Análise de superfícies fresadas por diferentes estratégias em aço AISI H13 endurecido

Abstract

In the final milling process of free form surfaces, commonly employed in the production of molds and dies, the knowledge of the cutting conditions and a strategy for choosing adequate processing routes in the milling of hardened materials can provide superior surface quality and dimensional control and a significant reduction in the manufacturing times and costs. The objective of this work is to understand the texture formation in the milling of hardened materials, through the quantitative and qualitative evaluation of the surface roughness, as well as the formation and the regularity of the surfaces. The tool used in these experiments was an interchangeable insert tungsten carbide, ball nose end mill. AISI H13 steel with a final hardness of 54 HRC was used throughout the experimental work. The workpiece was fixed on a device with an inclination of 60 degrees. The same cutting conditions were used for all the tests and four cutting strategies were considered, as defined by the trajectory of the tool, upward and downward, in the horizontal and vertical directions. To characterize the machined surfaces, the roughness was measured and other different methods for the visualization of the surface texture were employed, such as, the optical microscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was possible to observe, through the values of roughness and the topographic images of the machined areas, that the resulting textures clearly show the influence of the cutting strategy employ, distinctly characterized. The textures analyzed show a consistent and repetitive pattern, except the vertical upward strategy (VS) that resulted in an irregular and undefined texture, where the tool marks are unclear. For this condition the presence of plastically deformed material and acceded were observed in the machined surface, with presented the highest roughness value. The lowest roughness values were measured for the downward vertical strategy (VD).