Analysis of Agglomeration of Al2O3 Particles in Liquid Steel

Abstract

AnAlysIs of AgglomerAtIon of Al2o3 pArtIcles In lIquId steelThe removal of non-metallic inclusions from liquid steel is a result of co-operation of fluctuation, adhesion and agglomeration effects, with emphasis on agglomeration which plays the most important role. It is based on a few types of collisions between non-metallic particles, where turbulent collisions are most prominent. As a result of agglomeration, nonmetallic inclusions are intensely removed through flotation and increase of different dimensions of inclusions, which manifests itself with the occurrence of clusters mainly composed of Al2O3 precipitations. Authors investigated the agglomeration effect by making computer simulations with the use of the PSg method. The calculations were performed for a definite population of spherical particles of radius r in the steel volume. The applied calculation method allows for analyzing the dynamics of the collision process. The assumed initial number of particles remains constant, only the number of particles in specific sizegroups varies. It was also revealed that the process of agglomerates formation is much faster for particles having a bigger initial radius. in the case of very small precipitations (r=1 μm) their removal through agglomeration is very difficult because the probability those collisions can take place between them rapidly decreases.

Archives of Foundry Engineering

“…It should be considered that some of the inclusions which had contact with the filter walls do not form a permanent connection but are entrained by metal. This effect is expressed by the collision efficiency coefficient β [26][27][28][29][30].…”

“…In the tundish conditions there is a definite population of particles of radius r and number in steel volume v , i.e. density n. The efficiency of filtration of a definite population of inclusions in the course of turbulent collisions can be analyzed with the Particle Size Grouping (PGS) method worked out by T. Nakaoka and others [33] and used in works [26,[28][29][30]33]. The calculations in the model were based on the population balance equation ( 2):…”

Computer Simulation of the Formation of Non-Metallic Precipitates During a Continuous Casting of Steel

“…in the case of δ phase crystallization, all components of the alloy tend to cluster in the liquid phase. under these conditions the precipitates can be formed during the crystallization process [6][7][8][13][14][15][16][17][18]. The concentration of component "i" of liquid steel on the crystallization front depends on the operation of two factors: the rate of advancement of the crystallization front and the diffusion rate of a component in the solid phase.…”

“…On the other hand, a small amount of fine oxide inclusions or their precipitation during crystallization processes can significantly influence the way in which the structure of the cast steel is formed. The positive effect of non-metallic oxides precipitates on the steel structure is principally related to their similar sizes, of 1 µm, and the uniform distribution within the metal volume [1][2][3][4][5][6]. This can happend when the precipitates are formed during the steel crystallization.…”