Dynamic Wetting of CaO-Al 2 O 3 -SiO 2 -MgO Liquid Oxide on MgAl 2 O 4 Spinel
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UNDERSTANDING and controlling inclusion removal from steel is critical in modern steelmaking.[1] Inclusions are usually formed as a reaction product of the steel deoxidation process, though they may also result from slag and mold flux entrainment, refractory degradation, or precipitation events on steel solidification. They are generally removed by reacting with a slag (liquid oxide) phase. This is primarily achieved by optimizing the process conditions to promote contact and reaction between the inclusion and liquid oxide.[2] Efficient inclusion removal from steel is achieved when HAMED ABDEYAZDAN, Ph.D. Student, and BRIAN J. MONAGHAN, Director of the Engineering Materials Strength, are with the Pyrometallurgical Research Group, School of Mechanical, Materials and Mechatronic, University of Wollongong, Wollongong, NSW 2522, Australia. Contact e-mail: [email protected] NESLIHAN DOGAN, Lecturer, is with the Department of Materials Science and Engineering, McMaster University, Hamilton, ON L8S 4L7, Canada. M AKBAR RHAMDHANI, Lecturer, is with the Faculty of Science, Engineering and Technology, Swinburne University of Technology, Hawthorn, VIC 3122, Australia. MICHAEL W. CHAPMAN, Process Engineer, is with BlueScope Steel Ltd, Port Kembla, NSW 2505, Australia. Manuscript submitted May 19, 2014. Article published online October 18, 2014. 208—VOLUME 46B, FEBRUARY 2015
the inclusions contact the slag phase, leading to bonding and dissolution in the slag. If the bond is weak, then local fluid conditions are likely to result in the shearing of the inclusion-slag bond, and the inclusions remain in the steel. The strength of the inclusion bond or reactivity with slag may be assessed by measuring the dynamic wetting of the slag on a substrate made of the inclusion phase.[3] Research on inclusion removal in steel refining is principally divided into categories of flotation of inclusion to the steel/slag interface,[4,5] modification to improve reactivity/separation with the slag phase,[6] and dissolution in the slag phase.[7–13] A number of previous studies relevant to inclusion dissolution in slags have been carried out on bulk refractory or ceramic materials[14–18] where the material is dipped in slag and held for a period of time, removed, then analyzed for slag corrosion and/or penetration. Some recent studies have used high-temperature microscopy offering the possibility of analyzing the dissolution behavior of a single inclusion in a slag directly.[7–13] Monaghan and Chen[7] and Valdez et al.[12] used high-temperature microscopy to investigate the effect of slag basicity on spinel inclusion dissolution. They found that the rate of dissolution of the spinel particles increased with increasing basicity of the slag. METALLURGICAL AND MATERIALS TRANSACTIONS B
The least understood component of inclusion removal is inclusion reactivity/separation with the slag phase.[19] The inclusion has to travel across the steel-slag interface to wet the slag. This is favored when contact angle (h) for the steel inclusion is greater than 9
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