Influence of La addition on non-metallic inclusions of electrothermal FeCrAl alloy

Aiming at the effect of rare earth La on the type and distribution of inclusions in electrothermal FeCrAl alloy, the three-dimensional morphology and composition of inclusions were observed and analyzed by SEM-EDS, and the size and quantity of inclusions were statistically analyzed. The results show that there is only Al ₂O ₃ inclusion at 1600 ℃. During solidification, with the increase of solid fraction in the alloy system, AlN precipitated at the front of solidification. After adding 0.0093 % La, Al ₂O ₃ was modified into LaAlO ₃. When the amount of La was 0.0378 %, the main type of inclusion was LaAlO ₃+La ₂O ₂S, the number of inclusions increased obviously, and the proportion of La ₂O ₂S increased gradually with the increase of heat preservation time. When the content of La was 0.0964 %, the proportion of La ₂O ₂S increased further. After heat preservation for 60 minutes, only La ₂O ₂S inclusion existed stably in the steel. The polymerization characteristics of inclusions have a significant influence on the particle size of inclusions. At 1600 ℃ for 60 minutes, LaAlO ₃ showed a strong polymerization trend in the early stage of heat preservation, and the average particle size of inclusions first increased from 2.34 μ m to 3.31 μm and then decreased to 1.93 μ m. The trend of La ₂O ₂S polymerization is weak, and the average particle size of inclusions in the samples containing La ₂O ₂S is small and stable. In the early stage of heat preservation, the average particle size of inclusions is stable in the range of 1.8–2.0 μm.