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Aluminum Die Casting Defect Analysis
Jul 06, 2018

Aluminum die casting defect analysis.

 

Die casting is a metal casting process characterized by the use of a mold cavity to apply high pressure to the molten metal, similar to plastic injection molding. Die casting is particularly suitable for the manufacture of a large number of small and medium-sized castings, so die casting is the most widely used of various casting processes. Compared to other casting techniques, the die-cast surface is flatter and has a higher dimensional consistency. However, non-standard operations and parameters can also produce a wide variety of defects.

 

The flow marks and patterns

Visual inspection:

There are stripes on the surface of the casting that are consistent with the flow direction of the molten metal. There is a visible non-directional texture that is different from the color of the metal substrate, and there is no development trend.

The causes of the flow marks are as follows:

(1) The mold temperature is too low;

(2) Poor design of the runner, poor position of the gate;

(3) the material temperature is too low;

(4) low filling speed and short filling time;

(5) The pouring system is unreasonable;

(6) poor exhaust;

(7) The spray is unreasonable.

 

Reticulated wing (Craquelure)

Visual inspection:

The surface of the die-casting part has a mark of convex or concave like a mesh hair, which is continuously enlarged and extended as the number of times of die casting increases.

The reasons are as follows:

(1) There is a crack on the surface of the die-casting cavity;

(2) The pre-heating of the die-casting mold is uneven.

 

Concave (dent)

Visual inspection:

There are smooth indentations (like a dish) on the surface of the majority of the thickness of the die casting.

The reasons are as follows:

(1) caused by shrinkage

Die castings are not designed with too much wall thickness difference;

The sprue is not in the proper position;

The injection pressure is lower than the pressure, and the pressure holding time is short;

The local temperature of the die casting mold is too high.

(2) The cooling system design is unreasonable;

(3) The mold opening is too early;

(4) The pouring temperature is too high.