Magnetic saturation
I bought a strong magnet - why doesn't it work? We often have people who ask why their magnet doesn't work or doesn't stick better. This is due to the phenomenon of "magnetic saturation". If the surface is thin or does not cover the entire surface of the magnet, the magnet saturates too quickly, and then it does not work optimally. A magnet has to have something to hold on to. And if it didn't make sense with saturation in relation to the sugar analogy, you can also describe it as magnets being divided into many small domains (magnetic areas). When the magnet has to grab hold of something, it grabs perhaps with 1,000 domains. But if the other party only has 100 domains to grab hold of, it doesn't hold on very well, because then the last 900 of the magnet's domains have nothing sensible to do... You'd probably rather have two hands to grab you than 1 if you're about to fall.
So it's really nice to buy strong magnets, but you also need a magnetic counterpart to make sure your magnet doesn't saturate too quickly.< /p>
Magnetic saturation is a somewhat abstract concept, and although it can be explained quickly in everyday language, we will still go a little more in depth so that you can learn more about what it means with magnetic saturation and why it is important in relation to the choice of magnets to know something about the magnetic saturation.
To make it really easy, you can watch a video about it here:
The video was made by Peter Valberg, where he shows one of our biggest hook magnets.
First we need to get two things in place:
- Strength
- Carrying capacity
Ad 1: strength
Magnets are provided with specifications for strength (often stated in kg.), translated into everyday language is about how much it takes to pull the magnet off a sheet of pure steel. The direction for this is a direct pull in the same direction as the magnet (a bit like pulling on a fridge door where you feel resistance).
Ad. 2: carrying capacity
One can also talk about carrying capacity, and it is banal enough the ability of the magnet to carry something - i.e. the indirect pull on the magnet. If you put the magnet in the ceiling and hang something on it that just hangs straight down (vertically) and doesn't move, then you can get full strength. But if you put the magnet on the wall and hang something on it (so the magnetic field is horizontal but the object is vertical), gravity must be taken into account as a parameter, and then you achieve much less bearing capacity than strength. The same applies if something hangs in motion; then the same carrying capacity as strength is not achieved either.
A good rule of thumb is that the carrying capacity is 15% of the magnet's strength. But it depends on several factors - so feel free to contact us if we need to calculate your strength requirement before purchase.
Magnetic saturation in relation to strength and bearing capacity
The quick conclusion is that it depends on the counterpart you put against the magnet (magnetic surface or, for example, things you want to fish up), whether the magnet achieves the full conditions for this strength and thereby draws the strength that is given up.
But it only says something about the result and does not explain the concept, so we go a little deeper into magnetic theory...
In the video, Peter shows a magnet with 200 kg. in strength and how he easily removes the magnet from the whiteboard without much effort. This is due to the magnetic saturation.
There is a big difference between different magnetic surfaces: the thicker the steel, the higher the saturation.
Magnetic saturation on a whiteboard
A whiteboard typically consists of a very thin metal plate behind a writable surface that creates a distance between magnet and metal. So in addition to the metal being thin, there is also a non-magnetic barrier between the magnet and the steel that also affects the saturation of the magnet. And when you put a strong magnet on the whiteboard, the area around the magnet quickly becomes "magnetically saturated", so that the magnet cannot use its full strength. And the same goes again with regard to carrying capacity, because when the area is saturated quickly, the magnet does not hold particularly well, and thus it cannot carry very much. And there is one more factor on whiteboard surfaces, because they are also very smooth, and this creates another challenge for the bearing capacity.
Conclusion: the whiteboard gets saturated too quickly (or too easily), and thereby the magnet does not achieve full strength and load-bearing capacity.
Magnetic saturation on a thick metal plate
In the video, Peter shows a metal plate that is approx. 30 mm. thick. When attaching a magnet to metal that is more than 5 mm. thick, the magnet has more difficulty saturating the metal magnetically, and thereby you quickly achieve the full strength of the magnet.
Conclusion: the thick metal plate is not saturated by the magnet, and thereby the magnet achieves full strength and carrying capacity.
p>
So in other words: if a magnet is easily saturated, its potential is not utilized.
If magnets were sugar...
A really good comparison - to explain magnetic saturation with an everyday thing - is to take a glass of water and a bag of sugar. You can easily dissolve a little sugar in the water. But as you put more and more sugar in the water, it becomes harder and harder to dissolve all the sugar because the water has become saturated. In relation to magnets, this means that the less saturation they are exposed to, the stronger they are.
Test of magnet saturation
4:50 minutes into the video, Peter puts the 200 kg. strong magnetic hook on the thick metal plate. But he has put a layer of plexiglass in between to create distance, because otherwise he will have to pull the magnet off with a pull of 200 kg. And it will be difficult to do alone man without tools. This is because, as we also discussed above with the whiteboard, distance also affects strength and carrying capacity. But here you will have to watch the video because too much is lost by writing it down. It must be experienced to get the full understanding of the project and the phenomenon of "distance".