Structure and Working Principle of the Porous Nozzle Well Block for a Tundish

In the continuous casting process, the tundish is no longer viewed merely as an intermediate vessel for buffering, storing, and distributing molten steel—or for facilitating multi-heat continuous casting—but is now recognized for its significant metallurgical functions. Currently, combinations of flow-control devices, such as baffles, dams, and turbulence inhibitors, are widely employed to optimize the flow of molten steel within the tundish. These measures help minimize "dead zones," extend the residence time of the molten steel, and promote the flotation and removal of non-metallic inclusions, thereby purifying the steel. While such flow-control configurations are sufficient for the production of conventional steel grades, they struggle to effectively remove inclusions smaller than 50 μm, which is a critical requirement for the production of specialty steels and "clean" steels. To further enhance the metallurgical performance of the tundish, researchers have explored various advanced technologies, including molten steel filtration, heating systems, and gas-curtain baffles. One company has developed a specialized nozzle-well block for the tundish that incorporates an argon-injection feature. By creating an annular gas curtain around the stopper rod—positioned just above the nozzle—this system aims to facilitate the removal of non-metallic inclusions (improving cast-slab quality), prevent nozzle clogging caused by the accumulation of solid particles, and ensure the smooth, uninterrupted operation of the continuous casting process.

Structure of the Purging Nozzle Well Block for a Tundish

Several gas-permeable elements are embedded within a standard tundish nozzle well block. Each gas-permeable element consists of a high-temperature-fired ceramic rod containing a uniform distribution of tiny, straight, continuous channels. The lower sections of these elements are interconnected via an annular passage, ensuring they remain in open communication with one another. This annular passage is linked to a gas inlet pipe, which is connected to a gas source to supply the gas required during operation.

Working Principle

Inert gas is introduced into the tundish gas-permeable nozzle block, passing through tiny, straight channels within a ceramic element and into the tundish. As the gas rises around the stopper rod, it forms an annular gas-curtain barrier above the pouring orifice. The numerous micro-bubbles within this curtain collide with and capture non-metallic inclusions present in the molten steel; these bubbles then carry the inclusions upward, facilitating their removal and thereby enhancing the cleanliness of the molten steel.

When used in conjunction with flow stabilizers and slag-retaining walls, the tundish gas-permeable nozzle block is highly effective at removing non-oxide inclusions—capable of eliminating over 90% of such inclusions smaller than 50 μm—thereby purifying the molten steel and improving the quality of continuously cast billets. Furthermore, the use of these gas-permeable blocks helps prevent the clogging (or "flocculation") of submerged entry nozzles during the casting of aluminum-killed steel, ensuring the smooth operation of the continuous casting process.