Brief introduction of bolt mark, performance grade and process flow

Bolt is the most common fastener in fastener, bolt is everywhere in life. In order to let you have a preliminary understanding of the marking, performance level and process flow of bolts, the following China standard parts network takes hexagon bolt as an example to briefly explain the relevant knowledge, so that everyone can see at a glance.
One. sign
Hexagon head bolts and screws (thread diameter ≥ 5mm) shall be marked with raised or depressed characters on the top or side of the head, or with four characters on the side of the head.
1) Including: performance level and factory standard.
2) Carbon steel: strength grade marking code consists of two parts separated by ".".
3) The meaning of the number before "." in the marking code indicates the nominal tensile strength, for example, "4" in grade 14.8 is 1 / 100 of the nominal tensile strength of 400N / mm2.
4) The meaning of "." in the marking code and the number after the point indicate the yield ratio, i.e. the nominal yield point or the ratio of nominal yield strength to nominal tensile strength.
5) For example, the yield point of grade 4.8 product is 320n / mm2.
6) The strength grade mark of stainless steel products consists of two parts separated by "one".
7) The symbol before "-" in the symbol code indicates the material. For example, A2, A4, etc,
8) "One" indicates strength, such as A2-70

Two. Grade
Carbon steel:
The mechanical property grade of metric bolt can be divided into: number before point * 100 and number before point * 10 point after point.
Stainless steel is divided into:
Austenite: 60,70,80.
Martensite: 507080110.
Ferrite: 45,60.
3. technological process
Production process:
(1) , Yuan:
1。 Disk element refers to the original wire rod purchased from the manufacturer. The disk components mainly include the following parameters:
A. Brand; B, product name; C, specification; D, material; E, heat number or batch number; F, quantity / weight;
2。 The main chemical composition of steel is C, Mn, P, s, Si, Cu and al. The lower the content of AI and Cu, the better
(2) Annealing: eliminate the internal stress in wire processing and improve its malleability.
(3) Pickling: remove the oxide film on the surface of wire rod, lubricate the surface of wire rod, and facilitate wire drawing.
(4) Take out the wire: in order to achieve the wire diameter we need.
(5) Yes. Head (forming) and tooth profile rolling: finish product shape and tooth profile.
(6) Heat treatment: change the mechanical properties of screws.
(7) Electroplating: can meet the customer's requirements for surface treatment, but also can increase some properties of screws. Such as rust, beauty, etc.
(8) Yes. Packing: packing the products into boxes / boxes according to the standards or customer requirements.
Main products: steel structure bolts and nuts, high strength bolts and nuts, hexagon bolts, hexagon nuts, chemical bolts and nuts and other special-shaped parts.