Solubility of nitrogen in liquid Fe-Cr-Ni alloys containing manganese and molybdenum
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W A D A A N D R O B E R T D. P E H L K E
T h e nitrogen solubility in liquid F e - C r - N i alloys containing M o or M n w a s determined by the Sieverts' m e t h o d . T h e first and s e c o n d o r d e r m u t u a l interactions a m o n g nitrogen, c h r o m i u m , nickel, m o l y b d e n u m , and m a n g a n e s e in iron w e r e determined as a function of temperature. T h e heat and entropy of solution in these alloys were correlated as functions of the logarithm of the activity coefficient of nitrogen at 1873 K independent of the c o m p o sition of the alloys. A n equation w a s derived to predict the nitrogen solubility in liquid multicomponent iron alloys for the r a n g e f r o m log/N, 1873 K = 0 to -I .4 as, log (wt pct N ) T = ( - 2 4 7 / T - 1 . 2 2 ) - ( 4 7 8 0 / T - 1.51) (IOg/N ' 1873K) - (1760/T - 0.91) (log/N, 1873 K)z" an element N I T as R O inGalloyEsteels,Ncan ,be beneficial or deleterious t o mechanical properties depending upon its concentration, thermal processing of the alloy, and the presence of other alloying elements. Proper control of nitrogen is an important aspect in the production of alloy steels. Several questions, such as the nitrogen solubility in multicomponent alloy steels, the effect of temperature on nitrogen solubility, the nitrogen level at which various nitrides precipitate in alloy steels, are s t i l l t o be answered. Chipman and Corrigan~ found that the heat of solution of nitrogen in liquid binary iron alloys was proportional to the interaction parameter, and proposed an empirical l i n e a r equation for predicting nitrogen solubility in iron alloys in the r a n g e of steelmaking temperatures. The experimental data in relatively dilute iron alloys were in good agreement with a linear relationship. However, the deviation of the l i n e a r equation from the experimental data became significant in more highly alloyed steels. Turnock and Pehlke2 measured the heat of solution of nitrogen in liquid binary, ternary and multicomponent iron alloys, and proposed a second o r d e r equation in t e r m s of the logarithm of the activity coefficient of nitrogen. Kunze, Sch[imann and P a r l e ea evaluated all available experimental data on nitrogen solubility in iron-base alloys, and proposed an equation predicting nitrogen solubility at any temperature and composition from the value of heat of solution. A " c a r b o n " reference c u r v e was introduced by them from which the value of heat of solution of nitrogen in alloys eould be r e a d . Wada and Pehlke4 measured the nitrogen solubility in binary and ternary liquid F e - C r - N i alloys up t o 40 pet Cr and 20 pet Ni over a wide r a n g e of temperatures. They determined the first and second o r d e r interactions among Cr, Ni and nitrogen as a function of temperature, and obtained a second o r d e r equation predicting nitrogen solubility in F e - C r - N i alloys at any temperature and composition.
HARUE WADAis Research Associate, and ROBERT D. PEHLKE, is Professor and Chairman, Department of Materials and Met
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