Effect of Cooling Rate and High N Content on the Precipitation and Growth of AlN Inclusions in Fe–23Mn–2Al–0.08 V High‐Manganese Nonmagnetic Steel

Abstract

Industrial experiments are carried out to investigate the precipitation and growth of AlN in Fe–23Mn–2Al–0.08 V steel with nitrogen content up to 80–92 ppm. AlN inclusions can be precipitated before solidification. The morphologies of AlN are mainly divided into hexagonal and needle‐like shapes. With the cooling rate decreasing from 36.66 to 0.71 K s−1, the equivalent diameters of typical AlN increase from 7.56 to 24.20 μm, and the total amount decreases from 203.01 to 60.00 mm−2. The relationship between the cooling rate and the number density is obtained: . The element segregation analyzed by electronic probe microanalyzer shows that aluminum concentration is low in interdendritic regions but high in dendrites. Aluminum segregation is very weak, and there is almost no nitrogen segregation. Thermodynamic calculation shows that AlN can precipitate before solidification with the nitrogen content higher than 58 ppm. The predicted results of AlN growth by kinetic analysis method can well reveal the growth trend. The nitrogen content (≥58 ppm) has a negligible effect on the size of AlN when the cooling rates are 3.02 and 0.71 K s−1, while the cooling rate has a significant effect on the size of AlN.