Anyone use Carbon Arc Gouging ? 8

[tc7]

Is anyone familiar with carbon arcing for material removal associated with weld repairs and gouging? I can't find mention or it in AWS or Mil specs (I don't even know where to begin reading for ASME guidance). I have been told by some of the seniors that it is an old process, not practiced anymore due to excess carbon migration causing subsequent weldment problems.

I'd like to revitalize the process in our plant and refine it if possible. If AWS is silent on the process, then does that mean I can use it? Is a WPS required ? What precautions are advisable? Typical materials will be all manner of carbon steels as well as SS.

Thanks for all comments, references.

 

[HgTX]

AWS D1.5 allows air carbon arc gouging and has a lot to say about it (including some restrictions such as needing to grind afterward in some situations, or use preheat).

Hg

Eng-Tips policies: faq731-376

 

[gtaw]

I am looking at AWS D1.1-2002. It's the one handy on my desk top this morning!

Paragraph 5.15.1.1, 5.15.2, 5.15.4, and 5.15.4.1 address thermal cutting and gouging processes. No prohibitions are noted. However, 5.26 does prohibit oyxgen gouging of quench and tempered steels.

I've used air carbon arc gouging for many years on structural steel to remove welds and to facilitate repairs. The only word of caution I would offer is that you have your "gougers" dmonstrate they can use the equipment before you "turn them loose" on production work. In the hands of the wrong person, they can do untold damage. However, that's the case with any process. Have you ever seen what a screwdriver can do to wood molding in the hands of the wrong person?

AWS does have a recommended practice for carbon arc cutting - air. There are some excellent pointers in that publication if you are unfamilar with CAC-A.

Best regards - Al

 

[unclesyd]

Carbon Arc Gouging (CAG) is alive and well.
If properly used there is very little problem with carbon pick up by the material being cut. I have to qualify this a little by saying that the gouging has to be done by a competent operator well versed in the art of CAG. It has been my experience that the majority of the operators doing CAG haven't a clue as to what's needed to make successful cut or prep for weld repair. We don't give the CAG job to newest man on the team.
I've used properly executed CAG for weld prep on new and in service equipment for over 35 yrs in Austenitic SS equipment where the process dictates that the C content be controlled at extremely low levels.


Here is some literature from Thermadyne for the use of the ArcAir line of CAG equipment and consumables. Iwould give them a call for additional information.

http://www.thermadyne.com/twecoarcair/literature/pdfs/section/89_250_008.pdf

 

[tc7]

Wow - thankyou for rapid resposes. Stars for everbody!!!

I was given the idea that "carbon" arc gouging was such an old technology that the AWS references for "gouging" did not include this!! So then, I am left with two questions for now:
1. a WPS does or does not need to be qualified? (I fully understand operators will need to be trained and checked.)

2. how is the best way to check residual carbon after we're done excavting an area?

 

[gtaw]

The applicable code will address the need to demonstrate the gouging process. I believe it is a military welding standard that includes a requirement that the method of back gouging involving thermal cutting/gouging employed be included when qualifying the WPS. However, I don't believe AWS or ASME require it to be included in the qualification process.

I don't believe carbon pickup is a "real" problem. What many people attribute to carbon pickup is really surface oxide. Grinding the gouge back to "bright metal" will remove the surface oxide and any carbon that may have diffused a couple of angstroms into the base metal.

Best regards - Al

 

[unclesyd]

The isn't any real world method for a quick check for residual C on the cut surface other than visual. If the CAG isn't done properly at times you can see pieces of the gouging rod stuck to the metal being gouged. Other times you will see smut on the surface of the cut, easily removed, for same reasons as above.

When we switched from iron powder cutting of Austenitic SS to CAG we did multiple corrosion tests, both laboratory and in service coupons along with microstructural analysis. Once we had established the proper procedures for CAG we essentially did away with extensive grinding other than to correct the geometry.

 

[pipewelder1999]

Some of the things to think about when using the process .

1) HOTTER is NOT better. Some people have an idea that more amperage means easier operation. That is not correct. Like electrodes for welding, there are amperage ranges for Air Carbon Arc Gouging.

2) The hand eye coordination needed for gouging is similar to that needed for welding. Just because you have the equipment does not mean you have the ability. It does take some practice.

3) The air should be clean and dry. The air jets MUST be blowing air between the electrode and the base metal.

4) Bigger rods make a nice radius for welding.

5) Because the metal that is blowing out also helped form the arc, slowing down to much may cause the arc to go out. Get comfortable enough to travel at an even speed. The process should sound like a steady noise and not a series of random short bursts.

6) Wet or damp electrodes can be a pain to use.

7) There are different electrodes for some different metals and they may also operate on differenct currents and polarities.

In my opinion, there is NOT a better metal removing tool.





Gerald Austin
Iuka, Mississippi

http://www.weldinginspectionsvcs.com