The sixth process of magnet production: sintering and aging

The density of the green body made of the magnetic powder of the magnet after orientation, molding and isostatic pressing is very low, which is a negative factor in the production. The green body contains more pores, which is easy to absorb a large amount of gas, including water, and brings troubles and difficulties to the next process. At the same time, due to the low density of the green body, sintering shrinkage, easy deformation, easy size, so it must be sintered, and the process of sintering operation experience requirements are relatively high.

The green body is put into the sintering furnace through two processes: sintering and aging.
1> Sintering; holding for a period of time in the highest temperature range, where the most important sintered body density is increased. The relative density has the 0.6 of the green body -0.7 increased to above 0.95. The internal components of each crystal grain are further homogenized. The gap between the particles is reduced, and the adsorbed water vapor is discharged.
2> aging: sintered billet density is high, Br is high, but the coercivity and magnetic energy product is not high. This is due to the fact that the neodymium-rich phase is not yet properly distributed. At the aging temperature, the thin layer of the neodymium-rich phase surrounds the main phase particles and separates them from each other, forming a good organizational structure conducive to high coercivity. After aging, the Br of the billet increased only slightly, while the coercivity increased exponentially.

After the sintering of the blank products need to carry out the following analysis and testing, to ensure that the performance of the magnet standard:
A. Magnetic property detection after high temperature sintering;
B. Density detection after high temperature sintering;
C. Appearance and dimension inspection after high temperature sintering;
D. after high temperature sintering: carbon, oxygen and nitrogen analysis;
Finally, the demagnetization curve is drawn by the magnetic tester to determine whether the blank meets the national standard.

Source: magnet manufacturers Youlian Magnetic Industrywww.youliancy.com