Anomalies in the Relaxation Time of Elastic After Effect on Perlite Steel Compression Coil Springs at A₀ Transformation Point

In this study, we investigate the amount of plastic deformation caused by the settling of a pearlite steel compression spring under constant load heat treatment in various temperatures, and the amount of temporal change of elastic after effect in the treated spring. The relationship between the relaxation time and the heat treatment temperature has been discussed. The relaxation time of elastic after-effect became minimum at A0 transformation point and showed λ transition like abnormality. This decrement in relaxation time indicates that dislocations change its behavior from plasticity to elasticity. It corresponds to the extension of elastic limit in low-temperature annealing. It also suggests that the Curie point of magnetic transition in cementite affects the mechanical property of the spring.