Hot Deformation Behavior of Non-Alloyed Carbon Steels.

Petr Kawulok,Rostislav Kawulok,Stanislav Rusz,Kateřina Konečná,Michal Sauer,Ivo Schindler,Petr Opěla

doi:10.3390/ma15020595

Abstract

The hot deformation behavior of selected non-alloyed carbon steels was investigated by isothermal continuous uniaxial compression tests. Based on the analysis of experimentally determined flow stress curves, material constants suitable for predicting peak flow stress σp, peak strain εp and critical strain εcrDRX necessary to induce dynamic recrystallization and the corresponding critical flow stresses σcrDRX were determined. The validity of the predicted critical strains εcrDRX was then experimentally verified. Fine dynamically recrystallized grains, which formed at the boundaries of the original austenitic grains, were detected in the microstructure of additionally deformed specimens from low-carbon investigated steels. Furthermore, equations describing with perfect accuracy a simple linear dependence of the critical strain εcrDRX on peak strain εp were derived for all investigated steels. The determined hot deformation activation energy Q decreased with increasing carbon content (also with increasing carbon equivalent value) in all investigated steels. A logarithmic equation described this dependency with reasonable accuracy. Individual flow stress curves of the investigated steels were mathematically described using the Cingara and McQueen model, while the predicted flow stresses showed excellent accuracy, especially in the strains ranging from 0 to εp.

Highlights

Dynamic recrystallization (DRX) is an important structure-forming process that occurs under the hot forming of metallic materials with low stacking fault energy [1,2,3,4,5]
The determined hot deformation activation energy Q decreased with increasing carbon content in all investigated steels
The critical strain required to induce the dynamic recrystallization εcrDRX is lower than the peak strain εp, which corresponds to the peak flow stress σp in the flow stress–strain curve

Summary

Introduction

Dynamic recrystallization (DRX) is an important structure-forming process that occurs under the hot forming of metallic materials with low stacking fault energy [1,2,3,4,5]. This process is important, especially at the continuous hot rolling of steel strips, bars or wires [6,7,8,9,10,11]. After reaching the steady state, i.e., the stress σss, there is a balance between the softening and strengthening processes, and with increasing strain, the stress in the area IV.th does not change (see Figure 1) [12,14,15]

Methods

Discussion

Conclusion