Expansion chamber stuffed. Advice needed please

[Danger]

Ive repaired lots of them over the years
- make sure no carbon is near the weld area as this will precipitate into the weld and cause it to become too hard/brittle - hence the cracking.
-

Whats the best way to ensure carbon is not present in the area blacksmith? Heat it to glowing red with oxy acetelene to burn of the carbon in the welded area before tig welding?

[theblacksmith]

Whats the best way to ensure carbon is not present in the area blacksmith? Heat it to glowing red with oxy acetelene to burn of the carbon in the welded area before tig welding?

I usually clean it mechanically-die grinder or grinder depending on access(usually I split chamber by hacksawing through weld after marking ref marks all around).With stainless I clean with pickling paste and scotchbrite prior and after welding(with TIG and 316L filler rods) With mild steel I usually mig weld and apply post heat to stress relieve around the weld.We all hate cracks( on exhaust pipes anyway lol)