1 Characteristic of a new generation of ceramic foam filter molten metal filtration
In order to achieve the research and development goals we determined, a complete set of strict manufacturing technology has been studied from material selection, pulping and mixing, carrier
pretreatment, infrared drying, sputter coating, and microwave drying, to temperature field control of roasting. . The new generation of ceramic foam filter molten metal filtration developed can effectively improve the cleanliness of aluminum melt.
2 Mechanism of foam ceramic plate filtering and purifying aluminum melt
The mechanism of filtration and purification of aluminum melt by ceramic foam filter molten metal filtration is generally described as diffusion interception and inertial collision interception or screening mechanism, sedimentary layer, and deep bed filtration mechanism. The State Key Laboratory of Tsinghua University has established a three-dimensional physical model and a two-phase flow model for the filtration mechanism of foam ceramics and carried out simulation calculations, which are very helpful for us to study the filtration and purification of molten aluminum. The process of filtration and purification of molten aluminum by foam ceramic plate is very complicated, which is a complex process of high-temperature physical chemistry and metallurgical kinetics. As for screening, collision, sedimentation, interception, and filtration, it is relatively easy to understand. We have comprehensively analyzed many parameters obtained in the process of filtering aluminum melt with foam ceramic plates, and put forward the following insights:
(1) Through sieving collision interception, diffusion interception, friction, sedimentation, and other mechanical filtration, the filtration efficiency is proportional to the mesh aperture of the foam ceramic plate. The smaller the mesh, the stronger the interception ability of small particles of impurities.
(2) The effect of the deposition layer or the filter cake layer, with the deposition of the impurity particles in the melt and the curved interconnected and convex grid support walls in the filter plate, the ability to capture the impurity phase particles is improved.
(3) The rough surface formed by the gaps on the surface of the network support body increases the interfacial energy between the aluminum liquid flow and the ceramic body surface, which promotes the flow direction of the impurity particles in the aluminum liquid flow to be more disordered, which is conducive to the capture of solid particles. deposited
(4) Due to the microscopic cracks and pinholes on the surface of the network scaffold, the fluoride flux with a strong affinity for A2O3 particles is pre-deposited, which promotes the complete filter cake layer effect and strong chemical adsorption force, and makes the ability to capture and retain impurity phase particles. stronger
(5) During the metal smelting process and the temperature field effect of the heat transfer process, the concentration difference of the alloy solute will inevitably be formed, and the metal melt will be redistributed, integrated, and redistributed, and integrated again. This is also the alloying process. Some high melting point metals The phases and compounds re-aggregate and grow up, and the small impurities phase aggregate and grow up, which is beneficial to be captured by filtration. This can be explained by the changes in the concentrations of HAl2O3, Fe phase, and T phase before and after filtration. In particular, the effect of double-stage filtration or pore gradient thick plate filtration is more obvious. Therefore, under the same conditions, the new generation of ceramic foam filter molten metal filtration has a high removal rate of impurity phase in the aluminum melt, the change of static pressure difference before and after filtration changes more with time, and the change of aluminum melt amount before and after filtration is also obvious. . Of course, the smaller the pores of the selected foam ceramic plate, the more cleanliness of the aluminum melt can be improved.