Development of (110) [001] texture in iron by diffusion of sulfur into grain boundaries
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I T is known that iron and 3 pet Si-Fe can undergo s e c ondary recrystallization selective to a magnetically desirable (110)[0011 orientation*' 2 if, among other factors, the normal tendency for p r i m a r y grains to c o a r s e n is restrained. Restraint is commonly accomplished by "inhibitor in the m e l t " techniques wherein a p r e c i p i tate, e.g., MnS, is dispersed as finely divided particles. Such particles r e s t r a i n ~ a i n boundary motion by a Zener-type mechanism, thus maintaining grain bounda r y energy which drives (110)[001 ] secondary grain growth at t e m p e r a t u r e s in excess of ~ g25~ Solutes have also been reported to r e s t r a i n p r i m a r y grain growth; specifically, Grenoble and Fiedler 4 observed (110)[0011 secondary grain growth in 3 pet Si-Fe sheet having no second phase particles, but with sulfur and nitrogen present as solutes. These investigators suggest that grain boundary diffusion of solute sulfur and nitrogen inhibits p r i m a r y grain growth. Their r e a s o n ing is partially supported by observations of rapid grain boundary diffusion of sulfur in iron and 3 pet Si-Fe 5 below ~ 1000~ and the known pinning effect of solutes on grain boundary motion.6 The purpose of this study was to investigate the feasibility of texturing thin sheet iron by solute-induced grain boundary r e s t r a i n t wherein sulfur was supplied by an inert s e p a r a t o r . I. E X P E R I M E N T A L The m a t e r i a l used in this study was c o m m e r c i a l high purity iron supplied as 2 m m thick hot band sheet. Chemical analysis data for several important elements are listed in Table I. This sheet was processed to a final thickness of 0.15 m m by a single-stage routing without intermediate annealing and several two-stage routings with intermediate annealing. For the twostage routings, the intermediate thickness was adjusted so that the final cold reduction ranged from 50 to 75 pet. The intermediate anneal consisted of strip annealing in hydrogen (dew point of - I0~ for 5 min at 800~ but in some instances this anneal was conducted at 1000~ which is the r-phase of iron. At final thickness, all material was strip annealed at 800~ for 5 rain in order to bring about primary recrystallization. Rolling was done on a four-hlgh Stanat mill having 38 m m dlam W. M. SWIFTis Senior Engineer, Westinghouse Electric Corp., Research & DevelopmentCenter, Pittsburgh, Pa. 15235. Manuscript submitted March 4, 1974. METALLURGICALTRANSACTIONS
Tal~e I. Chemical Composition of Hig~ Purity Hot Band Sheet Pct Mn
Pct S
Pct C
Pct N
0.018
0.006
0.0045
0.0048
work rolls and 126 mm diam back-up rolls. The sheet was not lubricated. Sheets were slit to standard Epstein width (30 ram), sheared to lengths of 360 mm, and coates with an aqueous s l u r r y of 95 pet MgO-5 pot sulfur (flow. ered form). The coated s t r i p s were annealed at 880~ for 48 h in dry hydrogen (dew point of - 60~ in an Inconel tube furnace. Heating and cooling r a t e s were 100~ Standard Epstein f r a m e methods (ASTM Method A
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