DTA

stereo microscope

SEM and micro-area EDS were used to observe and analyze the shrinkage porosity in the gypsum mold jewelry castings.The results show that during the solidification process

the crystal grows in dendritic form and the shrinkage porosity generated in the dendrite gaps is caused by insufficient feeding of external liquid metal.Some parameters

such as alloy properties

casting structure

pouring system

mould temperature and pouring process

have significant impact on the dendritic growth and shrinkage porosity.To avoid shrinkage porosity defect in jewelry casting

alloy materials with suitable melting point and narrow solidification range should be selected preferentially

and jewelry structure and pouring system should be optimized

and castings with markedly different structures should not be poured at the same time

meanwhile

the mould temperature and pouring temperature should be controlled reasonably

and sufficient feeding force should be provided by centrifugal pressure casting or vacuum suction casting.