High Strength Bolt
High-strength bolt is a high-strength bolt, which belongs to a standard part. Generally speaking, high strength bolts can bear more loads than ordinary bolts of the same specification.
The working principle of high-strength bolt connection is intentionally to exert a large pre-tension force on the bolt, which causes the extrusion force between the contact surfaces of the joints, so there is a great friction perpendicular to the direction of the screw, relying on this friction force to transfer the connection shear. The pre-tension force of high-strength bolts is achieved by tightening the nuts. The common high-strength bolts generally adopt the methods of torque and rotation. The Torsion-shear type high strength bolt adopts the Torsion-shear bolt tail to control the pre-tension force.
High strength bolt is made of high quality alloy structural steel of 10.9S or 8.8S grade,and it has been heat treated,and its hole is drilled,which of friction diameter is 1.5-2.0 mm larger than the nominal diameter of the bolt,of pressure connection diameter is larger than the nominal diameter of the bolt 1 ~ 1.5mm.
High strength bolts are mainly used in steel structure engineering. One of the most important characteristics of high strength bolts is that they are limited to single use. They are generally used for permanent connections. It is strictly prohibited to reuse them.
According to the state of force, it can be divided into friction type and pressure type.
In fact, there are differences in design and calculation methods. The ultimate state of bearing capacity of friction type is the sliding between plates,which for pressure type is connection failure. Friction type high strength bolts can not fully develop the potential of bolts. In practical application, friction high strength bolts should be used for very important structures or structures that bears dynamic loads.especially when the reverse stress is caused by loads. At this time, the untapped bolt potential can be used as a safety reserve.In addition, high-strength bolted connections of bearing type should be adopted to reduce the cost.
According to the construction technology, it can be divided into torsional shear high strength bolts and hexagonal high strength bolts.
The big hexagonal high strength bolt belongs to the high strength grade of ordinary bolt, while the torsional shear high strength bolt is the improved type of the big hexagonal high strength bolt, in order to better construction.
The construction of high-strength bolts must first be screwed before final screwing, and the initial screwing of high-strength bolts needs impact type electric wrench or torque adjustable electric wrench; while the final screwing of high-strength bolts has strict requirements, the final screwing of high-strength bolts must use torsional shear type electric wrench, and the final screwing of high-strength bolts must use torsional type electric wrench.
The wire used for high strength bolt is 45 steel and so on. Which has been heat treated on C1035. This hardening treatment method can generally achieve 22-32HRC high strength.