An assessment of the control of finning (veining) defects in iron castings produced with phenolic - urethane cold - box bonded cores

摘要

Finning (or Veining in the USA) defects have been around for as long as foundrymen have been making cores in anything but greensand. Finning is, of course, an expansion defect caused when the sand grains (on the surface of a mould or core) expand due to heat from the molten metal. The rapid expansion of, predominantly, silica (quartz) sand at around 573℃ (α-β phase transformation) is the cause of the stresses that then cause the binder to fail allowing a crack to open up which then fills with the molten metal (usually iron but also bronzes and, sometimes, steels). inning is, of course, just one of several different types of expansion defect, including scabbing (buckling) and rat tails, that have been experienced by iron casters for a very long time indeed. Finning defects have been the source of comment in foundry literature for many years and it is to some degree astonishing that finning defects still exist in the modern foundry, albeit to lesser extent than once was the case.