1. Casting porosity
Porosity is a kind of hole on the surface or inside of the casting, which is round, elliptical or irregular. Sometimes, multiple pores form an air mass, and the subcutaneous is generally pear shaped.
2. Casting shrinkage
Shrinkage cavity is a kind of rough surface hole on the surface or inside of the casting. A slight shrinkage cavity is a lot of scattered small shrinkage cavities, i.e. shrinkage cavity, where the grain is coarse.
3. Casting slag inclusion
Slag hole is the open hole or dark hole on the casting. It is filled with slag completely or partially. Its shape is irregular. It is not easy to find small point flux slag inclusion. After the slag is removed, it presents smooth holes, which are generally distributed in the lower part of the pouring position, near the inner sprue or the dead corner of the casting. Oxide slag inclusions are mostly distributed on the casting surface near the inner sprue in a network, sometimes in a sheet shape or with wrinkles The irregular cloud like pattern, or the formation of lamellar interlayer, or the existence of the inner part of the casting in the form of floccules, often breaks from the interlayer when breaking, in which oxide is one of the causes of the formation of cracks in the casting.
4. Cracks in casting
The appearance of the crack is straight or irregular curve. The hot crack fracture surface is strongly oxidized to dark gray or black, without metallic luster. The cold crack fracture surface is clean and has metallic luster. Generally, the external crack of castings can be seen directly, while the internal crack can only be seen by other methods. Cracks are often associated with shrinkage porosity, slag inclusion and other defects, most of which occur in the inner side of the sharp corner of the casting, the junction of thick and thin sections, and the hot spot area where the pouring riser is connected with the casting.
A relatively regular hole is formed on the surface or inside of the casting, and its shape is consistent with the shape of the sand particles. When the casting is just out of the mold, the sand particles inlaid on the surface of the casting can be taken out. When multiple sand holes exist at the same time, the surface of the casting is orange peel.