Abstract
This chapter focuses on scab defect. Scabs and such related casting defects as rat-tails and buckles are the result of cracks appearing in the sand mould or core wall when the material is subjected to rapid heating during casting. Cracks are caused by the rapid and considerable expansion of quartz during its transformation to the ß form at the temperature of 573°C. The parts near the metal interface will expand more than those inside the mould wall because of the temperature gradient existing. If a single crack appears, the casting shows defects known as buckles or rat-tails. Scab defects are more common with green synthetic sands than dry or silicate–CO2-bonded sands. It is assumed that the moisture evaporated from the heated crust condenses behind forming a wet sand–sand interface within the mould. The chapter presents some experimental studies of scab and related defects and possible remedy for scab defect.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
