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Wheel surface defects actually generated Analysis
Aug 30, 2017

Through a large number of experiments and exploration, according to the factors that affect the defects, combined with the actual production process of the process parameters, such as casting time, mold temperature, the initial determination of the existing casting process conditions to produce these defects.


The picture shows the forging aluminum alloy wheels,and Meika company's production equipment

1)Aluminum alloy liquid with rotary degassing refining degassing, requiring aluminum liquid gas content ≤ 0.20 ml / 100gAl, through the detection, aluminum alloy gas content of 0.16ml / 100gAl, reached the technical requirements, and no excessive, and the stomata basically Are distributed in the hub of the highest point, and some in the surface, and some in the very shallow skin, after shot blasting or mechanical processing will be revealed, and the distribution is not uniform, so the stomata is not determined because the aluminum of the gas precipitation produced by the precipitation of stomata, but the outside of the gas immersed in the aluminum alloy liquid generated in the immersion pores. The main reason for this submerged stomata is that the casting speed is too fast and the cavity is poorly ventilated. When the casting speed of the aluminum liquid is too fast and the cavity is poorly ventilated, the gas in the cavity is easily caught in the molten aluminum, and the gas is easily transferred to the upper part of the casting during the filling process. The place due to the rapid solidification of the metal casting, the entrapped gas will make it difficult to float the metal liquid and discharge the cavity, thereby forming a pore defect beneath the surface or shallow surface of the upper part of the casting.

2) in the hub of the surface shrinkage causes analysis

Through the exploration and testing, in the aluminum alloy wheel gravity casting, the coating thickness, alloy casting temperature and mold temperature on the surface shrinkage defects have a greater impact, in which the impact of mold temperature is particularly prominent. In the core temperature is too high or too low circumstances, may be in the wheel hub surface shrinkage defects, resulting in uneven surface. The hub buffer is relatively thin, and the hub around the thick wall thickness, aluminum alloy solidification process, the buffer chamber diaphragm plays a role in the role of the filling channel, the central riser on the hub and part of the spokes filling should be carried out through the partition. When the core temperature is too low, after the aluminum alloy liquid pouring in the hub of the plate solidification speed is faster, fill the channel closed too early, so that the central riser filling effect greatly weakened, so easy in the hub surface, especially in the the hub and the spoke are connected with a shrinkage defect. If the core temperature is too high, although the cooling rate of the separator, but also make the hub and spoke connected to the hot section of the solidification is very slow, when it is behind the solidification time of the partition, the central riser will loss of filling effect, the same will be in the hub surface shrinkage.

The actual production shows that the core of the mold core temperature of 450 ~ 480 ℃ more appropriate, that can make the center of the riser to play a better role in the filling. After the measurement, the thickness of the coating in the production, aluminum alloy casting temperature are in line with the requirements, but the core temperature is high, often above 480 ℃, so in the existing production conditions to reduce the surface of the surface shrinkage, the need to strengthen the core cooling, reduce the core temperature, speed up the center of the cylinder around the solidification rate.

3) Analysis of the causes of the arrears of the spokes

Metal type gravity casting, due to mold heat transfer fast, poor ventilation, so the casting wall is too thin, mold and aluminum pouring temperature is low, casting speed, poor cavity performance and other factors are likely to cause casting cast. It is not thin on the surface of the defect on the surface of the spoke, but the wall of the part is not thin, and the casting temperature and mold temperature of the alloy are relatively high (about 270 ℃ and about 450 ℃) ,The most likely cause of the undercurrent is that the casting speed is fast and the cavity is poorly ventilated. These two factors will make the casting filling the alloy fluid before the cavity pressure greatly increased, the alloy flow easily less than the discharge of gas in the parts of the parts, such as parts of the corner or the highest point, if the exhaust is poor or can not exhaust, it will produce a large back pressure, the alloy liquid can not be filled, resulting in parts less cast.

The wheel spokes is the use of exhaust line for exhaust, when the frequent emergence of the bar after the defects of the exhaust line to check and found that the exhaust line is blocked by a lot of aluminum, resulting in exhaust system exhaust performance greatly reduced. So to solve the wheel of the spokes less cast defects, in addition to appropriate to reduce the casting speed, more importantly, often check and clean the exhaust line to ensure that the exhaust system is smooth.