Tue. Oct 3rd, 2023

Galling is a form of metal wear that occurs when one piece of metal unintentionally adheres to another metal surface that it touches. The adhesion between the two surfaces is often the result of high amounts of friction and ductility in the metals involved. The problem is common and can cause expensive equipment to malfunction or break down completely. This article explains what is galling and offers some tips on how to prevent it from occurring during fastener applications.

The occurrence of galling is most prominent in softer metals, such as aluminum and stainless steel austenitic grade fasteners. Hardened materials like tool steels and martensitic stainless steels are less likely to experience galling issues. The condition is primarily a result of friction between the metals. The higher the amount of friction, the greater the chance that the metals will begin to bond together and create a solid mass between them. The resulting bond may be seen as bumps or streaks on the surface of the fastener or may simply be felt as a noticeable increase in resistance during use.

Several factors can cause metal galling, but the most important factor is the amount of friction between the contacting surfaces. The amount of heat generated during fastening is the primary source of friction, but other factors such as abrasion and vibration can also contribute to the condition. In general, larger threads have a higher risk of galling than smaller ones. The roughness of the threaded surfaces and the presence of debris can also significantly increase the chances of galling.

When it comes to preventing galling, there are several steps that can be taken. The first is to choose a dissimilar metal for the application. Using a different material will reduce the risk of galling because the new metal will not share the same ductility and abrasion characteristics as the softer, original metal. It is also advisable to use an appropriate amount of lubrication to reduce the friction between the fastener and its mate.

A lubricant can also help to ensure that the threaded surface is properly cleaned and free of dirt, grease and other contaminants. In addition, it is recommended that the wrench used for tightening the fastener be of the appropriate size and power to avoid excessive stress on the surface of the metal.

In many cases, it is possible to eliminate galling completely by taking precautionary measures and following best practices during fastener installation. For example, purchasing a high quality fastener from an ISO 9001 supplier with well-groomed, precision threads will decrease the likelihood of galing. Threads that are damaged or rough will generate more friction and should be electropolished or ground before installing to reduce the chances of galling. Also, reducing the torque of the fastener will minimize the amount of heat generated and the possibility of galling. Lastly, the choice of a suitable lubricant can dramatically reduce the risk of this frustrating issue. Choosing a lubricant with an oily consistency can also help to reduce the likelihood of galling because it will be more difficult for the threads to snag on each other.

By Admin

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