Hello all,
Trying to weld aluminum here and am having a weird problem. I was doing just fine on this intake manifold project but something has changed. When I go to make my puddle the pieces want to curl back from each other and the aluminum gets that surface tension effect that makes it impossible to weld.

Any idea what's causing this?? I used a stainless brush on both pieces (only used for aluminum) then washed both pieces with dish soap, rinsed thoroughly and dried them both well.

I'm using a Miller Syncrowave 180, argon at 18 cfm roughly, amps at 110 (not full throttle on the peddle of course).

The material is 1/8" thick and I'm just doing a simple butt weld.

Thanks for any tips!
Fred

 

weird arc
tungsten weird
not moving fast enough

i usually smash the pedal at 110A at the beginning of my bead and let off after a bit, but i am moving really fast when doing this.

 

The arc was a little weird, as in hard to control exactly where it went. I may try regrinding the tungsten I suppose.

How can I move faster if the two materials never even had a chance to flow together and the filler rod wouldn't flow into what crummy puddle I did manage to get going?

thanks
Fred

 

try balling the tip. put the machine on DCRP electrode +, and just get the slightest ball on the end.

back to ACHF and slam the pedal and move fast feeding a lot of filler.

-derek

 

The surface tension is caused by contaminents rising to the surface of the weld pool. Either clean the surface of the material better first or the composition of the aluminum is just internally dirty in the first place.

 

also could be oxides. which is why i say slam the pedal.

 

can you see anything strange in the puddle? with a bunch of **** in basemetel you will see what looks like a spotty black skin sometimes and the puddle will look like moses parting the red sea down the middle of the joint.

I like to prep the edges of AL with a supershear since I know it wont leave anything behind and then wipe it down with acetone.

 

I've welded this exact aluminum sheet just last week so I know it's not a problem with the material's composition. And, I feel I cleaned it as well as ever so I don't think that's it either. I'm gonna re-grind the tungsten, possibly try the balling technique then floor the peddle and see what happens.

I'll post up my results.

Thanks
Fred

 

the problem is the layer of aluminum oxide over the molten aluminum. You CANNOT remove the layer since it rebuilds itself within microseconds of being removed. It is broken up by direct contact with the arc (that is how Al is smelted - Al2O3 is heated with a carbon electrode and the liberated oxygen contacts the carbon to make CO2). With Aluminum though, the HAZ is greater than the area the arc contacts, therefore the surrounding metal melts before the oxide layer breaks up, which creates a water balloon effect (molten Al inside a solid Al2O3 film). It tries to take the shape of a sphere making the sheet edge get thicker and shorter - this is much more pronounced in a butt joint and only slightly less so in a T-joint. This is easily observable by putting the arc on the filler and melting a blob - it quickly forms an ugly, oxide covered sphere. You can feed filler into it at the arc contact point which makes the blob grow with molten Al (be careful it doesn't roll off the table though - it's like quicksilver) or if you crank up the amps huge; it will burn off enough oxide at the surface to pop the balloon and allow the molten Al to "wet" out (it behaves much like solder at that point)

your problem is that you're adding too much heat into the edge before you have a "join" (also remember that heat can wick out through 2 pieces at a join (tacking bead) - when not joined, it has half of the effective heat sinking capablility and therefore can't take the same amount of amps - even though they touch, the oxide layer at the edge doesn't conduct anywhere near as much heat as pure Al does). Don't go for full penetration heat, try to just get a baby puddle started and feed in the filler to get a blob started; once it has sufficient mass (which acts as a heat sink) the heat can be turned up so it wets out the seam of the butt - at that point, continuing the bead should be straightfoward

 

Ok guys/gals, I re ground the tungsten and got all silly with the foot feed and things got marginally better. I had less surface tension problems and managed to make two pieces of Al stick together but it wasn't pretty. I've done so much better, I really don't know what the problem is now.

I'll try again with some different material in a few days, maybe I've contaminated the material somehow. I really need to watch a pro do this for a while.

Fred