PEM Bolt Manufacturers

What anti-loosening technologies can ensure the tightening effect of bolts?

Anti-loosening technologies to ensure bolt tightening effects mainly include the following, especially in vibration environments:

Mechanical locking and anti-loosening: The anti-loosening effect is achieved by using mechanical components such as stop washers, cotter pins, and series wires to prevent relative rotation between bolts and nuts.
Friction and anti-loosening: Use increased friction between contact surfaces to prevent loosening. This can be achieved by using washers with special textures or materials (such as spring washers, serrated washers) or by applying locking glue to the contact surface.
Non-detachable anti-loosening: The thread pair is fixed by welding, riveting or bonding. Although this will sacrifice the detachability of the bolt, it is very effective in situations where repeated disassembly is not required.
Pre-tightening force locking and anti-loosening: Apply sufficient pre-tightening force to ensure the stability of the connection, and at the same time cooperate with appropriate tightening technology, such as the torque method or the torque-angle method, to improve the consistency and reliability of tightening.
Self-locking bolts: Specially designed bolt structures, such as integrated self-locking double nuts, can produce additional anti-loosening effects when tightening.
Chemical glue to prevent loosening: Use special locking glue or anaerobic glue. These glues will harden under specific conditions (such as isolation of air and metal contact) to fix bolts and nuts.
MEC processing: A special processing technology that processes a mixture of micro-capsules containing adhesives at the bolt site. When the bolt is tightened, the capsule ruptures and the locking agent polymerizes to provide additional anti-loosening effect.
Lateral vibration test: Conduct a vibration test on the bolt connection system to verify the effectiveness of different anti-loosening measures, and select the best anti-loosening technology based on the test results.

Each anti-loosening technology has its specific application scenarios, advantages and disadvantages, and which technology to choose depends on the specific requirements of the bolted connection, the cost budget, and the feasibility of maintenance. In practical applications, it may be necessary to combine multiple anti-loosening technologies to achieve the best fastening effect.

How are the strength grades of bolts divided?

Bolts are important fasteners for connecting various mechanical components, and the classification of their strength levels is crucial to ensuring the safety and reliability of the mechanical structure. The strength grade of bolts is usually determined based on the tensile strength and yield strength of its material and follows international standards.

Bolt strength grade identification
The strength grade of a bolt usually consists of two numbers, such as 4.6, 8.8, 10.9, etc. These numbers represent the specific properties of the bolt material:

The first number: indicates the nominal tensile strength of the bolt material, in MPa (MPa), which is 1/100 of the tensile strength limit. For example, the nominal tensile strength of a grade 8.8 bolt is 880 MPa.

The number after the decimal point: indicates the yield strength ratio of the bolt material, which is 10 times the ratio of the yield limit to the tensile strength limit. For example, a grade 8.8 bolt has a yield ratio of 0.8, meaning its nominal yield strength is 80% of 880 MPa, or 704 MPa.

Selection of bolt strength grade
The strength grade of the bolt needs to be selected based on the required load-bearing capacity and design requirements of the connected components. High-strength bolts (such as grade 8.8 and above) are usually made of low-carbon alloy steel or medium-carbon steel and are heat treated to improve their mechanical properties. In contrast, ordinary bolts (such as grade 4.6, grade 5.6) are usually made of carbon steel and do not require heat treatment.

Application of bolt strength grade
Different application scenarios have different strength requirements for bolts. For example:

Automotive Industry: High-strength bolts are widely used as they need to withstand high loads and impact loads.
Building structures: High-strength bolts are also used, especially where dynamic loads are required or where anti-loosening is required.
Ordinary Mechanical Connections: Ordinary bolts may be used as they are less expensive and sufficient to handle the lower load requirements.
International standard for bolt strength grades
The strength grade of bolts follows international standards, such as ISO (International Organization for Standardization) and DIN (German Industrial Standards), as well as national standards of various countries, such as ASTM in the United States, GB in China, etc. These standards ensure consistent performance among bolts of the same grade produced by different manufacturers.

The strength grade of bolts is a key parameter in bolt design and selection, which is directly related to the reliability and safety of bolt connections. Knowing the strength grade of a bolt helps engineers and technicians make good decisions during the design and manufacturing process. With the development of technology, improvements in bolt materials and manufacturing processes will further enhance the performance of bolts and meet more stringent industrial requirements.