The aluminum nitrogen degasser is used to control the content of hydrogen, alkali metals and inclusions in the aluminum melt before casting.
In the past two decades, aluminum-nitrogen degassing machines have been relatively comprehensively developed.
Hydrogen solubility and influencing parameters Aluminum melt always interacts with the atmosphere, thereby forming a balance between gaseous hydrogen in the air and hydrogen in the aluminum melt.
But the partial pressure (ie content) of hydrogen in the atmosphere is almost irrelevant.
Therefore, hydrogen comes from water vapor in the atmosphere, and water vapor easily reacts with liquid aluminum to produce two problematic reaction products, namely aluminum oxide (inclusion) and hydrogen (gas).
Aluminum has a hydrogen problem, not because it is particularly soluble in liquid aluminum, but because it is particularly insoluble in solid aluminum, so aluminum will precipitate out of the solution during solidification.
The solubility mainly depends on the temperature of aluminum. Please purchase aluminum degasser through sales@alalloycasting.com.
The aluminum nitrogen degasser needs to remove hydrogen from the melt before purging the melt with inert gas nitrogen.
Understanding the hydrogen removal mechanism is essential to determine and influence the factors that influence the best removal method.
Atomic hydrogen is dissolved in liquid aluminum and distributed evenly.
When the dry inert bubbles are introduced into the melt, the internal hydrogen partial pressure is almost zero.
In the nitrogen bubble, a local equilibrium is quickly established between the H concentration and the H partial pressure in the molten boundary layer.
The diffusion rate of hydrogen from the human body to the boundary layer is limited, and the recombination of hydrogen from atoms to molecules is very fast.
The hydrogen concentration in the bubbles increases as they rise to the surface of the melt.
The transfer rate of hydrogen is not only related to the diffusion rate, but also to the total area of the bubble interface.
A given flow of inert gas has a larger interface area and can accommodate smaller bubbles.
In addition, as the bubbles become smaller, the time each bubble stays in the melt becomes longer. This is because the end velocity is reduced, which makes the hydrogen delivery time longer.
A deeper reaction zone allows more time to reach equilibrium because the bubbles stay in the melt for longer before reaching the surface.
Therefore, the aluminum nitrogen degasser needs to generate the smallest bubbles at the bottom of the processing vessel.
This is achieved at high rotor speeds. The melt is also mixed to obtain a uniform hydrogen distribution.
Spray gun processing is the beginning of industrial degassing, but spray guns usually produce coarse bubbles with a diameter between 10 and 50 mm, with a wide distribution of bubble sizes and limited melt homogeneity.
Breathable bricks, whether they are connected to the spray gun outlet or the furnace bottom, will generate small bubbles with a diameter of usually 10 to 20 mm; but even with them, the homogenization and bubble distribution are not optimal.
Finally, the development of a rotary jet system with a rotor solves the problem of insufficient gas distribution and provides bubbles with a diameter in the range of 3~10mm.
