PWHT-vs-NonPWHT P3 material

Date 12-15-2005 19:35

I have been posed the following question: A subcontractor we use has potentially re-welded or repair welded over some P3 material which has already been PWHTed (1125°F). The question is would the as-welded filler material etch differently than the filler material that has already been PWHTed, obvisouly the same chemical composition? The welds would not be very large and have reportedly been ground flush. It is reported that the repairs were areas of undercut. The components are assembled and re-PWHTing is not an option. As you can tell from the tone of the email the contractor is dening the re-welding and our customer is questioning it. This is all happening over in Europe and I am just getting the questions via the phone. I do apologize but that is about all the information I have. My background is with nickel alloys and in that case it can be noticed, but I do not know about these alloys. Any help would be great?

By chall

Date 12-15-2005 19:43

If I was in your shoes, I would check the hardness of the welds in question and compare them to the hardness of a P3 weld you know was subject to the proper PWHT.

Charles.

ps - If you look in B31.3., Table 331.1.1, there is guidance on what the acceptable hardness is following PWHT. Remember though, unless it the specified code, it may only be used as guidance.

By Benesesso (*)

Date 12-16-2005 00:07

What should be your primary concern is the heat-affected-zones (HAZ) of any post PWHT welds. You can use a portable "Equotip" type hardness tester-they are very accurate in the right hands. The actual new weld-metal hardness will NOT give you meaningful answers.

By chall

Date 12-16-2005 12:58

Actually, hardness values of the weld metal and HAZ (as close as possible to the edge of the weld) should be evaluated. This is a requirement from B31.3, section 331.1.7.

If it is suspected that localized welding took place to correct undercut on a joint after the joint was PWHT; than meaningful data could actually be obtained by comparing the "repaired" area to the "non-repaired" area of the same joint (provided there is sufficient distance between the two areas).

Charles