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Old 04-12-2019, 12:13 PM
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Default This is probably a bone head question. TIG welding

I've been thinking about trying TIG welding on aluminum, My stick/tig welding power source is DC only Miller CST250 so I know that one is out. I do have an old Hobart stick welder that's AC only. Do I really need high frequency to weld aluminum? Can lift arc tig be run on aluminum? Since there's no foot pedal option figuring out the heat settings might be a trick.
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Old 04-12-2019, 01:50 PM
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Without a high frequency add on box, I understand that aluminum would be difficult at best. The high frequency is part of what helps with the cleaning, it’s not just for starting the arc.

There are add on, high frequency boxes out there, I’ve seen two in person over the years. They aren’t plentiful, and probably not cheap, but they are out there.


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Old 04-12-2019, 02:01 PM
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As others have said, aluminum tig requires high frequency current. There are converter boxes out there but I have no idea how well they work. We ran one probably 30+ years ago and I know it didn't have a very smooth arc. Personally, if you want to weld aluminum I'd hold out for a dedicated welder with all the features included. From what I have read and seen online the newer technology is head and shoulders above what was available even 10-15 years ago.

You could probably make do with a converter but if you want to do really good work and be happy with it I'd try and find something better...
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Old 04-12-2019, 09:50 PM
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To the best of my knowledge, the high frequency is only there to help keep the arc going when in AC polarity. The actual AC current is what does the cleaning of the molten puddle when the rug torch current is positive, and when it goes negative is the normal weld current, that melts and fuses the metal.

You can weld with straight DC, but it really helps to have Helium. Just using argon is difficult, and it is a very different puddle, and dirty, at least the one time I tried it.




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Old 04-12-2019, 10:21 PM
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Quote:
Originally Posted by toprecycler View Post
To the best of my knowledge, the high frequency is only there to help keep the arc going when in AC polarity. The actual AC current is what does the cleaning of the molten puddle when the rug torch current is positive, and when it goes negative is the normal weld current, that melts and fuses the metal.

You can weld with straight DC, but it really helps to have Helium. Just using argon is difficult, and it is a very different puddle, and dirty, at least the one time I tried it.
I agree with Brian.

HF is there to stabilize the arc and the AC welding voltage passes through
zero volts. I keeps the arc going, because at the same time the current
also goes to zero as it is reversing. With square wave machine the HF is
generally just used when starting the arc and sometime will turn off. Like
when welding DC.

The HF has nothing what so ever to do with cleaning. The main welding
current does that, when the Electrode is positive.

Yes you can weld Aluminum with DC Tig but it is tough. DC Tig is used on
heavy section aluminum, 3/4" or better.

You can always give it a go on your machine and see if the welds you get
are good enough for your needs.
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Old 04-14-2019, 03:31 PM
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Thanks guys for the information. The very little I have tried welding aluminum was mig and let's just say it wasn't pretty at best. I have a couple of projects in mind that could be and probably will be steel, but aluminum would make using so much nicer.

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Old 04-15-2019, 05:41 AM
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yes the high frequency/voltage is just to start the arc and get it going.Its like a pulse of 4kv,a little current,but will put a jolt thru you the first time you come across it on a wet or damp weld table..ouch..don't screwball around with a hifreq box or anything else,get a true 200amp AC TIG machine to learn on.You don't want to complicate the learning process with machine problems as well..its easy and not THAT complicated..just keep the tungsten out of the puddle and don't hammer the footpedal right out of the gate..aluminum gets hot so you have to back off as you go so as not to overheat the metal..you'll learn..get a pound of 4043 filler rod,some scrap 6061 and have fun.Maybe try one out at your LWS or community college course?
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Old 04-15-2019, 07:27 AM
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I have done it every way mentioned. I have a freq box on my old stick machine, have done it with dc. The best advice I can give you is dont waste your time. Save your money and find a dedicated tig machine with ac and hf and a foot pedal.
The reason is that while all the other methods have been used they are much more difficult and unreliable. To someone learning ac tig on aluminum you already have your hands full, so dont add to your learning load. Once I bought a tig machine it was much easier to be succesful every time.
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Old 04-18-2019, 03:45 AM
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Can't imagine even trying aluminum tig without a pedal. Aluminum tig requires finessing the arc/puddle by nursing the pedal up and down. Once proficiency is attained, aluminum tig is funner than any of the other techniques.
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