FAQs

What does "Adhesion strength to iron surface" mean?

This is the force you need to apply to peel the magnet off a thick (e.g. 20 mm), smooth (polished) iron plate (technically pure iron). This force IS NOT a magnetic characteristic of the material, nor is it even a characteristic of the magnet. It only allows you to roughly compare the capabilities, in terms of attraction and repulsion, of magnets of different sizes, shapes and materials.

For the same magnet material, this force depends on:

the shape and size of the magnet;
the material of the surface to which the magnet is attached – pure iron, alloy steel or other ferromagnetic material. Pure iron provides the greatest adhesion force, while alloy steels provide less. For example, some stainless steels do not “stick” at all;
the shape and size of the object to which the magnet is attached; If the magnet is large (for example, Ф30х15 mm), and the surface is thin sheet metal (0.1 - 0.5 mm), the adhesion force will be much smaller than with thick sheet metal (15 -20 mm). To the same magnet, a wrench will stick with a force hundreds of times greater than to a pin;
a gap between the magnet(s) and the object being attracted. The reduction in the force of attraction between two magnets depends on the 3rd power of the distance between them. When a magnet interacts with an iron object, this force weakens even faster with increasing distance. Therefore, sometimes even a thin layer of paint has an effect on the attraction.

For specific situations in which you will use magnets, you can contact us for advice. In most cases, a sample (experiment) will give you the most accurate answer to the question “What is the adhesion force?” for the specific application.

How are magnets magnetized?

The possible magnetization methods (pole configurations) of magnets are given below. In the case of anisotropic magnets, the direction of magnetization is set during the manufacturing process. Therefore, they are available magnetized only in a certain way (in a fixed direction or axis). Such are neodymium magnets and anisotropic ferrites (Hfer30/22). Isotropic magnets are suitable for one-sided, two-pole and multi-pole magnetization. Ferrite magnets of the type (Hfer8/22) and magnetic foil are isotropic. Isotropic AlNiCo and neodymium magnets can also be manufactured, but in this case their magnetic characteristics are significantly lower.

Bipolar along the H or C axis

Bipolar, diametrical

Bipolar, one side

Bipolar, on both sides

Multipolar (strip, sector), on one side

Multipole on the surrounding surface
(for cylindrical and ring magnets)

Is using two glued magnets of thickness C equivalent to one magnet of thickness 2C?

The rule applies with great accuracy to 3,4,5, etc. magnets, but as the number increases, the accumulating air gap between the magnets may begin to have an impact. For other methods of magnetization, in most cases the above rule is inapplicable.

How long do magnets retain their magnetism?

Although they appear unchanged, over a long period of time, magnets partially lose their magnetization.
This happens to different degrees for different types of magnets.
AlNiCo magnets are the most resistant, both in terms of time and repeated temperature changes during operation. If they are not subjected to strong external magnetic fields, the change in about 30 years is no more than 2-5%.
Neodymium magnets are the most resistant to strong external magnetic fields and at constant room temperature they rival AlNiCo in resistance. Unfortunately, they are very sensitive to temperature changes, especially near and above the maximum operating temperature.
Ferrite magnets are the most noticeably demagnetized over time. They change their magnetization significantly with temperature changes (but can operate at significantly higher temperatures than neodymium magnets). However, in cases where a change of 10-15% is not significant, they can be used for practically an unlimited time.