MIG welding: settings, gas, wire and fixes

Q: What wire should I start with for MIG welding?

For mild steel, .030 in (0.8 mm) or .035 in (0.9 mm) solid ER70S-6 covers most garage work, from thin sheet up to about 3/16 in (4.8 mm). Auto body panels usually call for .023 in (0.6 mm) wire.

Q: Can I MIG weld without gas?

Only with self-shielded flux-cored wire (such as E71T-11 or E71T-GS), which carries its shielding inside the wire. It spatters more, leaves slag, makes more fume and usually runs with the gun on electrode negative.

Free guide · The Welder's Forge · updated September 2026

MIG is the process most home shops and fab shops reach for first. The wire feeds itself through the gun, you never stop to change a rod, and the bead comes out clean with no slag to chip. The trade-off is a machine with more settings, and that is where most beginners get lost. The guides below take them one at a time.

Quick answer

On a MIG welder you set three things: voltage (V), wire feed speed (inches per minute, which controls amperage) and gas flow (CFH). For mild steel, a common starting point is .030 in (0.8 mm) solid ER70S-6 wire, 75/25 argon/CO₂ gas and the gun on electrode positive (DCEP). Confirm against your machine manual.

Where to start

New machine in the box? Power, spool, drive rolls, gas, polarity and a first bead, in the right order: how to set up a MIG welder.
Not sure how many volts? The MIG welding settings chart gives voltage, wire speed and gas flow by metal thickness.
CO₂, 75/25 or argon? Each gas has a job, and pure argon is not for steel. See MIG welding gas compared.
Machine with no gas hookup? It runs self-shielded flux-cored wire, with different polarity and technique: gasless MIG explained.
Worn parts, wire that will not feed? Start with the MIG contact tip.
Pinholes or an ugly bead? Read weld porosity and common welding defects to find the cause by how the bead looks.

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The transfer modes in one table

How the wire melts into the puddle changes with voltage. Most auto body and light fabrication work is done in short-circuit transfer, which sounds like bacon frying.

Mode	Voltage	Spatter	Positions	Typical use
Short-circuit	15–22 V	Medium	All	Thin sheet, auto body, out of position
Globular	22–27 V	Heavy	Flat	Transition range, typical with pure CO₂
Spray	27–35 V	Almost none	Flat	Thick plate, production
Pulsed	Variable	Minimal	All	Special alloys, high quality work

Table 4.1 of the e-book The Welder's Forge.

MIG or MAG?

Same machine, same gun. With an inert gas (argon) it is technically MIG, used on aluminum and other nonferrous metals. With CO₂ or 75/25 it is MAG (active gas), which is almost all steel work. US shops say "MIG" for both. Still choosing a process? Compare MIG vs TIG welding.

These pages are reference material. They do not replace hands-on training with someone who can watch your technique, and anything that carries a load deserves a qualified person's review.

Guides on this topic

MIG welding settings chart: voltage, wire speed and gas flowWire size, thickness, voltage, wire speed and gas flow Gasless MIG welding (flux-core): when it worksSelf-shielded flux-core wire: when it pays off and when not MIG welding gas: 75/25, CO₂ or argon?75/25, CO₂ or argon: which to use and what flow rate How to set up a MIG welder step by stepPower, spool, wire, gas, polarity and your first bead Weld porosity: causes and fixes for pinholesFind the cause of pinholes in MIG, flux-core and stick welds MIG contact tip: size, wear and replacementTip, diffuser, nozzle and drive rolls: what to change and when Common welding defects and how to fix themUndercut, porosity, lack of fusion, spatter and cracks

Frequently asked questions

Is MIG welding good for beginners?

It is usually the fastest process to learn for an acceptable bead, because the wire feeds itself and you only control the gun. The real challenge is the settings, which you learn on scrap steel by changing one setting at a time.

What is the difference between MIG and MAG?

Only the gas. MIG uses an inert gas such as argon and suits aluminum and nonferrous metals. MAG uses CO₂ or an argon/CO₂ mix and suits mild steel. In the US both are simply called MIG.

What wire should I start with for MIG welding?

For mild steel, .030 in (0.8 mm) or .035 in (0.9 mm) solid ER70S-6 covers most garage work, from thin sheet up to about 3/16 in (4.8 mm). Auto body panels usually call for .023 in (0.6 mm) wire.

Can I MIG weld without gas?

Only with self-shielded flux-cored wire (such as E71T-11 or E71T-GS), which carries its shielding inside the wire. It spatters more, leaves slag, makes more fume and usually runs with the gun on electrode negative.

Want all of this in one PDF?

The e-book The Welder's Forge covers stick, MIG/MAG and TIG from the first arc to the shop floor, with reference tables and technical figures, in plain American English.

See the e-book — $12.90 Download a free chapter

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