Neodymium magnet bubbling phenomenon and how to prevent it

(1) If the blank is molded, the difference of moisture content between the inside and outside of the blank is relatively large, and the magnet simply bubbles. This is as a result of billet initial appearance water transpiration rate than internal water dispersion speed, follow the passage of time, its appearance moisture content drops, blank inside, outside moisture content difference increases, if billet base has the remaining closed water, in the high temperature will bubble. If the blank inside and outside of the moisture content of the difference, gradually reduce, bubbling also gradually reduce.

(2) In the secondary fine grinding, the larger the particle size, the more simple dispersion of inner and outer capillary water, the smaller the bubbling rate of the magnet.

(3) Sintering, below a certain sintering temperature is not bubbling, this temperature is called critical bubbling temperature, beyond this temperature, bubbling rate will progress with the progress of sintering temperature step by step. With the advance of the pre-firing temperature, the critical bubbling temperature also improved.

(4) Another reason for bubbling is that after the pre-sintered material is mixed with iron due to crushing and grinding in the crushing technology to produce Fe2O3, it will be divided in the sintering according to the reaction formula of 6Fe203 =4Fe304 +O22Fe2O3 =4FeO +O2. When this Fe2O3 is reduced to FeO fiercely, the differentiated O2 will also make the blank bubbling if it cannot be discharged.

(5) good ventilation sintering furnace, its magnets are also prone to bubble.