1.1 本规范涵盖了压力容器部件用低碳时效硬化镍铜铬钼铌合金钢锻件的要求。 1.2 本规范中的锻件可分为A级或B级。A级可分为以下一类或两类: 1.2.1 A级一级-- 正火和沉淀热处理，提供55 ksi[380的最小屈服强度 MPa]，最小抗拉强度为65 ksi[450 MPa]。 1.2.2 A级二级-- 淬火和沉淀热处理，提供65 ksi[450的最小屈服强度 MPa]，最小抗拉强度为75 ksi[515 MPa]。 1.2.3 A级是本规范中的原始钢成分。 1.3 尽管材料很容易焊接，但焊接程序至关重要，必须不会对材料的性能产生不利影响，尤其是在热影响区。预先假定焊接程序将适用于被焊接的材料。 1.4 补充要求，包括规范中适用的要求 A788/A788M ，以在需要额外测试或检查时使用。只有当买方在订单中单独规定时，这些规定才适用。 1.5 以国际单位制或英寸磅单位表示的数值应单独视为标准。每个系统中规定的值不一定是完全相等的；因此，为了确保符合标准，每个系统应独立使用，并且两个系统的值不得合并。 1.6 本规范以英寸磅和国际单位制表示。但是，除非订单规定了适用的“M”规格名称[SI单位]，否则材料应以英寸磅单位提供。 1.7 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。

1.1 This specification covers requirements for low-carbon age-hardening nickel-copper-chromium-molybdenum-columbium alloy steel forgings for pressure vessel components. 1.2 Forgings under this specification are available as Grades A or B. Grade A may be ordered in one or two classes as follows: 1.2.1 Grade A Class 1— Normalized-and-precipitation-heat-treated, providing a minimum yield strength of 55 ksi [380 MPa] and a minimum tensile strength of 65 ksi [450 MPa]. 1.2.2 Grade A Class 2— Quenched-and-precipitation-heat-treated, providing a minimum yield strength of 65 ksi [450 MPa] and a minimum tensile strength of 75 ksi [515 MPa]. 1.2.3 Grade A was the original steel composition in this specification. 1.3 Although the material is readily weldable, welding procedures are of fundamental importance and must be such as not to affect adversely the properties of the material, especially in the heat-affected zone. It is presupposed that welding procedures will be suitable for the material being welded. 1.4 Supplementary requirements, including those applicable in Specification A788/A788M , are provided for use when additional testing or inspection is desired. These shall apply only when specified individually by the purchaser in the order. 1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other and values from the two systems shall not be combined. 1.6 This specification is expressed in both inch-pound and SI units. However, unless the order specifies the applicable “M” specification designation [SI units], the material shall be furnished to inch-pound units. 1.7 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.