According to relevant standards, bolt performance grade is 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9 and other 10 grades, among which 8.8 grade and above bolts are made of low carbon alloy steel or medium carbon steel and have been heat treated (quenching, tempering), generally known as high strength bolts, the rest commonly known as ordinary bolts. The bolt performance grade label consists of two parts, respectively representing the nominal tensile strength value and flexure ratio of the bolt material. For example:
Bolts of performance class 4.6 are defined as:
1, bolt material nominal tensile strength of 400MPa;
2. The bending ratio of bolt material is 0.6;
3, the nominal yield strength of bolt material up to 400×0.6=240MPa
Performance class 10.9 high strength bolt, the material after heat treatment, can reach:
1. Nominal tensile strength of bolt material reaches 1000MPa;
2. The bending ratio of bolt material is 0.9;
3, the nominal yield strength of bolt material up to 1000×0.9=900MPa
The meaning of bolt performance grade is the international standard, the same performance grade of bolts, regardless of the difference in material and origin, its performance is the same, the design can only choose the performance grade.
Strength grades 8.8 and 10.9 refer to shear stress grades 8.8GPa and 10.9GPa for bolts
8.8 Nominal tensile strength 800N/MM2 Nominal yield strength 640N/MM2
Normal bolts are "X.Y" for strength,
X*100= the tensile strength of this bolt,
X*100*(Y/10)= Yield strength of this bolt [1]
(Because according to the label: yield strength/tensile strength =Y/10)
For example, level 4.8
Then of the bolt
The tensile strength is 400MPa
The yield strength is 400*8/10=320MP
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