To easily produce a steel having a low nitrogen content by using a specific shape of melting furnace and controlling the nitrogen content in oxygen used to a burner, at the time of molten steel by melting the raw material of steel scrap, etc., with the oxygen burner.
At the time of melting the steel scrap, etc., as the raw material with combustion heat of the oxygen burner 1, after preheating the steel scrap in a preheating part 3 at the upper part contacting with a contracted part 4 and a melting part 2 at the lower part in the melting furnace with high temp. exhaust gas from the melting part 2, while controlling the dropped quantity into the melting part 2 at the contracted part 4, the steel scrap is melted by the heat of the oxygen burner 1 with the combustion of heavy oil, etc., by using the oxygen as combustion assist gas in the melting part 2. In this case, the nitrogen concn. in the oxygen is made to ≤4% and also, lime, dolomite, silica, etc., are used and the molten steel surface is covered with new molten slag at early time and also, the invading quantity of the air into the furnace is restrained by the shape of the furnace. By this method, the molten steel having a low nitrogen content is produced.
SUWA TOSHIO
KOBAYASHI NOBUAKI
INOUE ATSUSHI
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