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The project aims to define an industrial process for EAF steelmaking, leading to 40 ppm nitrogen in steel before tapping. Both fundamental and industrial investigations carried out consisted of:

- evaluating the nitrogen removal capacity by BaO and TiO(2)-based slags (RWTH, laboratory experiments)
- studying the mechanisms of nitrogen content evolution (IRSID, 6t pilot furnace)
- determining the influence of industrial parameters on the nitrogen content (IRSID and Sidenor I+D, tests performed in Unimetal Gandrange and Sidenor Vitoria's mills).

Nitrogen can be removed with TiO(2)-based slags and a high amount of aluminium in steel. TiO(2) is first reduced by aluminium, then titanium nitrides form and move into the slag phase. Results are in good agreement with thermodynamics.

Trials on a 6t pilot furnace confirmed that decarburisation is the main way to promote nitrogen removal. As long as the carbon content in steel is higher than 0.1 %, flushing the steel bath with CO decreases the nitrogen content with no apparent lower limit. Nevertheless, the decarburation flow rate must be high enough to limit air intakes.

Industrial trials showed that it is possible to reach nitrogen contents of around 40 ppm in steel by:

- charging a high quantity of low nitrogen coal and increasing the amount of oxygen gas accordingly;
- promoting a high decarburisation rate especially towards the end of the heat;
- having a good slag foaming practise;
- ending the heat with a final decarburisation phase, power off, keeping the steel carbon content above 0.1 %. t above 0.1 %.

Additional information

Authors: ZBACZYNIAK Y, CREAS, Ascometal Unimetal, AmnÚville (FR);MAILHAN J C, IRSID MAIZ, Maiziþres-lþs-Metz (FR);NEUSCHTZ P, RWTH, Aachen (DE);STORSBERG L, RWTH, Aachen (DE);MOLINERO J, SIDENOR, Basauri-Vizcay (ES)
Bibliographic Reference: EUR 19349 EN (2000) 105 pp., EUR 16
Availability: Available from EUR-OP sales agents
ISBN: ISBN 92-828-9237-9
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