I recently bought a Lincoln Tig 250/250 welder. Seems to tig weld steel ok. Tried welding 1/16 alum, probably 6061. AC, high freq, air cooled torch, 1/16 electrode ( recommended by supplier) apx 20 cu. ft. argon. The arc seems to wander around blackening the surface until it falls thru without ever forming a puddle. I cleaned the metal using a stainless brush and sharpened and balled the electrode. I don't have much tig experience. Whats wrong? Thanks, Larry
Is there a possibility to adjust the time of the positive and the negative cycle of the AC wave ? If yes, you should increase the time of the positive cycle to obtain penetration of the aluminium oxide layer and to create a pool.
What type of tungsten elctrode are you welding with ? For AC welding on aluminium you should use pure Tungsten or Tungsten with 3-8% Zirconium. Other electrodes (tungsten with thorium etc.) are designed for DC welding and will have bad ignition on AC resulting in a wandering arc.
For AC welding it is not necessary to grind the electrode into a ball shape. This ball shape will automatically occur during welding.
Hope this info will help you.
I suppose welding ampere is not set correctly.
If using too high ampere, tungsten electrode melts and cause arc wandering and consequently turbulence occurs and air can comes to the molten pool (blacking the work piece). However, for a 1/16” aluminum sheet using high ampere will melt through and cut the work piece; so ampere must be too low. In this case also arc can wander.
For 1/16” Aluminum sheet 60 amperes can be good enough.
As a rule of thumb, use 40 amperes for each millimeter of aluminum work piece.
Which kind of tungsten electrode do you use?
Did this solve your problem?
Try welding some stainless if u have any. If it allso welds like crap you may have a hose conection going bad or loose. Steel is not as picky with shielding gas as aluminum or stainless. Recheck your colletbody, cup and backcap to make sure everything is seeting right up at the torch. Sounds like your sucking air. Allso if your cup is to small for 20cfs it will get turbulent and suck air into the streem of shielding gas. The blackness is due to some sort of contamination either from shielding problems or metal contamination or electrode. Try to eliminate some of those and hopefully you will fix it. Ray C.
Thanks for all the info. It does'nt weld stainless very well and even though it seems to weld steel ok there is a brown residue on each side of the bead. I will check the areas you suggested. Larry
Deffinetly suckin AIR find where and your prob is fixed!!!!!!!!
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