Performance level of hexagonal bolts

The performance grades of bolts used for steel structure connections are divided into more than 10 grades, including 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, etc. Among them, bolts of grade 8.8 and above are made of low-carbon alloy steel or medium carbon steel and heat treated (quenched and tempered), commonly referred to as high-strength bolts, while others are commonly referred to as ordinary bolts. The bolt performance grade label consists of two parts of numbers, representing the nominal tensile strength value and yield strength ratio of the bolt material. For example:
The meaning of bolts with a performance level of 4.6 is:
1. The nominal tensile strength of bolt material reaches 400MPa level;
2. The yield strength ratio of bolt material is 0.6;
3. The nominal yield strength of bolt material reaches 400 × 0.6=240MPa level
Performance grade 10.9 high-strength bolts, after heat treatment, can achieve:
1. The nominal tensile strength of bolt material reaches 1000MPa level;
2. The yield strength ratio of bolt material is 0.9;
3. The nominal yield strength of bolt material reaches 1000 × 0.9=900MPa level
The meaning of bolt performance grade is an internationally recognized standard. Bolts with the same performance grade, regardless of their material and origin, have the same performance, and only the performance grade can be selected for design.
The strength levels of 8.8 and 10.9 refer to the shear stress levels of 8.8 GPa and 10.9 GPa for bolts