Influence of basicity and TiO2 content on the precipitation behavior of the Ti-bearing blast furnace slags

Abstract

The present paper investigated the influence of basicity and TiO2 content on the crystallization behavior of the Ti-bearing blast furnace slag (Ti-BF slag). Single Hot Thermocouple Technique (SHTT) was applied to construct the Time-Temperature-Transformation (TTT) diagrams. Scanning Electron Microscope equipped with Energy-Dispersive X-ray spectroscope (SEM-EDX) and X-Ray Diffraction (XRD) were employed to observe the morphology and determine the crystalline phase of the Ti-enriched crystals. It was found that rutile was formed as the Ti-enriched phase when the basicity of the sample was lower than 0.6, and perovskite appeared as the Ti-enriched phase with an increasing basicity to 1.0. It was also noticed that the addition of TiO2 could decrease the incubation time in the TTT diagram of the samples. The kinetics of the formation of Ti-enriched crystals, rutile and perovskite, was studied, and the mechanism of crystallization and growth was further discussed. The results indicated that the crystallization of rutile was one-dimensional interface-controlled growth, and the nucleation rate varied with the holding time at different TiO2 content. While the precipitation behavior of perovskite was three-dimensional diffusion- controlled growth, and its nucleation rate decreased with the holding time. © 2013 ISIJ.