| 摘要 |
PURPOSE:To extend the service life of a lance for stirring a molten metal and to reduce the cost ratio thereof by using the lance for refining and running the gas cooled to an ordinary temp. or below in succession to the treatment thereby cooling the lance. CONSTITUTION:A lance 3 for stirring a molten metal which consists of a metallic pipe 7 having a gas passage hole 7 and covering refractories 8 enclosing the outside circumference thereof is immersed in the molten iron 4 in a ladle 1 and gas bubbling 6 is generated, whereby the molten iron 4 is stirred and refined. The gas cooled to an ordinary temp. or below is kept run in succession even after the end of the treatment to cool said pipe 7. The difference in the thermal expansion between the refractories 8 and the pipe 7 is thus decreased and the generation of the crack and stripping in the refractories 8 and the bend, etc. of the pipe 7 is prevented. Air, Ar, N2, CO2 or the like is cooled by being passed through a cooling tank filled therein with liquefied gas and is adequately used at a flow rate of 200-5,000Nl/min as the above-mentioned cooling gas. |
