Classification of strength grades for high-strength bolts

Classification of strength grades for high-strength bolts

The full name for high-strength bolts in production is high-strength bolt connection pair, which is generally not abbreviated as high-strength bolts. According to the installation characteristics, it can be divided into large hexagonal head bolts and torsional shear type bolts.

Torsional shear type bolts are only used in grade 10.9. According to the performance level of high-strength bolts, they can be divided into 8.8 and 10.9 levels.

Among them, Grade 8.8 only has large hexagonal high-strength bolts. In terms of marking method, the number before the decimal point represents the tensile strength after heat treatment; The number after the decimal point represents the yield strength ratio, which is the ratio of the measured yield strength value to the measured ultimate tensile strength value. The meaning of grade 8.8 is that the tensile strength of the bolt rod is not less than 800MPa, and the yield strength ratio is 0.8; The meaning of grade 10.9 is that the tensile strength of the bolt rod is not less than 1000MPa, and the yield strength ratio is 0.9. In structural design, high-strength bolts generally have diameters of M16/M20/M22/M24/M27/M30, but M22/M27 is the second choice series. Normally, M16/M20/M24/M30 is the main choice.