Effect of cooling rate on non-metallic inclusion formation and precipitation and micro-segregation of Mn and Al in Fe–23Mn–10Al–0.7C steel

The present study assesses the influence of the cooling rate on the morphology, composition, number density, size distribution of inclusions, and microsegregation of elements in Fe–23Mn–10Al–0.7 steel. The results indicate that with the increase of cooling rate from 5.1 K/s to 14.51 K/s, the total number density of inclusions increases from 28 mm−2 to 32 mm−2, with no change in the type of inclusions, the average size of MnS inclusion decreases from 9.57 μm to 5.21 μm. The precipitation and growth of MnS inclusion are predicted according to the coupled model, matching well with the experimental results. Furthermore, it is observed that AlN inclusion formed in the liquid steel can float up to the surface of the liquid steel, reducing the dissolved nitrogen content in the steel. As the cooling rate increases, the size and density of AlN inclusions on the liquid steel surface decrease. Combining the lattice mismatch of inclusions and the pushing and engulfment behavior of inclusions, the effect of cooling rate on the MnS precipitation for Al2O3 and AlN is analyzed. Moreover, under different cooling rates, Al segregation is very remarkable and it is low in interdendritic regions but high in dendrite stems.