MATERIALS-STUDBOLTS ASTM A320
ASTM A320 specification covers alloy steel bolting materials for pressure vessels, valves, flanges, and fittings for lowtemperature service. Each alloy shall conform to the prescribed chemical composition requirements. The material, as
represented by the tension specimens, shall conform to the requirements as to tensile properties such as tensile
strength, yield strength, elongation, and hardness. The material shall meet the prescribed impact energy absorption
requirements and the recommended test temperature. According to ASTM A320 mechanical tests shall be conducted on
the material, namely: impact testing, tension testing, and hardness testing.
Inside ASTM A320 several grades are covered, including both ferritic and austenitic steels designated L7, B8, etc.
Selection will depend on design, service conditions, mechanical properties, and low-temperature characteristics
The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI
units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be
used independently of the other. Combining values from the two systems may result in nonconformance with the
specification. Like the ASTM A193 specification, unless otherwise specified, the 8UN thread series is specified on fastener
larger than 1 ” in diameter.
Low temperature
service
ASTM A320 L7 Alloy steel, AISI 4140/4142 Quenched and tempered
ASTM A320 L7M
ASTM A320 L43 Alloy steel, AISI 4340 Quenched and tempered
ASTM A320 B8 Class 1 Stainless steel, AISI 304, carbide solution treated
ASTM A320 B8A
ASTM A320 B8T
ASTM A320 B8TA
ASTM A320 B8C
ASTM A320 B8M Class 1 Stainless steel, AISI 316, carbide solution treated
ASTM A320 B8MA
ASTM A320 B8cl2 Stainless steel, AISI 304, carbide solution treated, strain hardened
ASTM A320 B8Mcl2 Stainless steel, AISI 316, carbide solution treated, strain hardened
