【国外标准】 Standard Specification for Steel Castings, Ferritic and Martensitic, for Pressure-Containing Parts, Suitable for Low-Temperature Service

This specification covers steel castings for valves, flanges, fittings, and other pressure-containing parts intended primarily for low-temperature service. Several grades of ferritic steels and one grade of martensitic steel are covered. All castings shall receive a heat treatment proper to their design and chemical composition. It should be recognized that liquid quenching of the ferritic grades is normally required to meet the mechanical properties of heavier sections. The steel shall conform to the requirements as to chemical composition specified. Tensile test and impact test shall be made to conform to the requirements specified.1.1 This specification2 covers steel castings for valves, flanges, fittings, and other pressure-containing parts intended primarily for low-temperature service.1.2 Several grades of ferritic steels and one grade of martensitic steel are covered. Selection of analysis will depend on design and service conditions (Note 1). The temperature shown is the lowest temperature at which the material ordinarily is required to meet the impact requirements of this specification (see Supplementary Requirement S51, Impact Test Temperatures). Users should note that hardenability of some of the grades mentioned may restrict the maximum size at which the required mechanical properties are obtainable (see Appendix X1).Grade Usual Minimum TestingTemperatures, °F [°C]LCA −25 [–32]LCB −50 [–46]LCC −50 [–46]LC1 −75 [–59]LC2 −100 [–73]LC2-1 −100 [–73]LC3 −150 [–101]LC4 −175 [–115]LC9 −320 [–196]CA6NM −100 [−73]NOTE 1: This specification covers the low-temperature requirements particularly pertinent for ferritic and martensitic steels. Certain grades of austenitic steel castings furnished in accordance with Specification A351/A351M have been found suitable for low-temperature service down to −300 °F [−184 °C] and others down to −425 °F [−254 °C]. These grades may be used when impact tested in accordance with Specification A352/A352M with energy levels and temperatures of test mutually agreed upon between the purchaser and the manufacturer. As a guide to the selection of energy levels and testing temperatures, Appendix X1 should be consulted.1.3 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. Inch-pound units are applicable for material ordered to Specification A352 and SI units for material ordered to Specification A352M.             1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.