Direct Measurement of Agglomeration Force Exerted between Alumina Particles in Molten Steel

Abstract

As a fundamental study to clarify the agglomeration and coalescence of alumina inclusions in molten steel from the viewpoint of interfacial chemical interactions, it has been experimentally verified for the first time that significant agglomeration force is exerted between alumina particles in aluminum deoxidized molten steel by using a newly established experimental method. In this method, the agglomeration force exerted between alumina particles in molten steel is directly measured separately from the effect of molten steel flow. In addition, it has been quantitatively demonstrated that the contact angles measured between aluminum deoxidized molten steel and an alumina plate are larger than those between the molten iron-oxygen alloy and the alumina plate, which have already been measured by other researchers. Moreover, it has also been indicated by analyzing the actual measurement values of agglomeration force with an interaction model taking contact angles and interfacial properties into consideration that the agglomeration force between the alumina particles in aluminum deoxidized molten steel derives not from the van der Waals force but from the cavity bridge force occurring due to molten steel, which is unlikely to wet the alumina particles. Meanwhile, it has been assumed that the agglomeration force on spherical alumina inclusions in aluminum deoxidized molten steel calculated on the basis of the interaction model according to the cavity bridge force is greater than the buoyant force and drag force, and the alumina inclusions once coming into contact are therefore not prone to be simply dissociated even under molten steel flow. Thus, they maintain the agglomeration state and are subsequently sintered and form comparatively solidly bonded alumina clusters.

Interaction between Alumina Inclusions in Molten Steel Due to Cavity Bridge Force

“…The longer this working distance of agglomeration force, the higher the probability of agglomeration among alumina inclusions. Therefore, in addition to the previously reported absolute value measurement of agglomeration force, 1) it is probably important to elucidate the effect of the interparticle surface distance on the agglomeration force to understand the agglomeration mechanism of alumina inclusions.…”

“…Al 2 O 3 Cylinders in Molten Steel An experiment in which the Al 2 O 3 cylinders between which the agglomeration force was measured in the previous report 1) were immersed in molten steel was conducted to examine the influences of the interparticle surface distance on the cavity bridge formation between the Al 2 O 3 inclusions in molten steel. Figure 2 shows an experimental device for cavity bridge formation in molten steel.…”

“…1) On the basis of the results mentioned above, it is assumed that cavity bridges are formed between particles in liquid metal when the particles have the contact angle with the liquid metal of 90° or more and difficulty in wettability with liquid metal.…”

“…6. Here, according to the results of the previous report, 1) since the molten steel used in the experiments was the Al deoxidized molten steel whose composition resembles that of pure iron, the surface tension of Al deoxidized molten steel, the contact angle of that with Al 2 O 3 , and pressure difference between cavity bridges and molten steel were putted at 1.884 N·m through the mercury experiments also gives 58% of the calculated values from Eq. (7) and lies within the results of the molten steel experiments.…”

“…In a previous report, 1) the author established a new experimental method that extracts the agglomeration force exerted between alumina particles in molten steel separately from fluid dynamic action and thus directly determines the agglomeration force to elucidate the agglomeration mechanism of alumina inclusions in molten steel in view of the interfacial chemical interaction between molten steel and inclusions. Using the above-mentioned method, it was demonstrated that a large agglomeration force is exerted between the alumina particles in molten steel, and through the analysis of the actually measured agglomera- (Received on January 20, 2016; accepted on March 7, 2016; originally published in Tetsu-to-Hagané, Vol.…”