Calcium aluminate flux is used for steel refining in integrated plants based on iron ore processing as well as in mini-mill based on scrap recycling. The main use is in secondary metallurgy in combination with lime, ferro-alloys and possibly other minerals.
This secondary metallurgy slag is an oxidised liquid which floats on the surface of liquid steel (1 600 °C) and which, like a sponge, absorbs the impurities consisting mainly of sulphur and non-metallic inclusions. The design of the slag is a critical step impacting the efficiency of the steel refining process. The most common flux in secondary metallurgy processes is calcium fluoride (CaF2) which facilitates the reaction of reagents in order to get a liquid. However, it does not contribute to the slag composition. Another major disadvantage is that CaF2 is aggressive for the refractory lining. Calcium fluoride also has a harmful impact on the environment when the slag is valorised as its F content could be leached creating a risk of ground water pollution.
The calcium aluminate flux combines two major functions: it facilitates the slag formation and contributes to its optimised composition by adjusting the Al2O3/SiO2 ratio. The calcium aluminate flux therefore maximises the efficiency of the steel refining process by:
improving steel quality,
increasing productivity,
reducing costs,
protecting environment.
The Kerneos offer includes the following ranges:
The LDSF® range: proven products used for more than 25 years by many steelmakers with all types of metallurgical production tools (LF, VD, VOD, RH, tundish):
- LDSF® RG: a worldwide reference, very flexible thanks to its low melting temperature (< 1 325°C) which makes it suitable for a wide variety of steels,
- LDSF® LT: a low titanium calcium aluminate flux with a very low content of impurities, especially designed for high quality steel with Ti limitation such as bearing steels.
The OPTIMET™ product line: innovative calcium aluminate fluxes enriched in MgO (13%), designed to improve the lifetime of the ladle lining and to give the usual benefit of a calcium aluminate flux:
- OPTIMET™ RG: a regular product suitable for a large range of steel grades.
- OPTIMET™ SI: a flux with a low SiO2 content specially developed for steel grades with low Si specifications
- OPTIMET™ AL: a product with higher Al2O3 content allowing lower specific consumption for refining operations when higher melting point and SiO2 content are not critical.
LDSF® and OPTIMET™ are preferably added as first additions when the ladle is filled with the steel. This early addition enables the rapid formation of a fluid and reactive slag and an efficient dissolution of the other slag components. It also maximises the advantages of the MgO when OPTIMET™ Flux are used thus protecting the refractory lining during the first moments of secondary metallurgical process when corrosion is at its highest.
The calcium aluminate flux of the LDSF® and OPTIMET™ product lines is manufactured in a quality management system environment, certified according to ISO 9001 standards.
