The performance grade of bolts used for steel structure connection is 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9 and so on. Bolts of grade 8.8 and above are made of low carbon alloy steel or medium carbon steel and heat-treated (quenched, tempered), which are generally called high strength bolts and the rest are generally called ordinary bolts. The bolt performance grade label is composed of two parts, which respectively represent the nominal tensile strength value and the buckling ratio of the bolt material.
For example, a bolt of performance class 4.6 means:
The nominal tensile strength of bolt material is up to 400MPa; The strength ratio of bolt material is 0.6; The nominal yield strength of bolt material is 400×0.6=240MPa. Performance grade 10.9 high strength bolt, its material after heat treatment, can reach: the nominal tensile strength of bolt material up to 1000MPa; The strength ratio of bolt material is 0.9; The nominal yield strength of bolt material is 1000×0.9=900MPa. The meaning of bolt performance grade is an international standard. Bolts of the same performance grade, regardless of the difference between their materials and origin, have the same performance, and only the performance grade can be selected in the design.
Strength grades 8.8 and 10.9 refer to the shear stress resistance grades of the bolts 8.8GPa and 10.9GPa.
8.8 Nominal tensile strength 800N/MM2; Nominal yield strength 640N/MM2.
Generally, "X.Y" is used to represent the strength of the bolt,X*100= the tensile strength of the bolt,X*100*(Y/10)= the yield strength of the bolt (because according to the label: yield strength/tensile strength =Y/10)
Such as :4.8, then the tensile strength of the bolt is :400MPa; The yield strength is 400*8/10=320MPa.
In addition: stainless steel bolts are usually labeled as A4-70,A2-70, the meaning of another interpretation.
