Put the iron sheet on the fire and put the magnet on it at the same time. If the temperature of ferrite reaches 600 degrees, it will gradually lose its magnetic force. The N series of Nd-Fe-B will gradually lose its magnetic force when it exceeds 80 degrees. (Note: up to now, the best temperature resistance of strong magnetic field is 350 degrees.) Take ferrite magnet and NdFeB magnet for example.

The magnet will definitely be burned and melted in the fire, because the magnet also has a melting point and even burns, but the melting point and ignition point are very high. (magnets are ceramic or alloy, ferrite magnets are ceramic products, and samarium cobalt, aluminum nickel cobalt and other cast magnets are alloy.)

High temperature will change the molecular structure inside the magnet. After high temperature magnet, the magnetism will be weakened or even completely non-magnetic. This is invisible to the naked eye. Of course, if you just flash on the flame, the temperature does not change widely. (in terms of maintaining magnetism, generally, magnets with temperature below 80 ° can bear it. The temperature resistance of magnets of different materials is different, ranging from 80 to 400 degrees.)

When the temperature of magnet and magnet rises, the molecular motion is strong when heated, and the amount of charge is more than before. Therefore, the magnetism becomes stronger, the molecular motion intensifies, which disturbs the original regular molecular structure, and the internal molecular thermal motion is faster and faster. As a result, more and more electrons refuse to obey the "command" of the "queue". In fact, after cooling, the magnet can restore part of its magnetic force.

When the temperature rises to a certain value, the violent molecular thermal movement finally completely destroys the regularity of the direction of electron movement, and the magnetism of the magnet disappears. Metallurgists call the temperature at which magnets and magnets completely disappear magnetism "Curie temperature". The Curie temperature of steel is 770 ℃.

Some of the design needs have been basically restored, such as the magnetic steel in the middle of the rice cooker. The method of degaussing is to add an alternating strong magnetic field to the original magnetic object and slowly reduce it to zero. This method is used in the degaussing coil of tape and TV in real life.