1.1 本规范 2 涵盖几种等级的碳钢和低合金钢锻造或环轧法兰、锻造配件和阀门，主要用于低温使用并需要缺口韧性测试。它们是按照规定的尺寸或尺寸标准制造的，例如第节中引用的ASME和API规范 2 尽管本规范涵盖了一些由轧制棒材和无缝管材加工而成的管道部件（参见 5.3.3 ），不包括以这些产品形式生产的原材料。 1.2 不打算对尺寸进行超出制造商获得规定要求的能力的限制。然而，LF787级的3级仅在淬火和沉淀热处理条件下可用。 1.3 当需要额外的测试或检查时，提供了补充要求。这些仅适用于买方在订单中指定的情况。 1.4 本规范以英寸-磅单位和国际单位制单位表示。但是，除非订单规定了适用的“M”规格名称（SI单位），否则材料应按英寸-磅单位提供。 1.5 以SI单位或英寸-磅单位表示的值应单独视为标准值。在正文中，国际单位制单位显示在括号中。每个系统中陈述的值可能不完全等同；因此，每个系统应独立使用。合并两个系统的值可能导致不符合标准。 1.6 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》中确立的国际公认的标准化原则制定的。

1.1 This specification 2 covers several grades of carbon and low-alloy steel forged or ring-rolled flanges, forged fittings and valves intended primarily for low-temperature service and requiring notch toughness testing. They are made to specified dimensions, or to dimensional standards, such as the ASME and API Specifications referenced in Section 2 . Although this specification covers some piping components machined from rolled bar and seamless tubular materials (see 5.3.3 ), it does not cover raw material produced in these product forms. 1.2 No limitation on size is intended beyond the ability of the manufacturer to obtain the specified requirements. However, Class 3 of Grade LF787 is only available in the quenched-and-precipitation heat treated condition. 1.3 Supplementary requirements are provided for use when additional testing or inspection is desired. These shall apply only when specified by the purchaser in the order. 1.4 This specification is expressed in both inch-pound units and in SI units. However, unless the order specifies the applicable “M” specification designation (SI units), the material shall be furnished to inch-pound units. 1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. 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 non-conformance with the standard. 1.6 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.