Análise da Integridade da superfície do aço rápido após a retificação plana

Abstract

High Speed Steel (HSS) is commonly used in cutting tools application, such as milling cutters, taps and bits. Therefore, all these tools are subjected to the grinding process in one of the final stages of cutting tool manufacture. During the abrasive machining process, high temperatures are reached, especially when using conventional abrasive grinding wheels, which combined with some peculiarities, such as low thermal conductivity of grinding wheels, low depth of cut values and small chip dimensions, transfers most of the heat to the workpiece. HSS is still very susceptible to thermic damage, such as burns (surface oxidation), hardness decreasing and cracks, among others, that can compromise the workpiece function (in this case the future cutting tool). In order to avoid these damages, it is important to find the correct combination between cutting and process parameters, especially for the grinding wheel and the cooling system. In this work is aimed to determine appropriated parameters for grinding HSS by analyzing 3 depth of cut depths (ae) (10 µm, 25 µm and 50 µm) and 2 workspeed (vw) (2.5 m/min and 7.5 m/min). Roughness (Ra and Rz), Scanning Electron Microscopy (SEM) images, microhardness and microstructure underneath the ground surface were used to access the surface integrity of workpieces. Results show that the best surface finishing was obtained after grinding with the highest value of ae (50 µm) and lowest value of vw (2.5 m/min). The greatest microhardness and microstructure variations occurred when the highest depth of cut value was used; workspeed was not very influential for these output variables.