Brief introduction to bolt markings, performance levels, and process flow

Brief introduction to bolt markings, performance levels, and process flow

Bolt is the most common fastener among fasteners, and bolts are ubiquitous in daily life. In order to give everyone a preliminary understanding of the marking, performance level, and process flow of bolts, the following Chinese standard parts website takes hexagonal bolts as an example to briefly explain the relevant knowledge, so that everyone can have a clear understanding at a glance.

One. sign

Hexagonal head bolts and screws (thread diameter ≥ 5mm) should be marked with raised or recessed 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 standards.

2) Carbon steel: The strength grade marking code consists of two numbers separated by '.'.

3) The meaning of the digits before "." in the marking code represents the nominal tensile strength, for example, "4" in level 14.8 represents 1/100 of the nominal tensile strength of 400N/mm2.

4) The meaning of "." in the marked code and the number after the dot indicate the yield ratio, which is the ratio of the nominal yield point or nominal yield strength to nominal tensile strength.

5) For example, the yield point of a 4.8 grade product is 320n/mm2.

6) The strength grade mark of stainless steel products consists of two parts, separated by a "one".

7) The symbol before "-" in the symbol code indicates the material. For example: A2, A4, etc,

II. grade

Carbon steel:

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

Stainless steel is divided into:

Austenite: 60,70,80.

Martensite: 507080110.

Ferrite: 45,60.

III. process flow

Production process:

(1) , yuan:

1. Disc components refer to the original wire rods purchased from the manufacturer. The disk components mainly include the following parameters:

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

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

(2) Annealing: Eliminating internal stress during wire processing and improving its malleability.

(3) Acid cleaning: Remove the oxide film on the surface of the wire rod, lubricate the surface of the wire rod, and facilitate wire drawing.

(4) Remove the steel wire: In order to achieve the required diameter of the steel wire.

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

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

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

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