The ASTM (formerly the American Society for Testing And Materials) creates standards for materials and fasteners. The ASTM A320 standard family is for steel and stainless steel bolts used in very low temperature environments. These bolts can be used in ship building and metal piping exposed to low temperatures, like oil pipes.
According to "An Introduction to the Design and Behavior of Bolted Joints," by John Bickford, the ASTM A320 standard bolts come in grades L7, L43, L7M, L1, B8 CL1, B8 CL1A, B8 CL2 and B8M CL2. ASTM A320 L7 can be designated ASTM A320 GR L7. ASTM A320 L7 bolts can come in grades 4 and 7.
ASTM A320 grade L7 bolts have a nominal size of ¼-inch to 2 ½ inches. The minimum yield strength of ASTM A320 grade L7 bolts is 105 kilograms per square inch (ksi). ASTM A320 grade L7 bolts have a minimum tensile strength of 125 ksi. ASTM does not give a minimum hardness for this grade of bolts.
According to "Metallurgy and Corrosion Control in Oil and Gas Production," by Robert Heidersbach, ASTM A320 L7 bolt standards permit them to be galvanised. The book "Nickel: An Industry on the Brink of Expansion," by Nnamdi Anyadike states that ASTM 320-L7 bolts can be electroless nickel plated.
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