The role and requirements of sand cores are introduced
First, sand core role and requirements
1. the role of sand core
(1) the inner cavity and the hole of the casting must be formed with sand core for some complex cavities, which is an important function of the sand core.
(2) the formation of the casting shape is more complex for the external shape of the casting, such as convex and convex block more die and not hinder the demolition work, and having a curved shape complex, outer mold production difficulties, commonly used sand core to form the external shape of castings.
(3) to strengthen the local strength of the sand in the casting of large and medium sized castings, the sprue is usually high, scouring force metal, and on the same local scour time, these places are often due to insufficient strength and sand was washed away.
2. requirements for sand cores
(1) low hygroscopicity and moisture content of sand core Fanchao, will reduce the strength of the sand cores, while increasing the gas volume of the sand core, the casting defects such as blowhole.
(2) the good permeability in the casting process, sand and sand core temperature rise, rapid evaporation, combustion, decomposition of organic matter, volatile, inorganic chemical reaction, which will produce large amounts of gas.
(3) a good ductile casting will produce greater stress during the cooling process. If the sand core is not good in toughness, the casting may be deformed and even crack.
(4) high refractoriness, during the pouring process, the sand core is baked by high temperature metal liquid for a long time, and it is easy to cause sand sticking on the surface of casting.
(5) good sanding performance will reduce the amount of cleaning work and improve the surface quality of casting.
(6) high dimensional accuracy. The sand core mainly forms the inner cavity and the hole of the casting, and these places are no longer machined.
(7) good stability and balance, only with good stability and balance, can ensure that the sand core is easy to operate and stable and reliable during the lifting and unloading of the core.