How To Avoid Locking And Discoloration Of Stainless Steel Screws

When assembling stainless steel screws, locking phenomenon is often encountered. Lock, also known as bite, refers to the phenomenon of bolt and nut biting and locking during the tightening process, especially between stainless steel screws and nuts. Meanwhile, stainless steel screws may also experience discoloration. Below, we will explore how to avoid the locking phenomenon of stainless steel screws and the reasons for discoloration.

The reasons for stainless steel screw locking may include the following:

The inclination angle of thread fitting and the softer characteristics of stainless steel: During installation, uneven or inclined force application can cause the central axis of screws and nuts to tilt too much, making the thread vulnerable to damage and leading to biting and locking phenomenon.

Excessive locking force and low thermal conductivity of stainless steel: Stainless steel screws generate frictional heat during rotation, while stainless steel has a lower thermal conductivity. When the pressure and heat generated damage the chromium oxide layer of stainless steel, the metal teeth will directly block or shear, and in addition, stainless steel is relatively soft and prone to adhesion. The greater the locking force, the greater the heat generated, and the stainless steel screw teeth are prone to adhesion.

To avoid locking and discoloration of stainless steel screws, the following measures can be taken:

Apply attention evenly during installation, avoid tilting, and ensure the vertical alignment of the screw and nut center axis.

Control the magnitude of the locking force to avoid excessive pressure. Meanwhile, lubricants can be used to reduce the generation of frictional heat, making screw rotation smoother.

Choose high-quality stainless steel screws and nuts to ensure their surface is smooth, free from scratches or damage.

The reason for the discoloration of stainless steel screws:

Incomplete cleaning: During the cleaning process after screw work hardening, if the cleaning solution is not completely cleaned, it will remain on the surface of stainless steel screws, and chemical reactions will occur over time, leading to discoloration.

Surface phosphating treatment: The phosphating treatment film on the surface of screws may cause the appearance of red rust after quenching and tempering. To avoid discoloration of the screws, it is recommended to remove the phosphating film before heat treatment and moderately control the temperature in the furnace area.

Residual water quenched substance after quenching: If the water quenched substance remains in the stainless steel screw after quenching, it will cause a decrease in the rust prevention performance of the stainless steel screw and result in blackening after use for a period of time. Therefore, during the application process, it is necessary to regularly check the residual situation of water quenched materials to prevent discoloration of the surface of stainless steel screws.

In summary, to avoid locking and discoloration issues with stainless steel screws, attention should be paid to evenly applying, controlling the magnitude of locking force, selecting high-quality screws and nuts, and performing appropriate cleaning and surface treatment.