| 摘要 |
PROBLEM TO BE SOLVED: To prevent the damage of a nozzle inner hole body without developing the positive pressure in a slit by executing a second preheating while supplying inert gas after executing a first preheating in a specified time under the atmospheric opening state of a gas supplying tube communicated with the slit part of the nozzle. SOLUTION: The inert gas such as Ar introduced from the metal-made screwed gas supplying tube 1, is supplied through the gas blowing slit 3 into the refractory-made inner hole body 4 arranged on the inner wall of the nozzle refractory 2 made of alumina-graphite, etc., and gas film is formed on the inner wall of the nozzle to protect the nozzle from passed molten steel by turning to a non-contacting state. In this gas blowing type immersion nozzle for continuous casting, before casting, this nozzle refractory 2 is preheated to prevent the spalling. At this time, the gas supplying tube 1 is opened to the outer part of the atmosphere or reduced in the pressure, and preheated at 400-600 deg.C by (t) min shown with 0.357A<=t<=30 (wherein, A is the refractory thickness (mm) from the slit part 3 to the outer surface) and successively, preheated to >=1100 deg.C while supplying the inert gas.
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