Effect of TiN on Sulfide Morphology of Non-Quenched and Tempered Steel

Abstract

In this paper, non-quenched and tempered steel was selected to observe sulfide inclusions in as-cast and forged steel with different Ti and N contents, and analyzed the influence of TiN on the precipitation, morphology, distribution and composition of MnS. The precipitation of MnS and TiN in liquid-phase, solid–liquid two-phase region and solid phase was comparatively analyzed from a thermodynamic perspective, and the effect of the thermodynamic precipitation sequence on composite sulfide was explored. It was found that the change in Ti content had little effect on the morphology of sulfide in its as-cast state, and the composite sulfide was more spindle-like in the forged state. The increase in Ti and N content will increase the content of composite sulfide containing TiN in the steel, especially the number of MnS with TiN as the nucleation core. The initial precipitation temperature of TiN is higher than that of MnS, which provides a thermodynamic explanation for the existence of composite manganese sulfide containing TiN. Titanium treatment provides a new way to improve sulfide morphology.