Bolt Performance Level

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), commonly known as high-strength bolts, the rest are commonly known 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. E.g:

The bolt of performance grade 4.6 has the following meanings:

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

2. The yield ratio of 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, 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

The meaning of bolt performance level is an international standard. Regardless of the difference in material and place of origin, the performance of bolts of the same performance level is the same. Only the performance level can be used for design.

The so-called strength grades of 8.8 and 10.9 refer to the bolts' shear stress levels of 8.8GPa and 10.9GPa

8.8 Nominal tensile strength 800N / MM2 Nominal yield strength 640N / MM2

The general bolts use "X.Y" to indicate strength,

X * 100 = tensile strength of this bolt,

X * 100 * （Y / 10） = Yield strength of this bolt

(Because according to the label: yield strength / tensile strength = Y / 10)

Such as 4.8

Then this bolt

Tensile strength: 400MPa

The yield strength is: 400 * 8/10 = 320MPa