It is needed the Aluminum Melt Refining in the lone smelting process. Because the aluminum Melt is easy to oxidize, inhale, and absorb metal impurities. Therefore, it is very easy to be polluted during the smelting process. Preventing the contamination of impurities is an important issue in the smelting of aluminum and aluminum alloys. The purification of aluminum alloy melt is a key technology to ensure the metallurgical quality of aluminum alloy materials, and it is a problem that has been widely concerned by academia and business circles. The aluminum melt degassing and refining is mainly to reduce the hydrogen content and the content of oxide inclusions in the melt.
The hydrogen content required for the cleanliness of aluminum alloy melts is generally 0.15m1/100gA1 at the domestic advanced level, and 0.10m1/100gA1 at the international leading level. Oxidized inclusions are not allowed to have micron-sized particles and aggregates. It can be seen that the cleanliness requirements of aluminum alloy melt are very strict.
Al2O3 inclusions are fine, and the specific gravity is similar to that of Al, floating in the molten aluminum. The relationship between inclusion and [H].
a) The Al2O3 film on the surface can protect the molten aluminum from further oxidation.
b) At the same time, the supersaturated [H] cannot diffuse into the atmosphere.
c) When the temperature is >900℃, y-A1203 transforms into aA1203, the specific gravity becomes larger, the film cracks, the α-Al203 film sinks, the aluminum liquid inclusions increase, and it must be melted at low temperature.
Aluminum Melt Refining
The process principle of eliminating pores and oxidized inclusions can be summarized as: “prevention”, “exhaust” and “solution”.
- “Preventing” is to prevent gas and all kinds of dirt from entering the molten furnace.
- “Exhaust” is to eliminate oxidized inclusions and hydrogen in molten aluminum.
- “Solution” means that the hydrogen in the molten aluminum can be partially or even completely dissolved in the alloy structure during solidification, so as not to generate pores in the casting.
To arrange and select three sets of technological measures of “prevention”, “discharge” and “solution”, the principle of “prevention first and discharge second” must be mastered in the smelting process. Practice has proved that the focus of the best refinement method is still the word “prevention”. The effect of “melting” is obvious. When metal mold casting, die casting, low-pressure casting, negative pressure casting and squeeze casting are used, qualified castings can be obtained with poor quality molten aluminum.