Whether it is flux slag removal or other refining methods, the oxide inclusion particles suspended in the melt cannot be separated clean, especially the suspended alumina inclusions, which are more difficult to remove. Moreover, in the process of transferring molten aluminum, it is inevitable to re-oxidize and get gas. Therefore, in order to further improve the effect of the purification treatment and ensure the stability and reliability of the quality of the molten aluminum, it is necessary to use an online molten aluminum purification method to remove the hydrogen and inclusions in the melt.
Compared with aluminum casting flux furnace processing, online molten aluminum purification processing has a better purification effect and prevents secondary pollution of the melt. Cooperating with continuous casting and rolling, it can realize continuous and automatic casting and rolling production. There are many on-line processing methods. According to their main functions, they can be divided into degassing, slagging. Filtration is to allow the melt to pass through a filter made of neutral or active materials. The suspended inclusions 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.
Ceramic foam filter is a new type of filter material developed in recent years. It is generally made into a filter with a thickness of 50mm and a length and width of 200~600mm, and the porosity is generally 10~60ppi. Its function is to remove oxides and non-metallic particles in aluminum alloy. The filter is set between the static furnace and the casting and rolling mill, and in the filter system after the online degassing unit. When the aluminum liquid passes through the channel of the filter, the inclusions are adsorbed, blocked, and captured by the pores due to the combined effects of gravity retardation and adsorption. The filtration accuracy of the filter is related to the thickness and porosity. It is characterized by easy use, good filtering effect, and no high pressure head is required for filtering.
In the rotating inert gas flotation method, the purified gas is sprayed through the rotating nozzle and broken into countless tiny bubbles by the high-speed rotating impeller, which are evenly distributed in the melt, thereby expanding the gas-liquid contact surface. The tiny bubbles rotate and rise in the melt, effectively prolonging the residence time of the bubbles in the melt. At the same time, the strong stirring effect of the rotating nozzle accelerates the renewal of the gas-liquid interface between the gas and liquid phases, effectively improves the mass transfer conditions, and strengthens the diffusion process so that the small bubbles can fully play their role.