A characterization for the flow behavior of 42CrMo steel

In order to evaluate the flow stress and the dynamic softening characteristics of casting 42CrMo steel, isothermal upsetting experiments with height reduction 60% were performed at the temperatures of 1123 K, 1198 K, 1273 K and 1348 K, and the strain rates of 0.01 s−1, 0.1 s−1, 1 s−1 and 10 s−1 on thermal physics simulator Gleeble 1500. The flow behavior of the applied stress as a function of strain, strain rate and temperature exhibits a more pronounced effect of temperature than strain rate, and a typical characteristic of dynamic recrystallization softening. To characterize the flow behavior more factually and accurately, the traditional Fields–Backofen equation was amended, and an innovative mathematical model containing a softening item s, n-value and m-value variable functions was brought forth. The stress–strain curves calculated by the derived flow stress equation are fit with the experimental results well not only at the hardening stage but also at softening stage.