Effect of Compressive Deformation on the Transformation Behavior of an Ultra-Low-Carbon Bainitic Steel

Abstract

In this work, an experimental ultra-low-carbon-bainitic (ULCB) steel was prepared to study the effect of a prior compressive deformation on the transformation behavior during continuous cooling. It is found that prior deformation of austenite significantly enhances the bainitic transformation. At the same cooling rate the specimen with the prior deformation has a higher bainite start temperature (Bs) than the specimen without the prior deformation; in addition, the difference of Bs temperature becomes much larger at the higher cooling rate. This result is not consistent with that reported by Tamehiro et al. On the other hand, an isothermal experiment has been utilized to investigate the stability of the deformed austenite. It is suggested that the kinetics of precipitation of Nb(C, N) in deformed austenite influences the hardenability of bainite in local regions of the austenite matrix. This reason can explain why the deformed austenite grains produce finer allotriomorphic ferrite grains in a relatively slow cooling condition.