MATERIALS-STUDBOLTS ASTM A320 L7
ASTM A320 specification covers alloy steel bolting materials for pressure vessels, valves, flanges, and fittings for low-temperature 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.
ASTM A320, Grade L7 – This grade is intended for low-temperature service down to minus 150ºF and has a minimum Charpy impact value of 15 ft-lb at this temperature. Sizes 2-1/2 in. and under.