Application of Surface Layer Inoculation Processes to Solid Solution-Strengthened Ductile Cast Iron

Within the present investigations, an in-mould inoculation method for ductile cast iron with elevated silicon contents was developed. The inoculation process takes place at the interface between the mould's surface and the melt. The application of a mould wall inoculation process allows inoculation at the latest possible point in time, which means high efficiency due to reduced fading effects. For this purpose, various inoculant suspensions are produced, containing inoculants in different amounts and grain fractions. The inoculant is applied to the surface of a PEP SET (TM)-bonded moulding material by means of an air-pressurized spraying pistol. The specimen geometry used in the tests is a 5-stepped wedge, which represents wall thicknesses in the range of 5-40 mm. For a total of 8 castings, inoculant fractions in the spectrum of 0-25 and 0-45 mu m are used to produce the solid solution-strengthened grade EN-GJS-500-14 that is specified in the European standard EN 1563. Metallographic investigations show that a complete solidification according to the stable system can be adjusted in the investigated wall thicknesses by inoculation with grain fractions of 0-25 mu m.