The differences between rare earth magnets and ceramic magnets
A look at rare earth magnets versus ceramic magnets.
Magnets are objects that generate magnetic fields. These magnetic fields allow magnets to attract certain metals from a distance without touching them. Some magnets occur naturally, while others are man-made. While there are many different types of magnets, two of the most popular man-made magnets are ceramic magnets and neodymium magnets.
Advantages and Disadvantages
Rare-earth magnets and ceramic magnets are both types of permanent magnets; they are both composed of materials which, once given a magnetic charge, will retain their magnetism for years unless they become damaged. Not all permanent magnets are the same, however. Rare-earth and ceramic magnets differ in their strength and resilience because they are made from different metal alloys.
In Practice
Bluestreak Equipment offers magnetic sweepers that are ceramic and rare earth, a clear-cut example of the power difference of the two magnet types are shown in the video below. The Powerstik magnet is ceramic powered and fully packed, the Powerstik Pro Elite model has a fully packed rare earth magnet assembly. The holding capacity of the magnetic sweepers is shown in this video using the Powerstik & Powerstik Pro Elite to hold various pieces of metal debris. See Products Here
Video Transcript
So here’s the video comparing the Power Stick’s holding force compared to the new Pro and Pro Elite models. On the Pro, we’ve got eight railway spikes held on, as well as this plate and this square nut over here. On this one, you can see we only got four railway spikes, the one nut, and the one plate, and these are pretty well on there as well. The wraparound function really helps with this magnet to keep everything secure on there. And we’ll see what the other ones do.
So here’s a part of the comparison between the Power Stick Pro, the Power Stick Pro Elite, and the original Power Stick. Here we have the Pro version, and it’s got our Super Blue magnet technology inside of it. This is a demonstration just to show the holding power. We’ve got, what’s that, eight railway spikes, two large bolts, a rock plate, and a rock bolt shaft, and they’re on there pretty good.
We’re going to compare this to the original Power Stick and then the Elite, just so you can see the difference in strength. So here’s the power test for our Pro Elite model. Like the Pro, it’s got the eight railway spikes and the two square nuts and the plate here, but you can see we got another bolt, another big rock bolt, another piece of scrap, and on the other side, there’s about a three-quarter inch thick bolt on that side.
And I gotta say, this thing weighs probably 30 pounds, all this stuff on it, and it doesn’t feel like it’s going anywhere. Like, I’m giving it a pretty good shake, and this stuff’s not really moving.
So that just shows you the power level difference between the three sweepers: the Power Stick original got four spikes, the Pro got the eight spikes plus three other pieces of debris, and this got another four—what’s that, another five pieces of debris—on top of that. So this thing is by far the strongest magnet. Obviously, that’s why it’s the Pro Elite. But it’s quite a good magnet for collecting stuff because it has magnets all the way through the assembly, which is why we can put stuff on top, and it’s not going to fall when I do this.
Ceramic Magnets
For years all magnets were natural magnets such as lodestone, a naturally magnetic iron ore. In 1952 magnets were made from ceramic for the first time. By making magnets out of ceramic, engineers were able to make magnets into any shape they wanted. By making the ceramic magnets out of carefully created mixtures, more powerful magnet fields than were possible in nature could be generated. Ceramic magnets were less expensive and more powerful and quickly became popular. Ceramic magnets are also called hard ceramic magnets or ferric magnets. They are made from strontium or barium ferrite.
Rare Earth Magnets
There are two types of rare-earth magnets: samarium cobalt (SmCo) and neodymium-iron-boron (NdFeB). SmCo and NdFeB magnets are called “rare earth” because they are made from the rare earth, or lanthanide series, of the periodic table of elements.
SmCo magnets were developed in the 1970s and were the first of the rare-earth magnets to be produced. NdFeB magnets became available to buy in 1984.
Relative Strength of Ceramic versus Rare Earth Magnets
The strength of the magnetic field produced by a magnet is quantified with BHmax, or maximum energy product, which is measured in MegaGauss Oersted (MGOe). The higher the BHmax, the more powerful the magnet. Ceramic magnets have a BHmax of 3.5, SmCo have a BHmax of 26 and NdFeB are the most powerful of the rare-earth magnets with a BHmax of 40.
Relative Resistance to Thermal Stress of Ceramic versus Rare Earth Magnets
Magnets can begin to lose strength when they are heated beyond a certain temperature, known as Tmax, and should not be operated beyond this temperature. They will, however, regain their strength when cooled below Tmax. Ceramic magnets have a Tmax of 300 degrees Celsius, as do SmCo magnets, and NdFeB magnets have a Tmax of 150 degrees Celsius. If a magnet is heated too far beyond Tmax, it will eventually become demagnetized at a temperature known as Tcurie. When a magnet is heated beyond Tcurie, it will not recover once cooled. Ceramic magnets have a Tcurie value of 460 degrees Celsius, SmCo have a Tcurie of 750, and NdFeB have a Tcurie of 310 degrees.
Relative Durability of Ceramic versus Rare Earth Magnets
Along with their resistance to thermal stress, magnets also vary in their resistance to other stresses. NdFeB magnets are brittle and difficult to machine. They also corrode easily. SmCo magnets are slightly less brittle and are also difficult to machine, but have a high resistance to corrosion. SmCo magnets are also the most expensive type of magnet. Ceramic magnets are less costly than both SmCo and NdFeB magnets and have good resistance to demagnetization and corrosion.
Benefits of Each
Ceramic and neodymium magnets each have different benefits. Ceramic magnets are easy to magnetize. They are very resistant to corrosion and generally do not need extra coatings for corrosion protection. They are resistant to demagnetization by outside fields. They are stronger than natural magnets, though many other types of magnets are stronger than them. They are relatively inexpensive. Neodymium magnets are the most powerful of all permanent magnets. A neodymium magnet can lift more than any other type of magnet of the same size. They are extremely resistant to demagnetization by external magnetic fields.
Picking Up Less Ferrous Material with Rare Earth Magnets
Some types of metals are more difficult to pick up than others, alloys with less iron and more zinc or nickel in them to prevent rust are typically less magnetic. These metals are usually used in high quality fasteners that are difficult to pick up with typical ceramic magnets. Because of this situation Bluestreak offers rare earth versions of magnetic sweepers that have a higher gauss level than ceramic but at a higher cost. While not necessary in all situations, the extra gauss from the rare earth magnets vs the ceramic models makes the difference when trying to pick up lower ferrous content metals. The Vigilant forklift magnet is a ceramic, mid mounted magnetic sweeper that attaches to a forklift to continuously collect metal while the forklift works. The Defiant is exactly the same but has a rare earth magnet assembly for extra pickup and holding power, this was developed to collect high quality fasters around factories. The gauss chart below shows the difference in power levels and show how much more powerful a rare earth magnet can be when compared to a ceramic magnet that is the exact same size. See the Defiant Here
Vigilant Gauss Measurements
A: Distance from Magnet (Sweeping Height)
B: Note: Gauss (G) shown is the peak gauss, measured in the center of the magnet at each distance.
Defiant Gauss Measurements
A: A = Distance from Magnet (Sweeping Height)
B: Note: Gauss (G) shown is the peak gauss, measured in the center of the magnet at each distance.
Drawbacks of Each
Ceramic and neodymium magnets have different drawbacks as well. Ceramic magnets are extremely brittle and easily broken. They cannot be used in machinery that experiences a lot of stress or flexing. They become demagnetized if they are exposed to high temperatures (above 480 degrees Fahrenheit.) They have only a moderate magnetic strength, making them unsuitable for applications requiring powerful magnetic fields. Neodymium magnets are relatively more expensive than ceramic magnets. They rust very easily, and extra steps must be taken to protect them from corrosion. Neodymium magnets are also very brittle and will crack under stress. They lose their magnetism if exposed to temperatures above 175 to 480 degrees Fahrenheit (depending on the exact alloy used).
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