According to the actual production situation of cast rolling, the dissolved hydrogen is the most easily dissolved gas in molten aluminum, and its content accounts for 90% of the dissolved gas. Hydrogen is an important cause of porosity, loose strip and peeling in casting and rolling and the next process (aluminum alloy is easy to absorb hydrogen and oxidize in the melting process, which makes the aluminum melt contain a lot of inclusions). Molten aluminum flux purification in furnace is widely used in aluminum foundry.
The measures to reduce the hydrogen content are as follows:
(1) reduce the moisture content of the charge.
(2) Control the nature of furnace gas (no over temperature, furnace preparation).
(3) Cover with covering agent.
(4) Thorough refining and degassing.
Commonly used aluminum casting fluxes include covering agent, refining agent, cleaning agent, slag agent. The covering agent is alkaline earth metal chloride. Function: (small surface tension, good wettability) covering and isolating liquid aluminum, reducing the suction and burning loss of liquid aluminum. Refining agent (fluoride) function: adsorb dissolved Al2O3 and other slag inclusion, facilitate slag aluminum separation, increase purification effect (refining, filtration).
No matter flux slag removal or other refining methods, the oxide inclusions suspended in the melt can not be separated, especially the suspended alumina inclusions, which are more difficult to remove. In addition, it is inevitable to reabsorb during the process of liquid aluminum transfer. Therefore, in order to further improve the effect of purification treatment and ensure the stability and reliability of liquid aluminum quality, the on-line treatment method must be used to remove hydrogen and inclusions in the melt. Compared with the molten aluminum flux purification treatment, the on-line treatment has better purification effect, no secondary pollution of melt. The continuous and automatic production can be realized by combining with continuous casting and rolling.
There are many on-line treatment methods, which can be divided into the main functions of online degassing, slag removal, and gas slag removal. Ceramic foam filter filtration is a filter made of alumina ceramic. The inclusions suspended in the melt are mechanically blocked by the filter or chemically interact with the filter material, so that the inclusions are removed from the melt.