How Are Bolts Classified And Labeled? How To Understand The Strength Level Of Bolts?

 Bolts are mechanical connectors that are widely used in various industries, but some consumers may not be aware of the fact that bolts actually have strength levels. The strength level of bolts is closely related to their use. This article will focus on explaining the strength level of bolts, hoping to be helpful to everyone.

How to classify and label bolts

The strength levels of bolts used for steel structure connections are as follows: 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, and more than 10 levels. The bolt strength grade label is composed of two numbers, representing the nominal tensile strength and yield ratio of the bolt material. For example, bolts of grade 4.6 represent:

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

2. The yield strength ratio of bolt material is 0.6;

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

How to understand the strength level of bolts

The meaning of bolt strength grade is an internationally recognized standard, and bolts with the same performance grade have the same performance regardless of their material and origin. Therefore, in the design, only the corresponding performance level can be selected. The strength level of bolts is usually expressed in numbers, such as 8.8 and 10.9, where numbers indicate that the shear stress levels of bolts are 8.8 GPa and 10.9 Gpa, respectively.

The specific meaning of grade 8.8 and 10.9 bolts

The nominal tensile strength of Grade 8.8 bolts is 800N/mm?, The nominal yield strength is 640N/mm?. Grade 10.9 bolts, on the other hand, require specialized heat treatment to achieve the following three performance indicators:

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

2. The yield strength ratio of bolt material is 0.9;

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

How to calculate the strength grade of bolts

The strength grade of general bolts is usually represented by "X.Y". Among them, X * 100 represents the tensile strength of this bolt, while X * 100 * (Y/10) is the yield strength of this bolt, where Y represents the ratio of yield strength to tensile strength. For example, level 4.8 indicates that the tensile strength of the bolt is 400MPa, while the yield strength is 400 * 8/10=320MPa.

summary

It is particularly important to understand the strength level of bolts when selecting them. Accurate judgment and calculation can help us choose and use more suitable bolts, thereby better ensuring our safety and stability in work.