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The purpose of this research is to study DeMn treatments for the manufacture of low (less then 500 ppm) Mn steels in the (EAF-LF-VDU) production line. A series of tests have been carried out on this line in order to bring the Mn content below 500 ppm in the cheapest possible way by electric furnace treatment only or by ladle treatment possibly following an electric furnace treatment. However, both practices do not guarantee by themselves that the Mn content in the bath will be lower than 500 ppm. Therefore, a new practice has been worked out to be implemented in two steps, namely a partial demanganizing treatment (ie single-slag process, being cheaper than double-slag process) in EAF followed by a final ladle treatment. For the final treatment, the following possibilities have been taken into consideration:

- R: addition of lime only (2 kg/t);
- 1: addition of lime (2 kg/t), silica sand (2 kg/t) with SiO(2) equal to 80% and iron ore (2 kg/t) with Fe(2)O(3) equal to 65%;
- 2: addition of lime only (2 kg/t), quartzite (3.25 kg/t) with SiO(2) equal to 98% and iron ore (3.25 kg/t) similar to that of treatment 1).

The statistical analysis of data showed that:

- Practice R allows a final Mn content of 500 ppm;
- Practices 1 and 2 allow to go below 500 ppm.

Practice 1, applied in 33 heats, gave a 89% probability (average Mn content = 340 ppm from an EAF average content of 830 ppm). Practice 2 applied in 23 heats, gave a 97.8% probability (average Mn content = 280 ppm from EAF average content of 830 ppm). This data show that, when the Mn content is to be lower than what obtained with treatment, it is necessary to select slags furtherly by FeSi and carbon wire alloy addition. The minimum Mn content at the end of FeSi and C addition has been 100 ppm. n 100 ppm.

Additional information

Authors: CAPODILUPO D, Unità di ricerca di Terni, Centro sviluppo materiali (IT)
Bibliographic Reference: EUR 16694 IT (1997) 61pp., FS, ECU 11.50
Availability: Available from the (2)
ISBN: ISBN 92-828-0843-2
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