How to classify and label bolts How to understand the strength grade of bolts

Release time:

2023-07-28

The strength grades of bolts for steel structure connection are as follows: 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, etc. more than 10 grades. The bolt strength grade label is composed of two numbers, which respectively represent the nominal tensile strength and yield ratio of the bolt material.

Bolts are mechanical connectors and are widely used in various industries, but perhaps some consumers do not know that bolts actually have the details of strength grade. The strength grade of the bolt is closely related to the use of the bolt. This article will be aroundBolt strength gradeExplain, hope to help everyone.

How to classify and label bolts

1. The nominal tensile strength of the bolt material is 400MPa;

2. The yield ratio of bolt material is 0.6;

3. The nominal yield strength of bolt material is 400 × 0.6 = 240MPa.

How to know the strength grade of bolt

The meaning of the bolt strength grade is an international standard, and the same performance grade of the bolt, regardless of its material and origin, its performance is the same. Therefore, in the design as long as the selection of the corresponding performance level can be. The strength grade of the bolt is usually expressed as numbers, such as 8.8 grade and 10.9 grade, and the numbers indicate that the shear stress resistance grade of the bolt is 8.8GPa and 10.9Gpa, respectively.

Specific meaning of 8.8 and 10.9 grade bolts

Grade 8.8 bolts have a nominal tensile strength of 800N/mm? and a nominal yield strength of 640N/mm?. The 10.9 grade bolt is after a special heat treatment to achieve the following three performance indicators:

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

2. The yield ratio of bolt material is 0.9;

3. The nominal yield strength of the bolt material reaches 900MPa.

How to calculate the strength grade of bolts

The strength grade of general bolts is usually adopted“X.Y”This way of representation. where X * 100 represents the tensile strength of the bolt and X * 100 *(Y/10) is the yield strength of the bolt, where Y represents the ratio of the yield strength to the tensile strength. For example, 4.8 grade means that the tensile strength of the bolt is 400MPa, and the yield strength is 400*8/10=320MPa.

Summary

When choosing bolts, it is particularly important to understand the strength level of bolts. Accurate judgment and calculation can help us choose and use more suitable bolts, so as to better ensure the safety and stability of our work.