welding of Duplex stainless steel 1

[Lahane]

I have to weld a Duplex stainless steel of P no. 10H .The desing code is ASME B31.3.Code says "PWHT neither required nor prohibited".
How to interprete this statement?
I heard that control of heat input is very essential in welding of Duplex steel.Shall i need to do a PWHT? if yes what PWHT cycle i need to follow? which consumalbes are suitable to weld these by GTAW & SMAW process.
The application is SOUR & Impact test is required in PQR
Thanks in advance.

 

[metengr]

lahane;
"PWHT neither required nor prohibited". This is code language for PWHT is not recommended. If PWHT is decided on duplex ss joints, reheat treatment would only be permitted.

 

[Lahane]

Do you think that i should not go for PWHT then.

 

[mcguire]

PWHT of duplex runs a high risk of embrittlement from alpha prime precipitation unless its a very lean duplex like 2003. Unless you can do a full solution anneal and quench, forget about it.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[Lahane]

Michael,

So you recommend that i should not go for any PWHT,simply weld it & test it?
What about the suitable cosumables?

 

[21121956]

Hello everybody:

lahane, maybe this document can be of some help for you.

http://www.stainless-steel-world.net/pdf/SSW_DEC07_fluor_LR.pdf

 

[mcguire]

There are better experts on consumables than me. I'll defer.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[EdStainless]

http://www.imoa.info/_files/stainless_steel/Duplex_Stainless_Steel_2d_Edition.pdf

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[Guest102023]

PWHT is definitely NOT recommended for any duplex SS. In fact the service temperature is limited to ~600°F IIRC.

The only option is solution heat reating (expensive). If you have welds they should have been made with what I call a 'non-matching matching' filler metal. The short version of that means that if you re-heat treat, the weld and the base metal will have significantly differing ferrite contents, one of which may be out of spec.

Welding duplex SS is one of the reasons I got out of the manufacturing end of welding engineering ...

 

[weldtek]

I agree with the posts above. PWHT is not recommended for Duplex SS. Solution heat treatment is generally not a good option for weldments nor is it necessary.
The challenge you face is to develop a good welding procedure, but, there's plenty of help avaialble through the technical departments of reputable consumable manufacturers.

 

[strider6]

This is taken from :
Duplex stainless steel welding: best practices

http://www.stainless-steel-world.net/pdf/SSW_DEC07_fluor_LR.pdf

"Post-Weld Heat Treatment (PWHT) and Cleaning PWHT of DSS is generally not required but may be necessary when detrimental amounts of intermetallic phases have formed. Typically, a full solution anneal followed by a water quench should be considered"

S

Corrosion & Rust Prevention Control

 

[TomEun]

Please do not apply the PWHT unless the PQR and products with PWHT as solution annealing is approved by the end-user.

If the piping requires the PWHT for base metal per codes or end-user’s specification, the best solution may be to avoid the DSS.
For instance, when CS with DSS clad is required PWHT per code, you may have to use solid DSS without PWHT or CS with other clad material followed by PWHT.

Thomas Eun