Processing materials

Calcium aluminates.

The production of high quality steel grades involves the use of precisely defined materials. Modern process management of steel plants minimizes uncontrolled slag carry over.
For the subsequent secondary metallurgical treatment of the steel melt, a synthetic slag must be formed. Calcium aluminates such as REFRAFLUX® S are used for this purpose.

Production
The raw materials for producing REFRAFLUX® S include raw bauxite and limestone or dolomite. REFRAFLUX® S is first granulated and then sintered in a rotary furnace. Therefore, REFRAFLUX® S is dust-free and practically free of carbon, crystal water, and adherent moisture.

Properties
Depending on the intended application, REFRAFLUX® S is produced in different fraction sizes. As a flux for the casting tundish we offer a granulation between 0.5 and 5.0 mm. A granulation of 5...15 mm is used in the field of secondary metallurgy.
REFRAFLUX® S is a microporous granulate. If the melt or slag is agitated, e.g. by purging, liquid slag or melt penetrates into the pores, whereby REFRAFLUX® S is quickly dissolved.
By combining granulation and subsequent sintering it is possible to produce calcium aluminates with widely differing compositions – even in accordance with individual customer specifications.

10 % < CaO < 53 %
25 % < Al2O3 < 60 %
1 % < MgO < 20 %

Secondary phases:
SiO2, Fe2O3, TiO2, etc.

Desulphurisation with REFRAFLUX® 4842 S
Results of 1081 heats
Application
The main field of application is secondary metallurgy. In particular, calcium aluminates are used for desulphurization in the ladle furnace. Hereby, a highly reactive slag is formed very quickly. Subsequently, the slag is saturated with lime, e.g. by adding slag lime, which results in optimum desulphurization.

Another field of application of pre-reacted calcium aluminate is the production of hydrogen-sensitive steel qualities, such as heavy plate grades. In continuous casting plants, REFRAFLUX® S is used as a slag former ("sandwich layer") in the tundish. As a liquid top slag, REFRAFLUX® prevents contact of the melt with the atmosphere, reduces a possible reaction between the melt and acid covering materials such as NERMAT®AF, and binds rising oxide inclusions.
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