The role of solutes in the secondary recrystallization of silicon iron

Secondary recrystallization of silicon iron is widely understood to be a consequence of certain impurities present in small amounts which affect the mobility of grain boundaries. Whether it is a solute fraction of the impurity content which influences mobility by segregating to grain boundaries, or a precipitated fraction which stabilizes boundaries by inclusion pinning at a large number of sites, is not wholly resolved. Neither mechanism necessarily excludes the other. In this paper, evidence will be presented that boundary mobility is affected by very small changes in bulk solute content, and presumably therefore, by small changes in the solute content of the boundaries. Sulfur, nitrogen, and boron in combination when present in the small quantities that can be retained in solid solution bring about complete secondary recrystallization. For strip cold rolled in two stages with an 80% reduction in the final stage, values of μ at 10 Oe in excess of 1900 are obtained.