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What are the causes of defects in aluminium alloy die castings?
Release time：2019/6/4 0:50:29 | Source of information：Dongguan zhongding precision mould co. LTDDongguan Zhongding Precision Die Co., Ltd. is an enterprise specializing in the design and production of zinc alloy die-casting dies, aluminum alloy die-casting dies, magnesium alloy die-casting dies and die-casting products processing. It provides one-stop service from materials, dies, die-casting, post-processing and surface treatment. To provide professional die casting die and product processing for many top 500 enterprises in the world, the causes of shrinkage and porosity defects in die castings are due to liquid shrinkage and solidification shrinkage of metals larger than solid shrinkage. When sequential solidification is carried out, holes will be formed where liquid metal is not replenished at the final solidification point. Large and concentrated holes are called shrinkage holes, while small and dispersed holes are called shrinkage holes. Its prevention methods are as follows:
1. Casting structure should be designed reasonably and the thickness should be uniform in order to reduce hot spot.
2. For castings with uneven thickness, the thickest part should be placed at the top of the castings in order to add risers.
3. The inoculation amount of cast iron can be increased appropriately.
4. Correct selection of pouring position and system to cause simultaneous or sequential solidification. The compactness of sand moulds should be appropriate.
5. Ensure that the castings are solidified sequentially, leading shrinkage and porosity into risers. Therefore, it is necessary to select the casting position correctly when pouring, and to place chilled iron in different parts of the casting with different thermal conductivity to control the cooling rate of each part of the casting, which results in the condition of sequential solidification in the direction of riser.
6. Increase the feeding effect of riser. Place large and large enough risers in proper places to ensure adequate liquid metal for close feeding of castings.
7. Select and control the composition of liquid metal to minimize the shrinkage of liquid metal.
8. Correctly choosing pouring temperature and pouring speed can reduce pouring temperature and pouring speed without increasing other defects.
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