Stainless steel seizure

The most common assembly technique is screwing and bolting.

Screwing is no longer done manually, but has been replaced by the use of electric or pneumatic screwdrivers. Such tools involve a very high clamping force which can lead to the phenomenon of seizing.

Stainless steel screwed connections are regulated by standard NFE 25-035.

The surface condition of the material is usually a decisive factor in the onset of binge eating. In the case of stainless steel, however, other parameters also play a role.

When tightening a bolt on a nut, only 10% of the torque actually contributes to the tightening (axial force), the rest is lost in friction on the thread and under the head of the bolt (tangential force).

Friction is needed to keep it from loosening over time. However, if it gets too big, seizing occurs, which results from micro-adhesion, e.g. B. arise between the threads: It is impossible to loosen the nut and the screw may break under load. Solutions must therefore be found to avoid increased friction.

The measurement makes it possible to determine the torque from which there is a risk of seizure: The coefficient of friction must be constant, it indicates from a certain value

of torque, a significant increase in the coefficient of friction indicates seizure.

In order to increase the seizure threshold, it is necessary to act on the friction coefficient thread/thread and washer/nut (source: Institute for the development of stainless steel).

NFE 25-035 recommends subjecting screws or nuts, generally the latter, to a mechanical, chemical, thermochemical or other treatment. This standard also indicates that in torque-tension tests, the recommended speed must be between 10 and 25 rpm and that it must be continuous and regular.

One B January 2012 a Fasteners-Service the Decision encounter, HU- And

Provide brake nuts with lubricated "WAX" coating to reduce seizing.