Process and apparatus for vacuum degassing molten steel

• Main Authors: YAMADA; ATSUMI, NOBUMOTO; AKIRA, HIRAOKA; TERUYOSHI, GOFUKU; HIROKI, OONUKI; KAZUO, ISONO; TAKAHIRO, FUKUDA; KAZUHISA, NAGAHAMA; HIROSHI
• Format: Patent
• Language: English
• Published: 09.05.1995
• Edition: 6
• Subjects: CHEMISTRY; METALLURGY; METALLURGY OF IRON; PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OFWROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS

Molten steel is efficiently vacuum treated in a vacuum treatment vessel provided with a top blow lance capable of injecting oxygen and a gaseous fuel at desired flow rates, respectively, into the molten steel. The blow lance is provided on the top of the vacuum treatment vessel and is supported so as to be freely vertically movable. By spacing the lower end of the top blow lance not more than 2 m from the surface of the molten steel bath and injecting only oxygen onto the molten steel, and spacing the lower end of the top blow lance 1.0 m or more from the surface of the molten steel bath and injecting both oxygen and a gaseous fuel gas onto the molten steel, the temperature of the molten steel is prevented from decreasing during the vacuum treatment and the molten steel is so prevented from depositing on the inside wall of the vacuum treatment vessel. The top blow lance includes an oxygen injection section having a throat and a tapered portion connected to the lower end of the throat, and a plurality of fuel gas supply ports provided in the tapered portion. The throat and tapered portion are coaxial with the axial center line of the lance.