Abstract The invention relates to the refining of steel and has particular reference to the refining of steel by a process in which a stream of hot gases is directed onto the upper surface thereof. The invention particularly provides for a method of controlling the manganese content of the melt at turn-down of a steel refining process by at least a two stage process in which the refining is carried out using a gas stream comprising the products of combustion of a fuel and uncombined oxygen by varying the proportions of combustion products to uncombined oxygen in a first stage in which the gas stream is relatively poor in uncombined oxygen and in a subsequent or second stage in which the gas stage is relatively rich in uncombined oxygen and varying the duration of the first stage so that with a relatively long first stage a low manganese reversion is obtained and by providing a relatively short first stage a high manganese reversion to the melt at turn-down is obtained.
The method of controlling the manganese reversion set forth in claim 1 wherein said first stage comprises the formation of a slag and said second stage provides the major decarbonization of the melt.
Claim 2
Dependent Claim
52 words
The method of controlling the manganese reversion set forth in claim 2 wherein maximum manganese reversion is provided by regulating the time of said first stage to obtain a cool slag formation and wherein minimum manganese reversion is provided by regulating the time of said first stage to obtain a hot slag.
Claim 3
Dependent Claim
38 words
The method of controlling the manganese reversion set forth in claim 1 wherein said refining process includes a third terminal refining and correction stage wherein the gas stream is low in uncombined oxygen and high in combustion products.
Claim 4
Dependent Claim
54 words
The method of controlling the manganese reversion set forth in claim 1 wherein said refining process, said first stage includes an excess of from about 25 to 300 percent oxygen of that theoretically required for complete combustion and said second stage includes an excess of about 1,000 to 1,300 percent required for complete combustion.
Claim 5
Dependent Claim
36 words
The method of controlling the manganese reversion as set forth in claim 1 wherein said first stage is from 8 to 10 minutes for minimum manganese reversion and 4 to 6 minutes for maximum manganese reversion.