Welding Class 1 piping with MIG

All the MIG guys that run hardwire at the company I work for use straight Argon....

Although some flux core stainless steel wires do use carbon dioxide mixes generally carbaon in any form is to be avoided. I have never heard of hard wire stainless used with a carbon dioxide mix. Usually the small amount of oxygen in the argon mix is to improve arc characteristics. I would try several wires giving the sales departments concerned a chance to provide a weld procedure. Bottom line should be the wire and process that qualifies and satisfies the welders on the floor should get your business. This site may be a good place to start.

For MIG welding Stainless steel pipe? How would you get any penetration at all? I can't see how that would work.

Oxygen or Helium tri-mixes work best. C25 can work in a pinch, but you get a lot of oxides.

They use a large gap, tack at several places and then go back to weld it out. The ones I have seen do it, do it in short weld intervals, like less than a second at a time. As you can see from the pics that it can and is done. Almost like a pulsing weld only with their mig guns. I understand how some of you may find it hard to believe, so I put up some pics at the following address so that you can view them and make up your own minds. And by the way, these welds were xrayed as they were going underground.

Ones that start with Cawelo@ChevronTexaco and Cawelo_1799.jpg