Aluminum welding problem

[DrBob]

Hi, all. I just got a shiny new spoolmate 100 for my MM180. I have welded aluminum with my old Lincoln using an 'aluminum kit' and the regular gun but this is my first spooler. I am getting black carbon soot around the weld bead. Not on it. I doesn't seem to affect the weld much except at the toes where there might be slight undercutting. The soot wipes off easily with a paper towel or at the most a light wire brushing.
What I have checked/tried:
I checked the gas circuit, gas flow tried various settings from 20 - 50 CFH.
I had the tank (new -just filled once) emptied and purged with nitrogen and refilled.
I tried cleaning the base metal with several solvents and then wire brushing with a new stainless brush.
I tried increasing/decreasing the stickout, travel angle, work angle and travel speed.
I tried varying the voltage and WFS.

The soot remains. I have welded some coupons and bent them to failure in a vice. The welds are generally good although some have failed at the toes.
Also, there is some arc instability when attempting fillet welds. The arc jumps to the horizontal piece and leaves a big hole in the weld bead.
The 'spray arc' hissing/buzzing sound sometimes comes and goes. At first I thought I was getting to close /far from the base metal but careful weld travel at a constant 3/4" stickout gives the same result.
I also checked the input voltage (240V 40 amp circuit) and the work lead contact. I am using .030 3035 wire and straight Argon gas, DCEP.

I am totally beside myself! This honey of a machine will do mild steel with C25 all day and you almost can't get a bad weld.

I hope some of you experienced aluminum jockeys can help.
Thanks,
DrBob

[Broccoli1]

http://www.thefabricator.com/Aluminu...cle.cfm?ID=554

You seem to have checked everything though-

I only got the smut when I had a bad jug of Argon.

[bob_e95482]

The soot is typical when using a spoolgun.

[vin-man welding]

The soot is typical when using a spoolgun.

i second that. with out a picture what you described sound normal.

[GUIDO]

I agree with the last two fellas. It is normal with a spool gun. You also need to check to see if you are using too big of a contact tip or running the current way too high for the size wire that you are using, when it comes to the issue you are having with arc traveling from the root to the side plate. You said that you had undercut which leads me to believe you are cranked up too high, and possibly using too large of a contact for that size wire. If you plan on doing a lot of aluminum GMAW, then I would recommend a Python push pull system. I have one and runs flawlessly.

[welderdude402]

the new pythons are pretty awesome...unlike lincoln's shot with the cobra. i like the pistol grip push/pull guns though. they seem to be easier to use, once you get used to them, that is.

edit: i guess i shouldnt say all lincoln cobras are bad. i have only used one and it was fairly old, and just didnt care for it. the angle of the head was just in a weird place to me.

[Broccoli1]

How do you connect a Python push pull system to a MM180?

[DrBob]

Thanks to all who answered. Broccoli the gas was the first thing I thought of. After all - soot is carbon and where could the carbon come from? - CO2 that's where and where is there CO2? in a bad bottle of 'argon'. Well the fellow at airgas assured me that he purged the bottle twice with N2 and then refilled with pure Ar. I guess I'll have to live with it.

bob_e and Vin-Man I'll live with it if you say it's normal but I would still have my $200.00 if I had known that that's the way these guns work!

Guido I'm using the nozzle, contact tip and wire that came with the gun. 4043 (before I mistakenly said 3035) .030 I am using the recommended settings. BTW the settings seem very brittle - even a slight change leads to disaster.
When things go well it seems to make a nice enough weld. I wouldn't hang by one of those welds out of an airplane but it'll keep the lawn chairs together.
It's just that I'm spoiled by the job the MM180 does on mild steel. It is so forgiving and you can 'dial in' a designer weld bead for the job at hand.


So far I don't LIKE welding with this gun. You have to be careful at the start, watch your travel speed lest you melt through and be very careful when you get to the end of the run to shut down before you pull back.
Perhaps as I gain experience I'll come to terms with it.
Thanks again for the help - DrBob

[GUIDO]

DrBob,
Yeah welding aluminum, especially with an entry level machine and spool gun is fairly tricky compared to mild steel. I've been welding aluminum GMAW and GTAW since 1974 and have experienced all kinds of problems and used all kinds of machines, and that's why I recommended a push/pull system for smooth operation. I did look up your machine, and no it cannot accept a push/pull gun. I own a Lincoln Powermig 350MP with a 25 foot push/pull Python, for my aluminum mig welding but if you are not doing enough production welding to warrant a $5000.00 machine then you have made the right decision to use a spool gun system for econonic reasons as well as less hassle with " bird nesting " trying to push soft wire through a single drive unit, that can be frustrating even with a short lead.

You're right about paying attention to travel speed and settings, as you get more familiar with the machine your workmanship will improve. One thing that can help you when you start the weld to avoid a cold start, is to start and backtrack just slightly to flatten the start out. The same with the ending to avoid a huge crater at the end which is unacceptable in X-ray or precision structural welding. Another thing that also helps is slight ocillation to wet in the weld better. You want to be in a spray transfer ( sound of bacon sizzling), you do not want to hear any "pops" because every time you do hear a pop that is a gas bubble in the weld. It is different than steel welding in that spattering sound means gas bubbles. I learned this through X-ray work on my welds, one bubble per inch is acceptable. I know that you're not doing that kind of work, but what I am try to illustrate is some of the things to look for to improve your workmanship. As you get "hooked" on welding aluminum you will probably advance to a machine that has more features. A great feature that I have on mine is pulsing, which is nice for thinner material to keep it from warping and burn through.
But my greatest love is T.I.G welding aluminum, I have two machines that I use, one is a Lincoln 350 for stainless and light aluminum and the other is as far as I'm concered is the best welding machine in the world a Dynasty 700.
I weld 1-1/2" thick aluminum plate with CS 3 gas and practically zero pre heat. Anyway, welcome to the world of aluminum. I'm new to the internet and its exciting to be able to talk to people of the same interest. I'm sure if you have any problems in the future, there are a lot of talented people to help you through.

Have fun

[Broccoli1]

Guido,

good to have you aboard