What usually causes cracks directly next to the welds in 304 stainless constructions like downpipe or dump tubes?

Material is 304 with a thickness of 16g.

Or is the 304 not the perfect choise for these applications?
Maybe use 321 in the future?

Thanks

 

was filled used? Enough filled used?

 

Haz or stress on the downpipe/exhaust (no flex joint)

 

Depending where it cracked. If its near a bend that makes seance, because the material gets thinner as it bends in a mandrel bender.

 

Dumppipes especially crack in my experience, I think from the repeated, intense vibration if they are just hanging there.

 

Probably too much heat, but without seeing the failure its tough to tell.

 

Filler was enough - I´m pretty sure.
I usually weld these with 45-55amps.
Downpipe is always mounted with flex bellows, so vibrations should not be the problem.

The cracks only occure when and where I route the dumpetube into the downpipe and at the rear brace for the oem header mount behind the oilpan (honda B series).

The crack is directly next the weld - not the weld itself.

I never had a single problem with cracked manifolds or where I weld tube to tube.

More ideas?

 

vibration could still be a problem. maybe thermal expansion problems

 

Can you post a pic of it? I weld 16g at a max of 35amps with .045 filler. Are you using 1/16th filler rod with that amperage?

 

Yes, that´s the amperage I use for 1/16 filler.

It seems to be a problem of thermal expansation as somebody stated before.

I started to do a little research on different materials used for that applications.
This makes me to think about carbite precipitation that comes when 304 is used....

But it´s hard to translate all the articles :-)

 

weight X heat X thermal expansion X weld quality X material = infinite potential causes.

 

destroyer haha nice sig.

downpipes crack because guys dont go right through the material with the weld, so inside the pipe u still got a joint that isnt welded.

backpurge and check the inside of the welds for penetration!!