Cold welding also known as Thread Galling is a phenomenon that can occur during the tightening - mainly at high speed - of threaded connections. It is caused by a combination of pressure and friction (high friction value in stainless steel). You notice it when, while tightening a bolt, the threads get stuck in a nut or tapped hole. And, once the bolt is stuck you usually can't remove it the normal way. Then it becomes grinding, drilling or tapping.
How does cold welding occur?
During the tightening of fasteners, the pressure between the contact surfaces increases. This creates friction and damages the thread surface of both the external and internal threads.
These damaged surfaces then adhere to each other. The threaded connection seizes and, in extreme cases, the bolt or screw even breaks off.
Soft materials are often more sensitive than harder materials. Cold welding usually occurs with fasteners made of stainless steel, aluminum and titanium.
How to prevent cold welding?