Welding question, what causes this?

[muddysub]

I was welding on my rock sliders today and when I'd tack a piece in place, after letting go of the trigger the center of the tack would pop up like a little finger. It did it several times and I had to go through and clock them back down with a grinder. I haven't seen this before and the only thing I've changed is that I'm using some nozzle dip now to keep the tip clean. Could that be causing it? Here's a photo, kinda hard to tell, iPhones don't like to focus up close.

 

[Stomis]

Thats porosity in the weld popping through. You're pulling the tip away too fast causing the gas to disperse before the weld finishes cooling.

 

[muddysub]

Thats porosity in the weld popping through. You're pulling the tip away too fast causing the gas to disperse before the weld finishes cooling.

Ah! So as usual, I need to slow down and not be impatient.

 

[blazinzuk]

Quit tacking without your helmet on.

When I am doing alot of tacking I turn the welder up some. Like Stomis said your probably pulling out to fast. taking shielding gas away.

 

[muddysub]

Why would I quit tacking with my hood on? And out of curiosity, what should the gas be set to? My regulator was set at 12psi when I bought the welder and I haven't messed with it.

 

[ryoken]

he's referring to welding blind.. common practice to tack weld by just turning your eyes away and hitting the trigger without a helmet on..

12 is fine..i usually run 10 to 12.. bit breezy, I'll go up to 15ish.. some will say as low as 7, 8.. depends on how quick you mind running out of gas.. you can never have too much, but you'll blow thru bottles...

 

[tRustyK5]

I run at 20. BTW that number is in CFH, not psi. Cubic feet per hour. 12 is too low IMO. Gas isn't that expensive that I'm going to notice much difference, and the bitch about porosity is there is no 'burning it out'. Gotta grind it all out or it's back with the next pass.

I have found porosity more likely using nozzle dip, enough that when I did this fulltime I'd dip the nozzle when it was clean and hot, maybe once a day. At home I don't use it at all, and the nozzle is easy enough to clean without it.

 

[ryoken]

I stopped using nozzle dip yr's ago.. I found I got more contamination issues with it... all I do is keep a penknife handy and scrape out the nozzle every now and than...

 

[blazinzuk]

I run 18 cfh I put it as low as I was comfortable with I played with it alot and that's as low as I felt I could go.

 

[Stomis]

At work we run 30 cf dead head and it drops down to about 20 or 22ish open. I questioned my boss on feeling like it was really high the other day and he basically had the same feelings as rusty.

You can burn out porosity, its actually easy with a stick welder, but with a mig you've got to be welding hot enough to remelt all the way to your base pass or it will come back.

 

[tRustyK5]

Yes stick will burn it out, but we were talking about MIG...

Make sure you clean the oils off the tube you are tacking/welding too. You can get away with some surface impurities like scale, rust and oils with MIG, but not a lot. Do not use brake kleen or anything else that has chlorine in it...read the labels before using any of those. The chlorine gas released can really mess you up...

 

[cuervo]

I also run at 20 cfm. It's what's in the Miller guide that came with my 210 a bunch of years back.