Abstract: A grain oriented silicon steel sheet having a low iron loss and not causing degradation of properties even through strain relief annealing is produced by applying ultrasonic vibrations to the surface of the sheet after secondary recrystallization annealing.

Abstract: A method for preventing the camber of a two-layered clad metal sheet having a base layer and a covering layer of different metals which exhibit different amounts of thermal contraction. The method comprises developing a temperature difference .DELTA. T expressed by the following formula between the base layer and the covering layer during a hot levelling, by providing a greater cooling effect before or during levelling to the layer which exhibits the greater thermal contraction than to the layer which exhibits the smaller thermal contraction:.DELTA.T=f (.DELTA..alpha., .alpha., a, To)where,.DELTA..alpha.: the difference in thermal expansion coefficient between both metalsa: the clad ratio (ratio of covering layer thickness to total sheet thickness)To: hot leveller inlet temperature (.degree.C.).alpha.: mean thermal expansion coefficient of both metals.