Analysis And Control Of The Main LPDC Defects Of Aluminum Alloy Wheels

Low pressure die casting(LPDC) is the most widely used method in the product of aluminum alloy wheel casting. In CITIC Dicastal Co., Ltd(CITIC Dicastal), about 90% of the wheels are produced by the way of the LPDC. Comparing to other casting methods, although the LPDC have many advantages, but the existence of casting defects is still a huge challenge to the quality and cost of the products. According to statistics, 90% of the wheel that is scrapped in CITIC Dicastal every year is caused by the casting defects, which lead to serious losses of the manufacturers. Therefore, it is of great significance to study the casting defects in the LPDC process.In this paper, the defects in the LPDC process were analyzed, including the defects formation mechanism and its harm. Also, the measures of prevention was put forward to provide the reference for the production process.In order to find the bad effects of casting defects on product properties, combining with the actual production, the 13°impact tests of 02111C01 wheel in CITIC Dicastal was carried out, and its failure reason was analyzed. Results showed that the defects of shrinkage and porosity was the main cause of the failure. Also, the bending fatigue experiments of 00211C01 wheel and 02211C01 wheel were carried out. As the failure analysis result, the cooling rate of the wheel heart area of 00211C01 wheel was too slow, which cause the bad local silicon metamorphism and poor performance. There were a small amount of shrinkage defects in 02211C01 wheel and the main failure reason was the wheel structure problem. The shrinkage casting defects reduce the elongation of the product, which made the anti-fatigue performance degradation.The UG NX software was used to establish three-dimensional physical model of the wheel, and the Pro CAST software was used to simulated the LPDC process of the wheel. Combining with the simulation results, the wheel structure and cooling process parameters were optimized. Research results showed that hot spots were easy to form in the connection part of the spokes and the rim and the flange part in the LPDC process and which would lead to shrinkage defects. In the wheel design, it is important to ensure the cross section area of wheel keep decreasing trend from wheel center to the rim. To enhance the cooling effect and prevent shrinkage porosity defect, cooling measures should be taken in the areas that the hot spot was easy to form.The research result has a good guiding significance for the prevention of casting defects, the structure design and the cooling process design of the wheel.