Degassing Aluminum with Nitrogen: Nitrogen enters the bottom of the aluminum liquid through a certain process device. The nitrogen floats up from the bottom of the aluminum liquid in the form of bubbles. Due to the hydrogen partial pressure difference at the contact interface between the bubble and the molten aluminum, the partial pressure of hydrogen in the bubble is very low. When the hydrogen partial pressure tends to balance, the hydrogen in the alloy liquid continuously enters the bubbles. When the bubble rises to the liquid level, hydrogen will then escape into the atmosphere. While the bubble is rising, it will simultaneously adsorb the oxidized slag and its fixed impurities and make them float to the liquid level together. The inert gas should be condensed and dehydrated before use to prevent moisture from entering the aluminum liquid. The degassing refining quality is good, and the pores must be less.
The production practice of aluminum alloy has proved that hydrogen is the only gas that can be dissolved in large amounts in aluminum or aluminum alloy, and the most soluble gas in aluminum alloy.
Moisture: it comes from furnace gas, inadequately dried charge, refining agent, covering agent, modifier, under-dried furnace lining, crucible and paint on tools, and residual water on crucible, tools and charge solvent, these water vapors react with the aluminum to produce hydrogen, which enters the aluminum liquid in an atomic state.
The oil pollution comes from the furnace charge and tools with grease. The grease reacts with aluminum to generate hydrogen.
There are water-containing corrosion products on the charge. To reduce the absorption of gas by the aluminum alloy liquid, the alloy raw materials should be properly stored to prevent moisture. Before use, it needs to be fully preheated and dried; the melting crucible and tools should be fully preheated to remove moisture before use. In order to remove the gas in the aluminum alloy liquid, all the aluminum alloy liquid must be degassed and refined by Degassing Aluminum with Nitrogen before pouring molten aluminum.