Bolt Stress Mode And Grade Meaning

Bolts come in two types: Ordinary and reamed. Ordinary bolts primarily bear axial forces, but can also withstand less demanding lateral forces. Reamed bolts, which require a specific hole size, are used when subjected to lateral forces.

According to relevant standards, carbon steel and alloy steel bolts are classified into more than 10 performance grades, including 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, and 12.9. Bolts of grade 8.8 and above are made of low-carbon alloy steel or medium-carbon steel and undergo heat treatment (quenching and tempering), commonly referred to as high-strength bolts. The rest are commonly referred to as ordinary bolts. The bolt performance grade designation consists of two parts: the nominal tensile strength and the yield strength ratio of the bolt material. Stainless steel bolts are classified according to the steel's performance grade: A1-50, A1-70, A1-80, A2-50, A2-70, A2-80, A3-50, A3-70, A3-80, A4-50, A4-70, A4-80, A5-50, A5-70, A5-80, C1-50, C1-70, C1-110, C4-50, C4-70, C3-80, F1-45, and F1-60. The first letter and number represent the stainless steel group, and the second and third numbers represent 1/10 of the tensile strength.