Common defects in castings and their causes are:

1, stomata
The cause of the pores is that there is too much moisture in the molding material or contains a large amount of gas-generating substances; the sand and core sand have poor gas permeability; the casting speed is too fast.
2, trachoma
The cause of the blisters is that the sand is not strong enough; the sand is not tight enough; the pouring speed is too fast.
3, shrinkage hole
The reason for the shrinkage cavity is that the casting has poor shrinkage during solidification.
4, sticky sand
The cause of the sticking is that the sand has poor fire resistance or the casting temperature is too high.
5, crack
The reason for the crack is that the wall thickness of the casting is greatly different; the casting system is improperly opened; the sand type and the core have a new concession.