The Process, Histology And Magnetic Properties Of Rapidly Quenching Bonded Permanent-magnets

Since NdFeB permanent magnets have been appeared in 1983, they have become the most important material in the family of permanent magnets and have been paid much attention to throughout the world because of the remarkable magnetic properties. Bonded NdFeB permanent magnets have been used very widely, but there are still some problems. In the paper, a lot of experiments have been done in order to improve the magnetic properties.Two kinds of magnets have been made by MQ and SQP-A+ powder through single pressing in the paper. Effect of particle size and shape of magnetic powders, pressure force, warm-pressing process, sample dimension and uniform coated on magnetic properties have been studied by magnetic measuring apparatus, metallographic microscope and laser-particle measuring apparatus. The factors in process of moulding and measuring magnetic properties have also been studied. The best properties obtained by lots of experiments were that Br reaches 0.719T, Hcj reaches 1052 kA/m and (BH)max reaches 83.6kJ/m3.The results show that the particle size and shape of magnetic powder decide filling process, and flake MQ powder can make better properties. Heating up and compression simultaneously obtained better magnetic properties than compression after heating up. Mix round in time after adding addition agent can obtain uniform coated powder and improve the magnetic properties.Secondly, Magnetic properties under 800MP increase quickly when the well time extend; when the pressure reach 1200MP, dwell time make no difference on Magnetic properties. The best dwell time is 120s.Finally, the dimensional accuracy should be considered in the moulding process; The speed of measuring magnetic property should be controlled, it cann't be too quick, the best speed is between 60s～80s.