How to Prevent Secondary Pollution? The longer the casting launder, the greater the probability and degree of secondary pollution.
In theory, the purity of aluminum alloy melt should reach a higher level after refining in the furnace and online degassing and slagging. However, the actual results are often not ideal. One of the important reasons is that the slagging and gas suction conditions when the molten aluminum passes through the casting launder and the casting platform are ignored. The molten aluminum is in an “unprotected” state, and the absorbed gas and non-metallic inclusions are easier to flow into the cast rod, forming “secondary pollution”.
How to prevent secondary pollution, three measures can be taken when designing the purification system:
1. Shorten the length of the runner launder. Enter the mold from the casting water outlet, and the length of the launder shall not exceed 2 m. When dealing with the drop of the launder, instead of using the method of excessive tilting, the method of overlapping two sets of launders is adopted to ensure the stability of the liquid level to the greatest possible extent and prevent the aluminum melt from rolling and slagging.
2. The integrated design of filtration and degassing system saves the transfer process and shortens the length of the runner as much as possible.
3. The filter plate of the secondary filtration is directly placed on the crystallizer to ensure that the aluminum liquid is filtered directly into the casting, reducing the incidence of secondary pollution.
In addition, when refining in the furnace, the amount of refining agent is sufficient to ensure the refining time and avoid refining dead ends. Strictly implement the baking system of the casting system. These measures will have a positive impact on purity control.
In order to make aluminum rods with higher purity, you need to pay attention to several points:
1. When the alloy grade is changed, drain the aluminum liquid in the purification device and clean it up.
2. The launder mold plate must be thoroughly baked.
3. Use a covering agent to prevent inhalation when smelting in the furnace.
4. The runner mold plate must be installed in the previous shift and fully baked.
5. The production and maintenance of the runner mold plate adopts light-weight refractory insulation material, which has good air permeability, which is conducive to thorough drying and prevents air inhalation.
6. Blow off the scum on the surface of the ceramic foam filter before loading it, and check the blind porosity with light. It can be used only after it is qualified.