Method of manufacturing slag-forming mixture for the secondary steel refining in a ladle or in a ladle furnace

摘要

The subject matter of the invention is a method of producing a slag-forming compound for secondary steel refining in a ladle or a ladle furnace. According to the invention, the method of producing a steel-forming compound for secondary steel refining in a ladle or a ladle furnace is as follows: the fragmented slag obtained in the reduction process of steelmaking converter slag with the participation of roasted bauxite or in the reduction process of steelmaking calcium-aluminium ladle slag is blended with fragmented roasted bauxite and/or metallurgical lime. The obtained calcium-aluminium compound (of particle size 10-40 mm and consisting of 20,0-55,0% CaO, 25,0-60,0% Al 2 O 3 , 6,0-11,0% SiO 2 , 2,0-6,5% MgO, 0,5-3,0% (FeO + %Fe 2 O 3 + %MnO), 0,5-2,5% TiO 2 , 0-0,1 % P 2 O 5 and 0,02-0,1 % S) is put into molten steel, so that the mass of solid precipitates in the calcium-aluminium refining slag formed on the surface of the molten steel at 1600°C, determined by computer thermodynamic databases, does not exceed 2,0% of the total slag mass. The reduction process of steelmaking converter slag of particle size under 50 mm, and roasted bauxite of particle size under 50 mm, the amount of which constitutes 15-20% of the mass of the slag reduced, is carried out in the presence of a carbon reducer of particle size under 5 mm, bringing in elemental carbon in the amount of 5,0-10,0% of the mass of the slag reduced. The reduction process of steelmaking calcium-aluminium ladle slag is carried out in the same conditions, only with the participation of a carbon reducer bringing in elemental carbon in the amount of 2,0-5,0% of the mass of the slag reduced. The SiO 2 content in the slag reduced is 10,0-20,0%, and the sulphur content is 0,01-0,15%. The total content of ferrous and manganese oxides in the reduced slag is under 3,0%. The roasted bauxite put into the reduced steelmaking converter slag or reduced steelmaking calcium-aluminium ladle slag contains 86,0-92,0% Al 2 O 3 , 4,0-6,0% SiO 2 , 0-0,5% MgO, 1,2-1,8% Fe 2 O 3 , 3,0-4,0% TiO 2 and 0-0,8% CaO, and the metallurgical lime put into the reduced steelmaking converter slag or the reduced steelmaking calcium-aluminium ladle slag contains 94,0-98,0% CaO, 1,0-2,0% SiO 2 , 0-0,5% MgO and 0,5-5,0% volatile matter.