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Standards for the appearance of silicone investment castings


Customers' demand for silica sol precision casting is growing in tandem with the rapid development of my country's foundry industry and advancements in casting technology. Many customers who are unfamiliar with iron castings do not understand the flaws in the product's appearance and assume that the cast product should be defect-free. Let's discuss the criteria for judging the appearance quality of silica sol precision casting blanks today.

1. Cold insulation—in areas with relatively fine casting structures, cold insulation is generally caused by low molten iron temperature and slow pouring speed, which leads to cold doubts before the molten steel is fully covered with the mold shell, resulting in microstructure defects. Cold insulation reduces casting strength, affects casting physical properties, and can even crack high-quality railway castings in severe cases, so it must not exist on the surface of castings.

2. Cracks—The cause of cracks is that the cooling rate at each position is inconsistent during the casting condensation and shrinkage process, resulting in shrinkage resistance. When the frictional resistance of the casting exceeds the yield limit of the raw material, cracks form. Cracks cause damage similar to cold snaps and decrease the compressive strength and physical properties of castings. As a result, cracks on the product's surface are not permitted to be accepted.

3. Inadequate pouring-Inadequate pouring of castings is commonly caused by the cumbersome structure of the castings and the small passage in the mold shell, resulting in a lack of circulation of molten steel products to some parts. Inadequate pouring has a negative impact on the appearance of the casting and is therefore unacceptable.

4. Holes— Air vents, sand holes, and shrinkage porosity are examples of holes. Within the range of 50 mm, we allow one hole with a diameter of 0.5 mm and a depth of 0.5 mm without compromising the properties of high-quality silica sol castings. More than one is considered passing.


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