PWHT for SA-266 Gr.3 of TS and tubes of SA-213 T9 2

[mechengineer]

Hi,

For SA-213 T9 (P-No.5B, Group No.1) tubes, it is an 9Cr–1Mo steel. According to ASME Ⅷ-1 UCS-56 Table UCS-56-4, the tube joint needs to undergo PWHT at the minimum heat treatment temperature of 675℃.

The material of tubesheet is SA-266 Gr.3 (P-No.1, Group No.2). According to ASME Ⅷ-1 UCS-56 Table UCS-56-1, the minimum PWHT of the tubesheet is 595℃. At the same time, the heat treatment process of tubesheet will adopt quenched and tempered, with the optimal tempered temperature is 620℃～630℃.

If PWHT is carried out according to the SA-213 T9, will it damage the properties of SA-266 Gr.3 material?

Regards,

 

[Dhurjati Sen]

No, as the holding time at 695°C is very less.

DHURJATI SEN
Kolkata, India

 

[Christine74]

I don't know the answer to your question but I would be very cautious about taking anyone's advice here if they don't provide explanations/citations. For whatever reason some of the most confident posters here are basically clueless.

Once tool that can be used to assess a poster's credibility is simply clicking on their profile and looking at the ratio of "Votes Received" to "Total Replies" in the forum in question. The higher the ratio the more credible the poster. It's not perfect but it's worth taking into account when someone presents themselves as an Authority.


-Christine

 

[fleischfresser]

I want to avoid being unpolite, but the answer of DhurjatiSen is a bit too simple.

A joint from P-No. 1 to P-No.5B is an unusual combination of materials. Normally a P-No. 4 transition material is used. But this does not work for tube to tubesheet welds. Some other Pressure Vessel Codes (e.g. German AD data sheet, EN 13445) have very specific requirements for PWHT of joints of dissimilar ferritic steels.
The minimum PWHT temperature of the P-No. 5B exceed the lower critical temperature of the lower P-No. 1 and could therefore have a detrimental effects on the properties.

Back to ASME VIII/1
The old requirement of UW-40(d)
“ When pressure parts of two different P‐Number Groups are joined by welding, the postweld heat treatment shall be that specified according to either UCS-56 or UHA-32, for the material requiring the higher postweld heat treatment temperature.”
was replaced since Edition 2017 by
“It is recognized that some postweld heat treatments may have detrimental effects on the properties of some materials. When pressure parts of two different P-Numbers are joined by welding, engineering judgment shall be applied when selecting the postweld heat treatment temperature and holding time to produce material properties suitable for the intended service. ..”
That means it is not required to perform the PWHT at temperature required for P-No- 5B.
I strongly recommend performing the PWHT at temperature lower than required for P-No. 5B.

However according to ASME VIII/1 you have to had objective evidence that the joint after PWHT has sufficient properties. Therefore you need the results of the PQR and of the simulated heat treated specimen as required by UCS-85.


Regards - Juergen