Effect of Cooling System on the Mechanical Properties and Residual Stress of Steel AISI 1045 in Quenching Heat Treatment

Quenching heat treatment is one of the most used processes in the industry, which has a great influence on the properties of materials. Accurate understanding of the effects of this process on the behavior of materials can be effective in better use of this process. In this research, the effect of quenching media on the mechanical behavior of wide used steel of AISI 1045 has been investigated and the residual stress created in the structure has been studied using the contour method. In this regard, three cooling environments of water, oil, and molten salt have been utilized, and after examining the strength and contour of hardness resulted by each cooling environment, the residual stresses have been investigated by the contour method. Also, the uncertainty of residual stresses in the environment with the most influencing factor has been evaluated. Investigation of the results shows that quenching in water can create higher hardness and strength, and more excessive compressive residual stress with greater penetration depth than the other environments. But cooling media of water creates more heterogeneous of the structure between the surface and the center of the piece, while quenching in a molten salt environment, with maintaining a structural homogeneity close to the annealing state, can increase the hardness and strength, and generate compressive residual stresses with a penetration depth of about 1.3 mm. Investigation of uncertainty for quenching in the water environment showed that the greatest error in the residual stresses was about 9%, and the error resulting from data smoothing had the most effect on the measurement of residual stresses by the cantor method.