Residual magnetism in gears: what it is and why it matters

luglio 02, 2024

Have you ever heard of residual magnetism in gears without knowing exactly what it is? This article introduces the concept of residual magnetism, explaining where it comes from, the potential damage it can cause and how it is measured.

What is residual magnetism and where does it come from?

Residual magnetism is a small amount of magnetism that remains in a metallic material even after the external magnetic field that caused it has been removed. Imagine rubbing a magnet on a piece of metal and then removing the magnet: the metal may remain slightly magnetic.

Residual magnetism in gears can result from various processes:

production: gears are mainly produced using metallic materials which, being magnetic, can easily retain residual magnetism. During manufacturing, components can be subjected to controlled heat treatments that eliminate residual magnetism. Furthermore, dedicated demagnetizers can be used to reduce or completely eliminate residual magnetism.
Handling and assembly: Contact with other magnetic objects or magnetic fields during assembly can induce residual magnetism in the gears.
lifting systems: In heavy gears, magnets combined with lifting systems such as winches are often used. These magnets can induce residual magnetism in gears.

Why can residual magnetism cause damage?

Although it may seem harmless, residual magnetism can negatively affect the operation of gears, especially in precision applications. Here's how residual magnetism can compromise the precision and reliability of gears:

particle attraction: Residual magnetism can attract metal particles or dust that can stick to gears. This can cause uneven wear or block the movement of gear teeth, affecting the accuracy of the movement.
Magnetic Interference: Residual magnetism can cause magnetic interference with other sensitive components nearby. This can alter the surrounding magnetic field and affect the accurate operation of the gears.

How residual magnetism is measured: regulations and standards

Residual magnetism is measured with specific instruments such as magnetometers and induction probes, which detect the strength of the residual magnetic field in the metal. These measurements are important to ensure that the level of residual magnetism is below acceptable limits.

There are regulations that define the acceptable limits of residual magnetism in certain sectors. Here are some of the most relevant regulations:

ISO 9934-1: this standard concerns the magnetoscopic control of ferromagnetic materials. While it does not specify residual magnetism limits, it does offer guidelines on magnetoscopic test methods.
din 54132: This German standard describes methods for measuring residual magnetism and specifies maximum acceptable limits for various industrial applications.
astm e1444/e1444m: US standard for magnetoscopic testing that includes procedures for testing residual magnetism in ferromagnetic materials.

In conclusion, residual magnetism can have a significant impact on the precision and reliability of gears, especially in contexts where high performance and tight tolerances are required. For further information, contact us at sales.gsi@gsi-ingranaggi.it.

Residual magnetism in gears: what it is and why it matters

What is residual magnetism and where does it come from?

Why can residual magnetism cause damage?

How residual magnetism is measured: regulations and standards

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