| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for starting a gas-exhaustion in a vacuum-degassing apparatus by which air can surely be prevented from flowing into the vacuum-degassing vessel when using a pre-exhaustion of gas for shorteninga period of time for pressure reducing the inside of the vacuum-degassing vessel to a predfetermined pressure. SOLUTION: The vacuum-degassing apparatus 10 includes; the vacuum-degassing vessel 14 disposed at the upper part of a ladle 13 and dipped into molten steel at 200-500 mm in the ladle part 14a; a vacuum-exhaust gas device for sucking the air in the vacuum-degassing vessel 14; exhaust gas pipings 16, 20 and a pressure-equalized piping 18 for connecting the vacuum-degassing vessel 14 and the vacuum exhaust gas device; an exhaust gas main valve 17 arranged in the pressure-equalized piping 18 and the exhaust gas pipings 16, 20; an pressure-equalized valve 19 arranged in the pressure-equalized piping 18; and an elevating/lowering device 11 for elevating/lowering the ladle 13. After reducing the pressure in the exhaust gas piping 20 under the state of closing the exhaust gas main valve 17 and the pressure-equalized valve 19, the pressure-equalized valve 19 is opened and the pressure-reducing degree of≥0.04 MPa in the vacuum-degassing vessel 14 is reduced. In this case, the ladle 13 is elevated at the time point for opening the pressure-equalized valve 19 or at the time point before opening the valve. COPYRIGHT: (C)2010,JPO&INPIT
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