The presence of hydrogen and fine particles in cast products is a serious problem because the final products processed on cast rods (such as continuously formed bars and wires) have a poor grain structure and therefore reduce mechanical properties. Moreover, when the product is used as a conductor, the presence of undesirable ingredients can severely reduce the conductivity of the product. The purity of molten aluminum must reach a certain standard, and the molten metal needs to be purified. Most aluminum foundries use the following degassing and filtering methods: refining flux and inert gases are used to reduce the hydrogen content, and ceramic foam filter plates are used to remove finely divided solid particles.
Conventionally, molten metal is fluxed in batches by processing the melt in a holding furnace or in a ladle. However, since this method is time-consuming and requires a large amount of flux gas, this method is not entirely satisfactory. In addition, even after batch fluxing, due to the reabsorption of hydrogen and the further generation of hydrogen through the reaction of the metal with the moisture that may exist in the entire system, a large amount of hydrogen will usually remain in the casting. In addition, although methods of filtering molten metal through refractory filters are generally satisfactory in removing finely divided solid particles, they are not advantageous in significantly reducing the gas content of molten metal.
AdTech provides a two-stage tandem processing system for degassing and filtering molten metals, especially aluminum and aluminum alloys. The molten metal is melted in the first stage of the degassing system to remove hydrogen, and then filtered through a CFF filter. The granular filter media contained in the second stage is used to remove finely divided solids from it.
The processing principle of on-line degassing equipment is the principle of gas flotation. The process gas (inert gas or a mixture of inert gas and chlorine) is injected into the melt through the rotor and broken into uniformly dispersed tiny bubbles by the rotor, and the tiny bubbles rise to the melt on the surface, the following tasks are completed during the rising process of tiny bubbles:
- Hydrogen is absorbed into the bubble and is eliminated;
- Alkali metals are eliminated by chemical interaction with chlorine gas (formation of chloride);
- The inclusions are trapped by bubbles and then rise to the surface of the melt to form dross.
