| 摘要 |
A method for refining a low nitrogen steel is provided to reduce the degassing process time in a vacuum degassing process, accomplish cleaning of molten steel, and improve quality and productivity of molten steel. In a method for refining a low nitrogen steel containing not more than 50 ppm of nitrogen, the method comprises the steps of: maintaining the speed of an IDF(Induced Draft Fan) to 330 revolutions per minute before starting a blowing operation; maintaining the speed of the IDF to 75% of the maximum speed of the IDF for 30 seconds right after starting the blowing operation; sealing a converter with a skirt after a lapse of 30 seconds after starting the blowing operation, and automatically controlling the IDF by a hood pressure according to the flue gas amount; lifting the skirt from the converter after a time point when 95% of the blowing operation has been completed; and controlling the speed of the IDF to 60 to 75% of the maximum speed of the IDF. The method comprises the step of controlling the speed of the IDF to 40 to 55% of the minimum speed of the IDF in the blowing operation. After performing the step of starting the blowing operation, the method further comprises the steps of: recovering the flue gas when flue gas contains at least 19% of CO, and a gas storage tank has a level of at least 84%; and completing the recovery of the flue gas if it is after a time point when 90% of the blowing operation has been completed, or the gas storage tank has the level of at least 92%. |
