There are more than 10 grades of bolts for steel structure connection, 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 8.8 grade and above are made of low-carbon alloy steel or medium carbon steel and treated with heat treatment (quenching, tempering), which are called high strength bolts, and the rest are called ordinary bolts. The bolt performance grade label consists of two parts, which represent the nominal tensile strength value and the ratio of buckling strength of the bolt material respectively. For example, a bolt of performance class 4.6 means:
1. Nominal tensile strength of bolt material reaches 400MPa;
2. The compressive strength ratio of bolt material is 0.6;
3. The nominal yield strength of the bolt material is up to 400×0.6=240MPa grade 10.9 high strength bolt. After heat treatment, the material can reach:
1. Nominal tensile strength of bolt material reaches 1000MPa;
2. The compressive strength ratio of bolt material is 0.9;
3, the nominal yield strength of bolt material is 1000×0.9=900MPa
The meaning of bolt performance grade is international and general standard, the bolt of same performance grade, no matter its material and the distinction of producing area, its performance is identical, choose performance grade only on the design can. Strength grades 8.8 and 10.9 refer to the shear stress grades of bolts 8.8GPa and 10.9Gpa8.8 nominal tensile strength 800N/MM2 nominal yield strength 640N/MM2
A normal bolt is denoted by "X.Y",
X*100= the tensile strength of the 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 on the Richter scale
Then the bolt
Tensile strength: 400MPa
Yield strength: 400*8/10=320MPa
