A₀変態点近傍で熱処理されたパーライト鋼線を用いた引張コイルばねに見られるばね定数の不安定性

抄録

In this study, we evaluated spring constants of pearlitic steel tension coil springs heat-treated at various temperatures. We measured the spring constants quasi-statically at room temperature or dynamically at elevated temperature multiple times. We found that the spring constant gradually increased with the heat treatment temperature above A₀ transformation point. In addition, it exhibited unstable behavior with rapid increases and recovery in the sample heat-treated near the A₀ transformation point. These experimental results suggested that the 2nd order magnetic transition at the A₀ transformation point may have some effect on the spring constant. These phenomena can be explained by the decrease in the pinning width of dislocations on the ferrite phase {110} slip plane oriented in the longitudinal direction of the steel wire caused by gradual recovery and weak pinning at the domain wall for the dislocations.