Preparation Of Magnetic Abrasive By Sintering Method

As a new promising process, magnetic abrasive finishing(MAF) has achieved great development and been widely used due to the low design cost, high finishing efficiency, easy operation, low pollution, low energy consumption, easy automation, etc. As grinding tool, magnetie abrasive is the key of magnetic abrasive finishing, so in the paper we analysed the grinding mechanism of magnetic abrasive particles and based on the work,we brought forward performance requirerment of magnetic abrasive for magnetic abrasive finishing. In the paper, following items on magnetic abrasive were analyzed:grinding pressure, composition, structure, shape and the preparation method of magnetic abrasive, then conventional solid-state sintering method of magnetic abrasive was brought forward.In the paper, based on the traditional sintering method, using high-temperature inorganic binder instead of titanium, molybdenum and other precious metals bonded components, and iron powder surface was coated with SiO2 by Sol-gel method, a series of magnetic abrasive was prepared in the absence of climate protection. Then we studied the effect of sintering temperature, sintering time, suppressing pressure, ratio of raw materials, ferromagnetic phase type, abrasive particle size and sintering atmosphere on properties of magnetic abrasive, then the proper experimental parameters were determined, and in this condition, a series of magnetic abrasive was prepared. Thermal field emission scanning electron microscopy and X-ray energy dispersive spectroscopy were used to characterize the morphology and elemental composition, X-ray diffraction was used to study the phase composition. We also test the performance of magnetic abrasive grinding and analysed the durability. Experimental results indicated that, the magnetic abrasive was mainly composed of a-Fe, Al2O3, Fe2O3, AlFeO3, which were mainly irregular polyhedral particles. All the magnetic abrasive prepared had good polishing ability and long using time, and the surface roughness of the grinding sample can reach 0.12μm and the using time is up to 24 min.In addition, with ferrosilicon powder, corundum powder and high temperature inorganic binder were used as the raw materials, the magnetic abrasive has been prepared. We studied the influence of sintering temperature, sintering time, suppressing pressure on the binding degree of magnetic abrasive, and optical microscope, scanning electron microscopy and energy dispersive X-ray instrument were used to characterize the morphology and elemental composition. Experimental results show that the sintering temperature, sintering time and suppressing pressure are closely related to the binding degree of magnetic abrasive. The higher sintering temperature or the longer sintering time are, the better combination conditions of magnetic abrasive will be. The sintering temperature should be higher than 1200℃, sintering time should be longer than 5 h, to ensure that corundum powder remained high bond strength with ferrosilicon powder. Suppressing pressure is helpful to the combination state of ferrosilicon powder and alumina powder, the greater suppressing pressure is, the better combination conditions will be.