Influence of La addition on Non-metallic Inclusions of electrothermal FeCrAl alloy

Abstract

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 Al₂O₃ 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, Al₂O₃ was modified into LaAlO₃. When the amount of La was 0.0378%, the main type of inclusion was LaAlO₃+La₂O₂S, the number of inclusions increased obviously, and the proportion of La₂O₂S increased gradually with the increase of heat preservation time. When the content of La was 0.0964%, the proportion of La₂O₂S increased further. After heat preservation for 60 minutes, only La₂O₂S 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, LaAlO₃ 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 La₂O₂S polymerization is weak, and the average particle size of inclusions in the samples containing La₂O₂S 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.