P92 1

[alanisphoenix]

Using the CNB and Cr equivalent/ Ni Equivalent, Any one knows what is the value of those formules to guarantee that there are now ferrite delta on the structure of the P92?
I haver read so many about the P91, but can i use the same limits of the P92?, it has more W, so that increase the results. Any experience, or any article/book, when i could found more information.

Thank you

 

[metengr]

No, the same limits do not directly apply. I would suggest you follow the chemical composition ranges as stated for the ASME Code Case 2179-7 for Grade 92.

 

[metengr]

If you don't have access to the ASME B&PV Code Case, see the attachment below regarding general information. This is a decent presentation on use and background information on CSEF for Grade 91, and Grade 92.

http://ccusers.org/wp-content/uploads/2012/10/EISENBISE-High_Energy_Piping_Presentation.pdf

 

[alanisphoenix]

thank you for your comments.
Yes i have then ASME and ASTM code, but as you know the ranges for each element at the chemical composition it quite big.

I know that to avoid ferrita delta at p91, the CNB has to be under 10 (or between 9.4-10.2), and the C+N better <0.12. but what about P92? thats something that the standards don't talk about. Using the same ecuations (CNB, CrEq, NiEq), the results of course are not the same for both grades, so where are the limits for P92?

any idea, any suggestions??

thanks for your help.

 

[metengr]

alanisphoenix;
The chemical composition ranges are necessary to provide flexibility – you never have specific values. As long as you remain within the stated chemical composition ranges, the resulting microstructure will be nearly all martensite upon rapid cooling, and thus will result in tempered martensite (after tempering) with the necessary dispersion of various carbides to ensure elevated temperature strength.

The Chromium-Nickel Balance formula (CNB) is an equation developed by Combustion Engineering based on a modification to the work of Newhouse et al. I have not seen a similar equation for Grade 92 only because one of the variables for the CNB equation is W, and since Grade 92 has increased W, substituted for Mo, this results in a problem for using the CNB for Grade 91. As I said, if you remain within the chemical composition ranges for the Code Case and you follow the specified heat treatment parameters you should have no concerns for delta ferrite formation.

 

[tamal1475]

Since 1% W is taken to be equivalent of 0.5% Mo as a ferrite stabilizer you may use this in the formula.

 

[metengr]

You are at your own risk using CNB.