threaded studs Raw materials
How much of a high strength bolt can withstand
Just how helpful the withstanding capability of the high strength bolts are made of high strength steel, or need to larger bolt pre-tightening force, can be referred to as the high strength bolts. High strength bolts used in Bridges and rail links, high pressure and ultrahigh pressure equipment. The bolt fracture to brittle fracture. High strength bolts used in superhigh pressure equipment, to ensure that the container seal, need to bigger prestress on concept of high strength bolts (1) according to regulations of bolt performance level in 8.8 above, known as the high strength bolts. Now the national standard listed only to M39, for big size, especially the length of 10 ~ 15 times greater than % of high strength bolt, domestic production is short of high strength hex bolt type high strength T bolt
The high strength bolt is different from the normal bolt
High strength bolts are acceptable loads that are larger than normal bolts of the same specification. The material of the normal bolt is Q235 (that is, A3). High strength bolts of material 35 # steel or other high quality materials are made for heat treatment and increased strength. The difference between the two is the strength of the material.
From raw materials: high strength bolts are made of high strength materials. The bolt, nut and gasket of high strength bolts are made of high strength steel, and are commonly used in 45 steel, 40 boron steel, 20 mn titanium boron steel and 35CrMoA. Normal bolts are usually made of Q235 (the equivalent of A3). Strength level: high - strength bolts are used more and more widely. There are two levels of strength: 8.8 s and 10.9 s. Normal bolt strength level is low, generally 4.4, 4.8, 5.6 and 8.8.
In terms of force characteristics, the high strength bolt exerts the pretension and the force of friction. Ordinary bolt connection by shearing bolt rod and the pressure on the hole wall shear, tighten the nut when pulling force is small, its influence can be neglected, and high strength bolts, besides its material strength is very high to the bolt exerted a lot of tension, make connections between components to produce extrusion pressure, so that the perpendicular to the direction of the screw much friction, and strong, resistance to sliding coefficient and steel types are directly affect the bearing capacity of high strength bolt. According to the stress characteristics of the pressure type and friction type, the calculation method is different. High strength bolt minimum specification M12, commonly M16 ~ M30, super-size bolt performance is not stable, should be used carefully in design. High strength bolt type friction and pressure connection: the difference between the high strength bolt connection is through the great tighten pretension bolt rod inside the connection plate plate clamp, enough to produce a lot of friction, so as to improve the integrity and stiffness of connection, when the shear, in accordance with the requirements for the design and stress is different, can be divided into friction type high strength bolt connection and high strength bolt connecting two pressure type, is the essential difference between the two limit state is different, although it is the same kind of bolt, but in the calculation method, requirements, scope of application is very different. In shear design, outside shear friction type high strength bolt connection is reached the interface between the plate parts provided by the bolt tightening force may be the biggest friction as a limit state, namely is to ensure that connection in the internal and external shear force does not exceed the maximum friction force during use. The slabs do not occur relative slip deformation (the amount of void between the screw and the hole wall is always maintained), and the joint plate is subjected to the overall elastic force. In shear design, pressure type high strength bolt connection is allowed in the external shear force exceeds the maximum friction force, the relative sliding between the connected plate deformation, until the bolt contact with the hole wall, then connection on bolt shaft shear and pressure on the hole wall and the friction between the contact surface panel joint force, finally to shaft shear or pressure on the hole wall damage as even accept shear limit state. In summary, the high strength bolts of the friction type and the pressure type high strength bolts are actually the same bolts, but are designed to consider slippage. The friction type high-strength bolt can not slide, the bolt can not bear the shear force, once slip, the design is considered to achieve the failure state, in the technology is relatively mature; The pressure-bearing high-strength bolt can slide, the bolt also takes the shear force, and the ultimate failure is the equivalent of the normal bolt damage (the bolt or the steel plate is crushed).