Solubility of nitrogen and carbon in ESR type slag
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ave been reported previously.1'3 Further, the Ca, At, F contents were determined in o r d e r to check whether changes in the Ca : A1 : F ratios occurred during the long reaction times. The typical concentration time curves are shown in Fig. 1. Zero point of the time s c a l e is at the time when the carbon monoxide atmosphere was changed to the N2-CO-Ar gas mixture. In the upper d i a g r a m the contents of total nitrogen (N)tota1 , of cyanide (CN) and of total carbon (C)total are shown. The acid soluble carbon contents are identical to total carbon contents, within the scatter of the points. Hence, the amounts of graphite in the slag are negligibly small, and there is no indication that a reaction of the type 2C22- = C4- + 3C (graphite) occurs in these s l a g s during solidification as has been found t o occur in CaC2-A1203 melts 8 S i m i l a r l y as in the previous experiments with CaO-A1203 melts ~-3 the curves for (C)total and (CN) have maxima. The decrease of the (C)total and (CN) contents at long reaction t i m e s is caused by the change in the Ca and A1 contents of the slag (see lower d i a g r a m s in Fig. 1). Due to volatilization of Ca containing species, the CaO/A1203 ratio of the slag becomes s m a l l e r with inc r e a s i n g time and this is associated with a slight dec r e a s e of carbide and cyanide solubilities. C o r r e s ponding curves were obtained for all the other experi-
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reGdi0n time, h KLAUS SCHWERDTFEGER and HANS G E O R G SCHUBERT are with Max-Planck-lnstitut for Eisenforschung GmbH, Metallurgical Dep a r t m e n t , Max-Planck-Strasse 1 , 4 0 0 0 Diasseldorf, Germany. Manuscript submitted March 14, 1977. METALLURGICAL
TRANSACTIONS B
Fig. 1--Typical results on compositional changes occurring in slag of nominal 32 wt pet CaO, 32 wt pet AI~O3, 36 wt pet CaF2 during equilibration with graphite and N2-CO-Ar gas mixture (1600°C, 1 atm). VOLUME 8B, DECEMBER 1977-689
m e n t s . T h e v a l u e s f o r (N)total, ( C N ) , (C)total, a s obt a i n e d in the v a r i o u s e x p e r i m e n t s , a r e l i s t e d in T a b l e I. T h e c h e m i c a l r e a c t i o n s for the f o r m a t i o n of n i t r i d e , c y a n i d e , a n d c a r b i d e c a n be w r i t t e n a s 3 0 2_ ( s l a g ) + 3 1 ~ C ( g r a p h i t e ) + } N2 ( g a s ) 3 = N 3- ( s l a g ) + ~ C O ( g a s )
[1]
1 0 2_ ( s l a g ) + 3 C ( g r a p h i t e ) + 1~ N2 ( g a s ) -2 =
CN- ( s l a g ) + 2 C O ( g a s )
02- ( s l a g ) + 3 C ( g r a p h i t e )
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Atm 0.05 0.10 0.25 0.25 0.50 0.05 0.05 0.05 0.05 0.05
Atm 0.50 0.50 0.50 0.50 0.50 0.40 020 0.95 O.65 0.20
Atm 0.45 0.40 0.25 0.25 0 055 0.75 0 0.3O 0.75
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