1.1 本规范涵盖电解镀有铬和氧化铬的单还原和双还原锡轧机黑板。该钢以卷和切割长度提供，用于制造罐头、封口、牙冠和其他产品。 1.2 本规范适用于以英寸磅单位（如A657）提供的订单，其厚度为0.0050至0.0149英寸，或以SI单位[如A657M]提供的厚度为0.127至0.378毫米。 1.3 以英寸磅或国际单位制表示的数值应视为标准。在正文中，国际单位制显示在括号中。每个系统中规定的值并不完全相等。因此，每个系统必须独立使用。 将两个系统的值结合起来可能会导致不符合本规范。 1.4 本标准并不旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.5 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 single- and double-reduced tin mill black plate electrolytically coated with chromium and chromium oxide. The steel is furnished in coils and cut lengths for use in the manufacture of cans, closures, crowns, and other products. 1.2 This specification is applicable to orders in either inch-pound units (as A657) which is supplied in thicknesses from 0.0050 to 0.0149 in. or in SI units [as A657M] which is supplied in thicknesses from 0.127 to 0.378 mm. 1.3 The values stated in either inch-pound or SI units are to be regarded 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 this specification. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 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.