A billet of temporarily magnetizable (i.e., soft magnetic) material is deformed by a controlled flow of pressurized extrusion fluid passing between the nose of the billet and a flow control surface, thereby to give the product a preferred texture and crystallographic orientation. Heat generated in the material as a result of the deformation is employed to elevate the temperature of the material to magnetic annealing temperature, supplemented by auxiliary heating means if the heat of deformation is insufficient, or by cooling means if the heat of deformation is excessive, and the deformed material is magnetically annealed in a magnetizing field downstream from the exit end of the zone of deformation. The billet may be round or rectangular, of finite or of indefinite length, and the product may be wire or strip or sheet having high magnetic permeability.