[dewdrop9]

so can someone explain to me why you would have to fill your tubing with argon in order to get a good weld? its just a question that i have been wondering when i was watching tig videos on youtube

[weldin mike 27]

Only necessary on metals like ss and ti, protects the back of the molten/hot pool from contamination . Same idea as the gas coming out of the torch.

Mick

[zank]

I also backpurge the steel bicycle frames. It's cheap insurance on tubing that thin.

[rake]

I've done many a steel pipe/tube with a gas purge and a consumable insert.
Purging helps prevent any chance of contamination or defects from the back side of the
root pass. In many high pressure situations a small crack or porosity can lead to a catastrophic
failure. No matter what the base material is, if it's critical, it's usually purged.