2020 Volume 61 Issue 5 Pages 884-892
Oil quenching is an efficient heat treatment cooling method which can obtain a large cooling capacity by utilizing the boiling phenomenon. However, when the vapor film remains, the cooling speed is reduced only in the part, and the uneven cooling can cause heat treatment distortion, which is the biggest problem in the heat treatment process. In this paper, a quenching experiment was conducted by immersing a horizontal stainless steel disk specimen in quenching oil. Thermocouples which just located below the surface accurately measure the cooling curves of the top and bottom surfaces of the specimen.
In this study, the temperature-dependent heat transfer coefficients were identified from the cooling curves by the inverse method using the analytical solution derived from the Fourier heat conduction equation of the disk.
In addition, a visualization experiment was conducted, in which a laser beam sheet was put into the oil tank of the equipment, and the boiling phenomenon, the formation of a vapor film, and the film boiling phenomenon were observed using a high-speed video camera.
Furthermore, in order to verify the correctness of the heat transfer coefficient obtained by the inverse solution method, the heat transfer coefficient was substituted into the heat treatment simulation software “COSMAP” and the quenching distortion calculation was performed by executing the quenching simulation calculation of the disk. It was proved that the prediction accuracy was improved.
