Rotary Degassing Machine

タイトルまたは説明

ROTARY DEGASSING MACHINE

Aluminum alloys dissolve hydrogen in its surroundings very quickly, ie; the hydrogen in the air and in the refractories it contacts, is dissolved in the liquid aluminum. During the solidification of aluminum, the opposite is true: The hydrogen dissolved in the aluminum is gasified during the solidification process, nucleating on the oxide films to form voids in the casting.

The strength of the casting part drops due to that gas cavities. In order to prevent this undesired formation, Gas and Oxide Removal Process is applied to aluminum metal before casting. This process can be applied by chemical tablets, by introducing an inert gas through a pipe into the liquid metal, by introducing an inert gas into the liquid metal via a rotating rotor, or by ultrasonic vibration. However, the most preferred method because of both high efficiency and low cost is to introduce an inert gas into the liquid aluminum through a rotating rotor. (Rotary Degassing)

The inert gas used is usually nitrogen and / or argon. The rotary rotor distributes the inert gas in the form of small gas bubbles, significantly increasing the contact surface with liquid aluminum. The gas bubbles, which are moved toward the upper surface of the liquid metal, attract the dissolved hydrogen in the metal they are in contact with, and they also transport the oxide films they meet. Thus, liquid aluminum is removed from dissolved hydrogen gas and floating oxide films. One or two vortex cutter plates mounted on the side of the rotor are used to counteract the risk of creating new oxide films of the vortex formed by the rotating rotor.

Important parameters in this process, which is a sine qua non of a quality casting, are the rotor speed, the flow speed of inert gas and the application time. The rotary degassing machine is expected to control these three parameters. Since the level of gas and oxide in the molten aluminum in each foundry will be different, each foundry must set its own gas and oxide removal parameters. This work is done using the Density Index Measurement Device.