Sand casting systems

In addition to green sand molds, chemically bonded sand cast systems are also used. These systems involve the use of one or more organic binders in conjunction with catalysts and different hardening/setting procedures. Foimdry sand makes up about 97% of this mixture. Chemically bonded systems are most often used for cores (used to produce cavities that are not practical to produce by normal molding operations) and for molds for nonferrous castings. 

For high-volume production of parts, automated sand casting systems are used which result in very low component costs. 

The sand, mostly quartz, needs to be very permeable, in order to ensure the evacuation of the pyrolysis gases. Sand with an AFS-number of 35 - 50 is used. Interruption of the pouring may cause a collapse of the sand mould. Therefore an automatic casting system is often used. 

The techniques to produce cores with bonded sands are well established. Conventional binder systems, organic as well as inorganic ones, are widely used in sand casting foundry applications. There are still many open issues to reduce casting defects associated with the sand-binder system as discussed previously. It was also shown that RF aerogels as binders can overcome some of the problems encountered with conventional polymeric binders. 

Currently, systematic studies are carried out to optimize the core and casting quality as a function of the used sand-binder system in combination with aerogelic nanoadditives. 

With sand casting, probably the most common method, ordinary sand is used as the mold material. A two-piece mold is formed by packing sand around a pattern that has the shape of the intended casting. A gating system is usually incorporated into the mold to expedite the flow of molten metal into the cavity and to minimize internal casting defects. Sand-cast parts include automotive cylinder blocks, fire hydrants, and large pipe fittings. 

Silt, sand, concrete chips, shells, and so on, foul many cooling water systems. These siliceous materials produce indirect attack by establishing oxygen concentration cells. Attack is usually general on steel, cast iron, and most copper alloys. Localized attack is almost always confined to strongly passivating metals such as stainless steels and aluminum alloys. 

As the assembled molds are being placed on the pour-off lines, the scrap metal is melted in the furnace. Molten metal from the furnace is brought to the molds on the pouring lines in a refractory lined pouring ladle. Once poured, the molds are allowed to cool before being sent to the shakeout processes. At the shakeout, the castings are separated from the sand mold. The sand is sent to a reclamation system so that it can be reused in the molding process. 

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