Rectification is used in precision processes, is an expensive technique, and is only used when really necessary. For a good surface finish cutting speeds should be high, this factor coupled with lots of sharp edges makes this machining process occurs at high temperatures. With this the probability of burning the surface material is high, the excess thermal energy transferred to the workpiece directly affects the surface quality, inducing thermal defects such as residual stresses, phase changes, micro-cracks, among others. To avoid losing part by burning it is used some method of lubrication and cooling, which aims to reduce the process temperature by removing heat directly and lubricating the area between the workpiece and the tool to reduce friction and thus lower the heat generated in the process. Despite the benefits of the piece that the cutting fluid provides, there is a growing demand for trying to decrease its use in the manufacture of products, because the cutting fluid has substances that harm the environment and people. This increasing search for an efficient method and less offending to the environment and people did the Minimum Quantity Lubricant (MQL), which consists of applying a mixture of cutting fluid directed with compressed air directly into the cutting area. This method has a deficiency in its cooling, in this work an alternative to increasing the MQL coolant effect by adding water to the cutting fluid will be studied. The specimen consists of steel AISI 4340 hardened and tempered, the average steel combines strength with high resistance to fatigue, so it is of great use in parts and assemblies that are subjected to high loads and periodicals such as axles, crankshafts, and gears. In this study will be used CBN grinding wheel is composed of synthetic abrasive grains that have very high hardness, being exceeded only by diamond. The results should be made by evaluating the output variables of the grinding process, such as the tangential force behavior of cut, roughness, acoustic emission, G ratio (volume of material removed/volume of a worn grinding wheel), optical microscopy, roundness, and microhardness.
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