2004 Volume 90 Issue 6 Pages 422-428
An attempt was made to utilize H2 for the secondary refining in steelmaking process, because H2 would react with [O] and [S] without any inclusions and accelerate the nitrogen removal from the molten steel. The 20 kg of plain carbon steel was melted in the induction furnace. The gases of Ar, N2 and H2 were injected from the bottom. The temperature was ca. 1880K. The gas flow arte was 2.50 and 3.33×104m3/s (stp). The results are summarized as follows.
(1) The rate of nitrogen remove by H2, injection was 1.5 to 2.6 times larger than by Ar injection. The mechanism was (i) reduction of poisoning effect of [O], (ii) acceleration of mass transfer in the gas phase and (iii) finer bubble dispersion due to Marangoni effect.
(2) The deoxidation proceeded down to 6.0 ppm by H2 injection. But this result was the sum of deoxidation by [C] and H2. Taking into account of oxygen penetration from the outside of furnace, deoxidation by H2 was evaluated. The H2 bubbles leave the molten steel far from water vapor saturation. One reason is that the deoxidation process should be controlled not only by mass transfer in the molten steel but also that in gas phase. The other reason is the shallow molten steel bath.
(3) Neither desulfurization nor methane formation occurred by H2 injection.
(4) The [H] content decreased down to less than 1 ppm by Ar injection for 420 s.
