4. The casting product is incomplete.
Due to the low pouring temperature, the casting solidification speed is accelerated, and the casting is not fully poured and solidified, resulting in insufficient pouring. Because the channel of gating system is narrow and the flow of molten aluminum is small, a bottleneck is formed; When the pouring flow is less than the filling speed of molten aluminum, insufficient pouring will be formed and become waste.
Preventive measures: redesign and improve the gating system and increase the flow of molten aluminum; Preheat the mold and avoid too fast cooling speed of molten aluminum during pouring; The coating shall be reasonably distributed in the cavity, the thickness shall be moderate and uniform, and the coating shall not be too thin; Measures such as ensuring smooth mold exhaust can effectively eliminate the waste products formed by insufficient pouring.
5. Shrinkage and loosening
Due to the high liquid temperature and pouring temperature of aluminum alloy, slow cooling speed and large shrinkage, the grain is coarse and the structure is not dense, forming shrinkage casting waste.
Preventive measures: improve the process, operate carefully, and control the alloy heating temperature and pouring temperature; The riser size shall be designed scientifically and reasonably, and the coating shall not be too thin or too thick to ensure the shrinkage supply of castings; The casting design shall be symmetrical as far as possible, and the thickness difference shall not be too large.
6. Oxidation slag inclusion and air hole
Due to improper operation, splashing occurs when molten aluminum enters the mold cavity, forming bubbles, which are wrapped inside the casting, making the metal oxidized and forming oxidized slag inclusion; When there is a large amount of small volume hydrogen in liquid aluminum, irregular small holes will be formed, which are mostly seen in thick and large sand castings, and the physical and chemical properties will be greatly reduced.
Preventive measures: careful operation. During pouring, the flow rate of molten aluminum shall be stable and moderate to reduce the impact force. It is appropriate to adopt serpentine gate and bottom pouring system; Strictly check the cleanness of furnace charge, formulate reasonable melting temperature and pouring temperature of aluminum alloy, refine and degassing, etc.