ASME 8 Bolting

[welding1]

If I use an A320 B8 bolt in an ASME 8 vessel the max temperature it can see is only 100F, If I use an A193 B8 bolt it can see 1500F. Why is this as both bolts are basically 304 stainless steel, with identical UNS number and mechanical properties?

 

[prex]

It's a matter of reference specifications: A320 is for low temperature service, A193 for high temperature service.
I agree that the two are quite similar, especially for austenitic steels, but the fabricator has to choose one and to fulfil it.

prex
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