Grain oriented silicon- iron with a unique inhibition system for texture development
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HREE p e r c e n t s i l i c o n - i r o n with a (110)[001]. o r c u b e - o n - e d g e , t e x t u r e is widely used in the e l e c t r i c a l industry f o r its soft magnetic p r o p e r t i e s . 1 The t e x t u r e is developed by 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 , during which a r e l a t i v e l y few g r a i n s , in or n e a r the (110)[001] orientation, grow v e r y l a r g e at the expense of the s u r r o u n d i n g r e c r y s t a l l i z e d p r i m a r y g r a i n s . The final g r a i n s i z e is t y p i c a l l y up to two o r d e r s of magnitude l a r g e r than the thickness of the s t r i p , z The new high induction g r a i n o r i e n t e d s i l i c o n i r o n alloys a r e c h a r a c t e r i z e d by being n e a r e r to a p r e c i s e (110)[001 ] texture than is the conventional alloy. 3 W h e r e a s the s e c o n d a r y g r a i n s of the conventional a l loy introduced in the e a r l y 1940's have an a v e r a g e deviation of the (001} axis f r o m the r o l l i n g d i r e c t i o n of 7 deg, the high induction a l l o y s a r e c h a r a c t e r i z e d by a deviation of only 3 deg. The magnetic p r o p e r t i e s as a consequence a r e improved, with the induction i n c r e a s i n g f r o m 1.82 to 1.92 T with the s m a l l e r deviation, when subjected to a magnetizing f o r c e of 800 A / m . In the a b s e n c e of 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 , inductions a r e t y p i c a l l y 1.4 to 1.5 T. The i m p r o v e m e n t in orientation is brought about by a h e a v i e r final cold reduction and, to p e r m i t c o m plete 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 in the m o r e heavily cold r o l l e d s t r i p , i n c r e a s e d inhibition to n o r m a l g r a i n growth. 4 W h e r e a s the conventional alloy is cold r o l l e d in two s t a g e s a f t e r hot r o l l i n g with a heat t r e a t m e n t at an i n t e r m e d i a t e thickness and a final cold reduction of not m o r e than 60 pct, the high induction a l l o y s a r e p r o c e s s e d with a final cold reduction of over 80 pct, the heat t r e a t m e n t at an i n t e r m e d i a t e gage usually b e ing omitted. It is widely r e c o g n i z e d that in o r d e r f o r 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 to occur, r e s t r a i n t of n o r m a l grain growth is n e c e s s a r y . A v a r i e t y of p a r t i c l e s , but chiefly sulfides e's o r n i t r i d e s ~'7 or a combination of sulfides and n i t r i d e s 8'9 has been used for this purpose. The f i r s t high induction alloy, 8 introduced in the late 1960's, u t i l i z e s both MnS and A1N to provide inhibition to n o r m a l grain growth. P a r t i c l e s r e s t r a i n g r a i n growth b e c a u s e new g r a i n boundary a r e a equal to the c r o s s s e c t i o n a l a r e a of the p a r t i c l e must be f o r m e d if the grain boundary is to move off the p a r t i c l e . The H. C. FtEDLER is Metallurgist,General Electric Company, Corporate Research and Devel
