WELDING P11 WITH P91 STEEL

[DDN VERMA]

Dear Sirs,

I read several methods to join a P11 [1.25 Cr- 1/2 Mo] pipe to P91 [9Cr - 1 Mo] pipe, such as :

1. Weld using filler metal corresponding to corresponding to [2-1/4Cr - 1Mo] steel & post weld heat treat at appropriate temp..

2. Butter P91 with  filler corresponding to  [2-1/4Cr - 1Mo], post weld heat treat & weld with P11 & re-post weld heat treat it.

3. Use a P22 pup piece to join P11 with P91, etc. etc.....  

However, I wish to know, which is the most appropriate method taking into considerations the overall weld-integrity and high temperature strength of the weldment.

Please help to clarify my doubts.

THANKS,

DDN VERMA

[José Juan Jiménez Alejandro]

Construction Code?

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[Ghafor Mohamad]

Hi..

Good question.. I would like to add possible option say that we qualify a PQR joining the P11 with P91 with the B2 or B6 electrode and make full destructive test to evaluate the weld soundness and the weldability...

Once we have valid PQR and pass all the test consider that sufficiently enough be used at Site.

I know this not the right solution but maybe an option from the Contractor who like to take advantage..

Thanks
Ghafor

[Kannayeram Gnanapandithan]

Weld p22 and P91 (Pup piece) and SR. Then join p11 with p22. 

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[munee...@gmail.com]

Firstly, I do not understand the consequences of all 3 for what is the purpose?

Secondly, ok if you are doing butter there may be some purpose but scenario 1 and 3 why?

I feel like scenario 3 pub piece for tie in? Or shut down? If this is the case I agree with scenario 3.

Or

Scenario 1.

Still the questionnaire has deep knowledge of scenario than the one who is giving answer, to be precise, need more clarity for more information.

Regards,

 

Muneeb.M

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[Kannayeram Gnanapandithan]

When u weld P11 directly with P91 and then SR at 760°C will be very close to Lower critical temperature of P11 material. So better to have pup piece in between them. 

[Mohamed Muneeb]

Welding with pup piece you get one similar and one dissimilar obviously you will have two Weld joints, in this case you have to have two pqrs or you have to prepare a dissimilar pqr incorporating similar, possible? with pwht values within the tolerances? Filler etc? 

Welding without pup piece Piping we have did same scenario with dissimilar pqr for power generation high steam boilers. 

[munee...@gmail.com]

I agree, last time which we did was P91+P22, but not with the combo of P91+P11, below are the listed qualified, so as per below trailing mail we have to go for pub piece.

These are the combo we made PQR.

Grade

P-No

P11 + CS	P4+P1
P11 + CS	P4+P1
A 312 + A 106 Gr.B	P1+P8
A 312 +  P11	P8+P4

P22+P11	P5A+P4
P91+P22	P-No.15E+P5A
A 312 + P22	P8+P5A
A 312 + P22	P8+P15E
P11 + CS	P4+P1
P22+P11	P5A+P4
P22+ CS	P5A+P1
P91+P22	P-No.15E+P5A

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[sandeep kumar]

interesting query. Thanks for sharing.

The first think, why you need P11 to P91 joint? certainly you are going to have inferior properties on P11 side, so joint should withstand the P11 properties which can be achieved using welding with E8018-B2.

Now, while the recommended PWHT temp for P11 is 690 ± 15°C, its 740 ± 15°C for P91 material.

So, ideally a preheat temp of 200 to 250°C followed with a PWHT at 715 °C for longer duration shall be helpful to SR and controlled hardness values.

To me, point 1 suits more. however point 2 & 3 could be case specific and are the possible solutions.

Thanks & regards

Sandeep Kumar