Bolts made of high-strength steel, or bolts that require a larger pre-tightening force, can be called high-strength fishtail bolts. High-strength fishtail bolts are mostly used for bridges and rail connections. The fracture of this type of bolt is mostly brittle fracture. High-strength bolts applied to ultra-high pressure equipment need to be prestressed in order to ensure the sealing of the container. High-strength fishtail bolts can bear a larger load than ordinary bolts of the same specification.
2.From the comparison of strength grades, high-strength fishtail bolts are widely used. Two strength grades of 8.8 and 10.9 are commonly used, of which 10.9 is the majority. The strength grade of ordinary fishtail bolts is much lower, generally 4.8 and 6.8.
3.From the comparison of the force characteristics, the high-strength fishtail bolt exerts pretension and transmits external force by friction. Ordinary fish-tail bolt connections rely on the shear resistance of the bolt rod and the pressure of the hole wall to transmit the shear force. The pre-tension force generated when the nut is tightened is very small, and its effect is negligible. In addition to the high strength of the material, the high-strength fishtail bolt also applies a large pre-tension to the bolt, which generates a pressing force between the connecting members, so that there is a large friction force perpendicular to the screw direction, and the pre-tension , Anti-slip coefficient and steel type directly affect the bearing capacity of high-strength fishtail bolts.