4 major impacts of cast filter quality on filter performance

1. The influence of cast filter quality on thermal shock resistance

The quality of the filter has a certain impact on its thermal shock resistance, because when the filter is generally manufactured, Western medicine uniformly coats a specific proportion of high-temperature chemical raw materials on the glass fiber cloth carrier, and then makes it. become. And when casting, the position of the filter is generally as close as possible to the housing, and there is a certain height difference between the distance from the sprue cup, so the molten metal will produce a certain thermal shock to the filter under the action of the pressure head. This requires that the quality of the filter must be good and be able to withstand the thermal shock. An inferior filter will not be able to withstand it, causing cracking or even melting. In this way, it will not only be unable to effectively filter the molten metal, but will instead create slag.

2. The influence of cast filter quality on anti-chill performance

The casting filter is made of glass fiber yarn. The glass fiber yarn material is a non-metallic refractory material. The pouring temperature of casting molten iron is about 1400°C, and the molten steel is higher. When the hot metal liquid is immersed, the temperature difference is more than 1000 degrees. Among the filters, the anti-shock performance of the filter is a postgraduate test. Inferior filters may crack and break due to poor slurry preparation and sintering processes, resulting in the same consequences as the above-mentioned poor thermal shock resistance.

3. The influence of cast filter quality on pore uniformity

The filter relies on its internal adsorption and filtering of inclusions that are smaller than the gap size. Foundry workers are worried that premature clogging of inferior filters will cause defects such as lack of flesh and cold insulation in castings due to insufficient pouring, and in serious cases, they will be scrapped. To improve the porosity and pore uniformity of the filter, it must rely on the specific ratio of slurry, strict sintering process and high-quality glass fiber yarn. Different porosity can be made according to the type of casting alloy and process requirements. For example, most ductile iron uses a 10PPI filter with larger holes, which has about 10 holes per inch of length; most gray iron uses a 30PPI specification; it can also be made into 20PPI between the two. Inferior filters cannot actively control porosity at all, and the products are often roughly classified after they are fired. This type of filter appears to have holes on the surface, but its internal grid is blocked and has a large proportion of blind holes. If it is not crushed and melted by the molten metal during pouring, it will quickly become clogged. This indicator of the filter is mainly determined by visual inspection and pouring tests.

4. The impact of cast filter quality on dimensional accuracy

The dimensional accuracy of the cast filter screen includes the three-dimensional dimensional accuracy and flatness of the appearance. Whether the filter is used for green sand or self-hardening sand, it requires a small dimensional tolerance, which can fit well into the pre-made holes on the sand mold for placing the filter. . The high-quality filter king can neither cause the phenomenon of "big piece but small hole" that cannot be placed, nor will it cause the gap between the filter and the hole to be too large to cause side flow of molten metal.

The flatness of the filter is equally important. If it is warped, in addition to the easy side flow of molten metal during pouring, it will also cause uneven stress, especially for self-hardening sand molds, which increases the risk of damage due to the filter being unable to withstand thermal shock. sex. Dimensional accuracy can be measured using calipers. Flatness is determined by placing the filter on a flat surface (such as flat glass) to observe the degree of warpage.

In summary, the impact of cast filter quality on filter performance is mainly reflected in four aspects. One is the impact on thermal shock resistance; the other is the impact on chilling resistance; the third is the impact on pore uniformity; the fourth is the impact on pore uniformity. influence on dimensional accuracy. It can be seen that inferior filters not only do not help casting, but can also cause problems such as insufficient pouring, cold isolation, and increased inclusions. Therefore, when purchasing, we must choose high-quality filters.