Temperature and Neodymium Magnet
What is the maximum allowable temperature of the neodymium magnet? What if the magnet exceeds this temperature? How to read the demagnetization curve? Temperature problems and neodymium magnets can be a complex issue. In today's topic article, we'll try to simplify some of these concepts and answer some common questions.
In the previous article, we listed two key temperatures: the highest operating temperature and the Curie temperature.
The Curie temperature is the temperature at which all magnetization of the magnet is lost.
The maximum operating temperature (hereinafter referred to as MaxOpTemp) is a general number given for each different grade of magnet material. Although not entirely correct, this is a good guide for many situations. Between the MaxOpTemp and the Curie temperature, a certain proportion of magnetization is irreversibly lost.
Some definitions:
Magnetic strength: In this paper, magnetic strength is a key indicator. The product of B multiplied by H is usually used to describe the strength of the neodymium magnet. We specify the Gaussian surface field measured on the surface of the magnet. The magnetic strength is not power, nor power, and cannot be expressed in terms of power.
Reversible loss: Until MaxOpTemp, at these high temperatures, you will see some loss of magnetic strength. After returning the magnet to room temperature, it will return to its original strength. These losses are small, usually within 5% to 10%.
Irreversible loss: Some magnetization is lost above MaxOpTemp. When you return the magnet to room temperature, it will be weaker than before heating. Magnets with irreversible losses can theoretically be re-magnetized to their original strength, or very close to the original intensity.
Permanent Loss: Structural changes occur above the temperature at which the magnet material is initially sintered, permanently demagnetizing the magnet. The externally applied magnetic field does not restore the strength of the magnet. For neodymium magnets, this temperature is very high, typically above 900 °C to 1000 °C.
How much power will I lose at a given temperature?
We must study more in depth to answer this question. Let's start by a better estimate of MaxOpTemp. The MaxOpTemp for a given magnet depends largely on how it is used "online." For a magnet in free space, this means that it depends on the shape of the magnet.
A measure of this shape is called the permeability coefficient. Sometimes referred to as BH, work slope or load line. You can use our magnet calculator to find the permeability of any size/shape of neodymium magnets in free space. Generally, the number of high and narrow magnets is large, while the number of thin and wide magnets is small.