Casting defects should first determine what causes. Cracks caused by many reasons, have the following common                                                                                                                                                                                           

1,Stoma

Feature, the pore often take place interiorly, some smooth air hole exist in the surface or subsurface. Sidewall sometimes exhibits oxidation colour. Because the gas come from different source and different forming reason, the exibit different formation, such as ingressive pore, precipitation pore, subsurface pore.

2,Sand hole, inclusion hole

Feature: in inner or on the surface of the defect location, some hole fill with sand which called sand hole. If the defect represent irregular formation, and filling with residue or inclusion, which called inclusion hole.

3,Shrinkage or looseness

Feature: on the thick section of casting, hot spot or the axis center of the last freezing location, rough holes often take place, and more or less formed dendrite. Big and concentrated holes are called shrink, small and scattered are called looseness. The reduction in liquid shrink is more bigger than in solid shrink during the metal liquid turning into solid, and in the last location of freezing, no metal liquid can be available for compensation.

4,Adhering

Feature: on the surface of the casting, there is a layer of model material, which is different to remove. Including mechanical and chemical adhesive. The difference between these: mechanical adhesive is formed when the high temperature metal liquid enter into the gap among sands; when metal is oxidized and combined with the model material and form a combination with low melt temperature, and bonded firmly 

5,Crack