Does the PWHT required for the CS to SS joint (vessel service -lethal; CS side of vessel is PWHTed).

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Yes, it is required. To avoid damage to corrosion resistance of the SS it is recommended to make a buttering of the CS welding end using 309 electrode and then PWHT the CS section. After the SS can be welded to the buttering without subsequent PWHT (Austenitic SS is exempt from PWHT).
mauro

Dear Gonzaga

Reference to your reply for carrying out the PWHT on dissimilar joint. I would like to know if any reference in ASME for requirment of PWHT. So as to convince the concern as to with what respect PWHT is required to be done.

Regards
Prashant

For the CS end buttered with SS see UW-2 and UCS-56: PWHT required.
For the buttered SS to solid SS see UW-2 and (PWHT required on C. & Low alloy only). In addition, from Table UHA.-32 Austenitic steel is exempt from PWHT. Mind that buttering with SS before welding to silid SS make the joint P8 with P8. It is not dissimilar anymore.
For sake of your client read also all recoomendations of UHA.
Mauro

qaqcmpm,

I can not agree to buttering of C.S. groove face with Gr. 309 and PWHT of this buttering as required for the C.S.

Acc. to UCS-56 you have to carry out PWHT at min. 595 °C (depends on the P-No. of C.S.). But stress relieving may only be carried out on austenitic welding consumables at temperatures up to max. 300 °C (572 °F) for this case (buttering of C.S.).

A right solution for your problem is:
-buttering of groove face of the carbon steel with Ni-base alloy
-Local PWHT as required for the carbon steel (including the buttering)
-welding of the SS to the buttered groove face of the carbon steel with Ni-base filler metal.

For more information please see may reply Oct 14, 2007 in this forum to a verry similar case.

_________________
Kind regards,
Juergen Fleischfresser