Silver car wheel 5X120 4X100 5X112 aluminum alloy wheels

The reason for the formation of the cracking of the hub of the low -voltage cast aluminum alloy wheel

The cracks of low -pressure cast aluminum alloy wheels are mainly produced in the part where the stress concentration is produced, or the cracks caused by the unevenness of the stress due to the unevenness of the force, or the liquid solidification at the liquid pipe. Cracks are generally divided into two types: cold and hot cracks. Cold cracks refer to the cracks formed by the alloy when the temperature of the solid phase line is lower than its solid phase line. In layman’s speaking, cold cracks are produced by the casting stress on the casting when the casting is cooled to the low temperature. Cold cracks mostly appear on the surface of the casting, and there is slight oxidation on the surface of the crack: the heat cracks usually believe that due to the heat transfer effect of the wall during the alloy solidification process, the casting is always solidified from the surface. When a large number of branches appear on the surface of the casting, it is packed into a complete skeleton, and solid contraction will appear (often expressed by line contraction). However, at this time, there is still a layer of liquid metal film (liquid film) that has not yet been coagulated. If the contraction of the casting is not hindered by any obstacles, the effect of the branch crystal layer can be freely contracted, and there will not be no occurring will not appear. stress. When the shrinkage of the branch crystal is hindered, it cannot be freely contracted or the effect of tensile force will occur. At this time, the liquid film between the chinetic crystal will be stretched and deformed. Should be
When the strength limit of the liquid film is exceeded, the crystal is pulled open. However, there are still some liquid metals around the cracked part. If the liquid film is pulled open very slowly, and there is sufficient liquid around the surroundings and flowing in time in time, then the crack will be filled and “healing”. The casting does not have hot cracks. If the crack cannot be “healed” again, the casting will appear hot cracks. The surface of the hot crack is strongly oxidized, showing dark or black without metallic luster.