METHOD OF PRODUCING ULTRA-LOW-CARBON STEEL

摘要

A method of producing an ultra-low-carbon steel by using a vacuum degasser on a molten steel has the steps of conducting vacuum decarburization to attain a predetermined level of carbon content, e.g., 25 ppm or below, in the molten steel while progressively reducing the pressure in said vacuum degasser, conducting addition of hydrogen in which hydrogen is dissolved in said molten steel while said pressure is temporarily elevated to 20 Torr or above, and conducting final decarburization after reducing said pressure to 2 Torr or below. The addition of hydrogen may be conducted to meet the following conditions: ¢H! wherein ¢H! represents the hydrogen content (ppm) in said molten steel in the state after the addition of hydrogen, ¢C! represents the carbon content (ppm) in the molten steel in the state after the addition of hydrogen, and ¢C!final represents the final carbon content (ppm) to be obtained.