By Shane G
Date 01-14-2009 21:53
Edited 01-14-2009 22:45
Hello,
Not sure what machine your using or torch size but I was using 5/32" ceriated tungsten at work to weld 1.5" thick 6061 with a new Dynasty 700 also with pure argon. We were also told to maybe go to 3/16" if the tungsten was burning up or splitting.
Now you could also switch over and run DC with pure helium and stay with your current tungsten size or go back to 3/32" it will penetrate alot better but will seem to run dirty leaving black soot to brush off.If your running to a wps you will most likely have to run a procedure for the swith to DC and helium.
Also we had a preheat off 100° and a interpass of 400° called out.This might be another way to do it with AC and argon.Or maybe use AC with a argon/helium mix maybe 50/50?
What type of filler are you using 4043,5356? We had not luck at all with 5356 and DC because of the joint design being a u-groove about .750" deep and .800" wide. AC with the large tungsten and Dynasty 700 at about 350 amps finally got past x-ray.
By mountspire 
Date 01-15-2009 17:52
Edited 01-15-2009 17:54
I am using a miller syncwave 250. It is old like me but runs well. This is my first attempt to weld This thick of material on this machine so I appreciate all of you alls help beleive you me. I have tigged stainlees, brass, mild steel and alittle of aluminium. So this is a truelly new experience for me. I have been welding for around 30 plus years but I am always on the learning curve trying to better my skills everyday. I am running it on A.C. and start out at 250amps. I am also running high frequency constant. Thank you again
It would be interesting to know what amperage you're starting off at. What current type are you running? Are you using a WPS?
Aluminum is a bear if you aren't careful with it, i.e. keeping it very clean. If you search "aluminum" in this forum, you will see what I mean. This type of question comes up often here. :)
Pure tungsten for thinner parts is usually fine, but once you get into your greater thicknesses (and thus higher current and temperatures), you really should consider one of the Lanthanum or ceriated alloy electrodes. The operating parameters are provided by the manufacturer.
I do agree that 100% argon is likely the most efficient (and probably least expensive) gas choice for what you're doing.
To Shane G: 400 deg? Is that really what your IP temp was? Seems awfully high for 6061.
Yes almost positive it was 400,although being 1.5 thick and being roughly 16' long it never even got close to it.
And i agree argon is alot cheaper. We use 2% thoriated on everything we do only reason for the ceriated was it came with the dynasty 700 and the Miller rep. said that is what they use while researching and testing.
I would think 1/8" would be plenty to weld .250 alum. and the 3/8" also with some preheat. Most of the time at work we use DC on the thicker ALum.
Ceriated tungsten was developed to duplicate the properties of thoriated without the evil radiation hazard.
Discard the EWP and use EWCe or EWLa tungsten. Sharpen the tungsten to a point and set the Squarewave AC to Max penetration (65-75% time at negative; narrows or tightens the arc cone). For 1/8" tungsten set 200-250 amps and it should penetrate nicely. If, you have an inverter power source set the AC weld output frequency at 90 - 120 hertz.
BTW in the "old school"; with a balled tungsten, the formula was 1 ampere of current for each 0.001" (one - one thousands) material thickness. So, 0.250" would need 250 amperes and 0.375" would need 375 amperes. Spreading the arc out requires more amperage to achieve penetration. Narrower the arc cone; focus the arc energy, increase penetration, increase travel speed with less amperage to weld.
