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How Do MIG and MAG Welding Differ?

Date: 07-05-2024
GMAW Welding MIG Welding

MIG vs MAG Welding (banner) - Alphaweld

While almost everyone is using the word 'MIG' for both MIG and MAG welding, the vast majority of "MIG" welding jobs are actually MAG. Still, the industry has adopted MIG as the primary term, so you'll hardly ever hear someone refer to it as MAG, except on some welding procedure specification (WPS) sheets.

Both MIG and MAG fall under Gas Metal Arc Welding (GMAW). They are almost entirely the same. The primary difference between MIG and MAG welding is the shielding gas type.

What is MIG Welding?

MIG, like MAG, is a semi-automated wire welding process where the wire acts as an electrode and a filler metal. It requires a shielding gas to protect the weld pool from atmospheric contamination. However, since MIG stands for Metal Inert Gas, the shielding gas must be inert.

Inert shielding gasses are argon (Ar) and helium (He). So, when you MIG weld aluminium with a 100% argon bottle or an Ar/He mix, you are actually MIG welding it. The only true MIG welding is with an inert gas.

So, why is this important?

Well, inert gasses do not influence the weld metal. They are quite literally, inert meaning they have no effect whatsoever on the metallurgy of the material. Sensitive metals, like aluminium, copper, and magnesium must be welded with such shielding gasses. Attempting to weld these materials with MAG would end in a disaster of a weld.

While inert gasses are insoluble in molten metal and don't affect the metallurgy, they do affect arc and ionisation. Therefore, mixtures of helium and argon can produce different results than pure argon or helium. For example, a Ar/He mix can help you weld thicker aluminium because helium improves the arc's heat.

What is MAG Welding?

MAG stands for Metal Active Gas, meaning it uses reactive gasses for shielding. These gasses actually affect the material itself. That's why they are called active/reactive.

The most commonly used reactive gas is carbon dioxide. And yes – Ar/CO2 mix is also an active gas. Any mixture of an active gas with an inert gas makes the whole bottle an active gas. So, almost all ‘MIG’ welding on mild steel is actually MAG welding, as the most commonly used shielding gas is 75% Ar mixed with 25% CO2.

But you might be wondering: why do we need active gasses if they affect the material? Why don't we use true MIG for mild steel too? Simply put, using pure argon on mild steel would result in an erratic arc.

Mild steel has iron oxides on its surface, and these oxides attract the welding arc. However, oxides aren't evenly spaced on the material. So, under pure argon, the arc starts to wonder seeking iron oxides as they are the path of least resistance, resulting in uneven weld deposition.

However, when we add CO2, the iron oxide film becomes much more uniform. It's like paving the road for the arc. Instead of skipping over a bunch of potholes, CO2 ensures a smooth highway.

That's why we use reactive gasses and why MAG is the way to go for steels.

Using Oxygen and Pure CO2 for MAG Welding

Besides CO2, you can do the same with oxygen (O2). But, you'd need just under 5% of O2 with argon to achieve the same result. Still, the CO2 and argon mix is cheaper, making it the industry standard.

You can also use pure CO2 for mild steel. It actually improves the welding speed and penetration. But omitting argon causes much more spatter. Still, for heavy welding applications, pure CO2 can be the way to go.

MIG vs. MAG Welding Equipment

MIG and MAG equipment are mostly the same, but some differences exist. Both MIG and MAG welding processes use the same MIG welding machines. Almost everyone in the industry refers to GMAW welders as MIG welders, regardless of which process they'll use it for. The MIG torch, machine, gas regulators, hoses, consumables, everything is completely the same for the most part, except the shielding gas. You'll also see the MIG process as a part of the multi-process welders, but of course, this refers to MIG and MAG.

CO2 Regulator

In a particular case of using 100% CO2, you'll need a CO2 regulator. For example, the Tesuco Twin Gauge Series CO2 regulator is a popular choice. But, for more heavy-duty applications, you might need a Tesuco Heat Sink Regulator. Argon and CO2 mixes use the same regulators for pure argon.

MAG Wire and How to Avoid Porosity

You will also need a wire with deoxidisers for any MAG welding. Active gasses cause weld oxidation, which can lead to porosity and other issues. So, a wire like the Betaweld ER70S-6 with high levels of manganese and silicon will do the trick. Manganese and silicon bind with the oxygen and diffuse it to the surface, preventing oxidation and porosity. But, manganese is quite a dangerous welding fume compound. So, proper fume extraction machines or a welding respirator should be used (as with any welding).

MIG vs MAG Liners

If we are talking about true MIG for welding aluminium, you'll need a liner for aluminium, not steel. Aluminium wire is soft. So, using a steel liner will shave it inside the liner, causing it to clog up or kink, resulting in the birdnesting of your wire feeder. On the other hand, MAG welding plain steel requires your standard steel wound liner.

MIG Torch Duty Cycle

Another critical difference is the rated duty cycle of the torch. Some torches are rated with a higher duty cycle for 100% CO2 than for a mixture with argon. For example, the Sumig Titan S300 has a 60% duty cycle at 260A for CO2 welding and 60% at 225A for argon-mixed welding. If you need a higher duty cycle torch, consider something like the water-cooled Sumig Titan S500W. While both 100% CO2 and mix with argon are MAG, the torch duty cycle difference should be considered.

Need Additional Help? Alphaweld is Here for You

If you need additional help selecting the right MIG/MAG welding equipment don't hesitate to contact the experts at Alphaweld. Call (08) 9456 8000 or send us an online enquiry and we'll be happy to help.