Patent ID: 6544359
Filing Date: 2003-04-08
Classification: C21C,C22C

Abstract:
A method of producing objects of cast iron containing compacted (vermicular) graphite crystals, characterized in:a) preparing a cast iron melt suitable for the production of ductile iron, having substantially a carbon content at the desired final level and a silicon content below the desired final value, so that the equilibrium temperature (TE) for the reaction between carbon and SiO2 is at least 1400Â° C.; b) adjusting the temperature of the melt TM to a value between the equilibrium temperature (TE) and the boiling temperature (TB), at which carbon monoxide (CO) is expelled from the melt, to allow absorption of oxygen by the melt to a level exceeding the desired level just prior to pouring the melt into a mould, wherein said level exceeding the desired level is equivalent to a concentration of 50-100 ppm, adding an amount of silicon required in order to obtain a TE approximately 20Â° C. below TM, whereby further absorption of oxygen is reduced, and thereafter reducing the oxygen content by addition of at least one selected from the group consisting of: magnesium, a magnesium containing material, and a FeSiMg-alloy, to an oxygen level of 10 to 20 ppm oxygen in liquid solution, and forming, during the reduction process, particles of magnesium silicates.