本SAE推荐规程所涵盖的钢具有通过淬火和回火处理获得的增强机械性能。Q550级为碳锰钢，而Q550B、Q620B和Q690B级为碳锰硼钢。其他等级（由后缀A指定）表示含有一种或多种额外合金元素的钢，以达到更高的强度和适应更大的厚度。这些钢是经过完全脱氧和细晶粒生产的。由于这些钢具有机械性能的特点，因此在选择等级时必须小心，尤其是在需要通过焊接或成型进行制造的情况下。 特殊程序可能适用于特定供应商生产的不同成分和截面尺寸；因此，买方应咨询生产商，以了解这些变量。本SAE推荐规程涵盖了结构用淬火和回火碳锰、碳锰硼和合金钢板的三种强度等级。

The steels covered by this SAE Recommended Practice have enhanced mechanical properties obtained by quench and temper treatment. Grade Q550 is a carbon-manganese steel, while grades Q550B, Q620B, and Q690B are carbon-manganese boron steels. Other grades (designated by suffix A) represent steels containing one or more additional alloying elements as required to achieve higher strengths and to accommodate greater thicknesses. These steels are produced fully deoxidized and to fine grain practice. Since these steels are characterized by their mechanical properties, care must be exercised in the selection of grade, especially where fabrication by welding or forming is required. Special procedures may be applicable to varying compositions and section sizes, as produced by a given supplier; therefore, the purchaser should consult with the producer in order to be aware of these variables. This SAE Recommended Practice covers three strength levels of quenched and tempered carbon-manganese, carbon-manganese-boron, and alloy steel plates for structural use.