Stainless steel 321H fatigue creep high temperature

Question

Stainless steel 321H fatigue creep high temperature

extragol1A (Civil/Environmental)

(OP)

23 Aug 19 18:18

Hello to everyone,
I have a question about stainless steel 321H at high temperature.
I have a vessel designed in accordance with ASME VIII DIV.1 at 585°C, pressure of 10 barg and diameter of 12".
It is subjected to fatigue cycles, with 1 cycle of temperature from 250 to 500 every day for 8 years.
If i read from ASME IID for ASME VIII div1 I don't have a creep problems, because creep starts from 595°C, But for doing fatigue analysis if I use ASME VIII DIV.2 I don't have curves for temperature higher than 427°C (800 °F) so I can't do fatigue check for series 3XX.
Is it correct that 321H doesn t have creep problem up to 595°C?
How Can I do fatigue check at temperature higher than 800°F without creep problem?

Many thanks

ironic metallurgist (Materials) · Answer 1 · 2019-08-23 20:21:15

extragol1A,
The problem you describe is a difficult one to analyze and probably beyond the capability of this forum.
I recommend you get in touch with a reputable engineering service company specializing in fitness-for-service and life assessment.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

TGS4 (Mechanical) · Answer 2 · 2019-08-23 21:56:08

It's not that creep starts at that temperature, it's that temperature is where creep governs the allowable stress. But what matters more than three design temperature is the maximum operating temperature.

Nevertheless, the advice by ironic_metallurgist is spot on, and should be followed.

extragol1A (Civil/Environmental) · Answer 3 · 2019-08-24 08:47:33

Many thanks for your answers!
I Will do it like you told me!
Can you advice me a book where I can study better the material behaviour to high temperature and creep fatigue problem?

XL83NL (Mechanical) · Answer 4 · 2019-08-24 13:58:17

Get a copy of this one
https://www.amazon.com/Design-Analysis-Boiler-Pres...

extragol1A (Civil/Environmental) · Answer 5 · 2019-08-25 17:03:24

Thank you!
TGS4 Can you explain me better what do you mean when you say:
"It's not that creep starts at that temperature, it's that temperature is where creep governs the allowable stress"?

TGS4 (Mechanical) · Answer 6 · 2019-08-25 22:25:32

There's more information in API 579-1/ASME FFS-1. Table 4-1 indicates that the start of the creep regime for this material is at 538°C. This is the temperature where creep is no longer negligible. It's only at the higher temperatures where creep starts to govern the allowable stress in VIII-1, based on the criteria in Appendix 1 of II-D.

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Stainless steel 321H fatigue creep high temperature