Abstract: A cored wire (1; 100) intended to be injected into a molten metal bath to perform metallurgical treatment, the cored wire comprising: a fill (2) extending locally along a longitudinal axis (L), the fill comprising at least one active substance to treat the molten metal; and an outer sheath (4) extending longitudinally around the fill, characterized in that the fill comprises: an extruded bar (8) extending longitudinally and comprising the active substance; and an intermediate layer (10) extending longitudinally between the extruded bar and the outer sheath and comprising a powder containing one or more from among: a metal, a mixture of metals, a metal oxide, a mixture of metal oxides.