The difference between high strength bolts and ordinary bolts

Updated:06-12-2019
Summary:

High-strength bolts are bolts with a performance level […]

High-strength bolts are bolts with a performance level of 8.8 or higher. The general material of high-strength bolts is 35 # steel or other high-quality materials. After processing and manufacturing, heat treatment is performed to increase the strength of the bolts to achieve high-strength bolts standard.
What is the difference between high strength bolts and ordinary bolts?

Intensity
The load of high-strength bolts is much stronger than ordinary bolts, and the performance is also high.

Material
The rods, nuts and washers of high-strength bolts are made of high-strength steel. 45 # steel, 40B steel, 20MnTiB steel, 35CrMoA, etc. are commonly used. Ordinary bolts are usually made of Q235 steel.

Forced
High-strength bolts exert pretension and transmit external forces by friction; ordinary bolted connections rely on shear strength of the bolts and pressure on the hole wall to transmit shear forces.

Use level:
High-strength bolts are commonly graded at 8.8 and 10.9; ordinary bolts are generally graded at 4.4, 4.8, and 5.6.

usage count
High-strength bolts are generally not reusable; ordinary bolts can be reused.
Advantages of high-strength bolts: simple connection construction, good mechanical performance, detachability, fatigue resistance, and no loosening under dynamic loads.

Daily notes for high-strength bolts:
1. Do not hammer into the bolt during installation to prevent damage to the bolt thread.
2. The electric wrench that is regularly tested during use to ensure the accuracy of the torque and operate in the correct tightening sequence.
3. The surface rust, oil stains, burrs on the wall of the bolt holes, and welding knobs should be cleaned up.
4. After contacting the friction surface, the required anti-scratch coefficient must be met. The high-strength bolts used should have matching nuts and washers. When used, they should be used in accordance with the matching and must not be interchanged.
5. When handling the friction surface of the component, oil, dirt, and other sundries are not allowed during installation.
6. The friction surface of the component should be kept dry during installation and should not be operated in the rain.
7. Strictly check and correct the deformation of the connected steel plates before installation.

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