| 摘要 |
PURPOSE:To avoid the generation of a negative pressure in an OG type converter and to prevent the increase of the content of N in a molten steel by the intrusion of air therein by connecting a gas supply pipe to the mid-way of a waste gas hood of the converter and blowing gas not contg. N into the hood at the time when the flow rate of the waste gas is low at the end period of refining. CONSTITUTION:The molten iron in the OG type converter 2 is subjected to oxidation decarburization by oxygen top blowing refining using a lance 1 and is thereby refined to a steel. The waste gas contg. CO is sucked by a suction fan 4 and is thus recovered. The amt. of the CO-contg. waste gas by the oxidation of C is small at the end period of the decarburization refining and the negative pressure is developed in the converter by the suction of the waste g as by the suction fan 4, by which the external air is intruded into the converter. Then, the molten steel absorbs the N in the external air to becomes high nitrogen content. The gas such as CO, CO2 or Ar which does not contain N is supplied from the gas supply pipe 10 provided to the hood 3 to maintain the inside of the converter under the positive pressure at the end period of refining when the amt. of the waste gas is small in order to prevent the above-mentioned increase of N. The intrusion of the external air by the negative pressure is obviated and the increase of the content of N of the molten steel in the converter by the absorption of the N in the intruding external air is prevented. The low-nitrogen and low-carbon steel is thus produced. |
