強bai度等級是根據(jù)力學性能劃du分的。依相關標準zhi，螺栓性能等級分3.6、dao4.6、4.8、5.6、6.8、8.8、9.8、10.9、12.9等10余個等級，其中8.8級及以上螺栓材質為低碳合金鋼或中碳鋼并經(jīng)熱處理（淬火、回火），通稱為高強度螺栓，其余通稱為普通螺栓。螺栓性能等級標號有兩部分數(shù)字組成，分別表示螺栓材料的公稱抗拉強度值和屈強比值。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:
性能等級4.6級的螺栓，其含義是：
The meaning of bolts with performance grade 4.6 is as follows:
1、螺栓材質公稱抗拉強度達400MPa級；
1. The nominal tensile strength of bolt material is 400MPa;
2、螺栓材質的屈強比值為0.6；
2. The yield strength ratio of bolt material is 0.6;
3、螺栓材質的公稱屈服強度達400×0.6=240MPa級
3. The nominal yield strength of bolt material is 400 × 0.6 = 240mpa
性能等級10.9級高強度螺栓，其材料經(jīng)過熱處理后，能達到：
After heat treatment, the material of high strength bolt with performance grade of 10.9 can reach the following requirements:
1、螺栓材質公稱抗拉強度達1000MPa級；
1. The nominal tensile strength of bolt material reaches 1000MPa;
2、螺栓材質的屈強比值為0.9；
2. The yield strength ratio of bolt material is 0.9;
3、螺栓材質的公稱屈服強度達1000×0.9=900MPa級
3. The nominal yield strength of bolt material is 1000 × 0.9 = 900MPa
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