15 10月 Aluminium Nitrogen Degassing Machine
Aluminium Nitrogen Degassing Machine is used to control the levels of hydrogen, alkali metals and inclusions in the aluminum melt before casting.
In the past two decades, Aluminium Nitrogen Degassing Machine has been relatively comprehensively developed.
Hydrogen solubility and influencing parameters Aluminum melt always interacts with the atmosphere, forming a balance between the gaseous hydrogen in the air and the 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 alumina (inclusions) and hydrogen (gas).
Aluminum has a problem with hydrogen, not because it is particularly soluble in liquid aluminum, but because it is particularly insoluble in solid aluminum, so it will come out of the solution during solidification.
The solubility mainly depends on the temperature of aluminum. Please buy the aluminium degassing machine through email@example.com
The Aluminium Nitrogen Degassing Machine 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 affect the best removal method.
Atomic hydrogen is dissolved in liquid aluminum and is evenly distributed.
When a dry inert gas bubble is introduced into the melt, the hydrogen partial pressure inside 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 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 for smaller bubbles.
In addition, as the bubbles become smaller, the time each bubble stays in the melt becomes longer. This is because the terminal velocity decreases, which makes the hydrogen delivery time longer.
The deeper reaction zone allows more time to reach equilibrium, because the bubbles stay in the melt longer before reaching the surface.
Therefore, the Aluminium Nitrogen Degassing Machine needs to generate the smallest bubbles at the bottom of the processing container.
This is achieved at a high rotor speed; the melt is also mixed to obtain a uniform hydrogen distribution.
Spray gun processing is the beginning of industrial degassing, but spray guns often produce coarse bubbles between 10 and 50 mm in diameter, with a wide distribution of bubble sizes and providing limited melt homogeneity.
Breathable bricks, whether attached to the spray gun outlet or furnace bottom, produce typically finer bubbles of 10 to 20 mm in diameter; but even with them, homogenization and bubble distribution are not optimal.
Finally, the development of a rotary jet system with a rotor solved the problem of insufficient gas distribution and provided bubbles with a diameter in the range of 3 ~ 10mm.