In some grey cast ironGrey cast iron components, which are cast in sand moulds, the metalMetals sometimes penetrates into the mould producing defectsDefects and causes difficulties when cleaning the components. To improve knowledge of the metalMetals penetration mechanism, a series of test casting was performed in production scale where the influence of different inoculantsInoculant and different amounts was studied. Investigation of the various inoculantsInoculant shows that the inoculation of grey cast ironGrey cast iron will influence the metal expansion penetrationMetal expansion penetration in areas with late solidificationSolidification times. The amount of inoculantInoculant added shows a clear effect on the degree of metalMetals penetration. The whole casting processProcess was simulated with the software MagmaSoft® in order to investigate the solidificationSolidification characteristics as well as the porosityPorosity in the casting component. © The Minerals, Metals & Materials Society 2024.