we use TGS-2CM TIG wire and A407(AWS E310) welding consumable to weld P91+P22.After test,we found the C content of the area near P22 side is too low(Carbon poor). What caused the result? is it the time of PWHT too long,the dilute rate too large,and the alike? How to weld them?
Any response will be appreciated. Many thanks.
Without knowing what your working on and the code your welding to. (PWHT is governed by code) It's hard to give input. P91 to P22 would not normaly use this filler material that you referenced. But it sounds like you might be welding a tube sheet or something like that ,so I would recomend this web site, kobelcowelding.com and see if they can help you.
thanks
Jim
I mean tube to tube or pipe to pipe butt welding.The time of PWHT is 2.5 hours.Another question, for A106 GrB to ASTM A335GR P11,how to choose the welding material?It is also ease to lead to carbon migration from the A106 GrB side.
If it is pipe to pipe, and it is P22 to P91 then normaly it's ER90sB9 for GTAW and E9018B9 for SMAW. It's very inportant that you have qualified WPS's for this material. If this is in a steam generating system like a power boiler, these two materials especialy the P91 need to be welded correctly and can be a challenge to weld, so getting your information on how to weld them off a forum is not the way to go. As for the A106 GrB to 1.25 chrome (P11) you would normaly use ER80s2 for GTAW and E8018 for SMAW. Again there are other varibles to consider like pre-heat, PWHT that would be addressed on a WPS. Whatever code your working to needs to be brought into the mix also.
Thanks
Jim
Sounds like carbon migration. In dissimilar welds at elevated temperatures, carbon tends to migrate from the side with lower chromium content to the side with higher chromium. In this case from the P22 HAZ to the E310 weld metal. If you take a cross-section of the weld and HAZ, prepare it for metallographic examination and examine the P22 HAZ along the fusion line, you will likely see a decarburized zone. Inconel weld deposits are less prone to cause carbon migration than stainless steel, so the chromium difference is not the sole cause. We would normally use the P91 filler/electrode to make a weld between P91 and P22.
If the time of PWHT is too long,will it lead to carbon migration?In addition,can I choose Nickel-base electrodes?Or,adding a buffer zone on the P22 side?
I would not call 2.5 hours "too long" for P91. Rather than focusing on the PWHT time, it would be better to focus on the correct filler metal. Nickel-base electrodes are not really needed for welding P91 to P22. A 9% Cr electrode would have much lower tendency to promote carbon migration than one with 20-25% Cr.
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