Method and additive composition for preparing ductile cast iron, and ductile cast iron obtainable by said method

The present invention relates to a method for preparing ductile cast iron, comprising the steps of (a) melting a base iron to obtain a molten iron; (b) treating the molten iron with a nodulazing composition; (c) introducing the nodulized molten iron into a pouring unit; (d) holding the molten iron in the pressurized pouring vessel of the pouring unit resulting in a molten iron having a sulphur content from 0.002 wt. % to 0.006 wt. %; (e) pushing the molten iron from the pressurized pouring vessel to the pouring basin of the pouring unit; (f) pouring a stream of the molten iron from the pouring basin into a mould; and (g) allowing the molten iron to solidify in said mould; wherein the molten iron is treated with an additive composition and with an inoculating composition after step d) and prior to step g); wherein the additive composition comprises a source of sulphur, a source of selenium and, optionally, a source of tellurium and/or a source of rare earth elements, and comprises a carrier; and wherein the total content of sulphur, selenium, and optionally, tellurium and/or rare earth elements, in the resulting molten iron is increased by a total amount from 0.002 to 0.012 wt.% respect to total weight of the molten iron. The present invention relates also to an additive composition for preparing ductile cast iron according to said method, and to a kit comprising said additive composition and an inoculating composition. Finally, the present invention relates to a ductile cast iron obtainable by said method and to the use of the additive composition in the production of ductile cast iron.