Causes of common defects in die casting of aluminum alloy

2020-08-19 09:34:54

A: The surface of the casting presents strip-shaped scratch marks along the opening direction, with a certain depth, and it is one-sided when severe. The other is that the liquid metal and the mold weld, adhesion and strain. As a result, the surface of the casting is fleshy or deficient. Causes: the surface of the cavity is damaged, the inclination of the die direction is too small or inverted, the ejection is inclined, the pouring temperature is too high, and the mold temperature is too high, resulting in the adhesion of alloy liquid. The application of release agent is not good, and the iron content is less than 0. 6% etc

B bubble: the surface of the casting is arched with the size of rice grain, and there is also a hollowing out of the subcutaneous structure. The reason is that the filling degree of alloy liquid in the pressure chamber is too low, which is easy to cause air entrainment, the injection speed is too high, the mold exhaust is not good, the molten liquid is not degassed, the melting temperature is too high, the metal solidification time is not enough, the strength is not enough, and the casting is ejected too early, the pressure gas expands, and the release agent is too much.

C: Cold shut, die castings have significant, irregular, sagging linear lines (both penetrating and non penetrating) with small and slender shapes. Sometimes the junction edge is lubricated, which may develop under the action of external forces. The reason: the two metal streams butted with each other, but they were not completely fused and there was no impurity between them. The pouring temperature or die casting die temperature is low, the alloy selection is improper, the fluidity is poor, the gate position is not correct or the flow path is too long, the true filling speed is low, and the injection ratio is low.

D: Discoloration and spot: the appearance of the casting is different from that of the base metal. Causes: improper mold release agent, excessive and frequent transportation of release agent, graphite in lubricant containing graphite falls into the surface of casting.

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