What sand is used in casting?
According to the mineral composition of different silica sand and non siliceous sand are divided into two categories. The main mineral composition of silica SiO2. natural silica sand: for nonferrous alloy castings, cast iron and steel castings in small sand and core sand. The selection of the day However, for silica with organic binder as the molding sand and the core sand. The artificial sand for sand and core sand castings. Non siliceous sand non siliceous sand types, different uses. The limestone sand and limestone by crushing, the main mineral composition is CaCO3, for the sand and core sand castings. The zircon sand: the main mineral composition is ZrO2 - SiO2, for large steel castings and alloy steel core sand or sand sand surface, or be used as a coating powder. The main mineral composition of magnesia is MgO, for the high manganese steel casting surface sand and core sand, the powder can be used as the chromite sand coating. The main mineral composition is: FeO, Cr2O3, for large or special steel casting surface sand, sand core, the powder can be used as coating. The corundum sand: the main mineral composition is a -Al2O3, used for shell material, mould, ceramic mold casting. The olivine sand The main mineral composition is (MgFe) 2SiO4, used for sand castings and core sand for cast iron parts, non-ferrous alloy castings, and high manganese steel castings
Sand casting shall meet the following requirements: high purity and cleanliness, with silica sand as an example, iron sand as required by SiO2 content in 90%, cast steel a larger requests the SiO2 content above 97%; the high refractoriness and thermal stability; the suitable particle shape and particle composition; it is not easy to be wetted by the liquid metal; cheap. Particle shape and particle composition of casting sand permeability properties such as fluidity, compaction, permeability of sand resistance, strength and resistance to liquid metal effects, is an important indicator of quality of foundry sand. The particle shape casting sand shape. There are 3 kinds of sand particles were round or round, close to circular, smooth surface, no edges and corners. The more prominent Angle: sand particles into the polygon, and is the obtuse angle. The sharp angle: sand particles into the cusp shaped, and more acute. The particle shape casting sand generally by the angular coefficient (the actual surface area of sand / sand theory specific surface area) to express. (see pictures) particles of sand particles composition is expressed by screen size, determination of the method is that the washing to drying after the dry sand mud poured into the standard sieve, and then into the sand screen on the screen, the screen will stay after screening on the sand were weighed, and usually use the standard sieve 3 adjacent sieved sand most concentrated sieve the screen said on the casting sand particle composition.
In the year seventeenth Century has been Chinese silica sand is used as modeling materials, used in the manufacture of clocks, mirror, pots and artillery and other castings. But in the early stage for the natural clay sand that mountain sand and river sand, it has good plasticity, can be directly used in the manufacture of mold and core, suitable for handicraft production conditions. Enter mass production factory after, especially other mechanization, homogeneity of the properties of the natural silica sand clay is poor, it is difficult to control the sand quality, can not meet the technical requirements, so start with low clay content of natural silica sand and silica will be broken into artificial sand. At the same time, also expanded the use of various non siliceous sand. The development and application of resin sand core making process, the foundry sand quality also put forward higher requirements, such as fine powder, small specific surface area, low acid consumption. In addition, the sand size shape and size The cloth also has new requirements. Some lack of high-quality sand source countries also developed sand washing technique, in order to improve the taste and quality of silica sand.
