Estudo da temperatura em ferramentas de usinagem com canais de refrigeração internos no torneamento do ferro fundido cinzento

Abstract

Machining is a productive process that involves friction between two materials, with a high strain rate, in which most of the mechanical energy is converted into heat, mainly concentrated in small areas at the tool/chip interface where the highest temperatures are normally found. In the part, the higher temperature favors the reduction of cutting efforts due to the reduction of material resistance. It has an adverse effect on the tool, as it accelerates wear mechanisms, compromising its useful life. Furthermore, it harms the surface integrity of the part, the dimensional tolerances, and consequently the productivity of the process. The standard technique for temperature control in the metalworking industry is the application of Abundant Cutting Fluids – FCA. The main functions of FCAs are cooling, lubrication, chip removal and corrosion protection. These inputs effectively improve tool life, in addition to producing better dimensional control and surface quality. However, FCAs have disadvantages in relation to the sustainability tripod: social, environmental and economic. Environmentally, if not properly disposed of, they can impact soil, sewage, groundwater, rivers, springs, etc. Socially, they are toxic and can cause operators allergic skin problems, respiratory problems or even cancer. Finally, economically they represent a considerable portion of the production cost. This work presents a thermal study of a cooling technique for machining from tools and tool holders designed with internal cooling channels, through which chilled water circulates in a closed cycle. Therefore, this work aimed to study the effect that this cooling technique in machining with internally cooled tools has on machining temperatures. This proposal can be considered ecologically less harmful as it does not require the use of cutting fluids. To analyze the behavior of the system, gray cast iron was turned with carbide tools. The response variable was the temperatures generated during cutting, measured by the tool-work thermocouple and welded thermocouple methods. The input parameters were the cutting speed (84, 132 and 212 m/min) and the ambient conditions (common insert, modified insert circulating water at enviroment temperature and modified insert circulating chilled water), both controlled in three levels. The main conclusion found was that the cooling system proved to be efficient with temperature differences of up to 21.52% compared to a dry machining process and also showed to have a significant impact on the thermal gradient formed during the cutting process.