Casting molten aluminum is an important step to obtain qualified castings. In order to prevent and reduce casting defects, the following matters should be paid attention to during pouring.
Before pouring molten aluminum, carefully check the molten aluminum temperature, ladle capacity and the dryness of surface coating, as well as the preparation of other tools.
Before pouring the molten aluminum, please carefully check the mold temperature and paint spraying conditions. BN coating is a key factor in metal mold casting. The cooling speed of the metal mould is fast, it does not shrink back and has no air permeability, which is basically improved by coating. The coating has low thermal conductivity and slow cooling rate, which improves the cooling rate of metal mold and prevents the casting from producing cold barrier and casting defects.
The talc powder in the coating has the function of demoulding, thus improving the influence of metal mold not sunken, that is, ensuring the mold taking, preventing the casting from producing strain, crack and deformation defects, and protecting the mold. Mold. The coating has a certain degree of exhaust, which can improve the problem of metal type without exhaust, and prevent the hole and pinhole defects. Therefore, we must pay attention to the role of BN coating.
It should not be poured under strong wind conditions to avoid strong oxidation and combustion of molten aluminum, which may lead to defects, such as oxide inclusions in castings. In particular, fans should not be blown to the melting furnace and holding furnace, let alone the ladle during casting.
When discharging aluminum from the crucible, please use the bottom of the bag to gently poke the oxide scale or flux layer on the surface of aluminum water, then slowly immerse the ladle into the melt, then use the wide mouth of the ladle to pull out the molten aluminum, and then lift the ladle steadily.
When handling the ladle, the palm must be flat, the pace must be stable, and the ladle should not be raised. The aluminum level in the ladle must be stable and undisturbed.
When pouring is about to be carried out, the slag of the ladle should be cleaned to prevent the slag and oxide scale from being brought into the casting during the pouring of molten aluminum.