The difference between high-strength bolts and ordinary bolts

Today I will tell you the difference between high-strength bolts and ordinary bolts.

Bolts: Ordinary bolts are divided into three types: A, B, and c. The first two are precision bolts, which are less used. -General purpose bolts refer to C type general purpose bolts. These kinds of products have good development space in Qingdao bolt market. For some temporary connections and disassembly connections, use C-level general-purpose bolts. Commonly used bolts are M16, M20, and M24. In some machinery industries, thick bolts may have larger diameters and special applications. High-strength bolts: The material of high-strength bolts is different from ordinary bolts. High-strength bolts-used for permanent connections. Commonly used are M16-m30. The performance of super-large high-strength bolts is unstable and should be used with caution. The main components of the building structure are generally connected by high-strength bolts. There is no difference between the pressure type and the friction type of the high-strength bolts provided by the factory. In fact, the design calculation method is different:

(1) Friction type high-strength bolts take the sliding between plates as the ultimate bearing capacity.

(2) The normal service limit state of the pressure-type high-strength bolt is the sliding between the plates, and the connection failure is the bearing capacity limit state. Friction-type high-strength bolts cannot fully exploit the potential of bolts. In practical applications, for very important structures or structures under dynamic loads, especially when the load causes reverse stress, friction-type high-strength bolts should be used. At this time, the unrealized bolt potential can be used as a safety reserve. In addition, pressure-type high-strength bolts should be used for placement to reduce costs.

The difference between ordinary bolts and high-strength bolts

Ordinary bolts can be reused, but high-strength bolts cannot be reused.

High-strength bolts-made of high-strength steel. 45 steel (8.8s), 20MmTiB (10.9s), is a kind of prestressed bolt, friction type uses torque wrench to apply the specified prestress, pressure type unloading head. Ordinary bolt-Ordinary steel (Q235), just tighten it. Ordinary bolts-there are generally 4.4, 4.8, 5.6 and 8.8 grades. High-strength bolts are generally 8.8 and 10.9, mainly 10.9.

The screw holes of the West Pass bolts are not necessarily larger than the screw holes of high-strength bolts. In fact, ordinary bolts have smaller holes.

Type A and Type B screw holes-generally 0.3~0.5mm larger than bolts. Type C screw holes-generally 1.0~1.5mm larger than bolts.

Friction-type high-strength bolts transmit load through friction, so the difference between the screw and the screw hole can reach 1.5-2.0mm.

The load transfer characteristics of pressure-type high-strength bolts are to ensure that the shear force does not exceed the friction force during normal use, which is the same as friction-type high-strength bolts. When the load increases again, relative slippage occurs between the connecting plates. The connection depends on the shear of the screw and the pressure of the hole wall to transmit the force, which is the same as the ordinary bolt. Therefore, the difference between the screw and the screw hole is slightly smaller, between 1.0 ~ 1.5 mm.