What is aluminum casting defects and how to analysis?

- Oct 28, 2019-

Aluminum casting defects and analysis (part one)

The finished product of casting machine not 100% perfect but have something problem as following(part one):

Oxidized slag

Defect characteristics: Oxidation slag is distributed on the upper surface of the casting at the corner where the mold is not ventilated. The fracture is mostly grayish white or yellow. It is found by x-ray or during machining. It can also be found in alkaline washing, pickling or anodizing.


1. The charge is not clean, and the amount of recycled material is too much.

2. Pouring gypsum system design

3. The slag in the alloy liquid is not cleaned

4. Improper pouring operation, bring in slag

5. After the refining treatment, the rest time is not enough

Prevention method:

1. The charge should be blown and the amount of recycled material should be reduced appropriately.

2. Improve the design of the gating system and improve its slag blocking capacity

3. Use appropriate flux to remove slag

4. It should be smooth when pouring and should pay attention to slag

5. The alloy solution should be allowed to stand for a certain period of time before refining.

Two pores

Defect characteristics: The pores in the wall of the three castings are generally round or elliptical, with a smooth surface, generally shiny scale, sometimes oily yellow. Surface pores and bubbles can be found by sand blasting. The internal pores can be found by X-ray or machining. The bubbles are black on the X-ray film.


 1. Casting alloy is not stable, and it is involved in gas

 2. Type (core) sand mixed with organic impurities (such as coal chips, grass roots, etc.)

3. Poor mold and sand core ventilation

4. Cold iron surface has shrinkage holes

5. Poorly designed gating system

Prevention method:

 1. Correctly control the pouring speed to avoid getting in the gas.

 2. No organic impurities may be mixed into the type (core) sand to reduce the amount of gas generated by the molding material.

3. Improve the exhaust capacity of (core) sand

4. Correct selection and handling of cold iron

5. Improved gating system design