Do you know the difference between High Strength Bolt and ordinary bolts?

As a Railway Fastening System Manufacturer, share it with everyone. Today, advanced manufacturing represented by aircraft, large power generation equipment, automobiles, high-speed trains, large ships, and large complete sets of equipment has entered an important development direction. As a result, the Fastening System will enter an important stage of development. High-strength bolts are used for the connection of important machinery. Repeated disassembly or various installation torque methods require high-strength bolts. Therefore, the surface condition and the accuracy of the thread will directly affect the life and safety of the host. In order to improve the coefficient of friction and avoid rust, bite or jam during use, the technical requirements stipulate that the surface should be nickel-phosphorus plated. The thickness of the coating is guaranteed within the range of 0.02 to 0.03mm, and the coating is uniform, dense, and free of pinholes.
Railway Fastening System
Bolts made of high-strength steel, or requiring greater pre-tensioning, can be called high-strength bolts. High-strength bolts are mostly used for bridges, rails, high-voltage and ultra-high-voltage equipment connections. The fracture of this bolt is mostly brittle fracture. For high-strength bolts used in ultra-high pressure equipment, in order to ensure the sealing of the container, a large prestress needs to be applied.
Several concepts about high-strength bolts 1. According to the specified performance level of bolts above 8.8, they are called high-strength bolts. The current national standard only lists M39. For large size specifications, especially those with a length greater than 10-15 times Domestic production of high-strength bolts is still short-term.
The difference between high strength bolts and ordinary bolts:
High-strength bolts can withstand larger loads than ordinary bolts of the same specification.
The material of ordinary bolts is made of Q235 (A3).
The material of high-strength bolt 35 # steel or other high-quality materials is heat treated after being made to improve the strength.
The difference between the two is the difference in material strength.
From the raw materials:
High-strength bolts are made of high-strength materials. The screws, nuts and washers of high-strength bolts are made of high-strength steel. Commonly used are 45 # steel, 40B steel, 20MnTiB steel, 35CrMoA, etc. Ordinary bolts are usually made of Q235 (equivalent to the previous A3) steel.
From the strength level: high-strength bolts are increasingly used. Two intensity levels of 8.8s and 10.9s are commonly used, with 10.9 being the most common. The strength level of ordinary bolts should be low, generally 4.4, 4.8, 5.6 and 8.8.
From the perspective of the stress characteristics: high-strength bolts apply pretension and transmit external forces by friction. Ordinary bolt connections rely on the shear strength of the bolt and the bearing wall pressure to transmit the shear force. The preload generated when tightening the nut is very small, and its impact is negligible. In addition to the high strength of the material, high-strength bolts also exert a lot of force on the bolt The prestressing force causes a squeezing force between the connecting members, so that there is a large friction force perpendicular to the screw direction, and the preloading force, the anti-slip coefficient and the type of steel all directly affect the bearing capacity of the high-strength bolt.
There are pressure-bearing and friction-bearing types according to the characteristics of the force. The two calculation methods are different. The minimum specification of high-strength bolts is M12, and M16 ~ M30 are commonly used. The performance of oversized bolts is unstable, and should be used with caution in design.
Our company also has Railway Fastening System on sale, welcome to consult.

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