With high yield strength, toughness and good weldability, microalloyed steels are widely used in the automotive, pipeline and transportation industries. An understanding of the thermodynamics and kinetics of microalloy precipitation during casting and cooling can be important to microstructure control. Titanium nitride (TiN) precipitation is considered here, as TiN has high stability and may precipitate at temperatures near the liquidus. Titanium nitride precipitates may remain stable at elevated temperatures during later processing, suppressing grain growth during solid state processing or in weld heat-affected zones. Smaller precipitates have a greater effect on the grain boundary pinning and therefore the TiN size distribution is important.