Release time：2020-01-16 18:44 Browse：
How to produce extra long screws below M3?
The production of extra long screws below M3 (such as M1.2, M2, M2.5, etc.) requires special processes and equipment adjustments to ensure their structural strength and assembly performance. The following is a detailed production process and key technological points:
1. Material selection
Wire requirements: Small screws below M3 are usually made of high carbon steel (such as 1018, 1022) or stainless steel (such as 304, 316) to ensure sufficient strength and corrosion resistance.
Disk element specification: The initial wire diameter should be slightly larger than the tooth diameter of the finished screw (for example, M1.2 screws usually use 1.4-1.6mm disk elements).
2. Annealing and acid washing
Spheroidization annealing: Annealing high carbon steel at 680-715 ℃ to reduce hardness and improve cold heading plasticity.
Acid pickling phosphating: removes oxide scale and forms a phosphate film on the surface, which facilitates subsequent drawing and cold heading.
3. Precision drawing
Rough and fine drawing: gradually pull the wire to the diameter close to the target screw (such as pulling M1.2 screws to 1.2-1.3mm), ensuring dimensional accuracy of 13.
Lubrication treatment: Reduce friction during the drawing process and prevent surface scratches.
4. Cold heading forming (key difficulty)
Special equipment adjustment: Screw sizes below M3 are extremely small, requiring the use of high-precision multi station cold heading machines (such as DT06102 type) and optimization of mold clearance 1.
Extension rod processing:
Step by step forging: Due to the long length of the rod, multiple forging steps are required to avoid bending or fracture.
Mold oriented optimization: Add a guiding structure to ensure that the long rod maintains straightness during the molding process.
Head forming: adopt the the first mock examination and two punching process, pre forming before final forging, to avoid uneven material flow.
5. Rubbing teeth (threading)
Precision tooth plate: Use high hardness alloy tooth plates (such as SKD11) to ensure thread accuracy.
Low speed threading: Reduce the threading speed (150000-200000 times/day) to minimize the risk of deformation of long rod screws during the threading process.
6. Heat treatment (if necessary)
Carburizing or tempering: carburizing (surface hardening) or tempering (overall strengthening) carbon steel screws to improve their mechanical properties.
Dehydration treatment: If electroplating, it is necessary to bake at 200 ℃ for 8 hours to prevent hydrogen embrittlement.
7. Surface treatment
Galvanized/nickel plated: enhances rust prevention ability, suitable for small screw 1.
Dacromet: Suitable for occasions with high anti-corrosion requirements.
8. Quality inspection
Dimensional verification: Use an optical measuring instrument to check the rod length and thread accuracy.
Torque test: Ensure that the screw can withstand the specified assembly torque of 8.
Key challenges and solutions
Long pole stability:
Use a mold clamping machine or special guiding device to avoid bending during cold heading.
Thread strength:
Optimize the parameters of tooth rubbing to avoid incomplete or broken teeth.
Production efficiency:
The production of extended screws below M3 is relatively low (about 50000-80000/day), and the production pace needs to be adjusted
