Aluminum alloy melt filtration purification technology

[China Aluminum Network] Inclusions in metals, gases have a significant impact on the material's strength fatigue resistance, corrosion resistance, stress corrosion cracking performance and so on. Effectively controlling the oxide inclusions in the melt to improve the quality of cast rods is the common goal pursued by the aluminum industry. Currently, filtration purification methods are widely used to remove inclusions in aluminum alloy melts.
1. Formation of Inclusions in Aluminum Alloys A portion of the inclusions in aluminum alloys comes directly from the waste, and most of them are formed during the smelting and casting process, mainly oxide inclusions. All inclusions before casting are called primary oxidation inclusions, and can be classified into two types according to their size: one is the large-scale inclusions in the macrostructure, which discontinuously forms the alloy and reduces the compactness of the casting. It becomes the source of corrosion and the source of cracks, which significantly reduces the strength and plasticity of the alloy. The other type is fine dispersed inclusions. Such inclusions cannot be completely removed by refining, it increases the viscosity of the melt, and reduces the molten aluminum during solidification. The ability to feed. Secondary oxidation inclusions are mainly formed during the pouring process. During casting, the aluminum liquid is in contact with air, and oxygen and aluminum act to form oxide inclusions. The aluminum alloy is contacted with various components in the furnace gas during the smelting process to produce AL2O3 and other compounds. The Al2O3 in the aluminum liquid will increase the hydrogen content of the aluminum alloy melt. Therefore, the Al2O3 content in the aluminum liquid has a great influence on the formation of pores in the aluminum casting.
2. Filtration purification methods Foam ceramic filtration technology appeared in the 1970s. The use of ceramic foam filter plates is a more effective method for removing inclusions in aluminum melt. As for the metal filter and fiber cloth filtration, only large inclusions in the aluminum alloy melt can be removed, but inclusions below the micron level cannot be removed, and the metal screen also contaminates the aluminum alloy. The adoption of foam ceramic filter plates can filter out fine inclusions and significantly improve the mechanical properties and appearance quality of castings. It is the primary choice for casting workshops.
3. Use and selection of filter plate Foam ceramic filter plate is installed in the filter box between the furnace port and the diverter plate. The filter box is made of "Zhong Nai No.5" refractory material, which can pass through multiple chilling and heat stimulation. Without cracking, it has the advantages of high strength, good insulation properties, etc. It is currently a good material for making filter boxes, runners, etc. The closer the filter box is to the shunt plate, the better. This is because it can shorten the flow distance of the molten aluminum after filtration and reduce or avoid the re-production of oxides. The molten aluminum flows out of the furnace through the filter box and flows into the diverter plate through the flow cell. When the filter device is started, the drop before and after the melt filtration is about 50mm, but with the extension of the filtration time, the inclusions on the surface of the filter plate and the hole wall are increased, the filtration flow is decreased, the front-back drop is increased, and when the casting is completed, the drop increases. To 60-120mm. The choice of filter plate must be based on the flow of molten aluminum; secondly, the cleanliness of the melt, the higher content of inclusions and the total throughput of the melt should be taken into account. When designing the filter device, the filter plate should be submerged in the molten aluminum during the melt casting according to the specifications of the selected filter plate and the drop of the furnace port and the diverter plate. In addition, it must also be considered that installation and disassembly are safe and convenient. After the melt is cast, all the liquid in the filter box can be completely discharged. The surface of the filter plate has proved that the ceramic foam filter plate is currently a more effective tool for removing oxide inclusions in the melt. General fiber filtration can only remove large inclusions, while ceramic foam filter plates can filter out large inclusions and fine inclusions at the same time.
4. Filtration principle Foam ceramic filter plate has a multi-layer network, multi-dimensional through-holes, and holes communicate with each other. During the filtration, the aluminum liquid carries inclusions along the tortuous channels and pores, and is directly intercepted, adsorbed, and deposited when it comes into contact with the foamy skeleton of the filter plate. When the melt flows in the hole, the channel of the filter plate is curved, and the melt flowing through the channel changes the flow direction, and the inclusions thereof collide with the wall anvil and firmly adhere to the wall of the hole.
The main effect of the filter plate is its size and porosity to ensure that the larger the pores of the filter plate, the worse the de-slag effect. For aluminum castings with very strict requirements, the filter plate with small pores should be selected.
Foam ceramic filter plates are currently a more effective tool for removing oxide inclusions in the melt.

Centering Spot Drill Solid Carbide

Carbide Spot Drill, It is mainly to make small holes in advance at the position where drilling is needed to facilitate positioning during drilling. which can be used for drilling non-ferrous metals (aluminum alloy, copper), cast iron, alloy steel, low carbon steel, high hard steel, stainless steel, And various difficult-to-process materials, etc.;