I have seen many welders, when welding with GMAW, repair major cluster porosity by turning up the voltage and wire feed speed and welding over the top of the porosity, claiming that it is repaired because the porosity is no longer visable and claiming to have burned it out. Any opinions?
I believe most codes require that any defect be removed. An example is Para 5.26.1.3 of AWS D1.1 1998.
The phrase "Out of sight Out of mind" does not apply here! If you put a Band-Aid over a cut, does that mean the cut is gone? I don't think so Tim.
It also begs another question, "What else do they weld over without telling you?". Cracks? If the porosity or any other discontinuity exceeds allowable limits it needs to be removed.
Porosity does not "burn out", it travels from weld pass to weld pass and never leaves the original weld pass. It must be removed by air carbon arc gouging and / or grinding.
I always wonder if the welders that like to "burn out" the porosity would want to make their "government" jobs that way. I'll bet they don't on the trailer hitch that will be pulling their camper.
If practical to do so make a porosity sample with a welded over repair and cross section it through the repair. The results might be convincing evidence on why not to do that.
CHGuilford
A welder doing a G-job? I guess that means alot Bar-B-Que grills will last for a long time, I know my has the best and prettiest welds I ever turned out.
I agree, there are some people out there that really believe they can burn out porosity. They need to be convinced otherwise.
I thank you all for your replys. This is something that I have been teaching and preaching to the welders that I am associated with, but it continues to happen.I am getting ready to give a couple of weld repair classes and wanted the welders to see how other proffesionals view this practice. I will be including a sample as suggested, in the class.
If your students do not respond to your research you can always pull out the D1.1 code book and prove it them that way.You can't argue with codes and standards.
By Merlin
Date 05-24-2001 21:34
Do they (your welders) realize that the only function of the gas in GMAW is to shield the arc, not to remove any form of contaminants as Flux would do in SMAW ect, to some extent. I do not think this is so much a code question as basic arc welding physics. I am not encouraging the welding over of discontinuities without proper removal and verification first. This part is where codes and procedures comes in.
OK I'm back know I'll get off my soapbox and go away
