Cracking in stainless welds

A friend of mine recently had a set of stainless turbo headers built for his car by a local fab shop. After only a few hours of use we noticed that almost all of the welds had a crack right down the center. After closer inspection it looks like they pulsed over the original welds to make them look cleaner. The welds look pretty good and I am just puzzled on why they cracked in the first place. Was it the pass on top that did it? improper back purging? to much heat? wrong filler? wrong type of stainless for the heating and cooling of an exhaust manifold? I'm fairly new to tig and am trying to educate myself as much as possible. Your site has been by far the best one i have come across so far and i greatly appreciate you taking the time to share your all of your knowledge on here. You kick ass!


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the cracking could be caused by all kinds of different things.

using 303 free machining stainless.

excessive stress

inadequate filler and cross sectional thickness of welds.

if the cracks appeared that quickly, it is possible they already existed and that is why they were welded over.

that seems most likely. cracks welded over by washing leaves a cosmetic weld pass that is very thin.

the crack underneath propagates quickly.