Preparation And Properties Of Special Powder Cores,

Magnetic powder cores is one of soft magnetic composites, which ismanufactured by the conventional PM process, can be described asferromagnetic powder particles surrounded by an electrical insulating film.Modem analysis techniques including X-ray diffraction analysisanalysis(XRD),scanning electron microscopy(SEM),energy depressiveanalysis(EDA) and thermal analysis were applied in our experiments. Theeffect of process parameters on the permeability, quality factor, DC and ACcharacteristics of Fe₁₇Ni₈₁Mo₂ magnetic powder cores were investigated.In the paper, the influence between the insulation medium concentrationand the quality factor as well as the permeability of cores were investigated.The results show that with the increase of the additive contents of insulation,the permeability decreased, quality factor increased ,the better DC and ACcharacteristics of Fe₁₇Ni₈₁Mo₂ magnetic powder cores are obtained.The formula of permeability of magnetic powder core was deduced. Itcan be found there are close relationship between the density and thepermeability of the magnetic powder core. The higher the density of magneticpowder core is , the higher the permeability of that .Influence of pressingprocesses on magnetic powder core properties are also studied. The results ofthe experiments show that the permeability may increase with the increase offormed pressure and the additive contents of lubricant. The permeability maydecrease with the increase of the additive contents when the contents oflubricant is more than 1.5wt%. In the process of the warm compaction, thepermeability increased with the increase of the compaction temperature. Themaximum permeability can be obtained when the compaction temperature was130℃.Influence of heat treatment on magnetic properties of magnetic powdercore were investigated, the results indicate that the permeability and qualityfactor of the powder cores show different characteristics in differenttemperature stage. From room temperature to 400℃,the magnetic propertiesof powder core vary slowly with the increase of temperature In thetemperature range of 400～600～℃, the magnetic properties may be improvedgreatly with the increase of the annealing temperature. But the quality factordecreased when the annealing temperature is above 600℃. We also find that the permeability of the magnetic core increased with the increase of quenchingcooling rate.At last, the properties of compound magnetic powder cores wereinvestigated. Magnetic powder cores with good characteristic can be obtainedby mixing amorphous Fe_37.5Cu₁Nb₃Si_13.5B₉ and Fe₁₇Ni₈₁Mo₂ powders. Theproperties of compound magnetic powder cores varied with the change of theproportion of two powders.