What is the method of marking the bolts?

Usually fastener bolts will use different marking methods to represent different meanings, such as hexagonal head bolts and screws (thread diameter ≥ 5mm), which need to be marked with convex or concave characters on the top of the head, or on the side of the head. Indented logo, including performance level, factory standard and other information.

Carbon steel: The strength grade code is composed of two numbers separated by "·". The meaning of the number part before the "·" in the mark code represents the nominal tensile strength, such as "4" in the 4.8 grade, which means 1/100 of the nominal tensile strength of 400N/MM2. The meaning of the "·" and the number after the point in the mark code indicates the yield-to-strength ratio, that is, the ratio of the nominal yield point or the nominal yield strength to the nominal tensile strength. For example, the yield point of grade 4.8 products is 320 N/mm2.

The strength grade mark of stainless steel products consists of two parts separated by "—". The symbol before "—" in the sign code indicates the material. Such as: A2, A4 and other signs "—" indicate the strength, such as: A2-70 and so on.