Ordinary bolts are generally made of ordinary carbon structural steel without heat treatment. High strength bolts are generally made of high-quality carbon structural steel or alloy structural steel, which need to be quenched and tempered to improve the comprehensive mechanical properties. High strength is divided into 8.8, 10.9 and 12.9.
From the strength grade: high strength bolt commonly used 8.8s and 10.9s two strength grades. Ordinary bolts generally have grade 4.4, 4.8, 5.6 and 8.8.
According to the stress characteristics, high-strength bolts exert pretension and transfer external force by friction, while ordinary bolts transfer shear by bolt bar shear and hole wall bearing.