Stress and Distortion of 100Cr6 Steel after Quenching in Aqueous 4% Polyvinylpyrrolidone Solution

The stress and distortion that remain in steel products after quenching are harmful and undesirable. Therefore, a selected quenching medium should have a cooling rate equal to or greater than the critical cooling rate of the steel to achieve high hardness values, but the cooling rate should not be too large in order to minimize stress and distortion on the specimen. This paper studied the hardness, stress and distortion of C-ring samples quenched in 4% polyvinylpyrrolidone (PVP)-K60 solution and oil using simulated and experimental measurements. The results show that the maximum cooling rates (CR_max) of oil and 4% PVP-K60 quenchants are both higher than the critical cooling rate of steel. The CR_max of the 4% PVP-K60 solution is greater than that of the oil, and the cooling rate of the 4% PVP-K60 solution at 300 °C (CR₃₀₀) is smaller than that of the oil. The greater the CR₃₀₀ is, the greater the hardness, stress and distortion are. Thus, the hardness, stress and distortion values of the quenched sample depend less on CR_max and more on CR_300. The research results also showed that a solution of 4% PVP-K60 could replace oil in the quenching of 100Cr6 steel. Simulated and experimental results of the hardness, stress and distortion of C-ring samples reflected the same rule. The errors between the simulation and experiment using the program and the computational conditions of distortion are approximately 20%. The numerical simulation method is entirely usable to predict the hardness, stress and distortion of a sample during the quenching process.