[rahtreelimbs]

What causes black soot when trying to set up a spool gun?

[noddybrian]

Generally you will get some soot when Mig welding aluminum - I guess the question is how much are you getting v/s how much is normal ! some filler wires will always produce more than other alloys - I have always thought the main reason is lack of gas cover as you usually don't get pre-flow prior to arc initiation with Mig so if it's minor soot only at starts this would be considered normal - if it's excessive then possible culprits are bad gas / wrong gas / gas leak - external draughts or heat induced draughts in weld area causing lack of cover - long arc length / low wire speed & long stickout or any combination - maybe if you can upload a picture the more experienced aluminum guys can pin it down - I will admit I don't do much aluminum.

[cj737]

MIG ally in my experience always produces soot. It’s the lack of the cleaning action you get with AC current. You can reduce the soot by using a push angle instead of a pull angle with MIG ally.

[noddybrian]

Totally respect you cj but surely if Mig is electrode positive it kinda already has the cleaning action of AC ? I do agree on using push angle - I was taught by someone that believed you only ever push Mig on any material - I accept you can drag if needed but I only ever push - people that drag tend to be beginners that can't see the puddle around the shroud or learned stick first.

[cj737]

Alright then, Noddy, how about this explanation:

GMAW melts the filler wire sooner than the base metal and since aluminum has some portion of magnesium within it, the mag and ally melt at slightly different temps (vaporizing in fact). The soot occurs when shielding has is inadequate and the door is actually comprised of ally and mag, and metallic bits. Proper CWD and gun angle are essential to eliminating soot. 4043 produces less than 5356 because the mag content in 5356 is higher. Push angle is heavily required to avoid the soot collection.

Yes, my earlier statement of “cleaning action” is not terribly accurate, but since the OP is self described as a newbie, I felt better not bombarding him with knowledge bombs. But I should have been more clear, and less imprecise.

Push, pull, both work in certain circumstances especially when access is limited. Push is better always, but not always possible.

Still mates?

[noddybrian]

Still mates cj ! it's not easy sometimes to explain what we believe in text format & in the past I have managed to offend with alternate opinions ! I do agree on the filler composition & did mention it in my original post though did'nt go into alloys - as you mentioned not to get bogged down in tech jargon if the OP does'nt need to know - I'm still of the view that many Migs will when triggered apply power / wire feed & gas simultaneously so there is almost no chance of the gas achieving good cover prior to arc initiation hence the smoke - I am only basing this on the fact I had a very old stand alone General Electric spool gun that had it's own power box plugged into 110volt for the wire drive but the gas valve was manual built into the gun having just a permanent pressure feed from a regulator - this valve opened just ahead of the micro switch controlling power / wire feed - if you were careful it was possible to operate the trigger gently & achieve gas pre-flow - I got no or almost no smoke using that gun - any I tried since are worse in this regard - if you listen to some of Peter Zilla's aluminum welding with his pulse mig or the push pull hooked to it I think you can hear preflow on the gas - perhaps a setting on these new digital sets - he gets very little smoke.

[cj737]

No offense at all perceived. When I am embarking on MIG ally, I preheat a lot and clean heavily. I use 5356 on marine applications for durability and strength so I’ve dealt with soot avoidance. A tight CWD and good gas coverage is very productive. In the end, it brushed straight away with a SS Brush.

Hopefully the OP learned all he needed and if not, heck with him!

[noddybrian]

Agreed on the preheat - it's very difficult not to get a cold start on aluminum without having a setting way too hot to do more than a few inches at a time without burn through - I'm interested to try in person one of the newer inverter sets capable of " run in " settings where they change WFS after initial start - also the slope down / crater fill stops - think the HTP200 / 300 does both.

[Oscar]

I'm interested to try in person one of the newer inverter sets capable of " run in " settings where they change WFS after initial start - also the slope down / crater fill stops - think the HTP200 / 300 does both.

Indeed, the HTP PP300 does. There is a lot of control in that thing.
The analog version of the PP300 would look something akin to this:

[cj737]

I'm interested to try in person one of the newer inverter sets capable of " run in " settings where they change WFS after initial start - also the slope down / crater fill stops - think the HTP200 / 300 does both.

Indeed, the HTP PP300 does. There is a lot of control in that thing.
The analog version of the PP300 would look something akin to this:

Had to opportunity the other day to visit a buddy's shop while they were running a new Miller 350P with ally MIG Pulse. FCUK me, I want one of those! Darn thing is magic

[Oscar]

I'm interested to try in person one of the newer inverter sets capable of " run in " settings where they change WFS after initial start - also the slope down / crater fill stops - think the HTP200 / 300 does both.

Indeed, the HTP PP300 does. There is a lot of control in that thing.
The analog version of the PP300 would look something akin to this:

Had to opportunity the other day to visit a buddy's shop while they were running a new Miller 350P with ally MIG Pulse. FCUK me, I want one of those! Darn thing is magic

I hope to try out the aluminum pulse/double pulse features next month. I want to order a dedicated gun for it with the appropriate liner so as to avoid switching things out in the gun for steel.