Gas Shielding:
This is not easy to explain...bear with me!
The reason you do not want to use argon with a mig gun is called "low
ionization or cold shutting". Argon allows that the gap between the end
of the wire and the work be very small when the arc jumps. This causes a
small crack at the toe of the weld. The weld will look very good but it
can fracture. Using a 80/20, Co2 / Argon mix will cause a high ionzation
( a bigger gap) and allow the metal to come to temperature before the
filler metal hits the area. Straight Co2 will typically have more
splatter around the weld as compared to a 80/20 mix.
Stick Welding:
If you burn thru, which is easy welding .125 wall tubing, the metal on
the inside of the tube is now brittle because it is not shielded by the
flux on the rod. This CAN cause a weld fracture. This is why NHRA has
banned the use of stick welding on all race cars.
Mig Welding:
Nascar uses mig welding over Tig probably because of the miles of tubing
in one of those cars. Teams in the know, are now TIG welding the
chassis.
We all have had experience welding up cars/bikes that have held up thru
crashes and years of abuse using mig, gas, arc and tig. Dollar for
dollar, I spend the time to tig all tubing as from education in
metalugy, I have concluded that it is the best welding process for thin
tubing. I have a book from a gas supplier outlining the proper uses of
shielding gas and am willing to try to scan some approprate pages in to
my computor if someone would like to see them.
I'm not a teacher so I hope I have explained this so everyone can
understand it!?!
joe
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