In the late 1970s, the United States developed a Ceramic Foam Filter (CFF) made of alumina and chromium oxide. It not only has a good purification effect, but also is convenient to use. When the aluminum melt passes through, it only needs a pressure difference of 100 ~ 150mm. Once it passes through, it only needs to maintain a pressure difference of 2-10mm. Its purification principle is the same as that of ceramic tube filtration, and its porosity is as high as 80%-90%. Therefore, foam ceramic filter medium has a large flow capacity and is suitable for filtration purification in semi-continuous casting ingot and continuous casting rolling production.
A foam ceramic filter is a filter device using foam ceramic as a filter medium. It is installed in the filter box of the molten metal injection system between the static furnace and the casting table for filtering.
The choice of foam ceramic filter depends on the accuracy of filtration. Generally, 30PPI CFF filter can meet the requirements of aluminum liquid purification. If the aluminum liquid is dirty, a 20PPI filter can be used for pre-filtration to prevent premature plugging of the pore filter. This kind of large-diameter filter is also commonly used in the runner from the furnace to the standing furnace, and filter size is determined according to the casting speed and the metal flow rate per unit time.
Usually, the foam ceramic filter is horizontally disposed of in the filter box, allowing the aluminum water to pass vertically or vertically. When the aluminum water rises evenly, and the danger of channeling is reduced. In addition, when installing foam ceramics, the assembly parts must be sealed with fire-resistant fibers to eliminate any possibility of bypass.
It is better to heat the foam ceramic with a radiant heater to the melt temperature before filtering, so as to ensure that the aluminum liquid flows to foam ceramic without solidifying the metal and blocking the hole.