Wangzhong Mu

Agglomeration of Non-metallic Inclusions at Steel/Ar Interface: In-Situ Observation Experiments and Model Validation

Better understanding of agglomeration behavior of nonmetallic inclusions in the steelmaking process is important to control the cleanliness of the steel. In this work, a revision on the Paunov simplified model has been made according to the original Kralchevsky–Paunov model. Thus, this model has been applied to quantitatively calculate the attractive capillary force on inclusions agglomerating at the liquid steel/gas interface. Moreover, the agglomeration behavior of Al2O3 inclusions at a low carbon steel/Ar interface has been observed in situ by high-temperature confocal laser scanning microscopy (CLSM). The velocity and acceleration of inclusions and attractive forces between Al2O3 inclusions of various sizes were calculated based on the CLSM video. The results calculated using the revised model offered a reasonable fit with the present experimental data for different inclusion sizes. Moreover, a quantitative comparison was made between calculations using the equivalent radius of a circle and those using the effective radius. It was found that the calculated capillary force using equivalent radius offered a better fit with the present experimental data because of the inclusion characteristics. Comparing these results with other studies in the literature allowed the authors to conclude that when applied in capillary force calculations, the equivalent radius is more suitable for inclusions with large size and irregular shape, and the effective radius is more appropriate for inclusions with small size or a large shape factor. Using this model, the effect of inclusion size on attractive capillary force has been investigated, demonstrating that larger inclusions are more strongly attracted.

In situ observation of deformation behavior of chain aggregate inclusions: a case study for Al 2 O 3 at a liquid steel/argon interface

Particle aggregation is a widespread phenomenon spontaneously occurring in nature, and it is also widely explored in industry, for instance, metallurgical engineering and colloid chemical engineering. In this work, deformation behavior of Al2O3 aggregates in liquid steel is investigated as a case study. Using high-temperature confocal laser scanning microscopy, the morphologies of Al2O3 chain aggregates during their deformation are observed in situ at liquid steel/Ar interface. Thereafter, the change of morphology of aggregates over time is quantitatively investigated, and the results show that circularity of aggregates increases during deformation. This fact indicates that the morphology of aggregates tends towards spherical with time. The bending forces between the particles in an aggregate during the deformation are calculated based on the experimental data obtained from in situ observations. The force exerted to cause bending is predicted by the capillary force model established for attractive capillary force of inclusions. It is found that the bending force is slightly lower than the capillary force, and this indicates that the capillary force plays a significant role in the bending of aggregates during deformation. Moreover, the difference between the two forces is due to a resistance force existed from inflection part of the aggregate during deformation. The residence is quantitatively evaluated, and there is a clear tendency showing that the resistance force increases with decreasing distance between two particles during bending. In addition, initial sintering between contacted particles after bending is reported, and the radius of neck formed between sintered particles is evaluated. Finally, the effects of inclusion size and steel flow velocity in actual steelmaking process on the radius of neck and shear stress exerted on the sintered neck during deformation are discussed.