| Magnetic powder core is a kind of important magnetic functional materials,which has wide application in motor areas. Based on micro-motor for application target and in view of problems of the present magnetic powder core's development, magnetic powder core is manufactured by conventional PM process. Modern analysis techniques including X-ray diffraction analysis(XRD),scanning electron microscopy (SEM),and thermal analysis were applied in our studies. The properties are installed through the experimental test. The effect of powder morphology,particles size and distribution on the preparation and properties, the molding and heat treatment on material mechanic and magnetic performance, the binders on insulation and material comprehensive performance are discussed in this study.Special requirements are needed to powder morphology and size. The effect of ball milling on powder morphology and particle size and distribution is very important. The results show that, different powder particle size and morphology can be leaded to different ball milling process. Flaky powders can be obtained by rotating speed as 350 r/min,ball to powder weight ratio as 10:1, milling time as 4h,the medium particle size is milled as 100μm, which are suitable for preparation of magnetic powder cores. At the same time, powder surface is coated by an insulated film. In ball milling process, powder crystal shape neither changes, nor composition exhalation. The insulated film can improve heat resistant,but when the temperature rises to 474.51℃, organic membrane wrapped in the powder surface decomposes, which can provide the basis to choice of heat treatment temperature.To improve the density, pressure needs to be larger. With the increase of pressure, magnetic powder core's mechanic performance first increase, then decrease.The density is reached to 6.8g/cm3 as pressed as 1200MPa, and the mechanic properties are better. When the pressure is less than 1000MPa, with the increase of pressure, magnetic properties of magnetic cores are improved;and when the pressure within 1000-1200MPa, magnetic properties are better, and not volatility. Magnetic properties of magnetic cores are the best at the pressure of 1000 MPa.So the properties of magnetic cores are the best at the pressure of 1200 MPa.The effect of heat treatment on powder cores properties is discussed. The results show that, for H2 atmosphere,magnetic powder core's mechanic performance is qualified as heating rate for 100-140℃/h;and magnetic performance is better as heating rate for 140℃/h. The performance is better as temperature for 550℃(H2). The mechanic performance is better as holding time for 40 min;and magnetic performance is better as holding time for 60 min;compared to heating rate, the holding time is the less sensitive factor to magnetic powder core's performance. So magnetic powder core's performance is better as heating rate for 140℃/h, temperature for 550℃, holding time for 60 min (H2).The impact of binder selection, amount and composition on powder core's performance is very important. Phenolic resin and nano powders are selected as binders in this study, which can optimize the coated film, and nano powders modified phenolic resin, which can greatly improve its resistance,advance its heat treatment temperature, then improve the performance of magnetic powder core. With the increase of the content of binders, magnetic powder core's mechanic and magnetic performance first increase, then decrease. Magnetic powder core's mechanic performance is better as inorganic nanometer and henolic resins mass ratio as 3:2-3:1,binder amount of 2.7%-3.6%. Magnetic powder core's magnetic performance is better as inorganic nanometer and henolic resins mass ratio as 2:1,binder amount of 2.8%-3.5%. So magnetic powder core's performance is better as inorganic nanometer and henolic resins mass ratio as 2:1,binder amount of 2.8%-3.5%. |
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