A sliding nozzle controls the flow of steel by adjusting the relative offset between two open-hole refractory bricks connected and assembled together via a sliding mechanism installed at the bottom of the ladle. The advantages of a sliding nozzle include improved working conditions, faster ladle turnover, reduced refractory material consumption, reduced ladle leaks, improved molten steel quality, and facilitated off-furnace refining.

Refractory Materials for Sliding-Slide Nozzles

The sliding nozzle consists of four refractory bricks: an upper and lower slide, and upper and lower nozzles. Each ladle of molten steel is poured through these slides and nozzles, placing stringent demands on them. Firstly, they must be strong enough to withstand the static pressure of the molten steel at high temperatures. Secondly, the sliding surfaces of the upper and lower slides must be extremely smooth and flat to ensure close contact and prevent molten steel leakage during pouring. Furthermore, they must be resistant to erosion, corrosion, and thermal stability to withstand rapid temperature changes, erosion from the molten steel, and erosion from slag.

Refractory nozzles for sliding gates are primarily used to control the flow rate and injection rate of molten steel. They require excellent erosion resistance at high temperatures, good high-temperature volume stability, and a certain degree of self-melting properties.

Facts that damage refractory nozzles for sliding gates include: erosion and erosion by molten steel and slag; cracking or breakage caused by sudden temperature changes; and melt loss caused by oxygen firing and pouring. The material must exhibit excellent erosion resistance. For example, high-aluminum or fused quartz nozzles are suitable for casting plain carbon steel; aluminum-carbon or magnesium-based nozzles are suitable for casting steels with high manganese content. To improve the nozzle’s thermal shock resistance, it should be installed in an iron sleeve to prevent cracking. Oxygen firing and pouring should be avoided as much as possible. High-aluminum, aluminum-carbon, and aluminum-zirconium-carbon nozzles have a service life of one and two to three times, respectively.