This 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. Mechanical tests shall be conducted on the material, namely: impact testing, tension testing, and hardness testing.
1.1 This specification covers alloy steel boltingfor pressure vessels, valves, flanges, and fittings forlow-temperature service. See Specification for the definition of bolting. The bars shall be hot-wroughtand may be further processed by centerless grinding or by colddrawing. Austenitic stainless steel may be solution annealed orannealed and strain-hardened. When strain hardened austeniticstainless steel is ordered, the purchaser should take special careto ensure that Appendix X1 is thoroughly understood.
1.2 Several grades are covered, including bothferritic and austenitic steels designated L7, B8, etc. Selectionwill depend on design, service conditions, mechanical properties,and low-temperature characteristics. The mechanical requirements ofTable 1 indicate the diameters for which the minimum mechanicalproperties apply to the various grades and classes, and Table 2stipulates the requirements for Charpy impact energy absorption.The manufacturer should determine that the material can conform tothese requirements before parts are manufactured. For example, whenGrade L43 is specified to meet the Table 2 impact energy values at−150 °F[−101 °C], additional restrictions (such as procuring asteel with lower P and S contents than might normally be supplied)in the chemical composition for AISI 4340 are likely to berequired.
Note1—The committee formulating this specification has included severalgrades of material that have been rather extensively used for thepresent purpose. Other compositions will be considered forinclusion by the committee from time to time as the need becomesapparent. Users should note that hardenability of some of thegrades mentioned may restrict the maximum size at which therequired mechanical properties are obtainable.
1.3 The following referenced general requirementsare indispensable for application of this specification:Specification .
1.4 Nuts for use with bolting are covered in Section10 and the nut material shall be impact tested.
1.5 Supplementary Requirements are provided for useat the option of the purchaser. The supplementary requirementsshall apply only when specified in the purchase order orcontract.