How do I get rid of " the worm"?

[TraderMark]

I'm not a novice welder. I'm 50 years old and have welded most of my adult life, extensively at times, occasionally at other times. I've welded with stick, mig and o/a. But I've run up against something recently that's just whupping my butt.

I recently acquired a Millermatic 200 mig welder. Sweet machine IF I can keep the welds from being porous. Not every bead is porous. Sometimes I can weld a project & 99% of the beads will be perfect. Then there are other times when 99% of the beads are porous. I always know when the bead is going to be porous because the end puddle will "bubble". It looks like some kind of worm rising from hot lava. Reminds me of the "sandworms" in Beetljuice. I assume this is from some kind of gas forcing the molten metal to rise.

I've tried welding with the gas as high as 35 cfh and as low as 10 cfh. I've tried welding hotter, colder, faster, slower and every angle I can find to feed the wire. I've tried moving the ground closer to the weld and farther from the weld. I've tried more wire "stick out" and less.

Nothing seems to help.
Could there be something wrong with the welder itself? Could I have a roll of bad wire?

I'm going to try and add some pics of the welds to show you what I'm dealing with. Maybe I'm smart enough to upload them with this smartphone.

 

[topbuilder]

I also have a 200. Great machine. Is your surface clean prior to welding. Could it be a fan or wind is blowing you gas? What are you using for gas. Mixed or straight C02? Any surface rust on your wire? Any build up restricting your air flow out of the nozzle? Your wire is a 70s6 or close to it? That's all I can think of.

 

[Markcuda]

I say not enough gas.
To much wire out?
The term used in my shop is "porosity"

 

[topbuilder]

I use a torch and hit the oxygen lever to clean/burn the area before a weld. Then hit it with a wire brush. That will clean any rust or burn off any paint or oil. I have also run migs that just got too finicky to mess with anymore and the only fix was a complete new gun all the way back to the feeder. Tweeco (sp?) was the brand I used. I ran a shop with 4 millers of various sizes, always had extra liners and complete guns on hand.

 

[Markcuda]

Here are pictures of porosity.

Porosity formed and surface breaking

 

[Shield Arc]

Not to worry, these are just vents in the weld.






I'd say you have a gas flow problem at the nozzle. Release the drive rolls, and place the nozzle right at you ear, and see how much gas is actually coming out of the nozzle. Remember to release the drive rolls or you'll get the wire shoved in your ear!

Next thing would be a bad roll of wire.

 

[LD1]

It looks like your metal in the pictures is a little on the dirty side for a mig.

You really need bright clean metal. And if you are welding something like a pipe or something you cannot get to the back side on, and if you are running hot enough to get full penetration, you could be pulling rust and paint from the back side and causing you grief. Even some new metal with mill-scale on it can sometimes cause problems.

And as others said, make sure nothing is blowing your gas away. Dont use outdoors on a windy day and dont have a fan blowing on you.

Mig welders are great for new fabrication of things. But when making a repair on a rusty, dirty, painted, oily peice of equipment, Mig is not my first choice. But if used, CLEAN CLEAN CLEAN

 

[Shield Arc]

I've had really good luck with Lincoln's L-56 wire with less than perfectly clean metal. But clean metal is the best way to go!

These welds were made over epoxy paint, even when you grind the weld zone first, it can be a PITA.

 

[TraderMark]

Thanks for the speedy replies guys!!!

I've always felt it was a gas flow problem too. The gas I'm using is C-25 mix. The gun from the feed rolls out is a brand new Masterweld. (Tweco knockoff) Regulator is brand new too. It came with a HH 210 that a friend of mine bought recently.

I don't know what the wire is. It came from my LWS but being such a small town there aren't many choices when it comes to what they have in stock.

Re: metal cleanliness. It doesn't seem to matter how clean the metal is. It does this even with brand new steel and even if I clean the mill scale from the new metal.

No wind, no fan. I've even uses a tarp that covered the piece and all of.me just to make certain there was absolutely NO air movement.

I'll post a pic tomorrow when I use something better than this smartphone. It shows two beads on the same piece of metal. One is perfect, the other is porous.

 

[lostcause]

i've got a miller 211 and i occasionally get the same porosity and rising bubble at the end of the weld. i'm fairly confident it's a function of contamination. every time it has happened to me has been when working with some messy material - rusty, galvanized, or painted. when i'm using this type of material it's generally for a quick-and-dirty project, and often i don't grind the area enough, if at all. i can't say that i've had this happen yet when working with clean material.

i'd suggest doing some tests with all clean material and see if this still happens. other than that, maybe try a few different brands of wire as shieldarc suggested, but i think it's a matter of contamination. mig isn't as forgiving as 6011.

edit: looks like i was posting at the exact same time as you were. if cleanliness isnt the key, i dunno. one thing i can say is that to me it looks like you're moving too fast. it almost looks like you're going forwards and backwards out of the puddle and it seems to be making waves in the bead. maybe you're moving the shielding gas away from the puddle before it has cooled enough?