Perhaps many people have had headaches due to the inability to remove screws due to adhesion, right? Forcibly disassembling adhesive screws can lead to screw breakage, damage to concave holes such as hexagonal holes, and tool damage, which requires a lot of labor and time.
In order to prevent more people from suffering from screw adhesion, today Xiaorui will take everyone to understand the problem of screw adhesion.
Firstly, what is screw "adhesion"?
Adhesion refers to the phenomenon where screws cannot rotate for some reason, sometimes also known as sintering.
Why do screws stick?
The reasons for screw adhesion can be roughly divided into:
1) Friction heat of screw teeth
2) External reasons such as foreign objects
These two types.
Friction heat of screw teeth
When tightening screws, the screws expand due to frictional heat, and the thread deposits will cause adhesion.
This is why stainless steel screws are more prone to adhesion compared to steel materials.
Because compared to steel, stainless steel,
1. High friction coefficient (twice that of steel), easy to generate heat
2. Low thermal conductivity (1/3 of steel), difficult to dissipate heat
3. The coefficient of thermal expansion is large (twice that of steel), and the external and internal threads are easy to tightly fit
Therefore, screw teeth are prone to deposition.
Moreover, in high-temperature environments, adhesion is more likely to occur, and attention should also be paid to using steel screws.
External reasons such as foreign objects
On the other hand, screws made of steel can also cause adhesion due to:
1. Tighten when foreign objects such as chips are attached
2. Excessive tightening torque, some threads broken
3. The surface roughness of the screw teeth is large or there are dents
Wait a minute.
So how can we prevent "adhesion" from happening?
Firstly, for external reasons, it is necessary to confirm the state of the screw teeth before tightening, and tighten them with appropriate torque to prevent adhesion.
So, how can we prevent the adhesion caused by the friction heat of the screw teeth? It may seem difficult to change the thermal conductivity and thermal expansion coefficient of materials, but reducing the friction coefficient is feasible.
For example,
Apply lubricant
Implement surface treatment
These measures are all feasible.
But after the friction coefficient decreases, the screws will become easier to tighten. If the tightening torque remains the same, the screw teeth will be damaged. If there is adhesion caused by external reasons, it will not be worth the loss.
In summary, when taking measures to change the friction coefficient, attention should be paid to adjusting the tightening torque.
In addition, the main reason for the adhesion and sintering of screws is the frictional heat generated on the surface of the screw teeth during tightening. By using special surface treatment to reduce the friction coefficient of the screw tooth surface, compared to screws without surface treatment, even if tightened with the same torque, a larger axial force can be obtained. As a result, the generation of frictional heat can be suppressed by reducing the tightening torque, preventing screw adhesion or sintering.
Comparison of spectral reflectance after different surface treatments
Low temperature black chromium plating and stainless steel blackening treatment can significantly reduce the spectral reflectance, making it the most suitable for optical devices that require the prevention of diffuse reflection.
In clean environments where lubricants cannot be used and coating peeling is a concern, screws SNSL-PN that prevent adhesion by hardening the surface can also be used. When adhesion measures are needed, please consider using them.
