A process and apparatus for feeding an additive to a molten metal in a vessel to achieve a uniform dispersion of the additive are provided. In one example, the outlet of the lance is positioned below the surface of the molten metal. The lance is moved with a reciprocating motion, so that the outlet of the lance moves below the surface of the molten metal. The additive is dispensed through the outlet of the lance along a path traversed by the outlet in the molten metal while the lance reciprocates.