In this study, the industrial, experimental effect of a plasma heating system in the form of graphite electrode in the tundish of double-strand slab caster was evaluated for the first time. The system uses three graphite electrodes, two of which are cathodes and one of which is an anode, to form a conductive loop through molten steel in the tundish. The system is built on an old two-strand slab caster and is installed on the premise that the original ladle tundish equipment remains unchanged. The normal working power of the system is up to 1500 kW, and the heating rate of molten steel in the tundish can reach 1.0 °C/min under conditions of 5 t/min total steel throughput and a tundish capacity of 50 t. After the system was put into operation, the purity of molten steel undergoing heating was investigated. The sample analysis of low carbon steel and ultra-low carbon steel before and after heating showed that the contents of N and O in the steel did not increase, while the size of the oxide inclusions near the heating point increased but showed little change in terms of the overall quantity. This process benefited from the addition of inert gas during the heating process to control the atmosphere in the heating area, which prevents reoxidation. The sample analysis also showed that there is no obvious carbon absorption phenomenon after heating, and the fluctuation in C content is within 0.0001%, which is consistent with the general production results. By using this system, the temperature of molten steel in the steelmaking process can be reduced by 10~15 °C, allowing continuous low superheat casting to be supported, which is helpful for reducing production costs and improving the solidified structure inside the slab. The results of the study show that the plasma heating technology can be applied to the continuous casting of low carbon-nitrogen steel slabs, which shows the benefits of reducing emissions and improving production efficiency.
Keywords: continuous casting; graphite electrode; plasma heating; quality.