A213 T91 starting microstructure

[replica]

Hi all,

I want to know regarding the stress data that shown in API 530 Figure E11. for A213 T91. As I was aware that for T91 there are at least 3 different starting as received/as supplied microstructure which the same chemical composition and processes (Normalised and Tempered). As we all know that creep properties in T91 is very sensitive to microstructure hence the different starting microstructure will give different creep properties. My question is

1. What starting microstructure is used to produce the data in API 530 Figure E11 for T91/P91.
2. Is not normal to ask the sample of microstructure and to specify cooling rate during normalising when purchasing P91 rather than only hardness and N+T heat treatment in order to obtain correct fully tempered martensite structure without ferrite.

Herewith attached 3 different starting microstructure for T91 that had met the requirement for hardness and N+T heat treatment.

Comments are welcome.

 

[davefitz]

weldstan,

This thread could go on forever if we list all the problems found in the field with P91. It is probably safe to say that every single fabrication detail needs to be evaluated to ensure the assumed code properties are provided , and that every single fabrication process can lead to sub-code properties if they are not properly evaluated and executed.

Just think, they are dreaming about using such creep strength enhanced ferritic components on the Gen IV nuclear reactors. A good career move would be toward that of a QA/QC inspector on such a project; the unit would take longer to build than TVA watts bar 2.

"Nobody expects the Spanish Inquisition!"

 

[davefitz]

In parallel with Meteng's notice of the new code case , there is a paper being provided at the July PVP conference ( Vancouver) by prof Maruyama et al ( PVP2016-63225) that describes recent long term creep testing results that imply a 40% reduction in long term creep strength ( 500,000 hrs at 550C)may need to be applied to the code stresses. Such a change in creep life prediction of installed P91 components will be somewhat disturbing, if consensus agrees with that finding.

"Nobody expects the Spanish Inquisition!"