Evolution of Nonmetallic Inclusions during the Electroslag Remelting Process

Abstract

The evolution of inclusions during the electroslag remelting (ESR) process, especially the inclusions in droplets is investigated by an industrial trial which remelts a plain carbon steel billet in the slag of CaF2–Al2O3–CaO–MgO. Results show that oxide inclusions change from SiO2–MnO to Al2O3–MnO during the ESR process. The transfer of aluminum from the slag to the steel increases the aluminum content in the steel and causes the reaction between (MnO), (SiO2) in inclusions with the [Al] in the steel to generate (Al2O3) inclusions. Thermodynamic results show that inclusion evolution is mainly influenced by the temperature and the total Al content in the steel. With the increase in temperature at the electrode tip, the MnO content in inclusions increases rapidly. Meanwhile, as the aluminum transfers from the slag to the steel, the Al2O3 inclusion increases clearly with the corresponding decrease in MnO and SiO2 inclusions. In addition, from the electrode to the ingot, the number density of inclusions decreases from 208.82 to 33.49 # mm−2, whereas the average size increases from 3.79 to 5.76 μm. Both the chemical modification and the physical absorption of slag mainly occur at the liquid film and droplet stage.