welding of P91 material to P1 materrial

[avs01]

For Steam Blow piping i have to weld P91 to Carbon steel A106 Gr B piping. I believe after post weld heat treatment at 750deg C as required By P91, carbon steel gets week and may crack. same may happen at elevated temperatures at steam Blow please give me ur openion.

 

[metengr]

avs01;
I would strongly suggest you use a transition piece of sufficient length between the Grade 91 and carbon steel. I would use P22 material (2.25% Cr-1% Mo) welded to Grade 91, PWHT. After this operation, you can weld the carbon steel to Grade 22, and perform a second PWHT, if required for the carbon steel to P22 weld joint.

 

[Mr168]

I would second metengr's suggestion. There are multiple issues associated with properly fabricating that joint, and you will not realize the benefits of the P91 material at the reduced PWHT range permitted by ASME. I just went through a similar situation on P91 spools designed to tie into a carbon steel valve, and resolved the issue by having P22 safe ends installed.

 

[MJCronin]

Steam Blow...??? modest pressure..??

How about a set of flanges of different materials ?

-MJC