Quote Originally Posted by HMW View Post
Backpurging? is that where you use a gas like Argon on the back of the weld while your welding it?? Have welded a few things out of stainless with TIG and a couple with SMAW, worked OK but didn't back purge either?? can you explain?? I have heard of it just not sure about it...Thanks
You are correct. Purging consists of replacing the air on the backside of a weld with argon. This can be as simple as taping cardboard to the back of the metal to form a channel to seal the area for argon. The main reason I have a flow meter with two seperate outlets is to purge with one (@ higher psi), while welding with the other.

Welds in stainless can be done successfully without purging, but the back side (of a butt weld) will have "cauliflower" growing out the backside. This is how the stainless steel reacts with the atmosphere, which is not pretty. It can be ground-down, but takes work. If you are welding a box, that inside corner where 3 side come together is expecially hard to fix with a grinder. Most of the time when the customer is paying a premium for stainless, they expect the welds to be not only strong, but cosmetically appealing as well.