Welding P5B (P91) With no internal purge

By David Lucas Date 03-16-2009 00:31

I have worked on P5B material using GTAW and these projects had trouble with this material. This past year I wrote and got a procedure qualified to weld P5B material with no internal purge. I think this will change the way we look at welding this material. If you want to read about it go to www.lucasinspection.com

By Jim Hughes (***)

Date 03-16-2009 01:44

Are you talking about GTAW or FCAW or RMD? Getting a procedure qualified per Sec. IX without purge is not realy the issue with P5B material. You can qualify a WPS for 300 series Stainless without purge using GTAW but what does that get you? Did you do any corrosion testing (G28), passivity and impeding oxidation build up are the issue. Oxidation of the back side of the root could hinder creep rupture ability of P5B which could go undetected for 100,000 hours of a power plant life.

Jim

By js55

Date 03-16-2009 13:38

Jim's right. Section IX Tensiles and bends will not be the problem. There is such conservatism (justifiably) involved in Grade 91 welding that it will take years of research to determine the effect on long term properties. And I doubt there will be much motivation in the short term to even try.
What is the effect of the 80% atmospheric CO2 on the precipitation, morphology and volume percentage of CrC, MoC, Nb/V/N carbo/nitrides.
Not saying it isn't worth looking at but I would suspect a good deal of conservative hesitancy here. I would also suspect that results of metallurgical analysis would tend to argue against leniency on this issue.