Ceramic foam filter of aluminum is used to remove the oxide inclusions and provide high-quality molten aluminum for the casting process. Before the ceramic foam filter (CFF) filters the molten aluminum, it is necessary to fully preheat the ceramic sheet and the filter box to ensure that the molten aluminum can pass through the filter smoothly under the condition of uniform preheating. If the ceramic foam filter of aluminum is not uniformly preheated, the flow rate of the molten aluminum is fast in the high-temperature position, and the molten aluminum in the low-temperature position will easily block the filter hole, resulting in a slow flow rate of the molten aluminum.
The ceramic foam filter filtration process is the result of the combined effect of two factors: one is that the oxidized inclusions are transported to the filter, and the other is that the oxidized inclusions adhere to the filter.
Oxidized inclusions of small size adhere to the surface of the ceramic foam filter, and oxidized inclusions of large size are blocked on the surface of the ceramic filter due to mutual interaction. After the molten aluminum passes through the ceramic filter, the oxide inclusions are filtered to the surface, and the molten aluminum is purified.
However, the problem is that the number of oxidized inclusions filtered in this way is very limited. If there are too many oxidized inclusions on the surface of the filter, it will block the filter and affect the liquid level of the molten aluminum. Therefore, this filtering mechanism is only a rough filtration of the molten aluminum.
The main filtration mechanism of aluminum liquid in the thickness direction of the ceramic foam filter, and the main oxide inclusions with a size of less than 40μm are filtered through this filtration method.
When the ceramic foam filter of aluminum is filtering, the accumulation of oxidized inclusions is the key factor to improve the filtration efficiency. The oxidized inclusions aggregate, the particle diameter increases, and the removal efficiency of inclusions increases significantly. Using laminar staggered motion, a velocity gradient is generated in the melt, which can realize the collision and aggregation of inclusions and improve the filtration efficiency.
The main components of the ceramic filter system include: CFF filter box, ceramic foam filter, preheating burner. The ceramic foam filter is fixed in the filter box. When the aluminum liquid enters the filter box from the launder, it is filtered by the ceramic filter, and the oxidized inclusions in the aluminum liquid are filtered out, and the aluminum liquid is purified.
In order to ensure that the aluminum liquid passes through the micropores in the ceramic filter evenly and smoothly, the preheating of the filter is the most important factor. If the preheating temperature is not uniform, the molten aluminum is easy to pass through in the high-temperature position, and the molten aluminum in the low-temperature position is not easy to pass, and even the molten aluminum is easy to solidify in the low-temperature position of the filter and block the filter. Affect the filtering effect and the flow rate of the molten aluminum through the filter, thereby affecting the height of the molten aluminum level during casting, and adversely affect the equipment used in the casting process.
The best way to improve the preheating effect of the ceramic filter is to increase the flow of combustion air to form excessive combustion air in the filter box. On the one hand, it reduces the flame radiation temperature and at the same time disperses the hot air evenly in the CFF filter box to prevent local overheating, improve the preheating effect and the uniformity of preheating. In this way, when the molten aluminum enters the filter box and passes through the filter, the molten aluminum can evenly pass through the filter, preventing the partial area from being blocked or blocked due to uneven preheating.