Saarschmiede GmbH Freiformschmiede (Völklingen, Germany):

Mohr S., Mag. Eng., Techn. Specialist, Processing Equipment

Technical University “Bergakademie Freiberg” (Freiberg, Germany):

Heller H.-P., Dr. Eng., Scientifi c Fellow, e-mail: heller@iest.tu-freiberg.de
Lychatz B., Dr. Eng., Scientifi c Fellow

ArcelorMittal Bremen GmbH (Bremen, Germany):

Franzen A., Dr. Eng.
Buhles T., Dr. Eng.
Unland E., Mag. Eng.,Technological Dept., Blast Furnace Shop
Janz J., Dr. Eng., Head of Blast Furnace Shop

Crystallization behaviour of blast furnace slags is important in the daily practice at the blast furnace. During a planned stoppage of the blast furnace, the remaining slag in the furnace can freeze. Like this it can provoke big problems for the new start of the blast furnace process afterwards. This is why crystallization behaviour of blast furnace slags was examined in this project during its period of continuous cooling. The used method was entitled as “Single Hot Thermocouple Technique” (SHT). With this method, melting and crystallization processes can be directly observed in optically transparent slags. The results of testings have displayed that SHT technique can be considered as rather good and precise method for measuring crystallization temperature. Owing to the eff ect on nucleation conditions in the slag sample via starter bar, it was possible to adapt labour experimental conditions to industrial conditions. It was shown that basicity and such components as Al₂O₃ and MgO have substantial influence on crystallization parameters. If MgO/Al₂O₃ relationship for slags is located in the range 1.2–1.5, such slags are characterized by the less crystallization temperature. It was displayed that slags SY11, SY12-1 and SY12 have demonstrated very low crystallization temperatures. Therefore, low basicity should be hold. Additionally, the researched slag compositions helped to obtain crystallization temperatures that are lower than eutectic temperature of iron crystallization.

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