Influence of temperature and equivalent effect of added elements on the solubility, activity, and activity coefficient o
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- - r N 2 = l atm
.
AS '
AH'
. . . 4.575 4.575
1
T
to yield the following equation log %Nalloy, T, PN2 = 89 log PN~ -- 1 . 2 9 0 - 4.575 kT
3746
which r e q u i r e s only the knowledge of a l l ' , as a c o m p o s i t i o n dependent v a r i a b l e , for p r e d i c t i o n of n i t r o g e n solubility under any condition. The c a l c u l a t i o n of the AH' t e r m can be done by m e a n s of a r e c e n t l y developed e q u i v a l e n c e method. T h i s i n v o l v e s t r a n s f o r m a t i o n of the conc e n t r a t i o n s of all e l e m e n t s X i p r e s e n t , e . g . , in a m u l t i c o m p o n e n t m e l t into an e q u i v a l e n t c a r bon c o n c e n t r a t i o n %[C]N ~ i ) by m u l t i p l i c a t i o n of the c o n c e n t r a t i o n of each by an equivalence factor belonging to that e l e m e n t and d e r i v e d f r o m data on t e r n a r y s y s t e m s F e - N - X i . By s u m m i n g all % [ C ] ~ i ) v a l u e s to an e q u i v a l e n t total c a r b o n c o n c e n t r a t i o n % [ C ] ~ ) the final AH' value ( e x p r e s s i n g the c o l l e c t i v e influence of all e l e m e n t s ) can be r e a d from a single " c a r b o n " r e f e r e n c e c u r v e , e s t a b l i s h e d a f t e r c o n s i d e r a t i o n of many F e - N - X i s y s t e m s .
EXTENSIVEinvestigations have been made on the influence of alloying elements on the solubility of nitrogen in liquid iron-rich solutions at 1600~ 1-27 The effect of temperature at constant melt composition has also received increasing attention in recent years, see T~ble I, col. 5. Moreover, various attempts have been made to use these experimental values for the development of a single equation which can describe thermodynamically the influence of temperature as well as alloying elements on the solubility or activity coefficient of nitrogen in liquid iron. Almost without exception the evaluation in these investigations have been performed on a weight percent basis. The prediction of nitrogen solubility by means of thermodynamic-energetic values, however, is necessarily based on mole fractions. For reasons of comparison as well as in order to be able to estimate the e r r o r introduced systematically into the calculations by an evaluation on weight percent basis as done in the cited investigations it is necessary in the beginning to discuss some means for conversion.
HANS -D. KUNZE, formerly Max Kade Fellow for 1967-68 at the Department of Mineral Engineeringand the Center for Materials Research, Stanford University, Stanford, Calif. and EBERHARD SCHORMANN are Dr.-Ing, Teaching and Research Assistant and Dr.-Ing., Professor, respectively, Institut f~r Giessereiwesen,Technological University of Clausthal, Germany. N. A. D. PARLEE is Professor of Extractive Metallurgy, Stanford University. Manuscript submitted May 17, 1968. METALLURGICALTRANSACTIONS
The s t a n d a r d r e a c t i o n for the d i s s o l u t i o n of n i t r o gen in liquid i r o n or an alloy can be w r i t t e n as 89
= S (in the alloy)
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