycle that a welder can operate continuously at a stated output without overheating the internal components. A machine rated at 60% duty cycle at 150A can weld continuously for 6 minutes at 150A, then must cool for 4 minutes before running again at that output.

Most hobbyist and budget MIG machines are rated at 20–30% duty cycle at maximum output. This is adequate for occasional workshop repairs and hobby use. Trade and professional machines typically offer 60–100% duty cycle at rated output, which is necessary for production welding, repetitive fabrication, and structural work where stopping to wait for the machine to cool causes unacceptable delays.

Choosing the right machine size

Inverter vs transformer MIG

Almost all new MIG welders sold in Australia are inverter-based. Inverter technology offers significant advantages over older transformer designs: lighter weight (typically 5–15kg for a trade inverter vs 40–80kg for an equivalent transformer), lower power consumption, and better arc quality on thin material due to faster electronic response. Transformer machines are still found in older workshops — they're robust and simple to service, but the performance and efficiency advantages of inverter technology make inverter the right choice for any new purchase.

Australian brands

Several brands have a strong presence in the Australian market:

• UNIMIG — Australian-owned brand with a full range from entry-level to industrial machines. Strong service network and local support. Popular in trade and fabrication workshops.
• Cigweld — Australian brand (now owned by ESAB). Long history in AU trade welding; the Weldskill and Transmig ranges are well established in Australian fabrication shops.
• Lincoln Electric — US manufacturer with strong local distribution. Invertec and Powertec ranges used in trade and structural applications.
• Fronius — Austrian manufacturer; premium industrial machines. TransSteel and TransMig ranges used in high-production and precision applications.

Browse MIG welders at AIMS Industrial — inverter and multi-process machines for single-phase and three-phase supply.

PPE and Safety for MIG Welding

MIG welding produces UV and IR radiation, molten metal spatter, harmful fumes, and significant electrical hazard. The right PPE is not optional — it's the legal baseline under WHS regulations across all Australian states and territories.

Welding helmet

A welding helmet is the primary protection against arc radiation. For MIG welding, a minimum auto-darkening filter of Shade 10 is correct for most applications. Shade 9 suits very low-amperage work; Shade 11 suits higher-amperage production welding. Auto-darkening helmets switch from a light shade (for visibility when not welding) to the dark shade in microseconds on arc strike. Fixed-shade helmets are cheaper but require lifting to see between passes.

Helmets and filters in Australia must comply with AS/NZS 1337.1 and the filter lens standard AS/NZS 1338.1. For full detail on shade selection and helmet types, see our Welding Helmet Guide. Safety glasses or goggles should be worn under the helmet at all times — spatter and scale from chipping slag can enter below the helmet when it's raised.

See also: Welding Eye Protection: Shade Guide, AS/NZS 1337 and Filter Selection

Welding gloves

MIG welding gloves are lighter and more dexterous than stick welding gloves — you need to feel the torch, not just protect from spatter. Leather MIG gloves with a reinforced palm are standard. Split-leather or goatskin for precision work on thin metal; heavier cowhide for production welding where spatter volume is higher.

Clothing

Welding generates UV that burns exposed skin rapidly — similar to extreme sunburn, even from reflected arc flash. Wear:

• Long sleeves — leather welding jacket for heavier work; flame-resistant (FR) cotton long-sleeve shirt for lighter work
• No synthetic fibres — nylon, polyester and acrylic melt onto skin under welding spatter
• Leather boots with the laces and tongue covered (spatter drops into unlaced boots)
• Denim or FR cotton trousers — no turnups where spatter can collect

Respiratory protection and ventilation

Welding fumes are a genuine health hazard. Manganese in mild steel fumes, hexavalent chromium from stainless, and zinc from galvanised steel are all classified as hazardous substances in Australia.

• For workshop welding with good natural ventilation, position yourself upwind of the fume plume and keep your head out of the fume column. Local exhaust ventilation (LEV — a fume extraction arm) is the preferred engineering control.
• For stainless welding, galvanised steel, or confined spaces: a half-face respirator with an appropriate cartridge (AS/NZS 1716) is required. P2/P3 particulate plus OV (organic vapour) combination cartridges for most scenarios.
• Never weld galvanised steel without removing the zinc from the weld zone — zinc fume causes metal fume fever (flu-like illness) and in high concentrations is acutely toxic.

Fire and electrical safety

• Remove combustible materials (rags, cardboard, timber, fuel containers) from a 10-metre radius of the weld area before starting.
• Have a dry powder or CO₂ extinguisher within reach — welding sparks can ignite materials in areas not immediately visible.
• Earth clamp placement matters for equipment safety too: on pipework, the earth clamp should be as close as practical to the weld to avoid welding current flowing through bearings, valves, or instrumentation. Keep earth leads clear of oxygen cylinder connections.
• Never weld on pressurised containers. Never weld near flammable gases or liquids without formal hot-work permit procedures.

Refer to SafeWork Australia's Code of Practice: Welding Processes for full regulatory guidance applicable in your state or territory. Browse welding safety equipment at AIMS — helmets, gloves, FR clothing, respirators and screen panels.

AIMS MIG Welding Range

AIMS Industrial stocks the full consumables and accessories range for MIG welding setups across Australian workshops and fabrication shops. Whether you're setting up a new machine or restocking consumables, we carry what you need:

• MIG welders — inverter machines for single-phase and three-phase supply, 130A to 500A
• MIG welding wire — ER70S-6, ER308L, ER316L, ER4043, ER5356, E71T-GS and E71T-11 in 0.6, 0.8, 0.9 and 1.2mm diameters
• MIG consumables — contact tips, liners, nozzles and drive rolls in all common sizes
• MIG torches — push torches and spool guns, 150A to 500A
• MIG welding accessories — earth clamps, gas regulators, hoses, anti-spatter and welding positioners
• Welding safety equipment — helmets, gloves, FR clothing, fume extraction and fire blankets

Need help selecting the right setup for your application? Talk to the AIMS team — we're welders too, and we can help you match machine, wire, gas and consumables to your specific material, position and output requirements.