The purpose of the present study was to precise mechanisms at the origin of the exaggerated Goss grain growth of Fe–3% Si sheets, grade Hi–B. It has been pointed out that at the primary recrystallized state, the Goss grains which belong to the small grain class are present through the whole sheet thickness. In presence of AlN and MnS inhibitors, their growth during the anisothermal secondary recrystallization annealing is due to the high mobility of the special C.S.L. boundaries; their subsequent expanse at the fifth of the sheet thickness is favoured by purification of the sheet. Indeed, after dissociation of AlN and MnS precipitates at high temperature, a concentration gradient in sulfur and in nitrogen due to the reducing hydrogen atmosphere has been observed in subsurface thanks to SIMS experiments, such as general and C.S.L. boundaries can easily move whereas those at the center of the sheet are more dragged.