Effect of Quenching Parameters on Distortion Phenomena in AISI 4340 Steel

During quenching heat treatment, the formation of high residual stress values and the presence of distortion are phenomena which are difficult to control and accurately predict, their effects being extremely important to the components or pieces of complex and robust geometry that are commonly used in the industry. The latter is mainly due to the mixture of the high temperature levels formed between the surface and the cores of the components and the martensitic transformation during quenching. In this research, an experimental and simulated analysis of the process of the quenching heat treatment of AISI 4340 steel, using geometrically complex components, was undertaken with the objective of studying and understanding the effect of quenching process parameters on distortion, stress generation, and mechanical properties. A model that applied the finite elements method (FEM), in which entry data such as thermo-physical and mechanical properties were obtained through experimental techniques that were reported in the literature, made it possible to simulate the cooling process under different conditions, which helped to explain the origins of the distortion in the quenched parts. The results show a close relationship between various quenching parameters such as heat extraction speed, the immersion orientation in the liquid, and the component’s geometry. The data obtained could contribute to accelerating the design process of the heat processing routes for quenching components by taking into consideration both the classic process variables and, due to the increased precision resulting from mathematical modeling, additional factors such as the geometry of real applications.