What is the difference between A193 Grade B8 and A320 Grade B8?

ASTM A320/A320M is a standard specification for alloy steel and stainless steel bolting for low temperature service. ASTM A320 Grade B8 Class 1 bolts and threaded studs are manufactured from AISI 304 stainless steel. These bolts are heated and then water-quenched through carbide solution treatment, or solution annealing, which ensures the bolts are corrosion resistant. A320 Grade B8 Class 2 bolts are annealed and strain hardened to achieve increased strength characteristics. These bolts do not require an impact test.

ASTM 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.

A320 Grade B8 Bolt

Selection will depend upon design, service conditions, mechanical properties, and high temperature characteristics.Material according to ASTM A193 B8 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 B8 Class 1 Stainless steel, AISI 304, carbide solution treated.

ASTM A193, Grade B8 Class 2 Stainless steel, AISI 304, carbide solution treated,strain hardened.