熱分解性バインダーを用いた異方性磁性粉末の磁場成形

概要

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Ferromagnetic strontium ferrite powders are mixed and then kneaded with pyrolytic binder which is made of ethylene vinyl acetate, acrylic polymer, paraffin wax and stearic acid for metal injection molding. The kneaded compacts are formed in a magnetic field at temperature ranging from 100°C to 165°C. After orientation of the magnetic powders by the magnetic forming, the pyrolytic binder is eliminated by heating up to 600°C and then the compacts are sintered at 1200°C. Effects of the processing factors such as magnetic field strength, forming temperature, relationship between applied direction of the magnetic field and forming direction are investigated on magnetic characteristics of the compacts. The results obtained are as follows:<BR>(1) Residual flux density of the sintered compacts reaches 4400G., which corresponds to 94.6% of theoretical one.<BR>(2) The forming temperature is proper above 135°C, and the effect of the pyrolytic binder is not exhibited below this temperature. This temperature corresponds approximately to flow value of 0.02m1/s in kneaded compacts.<BR>(3) Magnetic characteristics of the sintered compacts made by pressing parallel to the magnetic field is superior to that made by pressing normal to the magnetic field.<BR>(4) Maximum shrinkage of the sintered compacts occurs in the direction of the application of the magnetic field and is unaffected by the pressing direction.