[PSUBS-MAILIST] Heads Question

[Sean T. Stevenson via Personal_Submersibles]

Dan - I was under the impression that the issue with GMAW (MIG) was the risk of porosity due to ineffective purge (both purging the opposite side of the joint on the root pass, and back purging the puddle while filling), and that it is perfectly acceptable if 100% gas purge is ensured and low hydrogen electrodes are used? The process is used in lots of pressure vessel manufacturing, but perhaps the pros have better control over this? 

I like the idea of a GTAW (TIG) root pass. Doing the filling passes with SMAW (stick) seems tedious, particularly if there is a lot of filling to be done, but your message is making me think twice. Is the major problem the embrittlement, or the porosity?

Sean
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