Strength grades are classified according to mechanical properties. According to the relevant standards, the bolt performance grade is divided into 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9 and more than 10 grades, of which 8.8 and above bolts made of low-carbon alloy steel or medium carbon steel and heat treatment (quenching, tempering), commonly known as high-strength bolts, the rest are commonly known as ordinary bolts. The bolt performance grade number has two parts consisting of numbers, which indicate the nominal tensile strength value of the bolt material and the flexural strength ratio. For example.
Shock-absorbing bolt; consisting of a screw, a rubber column, said screw has a screw head larger than its diameter, said screw head of the screw is embedded in the two ends of the rubber column, the end face of the screw head near the thread is flush or slightly convex with the end face of the rubber column, and the screws at both ends of the rubber column are coaxial.