发蓝工艺制备铁硅软磁粉芯及其磁性能研究

Magnetic Properties of Fe-Si Soft Magnetic Powder Cores Prepared by a Bluing Insulation Method

开发了一种碱性发蓝+氧化硅辅助绝缘工艺,成功制备了性能优于传统磷酸钝化工艺的铁硅软磁粉芯,研究了发蓝液浓度对粉芯微结构和磁性能的影响。研究发现:磁粉表面形成了一层均匀、稳定的绝缘层。低浓度发蓝液的使用有助于提高磁粉的流动性,而大量发蓝膜在铁硅颗粒表面生成后,磁粉的流动性变差,由此导致粉芯密度随着发蓝液浓度的增加呈现先增大再减小的趋势。粉芯密度降低说明内部气隙增大,导致退磁场增强,磁滞增大,造成有效磁导率降低,直流偏置性能增强,磁滞损耗变大。损耗分离研究表明,粉芯损耗在100kHz以下的变化主要由磁滞损耗所决定。

An insulation method,comprising an alkaline bluing coating followed with a silica assisting insulation,was used to prepare the Fe-Si soft magnetic powder cores whose performances were better than that of the powder cores fabricated by the traditional phosphoric acid passivation. The effect of the bluing solution concentration on the microstructure and magnetic properties of the powder core was investigated. It was found that a homogeneous and stable insulation layer formed on the surface of powders. The fluidity of the magnetic powder was improved by insulating with a low concentration bluing solution,but further increase of the bluing solution concentration resulted in the deterioration of the powder fluidity. As a result,the powder core density decreased with the bluing solution concentration after an initial increase. The decrease of the density implied that a large number of air gaps,causing the strengthening of the demagnetization field and the hysteresis and thus resulting in the decrease of the effective permeability and the enhancement of the DC-bias performance,existed in the core. The study on the loss separation indicated that the variation of powder core loss at frequency lower than 100 k Hz was mainly determined by the hysteresis loss.