No allowable stress for alloy 20.
No allowable stress for alloy 20.
(OP)
Does anyone know why B31.3 does not list allowable stress values for alloy 20 N08020 beyond 800 F. Is this because of metallurgical embrittlement?
Want to replace a valve in fully-regnerative catalytic reformer regen gas service that was 12Cr originally. Want to do it with alloy 20 Cb-3 b/c no 12Cr (410 or CA15, CA6NM) available. Design temperature is 1000F.
Want to replace a valve in fully-regnerative catalytic reformer regen gas service that was 12Cr originally. Want to do it with alloy 20 Cb-3 b/c no 12Cr (410 or CA15, CA6NM) available. Design temperature is 1000F.





RE: No allowable stress for alloy 20.
What makes alloy 20 an alternate for 410? Sounds like a real jump to me.
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RE: No allowable stress for alloy 20.
RE: No allowable stress for alloy 20.
RE: No allowable stress for alloy 20.
The ASME B31.3 is somewhat eccentric in how it handles Alloy 20 - the N8020 has 800 F limit, and is grouped with the stainless steel materials. The cast version CN7M is grouped with the nickel materials and had 1000 F limit.
The composition of rolled material is somewhat different than the cast material, but does it warrant the different group or temperature limits?
If you are considering a valve substitution, then most likely the valve body would be cast CN7M, limit 1000 F.
RE: No allowable stress for alloy 20.