Method of refining steel

Abstract

A method for refining an iron-base metal such as pig iron which contains minor amounts of elements including silicon, manganese, phosphorus, carbon, sulfur, and other incidental impurities, characterized by the steps of containing molten iron-base metal in a metallurgical vessel, heating and oxidizing the molten metal to cause chemical reactions to remove excessive contents of the said elements, adding solid lime and a mixture of fluorspar and slag conditioners of relatively high basicity (lime-to-silica ratios of 2.5 to 4.0) which conditioners consist essentially of oxides of selected metals including iron, manganese, silicon, magnesium, and calcium, and which conditioners have a melting point of from about 2,000 to 2,800 F, and continuing to heat while oxidizing the mixture of the molten metal, slag conditioner, fluorspar and slag-forming materials until said minor amounts of elements are reduced to the desired percentages, and are retained in the slag formed. More specifically, the function of the slag-conditioner is to eliminate the encapsulation of large particles of lime by dicalcium silicate and thereby more rapidly taking the lime into solution. The function of the mixture of fluorspar and slag conditioner is to promote more rapid solution of the solid lime than is obtainable with the use of either fluorspar or slag conditioner alone.

What is claimed is: 
     
       1. A steel refining process for facilitating the solution of solid lime by inhibiting the formation of dicalcium silicate, comprising the steps of a. heating and oxidizing a molten iron-base metal,   b. adding solid burnt lime to the molten iron-base metal.[.,.]. and   c. .[.adding material of high basicity and of a melting point lower than that of solid burnt lime together with a mixture of fluorspar and oxides of iron, manganese, silicon, magnesium, and calcium, which oxides have melting points of from about 2,000° to 2,800° F, to provide a slag devoid of encapsulated solid bodies of burnt lime.]. .Iadd.adding fluorspar and slag conditioners of high basicity and of melting points lower than that of solid burnt lime which slag conditioners comprise oxides of iron, manganese, silicon, magnesium, and calcium, and which slag conditioners have melting points of from about 2000° to 2800° F, to provide a slag devoid of dicalcium silicate encapsulated solid bodies of burnt lime and fluorspar. .Iaddend.   
     
     
       2. The method of claim 1 in .Iadd.which .Iaddend.step (a) .[.of which.]. comprises directing a stream of pressurized oxygen containing gas onto the surface of the molten metal. 
     
     
       3. The method of claim 1 in which the mixture consists essentially of, by weight percentage, from about 0.1 to 99.9 percent fluorspar and from about 0.1 to 99.9 percent metal oxides. 
     
     
       4. The method of claim 3 in which the mixture consists essentially of, from about 5 to 95 percent fluorspar, and from about 5-95 percent metal oxides. 
     
     
       5. The method of claim 4 in which the mixture consists essentially of from about 10-90 percent fluorspar and from about 5-95 percent metal oxides. 
     
     
       6. The method of claim 1 in which the mixture consists essentially of for each ton of steel, 2.5 lbs. of fluorspar and 7.5 lbs. of metal oxides. 
     
     
       7. The method of claim 1 in which there is from about 5-50 percent iron oxide, from about 2-20 percent manganese oxide, from about 2-15 percent magnesium oxide, from about 20-50 percent calcium oxide, and from about 8-25 percent silicon oxide. 
     
     
       8. The method of claim 7 in which there is from about 15-30 percent iron oxide, from about 5-12 percent manganese oxide, from about 8-10 percent magnesium oxide, from about 30-48 percent calcium oxide, and from about 10-16 percent silicon oxide. 
     
     
       9. The method of claim 8 in which there is about 25 percent iron oxide, about 10 percent manganese oxide, about 9 percent magnesium oxide, about 42 percent calcium oxide, and about 14 percent silicon oxide.