The difference between high-strength bolts and ordinary bolts

The difference between high-strength bolts and ordinary bolts

From the perspective of raw materials:

High strength bolts are made of high-strength materials. The screws, nuts, and washers of high-strength bolts are all made of high-strength steel, commonly used in 45 # steel, 40 boron steel, and 20 manganese titanium boron steel. Ordinary bolts are commonly made of Q235 steel.

From the perspective of strength level:

High strength bolts are increasingly widely used. Two strength levels, 8.8s and 10.9s, are commonly used, with 10.9 being the most common. Ordinary bolt strength

The degree level should be low, generally 4.4, 4.8, 5.6, and 8.8.

From the perspective of force characteristics:

High strength bolts apply pre tension and transmit external forces through friction. Ordinary bolt connections rely on the shear resistance of the bolt rod and the bearing pressure of the hole wall to transmit shear

When tightening the nut, the pre tension force generated is very small, and its impact can be ignored, while high-strength bolts have high material strength

In addition, a large pre tension force is also applied to the bolts, causing squeezing force between the connecting components, resulting in significant friction perpendicular to the screw direction

Friction force, as well as pre tension, anti slip coefficient, and steel type, all directly affect the bearing capacity of high-strength bolts.

According to the stress characteristics, it can be divided into pressure bearing type and friction type. The calculation methods for the two are different. Minimum specification M12 for high-strength bolts, commonly used

M16~M30, oversized bolts have unstable performance and should be used with caution in design.