So most of my experience welding is with stick, I'm still getting a little comfortable with my MIG.

I was doing some welding in my garage yesterday, and all my damn welds had a ton of little pinholes-like airbubbles in them.

Too hot? Too fast? Too slow? Where am I fawking up?

It's a millermatic 175 w/gas, for reference.

Is the polarity right? How clean is the metal?


Andy

check your gas. was it windy? fan blowing?

check your gas. was it windy? fan blowing?

I did have a fan running in the garage.

So lack of gas would do this to me? That would help explain why I was getting great welds on one side, and then when I moved to the other, I couldn't get a good one to save my ass.

Probably means I was holding the gun a little too far away too, huh?

Is the polarity right? How clean is the metal?


Andy

Polarity is fine and the metal was about as clean as it gets, having just used the grinder on it.

Usually either a lack of gas or contaminations...a little oil will do that

I'd see if turning the fan off made a difference. Could be from blowing the shielding gas away from the weld, not necessarily that you are holding the gun too far away. A downside to MIG is that it doesn't work so well in "breezy" conditions.

Sully I have been doing a lot of experimenting lately with my 'new' MIG and here has what has caused me porosity SO FAR. :D

Gas too low.
Gas too HIGH. Yeah it blows so fast that it will draw in air.
Dirty/rusty.
Voltage too high.
Dirty wire.

Stickout will not generally cuase me a porosity problem. What will happen is it will sputter and cause problems related to AMPERAGE not voltage/contamination. If you are getting a decent, smooth weld sound w/o splatter then your stickout is probably not the problem.

I'm not preaching down to you this is just what has been happening to me lately. I have welded MIG/FC a bit with a clarke 90, but with my 'new' Miller I have found I pretty much suck way worse than I thought. Difference between sticking two pieces of metal together and actually making something decent.

Another one is a dirty nozzle. When I have been welding 'good' for a while I'll check out the nozzle and it's pretty clean. But when I lay a pretty crappy bead, which is regularly, the nozzle will get dirty fast and that just adds to the problem.

*edit* Ok here's more since I have been obsessing about this lately. :D

Are your contact tube and nozzle flush? I'm assuming short circuit so that is important. Mine does not like to be in any position but flush. For spray arc you want a longer stickout and more sheilding so you generally run the contact tube below the nozzle. But with short circuit and all the 'disturbance' it creates in the gas sheild, it's critical that it's flush. This will also create porosity/contam problems even if you have your nozzle clean and your gas flow right.

Air bubbles aka Porosity in welds are from contaminates in the weld.You either are not shielding the puddle properly or the weld area is dirty. Make sure all paint, oil or any other crap is cleaned before you weld. Then make sure you are getting the right amount of shielding gas, too much is a bad thing. Yes wind or a fan will blow the shielding gas away. Also make sure you are not trying to weld over existing porosity, gring to clean metal before you weld.

So how's it going?