Need help with air-arc

[PhilDirt]

I bought a ArcAir K2000 torch and some carbon electrodes. Connected the torch to my Lincoln Squarewave 175 to try burning off some ugly stick welds. Used 5/32 rods, set it to DC-, 150 amps. I can't get it to maintain an arc. Tried DC+, AC, raised the amperage, etc, still no luck. I can get a decent arc without any air flowing, but not with the air on. I even tried turning on the TIG spark, it will spark just fine but no arc. I can get the rod hot enough to melt, still no steady arc.

I also tried using an old gray TIG 300/300, results were even worse. I also have a red TIG 250/250, but didn't try it. What am I doing wrong, there's obviously something I don't know. I did some googleing and all I found was a reference on a machine rental site that said 3phase welders were needed for air arc work, because they had higher open circuit voltage. Is that the answer? All my machines are single phase.

 

[lantraxco]

Are you pushing the rod? Angle back and push in the direction the air is blowing, don't drag it. Sorry if you already knew that. The stinger should be positive and they recommend 90-150 amp setting for 5/32" carbons. 2" minimum rod stickout, max 7". They do say you need at least 60 volts open circuit. You might try AC, but you need the special AC coated rods, I think 3/16 is smallest offered. Good luck.

 

[CRAFT]

PhilDirt : I am no expert at air-arc but the Lincoln 175 you speak of is that only a 175 amp unit ???? …… because if it is you deff don't have enough grunt (amps) ….. I have the smallest Air-Arc head that they make and am using an older 250 amp Hobart Dc gas powered machine, it barely does the job, continually arc's out with too much air pressure ….. That being said you need the volume of air to blow the slag away …. have been told by the Pro's that in the perfect world NO Less than 300 amps even with the smallest carbons ……. Curious to see the out come of this thread ….. Good-luck !

 

[John C.]

You need to go with small rod and a bigger welder.

 

[Tiny]

Few times i have had to air arc I had a 300 amp Lincoln pipeliner maxed out And a real good source of air ..... Ear plugs are needed , Leather jacket is a good option . If it is working right the fire will fly . The ear plugs are are good for noise but most to keep from getting a "fryer" in your ear .

 

[Randy88]

Too small of welder and too big of rods, I use a bobcat 250 maxed out and it barely does it on the smallest rods I can get, anything larger for rods which is actually recommended I can't even get them to strike an arc hardly much less actually cut anything. If your doing everything right and it strkes an arc and then dies off and won't cut, forget whats recommended and set the welder at max and go get the smallest rods made and try that. If your trying on a 175 amp welder I don't think it would strike an arc, if it did you must keep in mind the duty cycle at 100 percent power which I'd guess might be a few minutes of use then sit for a half hour to cool off again. My bobcat is 100 percent duty cycle at 100 percent power. If you exceed the duty cycle you'll fry your welder pretty fast, which I've done on several stick welders over the years.

The bigger the welder the better the results, when you get above that 300 amp welder or in that 400-500 amp range air arc's work far better than with anything smaller but we still run them at almost 100 percent power, just use larger rods and do the job quicker.

 

[PhilDirt]

5/32 is a pretty small rod, like Lantraxco said it's recommended to be used with 90 to 150 amps. I turned it up to 175 and the entire part of the rod sticking out turned red and melted off, but still wouldn't arc consistently. I'm trying to use the 175 amp welder because it's the only one I have that's semi portable and can be moved to the door of the shop. I imagine a motor driven welder has very different arc characteristics than what I have, more like a 3 phase unit I'd guess.

I understand pushing is correct, but I haven't gotten that far yet, still just trying to maintain an arc much less move it.

I did try a 3/16 rod, results were about the same.

The smallest AC rod is 3/16, I wonder if AC would work any better?

I imagine a motor driven welder has very different arc characteristics than what I have, more like a 3 phase unit I'd guess.
Can I safely connect a cheap VOM across the weld leads to test the open circuit voltage?

Thanks!

 

[CRAFT]

PhilDirt : as you say its what you have for a welder …… The gas powered is what we have too, as "Randy88" quoted my machine is virtually identical to his (only its a Hobart) and it acts EXACTLY as his does ….. I also have a 230 Amp AC/DC Buzz Box with a 100% duty cycle ….. It TOO will not power the Air-Arc WITH the smallest carbons ….. I don't think there is much of a difference between a plug in welder vs a gas powered welder in this case, Just the portability is the factor ………….. Sorry ! … Just face it your welder is WAY to small (AMPs) ……cheers !

 

[Dad5]

For 3/8 rods we set at 500 amps and use 35 cfm air at 150 psi.

 

[Randy88]

Ok lets hash this over, first never use an old rod twice, if its getting that hot, throw it away, then try a different spot to start on, with a rod getting that hot you'll carbonize the spot and then you'll never start the arc. Start your air first, every time and then try to strike the arc, lean the rod somewhat and push into the weld, if it won't arc and maintain you don't have enough welder to make it work, change polairty and try different things, but each time try a different spot to start on. If its getting that hot with air running, your not striking the arc, your sticking the rod, with air it'll probably get that hot as you go, which is fine until you get the hang of it. Now what's this 300 amp machine you have tried?

Also on my old stick machine that's rated at 220 amps, I can't make it work it air arc on, I gave it up years ago, it doesn't have enough duty cycle to make it work let alone enough amps, my 250 bobcat is barely enough, as a matter of fact I've been told my many I'd never make it work on that either, it wasn't big enough, but with enough practice it works, not ideal, but works, I'd say marginally at best. No offense intended, but I don't think your welder is anywhere large enough to ever air arc with, just from personal experience.

 

[PhilDirt]

OK, I was hoping it would work judging by the rating of 5/32 rods. I'll try again with the 300/300 (rated at 375 amps).

try a different spot to start on, with a rod getting that hot you'll carbonize the spot and then you'll never start the arc. Start your air first, every time and then try to strike the arc, lean the rod somewhat and push into the weld,

This could be the clue I need, I was restarting the same rod and at the same spot, like I was trying to start a stick weld. The spot looked pretty clean so I thought it would be OK. Should I break the end of the rod off every time I restart? The rod isn't sticking, at least not like a stick rod sticks, I don't have to pull it off the part, it just touches and doesn't arc.

Does the steel need to be perfectly clean?

 

[Randy88]

The more amps the larger rod you need, but start with a small rod and work your way up in size, as to breaking off the end and using the same rod, lets get you to get it to work first, try a new rod each time, to save grief on your part, I'd also try a new spot each time to try on as well. As for sticking its not quite like stick welding when it sticks and doesn't arc. I always back up and after it arc's go through the spot it last quit so its working as you pass that spot, but everyone does it differently.

The cleaner the better as far as rust and whatever there is on it, I grind with an angle grinder to clean a spot to clamp my ground clamp onto, then hit the weld some where I'm going to start if its rusty not sure its necessary or out of habit but it all helps. I always hit the air first and then strike an arc, go into the weld at an angle and if it won't start yet, how old are the rods, are they wet, damp or anything like that, how fast are you giong, does it sound like the welder is working somewhat, does it buzz as you are going, not sure the correct term to use but I can tell if its working by the sound of the welder and also the sound the rod makes as its cutting or trying to start an arc. Let us know how its going or not going and whats the welder your going to use now that's 375 amps?

 

[PhilDirt]

whats the welder your going to use now that's 375 amps?

It's a Lincoln TIG 300/300, the big gray one. I bought it new in the '70s and it's had an easy life, no fancy tech but good old american iron transformer machine with adjustable spark gap and intensity and all that. 230 volt single phase input.

I have to fix my forklift now to move a few things before I can get back to this, I'll post more when I try again. Thank you very much, I've learned a lot so far, sounds like technique is more important than I expected.

 

[SE-Ia Cowman]

I have Been useing a bobcat 250 for a couple years and have used it a lot on a air arc a lot. I have got along good with 3/16 and have used some 1/4 with mixed results I bought a lincoln pipeliner SAE 400 that goes up to 500 amps a couple weeks ago and it will realy get it with a 1/4 rod. I will try it with some 3/8 as soon as I have a call for that heavy of gouging. I think that 300amp machine should run a air arc just fine once you get the hang of it but there is a steep learning curve for someone who has been stick welding for years and never used a air arc, I sugest you find someone who has used one and see if they can make it work on your welder, I am shure 175 amps wont give satisfactory results though.

 

[06Pete]

I don't know much about air arcing but I have heard of hooking 2 welders together to make it work. If anyone has any experence doing that I would like to hear how to do it and if it works.

 

[John C.]

So how far does the rod stick out of the holder when you try starting a cut?

You only need a couple of inches past the air holes in the head when you start cutting with that small amperage and little bit of air. I've used a Bobcat 225 and 3/16 rod for a long time for taking out a little bit of a fillet. You also mentioned a Tig welder. Is it constant voltage or constant current or both? I don't remember running any carbon rod on anything but a constant current machine and I used 1/4" rod at 300 amps on those. Those were also motor generators or engine driven units. I've only seen one rectifier machine used for carbon arcing and it was a 600 amp Linde ship yard machine.

 

[PhilDirt]

So how far does the rod stick out of the holder when you try starting a cut?

I was trying about 2 to 3 inches.

You also mentioned a Tig welder. Is it constant voltage or constant current or both?

It's constant current. A TIG welder is basically a good stick welder with a few add ons to control gas flow etc.

I wonder how a MIG power supply would work for this? You could definitely turn up the voltage.

 

[John C.]

Sounds like you have it right. I'm betting now that your welder doesn't have high enough open circuit voltage to start or current to maintain the arc. Try the small rod and if that doesn't work I'm sure you need a bigger welder.

Good Luck!

 

[norite]

The lincoln square wave 175 is a great little stick and tig welder, but as others have said it is not big enough amp capacity or duty cycle for arcair work.

 

[Nige]

We use a minimum of 350-amp welders for Air-Arc work. 500-amp works even better, it allows you to use more air flow that results in the liquified weld being literally blasted out of the joint.