At work one of our engineers is undertaking a tig welding course and has to make a test piece comprising two pieces of 1,5mm thick 304 stainless steel approximately 150mm long butt welded together. (This is a C&G standard test).

The first test piece he made was rejected due to excessive penetration and because the weld bead was very flat rather than raised up.

The college said the two plates should be set 1.5mm appart but on the back (the other side from the weld) the plates should be purged with Argon.

He has made up a copper support plate with a 6mm x 6mm grove along it over which the joint is positioned. He then ran an argon supply into this groove and had another go at welding but the results are no better.

Does anyone have any experience of purging the back of a weld in this way or can you offer any advice.

Many thanks,
John.

He may well need to make the "chamber" for the argon bigger, to allow it to reach along the whole 150mm width, and cover it with a fine gauze to stop the gas disapearing too quick.

I have seen a purge box used i.e. a box with no lid with an argon supply.
The job is welded inside the box, argon being heavier than air stays in the box.

HTH

Neil