The solubility product of boron nitride in 3.1 pet silicon-iron
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The addition of b o r o n to 3 pet s i l i c o n - i r o n m a k e s p o s s i b l e the d e v e l o p m e n t of a p r e c i s e (110)[001] s e c o n d a r y r e c r y s t a l l i z a t i o n t e x t u r e , with a r e s u l t a n t high m a g n e t i c induction. 1-3 Boron, n i t r o g e n and s u l f u r together a r e n e c e s s a r y to provide i n h i b i t i o n to n o r m a l g r a i n growth, a p r e r e q u i s i t e for s e c o n d a r y r e c r y s t a l lization, in one of the two i n h i b i t i o n s y s t e m s thai i n clude b o r o n . 2'3 B o r o n is known to be a s t r o n g n i t r i d e f o r m e r , 4 and the objective of the work to be r e p o r t e d was to d e t e r m i n e the s o l u b i l i t y p r o d u c t of the compound BN in 3.1 pct s i l i c o n - i r o n . F o u n t a i n and C h i p m a n4 d e t e r m i n e d the s o l u b i l i t y product of b o r o n n i t r i d e in g a m m a i r o n for t e m p e r a t u r e s of 950 to 1150~ and f r o m that data c a l c u lated the s o l u b i l i t y product in pure alpha iron. Somewhat l a t e r , and a p p a r e n t l y u n a w a r e of the F o u n t a i n and C h i p m a n r e s u l t s , M a n e s c h i and B e c c a r i a s also d e t e r m i n e d the s o l u b i l i t y product in g a m m a i r o n . At 1200~ t h e i r value for the s o l u b i l i t y product is about 50 pct l a r g e r than that of F o u n t a i n and Chipman. P r o c e d u r e . Ingots weighing 1.4 kg were v a c u u m m e l t e d u s i n g Glidden A104 e l e c t r o l y t i c i r o n and high p u r i t y s i l i c o n . B o r o n was added as FeB. They were poured in a r g o n o r in a r g o n containing n i t r o g e n . A f t e r h e a t i n g to 1230~ in hydrogen, the alloys were hot r o l l e d to a t h i c k n e s s of 2.3 m m . Following pickling, the pieces were heat t r e a t e d for 3 rain at 950~ in h y d r o g e n and cold r o l l e d to 0.30 m m , the f i n a l thickn e s s . The alloys contained 3.1 pct s i l i c o n , 0.005 pct carbon, 0.003 pet s u l f u r , 0.002 pet m a n g a n e s e , less than 0.002 pet a l u m i n u m and l e s s than 0.010 pct oxygen. The b o r o n content r a n g e d f r o m l e s s than 1 ppm with no b o r o n added to as high a s 55 ppm. The a n a l y s e s for b o r o n w e r e by a r c e m i s s i o n s p e c t r o s c o p y ; the r e p r o d u c i b i l i t y of the r e s u l t s was • pet in the b o r o n r a n g e i n v e s t i g a t e d . The n i t r o g e n content of the cold r o l l e d s t r i p s r a n g e d f r o m 4 to 100 ppm. A l l of the a n a l y s e s for n i t r o g e n were by the i n e r t gas fusion p r o c e d u r e , for which the r e p r o d u c i b i l i t y was +3 ppm. The p r o c e d u r e used to d e t e r m i n e the s o l u b i l i t y product was to e q u i l i b r a t e s a m p l e s in high p u r i t y n i t r o gen. The s a m p l e s were a b r a d e d and s e a l e d i n d i v i d u a l l y in q u a r t z t u b e s with sufficient n i t r o g e n
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