On 16/11/2018 10:50, The Other Mike wrote:
On Thu, 15 Nov 2018 23:20:25 +0000, Fredxx wrote:

On 15/11/2018 21:35, Cursitor Doom wrote:
On Thu, 15 Nov 2018 12:45:04 +0000, John Rumm wrote:

Most wire fed gas shield welding on steel uses CO2 as a primary
shielding gas rather than pure Argon or Helium. CO2 is classed as an
"Active" rather than an "Inert" gas, hence MAG rather than MIG.

Kind of struggling here to work out what use *any* non-inert gas would be
in a welding process. The very last thing you want is oxidisation!

It's normally for arc stability. It is normal to add a small amount of
CO2 to argon as pure argon has poor arc stability. O2/argon mixes are
for stability. Though only a couple of % of O2 is needed.

For MIG welding CO2 also aids penetration so mixes for thin material only have
around 5% CO2, those for thicker material around 20%

Argon mixes with CO2, even at the 5% level are for all practical purposes
incompatible with that required for TIG processes.

The tungsten electrode is eroded more quickly in a CO2/Ar mix. I suspect
the arc is otherwise fine although may give more heat penetration as per
MIG welding.

But you can MIG weld with
pure argon, and some claim 100% CO2 works too.

There is little point in using pure argon, the arc is not so stable and
is more expensive. Many people do indeed use pure CO2, but more spatter
and more depth.

What is very clear is not all ARC welding processes are the same, even with the
same base material.

Agreed.