MIG weld on top of TIG weld?

[Andy1]

Hi guys
Looking for a bit of advice? I just purchased a new exhaust from America, it was really cheap, so i wasnt surprised to find 2 duff welds.
One is on the hanger for the backbox, and there is a hole right through into the silencer. The other is a pin hole on a butt weld.
I own a MIG welder, which would close these up just fine. However both the holes are actually on top of the TIG welds. Can my MIG welder lay a decent weld on top of these TIG welds?
Thanks in advance
Andy

 

[Tungsten Sharpener]

No problem at all, make sure you have the right wire, tig root mig cap - new one on me.

zTS

 

[Andy1]

What type wire do you suggest?
Tig root cap?
Sorry im still a novice at this

 

[English Steve]

Depends what the exhaust is made of. You need a wire to match the material. Let us know what it's made of and someone will be able to recommend the correct wire.

 

[Andy1]

Ah its made of stainless 304. I have stainless welding wire, 0.6mm?
Will the weld last a while or will it fall off every wee while?

 

[dannyweld]

no problem, just weld it up. a lot of stuff like that is tacked together by TIG then MIG welded up.

 

[dopplershift]

Tig root cap?

Andy, I think the root pass is the first weld bead down in the join. (Sometimes done with thinner filler rod to get down inside the \/ prepped joint)

Then this is 'capped' with one or more beads.

I dont really know much more than that. I think the root is for penetration, then the cap/s are for strength and appearance?

Have a look at some of Flange Jockey's awesome work (example).