중탄소강의 동적 재결정에 관한 연구

초록

The dynamic recrystallization (DRX) of medium carbon steels (SCM 440 and POSMA45) was studied with torsion test in the temperature range of 900 - 1100℃ and the strain rate range of 5.0x10-2 - 5.0x100/sec. To establish the quantitative equations for DRX, the evolution of flow stress curve with strain was analyzed. The critical strain (εc) and strain for maximum softening rate (ε*) could be confirmed by the analysis of work hardening rate (dσ/dε = θ). The volume fraction of dynamic recrystallization (XDRX) as a function of processing variables, such as strain rate (), temperature (T), and strain (ε) were established using the εc and ε*. For the exact prediction, the εc, ε* and Avrami' exponent (m') were quantitatively expressed by dimensionless parameter, Z/A, respectively. The transformation-effective strain-temperature curve for DRX could be composed. It was found that the calculated results were agreed with the experimental data for the steels at any deformation conditions.