The bolts for steel structure connection are classified […]
The bolts for steel structure connection are classified into more than 10 grades of 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 heat treated. (Quenching, tempering), commonly known as high-strength bolts, the rest are commonly referred to as ordinary bolts. The bolt performance grade label is composed of two parts, which represent the nominal tensile strength value and the yield ratio of the bolt material. E.g:
Bolts with a performance class of 4.6, which means:
1. The nominal tensile strength of bolt material is up to 400MPa;
2. The yield ratio of the bolt material is 0.6;
3. The nominal yield strength of the bolt material is 400×0.6=240MPa
Performance grade 10.9 high strength bolts, after heat treatment, can achieve:
1. The nominal tensile strength of bolt material is up to 1000MPa;
2. The yield ratio of the bolt material is 0.9;
3. The nominal yield strength of the bolt material is 1000×0.9=900MPa
The meaning of the bolt performance grade is the international standard. The bolts of the same performance grade have the same performance regardless of the difference between the material and the place of origin. Only the performance grade can be selected in the design.
Strength grades The so-called 8.8 and 10.9 grades refer to bolts with shear stress ratings of 8.8 GPa and 10.9 GPa.