Dependence of the Cutting and Polishing Ability of Magnetic-Abrasive Powders on the Form and Structure of the Particles

Abstract

It is shown that fragmented particles are preferable to spherical particles for magnetic-abrasive finishing. The cutting elements of such powders are microscopic projections that determine the roughness of the finished surfaces. For a given volume of magnetic-abrasive powder, a decrease in the diameter of the particles increases the number of cutting centers. To maximize metal removal over the duration of the polishing operation and shorten the amount of time needed to reach the minimum value of Ra, it is necessary to use progressively finer abrasive powders as Ra decreases during polishing.Composite magnetic-abrasive materials (MAMs) ensure the maximum removal of material from the workpiece in magnetic-abrasive finishing (MAF) conducted with particles of different sizes. MAM performance depends on the conditions which exist during MAF, the dimensions of the working gaps, and the strength of the magnetic field. The shape of the grains of magnetic-abrasive powders has a significant effect on their cutting and polishing ability and a substantial effect on their service conditions.Inside the working gap of the MAF machine, Iron-based magnetic-abrasive particles -which exhibit shape anisotropy -are oriented in such a way that their major axis is parallel to the lines of force of the magnetic field and is perpendicular to the surface of the workpiece. The surface is finished by microscopic projections on the particles [1]. In addition to the magnetic forces, a magnetic-abrasive particle pressed against the surface being finished is acted upon by a frictional force that causes the motion of the particle to deviate in the direction of motion of that surface.Here, the cutting angle becomes negative and increases in absolute value, which adversely affects cutting conditions [2]. Studies of alsifer powders of spherical and fragmented form have shown (Table 1) that a fragmented shape offers more advantages than a sphere [3].Powders obtained by the same method were used for our investigation. Having a material of the same initial composition and performing simultaneous nitriding made it possible to obtain composite powders with granules having different geometries on the macroscopic scale but similar parameters (hardness, dispersity, dimensions) for the particles of the abrasive component -nitrides of silicon and aluminum, silicon carbide (green). The structural parameters of the granules were also similar, particularly the density of the distribution of the abrasive particles over the surface of the granules.Tests were performed on powders with a granularity of 200/160. The spherical and fragmented powders therefore

The dependence of the performance of the process of finishing vibration processing on the shape of the abrasive tool (granules)

“…The shape of the abrasive granule, according to experimental studies, affects not only the performance of abrasive granules, but also on their mobility in the vibration field [14]. Studies have shown that the circulating velocity of the medium consisting of granules of various shapes changes on average by 25-30% compared with traditional cones.…”