3. What is the difference between an electromagnet and a permanent magnet?
A permanent magnet is made from a “hard” magnetic material that maintains its magnetism over long periods of time once it is magnetized by an external magnetic field. The magnetism in an electromagnet is created and changed by current running through a coil of insulated wire that is wound around a piece of “soft” magnetic material.
4. Do magnets get rust?
It depends. Neodymium magnet is the only permanent magnet which is easy to rust because it contains iron element. Samarium cobalt is hard to rust even it contains iron. Because the iron element is much lower than NdFeB magnet. AlNiCo and Ferrite magnet are rust proof magnets. So they don’t rust.
5. What coating we can use on neodymium magnet?
Neodymium magnets are often coated with NiCuNi, Zn, black epoxy, and other coatings to protect their surfaces from corrosion and oxidization. You can find more from our Magnet Plating Page.
6. When smco magnets need plating and what to choose?
For normal environment, we can use uncoated smco magnet. But when you use it in sea water, we suggest use coated smco to avoid rust point on the surface. Moreover, the surface of uncoated smco is rather rough. So if you use smco magnet as outer parts, it’s better to plate smco with NiCuNi triple-layer.
We also provide other surface treatment, such as Zinc, silver, copper, chemical nickel, nickel+gold, nickel+tin, epoxy etc.
7. How magnets are graded?
You can find detailed information from our Magnet Grade Page.
8. How long does it take a magnet to lose its power?
Rare earth magnet has high coercive force. That means it doesn’t lose magnetic force and don’t change magnetic property under ordinary circumstances over time.
We assume that the environment is stable (proper temperature & humidity, no strong external magnetic field, no radiation and others), the magnetic force only lose few even after a long time. So in an actual application, we can ignore the influence of time factor on magnetic force.
9. What is important magnet glossary?
- Residual Induction (i.e. Br, measured in gauss) Flux density, of a magnetic material after being fully magnetized in a closed circuit.
- Coercive Force (i.e. Hc, measured in Oersteds) – The demagnetizing force, required to reduce the residual induction, Br, of a fully magnetized magnet to zero.
- Intrinsic Coercive Force (i.e. Hci), – Oersted measurement of the material’s inherent ability to resist self-demagnetization.
- Maximum Energy Product (i.e. BHmax, measured in Gauss-Oersteds) – The maximum product of (BdHd) which can be obtained on the demagnetization curve.
- Gauss – Unit of measure of magnetic induction, B, or flux density in the CGS system.
- Megagauss-oersteds (MGOe) – The stored energy in a magnet, called magnet performance or magnetic energy product, is typically measured in units of megagauss-oersteds.
- Gaussmeter – An instrument used to measure the instantaneous value of magnetic induction, B.
- Maximum Operating Temperature – The maximum temperature of exposure that a magnet can forego without significant long-range instability or structural changes.
10. How do you measure the strength of a magnetic field?
Gauss meters are used to measure the magnetic field density at the surface of the magnet. This is referred to as the surface field and is measured in Gauss (or Tesla).
11. Why we can’t use the surface magnetic field to determine the magnetic properties?
The surface magnetic field is the value on the certain point of magnet surface measured by the gauss meter. The measurement point does not cover the entire magnet surface. In addition, every gauss meter has 2% error. And there are measurement errors in the measurement process, because in the same product, you cannot find two points which are coincide exactly.
Therefore, the surface magnetic force can only be a basic reference; but cannot be used to determine the performance of permanent magnet. Normally, we will use the flux value to determine whether the performance of the magnet is qualified.
12. How to find the north side of a magnet without a compass?
- Use another marked magnet. The North Pole of the marked magnet will be attracted to the South Pole of the unmarked magnet.
- Use a Gauss Meter.
You can find more from our Ways to Determine Polarity of Magnets Page.
13. Why there is a delay in delivery?
Many factors will determine the delivery of permanent magnets, such as magnets’ performance, size, shape and so on. Let us explain in detail:
- The impact of rare earth magnet performance: when use unconventional performance or other less commonly used properties material to make magnet, such as: low coercivity grade SmCo LTC (YXG-22) and hast neodymium magnets, they need to be re-formula, smelting, powder, pressure, sintering and sample processes. And their processing technology is more complex; even when the climate changes, it will also affect the results of magnet production. When there is slight uncontrolled, the magnet performance will not meet the requirements and only have to re-production. However this is just production problem of raw material. There are multi-channel machining processes following.
- Magnet size impact: if magnet is too small, too large or special size, it will increase the difficulty of mechanical processing. Too small magnets are difficult to install and easy to lose. So the scrap rate or loss rate is difficult to estimate. Too large magnets are easier to crack. Therefore, the chances of reproducing of too small and too big magnets are relatively high.
- The impact of magnet shape: irregular shaped magnets, especially with the hole in the middle, will result in collapse or crack phenomenon in the production process because of brittle material or the impact of processing stress. In case of such circumstances, it will delay the deliver.
- There are some other factors, such as special fixture required some magnet products. Under normal circumstances, the fixture needs a trial process.
- In addition, we cannot avoid the impact of processing errors sometimes.
14. How long is delivery time for customized neodymium magnet, ferrite, AlNiCo and SmCo magnets?
As we are manufacturer and all our magnets are customized based on your requirement. So we don’t have stock. Normal lead time for custom magnets is 2-4 Weeks, for custom assembly is 3-5 Weeks. You can contact our salesman for more accurate delivery date.
15. Why rare earth magnet sample can’t be free of charge?
- permanent magnets are custom products. They are not ready made unlike other standard parts. Even for several pieces magnet samples, generally they have to go through a series of mechanical processing. And the processing is complex with more than a dozen processes to complete. Some often need five or six days of process turnaround time.
- These production processes require all production equipments as well. And clamping tools and equipment adjustments are time-consuming too. So there is a lot of waste of resources and it also brings a serious impact on the normal production. If there are chamfering or plating needed to be made, the cost will be even higher. The general chamfer or plating needs ten hours to complete. It’s also a high cost for coating when plating barrel with a few kilograms capacity are installed only ten or dozens of pieces magnets.
- magnet raw material is expensive, especially raw material of rare earth magnet.
- due to the small number of samples, we often use more than 200% material to make sample. Generally, volume production use molds to make more appropriate raw material. However samples have to use unmatched rough material to work. This will waste material and increase several extra processes.
- for above reasons, magnet samples also take a lot of our labor.
- there is a data, after preliminary estimates, indicated the unit price of magnet in a bulk order is only a few cents; however, the sample cost is about USD80-100. The sample cost we charged is very low, far less than our production cost. Sample cost is only for long-term cooperation and hope there is a bulk orders. Meanwhile, it is a reminder for customers to make magnet sample careful and try to avoid unnecessary proofing. Moreover, we will respect each other’s contributions from magnet sample order.
At last, your understanding and support will be highly appreciated.
16. Email is the best way to contact us, why?
- We need comprehensive information so that we can offer the correct price. By email, you can provide detailed information, such as: magnet material, grade, size, pole direction, tolerances, quantity, special requirements and so on.
- Our experienced professionals will calculate magnet price and it needs time, so we cannot blurt out. When you tell us all information about magnets, we are not sure that we receive the correct information, because our memory and pronunciation differences will effect accurate quotation.
- We can save emails as a record and check them when we are still in doubt.