AC SMAW on an inverter power source question

[taylorkh]

To quote Monty Python "And now for something completely different..."

The AC frequency on an inverter power source can be varied considerably. For example a Dynasty 200 DX can be adjusted from 20 - 250 Hz. This allows considerable flexibility in tweaking the arc shape and performance when using the GTAW process.

A simple transformer power supply will simply output the same frequency as the input line typically 60 Hz (or 50 Hz in some countries). I would guess that AC welding rods were developed for use with 60 Hz long before inverter machines were available. So the question is...

Would there be any advantage to running a SMAW rod at a higher frequency? Or perhaps with high frequency stabilization? Or advanced square wave vs. a sine wave?

TIA,

Ken

[Matrix]

I have always hated AC stick welding. Most people do. The one single advantage of AC is better control of arc blow. Every other aspect is inferior to DC so why would you even want to? If you had a Dynasty 200DX you could do some lovely DC stick welding with it. Inverters have smoother arc control than rectifiers.

[taylorkh]

Thanks Matrix,

I almost had a Dynasty 200 DX. I just got back from a not very local LWS. I was at a closer branch of the same LWS company Wednesday and asked them what sort of deal they could make me on a Dynasty. They called another branch which had one in stock, a "new, floor display" model and offered a REALLY good price if I would pick it up at the other branch. For a floor display it had more scuffs and scrapes than my 3 year old Diversion, it appeared to have been hooked up and the parts, plugs etc. which were supposed to be in the box were nowhere to be found. Something told me to pass on the deal and I did. End of rant...

As to AC stick, I am after a Dynasty strictly for TIG. But as the stinger lead plugs into the same port as a TIG torch I figured that the same AC would come out and was just curious what a stick rod would do at 250 Hz.

Ken

[NathanH]

It would sure be interesting to play around with. Still just AC though.

[USMCPOP]

This is an interesting read ... AC does have some other advantages.

https://kb.osu.edu/dspace/bitstream/...pdf?sequence=4

[Matrix]

I've seen that old Le Tourneau article from the 30's before. It's basically a lot of paragraphs to really only say two things:
-Reduced arc blow.
-Better deposition rate. (due mostly to reduced arc blow)

A few things they conveniently forgot to mention are:
-They switched to AC welding machines because they were cheaper than DC machines and as a result they discovered an additional deposition rate benefit in the process.
-They build heavy equipment so there is little need to weld thin steel which can be problematic with AC.
-There's a much greater possibility that you can electrocute yourself while stick welding with AC.
-It's easier to stick weld with DC.

I didn't notice it the first time I read that article years back but this time I picked up on a claim they made of better mechanical properties in the weld deposit. I will research that a little but I doubt that there is any merit to it as I have yet to see a critical weld procedure specifically call for the use of AC current only. If it really does produce better welds you would think you would see that requirement every day for all kinds of purposes.

[go2building]

WOW!! One thing I do know, my Miller Bobcat has a caution symbol next to the A/C welding process selection. When Tesla invented A/C power he was criticized and told his A/C power was far more dangerous than the DC power being used at the time.
Just my .02 on this ****
Kevin

[Matrix]

WOW!! One thing I do know, my Miller Bobcat has a caution symbol next to the A/C welding process selection. When Tesla invented A/C power he was criticized and told his A/C power was far more dangerous than the DC power being used at the time.
Just my .02 on this ****
Kevin

Exactly. Out of curiosity I decided to take a peek in the owners manual on my Dynasty 200DX, which just happens to be the exact topic of discussion in this thread if anyone cares to remember.

On the very first page in section 1-2 under the heading "Arc Welding Hazards" are warnings on of the dangers of selecting AC output welding current.

And I quote:

- Wear dry, hole free insulating gloves and body protection
- Insulate yourself from work and ground using dry insulating mats big enough to prevent physical contact with the work or ground.
- Do not use AC output in damp areas, if movement is confined or if there is a danger of falling.
- Use AC output ONLY if required by the process.

(In large bold letters)
ELECTRIC SHOCK can kill.
With symbols depicting a weldor touching the end of the electrode and electric current running through the man's body.

Sure sounds to me like Miller thinks maybe there are a few safety concerns with AC welding. They tell you to take measures to prevent contact with the work or the ground and they show you a picture of a man touching the electrode and being electrocuted but never mind any of that, Cruiser knows best and it doesn't matter anyway because we take a crap all over the new people here whether they are right or wrong.

[gnforge]

Lol. !! Story of my life, been doing this off & on for 35 years. Back to full time. And just burnt my hand for the millionth time tacking up a piece.
I'm to old & stubborn now to learn any better.
Thx for the laugh, glad to know I'm not alone.
:-)

[paulrbrown]

gnforge, ever notice if you have a hole in your glove....you do wear gloves???? that is where the hot part always seems to be when you pick something up..... Mom said don't touch that stove, but did we listen, no, we bacame weldors....and we like it.........weld_4162.jpg