Selection principle and method of flange bolt strength grade

The strength grade of flange bolts is selected according to the working pressure. If the working pressure is less than 1Mpa, you can choose grade 4.8, and if the working pressure is less than 1Mpa, you can choose grade 8.8 high-strength bolts and so on.

Flange bolt grades can be divided into 10 performance grades: 3.6, 4.6, 4.8, 5.6, 5.8, 6.8, 8.8, 9.8, 10.9, 12.9, among which the bolts of grade 8.8 and above are made of low carbon alloy steel or medium carbon steel and After heat treatment (quenching, tempering), they are commonly called high-strength bolts, and the rest are commonly called ordinary bolts.

The bolt performance grade label consists of two parts of numbers, which respectively represent the nominal tensile strength value and yield strength ratio of the bolt material. For example: bolts with performance grade 4.6, its meaning is:

1. The nominal tensile strength of the 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 reaches 400×0.6=240MPa.

The meaning of bolt performance grade is an international standard. Bolts of the same performance grade have the same performance regardless of the difference in their materials and origins. Only the performance grade can be selected for design.

Instructions for purchasing bolts

It is necessary to prevent suppliers from shoddy and prevent suppliers from quoting in small units of measurement, thereby reducing your sensitivity to prices. To analyze the supplier's proposal for pitfalls.

Strengthen testing, especially for materials whose raw material prices fluctuate greatly, suppliers often take the opportunity to raise prices. It is a wrong view that the raw materials in the supplier's quotation cannot be moved. The bolt grade can be tested by relevant instruments, and the bolt strength grade is detected by a hardness tester, a tensile machine, and an impact machine. When selecting bolts, you must first consider the types of forces the bolts are subjected to during use, the magnitude of the forces and the environment in which they are used, and then select flange bolts with appropriate specifications and grades.