螺栓等级（Bolt grade）.doc

螺栓等级（Bolt grade） High strength bolts are called high strength bolts in production. They are generally not called high-strength bolts. According to the installation features are divided into: big six angle bolts and torsion scissors type bolts. The twist shear type is only used in the 10.9 stage. According to the performance grades of high strength bolts, they are divided into 8.8 grades and 10.9 grades. 8.8 only six large angle type high strength bolt which, in the sign before the decimal point method, a digital representation of tensile strength after heat treatment; the number after the decimal point indicates that the yield ratio of the measured value of yield strength and ultimate tensile strength ratio of the measured value. The 8.8 level means that the tensile strength of the bolt bar is not less than 800MPa, the bending strength ratio is 0.8; the 10.9 stage means that the tensile strength of the bolt rod is not less than 1000MPa, and the strength ratio is 0.9. Structural design, high strength bolts generally have M16/M20/M22/M24/M27/M30 diameter, but M22/M27 is second, select series, under normal circumstances, the use of M16/M20 /M24/M30 based. According to the design requirements, high strength bolts are divided into high strength bolts, pressure bearing type and high strength bolt friction type. Depends on the bearing capacity of friction type on the friction force and the anti sliding coefficient of friction surface quantity, blasting (pill) after the red rust of the friction coefficient of the highest, but from the practical point of view by the level of construction has great influence, many supervision units are put forward to reduce the standard to ensure the engineering quality. The bearing capacity of a pressure bearing depends on the minimum shear resistance of the bolt and the compressive capacity of the bolt. In the case of only one joint, the shear strength of M16 is 21.6~45.0kN, while the shear strength of M16 bearing is 39.2~48.6 kN, and the p