Application temperature limits of SS 904L

[Josep Maria Perdigo]

Dear forum members,
I was surprised that the SA-312 grade 904L pipe has an application limit of 371°C (700°F) for ASME VIII-1, while in ASME B31.3 the limit drops to 260°C (500°F). Does anyone know the reason for this big difference?

 

[metengr]

This material can precipitate phases, like sigma, above 500 deg C in service which can adversely effect mechanical properties and corrosion resistance. The difference in maximum temperature application has more to do with code experience. These among other items are issues that have been around for years between standards committees.

 

[EdStainless]

There are versions of 904L stable to higher temps, but using the general chemistry the limits that you see are realistic.
When the phases form they not only greatly lower corrosion resistance but the toughness and ductility drop. The properties while hot are usually fine, but when the material cools it can be very brittle.

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P.E. Metallurgy, Plymouth Tube

 

[Josep Maria Perdigo]

Thanks metengr and EdStainless.
To complete the normative panorama, one more data: "EN 10216-5 Seamless steel tubes for pressure purposes" establishes a limit for intergranular corrosion of 400ºC for 1.4539, which is the European equivalent of 904L.
Summarizing:
ASME VIII-1, vessels: 371°C
ASME B31.2, piping: 260°C
EN 10216-5, vessels & piping: 400°C

Another thing is the compatibility of the 904L with the product content, at the design temperature finally chosen. That is the responsibility of the owner and his engineering.

 

[EdStainless]

The 260C seems to be unrealistically low, the 371C sounds right to me.
There are some good data sheets out there from producers.

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P.E. Metallurgy, Plymouth Tube

 

[metengr]

Regardless of what anyone thinks, B31.3 committee chose as a consensus committee to be more conservative based on their experience with materials. This is why you have differences and it will remain that way.