Cover powders
Reactive layer:
Appication of a reactive calcium-aluminate slag TO the tundish surface offers optimum protection against re-oxydation (kinetic reaction formulation mode) by achieving the quickest possible melting speed and sealing of the bath surface. Upon reaction of CaO with Al2O3 at approximately 1550 °C no further binding heat from the tundish is required. In fact, the opposite occurs: heat is released that further accelerates the melt open process. The quantity of calcium-aluminate slag to be added is about 0.5 - 1 kg per ton of steel, depending on the process and the sequence length.
Insulating layer:
Since the slag itself provides no thermal insulating effect, it is usually covered with carbonaceous rice ash. Here, however, the high SiO2 content (> 90%), which over the sequency length induces an increase in SiO2 in the liquid slag phase, may have a negative impact. This means an increased reduction potential in the boundary phase slag-steel and thus the danger of non-metallic inclusions in the form of Mikro-alumina. This can be countered with the FOR MET 4.1 insulating layer developed in WEERULIN laboratory. It is a quartz-free, alkaline insulating cover, whose SiO2 content is mineralogically bound and below 5%. Its similarity to the chemical-mineralogical composition of calcium-aluminate slag provides perfect synchronization of the system. The insulating layer can take up ladle in-line slag without annealing or melting. Formation of clods or covers is not expected with calm bath levels.
| Sector | Type | WEERULIN Product | Characteristics |
|---|---|---|---|
| surface | reactive layer | FOR MET 3.1 | reactive calcium alumina slag |
| surface | insulating layer | FOR MET 4.1 | SiO2-reduced basic insulating powder |
| surface | one-layer cover | FOR MET 5.1 | SiO2-reduced reactive slag, insulating powder |