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Ceramic foam filter Filtration principle

Ceramic foam filter Filtration principleCeramic foam filters, usually with poly urethane foam impregnated with ceramic: the slurry, then the slurry extrusion, and the rest covered in foam surrounding the fiber ceramic material, fired at high temperature sintering, poly urethane heat exploded, leaving foam ceramic products - ceramic foam filters. The filter can be used for various kinds of casting alloys, and the product has been commercialized. This filtration process has been fully promoted in industrialized countries, extensive use, become improve the mechanical properties of castings, reduce porosity, inclusions are the most simple and effective way.


In the foundry, since the non-metallic inclusions such as casting defects in casting waste usually accounts for 50% to 60% of the total waste. Liquid metal filter technique can effectively reduce or eliminate non-metallic inclusions therein, purifying liquid cast alloy. Ceramic foam filter is the use of polyurethane foam as the carrier, through hydrolysis after he dipped into the coating of a ceramic powder, binder, sintering aids, suspending agents, or the like, and then squeezing out the excess paint, the ceramic coating evenly coated spreads in the vector backbone become blank, blank and then drying and high temperature roasting. Ceramic foam filter by three kinds of physical and chemical effects of liquid metal, liquid separation cast alloy inclusions, to purify the liquid metal effect.


Complex ceramic foam structure, high efficiency mechanical slag when molten metal through the complex structure of the ceramic foam filters, mechanical separation by the action of the filter medium, the filter surface is greater than the perforations inclusions filtered and allowed precipitated in the liquid metal flows into the filter end, becomes an integral part of the filter. With the inclusion on the filter surface of the increase in the number of accumulation, and gradually formed a layer of "cake", the metal flow path, further thinning, thus new filter medium surface can be filtered more small inclusions at the same time, the internal filter media also have a role in a number of through holes in the ceramic body, some showed small slit, the presence of some dead, these changes are different regions may intercept position inclusions, internal filter there are also "cake" effect.


Surface effect: When the metal flow through the complex structure of the ceramic body, is divided into many small stream, increasing the liquid metal inclusions and the filter medium contact area and contact probability, since the filter surface is tiny concave surface, concave block size of about 1 ~ 10μm, inclusions electrostatic adsorption and adhesion closure effect.


Rectifying effect: when the flow of metal through the ceramic foam filter stream is divided into many small units, the smaller diameter, so that the Reynolds number (Re = vd / r) smaller, so that tends to flow Laminar Flow . When the liquid metal in a laminar flow state, the density of the molten metal is much greater than the density of inclusions. Thus the inclusions have sufficient time to remove floating, ie ceramic foam filters can assist runner slag. After pouring system placed filters help increase the flow of molten metal in the runner flowing liquid metal is easy to form full of movement, reduce the flow rate, is conducive to inclusion float and remain in the top runner.