Processing procedures of fastener screws
The manufacturing process of fastener screws includes: wire rod - annealing - pickling - cold heading -thread rolling - heat treatment - electroplating - packaging.
1. Wire Rod
Raw wire rod (raw material) purchased from the manufacturer.
2. Annealing
The wire is heated to the appropriate temperature, kept for a certain time, and then cooled slowly to adjust the crystal structure, reduce hardness, improve the wire at room temperature processing.
3. Pickling
Objective: To remove the oxide film on the wire surface and form a phosphate film on the metal surface in order to reduce the scratch on the die during wire drawing and cold pier or forming.
Operation process:
1) Pickling: The whole dish was immersed in three acid tanks with a concentration of 20-25% at room temperature for several minutes respectively to remove the oxide film on the wire surface.
2) Clear water: Remove hydrochloric acid corrosion products on the wire surface.
3) Oxalic acid: Increase the activity of the metal to make the skin membrane generated in the next process more compact.
4) Skin film treatment: The diskette is immersed in phosphate, the steel surface is in contact with the treatment solution, and the steel dissolves into insoluble compounds (such as Zn2Fe (Po4) 2.4H2O), which are attached to the steel surface to form a skin film.
5) Clear water: Remove the residue on the surface of the skin film.
6) Lubricants: Because the friction coefficient of phosphate skin film is not very low, it cannot give sufficient lubrication during processing, but reacts with metal soap (such as sodium soap) to form a hard metal soap layer, which can increase its lubrication performance.
4.Cold heading
Cut off the wire, upset the screw into a blank, form the head, make the cross groove (or other head type) thread blank diameter and rod length, head under the round corner, etc.
5. Thread rolling
6. Heat treatment
Strengthen the strength, hardness and bremsstrahlung of screws. A good screw must not be too hard - a lock will break easily, nor too soft - it will slip and the teeth will not lock properly, so heat treatment is necessary for the screw to have the properties of external steel and internal flexibility.
7. Electroplating
