It is not uncommon to use an argon helium mix when doing AC of thick aluminum. (if you don't mind buying a mixer) to get the benefits of helium and the good arc starting and stability of argon.
If you are doing code work... A PQR of course would be in order...
DCEN of aluminum takes some extra care and extra steps in prep... There are also some technique issues that need to be understood.
Here is also a place where newer "Asymmetric" GTAW power supplies.. (like Miller Dynasty) can come in quite handy... The DCEN amperage can be increased tremendously and the DCEP current can be reduced to just enough to provide cleaning action.... Few people actually need this type of technology... But the scenero above seems like it might be a good fit.
A dynasty is exactly what I currently use, Are you familiar with any of the starting parameters if one was to try this helium thing, I am quite satisfied with argon but would just like to mess around with the helium more out of curiosity then anything else just to see what it does.
Richard...
If you are just doing trials and not worried about WPS's its pretty easy to just go with gross numbers and adjust to make yourself happy.
There are so many combinations with an Asymmetric AC GTAW powerplant that you can really play scientist to get the results that make you happy.
I find when the rubber meets the road that Helium added to AC GTAW just gives a little more punch and thats about it. For example if you were trying to weld aluminum 1/4" or thicker and you were having problems with your 3/32 tungsten degrading or you just didn't like waiting around for the puddle to form; a dose of helium might make a weld a little easier than if you were using straight Argon... I really enjoy a 50/50 mix.
It's the current control that sets the high level Dynastys apart. I like a VERY high DCEN value for a more median duration with the DCEP set with just enough current to break up the oxide and make the toes shine. A 3/32 pointed tungsten can handle a good 250 amps or even more if the dwell time on the EN side of the half cycle is set carefully.
Increased frequency will have a nill effect on thick sections... I actually like to run about 50 hz when I'm on the edge of not being able to melt the base metal... 200 hz. (never more) is excellent for fillets in thinner aluminum. The constricted arc can be a true advantage on materials < .063 in my opinion. Frequencies above 220 hz will only trigger migranes, they do not increase performance in my view.
Lawrence you hit the nail on the head, Ive never used 50/50 before but it would be good on thicker aluminum. I was tolded that our Dynasty 350 would weld up to 5/8 material with Argon but we haven't had to weld nothing that thick yet. I think its the best GTAW machine that I have used.
M.G.
Al, I think he needs to give it a shot any ways because it will be something that he can add to his resume.
M.G.
Milton, this has turned into a great thread with lots of good comments and insight thanks for starting it.
Kind Regards, Richard.
With the Dynasty 200 using from a distributor supplied cylinder of 75% Argon/25% Helium, 70-75% time at negative side of squarewave and 120-180 hz AC using a pointed and truncated (blunted) 3/32 in EWCe or EWLa. This provides a very narrow and focused arc providing a narrow haz.
Increasing the time at negative to 95-99% provides very interesting possibilities for copper, inconel, monel and stainless steel. The frosting of the tungsten at this high time at negative must be watched.
357Max
We did some trials way back in the Aerowave days on Inconel/s and Hastalloy/s hot section pieces.. We used the 99% ish DCEN with a very high amperage but only 1% dwell on the DCEP... Sometimes we had to make on wing repairs on exhaust sections that just would not allow for part prep to the usual standard practice.
The results were pretty clearly an improvement, but we never got the traction to move forward... I don't know how you would quantify a PQR on a soot black exhaust strut made of Hastelloy X laying on your back in the tailpipe of a 727 welding with a mirror anyhow :)
Lock out those thrust reversers !
Al says:
I find it interesting when trying to get a welder to change to something different. It is easier to get an ocean tanker to change direction than it is to get some welders to change how they are doing something. Getting a welder that is used to welding with Argon to try using Helium or vice versa is like pulling teeth.
Al
I say:
I find it interesting when trying to get a _______ to change to something different. It is easier to get an ocean tanker to change direction than it is to get some _______ to change how they are doing something. Getting a _______ that is used to _______ with _____ to try using ______ or vice versa is like pulling teeth.
It's the human element I'm so fond of noting.
You can fill in those blanks with words of your choosing. It will still be accurate, and has been since man's first breath. People who are or have in the past, worked in vastly different fields can fill those blanks as well or even weller (!?) than people who work amungst welders.
Long after we are all dead, it will still be the same.
Human nature, regardless of technical advancement, will always remain the same.
I have no doubt that some inspector on the Great Pyramid Job muttered an identical phrase in ancient Egyptian language, whatever it was.
And I don't doubt that George Jetson will mutter the same a few centuries into the future.
The real on the ground deal is that the paid welder (sooner or later, in this economy prob sooner) will have to work within the process specified for the job or be an unemployed, hungry welder.
Same for the company, spec the wrong process/procedure and die quickly. Spec it right and make it thru. Many are dying as we speak.
J
Good point Al and I here what your saying , I have always been of the opinion that "If you always do what you have always done, You will always get what you always got" in other words I'm big on trying new things if for no other reason then to just have an opinion.
Thanks for your insight, Best to you and yours. Richard
Forum
