tig characteristics for different welding voltages

Hi,
I have been looking at specifications of some commercial dc inverter welders like Lincoln invertec 275 or Miller CST 280 and notice that the welding
voltage is somewhere around 28 and for the tig specific machines it is more like 14.
I was wondering if anyone here would know if there really is any difference in the characteristics. I like the big fat electrodes like 7024 or 7018 in flat position as much as possible or tig for small stuff or when I really hate splatter which is quite often besides I have hundreds of pounds of steel tig wire. I currently have a Murex transformer welder which I was told by the welder repair place where I once got a after flow relay it was an airco re branded. As best as I can tell it says welding voltage of 40 volts on the back. I really can't tell the difference from medium range and big dial lower Vs high range with big dial lower. Generally there is supposed to be some difference at least for the dc generator type. I don't intend on getting rid of my dinosaur but want something for another location. Don't need any solenoids intend on using an argon water shut off to hang the torch on.
Thanks
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That is likely the Open Circuit Voltage, or OCV. Welding voltage will be lower, but a high OCV makes many stick electrodes happier, such as 6010 and 7018.

The CST 280 is a really nice Stick machine. I got the school to buy one 3 years ago, and it has been great. It is only a rudimentary TIG welder, but can accept a foot pedal. It has no gas solenoid, and only has Lift-Arc TIG start, and it is restricted to 220 volt - 460 volt, single, singel or 3 phase.
If you want a really good DC TIG machine, that is also a really good Stick machine, and don't need the higher amps, I recommend the Maxstar 200 SD. It has High Freq. start, digital readout, can weld from 1 - 200 amps, has the gas solenoid, and because it has "Autoline" it can run on any voltage from 120 volt to 460 volt, single or 3 phase, 50 or 60 hz. At $2500 it is a bit more than the CST 280, which lists around $2300, but is a more versatile machine. I have had a Maxstar 200 DX (DX means it has the pulser/sequencer) for 7 years and absolutely love it. I have done a lot of structural welding with it and routinely do onsite Stainless TIG for brewery repairs. In Stick mode it runs 6010 and 7018 like butter. The 200 DX runs around $2800, the SD is around $2500.
Their simpler little brother is the Maxstar 200 STR which is really just a smaller CST 280 since it is a stick machine with basic TIG, but it does still have Autoline, and only costs around $1650. I got the school to buy one last summer for campus repairs so I could bring my 200DX home. So far it has been another excellent machine.
Where it comes to Inverters I believe Miller really has the better technology.
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Yep, what he said. We have Maxstar 200 DX machines everywhere in the shipyard, and I love 'em! Great for stick and tig, I love having a machine I can trust to keep running, whether it's at 30 A for really small tig, or 200 A for lightweight (1/4") CAC.
From personal experience over the last 4 years, I want a Miller MaxStar 200 DX a little more than I want my two front teeth!
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Tin Lizzie
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Ernie Leimkuhler wrote in message

welders
more
difference
in
was
don't
off
The question I was after was the maxstar ones rate tig at 16 volts give or take and stick at 25 volts give or take while the cst 280 rates both processes at 26 volts for comparable amps connected to single phase, so what is the difference going to be at say 150 amps on tig using the one which only has 26 volts and the other which when set on tig is at 16 volts. Whether it is miller Lincoln thermal arc model choices are similar. I have been known to use helium or helium mix as well. The rod I have is E70s-6.
The welder I have now will draw 91 amps at 230 volts probably something like 400 amps output and that is where (pretty sure) it is rated at 40 volts I think the open circuit is like 80 volts. It has high frequency and I have a super separate box for high frequency since I don't think the one in the machine works that great however just scratch start or scratch start on a piece of copper isn't all that bad if the buzzing noise is annoying.
I see the maxstar models don't de rate on single phase, I had a color brochure a few years ago and thought they did. The cst 280 is really only good for 200 on single phase the way the specs look and weight wise has less stuff in it than the invertec 275.
http://www.millerwelds.com/pdf/spec_sheets/DC29-5.pdf maxstar200str http://www.millerwelds.com/pdf/spec_sheets/DC32-0.pdf maxstar200 sd lx dx http://www.millerwelds.com/pdf/spec_sheets/DC29-55.pdf cst 280
Fran
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Well I am not sure how to answer you. I can say that having used a LOT of machines: inverters, generators and transformers, I love the way the Maxstar runs stick, and TIG. Smooth and precise. Lincoln's large Inverters are OK, but I still prefer Miller.
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fran...123 wrote:

TIG welding is a "constant current" process. If you are pushing 90 amps into a TIG torch with an argon shield, the power supply will deliver the voltage required to push 90 amps. If you change welders, I don't think the voltage will change for a specific current flow. Changing gasses will change the voltage. This is the reason that helium welds hotter, it has a higher arc voltage. The power in the arc is higher because of the higher voltage.
I believe that the arc voltage for a given current setting is mostly dependent on the gas that you are flowing. It is the ionization voltage for the gas.
Stick welding is also a constant current process, but the arc voltage is going to vary because the different fluxes will create different gas mixtures to ionize.
Note that these comments are based on what I think is happening. As I weld alone, it is really tough to look at the arc voltage on the selder behind me while welding. If someone like Ernie who can watch someone else welding and see the arc voltage can comment on this, I would apprecieate it.
BobH
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BobH wrote in message ...

Thanks for the responses
I realize the constant current type of welding and the constant voltage type which is mig or it's proper letters depending if it is tubular or whatever. It is close to constant but there are graphs of how it varies depending on how things are set I seem to recall from the instructions of the flat head gasoline SA200 I had. I did try tig with that and spliced in a foot pedal rheostat into the fine current adjustment wire. I am not sure if I could describe how that was different, it used major amounts of gasoline.
I don't recall reading about the gas and voltage but it is informative. I do recall seeing a cross section of a bead and what depth the melting goes to for each. The electrons get stripped off the inert gas atoms and then throw off major heat when they pop back into position. that is my idea of where the heat technically comes from or transfers from. At least with my tig machine you get more heat if you hold the tig arc short.
using the miller data which is similar to other manufacturers the seriously tig slanted machines spec their voltage about 10 volts lower than the stick ones. Sure it can be modified by the arc force or the special application dial on a motor generator torpedo type which have probably mostly been cut up for scrap by now. You may notice the maxstar ones have different voltages listed for tig and stick so the switch must do more than turn on the lift arc feature or the solenoid. http://www.millerwelds.com/pdf/spec_sheets/DC29-5.pdf maxstar200str

dx
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fran...123 wrote:

(snip)
(snip)
The voltage used is a function of "arc length", shielding gas and ground losses.
Stick "arc length" is usually 1/8" to 3/8" (arc gap) depending on electrode dia for electrodes 1/4" dia. or less and flux type.
For tig the arc length is less, usually 1/16" to 3/16" (arc gap) so less "force(voltage)" is needed to carry the required current.
Different sheilding gases can account for up to 4-5 volt changes in "arc length", but the large factor is the gap and ground loss should never account for more than a volt or so.
Matt
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