1 filter

 

Filtration is an important function of foam ceramic filter. It can be classified into three aspects. For the sake of clarity, we use molten iron for example, and the application of filter net can also be cast steel, cast copper and cast aluminum).

 

(1) floating molten iron separated from the pouring cup. Due to the placement of foam ceramic screen at the bottom of runner or runner, the molten iron can stop for a short time, so that the inclusions with low density and molten slag are separated from molten iron. This phenomenon continues when the runner is in full state.

 

(2) Surface filtration (two-way filtration) large slag and other inclusions that do not float are captured by the surface of the filter screen when molten iron passes through the filter screen. Moreover, the captured inclusions form finer filter holes with the filter screen, so as to capture the subsequent inclusions and improve the filtration effect. However, this surface filtration will not only keep the filter hole blocked, but also worsen the pouring condition.

 

(3) internal filtration (three yuan filtration) internal filtration is an excellent filtering function of foam ceramic filter screen. The inclusions not removed by the above two filtering functions are repeatedly contacted and collided with the filter frame with large surface area when the molten iron passes through the zigzag channel inside, so as to adhere and remove. Moreover, the main SiC on the surface of the skeleton is oxidized into very thin glassy SiO2 during roasting. During the filtration process, SiO2 is softened by the heat of molten iron, which produces a "slime glue" effect on the inclusions, making it difficult for the inclusions that collide and contact with the skeleton to escape.

 

2. 2 rectifier

 

The setting of filter screen in the pouring system not only avoids slow pouring because of its large porosity, but also makes the molten iron flow stable due to its ternary skeleton structure, realizes the ideal "uniform pouring" and simplifies the pouring technology. In addition, it also has the following functions:

 

(1) Prevent eddy current. When pouring the sprue with small capacity, the gas is filled first than the molten iron. Setting a filter screen can prevent the molten iron from generating eddy current in the gate cup at the initial stage of pouring, avoid air involvement, and is conducive to the floating of inclusions.

 

(2) When the iron flow passes through the filter screen and collides with the skeleton, not only the flow velocity but also the flow direction changes. The molten iron is evenly and smoothly injected into the mold cavity, which greatly reduces the oxidation degree of molten iron.

 

(3) When the uniformly stirred iron flow passes through the filter frame, it is continuously separated and then closed until the action of the stirred iron and the uniform composition can make the added alloy, inoculant and spheroidizing agent more uniform. Therefore, it has special effect on in mold inoculation and spheroidization.