Effect of External Electric Field Application on the Clogging Behavior of Submerged Entry Nozzles During Aluminum-Killed
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INTRODUCTION
DESPITE the significant improvement in the thermal shock resistance of submerged entry nozzle (SEN) materials, the clogging, blockage, and erosion of such materials have become common service failure problems.[1,2] Some serious clogging can even cause complete blockage of the SEN, which can lead to accidents related to continuous casting.[3] The effective control and prevention of clogging in SENs have been the subject of extensive investigation and improvement in the continuous casting process. During the casting of SENs, clogging may occur at the inner wall of the nozzle due to continuous adhesion and sintering of inclusions.[4–7] Unstable clogging and adhesion are continuously introduced into the steel, forming new large inclusions in the molten steel that flows with high speed, which can seriously affect the quality of the steel. At the same time, due to the continuous dissolution and reaction between inclusions and SEN, the size and number of inclusions in the steel may be further increased.[8,9]
CHEN TIAN, LEI YUAN, DANBIN JIA, XINGLONG YAO, and TIANPENG WEN are with the School of Metallurgy, Northeastern University, Shenyang 110819, P.R. China. Contact email: yuanl@smm.neu.edu.cn JINGKUN YU is with the School of Metallurgy, Northeastern University and also with the State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang, 110819, P.R. China. Manuscript submitted March 31, 2020.
METALLURGICAL AND MATERIALS TRANSACTIONS B
At present, SEN clogging can be roughly divided into four categories: deoxidation products, composite oxides, solidified steel, and reaction products.[10,11] The formation of SEN clogging is a complex physical and chemical process, and the involved influencing factors and conditions are numerous and interact with each other. In particular, the most common cause of clogging is the presence of alumina inclusions in the molten steel.[12–14] Many researchers have obtained valuable results on the clogging inhibition behavior of inclusions in SENs.[15–21] Many studies in the literature show that most metal oxides in liquid metal carry a positive charge, and these inclusions will migrate in the direction under the action of electric field.[22–25] Meanwhile, in recent years, our research team has found that the charge of the inclusions may be generated because of high-speed friction between molten steel and the inner wall of the SEN. The electric charge potential strength is proportional to the speed of continuous casting. The explanation of this phenomenon is that the electrification of alumina inclusions is due to the loss of negative electrons during friction.[26,27] Moreover, this phenomenon is also related to the clogging behavior of the SEN. Based on this principle, our team tried to prevent clogging by controlling the charged behavior of the SEN. For example, in industrial testing, the method of using an adaptive electric field or an electric current pulse to eliminate the frictional electric field has played a beneficial role in improving clogging control.[27–29]
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