Fusion (Autogeneous) welding.

[TTNickSoCal]

In your guys experience, is fusion (Autogeneous) welding of stainless exhaust pipe less durable than normal Tig with filler. Assumming both situations have similar close fit ups. Im asking because guys from a car forum of mine says they would never fusion weld something that they intend to give a warrenty on. Is this the correct way of thinking? or are they just being overly cautious?

[shovelon]

Yes, it is less strong because the effective throat is reduced creating a stress riser. Conventional wisdom dictates that the weld be stronger than the material side adjacent to it.

[TTNickSoCal]

Ok cool thanks for the reply. I have noticed that while practicing fusion welds i often find im getting a slight undercut look to the side of weld which probably causes a stress point.

So are there any cases where fusion welds are OK?

[shovelon]

Ok cool thanks for the reply. I have noticed that while practicing fusion welds i often find im getting a slight undercut look to the side of weld which probably causes a stress point.

So are there any cases where fusion welds are OK?

Tacking parts in prep for silver braze, hermetically sealing cans, lap joints if approved by design authority and such.

Basically I just use it for tacking.