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There are three kinds of defects in castings, which are penetrating linear defect, cavity defect and shrinkage defect.

1, through the linear class defects

Have crack commonly, cold lie between wait, the surface shows long and narrow and fine fission phenomenon, have continuously, discontinuous, have linear, wave form, the continuity that this kind of blemish broke up part.

The depth of such defects is often not measurable, even after the repair welding, in the use of the process may also lead to early crack growth, resulting in the fracture or leakage of parts, so the through linear defects are not allowed to repair.

2, hole surface defects

Hole surface defects generally refer to the air holes, shrinkage holes, sand holes, slag holes and lack of flesh exposed after casting processing. In addition, casting machined surface bumps, scratches and other defects also belong to this category. This kind of defect presents isolated distribution, with different shapes, sizes and positions, which has great randomness.

Such defects generally present opposite distribution, limited depth, visibility, and matrix support, there is the possibility of repair.

3. Internal defects of pinches

The internal defects of shrinkage cavity generally refer to the shrinkage cavity and porosity of castings which have not been exposed obviously after machining and are mainly network or dendritic holes. If this kind of defect is connected with the internal pipes and the processed surface of the parts, it will lead to the internal densification and leakage of the parts.

This kind of defect has slight penetration characteristics, easy to lead to parts leakage, there is the possibility of infiltration.

How to repair casting surface defects?

There are two methods: hot welding and cold setting. Among them, the hot welding method usually has the electric welding, the gas welding, the metal spraying and so on, but the cold setting repair method has the epoxy resin repair, the plug repair, the electric brush plating.