Accumulation of heat at eges in the mold cavity.
Thin mold material sections protruding in the mold cavity are heated particularly strongly by the melt. This delays the local solidification in such a way that the accumulation of heat increases as the radius of the edge decreases. This can promote the occurrence of cavities and hot cracks on filets with sharp or insufficiently rounded edges. This risk can be reduced by altering the design. Atmospheric risers take advantage of the sand edge effect where the heated mold material releases its thermal energy to the surrounding metal thus preventing early freezing.