According to the performance characteristics and functions of the fasteners used, the fasteners used in many fields are made of stainless steel, and the most common disadvantage of stainless steel fasteners is that the bolts and nuts cannot be unscrewed during use. , This phenomenon is “biting to die”, usually, we can also call it “locking” or “biting” problem. Why do stainless steel bolts and nuts have such a problem? How can we do a good job in preventing stainless steel fasteners from being bitten?

During the use of the bolt and the nut, once the biting occurs, the two fasteners will be difficult to separate. Usually, we will cut off the bolt or break the nut to realize the disassembly of the accessories, which will directly affect the speed of disassembly and assembly of the accessories and the re-usability of the fasteners. Therefore, we need to first analyze the principle and causes of the locking of stainless steel fasteners, and then analyze to find the most reasonable preventive measures to prevent the fastener bolts and nuts from being seized.

1. The principle of the seizure of stainless steel bolts and nuts

Stainless steel fasteners have rust resistance. When the surface is damaged, a thin oxide layer (in the case of austenitic stainless steel, it is chromium oxide) will be formed on the metal surface to prevent further and deeper rust. When the stainless steel fastener is locked, the pressure and heat generated between the teeth will destroy and erase the chromium oxide layer in between, causing the metal teeth to be blocked/sheared directly, and then the phenomenon of adhesion occurs. When the sticking phenomenon continues, the stainless steel fasteners will be completely locked and can no longer be removed or locked. Usually this series of blocking→cutting→sticking-→locking takes place in just a few seconds.

2. The reasons for the seizure of stainless steel bolts and nuts

By analyzing the principle of the seizure of stainless steel fasteners, it can be seen that the seizure of stainless steel fasteners is caused by the pressure or heat between the tooth patterns destroying the oxide layer, which makes the metal materials directly contact and further develop. Therefore, the excessive pressure or heat generated between the teeth often causes the stainless steel fasteners to die. For the following reasons, excessive pressure or heat is often generated between the teeth, which in turn causes the stainless steel fasteners to bite.

1) The tooth pattern is rough or there is foreign matter sticking. If solder joints and other metal shavings are caught between the teeth, it will often lead to seizure.

2) The tightening force is too large or the tightening speed is too fast. If the tightening force is too large, it is easy to generate a large pressure between the tooth lines and cause it to die; if the tightening speed is too fast, it is easy to cause the temperature between the tooth lines to rise rapidly and die.

3) The angle of the force direction is wrong. When tightening, the tightening direction is not perpendicular to the axial direction of the bolt, which is easy to cause seizure.