<p>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.</p>
