Common problems of aluminium alloy casting
The solidification temperature range Al - Cu alloy is wide, the feeding problem occurs in the casting is easy to form dendritic shrinkage. Shrinkage is in the late solidification stage, the liquid phase in the solidification zone is divided into small isolated molten pool by dendrite, and the small molten pool shrinks when it is solidified and can not be compensated. An alloy with a wide range of crystallization temperatures is most likely to form shrinkage. Al - Cu system and Al - Mg system are solid solution alloys, which tend to form grain boundary shrinkage. Al-Si alloy is eutectic alloy, which is easy to form concentrated shrinkage.Cold insulationThe cold septum presents a crack like crevice, but the gap has rounded edges. Most of the cold separation defects are formed by clogging of the flow head. The main measures to solve the cold separation defects are to improve the filling ability of the metal liquid, including increasing the pouring temperature, improving the mold temperature, improving the exhaust, optimizing the design of the gating system, etc..
There are two main reasons for the thermal crack: the solidification mode of the casting and the casting stress during the solidification process.The casting has a wide range of solidification temperature, the alloy is mushy or volume solidified, and the Al - Cu alloy belongs to this kind.Shrinkage and porosityShrinkage hole surface roughness, irregular shape, usually appear in the final position of solidification casting and hot spot. The Al - Si alloy forms a centrally concentrated shrinkage hole at the point where the casting is inadequate.
Common problems in casting aluminum alloy are porosity, cracks, shrinkage and shrinkage, cold separation.Stoma:From the causes of formation and formation of stomata, stomatal defects can be divided into five types: invasion pores, inclusion pores, and analysisStomata, endogenous reaction pores, and exogenous response pores. Among the aluminum alloy castings, the longest one is the first three kinds of porosity defects.Crackle：
