Special features of the magnetic abrasive machining

Abstract

It is shown, using electron microscopy, magnetic and friction methods, that a mixture of magnetic g-Fe 2 O 3 and abrasive powders, properly processed, can be used as a material for magnetoabrasive machining and polishing of variously shaped components.In recent years, a great deal of attention in mechanical engineering has been focused on finishing operations aimed at tightening the finishing tolerance of machined components; in this connection, there has been increased interest in the use of the magnetic abrasive machining (MAM) method. In the MAM method, a magnetic field is used to generate cutting and polishing forces to treat the surface of a machined part. The magnetic field behaves as an elastic bond for the abrasive ferromagnetic grains and allows more effective use of the abrasive's cutting edges; furthermore, it provides conditions for a small cutting force and a low surface temperature for finishing operations.The MAM method offers a number of advantages over the conventional techniques of abrasive treatment [1, 2]: (i) abrasive grains are spread uniformly over the treated surface, which allows effective finishing of complex-shaped components; (ii) the abrasive grains do not suffer from overloading; (iii) instantaneous temperature spikes can be readily avoided; (iv) the cutting temperature can be lowered to 473 K; (v) selective polishing is possible on ferromagnetic materials in which surface asperities (magnetic field concentrators) are cut off; (vi) the force (typically up to 1 MPa) at which the abrasive grains act on the surface treated promotes the formation of a new high-disperse phase and converts the tensile stresses into compressive.The readjustment of machine-tool equipment for handling components of different size and shape by the MAM method is not usually an easy task, and for this reason the use of MAM techniques is cost-effective either on large-scale production, or for solving special technological problems.The MAM machine tools can be classified with regard for the arrangement of magnetic poles: for cylinder-shaped components, for flat-surface components, and for small-size complex-shaped components; schematically, this is shown in Fig. 1 [3 , 4]. Magnetic abrasive (MA) materials with particles of different shape can be used; schematically, this is shown in Fig. 2.A general-purpose MA powder which would be equally good for roughing, cutting and polishing operations is yet to be developed. The conventional methods for preparation of adhesive powders are purpose-oriented and the powders pre-

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