Something to add to this GMAW discussion: I've performed quality control work and inspection at a large piping fabrication shop where they were using mainly STT GMAW because of the high production rates inherant with this welding process. There were mainy issues with lack of fusion or porosity in the root and the quality of welds being of concern. I've later talked with welding engineers and consultants who have said that any type of GMAW process, whether its STT or other, will be susceptible to these types of defects, especially in the root of the weld. I'm not saying it's impossible to perform but the welders must have very good training with the capabilities of the machines and they must be aware of the difficulties in root welding otherwise you will have a large quality "headache" on your hands. One possible solution is to grind away any weld starts that are suspect at having defects before welding over with the following passes (the welders at the shop I was working did not do this from what I could see and hence, likely propagated the problem). Regards, J.Z. Materials & Welding Engineer --- On Thu, 9/24/09, Vishal Mehta <vdm@supertechservices.in> wrote:
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