The characteristics and causes of undercasting

Characteristics: There are underfilled areas and unclear contours on the surface of the castings.
Causes of occurrence:
① Poor fluidity of the alloy liquid;
② Inclusion of air, oxidation and high iron content in the alloy liquid reduce its fluidity;
③ Low pouring temperature or mold temperature;
④ Poor filling conditions;
⑤ Insufficient pressure;
⑥ Excessive entrainment of gas, increased back pressure in the cavity, and obstruction of filling;
⑦ Improper operation, such as excessive spraying of coating or accumulation of coating, preventing the gas from escaping.