Filtration Mechanism of Ceramic Foam Filter for Casting

 The ceramic foam filter for casting separates the inclusions in liquid casting alloy by three physical and chemical actions of molten metal, so as to achieve the effect of purifying molten metal.

 

1. Filter cake effect

The complex ceramic foam structure can efficiently block the slag mechanically. When the metal liquid passes through the complex ceramic foam filter, the filtration medium can filter out the inclusions larger than the pore size of the filter by mechanical separation, and deposit them in the molten metal's inflow end of the ceramic foam filter. With the increase of inclusions on the filter surface, a layer of "filter cake" will be formed gradually, which will make the metal flow channel become narrower step by step. Therefore, the surface of the new filter medium can filter out the finer inclusions. At the same time,  the inside of the medium also has the function of filtering. In many small holes penetrating through the ceramic body, some have small slits, and some have dead corners. These different areas are all possible locations to intercept inclusions. There is also a "filter cake" effect inside the filter.

 

2. Surface effect

When the molten metal flows through the ceramic body with complex structure, it is divided into many small streams, which increases the contact area and contact probability between the inclusions in the molten metal and the filter medium. Because the surface of the filter is very small concave surface, it has electrostatic adsorption and adhesion effect on the inclusion.

 

3. Rectification effect

When molten metal flows through the ceramic foam filter, it is divided into many small units, and its diameter is small, making the liquid flow tend to laminar movement. When the molten metal is in laminar flow, because the density of molten metal is much larger than the density of inclusions, the inclusion has enough time to float up and remove, that is, the ceramic foam filter can assist the runner to stop slag.