MIG Welder Buying Guide NZ: Choosing a MIG Welder and MIG Wire

The right MIG welder comes down to four things: whether you'll weld with shielding gas or gasless flux-cored wire, how thick the metal is, how long you'll weld without a break (duty cycle), and what power supply you have. Choose the machine first, then match the MIG wire, gas and consumables to it. A wire that suits the job but doesn't suit the machine, or the other way round, gives poor welds.

What a MIG welder does

A MIG welder feeds a continuous wire electrode through a torch. The wire melts into the joint while the machine holds a steady arc. Because the wire feeds itself, MIG is quicker to learn than stick (MMA) or TIG, and it's the usual choice for fabrication, farm repairs, trailers and general workshop work. Many current machines are multi-process inverters that do MIG, stick and lift-arc TIG from one box.

Gas vs gasless (flux-cored) MIG

Gas MIG runs solid wire. A bottle of shielding gas protects the weld pool from the air. It gives clean welds with little slag and is the standard for indoor fabrication on steel, stainless and aluminium.

Gasless MIG runs flux-cored wire. The flux inside the wire does the shielding, so you don't need a bottle. Weldco's gasless wire listing describes it as ideal for welding outdoors, where gas would blow away. There is slag to chip off afterwards. Gasless wire also usually runs on reversed polarity. Hugong's TekMaster MIG 200 listing, for example, notes reversible polarity for gasless MIG welding, so check that your machine can switch.

Many machines do both. If you'll weld in the shed and also out in the paddock, a gas/gasless machine is the flexible choice.

Amperage and material thickness

More amps let you weld thicker metal in one pass. Don't rely on a rule of thumb. Use the maker's figures: Weldco lists its MIG160 as handling material up to 6mm thick and its MIG200 up to 10mm. Also look at the bottom of the current range. A machine that turns down low is easier to use on thin sheet and panel work.

For a hobby or home workshop, a machine in the 120-160 amp class covers light repairs and sheet. A 200 amp machine gives headroom for trailers, brackets and heavier fabrication. Above that you're into workshop and production machines.

Duty cycle explained

Duty cycle is the share of a set test period that a machine can weld at a given current before it has to stop and cool. It's written as a percentage at an amperage. For example, Hugong lists the TekMaster MIG 200 at 60% at 200A. Duty cycle is higher at lower currents, so a machine you mostly use well below its maximum will rarely trip its thermal overload. Short repair welds hardly test duty cycle. Long seams and production runs do. Compare machines on their own published figures, and treat a missing figure as a question to ask, not a pass.

230V single-phase vs 3-phase

Most home and site machines run on a standard 230V single-phase supply. Some run on an ordinary 10 amp plug: Weldco's MIG120 and MIG160 both say so. Bigger single-phase machines can draw more current, so check the maximum input current on the spec plate against your circuit before you buy. The TekMaster MIG 200 lists 230V input and a 36A maximum input current.

Three-phase machines suit workshops with a 400V supply. They're built for long runs at high current. Hugong's MIG/STICK 250 is a three-phase, 400V trolley machine with a 4-roll drive. If you only have single-phase power, a three-phase machine isn't an option without an electrician's help.

Comparison: MIG welders in stock

MIG wire: types, diameters and matching gas

Match the wire to the metal you're welding. Then match the gas to the wire.

• ER70S-6 (mild steel, gas). The everyday steel wire. DUROARC ER70S-6 MIG Wire (AWS A5.18 ER70S-6) is copper coated and all-positional. It's listed for straight CO2 or an argon/CO2 mix. It comes in 0.6mm to 1.6mm, on 5kg and 15kg spools.
• Flux-cored (gasless). Duralloy Gasless Flux Cored Wire comes in 0.8mm, 0.9mm and 1.2mm, on 1kg and 5kg spools. No gas is needed.
• Stainless. DUROARC 316LSI Stainless MIG (AWS A5.9 ER316LSi) is listed for 316 and 316L stainless. Recommended gas is 98% argon/2% CO2 or 95% argon/5% CO2, and argon-helium can also be used.
• Aluminium. DUROARC 5356 MIG (AWS A5.10 ER5356) is a 5% magnesium alloy for cast, wrought and extruded aluminium alloys, including ramps, ladders, handrails and marine work. Use it with 100% argon or an argon-helium mix. Aluminium wire is soft, so it's normally fed with a spool gun or with aluminium-specific drive rollers and liner.

Diameter: thinner wire suits thinner metal and lower currents. Thicker wire suits heavier work at higher amps. Whatever you choose has to sit inside your machine's wire-feed range. The drive rollers, contact tip and liner all have to match the wire size too.

Consumables: tips, nozzles and liners

• Contact tips carry the current to the wire and wear with use. Buy them sized to your wire. Bernard Centerfire MIG Tips come in 0.9mm to 1.6mm models. Make sure the tip style matches your torch.
• Nozzles direct the shielding gas. Spatter build-up disturbs the gas flow, so keep them clean. Nozzle dip compound applied before welding reduces spatter build-up.
• Liners guide the wire through the torch lead. Our steel liners are colour coded by wire size: blue for 0.6-0.9mm, red for 1.0-1.2mm and yellow for 1.6mm. Aluminium liners are separate. A kinked or worn liner causes erratic wire feed.
• Drive rollers come knurled for flux-cored wire and in aluminium-specific types for aluminium wire. Use the type and groove size that match your wire.

How to choose by job

• First welder, light repairs, no gas bottle: a gasless machine on a 10 amp plug, such as the Weldco MIG120, with flux-cored wire.
• Home workshop, gas and gasless: the Weldco MIG160 for material up to 6mm, or the MIG200 for up to 10mm.
• Site and mixed metals: the Hugong TekMaster MIG 200. It runs on single phase, is spool gun capable for aluminium, and adds stick and lift TIG.
• Three-phase workshop: the Hugong MIG/STICK 250 for longer runs at higher current.

FAQ

Which MIG wire should I use for mild steel?

ER70S-6 solid wire with CO2 or an argon/CO2 mix is the common choice when you have gas. If you don't, use a gasless flux-cored wire and set the machine to the polarity its manual gives for flux-cored wire.

Is gasless MIG as good as gas MIG?

Each has its place. Gasless is handy outdoors and away from a bottle. Gas MIG gives cleaner welds with no slag and is the choice for stainless and aluminium.

What size welding wire do I need?

It depends on material thickness and your machine's wire-feed range. Pick a size your machine handles, and buy contact tips, liner and drive rollers to match.

Can I MIG weld aluminium with any welder?

You need a machine set up for it. That usually means a spool gun or aluminium rollers and liner, 5356 (or similar) aluminium wire and pure argon. Check the machine's listing says it handles aluminium.

Browse the full range in welding machines, welding and the Duroweld range.