Currently, most steel billets worldwide are produced using continuous casting technology, making the service life and performance of refractory materials for sizing nozzles crucial. Zircon bricks, zirconia sizing nozzles are widely used in tundishes for the continuous casting of small square billets. The performance of the nozzle directly affects the duration of continuous casting.
Sizing nozzles are the nozzle bricks in a sliding gate system used in steel mills when casting square billets. The sliding gate system took nearly 80 years from conception to industrialization, primarily due to inadequate material quality, despite its significant advantages over stopper rod systems. Zirconia nozzles exhibit good resistance to corrosion from molten steel and slag, and are typically made from high-purity zircon, CaO-stabilized ZrO2, and industrial-grade zirconium oxide.
The most critical components of a sliding gate system are the slide gate brick and the nozzle brick embedded within it. The system typically consists of upper and lower slide gate bricks and nozzle bricks. Casting begins when the upper and lower nozzle bricks align. The upper nozzle brick is mounted at the bottom of the ladle and remains stationary along with the upper slide gate brick, while the lower nozzle brick slides along with the lower slide gate brick, thus controlling the steel pouring process. The upper nozzle brick is immersed in molten steel for a long time and is relatively difficult to replace, requiring high-quality products and a long service life. The lower nozzle brick is mainly used to control the steel pouring speed and quality, and has lower service life requirements; its lifespan can reach eight hours or longer.
