Abstract: The gap between an insertion hole formed in a covering of a ladle and an electrode inserted through the insertion hole is sealed by sealing means. The sealing means has a cap seal longitudinally and slidably fitted over the electrode. A base seal is hermetically disposed between the cap seal and the covering in such a manner that a gap is provided between the electrode and the base seal. The base seal has a gas injection nozzle intended to discharge a gas toward the electrode and another gas injection nozzle intended to discharge the gas downwardly. The use of the base and cap seals enables securing the sealing functions thereof despite any movement of the electrode, thus preventing the pickup of [N] as well as the reoxidation of molten steel. When a gas seal is effected by the formation of a flow of gas rotating around the electrode about the axis thereof, the sealing performance can be more enhanced.

Abstract: Three electrodes are dipped into slag on molten steel in a ladle. The electrodes are connected to a three-phase AC voltage. An arc is formed between each electrode and molten steel upon energizing the electrodes. The molten steel is heated by arc heat. Each electrode has a gas flow path extending longitudinally along its center. The gas flow path is open at the lower end of each electrode to constitute a gas injection port. Ar gas is injected from the gas injection port through the gas flow path. Nitrogen is removed from the arc region between the electrodes and the molten steel and its peripheral region to prevent the nitrogen pickup phenomenon of molten steel. If a powder mixture of chromium ore and carbon is added to the Ar gas, chromium ore is reduced by carbon with arc heat to add reaction product of chromium to the molten steel. If a flux powder is added to the Ar gas, the flux is melted and slagged by the arc heat.