American Welding Society Forum
A pipe welder was qualified on P5B base metal (GTAW+SMAW process with backing gas for GTAW), does he qualify to weld on P1 base metal with the same welding process(without backing gas for GTAW process), the F No. of the filler metal used for both P5B and P1 are the same (eg F6 for GTAW and F4 for SMAW)
Need someone to advise...
No for the GTAW portion. The deletion of backing gas for GTAW is an essential variable for welder qualifications (QW-408.8). The GTAW portion of the weld serves as metal backing for the SMAW portion in both cases, so the SMAW portion of the test is still valid for the production weld.
Thanks MBSims, what about the other way round,eg qualified for P1 GTAW+SMAW(without gas backing) ,does it qualify for P5B GTAW+SMAW(with gas backing),as the code never mention addition of gas backing is essential variables...
The addition of of either gas or metal backing is not an essential variable for SMAW or GTAW. A change in consumable inserts is however an essential variable for GTAW (QW-416)
Just a question to stir the pot so to speak, but if they had a qualified procedure that used backing gas even if it wasn't needed would the welder be qualified then? I have worked for one company fabricating refrigeration piping any they required backing gas on all GTAW welds.
Welder qualification variables are entirely independent of anything that is or isn't required by a WPS. Except of course the statemtn "maximum to be welded".
meaning this welder is qualified to weld P No.5B pipe material(GTAW+SMAW with gas backing for GTAW)?? my understanding is those able to weld P No.1 pipe material(GTAW+SMAW) doesn't mean that he is capable to weld P No.5B pipe as welding of P No.5B pipe require a highly skilled welder especially on the root pass by GTAW process....
There is so little welding skill variance between 70S-X wires and B9 that it is almost irrelevent. Almost. The B9 will be slightly more viscous due to the alloy content, and is slightly more difficult to make fuse with an open root landing, but for most welders it is probably unrecognizable. There is certainly far less difference than between 70S-X and stainless steels, which of course are also F6's.
The difficulty with B9 fillers (welding Grade 91) is the knowledge to maintain the proper heat regime during welding and the greater tendency of B9 fillers to hot crack. This is not unlike the issue of welding titanium. The actual welding skill involved is not any greater than it is for carbon steel (though it is different). Its the prep and cleanliness that is absolutely critical.
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