Defect prevention

An overview of the key measures for preventing metallization

  • In order to prevent defects, it is recommended to assess the sintering behavior of bentonite, the molding base material and mold material mixtures by means of tests. The sintering behavior of these components should reach highest values in any case.
  • Molding sands should not exhibit any contamination that enables a reaction with the slag and the formation of low-melting slags.
  • Increasing the thermal stability of the mold material by adding new sand (to reduce oolitization); not using or adding any contaminated sands.
  • Using chemically neutral molding base materials; chromite sand, for example, has proven to be favorable to silica sand.
  • Carefully coating molds and cores; the occurrence of small cracks in the coating layer is to be avoided; possibly increasing the thickness of the coating layer.
  • The formation of reactive oxides and slags should be prevented by adding a sufficient amount of components that form lustrous carbon.
  • All measures that help to prevent penetration also have a positive influence on the prevention of metallization.