Demagnetization of iron-neodymium-boron type permanent magnets without loss of coercivity
AssigneeGeneral Motors Corporation
InventorViswanathan Panchanathan
Life of this patent
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Abstract
Hot worked, fine grain, permanent magnets of the iron-neodymium-boron type can be demagnetized by heating in air for a period of minutes at a temperature in the range of 100.degree. C. to 300.degree. C. above their Curie temperature without significant loss of coercivity.
Claims3
A method of demagnetizing a permanent magnet so as to minimize loss of coercivity, the permanent magnet comprising fine grains of the tetragonal crystal phase of RE.sub.2 TM.sub.14 B composition where RE is neodymium and/or praseodymium or mixtures of them with lesser quantities of other rare earth elements and TM is iron and mixtures of iron and cobalt, the method comprising
- heating the magnet at a temperature in the range of 100.degree. C. to 300.degree. C. above its Curie temperature to demagnetize the magnet such that upon cooling to normal room temperature the magnet possesses a coercivity no less than the coercivity prior to demagnetization.
A method of demagnetizing a hot worked, anisotropic permanent magnet so as to minimize loss of coercivity, the permanent magnet comprising fine grains of the tetragonal crystal phase of RE.sub.2 TM.sub.14 B composition where RE is neodymium and/or praseodymium or mixtures of them with lesser quantities of other rare earth elements and TM is iron and mixtures of iron and cobalt, the method comprising
- heating the magnet in air at a temperature in the range of 100.degree. C. to 300.degree. C. above its Curie temperature to demagnetize the magnet such that upon cooling to normal room temperature the magnet possesses a coercivity no less than the coercivity prior to demagnetization.
A method of demagnetizing a hot worked, anisotropic permanent magnet so as to minimize loss of coercivity, the permanent magnet comprising fine grains of the tetragonal crystal phase of RE.sub.2 TM.sub.14 B composition where RE is neodymium and/or praseodymium or mixtures of them with lesser quantities of other rare earth elements and TM is iron and mixtures of iron and cobalt, the method comprising
- heating the magnet in air for a period up to thirty minutes at a temperature in the range of 175.degree. C. to 250.degree. C. above its Curie temperature to demagnetize the magnet such that upon cooling to normal room temperature the magnet possesses a coercivity no less than the coercivity prior to demagnetization.
Dependencies are inferred from the claim text.