Magnetic field assisted finishing of ceramics--part II: on the thermal aspects of magnetic float polishing (MFP) of ceramic balls

摘要

The thermal model developed in Part I of this three-part series is applied in this paper to magneticfloat polishing (MFP) of ceramic (Si{sub}3N{sub}4) balls. Using this method, the flash temperatures,flash times, and temperature distribution at the interface between the balls and the shaft of the MFPapparatus are calculated. Examination of the polished surfaces (scratch lengths) of the balls showedthat the length of most scratches during the final stage of polishing is <20μm and most are formedunder transient conditions. But because of the small area of contact and low load encountered inMFP,the results of the calculations under these conditions were found to be very close to the quasi-steady-state conditions. However, it is not possible to know a priori if the conditions are transient orquasi-steady state unless solutions are available for each case. The use of the general solutiondeveloped in Part I enables this determination. The minimum flash temperatures and minimum flashtimes that occur during polishing ensure the determination if adequate temperatures are generated forchemo-mechanical polishing to take place. Of course, the lengths of the scratches would be muchlonger and the corresponding flash duration longer during the semifinishing operation than duringfinishing. The combined temperature and flash duration would determine the extent of chemo-mechanical action under these conditions. The flash temperatures and flash times required forchemo-mechanical action can be used as a basis for the optimization of polishing conditions in MFP.