The aluminum melt degassing of die-cast aluminum alloy is very important to the mechanical properties of the casting. Hydrogen absorption is the main reason for the formation of pinholes in aluminum alloy castings and reduces air tightness and mechanical properties. Therefore, various measures must be taken to strictly control the content of hydrogen and other gases.
Aluminum Melt Degassing Measures
Before entering the furnace, the rust and oil stains of the charge must be strictly removed and preheated to the specified temperature.
The furnace should be baked before adding the feed to remove the moisture in the furnace to prevent moisture and hydrocarbons from contacting the feed.
Before coming into contact with the aluminum alloy melt, it should be fully preheated to remove moisture, and a layer of paint should be applied to the surface of the iron tool.
Control the smelting temperature and time, prevent the aluminum alloy melt from overheating and generate gas, and use a refining agent to refine the aluminum alloy melt. The refining agent must be completely dried before use.
The hydrogen contained in the molten aluminum is precipitated by flushing the molten aluminum in the transfer package with an inert gas to reduce the hydrogen content in the molten aluminum alloy.
Gas treatment refers to transporting the molten aluminum in the transfer package to the aluminum degassing unit, and filling the molten aluminum with inert gas through the vent holes on the graphite rotor to precipitate hydrogen, thereby reducing the hydrogen content in the molten liquid. In the normal smelting operation, the transfer degassing process is optimized and improved, and different types of inert gases are used to fill the transferred aluminum alloy melt, so that the hydrogen contained in the aluminum alloy melt can be effectively precipitated, thereby reducing the aluminum content. Density value of alloy melt.
We choose two different types of inert gases: nitrogen and argon, mixed in different proportions, and then degassed during transportation. From the experimental data, it can be found that if a higher proportion of argon is used for transfer degassing, its density value will be significantly reduced, but in terms of degassing use, the production cost will increase by more than 25%. After a comprehensive discussion and considering factors such as controlling production costs, the research finally decided to use nitrogen.