How 2, ac arc welder to tig?

[R6 Racer]

OK, So I hear its possible to make a tig welder out of an old arc welder providing that it is an ac or ac/dc model.

Has anyone done this?

Does this actually make a quality tig?

What pitfalls are out there when trying this & how do I avoid them?

Is this costly & what exactly does one need to buy/acquire to make an arc into a tig?

I would like to hear lots of different stories, so tell me what you know!


Steve

 

[zkling]

IMHO I don't think it is worth the time and money, unless you have a super nice stick welder already. And or used tig machines aren't cheap in your neck of the woods.

Basically what you be limited to is steel, stainless and possibly DC aluminum. You will be running like the oil field guys run. No remote amperage control and scratch start.

You will need a WP17 torch with built in valve
Argon tank
flow meter
"power block" for torch

Here is a good example on it.

http://weldingweb.com/showthread.php?t=38106

 

[thinktwicez71]

/\....right ! i just went through all this , i went with a weldcraft wp-17v-25r assembly , a weldcraft 105z57 power block adapter , a HTP flowmeter off ebay brand new shipped for $29.99 , and then just go to your LWS store and get a has hose , collets , collet body , cups and filler metal if you dont already have all that


edit: just the flowmeter was 29.99 , not everything together

The only reason i went with this setup is because i already had a Lincoln idealarc 250 ac/dc and a 64 sa200 redface for stick welders , and in the pipefitters union 99% of the time tig welding pipe in the field is done with a setup like this , no dedicated tig machine or foot pedals.

 

[Tamper84]

If you want high frequency I know miller did ( they still might) make a stand alone high frequency box.

 

[Tamper84]

They still make em. Pricey little buggers tho. http://www.millerwelds.com/products/accessories/frequency/ I've seen them go cheaper on eBay and the like.

Chris

 

[kf4zht]

I will toss my 2 cents in. It's not that hard or expensive if you do some shopping around. I already had an AC/DC stick welder. In cruising pawn shops I found a 17 series torch with regulator, hoses, etc for ~$75. Used my existing argon tank (get a splitter) and I was up and going. I TIG steel and stainless, only hard part to get used to was the scratch start.

The lack of a foot pedal does get annoying, less from the power control and more from the torch being hot all the time. I am working on a foot pedal switch that controls a relay and gas solenoid to make it easier.

 

[deboto42]

I have a craftsman tig unit that attaches to an ac welder. The torch is air cooled so it is not real high amperage. Bought it at an estate sale than ended up with a miller tig unit water cooled. If your interested I can get you the model number I paid 50 for it.

 

[jerryd68]

Before the inverter style tigs were availble we used to do repair work quite often with a lincoln AC/DC buzz box a bottle of argon and a Tig torch. Only on Stainless though. It worked but the new little inverter 120 volt welders are much better.

 

[MoonRise]

As pretty much mentioned, hook up a TIG torch to the welder and connect the torch gas line to a gas flow meter which is connected to an argon tank.

You can then TIG weld in scratch-start mode.

If your welder is DC, then you can weld steel ('plain' or stainless).

If you have AC available, you -could- weld aluminum. Maybe. Putting a high-frequency 'box' into the mix would help keep the arc 'lit' as the voltage alternates from (+) to (-) and back.

You would have no pedal amperage control, and no automatic gas control (remember to turn the gas ON before you start welding and turn it OFF when you are done). No pre-flow and no post-flow 'control'. If you get a torch with a gas valve built-in, you can (maybe) waste a little bit less gas if you constantly remember to turn the gas valve on right before you weld and then turn it off ~ 5-10 seconds after you stop the weld (human-controlled post-flow timer ) and not have to walk back to the argon tank and turn the tank valve off all the time.

The tungsten would be 'hot' all the time the welder is ON (just like a stick is when stick welding), so don't put the torch down on/near the workpiece or anything electrically 'connected' to the welding circuit.

Doable? Yes.

Weld quality will (as always) depend on the human's skill and just how well (and coordinated) they can adjust travel speed and filler 'dips' as the only 'adjustment' (no pedal control, remember?) they have (unless you have a welder with amperage settting that is adjustable while in use, and have a helper to turn the amps up and down as you shout out to them).

 

[racingtadpole]

BTDT.. Wasnt inspired by the results, and scratch start while do-able is an art form in itself, not to mention very frustrating for the novice.
Put the money you will spend on buying all the tooling toward a cheap inverter TIG and be done with it. That was the lesson I learnt from it. I now have a nice little 200A inverter with all the bells and whistles and it is SOOOOO much nicer to use.

 

[Guster]

HF helps with more than arc stabilisation as it also helps control and 'clean' oxidisation when welding aluminium alloys that is why fancier inverter welders allows you to independently adjust the ratio between time spent in the positive vs. negative cycle for both HF(cleaning) and weld supply(heat and penetration). Many DC only inverter welders also rely on an HF signal to initiate/reinitiate the arc.

It is not too hard to add 4 high power rectifier diodes in a bridge rectifier circuit to a traditional transformer weld supply. An additional rated capacitor and inductor will help provide a smoother supply with better arc stability. Care should be taken with transformer weld supplies fitted with a current control circuit(ie. SCR based) as the particular design may not cope with a bridge rectifier terminating the transformer fulltime.

Scratch start is not that hard and the coordination skills become handy when finally learning to maintain arc length when welding complex positions. However the other features of an inverter unit do make it a worthy investment if regular TIG welding is to be considered. The fact that it saves on shielding gas by automatically starting and stopping gas flow, rather than manually closing a valve, alone makes a big difference. It was one of the features I added to my old transformer welder to reduce the running cost for personal use.

 

[MoonRise]

HF helps with more than arc stabilisation as it also helps control and 'clean' oxidisation when welding aluminium alloys that is why fancier inverter welders allows you to independently adjust the ratio between time spent in the positive vs. negative cycle for both HF(cleaning) and weld supply(heat and penetration). Many DC only inverter welders also rely on an HF signal to initiate/reinitiate the arc.

Ummm, nope.

The HF superimposed on the AC arc is there to help the arc reignite (or not go out) every time the voltage changes from (+) to (-) and back again, where the uotput is going through the zero crossover range (voltage and current). It does help stabilize the arc (by helping to keep the arc 'lit').

The 'cleaning' in AC TIG on aluminum comes when the electrode (the tungsten) is positive. The 'penetration' of the arc/weld comes about mostly when the electrode is negative. Approximately 70% of the actual heat from the arc/electrons goes to whichever 'side' of the welding circuit is positive. When the electrode is positive, ~70% of the heat is going into the electrode, when the workpiece is positive (and the electrode thus is negative) then ~70% of the heat is going into the workpiece.

Yes on DC welders using HF to start (or restart) the arc.

Yes on 'fancy' welders (usually inverter welders) sometimes giving you the ability to control the arc frequency (in AC mode), and the percentage of arc time spent in DCEN (for penetration) and in DCEP (for cleaning) when in AC mode, and sometimes also having waveform control and separate adjustments for the amperage used in the DCEN portion and the DCEP portion of the waveform in AC mode, etc, etc.

Yes on a machine with built-in gas solenoids making life 'easier' for the welder and helping to safe on shielding gas comsumption (and thus costs) versus the welder having to manually turn on/off the shielding gas before and after each weld.

But the HF is not responsible for the cleaning in AC TIG welding.

http://www.millerwelds.com/resources/improving-your-skills/tig/

http://www.millerwelds.com/pdf/gtawbook.pdf