Análise das forças e do desgaste de flanco em ferramentas de metal duro modificadas no torneamento do aço ABNT 1045

Abstract

Working with high material removal rates in machining, usually corresponds to less time of production and economic gains. However, an increase in energy consumption or a premature tool wear may affect this relationship. Knowing the amount of heat generated during cutting of the material and its consequent flow, it is essential to control the phenomena involved during turning. Changing the heat flow of the tool is an alternative to increase service life. For this, geometric modifications can be introduced, for example, microtextures in the rake face or in flank face. In this scenario, we studied the behavior of a cemented carbide insert coated with a layer composed of TiN, TiCN and Al2O3 with the modified flank face, turning steel with hardness 1045 ABNT 83HRB. A project to change the insert was developed, which was considered the creation of a geometry that physically limit the maximum length of the flank wear and notch, and it was easy repeatability and low cost. The steel was turned on cutting speed 350 m / min and depth of cut of 1 and 2.5 mm. The force values were collected during the tests, in addition to assessing the chip microhardness and monitoring the evolution of flank, crater and notch wear. The surface integrity was analyzed with microhardness profiles and roughness measurement. Considering that the presence of notch wear in the machining of carbon steel is not common, a analysis was carried out, which indicated that the wear formation was related to the variation in the heat flow in the tool, from the friction of the chip with the flank face and their propagation related to the oxidation mechanism. The modification proved to be highly efficient in energy consumption, reducing the resulting machining force in 58% compared to conventional insert. The reduction in cutting force component and reached 70%. Regarding the surface integrity, the modification promoted a decrease of the hardness after the machined surface in 16%, and the surface roughness worsened going from 1.36 Ra to 1.78 Ra. The same wear mechanisms present in the normal insert were detected in the modified one, and acted in the same proportion, but evidence showed that the modification raised the temperatures even further during machining, which limited the increase in the forces related to wear.