The long nozzle (or protection tube) is used between the ladle and the tundish to protect the molten steel from secondary oxidation and prevent the steel flow from splashing. Otherwise, cracking, breaking and other accidents are prone to occur when pouring. It has strong adaptability to steel types and good corrosion resistance. There are long nozzles that can be used without baking, which are called emergency backup nozzles. The long nozzle is installed under the ladle. It is an Al2O3-C circular tube channel for molten steel to be injected from the ladle into the tundish. It plays a role in guiding and preventing oxidation and splashing of molten steel. It is an important functional refractory material for realizing molten steel protection casting to improve the quality of steel billets. Its use will directly affect whether the entire continuous casting process can proceed normally.
Long Nozzle Advantages:
The shroud is a refractory material connecting the ladle and the tundish. The shroud has the functions of stabilizing the flow state of molten steel, preventing oxidation of molten steel, and preventing splashing of molten steel. The baking-free shroud has the advantages of good thermal shock resistance, strong resistance to molten steel scouring, and good slag resistance. At the same time, it is quickly promoted for its convenient operation and greatly improved working conditions.
Long Nozzle Application:
Quartz long nozzle is earliest used, which has very low linear expansion rate or nearly no thermal expansion, excellent thermal shock resistance, but it’s corrosion resistance is weak, especially for the casting of special steel such as high Mn steel, the service life is even shorter. With the developing of continuous casting technique, especially the casting of special steel, quartz long nozzle can also have unfavorable effect on steel quality, so new type of alumina carbon long nozzle is developed. Alumina carbon long nozzle’s service life is significantly longer than quartz long nozzle, but alumina carbon long nozzle’s main components are corundum, mullite, graphite and molten quartz, although mullite and quartz can large scale increase thermal shock resistance, the corrosion resistance to Mn steel and other special steel is not very good.
