black soot push pull mig gun

Date 01-31-2004 20:05

I am using a miller push pull gun on alluminum, I believe 5356 wire, straight argon with the flowmeter set at about 30 to 35 and I keep getting black soot around the weld. It is an older gun, very large machine gun looking. I can feel gas flow out of the gun. I am keeping as short of an arc length as possible. I am using pulsed arc. The weld itself looks good. Most of the soot comes off if I wipe it off right away, I was just wondering if anyone knew what was causing this. Thanks

By EVWELDER (**)

Date 01-31-2004 20:30

Hello jdove55,

I weld 6061 material everyday with a cobramatic push pull gun with 4043 wire it sounds like your angle maybe too far forward that you are losing gas covarage try pointing your nozzel more towards your weld. Also another thing maybe if you have some kind of fan blowing your gas away.

hope that helps

By TRC

Date 02-01-2004 17:03

Hey JD55, once you've eliminated a gas coverage problem. Be sure to have clean base metal and electrode. And if you still get the soot it is inherent of 5356 to leave more by-products behind compared to 4043. 5356 just doesn't weld as nicely as 4043 I believe some call it "welders appeal".

Hope this helps- Ted

By sparx

Date 02-02-2004 14:07

The gas flow is not the problem when welding with 5356. The black soot that you are getting is called SMUT. This is more prevalent when mig welding with the 5xxx series filler alloys. What is happening is the result of metal vapor being produced by the intense heat of the arc, and then condensing on the base metal surfaces. the smut is a deposit of finely divided metal oxides. Although not harmful to the weld, it is a bit ugly. As you mentioned, you can wipe it off with a rag quite easily, but if left on the weld for a couple of hours, it can be tough to remove. Switching to 4043 will lessen the chance of smut formation, because it is mostly vaporized aluminum and magnesium, but there is still the chance of formation on and around the weld and heat affected zone.

By garryweld Date 02-10-2004 04:08

Hi, JD55
I'm going to suggest a few tips if I may, First & foremost know exactly what grade or series of Aluminum you are going to weld on. Rule of thumb if it silicone based use a 4000 series filler, if it is magnesium based use a 5000 series filler. Try to cut down your flow of argon to say 20, 25. Try the forehand motion, or in other words push the weld, have gun butt tilted back at 15 to 30 degrees from vertical pushing nozzle toward end of weld. Hope this helps!!!!

Garryweld