Abstract: In order to optimizate Q345C steel production process, the experiment has been carried out on Q345C steel by adding TiN nanoparticle in Q345B ladles without changing the process of steelmaking and rolling. The effect of diffrent TiN nanoparticle additions on mechanical properties and microstructure of Q345 steel was researched. The results showed that the mechanical properties of Q345B test steel could meet the requirements of Q345C steel with 0.05% (mass fraction) TiN nanoparticle addition, and the efficiency of Q345C steel rolling production was increased by 20% with the test process. The grain size of the test steel was refined slightly and reached to between Class 8 and Class 10. The TiN nanoparticlethe added in the Q345 steel existed in the form of pure substance in the steel and play the role of heterogeneity nucleation and nail in steel.

Key words: ladles, TiN nanoparticle, mechanical properties, microstructure