30 PPI foam filter is suitable for aluminum alloy castings. The choice of ceramic foam filter is very important for a good filtration effect and no pollution to the alloy. Many practices show that the use of ceramic foam filters can remove inclusions, improve the structure of castings, improve the mechanical properties and qualified rate of castings, improve the processability of castings and reduce the processing cost. However, if it is not used properly, it will not only fail to achieve the expected effect, but also bring troubles to the production, and even increase the reject rate of castings.
The choice of ceramic foam filter material depends on the type of casting alloy and pouring temperature. Steel castings are usually made of zirconia. Cast iron is usually made of silicon carbide. Large cast steel and cast iron can be made of silica gel. Aluminum alloys are usually made of alumina and magnesium alloys are usually made of magnesium oxide.
The choice of ceramic foam filters is usually:
10 holes/inch (10 PPI Foam Filter) can be used for ductile iron large gray iron parts and steel castings.
20 holes/inch (20 PPI Foam Filter) is suitable for small gray cast iron, malleable iron, and non-ferrous metal castings.
30 holes/inch (30 PPI Foam Filter) is for copper alloy castings and aluminum alloy castings.
The thickness of the alumina foam ceramic filter is selected based on the mechanism and purification method of foam ceramic filter. In order to give full play to the purification function and withstand the influence of high-temperature metal flow, the filter must have a certain thickness to prevent the filter from burning. Burning through the filter will cause slag and scrap the casting.
The thickness of light alloy castings (such as small aluminum alloy) is 12 ~ 15mm.
The thickness of large non-ferrous alloy castings is 20-25 mm.
The iron casting is 10-22mm.
Steel castings ≥ 20 mm.
The ceramic foam filter is placed in the runner and the design and casting production of the gating system including the filter, the ceramic foam filter can be placed horizontally at the bottom of the runner, horizontally or vertically in the runner and the internal flow channel; the vertical split type filter can be placed on the side of the gate. In order to avoid the turbulence of molten metal, the gate system is usually designed to be semi-closed or open, and the size of the relevant unit of the gate system must be increased due to the flow resistance of the filter.