强bai度等级是根据力学性能划du分的。依相关标准zhi，螺栓性能等级分3.6、dao4.6、4.8、5.6、6.8、8.8、9.8、10.9、12.9等10余个等级，其中8.8级及以上螺栓材质为低碳合金钢或中碳钢并经热处理（淬火、回火），通称为高强度螺栓，其余通称为普通螺栓。螺栓性能等级标号有两部分数字组成，分别表示螺栓材料的公称抗拉强度值和屈强比值。例如：
The degree of strong Bai is divided into Du grades according to the mechanical properties. According to relevant standards, the performance grade of bolts can be divided into more than 10 grades, such as 3.6, dao4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9 and 12.9. Among them, bolts of grade 8.8 and above are made of low-carbon alloy steel or medium carbon steel and heat-treated (quenching and tempering), which are generally called high-strength bolts, and the rest are commonly referred to as ordinary bolts. The bolt performance grade label consists of two parts, which respectively represent the nominal tensile strength and yield strength ratio of bolt material. For example:
性能等级4.6级的螺栓，其含义是：
The meaning of bolts with performance grade 4.6 is as follows:
1、螺栓材质公称抗拉强度达400MPa级；
1. The nominal tensile strength of bolt material is 400MPa;
2、螺栓材质的屈强比值为0.6；
2. The yield strength ratio of bolt material is 0.6;
3、螺栓材质的公称屈服强度达400×0.6=240MPa级
3. The nominal yield strength of bolt material is 400 × 0.6 = 240mpa
性能等级10.9级高强度螺栓，其材料经过热处理后，能达到：
After heat treatment, the material of high strength bolt with performance grade of 10.9 can reach the following requirements:
1、螺栓材质公称抗拉强度达1000MPa级；
1. The nominal tensile strength of bolt material reaches 1000MPa;
2、螺栓材质的屈强比值为0.9；
2. The yield strength ratio of bolt material is 0.9;
3、螺栓材质的公称屈服强度达1000×0.9=900MPa级
3. The nominal yield strength of bolt material is 1000 × 0.9 = 900MPa
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