Chemically bonded sand systems

An overall reclamation ratio of 92 %, as given above, is a normal value for mixed green sand -chemically bonded sand systems. Regeneration ratios of up to 98 % have been reported. The actual ratio depends on the volume and chemical composition of the used cores. For fiiran cold setting monosands, values around 78 % are reported. 

Thermal systems are normally used for chemically bonded sand systems and mixed sand systems, providing the share of chemically bonded sands (cores) is high enough. Nevertheless, a distinction can be made ... 

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. 

In the reclamation of chemically or resin bonded sands, the system employed must be able to break the bond between the resin and sand and remove the fines that are generated. The systems most commonly employed are wet washing and scrubbing for silicate bonded sands, or dry scrubbing/attrition and thermal (rotary drum or fluidized bed) systems for resin bonded sands. 

The most common example of a nonmetallic particle system in a nonmetallic matrix, indeed the most common composite material, is concrete. Concrete is particles of sand and gravel (rock particles) that are bonded together with a mixture of cement and water that has chemically reacted and hardened. The strength of the concrete is... 

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