Influência do processo de polimento com mídias abrasivas em fresas de metal duro na usinagem do aço AISI P20

Abstract

In machining, the condition of the tool cutting edges has a high influence on the results obtained from the process, knowing that after manufacturing the wedge the cutting edge may present defects. As a result, this work studied the effect of cutting edge treatment performed by the brushing process with abrasive sponges in straight top carbide milling cutters, because this treatment is an alternative that can prepare the edge, reducing or eliminating defects, strengthening it and increasing the tool life. The treatments of the milling cutters were performed through the brushing process used by the machining group (GUS) of the University of Caxias do Sul (UCS), which occurred with rigid abrasive sponge discs. To evaluate the brushing results, the milling cutter edges were analyzed qualitatively by images obtained by optical microscopy and quantitatively by roughness easurements performed in the flank region, near the main edge. After the analysis of the cutting edges, two of the three brushed cutters were tested in machining in AISI P20 steel. During the tests, pauses were performed to verify the types of wear that occurred and the wear mechanisms causing them, in addition to measuring the flank wear (VBmax) of each cutting edge. This procedure was performed until the wear reached the predetermined end of life of VBmax = 0.2 mm. The quality of the surfaces generated by the milling cutters were also evaluated, for these analysis surface texture images and roughness measurements were performed. The variables evaluated by the milling cutters polished by rigid sponges, on the polished edges and of the machining tests performed, were also evaluated in cutters polished by flexible sponges and in cutters without treatment, aiming to compare the 3 different cutting edge conditions. The cutters brushed with rigid sponge had a lifespan 21.63 % shorter than the cutters without treatment, while the cutters brushed with flexible sponges returned a 6.92 % shorter service life. However, the cutters brushed with rigid sponge had the lowest occurrence of micro chipping, while the cutters without treatment had the highest occurrence. The lowest roughness values measured were those of the surfaces generated by the tools brushed with flexible sponge and there were no significant differences between the values measured on the surfaces generated by the tools brushed with rigid sponges and by the untreated tools. The textures of the surfaces generated by the tools brushed with rigid sponge, for the beginning of life, did not clearly present the groove marks generated by the passage of the tool, since the other conditions did not present significant differences between them. However, it is important to highlight that the results presented on this study for the machining tests, are only valid for the cutting conditions applied here, any change on these conditions would probably generate different results. [resumo fornecido pelo autor]