Bolt

A bolt is a type of fastener consisting of a head and a screw (a cylinder with external threads). It should be used in conjunction with a nut to fasten two parts with a through hole. It is an anchorage assembly that anchors the connecting piece to a hardened concrete substrate.

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 bolts of performance class 4.6, the meaning is:

1. Bolt material nominal tensile strength of 400MPa;

2. The strength ratio of bolt material is 0.6;

3. 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:

1. The nominal tensile strength of bolt material reaches 1000MPa;

2. The 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 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

General bolts are used "X.Y" to indicate strength,

X*100= tensile strength of the bolt,

X*100* (Y/10) = yield strength of the bolt

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

If grade 4.8, then this bolt:

Tensile strength: 400MPa

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