The type of CFF metal filtration can be divided into deep bed, filter cake, or mixed filtration. The efficiency depends on the pore PPI (number of holes per inch) of the filter material. It also relates to the size distribution of the particles to be removed. PPI refers to the plastic used to make ceramic foam, and the number of pore boundaries encountered per inch can be found from the average value.
The size range of a typical commercial CFF molten metal filtration is 10 to 80 PPI. 20-40 PPI is the most commonly used, used in industrial casting houses to achieve the required casting speed and the lowest acceptable filtration efficiency. The 10 to 20 PPI filter has poor particle retention, and is usually used to filter the large pieces of trapped, surface-spread oxides and other large particles produced during melting, storage and transportation.
High pore density ceramic foam filters with a value of 60-80 PPI are only suitable for quality-sensitive applications, such as surface critical extrusion and sheet products. The structure of CFF creates a unique tortuous path for fluid flow, thereby trapping inclusions and allowing a clean, smooth flow of metal into the cavity.
Important filter parameters are effective porosity (that is, the porosity that effectively contributes to the porosity), fluid tortuosity, specific surface area and pore size.
Ceramic foam filter dimension: 660x660x50(26″), 584x584x50(23″), 508x508x50(20″), 432x432x50(17″), 381x381x50(15″), 305x305x50(12″), 228x228x50(9″), 178x178x50(7″).
The CFF metal filtration process also depends on: alloy type, grain refiner, casting rate, metal temperature, etc. The grain refiner added before the filter has a particularly adverse effect on the filtration efficiency.
In terms of cost, ease of use, ceramic foam filter (CFF) is generally considered to be the acceptable performance characteristic of the “best” placement filter. Their main advantages are: high filtration efficiency, reduced turbulence, refractoriness and corrosion resistance, suitable for the most demanding casting applications.
