International Journal of Advanced Engineering Research and Science (IJAERS) [Vol-7, Issue-4, Apr- 2020] https://dx.doi.org/10.22161/ijaers.74.45 ISSN: 2349-6495(P) | 2456-1908(O) www.ijaers.com Page | 360 The influence of heat treatments in the shear force during the machining of the SAE 4320 Steel Brayner Cardoso dos Santos, Thalita Francisco Possão Dantas, Carlos Augusto Cardoso Lima, Gabriella Pinto Valentim, Fernanda Couto Silva Federal Institute of Goiás, School of Engineering, Goiânia, GO, Brazil Abstract— The steel have a wide range of applications in the industry, being of extremely importance in any manufacture process. The SAE 4320 steel is used in a lot of ways, some of them are the transmission systems like gears and pinions. The heat treatments are used to improve some properties of the steel like, hardness, ductility and impact resistance. There are many different types of heat treatment. In this article it was made the tempering process in water and oil, and the quenched process was done in the samples. The purpose of this activity is to do the heat treatments, that were mentioned before, in the SAE 4320 steel, and then analyze with tests the mechanical property variation in the shear force during the machining, with the objective of verifying if there is any correlation between these parameters and if the shear force is also influenced by this modification of the microstructure. Some parameters, like the time that the sample was in the austenitization temperature and the machining parameterswere fixed. After the heating treatments some analysis of the microstructures and hardeningwere made. Keywords— SAE 4320 Steel; Heat Treatment; Hardness; Shear Force. I. INTRODUCTION The study of thermal and thermochemical treatments, as well as mechanical analysis after certain treatments are of great relevance to optimize the machinability of a given material. The SAE 4320 steel, which is widely used in the manufacture of pins, gears and elements requiring high surface hardness, is still of few use in the range of products available on the market. This report has the objective to broaden the knowledge already acquired in relation to steel, contributing to its applicability. Using different thermal treatments it was evaluated how these processes influence the machining of a part made of SAE 4320 steel, allowing the choice of the ideal processes according to the application of the material. The concepts and knowledge developed in the machining of hardened steel are applied to obtain desired surfaces and production in the shortest time possible, eliminating future operations, mainly rectification [1]. The choice of the appropriate tool and application of the cutting parameters can contribute not only to obtaining the specified surfaces but also to the execution of the operations with lower costs [2]. Machining is of fundamental importance to other manufacturing processes, being the most widely used in the industry, turning into chips about 10% of all metal production, employing tens of millions of people worldwide [3]. It also accounts for more than 15% of the total value of processed products, whether mechanical or not. By comparing the machining forces (Fu) of thermally treated samples, it is expected to determine which variables should be used in order to optimize the manufacturing process of parts made of 4320 steel. It is also expected that the work will contribute to the determination of the heat treatment variables of the steel under study, in order to offer results that will show which type of treatment is most suitable for obtaining certain mechanical characteristics such as hardness. Among the main objectives to be taken into account, one highlight is the heat treatment of 4320 steel, as well as the metallographic analysis that evaluates how such treatments can change the machinability of the material. In this way, to see if the results obtained were satisfactory for the applicability of SAE 4320 steel in the