Abstract
An improved shock heating test was conducted to investigate the effect of moisture condensed layer on scabbing, and the motion of moisture condensed layer and the time of fracture of sand specimens were measured. It was found that when the mold surface is rapidly heated in contact with molten metal or by radiant heat, the moisture condensed layer is formed benearth the mold surface ; simultaneously, expansion force is generated within the dried surface layer and imposes shear stress on the moisture condensed layer. Because of the distinctly weakend condition, fracture occurs on the moisture condensed layer and causes scabs.
