How fast do magnets lose magnetism at high temperatures?

When a magnet encounters a high temperature that exceeds its bearing capacity, it will immediately lose some magnetism. How much high temperature is required? This depends on the coercivity of the magnet, which is usually represented by the letter after the magnet brand. For example, n40h, the maximum magnetic energy product is 40, and H represents temperature resistance 120c. The higher the coercivity, the less likely it is to lose magnetism (demagnetization), and the more dysprosium is added to the magnet.

How much magnetism will it lose?

It depends on the degree of magnetic protection. If there is some iron around it, it will help. Of course, it depends on the temperature, but it is a highly nonlinear effect. It does not begin to lose its magnetism until it reaches a certain temperature, and then quickly loses all its magnetism. Note that the amount of magnetism it loses depends on how high the temperature is, not the length of time at a particular temperature. When the magnet reaches a certain temperature, it will lose all the magnetism it can achieve at that temperature.

How long will it take to lose magnetism?

For some small magnets, they will be demagnetized immediately. However, even for small magnets, it takes time for heat to transfer from the outer surface to the center. For example, a 1 cm3 part takes several minutes. However, some magnets near the surface will lose performance immediately. 200 °, whether Fahrenheit or Celsius, is very high for magnets. Unless you have a special magnet with higher temperature resistance (uh or ah or better), you will completely destroy it.

Introduction of coercivity of NdFeB magnets of various grades;

Class n neodymium magnet: low coercivity

Class m neodymium magnet: medium coercivity

Class H neodymium magnet: high coercivity

SH neodymium magnet: ultra high coercivity

Uh grade neodymium magnet: ultra high coercivity

EH neodymium magnet: extremely high coercivity

From n to eh, the temperature resistance will be higher and the cost will be higher. Other high temperature resistant magnets include samarium cobalt, ferrite, aluminum nickel cobalt and so on.