Obtaining a Spherical Magnetic Abrasive by Plasma Spraying into Water

A magnetic abrasive, used for medical capillary tube interior finishing, preventing accumulation of impurities and uneven flow of the transported liquid, is a composite particle consisting of a magnetic base (ferromagnetic powder Fe3O4) and an abrasive Al2О3. Non-uniform shape of the magnetic abrasive caused by the process of mechanical crushing results in abrasive non-uniform cutting depth, leaves scuff marks on the surface and reduces the surface roughness of the processed products. Moreover, non-uniform shape of the magnetic abrasive causes difficulties when introducing it into a capillary tube. Capillary tubes are widely used in medical, electrical and chemical equipment. These tubes must have smooth machined inner surfaces to prevent the accumulation of contaminants and uneven flow of the transported liquid. Internal diameter reduction and length increase of a capillary complicates inner surface machining. To improve the quality of magnetic abrasive machining, this study proposes the production of a spherical magnetic abrasive based on ferromagnetic powder Fe3O4 with Al2О3 abrasive on the surface being applied by plasma spraying into water. The article considers: firstly, the possibility of plasma spraying into water to give the existing magnetic abrasive a more spherical shape and suggests the conditions necessary to obtain a spherical magnetic abrasive; secondly, it studies the creation of a new spherical magnetic abrasive made of individual particles: ferromagnetic powder Fe3O4 and abrasive Al2О3, located on the outer surface of the magnetic abrasive. Quality evaluation of the machined capillary tube surface made of stainless steel SUS304 during experiments shows the applicability for magnetic abrasive finishing. As a result of the study, a method for manufacturing a spherical magnetic abrasive is described, the cutting edges of an Al2О3 abrasive located on the magnetic abrasive outer surface capable of generating a large magnetic force, in comparison with other abrasives obtained by other methods. The resulting spherical magnetic abrasive, whose Al2О3 abrasive particles with an average diameter of 4 microns are located on top of 75 microns of ferromagnetic Fe3O4 powder, has a greater processing efficiency of stainless steel SUS304 capillary tubes in comparison with magnetic abrasives obtained by other methods.