High-strength bolted connections rely on the friction between the contact surfaces of the connectors to prevent them from sliding each other. In order to make the contact surfaces have sufficient friction, it is necessary to increase the clamping force of the components and increase the friction coefficient of the contact surfaces of the components. The clamping force between components is achieved by applying pretension to the bolts, so the bolts must be made of high-strength steel, which is why it is called high-strength bolt connection.
  In high-strength bolted connections, the friction coefficient has a great influence on the bearing capacity. The test shows that the friction coefficient is mainly affected by the form of the contact surface and the material of the component. In order to increase the friction coefficient of the contact surface, methods such as sandblasting and cleaning with a wire brush are often used to treat the contact surface of the components within the connection range during construction. What about the high-strength bolt material?
1. The maximum tensile strength of the material used for high-strength bolts has a lot to do with quenching treatment. After 40Cr quenching treatment, it is generally difficult to meet the material requirements of 10.9S high-strength bolts. The surface hardness is used to judge the maximum tensile strength of the material. In addition to the different properties in the processing process, the delayed fracture properties of high-strength bolts with different materials are also different under high stress conditions.