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What is the Cause of Sand Hole in Aluminum Alloy Die Cast Part?

Mar. 28, 2020
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In die castings, due to the special characteristics of die casting, aluminum alloys are formed under high temperature, high speed, and high pressure. Therefore, there are unavoidable holes in the die castings. We collectively call these holes sand holes. This is also the most common quality problem for Aluminum Alloy Die Cast Part.

As an Aluminum Alloy Die Cast Part Factory, share with you the classification and expression of sand holes.

Aluminum Alloy Die Cast Part

Aluminum Alloy Die Cast Part

1. Stomata: In the process of die-casting, the holes generated due to the complexity of the mold cavity and the control of the production process will exist at any position in the casting, and can be subdivided into entangled pores precipitated pores, and There are three types of invasive stomata, each of which has its own form of expression, which I will explain one by one later.

2. Slag holes: In the process of die-casting, due to the impureness of the aluminum soup or the entry of foreign bodies during the die-casting, the foreign bodies inconsistent with the aluminum alloy body can be clearly seen when dissected.

3. Shrinkage: The hole caused by the shrinkage of the casting exists in the thick part far from the gate or the product. The inner hole is irregular, and the hole wall has a metallic luster and has not been polluted.

Cause Analysis

1. Stomata

(1) Involved stomata

Reason: There will be gas in the mold cavity and the material tube (barrel, melting cup). During high-speed injection, because the gas is too late to be exhausted, it is wrapped by the turbulent aluminum alloy and exists inside the casting to form air holes. : There is pressure inside the pores. If the casting is heated to about 220 degrees, there will be raised bubbles on the surface of the casting. Sometimes the sound of bubbles may be heard when the heating is continued. Contaminated.

Solution

a. Find a way to exhaust the gas existing in the mold cavity and the material tube before die casting. At present, vacuum die casting and oxygen die casting can be used.

b. Write an article on the mold and find a way to exhaust the gas in the mold cavity.

c. The article on the die-casting process is always good. Some equivalent gas exists in a certain part of the casting, and it must be a defective product. We can use the die-casting process to disperse the gas that exists in one place. Divide into several portions to diffuse the stomata.

(2) Precipitated stomata

Reason: When the aluminum alloy is solidified from liquid to solid, the H dissolved in the aluminum alloy will precipitate to form hydrogen, and these hydrogen will remain inside the casting to form holes.

Representation style: Cut-out inspection, smooth inner wall, metallic luster, will exist anywhere in the casting.

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