Production process and damage mechanism of tundish sizing nozzle

 Tundish sizing nozzle is used as the key refractory material for billet continuous casting, which controls the flow of molten steel, determines the drawing speed of the billet in continuous casting, and is a necessary condition to ensure the normal operation of continuous casting. In addition to cracking, blockage and falling off of the zirconic sizing nozzle, it is also required that the diameter expansion speed should not be too fast to meet the requirements of long-term casting. Damage to the sizing nozzle. The damage process of the oxidized sizing nozzle is a complex physical and chemical effect of its interaction with steel slag and molten steel at high temperatures.

The specific damage mechanism is divided into two categories:

(1) Physical damage:

During the use of the zirconium sizing nozzle, due to the large temperature difference between before and after pouring steel (the pouring temperature of the steel is 1540C, uneven heating, a huge thermal stress is generated inside the nozzle, resulting in micro cracks in the nozzle. The generation of slag reduces the strength and erosion resistance of the nozzle, and provides convenience for the penetration and erosion of molten steel and steel slag into the sizing nozzle.?

(2) Chemical damage:

① Desolubilization of stabilizer in zirconia. The best raw material for preparing zirconium sizing nozzles is partially stabilized zirconia. In the process of casting steel, stabilizers (calcium oxide, magnesium oxide, etc.) will react with molten steel and inclusions (such as Fe, Mn, Si, etc.) in molten steel. A low melting point oxide melt is formed, which flows away with the molten steel, and the aluminum oxide solid solution is destabilized and decomposed due to the desolubilization of the stabilizer. As a result, the quantity of cubic phase aluminum oxide is reduced, and small particles of monoclinic phase are lost with molten steel.

② Infiltration and erosion of molten steel and steel slag.

 

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Article Source:Production process and damage mechanism of tundish sizing nozzle
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