Screw grade classification

The screw grade classification is:

1. Bolt performance grade, that is, bolt performance grade for steel structure connection, 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, 12.9, etc. 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. Among them, the bolts of grade 8.8 and above are made of 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 consists of two parts of numbers, which represent the nominal tensile strength value and yield ratio of the bolt material respectively.

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. Among them, 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 bolts, and the rest are generally called ordinary bolts. The bolt performance grade label consists of two parts of numbers, which represent the nominal tensile strength value and yield ratio of the bolt material respectively. For example: bolts of performance class 4.6, which means:

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 is 400×0.6=240MPa

The performance level 10.9 high-strength bolts, after heat treatment, can reach:

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

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

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