Tack welding to look like tig..problem

[WickedWrenches]

Every time I do a tack weld on a 16ga exhaust pipe it ends up having a small dimple in the middle of the tack. Is there a way to stop this I am using millermatic 140 autoset set at the charts recommendation, .030 solid wire with 75/25 mix. Any help would be great. Thanks

[dearhuntn75]

Not that I know of.

I have found that it is just a product of mig welding. Looks like a belly button.

[eecervantes83]

Tack over it while it still red. Hot

[dave powelson]

crater cracks mig weld

I have found that it is just a product of mig welding. Looks like a belly button.

That's a crater crack.
Backing over it or as eecervantes83 sez:

'Tack over it while it still red. Hot '

These are not only crack initiators seen on the weld surface
but can and do extend down thru the weld.
They are a BIG DEAL--not just from the visual cracking that
can be seen (microscopically)....but most of the time
will leak pressure on a pressure tight weld. If one's seal welding
then back over them or else grind and fair the stops and starts,
the go back, overlapping and doing the back step to wash over.

[Rhinox]

Tack welding to look like tig..problem

its only because it is the end of the course!

once you finish your bead count 1-2 staying at same place.. and off the trigger! its only because your weld at that point isnt filled....

[Rhinox]

Tack welding to look like tig..problem

same with your tacks...

[tommy2069]

cut the wire speed back and turn up the heat if needed and spray arc it in pulses. you won't have any start and stops to grind down and it will look like a tig weld .

[Cgotto6]

Don't think he is going to spray anytime soon with his 140...

[Rhinox]

Tack welding to look like tig..problem

loll...

[BD1]

Wondering if going to 100% CO2 would help since it's a 120 volt machine.

[BukitCase]

I'm still tryin' to figger out how to do BOTH of these at the same time

"cut the wire speed back and turn up the heat"

[snowbird]

you need more control (s)

I'm still tryin' to figger out how to do BOTH of these at the same time

"cut the wire speed back and turn up the heat"

lower the wire speed knob, increase the voltage knob...

don't know much about a 140 auto-set...looks like it has 2 knobs... otherwise use an active gas.

[old jupiter]

Wondering if going to 100% CO2 would help since it's a 120 volt machine.

That's funny, I was going to suggest he try going the other direction, and try a bottle of C15 or C10 and .024" S3 wire. Hmmm . . . yeah, 16ga isn't all that thin, okay, never mind.

[tommy2069]

sorry i didn't see he was useing a 140 my bad

['Stang]

Don't think he is going to spray anytime soon with his 140...

If he does, I really have to buy a 140!