Analysis on the Defect of Anti-Penetration Casting with Ceramic Foundry Sand
Release time： 2020-08-17 09:50:00.000
Ceramic foundry sand is spherical particles, the main component is alumina, its refractory temperature as high as 1800 ℃.It has been proved by practice that the adoption of ceramic foundry sand can obviously reduce mechanical and chemical metal penetration, labour intensity of cleaning sand and defects such as sand inclusion, sand washing and blowhole.
Chromite sand is used to prevent penetration of liquid metals, usually because molten chromite closes sand gaps.Serious metal penetration defects often occur when chromite sand is used as surface sand material by domestic factories producing large steel castings, which seriously affects the surface quality of steel castings.It has been shown that this is because the iron in the chromite is reduced by the redox reaction between the chromite and the high chromium steel or between the chromite and the carbonized film of resin at the interface. The reduced iron forms a dense mixture with the sand particles and adheres closely to the casting surface to form glazed penetration.In addition, the use of high clay content, impurities in the chromite sand casting, also often produce metal penetration defects.
Because of its high refractoriness, the thermal expansion rate of ceramic foundry sand is almost zero; Its anti-metal penetration mechanism is due to its particle size is very small, closing the gap between the sand.In addition, because the sand grains are close to spherical, they have good mobility, can make the binder cover evenly, can get smooth surface, compact structure of the mold and have good air permeability. Using ceramic foundry sand as face sand can not only improve the dimensional accuracy of castings, prevent molding sand sintering, sand inclusion and metal liquid infiltration, but also greatly reduce the workload of cleaning and finishing castings and improve the working conditions of workers.
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