Thermodynamic Analysis of TiN Precipitation in SWRH92A High Carbon Tire Cord Steel Under the Influence of Solute Micro-segregations During Solidification

The precipitation of TiN inclusion during the solidification of SWRH92A high carbon tire cord steel has been thermodynamically calculated. The influence of solute micro-segregations calculated by Ohnaka and Clyne–Kurz models, respectively, on the thermodynamic parameters is considered. The TiN precipitation module is coupled with the Ti and N micro-segregations when the condition of TiN precipitation is satisfied. Furthermore, the TiN growth is predicted based on the thermodynamic calculation results. The results first show that the solute elements of molten steel segregate to different extents during solidification. The carbon concentration increases most significantly by about 1.8 wt pct due to its highest original content. By coupling TiN precipitation module with solute micro-segregation module, the segregated ratios of Ti and N decrease after the TiN inclusion starts precipitating. With cooling rate increasing from 0.17 to 1.67 K/s, TiN precipitation starts earlier, but the TiN particle size decreases from about 10 to about 3 μm. The TiN inclusion sizes calculated in the Ohnaka and Clyne–Kurz model cases are close and well validated by the metallographic images of TiN inclusions and the statistical data of TiN particle size distribution in high carbon tire cord steels. This agreement encourages the proposed calculation method and provides guidance for the future thermodynamic studies of nonmetallic inclusions of steel.