A study on demagnetization heat treatment of waste neodymium iron boron (NdFeB) magnets by using computer simulation

Abstract

In this study, demagnetization heat treatment at 100 ∼400 °C is studied by using computer simulation to secure the optimal demagnetization heat treatment conditions for waste neodymium iron boron (NdFeB) permanent magnets. From the computer simulation, the temperature of the magnet during heat treatment is higher than the set temperature by up to 6 °C. Delay time occurs when the furnace internal temperature and magnet temperature reached the set temperature. A delay time of 15 minutes in an air atmosphere and 10 minutes in a nitrogen atmosphere occurs. The Nd magnet was completely demagnetized at 300 °C as the magnetic flux decreased when the heat treatment temperature increased up to 250 °C. The fully demagnetized magnet could be magnetized to the level of a new magnet. It was confirmed that NdFeB magnets heat treated up to 350 °C in a nitrogen atmosphere can be reusable due to stable demagnetization being possible without surface change.