Brief introduction of bolt mark, performance grade and process flow

Brief introduction of bolt mark, performance grade and process flow

Bolt is the most common fastener in fasteners, and bolts are everywhere in life. In order to let you have a preliminary understanding of the marking, performance grade and process flow of bolts, the following China standard parts network takes hexagonal bolts as an example to briefly explain the relevant knowledge for everyone to see.

I. 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 four characters on the side of the head.

1) Including: performance level and factory standard.

2) Carbon steel: the strength grade marking code is composed of two parts of numbers 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 indicates 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, that is, 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

II. grade

Carbon steel:

The mechanical property grade of metric bolts can be divided into: number before point *100 and number before point *number after 10.

Stainless steel is divided into:

Austenite: 60,70,80.

Martensite: 507080110.

Ferrite: 45,60.

III. process flow

Production process:

(1) , Yuan:

1. Disk components refer to the original wire rod purchased from the manufacturer. Disk components mainly include the following parameters:

A. Brand; B. Product name; C. Specifications; D. Material; E. Heat number or batch number; F. Quantity/weight;

2. The main chemical compositions of steel are: C, Mn, P, s, Si, Cu, al. The lower the content of AI and Cu, the better

(2) Annealing: eliminate the internal stress of wire processing and improve its malleability.

(3) Pickling: remove the oxide film on the wire rod surface, lubricate the wire rod surface, and facilitate wire drawing.

(4) Take out the wire: in order to reach the wire diameter we need.

(5) Yes. Head (forming) and tooth profile rolling: complete the product shape and tooth profile.

(6) Heat treatment: change the mechanical properties of screws.

(7) Electroplating: it can meet customers' requirements for surface treatment, and also can increase some properties of screws. Such as rust prevention, beauty, etc.

(8) Yes. Packaging: package the products into boxes/boxes according to standards or customer requirements.

The company is mainly engaged in high-strength bolts, high-strength nuts, steel structure bolts, steel structure nuts, space frame sealing plate, space frame bolts, etc.