Heat flow, gap formation and break-outs in the continuous casting of steel slabs
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A t h e o r e t i c a l i n v e s t i g a t i o n of heat flow and gap f o r m a t i o n i n the m o l d of a continuous s l a b c a s t e r has b e e n u n d e r t a k e n u s i n g a m a t h e m a t i c a l modei, with the u l t i m a t e p u r p o s e of p r e d i c t i n g the c a s t i n g c o n d i t i o n s which can lead to b r e a k - o u t s . The m a t h e m a t i c a l m o d e l that has b e e n developed for this study is capable of t r e a t i n g the heat flow and a i r gap as coupled p h e n o m e n a , and can accept o p e r a t i n g v a r i a b l e s such as s l a b s i z e , c a s t i n g speed, m o l d t a p e r , and t h e r m a l c o n d u c t i v i t y of the mold powder, as input. F o u r d i f f e r e n t c a s e s of s l a b c a s t i n g have b e e n i n v e s t i g a t e d ; and it has b e e n found that hot spots c a n f o r m o n t h e s u r f a c e of the slab within a few c e n t i m e t e r s of the c o r n e r s . D e p e n d i n g on t h e i r t e m p e r a t u r e , it is s u g g e s t e d that t h e s e hot spots m a y give r i s e to the f o r m a t i o n of b r e a k - o u t s off the c o r n e r s of the s l a b . F r o m an e x a m i n a t i o n of the b e h a v i o r of the hot spots, the s u s c e p t i b i l i t y of the c a s e s studied to b r e a k - o u t s has b e e n e v a l u a t e d . T h e u s e f u l n e s s of the p r e s e n t a n a l y s i s in q u a l i t a t i v e l y a s c e r t a i n i n g the l o c a t i o n and extent of mold w e a r u n d e r d i f f e r e n t c a s t i n g conditions has also been e x a m i n e d . ] 3 REAK-OUT of the liquid core, when it o c c u r s , is a s e r i o u s p r o b l e m in the continuous c a s t i n g of s t e e l s l a b s and b i l l e t s , s i n c e the m o l t e n s t e e l that e s c a p e s t h r o u g h the s o l i d s h e l l u s u a l l y r u n s into the s u p p o r t a s s e m b l y below the mold, and stops any f u r t h e r c a s t ing of the s t r a n d involved. C a s t i n g then cannot be r e s u m e d u n t i l the s p i l l a g e and p a r t i a l l y s o l i d i f i e d s t e e l s t r a n d have b e e n r e m o v e d f r o m the c a s t i n g m a c h i n e , and i n the c a s e of a s e r i o u s b r e a k - o u t , r e p a i r s made to the s u b m o l d a s s e m b l y . D e p e n d i n g on the f r e q u e n c y and s e v e r i t y of the b r e a k - o u t s , t h e s e o p e r a t i o n s can b e c o m e t i m e c o n s u m i n g and c o s t l y . F o r this r e a s o n an u n d e r s t a n d i n g of the c a u s e s of b r e a k - o u t s and the m e a n s of p r e v e n t i n g them a r e f u n d a m e n t a l l y i m p o r t a n t to efficient c a s t i n g p r a c t i c e . At the p r e s e n t t i m e , t h e c a u s e s of b r e a k - o u t s a r e only i m p r e c i s e l y understood; but due to the fact that they m o s t often o c c u r j u s t below the mold, it is likely that they a r e r e l a t e d to the n a t u r e of heat flow i n the m o l d i t s e l f . T h a t m o r e is no
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