Under the production conditions, the central crack of the aluminum alloy round ingot is caused by the liquid hole being too deep, the beginning and the closing operation are improper. The basic reason for the crack is that the temperature difference between the inner and outer layers of the aluminum alloy ingot is large, the cooling rate of the inner layer of the ingot is greater than the cooling rate of the outer layer, and the shrinkage of the inner layer is hindered by the outer layer that has already been condensed, which is the diameter plane of the central layer of the aluminum alloy ingot. The reason for the tensile stress is formed. This stress is continuously enhanced from the moment of crystallization to the complete cooling of the ingot, and cracks are generated when the allowable deformation ability of the metal is exceeded. At the beginning and end of the ingot, the normal casting conditions are destroyed, the cooling conditions are extremely uneven, and additional thermal stress is generated, which is also an important element leading to the center crack.
The fundamental method to prevent central cracks: First, strictly control the chemical composition and impurity content according to the internal standard, improve the ability of the alloy to resist cracking; second, prevent the melt from overheating or staying in the furnace for too long, and prevent the bottom and mouth clips Slag. In operation, it is important to adjust the temperature and stress field inside the ingot by adjusting the depth of the hole to reduce the temperature difference between the inner and outer layers of the ingot. The specific method is as follows:
1 reduce the casting speed;
2 Properly increase the cooling water pressure;
3 to prevent the use of a small funnel, uniform liquid flow;
4 Appropriately increase the level of the molten metal in the mold. For direct hard alloy ingots with a relatively high crack tendency, a low tiling (or a 2-3 mm thick thermal insulation station on the aluminum alloy ingot base) and a mouth tempering measure should be taken to prevent the bottom crack and the mouth. occur.
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