common defects of aluminum castings

Aluminum castings generally uses sand molds or metal molds to pour the heated liquid aluminum or aluminum alloy into the mold cavity, and then obtain the aluminum parts or aluminum alloy parts of various shapes and sizes,the production process involves some alloy additives such as silicon metal, magnesium ingot, etc.

Some common defects will be encountered in the process of cast aluminum production. Below we will show you more details:

1. Oxidation and slag inclusion

Defect characteristics: Oxidized slag is mostly distributed on the upper surface of the casting, at the corners of the mold where no air is passed. The fractures are mostly grayish white or yellow, and are found in X-ray fluoroscopy or mechanical processing, and can also be found in alkaline washing, acid washing or anodizing.

Preventive measures: 

(1)The charge should be sand blown, and the consumption of the return charge should be appropriately reduced; 

(2)Improve the design of the pouring system to increase its slag retaining ability; 

(3)Use appropriate flux to remove the slag; 

(4)The pouring should be stable and pay attention to slag retaining; 

(5)Refining The alloy should stand for a certain period of time before post-pouring.

2. Stoma and bubbles

Defect characteristics: The pores in the casting wall are generally round or oval, with a smooth surface, generally shiny oxide skin, sometimes oily yellow. Surface pores and bubbles can be found by sandblasting, and internal pores and bubbles can be found by X-ray fluoroscopy or mechanical processing.

Preventive measures: 

(1)Reduce the filling speed to avoid eddy current entrapment; 

(2)No organic impurities should be mixed into the mold (sand) core to reduce the amount of gas generated by the molding material; 

(3)Improve the exhaust ability of the molding sand (core); 

(4)Select and treat correctly Cold iron; 

(5)Improve the design of the pouring system.

3. Shrinkage

Defect features: Shrinkage porosity of aluminum castings generally occurs in thick parts of non-riser roots near the inner runner, wall thickness transition points and thin walls with large flat surfaces. In the as-cast state, the fracture is gray and light yellow. After heat treatment, it is grayish white, light yellow or gray black. On the X-ray film, it is cloudy and severely filiform, or it is found by X-ray, fluorescence low-power fracture inspection.

Preventive measures: 

(1)Pour molten metal from the riser and improve the riser design; 

(2)The charge should be clean and non-corrosive;

(3)Set the riser at the shrinkage of the casting, and place the chilled iron or chilled iron in combination with the riser; 

(4)Control the moisture content of the molding sand The sand core is dry;

(5)Measures to refine the grains are taken; 

(6)The position of the casting in the mold is improved, and the pouring temperature and pouring speed are reduced.

4.Peeling

Causes: 

(1)Poor filling mode, causing overlap of molten metal; 

(2)Deformation of mold, causing overlap of molten metal; 

(3)Inclusion of oxide film.

Preventive measures: 

(1)Switch to high-speed filling early; 

(2)Shorten the filling time; 

(3)Change the filling mode, gate position, pouring speed; 

(4)Check whether the mold strength is sufficient;

(5)Check whether the pin device is good; 

(6)Check whether there is oxide film.

Aluminum castings have a wide range of uses, such as auto parts, various housewares, and industrial machine parts. Compared with cast steel and iron castings, aluminum castings have some higher quality properties;

1.It can produce parts with complex shapes, especially rough blanks with complex cavities (such as heating)

2.Wide adaptability, metal materials commonly used in industry can be cast from few grams to hundreds of tons.

3. Raw materials are widely and price low, like aluminum scrap, aluminum dross, cuttings etc.

4.The shape and size of the casting are very close to that of the parts, reducing the amount of cutting, which is less and without cutting.

Anyang Huatuo Metallurgy Co.,Ltd has helped much more aluminum castings produce high quality cast aluminum parts, always supply high quality silicon metal and magnesium ingot to them, so if any interests can consult us.