Desulphurization of Molten Steel in RH-Degasser by Powder Blowing to Produce Non Grain Oriented (NGO) Silicon Steel

oleh Zulfiadi Zulhan, Christian Schrade, Yelsi Ade Patriona

Penerbit - Institute of Technology Bandung, Technometal GmbH

Kategori - Novel Am

Steel desulphurization of molten steel during RH treatment by addition of Ca-based fluxes through powder injection lance as well as through alloying vacuum hopper system were investigated by reasearchers in 1990-s. However due to the reducing of refractory’s service life of RH plant, particularly in snorkel and bottom part of RH vessel, this technique is not a common practice in steel industry. Currently, the steel grade to be produced is very strict in term of chemical composition in order to obtain certain physical and mechanical properties of steel. Impurities, such as sulphur and phosphor, shall be as low as possible. For some non grain oriented (NGO) silicon steel grades, it is required that carbon and sulphur contents are less than 30 ppm and 20 ppm, respectively. Decarburization to produce steel containing less than 30 ppm carbon as well as addition of silicon according to final specification (e.g. 2 - 3.5% silicon content for NGO silicon steel) could be accomplished during vacuum treatment on RH plant. To reduce total treatment time as well as to prevent carbon pick-up during subsequent desulphurization step, therefore, it is suggested to continue the desulphurization process on RH plant directly after decarburization and alloying additon. In this paper, kinetic model to predict sulphur content during RH treatment by powder injection which were introduced by previous reaserchers are reviewed and improved. The model is then combined into decarburization and alloying addition in order to provide temperature prediction for the whole RH process, to estimate total treatment time as well as to integrate in the production line. Injection technique of Ca-based fluxes powder is also described in this paper.

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