Strength of high-strength bolts
Strength of high-strength bolts
High strength bolts are mainly used to connect steel plates in steel Structural engineering. High strength bolts are divided into torsional shear type high strength bolts and large hexagonal high strength bolts. The large hexagonal high-strength bolt belongs to the high-strength grade of ordinary bolts, while the torsion shear type high-strength bolt is an improved version of the large hexagonal high-strength bolt, which has a better structure. The structure of the high-strength bolt must be tightened first, and then tightened. The initial tightening of high-strength bolts requires the use of an impact type electric wrench or a torque adjustable electric wrench. However, there are strict requirements for the final tightening of high-strength bolts. Torque type electric wrenches must be used for the final tightening of high-strength bolts, and torque type electric wrenches must be used for the final tightening of high-strength bolts.
Why are high-strength bolts called high-strength? Is it because it is earthquake resistant? In fact, the reason why high-strength screws are called high-strength bolts is because they are made of different materials. The material of high-strength screws is made of high-strength steel or bolts that require greater preload. High strength screws use a specialized wrench to tighten the nut in order to generate a controllable and huge pre tightening force on the bolt. Generate the same preload on the connected parts through nuts and substrates. High strength screws are mainly used for connecting bridges, railway tracks, high-voltage and ultra-high-voltage equipment. According to the specified performance level of bolts above grade 8.8, they are called high-strength bolts. Currently, the national standard only lists M39. For large-sized specifications, especially high-strength bolts with a length greater than 10-15%, domestic production is still very short. In terms of strength level, high-strength screws are widely used. The commonly used strength levels are 8.8s and 10.9s, with the highest strength level being 10.9. The strength grade of ordinary bolts is relatively low, usually 4.4, 4.8, 5.6, and 8.8.
From the perspective of stress characteristics, high-strength bolts apply pre-stress and transmit external forces through friction. The shear force of ordinary bolt connections is transmitted through the shear resistance of the bolt rod and the pressure on the hole wall. The pre tightening force generated when tightening the nut is very small, and its impact can be ignored. In addition to the high material strength of high-strength bolts, a significant amount of pre-stress is also applied to the bolts, resulting in compressive pressure between the connecting components and a significant amount of friction in the direction perpendicular to the screw direction. Additionally, the preload force, slip resistance coefficient, and various materials of steel directly affect the load-bearing capacity of high-strength bolts. According to stress characteristics, it can be divided into pressure bearing type and friction type. The minimum specification for high-strength bolts is M12, usually using M16-M30. The performance of oversized bolts is unstable, so they should be used with caution in design.
The company's main products include high-strength bolts, high-strength nuts, steel structural bolts, steel structural nuts, grid sealing plates, grid bolts, etc.
