Effect of Alumina Morphology on the Clustering of Alumina Inclusions in Molten Iron

Abstract

Clustering of alumina inclusions during liquid processing of steel significantly influences its cleanliness and mechanical properties. We have therefore studied the effect of alumina inclusion morphology on their clustering behavior in molten iron. Alumina inclusions were extracted from iron samples taken at 1 min after Al addition. Dendritic, spherical, plate-like, faceted and clustered alumina inclusions were identified and their clustering degrees were measured. The clustering degree increases in the order of spherical, dendritic, plate-like and faceted inclusions. To explain this, attractive force between two alumina particles with different shape combinations, i.e., sphere-sphere (S-S), sphere-plane (S-P), plane-plane (P-P), was calculated based on the theory of spontaneous cavitation. The attractive force is influenced significantly by particle shape. S-S type has the smallest attractive force and the shortest acting length. P-P type has the largest attractive force and the longest acting length. This explains that spherical inclusions have the lowest clustering degree. The lower clustering degree of plate-like inclusions, compared with faceted inclusions, is due to that molten iron wets plate-like inclusions better.

A Study on the Nonmetallic Inclusion Motions in a Swirling Flow Submerged Entry Nozzle in a New Cylindrical Tundish Design

“…In addition, the interaction between nonspherical inclusions, such as the faceted inclusions, and the refractory wall seems like a plane-plane type interaction. According to the research by Zheng et al, [57] this kind of interaction is stronger compared to a sphere-plane type interaction, namely, the interaction between a spherical inclusion and a refractory wall. This means that nonspherical inclusions may easily stick to the wall once they move close to the wall compared to spherical inclusions.…”

Agglomeration Behavior of Non-Metallic Particles on the Surface of Ca-Treated High-Carbon Liquid Steel: An In Situ Investigation

“…There are several types of attraction forces between non-metallic inclusions. Figure 6 summarized three types of attraction force the Van der Waals force, the force due to the gas cavity and the capillary force, which have been estimated by Zheng et al [4]. The measured attraction force at the molten steel surface is calculated by Equation (2) and also plotted in this graph.…”

“…It has been indicated that bonding through the cavity bridge may be the main reason for alumina inclusions strongly agglomerating in liquid steel. Furthermore, Zheng et al investigated the attractive forces between different shapes of alumina inclusions based on the theory of spontaneous cavitation [4]. By calculating the rupture energy of a cavity bridge, Zheng et al [4] demonstrated that a faceted inclusion has the strongest attractive force, which was reflected in a plate-like, dendritic and spherical shape.…”

“…Furthermore, Zheng et al investigated the attractive forces between different shapes of alumina inclusions based on the theory of spontaneous cavitation [4]. By calculating the rupture energy of a cavity bridge, Zheng et al [4] demonstrated that a faceted inclusion has the strongest attractive force, which was reflected in a plate-like, dendritic and spherical shape. Also Fuchigami et al [5] developed an agglomeration model by combining a coagulation calculation and flow simulation of liquid steel, where coagulation of alumina and slag-origin oxide inclusions were considered [5].…”

Analysis of Fluid Flow of Liquid Steel through Clogged Nozzles: Thermodynamic Analysis and Flow Simulations

“…The dissolved oxygen reacts with aluminum in steel to precipitate alumina, forming a dense network adhered to the internal wall of the nozzle, as shown in Equation (6). Inclusions that come with the steel through the nozzle easily adhere to this initial network through surface tension and diffusion mechanisms [3] intensifying the problem. 2½Al Fe þ 3½O Fe ¼ hAl 2 O 3 i Fe (6) Regarding Ti additions to steel, it is generally known that nozzle clogging during casting Ti-stabilized ultralow-carbon steels (Ti-SULC) is more severe and takes shorter forming times than when casting low-carbon aluminum-killed steels (LCAKS).…”