Classification of screw grades

The classification of screw grades is:

1、 The bolt performance level, which refers to the performance level of bolts used for steel structure connections, is divided into more than 10 levels such as 3.6, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9, 12.9, etc. 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 with grade 8.8 and above are made of low-carbon alloy steel or medium carbon steel and undergo heat treatment (quenching, tempering), collectively referred to as high-strength bolts, and the rest are collectively referred to as ordinary bolts. The bolt performance grade number consists of two parts of numbers, which respectively represent the nominal tensile strength value and yield strength ratio of the bolt material.

2、 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 with grade 8.8 and above are made of low-carbon alloy steel or medium carbon steel and undergo heat treatment (quenching, tempering), commonly known as high-strength bolts, while others are commonly known as ordinary bolts. The bolt performance grade number consists of two parts of numbers, which respectively represent the nominal tensile strength value and yield strength ratio of the bolt material. For example, a bolt with a performance level of 4.6 means:

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

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

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

High strength bolts with a performance level of 10.9, made of materials that have undergone heat treatment, can achieve:

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

2. The yield strength ratio of bolt material is 0.9;

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