mig weld aluminum: lots of porosity

[MScriven]

Hello. My name is Marty. Where i work we're tying to weld an extrusion to rolled piece of aluminum. Specifics as i know them:
XR Aluma feed unit.
Aluma power 350 MPA.
Rolled "can" shape: 6061 T-6, .050" thick.
extrusion: 6063 T-6, about .100" thick where welded.
3/64 4043 wire
argon @ 30 CFH.

Weld looks OK, not a lot of soot (smut?). Penetration is OK. Welder is connected to a robot, and appears to work OK, e.g. position and travel speed. The robot and welder are new to us. We have the same welder on another machine where we weld the edges of the rolled can and it seems to work OK.

See attached picture. We're getting tons of porosity. Have tried welder in synergy and non synergy mode. Extrusion is anodized, but we are sanding it off, taking care to not embed anything into the aluminum.

Don't know what else to try. Supposedly the 4043 wire should work when welding this extrusion.

Anyone with any tips please send them my way.
Thx.
Marty

[Bodybagger]

Try this same process joining two pieces of rolled stock, then again using two pieces of extrusion. I think you'll find that the rolled to rolled joint is fine and the extrusion to extrusion joint looks like chicken poop. I'd suggest cleaning the anodized finish with a carbide burr instead of sanding. I've found that sanding with aluminum oxide or silicon carbide abrasives does more harm than good.

[MScriven]

Thx. may try that.

Found another thread that suggested to turn gas up to 45. That helped a ton.
More testing tomorrow.
Thx.
Marty.

[cruizer]

Synergy mode will be best, gas is a little high kinda freezing the weld too fast. for robotic applications 15to 20 CFH is good enough. Also your time to start needs to be slowed down a bit

[Danl]

I had this happen. Turned out the gas in the bottle was 75/25 mix instead of 100% argon...Regards, Danl

[MScriven]

Tried again today using gas at 45 welding extrusion to can w/ same poor results. Yesterday welded piece of 6061 to can and was good.
Will try again w/ gas at 20.
TIG welded 2 extrusions together and was OK.
Gas is plumbed to machine from big tank outside; should be ok.
Cruiser: What do you mean time to start needs to be slowed down?

Thx.

[MScriven]

Tried w/ gas at 20 and still no good. Tried one at 50 and it was better, but maybe just coincidence.
Extrusion doesn't always fit perfectly flat on can. Maybe has .020 gap in places. Could that be a problem? I'm holding pieces in a fixture. Maybe i should tack them in place making sure there is no gap, then weld?
What else can i try?
Thx.

[walker]

Sounds like the extrusion is the problem. Concentrate your efforts on cleaning the anodized off, and cleaning the piece with acetone first.

[MScriven]

But i can TIG 2 extrusions together. Wouldn't that rule out the extrusion being the issue? Or could extrusion weld differently, MIG and TIG?

Thx.

[cruizer]

Well, you said you were running with a robot. So, increase the in position start time, so the puddle has a chance to form. Alot of variables here, often takes me a half a day to get things just right.. Angles , stick out, gas, material, Can't be running at 50 CFH, that tells me that your stickout is great, 1/4 to 3/8" is maximum. Yours is 1/2" or more. and your nozzle is likely 5/8" so thats wrong as well.

[MScriven]

Hmmm. We had a miller guy here and i believe he said 1/2". Stick out is measured from tip to work piece? I do have 5/8 nozzle. I'm curious: how did you know i'm running 1/2" stick out?

Much better results today. Started over w/ settings. Tried to "turn off" the settings that vary arc length/ wire speed so you get that "stack of dimes" effect. A little bit of porosity still, but not nearly what it was.

thx again all for your help.
Marty.