5 Interesting Facts About Tundish Refractories

A tundish is a crucial component of the continuous casting process in steelmaking, positioned between the ladle and the casting molds. It regulates the flow of molten steel into the molds. Given the extreme temperatures, tundish refractory linings are engineered to withstand thermal shock, minimize heat loss, prevent oxidation, and resist erosion and corrosion, all while avoiding contamination of the liquid steel with impurities.

Here are five interesting facts about tundish refractory linings:

1. The Tundish Has a Permanent and Disposable Lining  

A tundish is lined with a permanent layer of refractory bricks or monolithics, and it also includes a disposable lining. The disposable lining serves as a thermal and chemical barrier, protecting the permanent liner while maintaining the temperature of the molten metal. This lining needs to be replaced after one or more heats of molten steel. The refractory lining, which is sprayed on between heat cycles, features a unique phosphate binder/deflocculant system that cures with either residual heat or ambient temperature after cold starts.

2. Phosphates as Binders and Deflocculants in Refractories  

Phosphates play a critical role in refractories by aiding in strength development, dispersing ingredients throughout the mix, and allowing for control over set and working times. Our phosphates are specifically engineered to enhance flowability, prevent oxidation and out-gassing, and improve strength development at elevated temperatures.

3. Sodium Metasilicate 9 MOL: A Low-Temperature Binder  

Sodium Metasilicate 9 MOL is highly stable at ambient temperatures and begins releasing significant amounts of water around 80°C, making it an effective quick binder for single-component systems at relatively low temperatures. It has proven highly successful in blends designed for low-temperature strength development. Beyond enhancing strength, the water release triggers reactions in other additives within the refractory mix.

4. Steel and Slag Residue in the Tundish Forms a "Skull" That Must Be Removed  

In addition to extending the life of the permanent tundish lining, the disposable lining simplifies the removal of the tundish "skull," a hardened residue of steel and slag. This residue is removed in a process known as "deskulling," after which it can often be recycled back into the continuous casting process. Our phosphate additives prevent oxidation within the skull, ensuring that no harmful impurities are reintroduced into the material.

5. The Output of Continuous Casting: Billets, Blooms, and Slabs  

The continuous casting process typically produces billets, blooms, or slabs, which are considered semi-finished products. These materials serve as the foundation for various steel products, eventually being processed into items such as rails, pipes, wire, rods, or tubes.