Purity of Aluminium Alloy Improved by Degassing and Filtration

Theoretically speaking, the purity of aluminium alloy melt should reach a high level after refining in furnace, online degassing and slag discharging. However, the actual results are usually not ideal. One of the important reasons is that the aluminum liquid passes through the washing tank. Slagging and suction conditions during casting. At this time, the molten aluminum is in the “unprotected” state, and the absorbed gas and non-metallic inclusions are more likely to flow into the casting rod and form “secondary pollution”. The longer the washing time, the greater the possibility and degree of secondary pollution.

Purity of Aluminium Alloy

In view of the above problems, three measures can be taken in degassing and purification:

  • Shorten the length of the runner. The length of the sink shall not exceed 2 m when entering the mold from the casting water outlet. In order to ensure the maximum liquid surface stability and prevent the aluminum melt from rolling and dumping, the method of overlapping two sets of washing tanks is adopted instead of excessive inclination in the treatment of water tank drops.
  • The integrated design of the filtration and degassing system saves the transfer process and shortens the length of the chute as much as possible.
  • The ceramic foam filter plate of secondary filtration is directly placed on the filter box to ensure that the liquid aluminum is directly filtered into the casting to reduce the secondary pollution. When refining in the furnace, the amount of refining agent is sufficient to ensure refining time and avoid refining dead ends. Strictly implement the baking system of casting system. These measures will have a positive impact on purity control.

In order to improve the purity of aluminium alloy, the following points should be paid attention to:

  • After cleaning, the aluminum alloy liquid is discharged into the purification device.
  • The runner tray must be thoroughly baked.
  • When melting in a furnace, use a covering agent to prevent inhalation.
  • The runner tray must be installed in the previous shift and completely baked.
  • The production and maintenance of runner template adopts light fire-resistant and heat-insulating material, which has good air permeability, is conducive to thorough drying and prevents air inhalation.
  • Before loading, blow out the scum on the filter surface and check the blind hole.

It should be noted that the degassing and purification equipment has been put into use in an aluminum plant in March, and its operation is stable and the effect of degassing and slagging is ideal. But after the rainy season in June, the purification effect is greatly affected. It can be seen that environmental factors are important factors affecting the purity of melt. Melt purification is not a problem that can be solved only by advanced equipment. It needs comprehensive consideration and overall planning from the aspects of production management, equipment maintenance and process specification, so as to achieve a better effect.

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