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 本规范下的锻件可分为A级或B级。A级可按以下一类或两类订购: 1.2.1 一级甲等- 正火和沉淀热处理，提供55 ksi[380]的最小屈服强度 MPa]和65 ksi[450]的最小抗拉强度 兆帕]。 1.2.2 二级甲级- 淬火和沉淀热处理，提供65 ksi[450]的最小屈服强度 MPa]和75 ksi[515]的最小抗拉强度 兆帕]。 1.2.3 A级是本规范中的原始钢成分。 1.3 虽然材料易于焊接，但焊接程序至关重要，必须确保不会对材料的性能产生不利影响，尤其是在热影响区。前提是焊接程序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 ，供需要额外测试或检查时使用。仅当买方在订单中单独规定时，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值。每个系统中规定的值不一定是精确的等价物；因此，为确保符合本标准，每个系统应独立使用，且两个系统的值不得组合。 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[国际单位制]，否则材料应以英寸-磅为单位提供。 1.7 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）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.