A Tundish Covering Flux looks like a simple product: powder in a bag, spread on top of the steel. In practice, three variables decide whether it works, and choosing them in the wrong order is the most common reason a plant concludes that "Tundish Covering Flux does not work for us".
Start with melting behaviour. The Tundish Covering Flux has to melt into a continuous liquid layer at your actual tundish temperature, not at a laboratory reference temperature. If it stays solid, it insulates but does not absorb inclusions. If it melts too thin, the layer breaks up and reoxidation starts again. The target is a layer that stays liquid but viscous through the whole casting sequence.
Second, particle size distribution. This has to match how the material is added. Manual spreading tolerates a wider distribution and some fines. Machine feeding through a hopper does not — fines cause bridging and the feeder stops. Granular Tundish Covering Flux exists for exactly this reason.
Third, addition rate. Too little and you get bare patches where the steel is exposed. Too much and you are paying for material that sits on top doing nothing while the layer gets thick and hard to remove. A practical starting point is to keep a continuous layer of roughly 20 to 30 mm and adjust from there based on what you see at the tundish.
One more thing worth checking before you change suppliers: how the Tundish Covering Flux behaves in the last third of the sequence. Many products work well early and then break down late, when the tundish is nearly empty and temperature control matters most. Ask for a trial batch and watch it to the end.
Related product
Covering Agent
Spread on the molten bath, a Covering Agent melts into a continuous protective layer that holds heat in, keeps air out and absorbs the inclusions that rise to the surface.
