The re-solution of inclusions in remelted stainless steels
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n u m e r o u s r e m e l t i n g and w e l d i n g p r o c e s s e s c a r r i e d out on s t a i n l e s s s t e e l s t h e r e a r e c o m p l e x i n t e r a c t i o n s a m o n g the m e t a l , i n c l u s i o n and flux p h a s e s p r e s e n t . The net r e s u l t of the t h e r m o c h e m i c a l conditions e x p e r i e n c e d d u r i n g any such m a n u f a c t u r i n g p r o c e s s i n f l u e n c e s the t o t a l i n c l u s i o n content and the d i s t r i b u t i o n of i n c l u s i o n s within the m e t a l . 1,z This in t u r n g r e a t l y d e t e r m i n e s the final p r o p e r t i e s of the m a n u f a c t u r e d component. An u n d e r s t a n d i n g of the e v e n t s that take p l a c e d u r i n g r e m e l t i n g is t h e r e f o r e of c o n s i d e r a b l e i n t e r e s t to the p r o d u c e r s and f a b r i c a t o r s of s t a i n l e s s s t e e l s , z In the i n i t i a l s t a g e s of this study 304L, 316L and 317L s t a i n l e s s s t e e l s - - s e e Table I for n o m i n a l c o m p o s i t i o n s - w e r e e l e c t r o s l a g r e m e l t e d to p r o d u c e i n gots of l o w e r i n c l u s i o n content than the e l e c t r o d e m a terial r e c e i v e d from conventional electric arc furnace p r a c t i c e . The r u n s w e r e a l s o conducted with a v i e w to m i n i m i z i n g the l o s s of the a l l o y i n g e l e m e n t s p r e s e n t in the s t e e l s . The d e t a i l s of this will be g iv e n l a t e r . M e t a l l o g r a p h i c e x a m i n a t i o n i n d i c a t e d that the e l e c t r o s l a g r e m e l t e d m a t e r i a l was significantly " c l e a n e r " than the electrode material as far as large-sized inclusions were concerned, v i z . , all inclusions greater than one micron in size. See Figs. 1 and 2. The results of the oxygen and nitrogen analyses,* however, *The authors wish to thank Dr. S. G. Whitewayand Messrs.J. Uher and C. Collings,of the AtlanticRegionalLaboratories, of the National ResearchCouncil of Canada, Halifax,NovaScotia, for their aid in doing the vacuum fusionanalyses reported here. f or s i x ingots of 304L s t a i n l e s s s t e e l i n d i c a t e d only a slight d e c r e a s e in the oxide and n i t r i d e content a f t e r e l e c t r o s l a g r e m e l t i n g . This can be s e e n on e x a m i n i n g Table If. C l e a r l y if e s s e n t i a l l y all of the i n c l u s i o n s l a r g e r than one m i c r o n h a v e a p p a r e n t l y b e e n r e m o v e d and yet the t o t al gas content is s u b s t a n t i a l l y unchanged,
then one of two s i t u a t i o n s m u s t be p r e s e n t . E i t h e r m o s t of the l a r g e i n c l u s i o n s in the e l e c t r o d e a r e m e r e l y b e i n g r e d i s t r i b u t e d , o r t h e r e is a s o u r c e of r e o x i d a t i o n and r e n i t r i d i n g which is q u a n t i t a t i v e l y r e p l a c i n g the l a r g e i n c l u s i o n s that a r e b e i n g r e m o v e d by the e l e c t r o s l a g p r o c e s
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