1.1 本规范涵盖了热加工合金钢和碳硼钢，旨在在端部淬火试验中达到有限的硬化深度。这些钢成分由添加到常规牌号的后缀字母“RH”标识。 1.2 一般来说，淬透性受限的钢（RH钢）在端部淬火淬透性棒的初始位置的硬度范围不超过5 HRC，不超过标准H型钢硬度范围的65%（规范 A304 )在拐点区域。通常，受限淬透性带遵循相应标准H带的中间。给出了4140级RH带与H带的比较示例 图1 . 1.2.1 以国际单位制或英寸-磅单位表示的值应单独视为标准值。 每个系统中所述的值可能不是完全等效的；因此，每个系统都应独立使用。将两个系统的值结合起来可能会导致不符合标准。 1.3 本规范以英寸-磅单位和国际单位制表示。但是，除非采购订单指定了“M”规格名称，否则材料将以英寸磅为单位供应。 1.4 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 hot-worked alloy and carbon-boron steels designed to attain restricted depth of hardening in the end-quench test. These steel compositions are identified by the suffix letter “RH” added to the conventional grade number. 1.2 In general, steels with restricted hardenability (RH steels) will exhibit a hardness range not greater than 5 HRC at the initial position on the end-quench hardenability bar and not greater than 65 % of the hardness range for standard H-band steels (Specification A304 ) in the inflection region. Generally the restricted hardenability band follows the middle of the corresponding standard H-band. An example of the RH band compared with the H band is given for Grade 4140 in Fig. 1 . 1.2.1 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 non-conformance with the standard. 1.3 This specification is expressed in both inch-pound units and SI units. However, the material will be supplied to inch-pound units unless the purchase order specifies the “M” specification designation. 1.4 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.