Page 1 of 4 123 ... LastLast
Results 1 to 10 of 35

Thread: Air-Carbon-Arc Cutting & Gouging HOWTO

  1. #1
    Senior Member moya034's Avatar
    Join Date
    Jun 2008
    Location
    Delaware, USA
    Posts
    1,652

    Air-Carbon-Arc Cutting & Gouging HOWTO

    Everything you wanted to know about Air-Carbon-Arc Cutting & Gouging

    Air-Carbon-Arc Cutting & Gouging is a very usefull metal removal process. It differs signicantly from both oxy-fuel cutting and plasma cutting. The process uses a carbon electrode, a standard Constant Current Welding power source, and compressed air to melt the metal and blow it away. This process will work on anything that can conduct electricity and be melted with an arc. Steel, cast iron, stainless steel, copper, brass, aluminum, magnesium alloy all can be destroyed with air-carbon-arc.

    It is not a common process among hobby metalworkers, and is typically only found in industrial environments. This is unfortunate becuase it is a process that can be of great value to us. After reading this post, you will know everything you need to get started.

    The main purpose for air-carbon-arc is gouging and removal of old or defective welds so that they can be redone, or the equipment dismantled. It will allow you to remove the minimum possible amount of material so that the joint can be re-welded. Oxy-fuel and plasma cutting are capable of gouging, however, neither does it as well as air-carbon-arc.

    It can be used for cutting too. Oxy-fuel cutting is pretty much limited to steel, and plasma equipment can be very expensive when compared to air-carbon arc. Depending on the thickness of the material you may have to take multiple passes. If you have a cutting situation where mechanical means are not suitable, and plasma/oxy-fuel is not available, it may just be your solution.

    With some practice, an operator can very accurately remove metal in a controlled fashion, and applications besides weld removal will soon be discovered. I have used it to destructively remove bolts and nuts, make quick and fast bolt holes, heavy demolotion, you name it.

    A little history lesson:

    Air-carbon arc cutting and gouging was invented during WWII when, while building a warship, a very long stainless steel weld was done incorrectly and had to be removed. The labor costs of grinding and chipping were cost prohibitive, not to mention the time it would have set the job back. At the time, they didn't have air-carbon-arc torches, so the operator held a carbon electrode in a welding stinger, and an assistant followed the arc with a compressed air nozzle. The gentleman who came up with the idea invented the first air-carbon-arc torch, patented it, and started the "Arcair" company that Thermadyne now owns.

    Equipment and consumables needed

    First, let's discuss the power source. Air-carbon-arc cutting requires use of a standard Constant Current (CC) SMAW (stick welding) power source.

    Remeber that post I made that discusses electricity? No? Well go read it now. The reason I made that post is actually so you can understand why the following is true: Single phase DC Welding power sources will NOT work with DC carbon electrodes.

    Don't even try it, it ain't going to happen. The reason is that DC carbons do not have the same chemicals found in welding electrode fluxes, and therefore do not have the same arc stabilization properties. The capactiors are not quite enough to smoothe out the waveform to make a stable arc with DC carbons.

    You will require a machine powered by 3 phase power, or an engine driven welding machine. For most hobby metalworkers, 3 phase is out of the question and the best option of course is to go the engine driven route. (Tell your wife, girlfriend, husband, or boyfriend that it's a backup power generator, and you won't be lying.)

    Now you have to be carefull when you go to buy your engine driven machine. Some lower end machines generate single phase power and rectify it, just like you would with line powered machines and aren't suitable. The mid to higher range machines will generate 3 phase power or pure DC internally for the welding circuit, and these are what you want. (The machine I use for my air-carbon-arc cutting is an old, used, Lincoln Weldanpower)

    (Note: They do make AC carbons that would in theory work OK on single phase power, however they do not make these in all sizes, and I have not yet had a chance to personally try them myself. When I do, I will post about it.)

    Well, how many amps do I need?

    I'm glad your asked that question! Air-carbon-arc cutting and gouging uses significatnly more amps then welding of the same sized electrode does. For most of the type of stuff you and I do, an 1/8 carbon is the most usefull size, with 3/16" coming in a close second. 1/4" and above is really too big for our needs. Here's a nifty chart:



    Note: I've found when using engine driven machines (both mine, and ones at work), that I need more amps to accomplish the same cut as compared to 3 phase powered machines.

    What else do I need?

    Obviously you need the air-carbon-arc torch! My one and only recomendation to you is the Arcair K2000 torch by Thermadyne products (Same people who make Victor gas-apparatus.) Anything larger then that is over kill for our needs, and also requires very large air compressors. The other brands of air-carbon-arc torches I've seen, I have not been impressed at all with, I think Arcair is the best. The K2000 will run you anywhere from $200-350 retail. I got a great deal on mine in "new" condition from Ebay for $95 plus shipping.

    Also, you will need an air compressor. The K2000 requirse 40 PSI at 8 CFM.

    The K2000 features a coaxial air hose/conductor. This hose accounts for about half the cost of the torch, so take damn good care of it. Running too many amps, stepping on the hose, melting the hose, kinks, etc., will all ruin your day.

    Here's a pic of the torch setup:



    You'll want to add an air hose, and welding lead pigtails with quick connects to the coaxial hose. Not using quick connects is a royal pain in the ass. (I keep my welding stinger on a 5 foot long pigtail and quick connect as well.) The rubber boot slides over the connection points to keep from arcing against crap.

    Safety

    Air-carbon-arc cutting and gouging is a very dangerous process. The arc is much brighter and more intense then a welding arc. It is an EXTREMELY loud process, and hearing protection is NOT optional. (Also, don't forget, not only do ear plugs save your hearing, they keep spatter out of the ear canal.) Heavy welding gloves, and leathers are also reccomended.

    I do NOT reccomend using auto-darkening hoods with air-carbon-arc cutting. Use a standard hood with a glass filter. Make sure you pick a shade filter # that is approiate for the amount of amps you are running.

    Also, this process presents a very large fire hazard. It is capable of blowing molten metal through the air up to 15-20 feet away if the trajectory is right, so make sure you have a good clear path, and DO NOT do this inside your shop.

    Electrocution is also a concern. Don't do this (or weld) if it's wet on the ground, you clothes are dripping from sweat, etc. The worst electrical shock I've had in my lifetime happened at work, last summer, sitting on top of a railcar on a hot sweaty day while using air-carbon-arc to trim a piece for fit up. I shocked myself, and was thrown back about 4 feet. I'm lucky I did not fall off of the car, and the electricity didn't pass thru any organs.

    Another considerion is your neighbors. Trust me, they will be able to see and hear you, so keep them in mind.

    Can you quit blabbing and get on to it, buddy?

    First of all, these carbons are BRITTLE, and expensive ($0.30-$1 a piece), be careful with them.

    You want your electrode stick out to be no more then 6" for the larger electrodes, and 3" for the smaller ones. As the electrode wears away, you simply loosen the clamp and slide it further out.

    Most DC carbons have a thin copper coating on them to improve the electrical contact between the carbon and the torch.



    Make sure the air holes are pointing the right direction! (That's towards the work, buddy.)

    The piece that has the air holes swivels 360 degrees so you can put it at any angle you like.



    Striking the arc is a little bit different (and easier) then with a welding electrode. Just LIGHTLY touch the electrode to the work, let the arc start, and slowly move it where you want it to go. This requires a special touch, and to be honest, I don't know how else to describe it. Some practice time will quickly teach this to you, as well as how fast you should travel. This really is easier then welding, however, like welding you will get better with practice.

    You want to hold the electrode at about a 45 degree angle. You want to use a "push" direction*. Make sure the air holes are BETWEEN the electrode and the work, not over top of the electrode. THIS IS IMPORTANT. Also, don't forget to open the valve! You will make a big mess if you don't. The valve is that black button on the torch handle.

    *(same meaning as with MIG welding.)

    Note: if you are having trouble starting an arc, try increasing the amps. Don't worry if this takes you past the limits of what the chart says above, or the box of carbons' documentation. Just use enough amps to get the job done, and no more. However, make damn sure you don't exceed the rating of the K2000!!!

    Note2: DC carbons use DC Electrode Postivie polarity.



    Here's a picture of what a gouge looks like, half way thru a weld.



    Here's an action shot. Note the intensity of the arc vs welding. To the right of the arc, you can see the molten metal flying to my right. (The electrode is traveling left to right.)



    Here's the completed gouge.



    Then you can take a grinder and clean it up. If you look very carefully on the bottom piece, you can see where I gouged the surface a little bit. This can be filled in with weld metal and ground smooth, before re-welding the joint. Nobody will know the difference.



    Here's an action shot of welding it back together.



    And here's the completed welded, gouged, and re-welded coupon. Yeah, yeah, my heat was screwed up on the beggining of the weld. If I did that on a jobsite, I'd have to gouge it out (again) and fix it!



    Well that's about it. Feel free to ask questions.

    Air-carbon-arc cutting is a really usefull process, and I hope you enjoy using it. With the large amount of amps, the intense sound and light, the fact you can cut thru metal like butter, and flying molten metal all make this a really awesome process, that is really fun to do (Until you have to do it out of position on a jobsite, and give yourself minor burns every 2 seconds.)
    Last edited by moya034; 03-13-2013 at 01:30 AM.

  2. #2
    Senior Member
    Join Date
    Jan 2010
    Location
    South Florida
    Posts
    383
    How about using a rotary phase converter to get the 3-phase?
    http://en.wikipedia.org/wiki/Rotary_phase_converter
    There are only 10 types of people in the world —
    those who understand binary, and those who don't.

  3. #3
    Senior Member moya034's Avatar
    Join Date
    Jun 2008
    Location
    Delaware, USA
    Posts
    1,652
    Quote Originally Posted by ziper1221
    How about using a rotary phase converter to get the 3-phase?
    http://en.wikipedia.org/wiki/Rotary_phase_converter
    That's a good question.

    Rotary phase converts don't actually generate "true" 3 phase current. They use a single spinning 3 phase motor and a few capacitors to mimic the 3rd phase. Most applications of rotary phase converts involve turning a 3 phase motor on a machine.

    I would be very curious to see the 3 phase output of a rotary phase converter on an oscilliscope. If anyone has any pics of this to post, please do.

    I'd like to hear from someone who has personall tried running a welding machine off of a phase converter. I'm sure one of these days I'm bound to try this myself, when I have the cash and can afford the extra play toys.

    That all being said, I think for many hobby guys, an engine driven welding machine is very useful to have, because it makes the electrical requirements in the shop easier, double as a power generator, and is portable. If you keep an eye out, you can find good deals on used machines that fill our needs well. (I got extra lucky with mine and only spent $125 on it!)

  4. #4
    Senior Member Rugerdude's Avatar
    Join Date
    Feb 2009
    Location
    Atlanta,Georgia
    Posts
    445
    Blog Entries
    6
    Not exactly on topic but I've been wondering for a while. Are you supposed to wear earplugs whenever you're welding? I saw on Lincoln's electrode box MSDS that you're supposed to wear earplugs and a respirator and all this other stuff. Is this true or are they just saying it because they have to? I noticed on the second action photo (not including the first diagram) that you were wearing what looked like orange earplugs.

    Anyway, air-carbon-arc cutting looks pretty cool. I don't think I'll need or be able to use it anytime soon but it's good to know.
    BYMC Member Map | My Hobbies | Anon's Foundry Tutorial


    “Two things are infinite: the universe and human stupidity; and I'm not sure about the universe." ~Albert Einstein

  5. #5
    Administrator Site Admin Anon's Avatar
    Join Date
    Nov 2005
    Location
    Indianapolis, IN
    Posts
    8,152
    Blog Entries
    11
    Added to the Hall of Fame.

    Very informative.

    I have a box of carbons that I bought a while ago for experimentation; while I can easily strike an arc between two of them (on an AC-only, single-phase machine), I never could get an arc to form between a carbon and steel. This seems to explain why. (Also, they're 3/8" carbons, which is what the guy at the welding shop recommended, but based on your chart are way too big for actual gouging use at anything like the capacity of my machine. They work fine for heating use, though.) I've been wanting to make a general-purpose carbon-arc heating torch for a while (as opposed to just holding one in each hand and jamming them together); I'm wondering if that plus the proper amount of air would make a primitive gouging torch as well. Might be an interesting project, even if it doesn't produce anything particularly useful in terms of cut quality.

    If I can figure out whether the AC carbons are a viable alternative, I might just browse on eBay for a real torch, though. That's certainly cheaper than a plasma cutter, and it beats trying to arc-cut with steel rods by a long shot.

    I'm curious why you said this, though:
    Quote Originally Posted by moya034
    I do NOT reccomend using auto-darkening hoods with air-carbon-arc cutting.
    What's the reasoning behind that?
    The process of turning stumbling blocks into stepping stones can at times require the use of a large sledgehammer.

    Foundry Tutorial
    My Website <<Now at prometheus-foundry.com

  6. #6
    Senior Member moya034's Avatar
    Join Date
    Jun 2008
    Location
    Delaware, USA
    Posts
    1,652
    Quote Originally Posted by Anon
    I'm curious why you said this, though:
    Quote Originally Posted by moya034
    I do NOT reccomend using auto-darkening hoods with air-carbon-arc cutting.
    What's the reasoning behind that?
    Main reason is because many times the amps you are running (even with an 1/8" DC carbon) are more then the shade filter of an AD hood is rated for.

    I've read some stories online about people having issues with AD hoods and the arc from air-carbon-arc. Don't know how reliable the stories are, but I know for sure that a good glass filter of the right shade will never have a problem with this process.

  7. #7
    Senior Member moya034's Avatar
    Join Date
    Jun 2008
    Location
    Delaware, USA
    Posts
    1,652
    Quote Originally Posted by Rugerdude
    Are you supposed to wear earplugs whenever you're welding? I saw on Lincoln's electrode box MSDS that you're supposed to wear earplugs and a respirator and all this other stuff. Is this true or are they just saying it because they have to?
    I like to always wear ear plugs. The sound of a welding arc really isn't that loud, however the main advantage of ear plugs is that they keep hot spatter out of year ear canal.

    Other nosiy activities go along with welding, like angle grinders, air compressors, and engines, so there are other noises to account for.

    The main reason air-carbon-arc is extra loud, is not because of the arc it self, but what it sounds like once compressed air hits the arc. The sound is much much louder then the sum of the arc and the air by themselves.

    As far as respritory protection, that depends on how good the ventilation is. If you are welding in a poor ventilated area, respirators are fantastic ideas.

    Quote Originally Posted by Rugerdude
    I noticed on the second action photo (not including the first diagram) that you were wearing what looked like orange earplugs.
    Yes, I was wearing orange ear plugs in all those action shots.

  8. #8
    Senior Member moya034's Avatar
    Join Date
    Jun 2008
    Location
    Delaware, USA
    Posts
    1,652
    Quote Originally Posted by Anon
    If I can figure out whether the AC carbons are a viable alternative, I might just browse on eBay for a real torch, though.
    If anybody has any 3/16" AC carbons lying around and sends me a couple, I'll test them out on my 220V single phase Lincoln Idealarc 250 and K2000, and post the results.

    My LWS does not have any in stock, and even tho I got a job recently, it'll be a while till I have the $ to order a box from the internet.

  9. #9
    moya's right. Arc Carbon cutting is truly awesome. And nobody can stress enough on the destructive potential of it. I remember working 3 floors down from some ironworkers that were arc-carbon cutting and the sparks/slag was finding any way it could down to us (even through joints in the concrete flooring). Started one guy's jacket on fire and melted giant holes into another guy's lunchbox. They even managed to start a very large fire in the dumpster OUTSIDE of the building.

    If you're gonna do this and you aren't in the middle of nowhere, I HIGHLY recommend you have a buddy hang out with a fire extinguisher or at the very least a garden hose and play fire watch.

    And don't do it around vehicles, the slag will melt into the glass like it was made out of ice....ask me how I know ops:
    10 million unfinished projects strong.....and growing.

  10. #10
    Senior Member Rugerdude's Avatar
    Join Date
    Feb 2009
    Location
    Atlanta,Georgia
    Posts
    445
    Blog Entries
    6
    Quote Originally Posted by moya034
    As far as respritory protection, that depends on how good the ventilation is. If you are welding in a poor ventilated area, respirators are fantastic ideas.
    I weld outside with a big fan blowing any fumes downwind (if any) so I think that counts as adequate ventilation. Still, this seems pretty interesting, and easy to make. Not sure how effective it is though.
    BYMC Member Map | My Hobbies | Anon's Foundry Tutorial


    “Two things are infinite: the universe and human stupidity; and I'm not sure about the universe." ~Albert Einstein

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •