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Foundry Sand

Release time： 2020-05-27 11:06:00.000

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There are many kinds of foundry raw sand, such as silica sand, chromite sand, ceramic sand, clinker sand and so on. Foundry sand can be divided into two types according to mineral composition: silica sand and non-silica sand.

The foundry sand shall meet the following requirements:

①Higher purity and cleanliness, taking silica sand as an example, the content of SiO2 is required to be more than 90% for cast iron sand and more than 97% for larger steel castings;

②High refractoriness and thermal stability;

③Appropriate particle shape and particle composition;

④Not easily infiltrated by liquid metal;

⑤Cheap and easy to get.

The particle shape and composition of foundry sand affect the fluidity, compactness, permeability, strength and resistance to penetration of liquid metal of the sand, which is an important index of the quality of foundry sand.

Particle Shape

There are generally three shapes of casting sand.

①Round sand: The particles are round or nearly round, with smooth surface and no protruding edges and corners.

②Polygonal sand: The particles are polygonal and most of them have obtuse angles.

③ Sharp Angle Shaped Sand: The particles are sharp angle shaped and most of them are acute angle. The particle shape of casting sand is generally expressed by angle coefficient (sand actual specific surface area/sand theoretical specific surface area).

Particle Composition

The particle composition of the sand is expressed by the sieve number, the measuring method is to pour the dry sand after washing to remove mud and drying into the standard sieve, then put it on the sieve machine for sieving, and weigh the sand staying on each sieve respectively after sieving, usually the particle composition is expressed by the top and bottom sieve numbers of the three adjacent sieves where the sand is most concentrated after the standard sieve.

According to the different mineral composition, foundry sand can be divided into silica sand and non-silica sand.

Silica Sand: The main mineral composition of silica sand is SiO2.

①Natural silica sand: used for non-ferrous alloy castings, iron castings and small and medium-sized steel castings molding sand and core sand.

②Selected natural silica sand: used in all kinds of molding sand and core sand with organic binder.

③Artificial silica sand: used for steel casting sand and core sand.

Non-siliceous Sand: There are many kinds of non-siliceous sand with different uses.

①Limestone sand: crushed from limestone, the main mineral composition is CaCO3, used for steel casting sand and core sand.

② Zirconium sand: the main mineral composition is ZrO2 · SiO2, which is used as core sand of large steel castings and alloy steel castings or surface sand of sand molds, or its powder is used as coating.

③Magnesite sand: the main mineral composition is MgO, used for high manganese steel castings surface sand, core sand, the powder can be used as paint.

④ Chromite sand: Its main mineral composition is FeO · Cr 2O 3, which can be used as face sand and core sand for large or special steel castings, and its powder can be used as coating.

⑤ Corundum sand: main mineral composition is α-Al2O3, used for making shell material in investment mould and ceramic mould casting. (6) Olivine sand, mainly composed of (MgFe) 2SiO4, is used in molding and core sand for iron castings, non-ferrous alloy castings and high manganese steel castings.

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