1. Disk element
Refers to the original wire rod (raw material) purchased from the manufacturer
The wire is heated to an appropriate temperature, kept for a certain period of time, and then slowly cooled to adjust the crystal structure, reduce the hardness, and improve the normal temperature workability of the wire.
Purpose: To remove the oxide film on the surface of the wire, and to form a phosphate film on the metal surface to reduce the scratches on the tool and die during the wire drawing, cold piercing or forming process.
1) Pickling: immerse the entire disk element in three hydrochloric acid tanks with a concentration of 20-25% at room temperature for several minutes, the purpose is to remove the oxide film on the surface of the wire.
2) Clear water: remove the hydrochloric acid corrosion products on the surface of the wire.
3) Oxalic acid: increase the activity of the metal to make the film generated in the next process more dense.
4) Coating treatment: immerse the disc element in phosphate, contact the steel surface with the chemical treatment solution, and dissolve the steel to form insoluble compounds (such as Zn2Fe(Po4) 2.4H2o), which adhere to the steel surface to form a coating.
5) Clear water: remove residues on the surface of the film.
6) Lubricant: Since the friction coefficient of the phosphate film is not very low, it cannot give sufficient lubricity during processing, but it reacts with metal soap (such as sodium soap) to form a hard metal soap layer, which can increase its lubricating performance.
4. Cold heading
Cut the wire, upset it into a screw blank, form a head, make a cross groove (or other head type) thread blank diameter and rod length, and fillet under the head.
5. Thread rolling
6. Heat treatment
Strengthen the strength, hardness and stability of its screws. A good screw can't be too hard - it will be easy to break when locked, nor too soft - easy to slip and will not be locked tightly, so to make the screw have the characteristics of outer steel and inner softness, it must be heat treated.