The production process of magnet: isostatic pressing
What I’m going to introduce to you today is the fifth technological process of magnets. What is it? That’s isostatic pressure.
The green density of the magnetic field oriented molding process is about 3.2-3.8g/cm³, and the ideal density of the sintered NdFeB magnet should be 3.2-3.8g/cm³. It is about 7.5g/cm³, so when pressing large columns and blocks, it is easy to crack due to large shrinkage, deformation due to missing angle and size out of tolerance. Therefore, it is necessary to put an isostatic press to improve the density of the green body through isostatic pressing. After isostatic pressing, the density of the green body is 4.5g/cm³（ Other specifications have to go through the isostatic pressing process after directly swinging the box into the sintering furnace. In order to prevent oil immersion and surface oxidation, the isostatic pressing green body must be vacuum sealed and oil stripped before entering the furnace.
The working principle of isostatic press is pascal’s principle. The green body put into the soft mold sleeve is put into the closed super-high claw container, and the hydraulic oil is continuously pressed into the sealed container through the booster pump, so that the hydraulic pressure in the sealed container is continuously increased, and the general use pressure is 100 ~ 630mpa. The high-pressure liquid uniformly acts on the surface of the rubber sleeve and compresses the granulating material in the rubber sleeve to make it shape. Because the characteristic of isostatic pressing is equal pressure in all directions, the density of the blank is uniform, the structure is uniform and isotropic.