Agglomeration of Solid Inclusions in Molten Steel
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Agglomeration of solid particles in liquid is relevant to numerous commercial products and industrial processes,[1] such as metallurgical engineering,[2,3] materials fabrication,[4,5] and pharmaceuticals.[6] During the steelmaking process, deoxidizer is added into the molten steel and inclusions are generated during the deoxidation production through the reaction between the deoxidizer and the dissolved oxygen.[7] Fine inclusions can grow rapidly through agglomeration and coalescence. Nevertheless, large clusters in the steel are detrimental to the mechanical properties and can easily deposit on the submerged entry nozzle, causing clogging.[8,9] Thus, understanding the agglomeration mechanism of inclusions in molten steel is of great importance for predicting and controlling inclusion behavior and steel cleanness. Generally, solid inclusions are nonwetted in the molten steel (the contact angle exceeds 90 deg), such as 136 deg for alumina inclusions[10] and 102 deg for silica inclusions.[11] Agglomeration easily occurred among those inclusions to form clusters.
HAOJIAN DUAN, YING REN, and LIFENG ZHANG are with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing (USTB), Beijing 100083, China. Contact emails: [email protected]; [email protected] BRIAN G. THOMAS, is with the Department of Mechanical Engineering, Colorado School of Mines, Golden, CO 80401 Manuscript submitted September 15, 2018. METALLURGICAL AND MATERIALS TRANSACTIONS B
Figure 1 shows the example of the agglomeration of alumina inclusions in interstitial-free (IF) steel. Recently, the cavitation theory[12–15] that the liquid spontaneously expelled from the gap between solid particles to form a cavity as the solid particles approach each other was used to explain the agglomeration of inclusions in the molten steel. Sasai[16,17] established an experimental method to directly measure the agglomeration force exerted between alumina inclusions in molten steel and to evaluate the formation and extinction behavior of cavity bridges between alumina inclusions. It was demonstrated that the agglomeration force is derived from the cavity bridge force. Zheng et al.[18] investigated the effect of alumina morphology on the clustering behavior by analyzing the attractive force between two alumina inclusions with different shapes in molten steel based on the cavitation theory. Even though the agglomeration of solid inclusions in the molten steel due to the cavitation was reported previously,[16–18] many details regarding this phenomenon still need to be further clarified. The current study investigated the formation and the stability of the cavity between solid inclusions from the view of free energy analysis based on the bridge cavitation theory. Several key parameters for the agglomeration, such as the equilibrium energy and the critical separation, were proposed and discussed. The agglomeration mechanism was proposed through the free energy analysis of the cavitation. Experimental results reported by Sasai[16,1
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