Carbon Arc Gouging VS Plasma Arc Gouging?

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I should start by saying I work in production shop that utilizes robotic welders. Robots are great tools, but ours do not have the sense to stop welding when welding issues arise. Like a dirty nozzle or someone leaving an over head door open while the wind is blowing. These issues are usually the result of human error. When insufficient gas happens it can be a real mess. Depending on the part, it could be 2'-20' of weld that needs to be removed due to porosity. We typically use a carbon air arc setup on a 500 amp GMAW welder (red) to dig out long welds. It works great but is somewhat of a hazard with sparks blowing across the shop. I've recently been working with a new 65 amp hypertherm plasma machine to gouge out porosity.  It does a great job of cleaning out the offending welds. But after you de-slag and clean the material up with a grinder followed by blowing out the contaminates, the re-weld tends to still be full of porosity. Now I realize the easy answer is that I'm not removing enough of the porosity. But with carbon arc, I can remove 75% of the material, clean out the slag and grind back flush. Turn up the heat to make sure the root gets burned out and I'm good to go.  With Plasma gouging I have to take everything out and even down get into the root to get a good re-weld. And even then its not a guarantee'd success. So has anyone else had a similar experience with plasma gouging?
Reply:Im not a fan of plasma gouging. The slag or dross is much harder to remove than when done with an air-arc. Besides that it's slow in comparison. I'm sure there are industrial plasma setups that are better than your typical 50-85 amp setup but at a huge price.
Reply:The plasma gouging setup is also kinda worthless in corners and funny angles. IMO, carbon air is more predictable in width and depth of gouge as well. Its always amazed me how many welders are scared of the damn thing tho. They'd rather grind for an hour than take a few minutes to learn how to gouge.
Reply:I bet the plasma gouging is leaving a layer of nitride on the metal, which if not removed will cause porosity. I don't think carbon arc gouging does this.  https://www.thefabricator.com/thewel...gouging-methodMiller Multimatic 255
Reply:Air-arc leaves carbon behind. Depending on the welding process and material itself it's also an issue that needs to be dealt with.
Reply:Someone good with an Air arc can do a pretty clean gouge. The trick to a sound weld is to clean all the edges to get rid of any possible carbon deposits deeper in the gouge. It is very frustrating when you think you have a porosity filled weld cleaned out but the new weld also has porosity. I haven't used a plasma gouger enough to know how it effects being welded over. I think the sound and sparks are what scare people away from an Air arc gouger. They are kind of intimidating. A lot of weldors crank the amps up a lot higher than they need to. Even more frustrating is when Dual-Shield wire has porosity for no apparent reason and it's in a tight corner that's hard to clean. Worked in a shop where an experienced weldor threw the Mig gun across the shop after getting porosity welding gussets on a flare stack base. I'd had the same issues too. Weld up 3 of 4 gussets no problem, turn the stack to weld the 4th gusset in the same position and get porosity.Last edited by Welder Dave; 07-16-2021 at 12:59 PM.
Reply:Another gouge option when not to deep or wide is the Chamfer Arc stick electrode. You can do pretty precise gouges with them and they are fairly clean gouging. I sold Arc Air for many years and it's tried and true but for smaller projects I'd still vote for plasma or chamfer arc rods.Thermal Arc 320SP ( Lorch )Cobra PythonsThermal Arc 300 AC/DC  ( Sanrex )ESAB 301i AC/DC  ( Lorch )Thermal Arc 161STL  ( WTL )Thermal Arc 190S  ( Sanrex )Cut Master 82, 42. Cut45 ( WTL )Victor Gas Apps.Boxes and boxes of welding crap.
Reply:Originally Posted by RondoAnother gouge option when not to deep or wide is the Chamfer Arc stick electrode. You can do pretty precise gouges with them and they are fairly clean gouging. I sold Arc Air for many years and it's tried and true but for smaller projects I'd still vote for plasma or chamfer arc rods.
Reply:Originally Posted by Brand XPrecision plasma is where it shines above all other processes. Being able to gouge out the top of a spot weld without going into the base metal is quite something .Small weld beads/thin base stock are another great use of plasma gouging.. I like air arc, but sold mine off, because thinner type metal is mostly what I work with..
Reply:I spoke with 2 different AirGas reps last week regarding the question I posted here. They didn't have an answer to why it was happening, only that I needed to grind out the root. Thats fine, but it is extra work I'm not looking to do. We make things that you drag in the dirt. This is not structural code work. The material thickness is usually small enough that I would need to take the root out, back fill with short circuit and then spray arc a cover pass. More heat and stress to the parent metals of parts that are generally over welded to begin with.  With carbon arc i can gouge, grind back and re-weld. The plasma gouge process may be fine for back gouging or making grooves. I just don't see a lot of place for it in rework. IDK, I could be wrong.  Im going to set it all back up and do more testing under a more controlled setup.