Additive for promoting slag formation in steel refining ladle
AssigneeHamilton Specialty Bar Division of Slater Industries, Inc.
InventorBradford C. Bowman
Life of this patent
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Abstract
In ladle refining of steel a molten protective slag covering is used consisting of iron blast furnace slag, or of a mixture of solid burnt lime and/or burnt dolomitic lime together with iron blast furnace slag in an amount effective to serve as a flux promoting the melting of the lime and dolomitic lime. The iron blast furnace slag avoids the environmentally harmful emissions caused by use of fluorspar as a flux. It forms a quicker melting slag, resulting in lower power usage and shorter refining times. It forms a final slag with good physical properties. There is considerable reduction of wear of the ladle and roof refractories and carbon pick up from the ladle refining electrodes is minimized.
Claims13
A process of ladle refining of steel, comprising disposing in a ladle a quantity of molten steel to be refined, adding a material forming a molten protective slag covering on the steel in the ladle, heating at least a region of the slag with electric current passed to carbon electrodes immersed in the slag, gently stirring the steel to allow it to be heated by heat transfer from said heated region without substantially disturbing the continuity of the protective slag covering, and to substantially homogenize the steel, and subsequently discharging the heated and homogenized steel from the ladle, wherein the improvement comprises said material forming a molten protective slag consisting essentially of iron blast furnace slag, or of a mixture of solid particulate burnt lime or burnt dolomitic lime, or both, with iron blast furnace slag in an amount effective to serve as a flux promoting the melting of said lime and dolomitic lime, and wherein said iron blast furnace slag consists essentially of the following in percentages by weight based on the total weight of the slag:
- CaO:
- about 30 to about 45%
- SiO.sub.2 :
- about 35 to about 45%
- MgO:
- about 5 to about 15%
- Al2O.sub.3 :
- about 5 to about 15%
- together with about 0 to 2% each of P, Na, K and Mn, about 1 to about 2% S, and about 1 to about 4% Fe.
Dependencies are inferred from the claim text.