【国外标准】 Standard Specification for Steel Castings, Alloy, Specially Heat Treated, for Pressure-Containing Parts, Suitable for High-Temperature Service

This guide specifies standard specification for alloy steel castings, which have been subjected to special heat treatment, for valves, flanges, fittings, and other pressure-containing parts intended primarily for high-temperature service. All castings shall receive a heat treatment proper to their design and chemical composition. Heat treatment shall be performed before machining except in instances when reheat treating is necessary. The steel shall conform to the required chemical composition for carbon, manganese, phosphorus, sulfur, silicon, chromium, molybdenum, and vanadium. Steel used for the castings shall conform to the required tensile properties such as tensile strength, yield strength, and elongation. When methods involving high temperature are used in the removal of discontinuities, casting shall be preheated to at least the minimum temperatures.1.1 This specification covers alloy steel castings that have been subjected to special heat treatment for valves, flanges, fittings, and other pressure-containing parts (Note 1) intended primarily for high-temperature service.1.2 The high-temperature properties of the materials covered in this specification are dependent upon special heat treatment that is required. Although the high-temperature properties are not specified, they are implied by control of chemistry, heat treatment, and room-temperature properties.1.3 Two grades of ferritic alloy steel are covered (Note 2). Selection will depend on the design and service conditions, mechanical properties, and high-temperature characteristics.NOTE 1: Carbon steel castings for pressure-containing parts are covered by Specification A216/A216M. Alloy steel castings are covered by Specification A217/A217M.NOTE 2: The grades covered by this specification represent materials that are generally suitable for assembly with other castings or wrought steel parts by fusion welding. It is not intended to imply that these grades possess equal degrees of weldability; therefore, it is the responsibility of the purchaser to establish for himself a suitable welding technique. Since these grades possess varying degrees of suitability for resistance to oxidation and for high-temperature service, it is also the responsibility of the purchaser to determine which grade shall be furnished, due consideration being given to the requirements of the applicable construction codes.1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.1.5 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.