A193 specification covers alloy steel and stainless steel bolting material
for pressure vessels, valves, flanges, and fittings for high temperature or high
pressure service, or other special purpose applications.Several grades are
covered, including ferritic steels and austenitic stainless steels designated B5, B8,
and so forth. Selection will depend upon design, service conditions, mechanical properties, and high temperature characteristics.Material according to
ASTM A193 B7 is often available in national coarse (UNC) thread pitches,
if being used in traditional applications, threads are specified 8 threads
per inch (tpi) for diameters above one inch.

ASTM A193, Grade B7 - a heat-treated chromium-molybdenum steel widely used for medium high-temperature service.