各向异性轧制成型高摩尔比铁氧体磁粉工艺研究

生产各向异性轧制磁体用铁氧体磁粉,通常采用的氧化铁Fe_2O_3与氧化锶SrO的摩尔比低于铁氧体摩尔比理论值6.0。由于碱性环境下容易生成Cr~(6+),需通过回火后湿式表面处理工序去除Cr~(6+)。通过调整预烧工艺参数,考察摩尔比在5.65~6.5时磁粉中的Cr~(6+)含量,并探究省去表面处理工序的可能性。研究发现摩尔比大于6.2时,Cr~(6+)含量10 ppm。摩尔比在5.9~6.3时,磁粉剩磁257 m T,内禀矫顽力=270 k A/m。通过调整预烧和添加剂比例,在摩尔比为6.2、添加剂含量3%、1100℃预烧条件下获得磁体剩磁达264 m T的性能。通过对预烧温度对比,在1040~1120℃随预烧温度提高,剩磁逐渐提高,之后继续提高,剩磁逐渐降低。

Study on the preparing technology of ferrite powder for rolled anisotropic magnet with high molar ratio

The production of ferrite magnetic powder for anisotropic rolled magnet generally uses molar ratio of iron oxide Fe2O3 to strontium oxide SrO of lower than theoretical value of 6.0. Because of the easy generation of Cr6+ in the alkaline environment, it is necessary to remove the Cr6+by wet surface treatment process after tempering. This paper focuses on adjusting the pre-sintering process parameters, investigating the effects of the molar ratio in the range of 5.65 to 6.5 on the concentration of Cr6+, and exploring the possibility of eliminating the surface treatment process. The experimental result shows that the concentration of Cr6+ is less than 10 ppm when the molar ratio is higher than 6.2. The remanence is higher than 257 mT and the intrinsic coercivity equals to 270 kA/m when the molar ratio is between 5.9 and 6.3. By adjusting the pre-sintering condition and the amount of additives, the remanence value reaches a maximum of 264 mT in a molar ratio of 6.2 when the proportion of additive is 3 % and the pre-sintering is 1100℃; for pre-sintering of 1120℃, the optimum remanence value is obtained.