Optimization of the Interfacial Properties between Mold Flux and TiN Substrate Through the Regulation of B₂O₃

Abstract

Titanium nitride (TiN) inclusions are easy to precipitate in the high temperature processing of titanium alloying steels, which tends to introduce numerous surface defects on the final continuous casting slabs. This study utilizes B₂O₃ to regulate the interfacial properties between the designed mold fluxes and TiN, with the aim to resolve above problems. The results show that the spreading behavior of the mold flux on the TiN substrate is enhanced, and the interfacial contact angle starts to drop at a lower temperature (from 1473 K for Sample 1 to 1343 K for Sample 4) with the addition of 0–9 wt.% B₂O₃, as the melting behavior of the designed mold fluxes has been improved. The interfacial reactions between the TiN substrate and molten fluxes are also promoted with the addition of B₂O₃, where more bubbles are observed in the tested mold fluxes samples. For Sample 1 without B₂O₃, quite a few TiN particles couldn’t be dissolved and remains in the matrix phase, where the major formed phase is perovskite (CaTiO₃) that would deteriorate the high temperature properties of mold flux severely. However, most TiN particles have been dissolved in the optimized mold fluxes, as major of them have reacted with mold fluxes, resulted in the more generation of titanium oxides phase in the samples. In addition, the calculated phase diagram of CaO–SiO₂–TiO₂ slag system under different B₂O₃ contents indicates that the formation and precipitation of CaTiO₃ can be effectively inhibited by the addition of B₂O₃.