problems welding .250 aluminum

[sandfish]

ok so i have never had this issue before but everytime i start to lay a bead black crap keeps coming out of the metal. ive ground it down cleaned it with brake cleaner and acetone and used a stainless brush on it before welding i even purged it with 8 pounds of argon..still contaminents keep puking out. is it the aluminum itself or the rod or me? the material is 2x2 .250 6061 and the rod is 1/8 4043. what am i doin wrong here?

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[RL Detroit]

I had the same issue while welding some sheet alum - I was using a spool gun hooked up to my mig welder so I assumed it was just becuase I used that type of setup.

[fasttruck ryan]

aluminum has to be welded with reverse polarity, and with that thick you should definitely use strait helium gas.aluminum requires much more current to weld. mig or tig. helium creates a wayyy more efficient path for the electrons to pass. the spool gun will kick ass. promise.

[sandfish]

problem fixed.. i was welding it in horizontal position i layed it down flat and bumbed the purge gas to 10 pounds and BOOM it welded clean..rookie mistake i guess. im using a syncrowave 250. now i have to preheat the material with map gas and then can only weld at 175 amps due to a 50 year old breaker box with only a 50 amp breaker so over 175 my breaker keeps popping. but slow and steady is getting the job done. thanks

[Wild bill]

An old timer showed me a trick that works well on preheating thick aluminum. He would use a rose bud tip, turn just the acetylene on, strike a flame and lightly blacken the plate with carbon from the acetylene. He then would add the oxygen to give a normal looking blue flame and heat the plate until the carbon was burnt off. The plate was then at a perfect temp to weld.

[FABRICATOR]

An true old timer showed me that trick too a while back. He was about 25 at the time.

[D.Mavis]

looks like you found your problem but you may want to inspect your gas lines with soapy water to make sure they arent cracked or leaking. we had that problem so the flow gauge showed we had enough gas flow but it was not making it to the torch. we turned it way up and sure enough it welded aluminum just fine. then we realized we had major leaks. Aluminum is certainly more sensitive to shielding gas. We just thought that we were slowly forgetting how to weld aluminum!

[tmathews]

Sometimes it can be the gas.... If it's running bad to start.. meaning when starting with a full tank. Also, never run the tank completely dry. Always leave some gas in the tank.

[DBMETALWORX]

I had the same issue while welding some sheet alum - I was using a spool gun hooked up to my mig welder so I assumed it was just becuase I used that type of setup.

If you were dragging the spoolgun it will be black every time. You need to push it and it'll be fine.

[KOH427]

Also, never run the tank completely dry. Always leave some gas in the tank.

Never heard this before, why?