The elimination of anti-veining sand additives through the use of active ingredient absorption coatings

摘要

The automotive sector has a continuing requirement for increasingly complex, high performance castings - while driving down production costs. The cores for these castings are increasingly produced using silica sand and polyurethane coldbox binders, a combination that is known to promote vein type defects that are difficult and costly to remove. Traditionally such defects are minimised using a combination of coating and anti-veining sand additives, however vein defects occurs at the core surface, whereas the anti-veining additive is added to the whole core, increasing consumption costs. A new coating eliminates the use of wasteful anti-veining additives by promoting the absorption of active anti-veining ingredients from the coating into the core surface, delivering anti-veining protection where needed. The coating is applied in a one dip process, with components of the coating absorbing into the core surface, replacing traditional anti-veining additives, while additionally building a protective coating layer on the surface. The paper discusses the mechanism of the veining defect, the function of the active ingredient and how it is preferentially absorbed into the core surface, and provides case study documentation of performance.