Numerical Simulation on Saffman Force Controlled Inclusions Removal during the ESR Process

Chuxiong Sun,Huai Wang,Zuosheng Lei,Weili Ren,Yunbo Zhong,Zhe Shen,Qiang Li,Tianxiang Zheng,Yifeng Guo

doi:10.3390/met10050647

Abstract

Electroslag remelting (ESR) is an effective method for removing nonmetallic inclusions from steels or alloys. The main stage of inclusion removal during ESR is the aggregation of liquid metal film (LMF) to form droplets at the consumable electrode tip. In this study, a lab-level ESR experiment was carried out. The number and size of inclusions at the characteristic position of the electrode were quantitatively counted. The number of inclusions in the center position of LMF were larger than that in other regions. To elucidate these phenomena, a two-dimensional mathematical model was established to study the migration of inclusions in LMF. The results indicate that due to the large velocity gradient in LMF, the Saffman force is strong enough to offset the buoyant force and drag the inclusions toward the slag/LMF interface (SFI), where the inclusions will be dissolved in the SFI region by the molten slag. This study demonstrates that the Saffman force plays a key role in the removal of nonmetallic inclusions in LMF during the ESR process.

Highlights

Electroslag remelting (ESR) processes have been widely employed to produce high-quality alloys and steels because they can improve the purity and structural quality of ingots [1,2,3,4,5,6]
Reported three stages of inclusion removal in the ESR process: aggregation of the liquid metal film (LMF) to form droplets at the electrode tip as the first stage; droplets falling through the slag as the second stage; and the interaction between the liquid slag and the molten steel as the third stage
They experimented with radioisotopes in the ESR process and came to the conclusion that the main stage of inclusion removal is the aggregation of LMF to form droplets at the consumable electrode tip

Summary

Introduction

Electroslag remelting (ESR) processes have been widely employed to produce high-quality alloys and steels because they can improve the purity and structural quality of ingots [1,2,3,4,5,6]. The number, size, and distribution of nonmetallic inclusions are significant indicators of the purity of steels and alloys. To meet the higher demands for cleaner and higher-quality steels and alloys, the ESR process has become an essential technology to remove impurities and nonmetallic inclusions. Reported three stages of inclusion removal in the ESR process: aggregation of the LMF to form droplets at the electrode tip as the first stage; droplets falling through the slag as the second stage; and the interaction between the liquid slag and the molten steel as the third stage. For the first stage, the physical dynamic mechanism is still unclear, which forces dominate this process and how the inclusions migrate to the LMF, and need to be further investigated

Methods

Results

Conclusion