Screw grade classification

1. The bolt performance level, that is, the bolt performance level for steel structure connection, is divided into more than 10 grades such as 3.6, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9, and 12.9. The performance grades of bolts for steel structure connection are divided into more than 10 grades such as 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, etc., of which the bolts of grade 8.8 and above are low carbon alloy steel or medium carbon steel and are heat treated (Quenching, tempering), collectively referred to as high-strength bolts, the rest are collectively referred to as ordinary bolts. The bolt performance grade label is composed of two parts of numbers, which respectively represent the nominal tensile strength value and yield ratio of the bolt material.

2. The performance grades of bolts for steel structure connection are divided into more than 10 grades, such as 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, etc., and the bolts of grade 8.8 and above are made of low carbon alloy steel or medium carbon steel After heat treatment (quenching, tempering), it is generally called high-strength bolt, and the rest are generally called ordinary bolts. The bolt performance grade label is composed of two parts of numbers, which respectively represent the nominal tensile strength value and yield ratio of the bolt material. For example: bolts of performance class 4.6, the meaning is:

1. The nominal tensile strength of the bolt material reaches 400MPa;

2. The yield strength ratio of the bolt material is 0.6;

3. The nominal yield strength of the bolt material reaches 400 × 0.6 = 240MPa

Performance grade 10.9 high-strength bolts, after heat treatment of the material, can achieve:

1. The nominal tensile strength of the bolt material reaches 1000MPa;

2. The yield ratio of bolt material is 0.9;

3. The nominal yield strength of the bolt material reaches 1000 × 0.9 = 900MPa.