The present work is carried out to study the evaporation of Na₂O from CaO–Al₂O₃–SiO₂–TiO₂–MgO–Na₂O slags with high basicity and high alumina in the temperature range of 1500–1560°C. The ratio of evaporation was determined by monitoring the Na₂O content change of the slag melt under isothermal reduction conditions. The results show that the evaporation ratio increases with increasing the temperature. Higher basicity and increasing concentrations of Na₂O, Al₂O₃ are also found to increase the evaporation ratio of Na₂O, while MgO addition only slightly enhances the evaporation ratio. With TiO₂ content increasing, the evaporation ratio first increases and then decreases. The evaporation rate of Na₂O appears to be controlled by chemical reaction at the slag/gas interface in the beginning, followed by a mixed reaction-mass transfer regime, and finally a liquid-phase mass transport step. The apparent activation energy is 134.74 kJ mol⁻¹ for the chemical reaction regime and 268.53 kJ mol⁻¹ for the liquid-phase mass diffusion step.

The effect of rare earth on the solidification structure of 3.2%Si-0.9%Al non-oriented silicon steel was investigated using industrial trials. The outputs demonstrated that increasing rare earth content leads to a decrease in the average size of equiaxed crystals in the casting billets. In order to further understand the rare earth on the grain refinement of δ-ferrite, the conventional inclusion detection technology, was used to investigate the distribution characteristics of inclusions, together with theoretical calculation of the equilibrium partition coefficients, pinning forces and mismatch degrees. The detection results of inclusions and the calculation results of pinning force showed that the effect of rare earth on the pinning force of inclusions was marginal. Thermodynamic calculation indicated that Ce addition had negligible effect on the equilibrium partition coefficient of Si, Al and Mn. Combined with the calculation results of GRF model, it is reasonable to consider that the contribution of rare earth element to the refinement of equiaxed crystals can be ignored. Further, the outcomes obtained from the E2EM model calculations revealed that the principal mechanism responsible for the refinement of equiaxed crystals through rare earth treatment can be attributed to the heterogeneous nucleation effect of (La, Ce)2O2S.

In this paper, the effect of rare earth Ce content on the morphology, composition, type and size distribution of inclusions in W350 non-oriented silicon steel was investigated by means of ICP-MS (inductively coupled plasma mass spectrometry), SEM/EDS (scanning electron microscope-energy Dispersive Spectrometer), and ASPEX (automated SEM/EDS inclusion analysis). The results showed that with the increase of Ce content in the steel, the modification sequence of inclusions was CeAlO₃→Ce₂O₂S→Ce_xS_y. The type and size distribution of inclusions in the steel obviously changed with the difference in added Ce content. When the added Ce content in the steel was 10 ppm, 14 ppm, 20 ppm and 30 ppm respectively, the rare earth inclusions were mainly CeAlO₃-Ce₂O₂S. Furthermore, when the added Ce content increased to 60 ppm, the rare earth inclusions were mainly Ce₂O₂S with a small amount of CeAlO₃ contained in part inclusions. When the added Ce content increased continually to 95 ppm, the rare earth inclusions were mainly Ce_xS_y-Ce₂O₂S. The critical Ce content for the conversion between CeAlO₃ and Ce₂O₂S was 41 ppm. To ensure that inclusions transform from CeAlO₃ to Ce₂O₂S, the Ce content in the steel should be greater than 41 ppm. Under the current experimental conditions, it was found that when the Ce content was 20 ppm, the number density and proportion of inclusions in the steel were lower, and their average size was larger. When the added Ce content increased to 95 ppm, the number density of inclusions in the steel significantly increased, which deteriorated the steel cleanliness.

In order to study the effects of rare earth La–Ce alloying treatment on the characteristics of inclusions in non-oriented silicon steels, industrial experiments were conducted studying the composition, morphology, size and quantity of inclusions in W350 non-oriented silicon steel during the RH (Ruhrstahl-Hereaeus) refining process and tundish process, after rare earth treatment. The products were analyzed by means of ICP-MS (inductively coupled plasma mass spectrometry), SEM/EDS (scanning electron microscope-energy dispersive spectrometry), and ASPEX (automated SEM/EDS inclusion analysis). The research results showed that the types of inclusions in experimental steel changed significantly after rare earth treatment. The types of inclusions after RE (rare earth) treatment are typically rare earth composite inclusions that are mainly composed of (La, Ce)Al₂O₃, and conventional inclusions. The addition of rare earth promotes the agglomeration of inclusions; the morphologies of the inclusions are mostly blocky, and some are distributed in long strips. After rare earth treatment during the RH refining process, the number of inclusions with sizes of 1.0~3.5 μm in the experimental steel is increased, and the average size of the inclusions is 2.66 μm. In addition, the number of inclusions larger than 4 μm in the specimens increases due to the collision and growth of inclusions caused by the RH circulation. After rare earth treatment during the tundish process, the number of micro inclusions with sizes of 1.0~2.5 μm in the specimen steels decreases, while the number of inclusions larger than 5 μm increases. The size distribution of micro inclusions in hot-rolled sheets after rare earth treatment was studied using TEM (transmission electron microscopy). In the specimens without rare earth, the content of micro inclusions (≤1 μm) is 51,458.2/mm² and the average size is 0.388 μm. In the specimens with rare earth added, the content of micro inclusions (≤1 μm) is 24,230.2/mm² and the average size is 0.427 μm. Compared to sheet produced by the original process, the iron loss of the 0.35 mm finished experimental sheet is reduced by 0.068 W/kg, and the magnetic induction is increased by 0.007 T. The iron loss of the 0.50 mm finished experimental sheet is reduced by 0.008 W/kg, and the magnetic induction is increased by 0.004 T. After rare earth treatment, the average size of micro inclusions increases and the magnetic properties are obviously improved.