Nitrogen degassing device has the advantages of simple structure, no pollution of liquid aluminum, long service life and simple maintenance. It is widely used in aluminum alloy casting in China.
During smelting, the metal aluminum reacts with water vapor to form hydrogen gas that dissolves into the aluminum solution. Hydrogen is removed from the liquid aluminum as it solidifies.
If the hydrogen content in liquid aluminum is too high, pores are easy to form in the casting, which reduces the mechanical properties of the casting and may lead to the scrap of the casting.
Hydrogen is a noxious gas in liquid aluminum. The pre-furnace test of liquid aluminum hydrogen content is an important procedure to ensure casting quality. Especially in the precision die casting process, the use of nitrogen degassing device to remove hydrogen and slag will become an indispensable deficiency.
Nitrogen Degassing Device Degassing Principle
The liquid aluminum is stirred by a controllable rotating graphite shaft and a rotor. The measured inert gas is pressed into the liquid aluminum through the rotor and dispersed into small bubbles, which are evenly dispersed in the liquid metal. The gas partial pressure is zero for bubbles.
Due to the high partial pressure of hydrogen in liquid aluminum, hydrogen in liquid aluminum continuously diffuses into bubbles, while some non-metallic inclusions in liquid aluminum adsorb on the surface of bubbles, and some non-metallic inclusions are inert adhesion of hydrogen and some non-metallic inclusions. Bubbles rise to the surface.
When a special degassing filter box is available, the impurities are isolated before pouring and then desulphurized and deoxidized by the slag. Degassing principle is also recognized, high efficiency, does not affect production. Process.
It can improve the purity of liquid aluminum in a short time, reduce the scrap rate, improve the production efficiency, improve the mechanical properties of castings, and enhance the competitiveness of products, which can not be achieved by the traditional degassing method.
In the application environment of liquid aluminum, graphite material and alumina material, silicon carbide material can be used for stirring, but due to the graphite rod itself has high temperature resistance, low thermal expansion coefficient (resulting in high temperature and low temperature conversion will not crack), moderate strength, high purity, and no reaction with liquid aluminum.