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Due to the low flowability of certain inorganic binders and the position of shoot tubes, sand channels or bridging could develop in a core- making machine designed for organic binders.


General Machine Requirements Inorganic sand mixtures generally


are alkaline and show traces of various salts. For this reason, machine parts that come in contact with the mixture should be manufactured out of corro- sion resistant materials. Inorganic cores do not have the


same strength as cores made with organic binders immediately after manufacturing. Te core strength improves after drying and cooling. Tis has to be taken into account when handling the cores (e.g. removal, fettling, assembling). Te speed and clamping pressure of the handling mechanisms in both manual and auto- matic machines have to be adjusted accordingly. As in all warm/hotbox processes, definning should be done at a constant temperature after cooling. Definning at different temperatures can lead to core damage. Te cores should be stored in a room with a controlled, low humidity to avoid quality degradation.


INORGANIC CORES IN SUMMARY


Inorganic core production can reduce costs and environmental impact, but the parameters of the binder systems must be kept within tight limits to ensure it is a successful alternative to organic core production.


The need for hot tooling when working with inorganic binders is the main restriction at this time. Due to high tooling costs, small batch or single core production is not cur- rently economical.


Several impediments to using inorganic materials have been solved, including the challenges associated with reclaiming the product and using it with high melting point materials.


30 | MODERN CASTING October 2012


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