Aplicação de fluido de corte a baixas temperaturas na retificação plana tangencial do aço SAE 52100

Abstract

Grinding using conventional wheels is widely used in metal-mechanic industry due its ability to provide to the workpiece a good finishing and tight tolerances. However, using conventional grinding wheels a great amount of heat generated on the process is conducted into the workpiece and so it is important the correct selection of cutting parameters in order to avoid finishing deterioration and microstructural changes. Among these parameters, the cutting fluid plays an important role since it aims, mostly, to cool the workpiece, minimizing or avoiding dimensional changes and thermal damages caused by high temperatures during the process. In this context, this work presents the results of the investigation of the influence of a conventional cutting fluid cooled below room temperature and then applied during surface grinding of hardened SAE 52100 steel. The cutting fluid employed was vegetable based, applied at three different temperatures: 15 °C, 10 °C and 5 °C. Experimental trials using cutting fluid at room temperature and also dry conditions were done as well, in order to allow comparisons and analyse the cooled cutting fluid performance. The analysed output parameters were the workpiece temperature, surface roughness (Ra, Rz and Rt parameters) and microhardness below the machined surface. Images from ground surface and from microstructure below machined surface were also obtained and analysed after grinding process. The results showed that the depth of cut and the different lubri-cooling conditions did not play significant influence on the roughness values. In addition, it was observed an increase on the workpiece temperature for all cutting conditions, except for those samples machined using cutting fluid at temperatures of 10 °C and 5 °C. Lastly, the microhardness results, and the analyses of both machined surfaces and microstructure of surface layer showed that the application of cooled cutting fluid has drastically reduced the heat affected zone, indicating that this procedure was efficient in terms of preventing microstructural changes caused by heat generation during the grinding process of hardened SAE 52100 steel with conventional Al2O3 grinding wheel.