Distribution and Precipitation Mechanism of TiN in Industrial Pure Iron Bloom

Abstract

The size and distribution of TiN particles have a great influence on the properties of industrial pure iron. It is necessary to understand TiN precipitation behavior in bloom. Herein, inclusions in industrial pure iron cast billets are observed. The temperatures and conditions for TiN precipitation are calculated using thermodynamics and kinetics. The results show a large number of TiN inclusions in the bloom, and the quantity density is the largest at the inner arc of the bloom. This is caused by the large cooling rate at the inner arc and the homogeneous nucleation of inclusions. According to the thermodynamic calculations, during the solidification of industrial pure iron, TiN begins to precipitate at a solidification fraction greater than 0.82. The amount of TiN precipitated during solidification is 93%, with TiN continuing to precipitate from the solid phase after the solidification is complete. The results of TiN particle growth kinetics reveal that MgO is the most effective in promoting TiN nucleation, followed by δ‐Fe, CaS, and MgAl2O4, the effectiveness of Al2O3 as a heterogeneous nucleation core is relatively poor. The radius of the TiN particles decreases with a decrease in the N and Ti content and an increase in the cooling rate.