Have you reviewed the scope for each material specification?
A 376 SPECIFICATION FOR SEAMLESS AUSTENITIC STEEL
PIPE FOR HIGH-TEMPERATURE CENTRAL-STATION
SERVICE
1. Scope
1.1 This specification covers seamless austenitic steel
pipe intended for high-temperature central-station service.
Among the grades covered are five H grades and two
nitrogen grades (304N and 316N) that are specifically
intended for high-temperature service.
Seamless pipe and power plant applications
A312 SPECIFICATION FOR SEAMLESS AND WELDED
AUSTENITIC STAINLESS STEEL PIPES
Scope
1.1 This specification covers seamless, straight-seam
welded, and heavily cold worked welded austenitic stainless
steel pipe intended for high-temperature and general
corrosive service.