Friction treatment method for high-strength bolted joints

What are the friction treatment methods for high-strength bolted joints? Let's introduce maijin. ①Sandblasting (shot) method Use compressed gas as the drive to spray sand (shot) onto the steel surface immediately, so that the steel surface can achieve a certain surface roughness, rust is removed, and the steel surface is iron gray after sandblasting (shot). ②Oxidation treatment-pickling passivation method Generally, the processed prefabricated components are soaked into the pickling equipment, stay for a period of time, and then put into the lime powder tank, neutralize and clean with cold water. ③Sand wheel grinding method For small projects or existing building reinforcement and reconstruction projects, technical methods are often used to deal with the repelling surface. Sand wheel grinding is the most intuitive and simple method. When using a grinder to grind the steel surface, the grinding direction of the grinding wheel is perpendicular to the bearing direction, and the grinding operation scale should be 4 times the bolt hole diameter. When grinding, pay attention to the fact that no obvious grinding dents appear on the surface of the steel. ④ Steel brush manual anti-rust treatment Use a steel brush to remove iron, phosphorus, rust, floating dust, oil stains and other wastes on the repelling surface, so that the steel surface will expose the metal texture, and store the original cold-rolled surface. Differences between high-strength bolts and ordinary bolts: 1. The raw materials of high-strength bolts are different from ordinary bolts. High-strength bolts are generally used for permanent butt joints. The common ones are M16~M30. Super-large standardized high-strength bolts have unstable properties and should be used calmly. 2. The bolts of the main components of the building structure are generally connected with high-strength bolts. 3. General bolts can be reused many times, but high-strength bolts are not easy to reuse. 4. High-strength bolts are generally made of high-strength steel (No. 45 steel (8.8s), 20MmTiB (10.9S), which are prestressed steel bolts. The friction type uses a torque wrench to increase the required prestressed steel bar, and the compression type unscrews the torx head. Ordinary bolts are generally made of general steel (Q235), and only need to be tightened. 5. General bolts are generally 4.4, 4.8, 5.6, 8.8 High-strength bolts are generally grade 8.8 and grade 10.9, among which grade 10.9 is the majority. 6. The screw holes of general bolts are not necessarily larger than high-strength bolts. In fact, the screw holes of general bolts are very small. 7. The screw holes of general bolts A and B are generally 0.3~0.5mm larger than bolts. C-grade screw holes are generally 1.0~1.5mm larger than bolts. .5 ~ 2.0mm. 9. The standard force transmission characteristic of pressure-bearing high-strength bolts is to ensure that under the premise of normal start-up, the shear stress shall not exceed the sliding friction force, which is the same as that of friction-type high-strength bolts. When the bearing capacity increases, the relative movement between the butt plates will occur, and the butt joints use the screw to resist bending and the hole edge to bear pressure to transmit force, which is the same as ordinary bolts. Therefore, the difference between the screw and the screw hole is slightly smaller, 1.0 to 1.5mm.