Analysis of Precipitation of NbC in Low Reduction Ratio Conditions

Compared with the thin plate production process, the behavior of NbC precipitating would be different in thicker plate from the rolling processing due to reduction ratio conditions. The mechanism of epitaxial growth of NbC precipitating along with TiN particles was observed. The distribution of TiN particles, which influenced by N content in steels, would determine the distribution of the combined TiN + NbC particles by transmission electron microscopy. TiN particle is a high-temperature precipitate. The TiN particle is precipitated completely before the NbC particle is precipitated. It is concluded that the distribution of TiN was most important factor to control austenite grain size by Zener drag force. When the N content was higher in the steel would result in the coarser TiN particles which are harmful to controlling the size in roughing. Increasing of N content did not lead to an increase in the Zener drag force to control austenite grain size.