Blog Euskatfund

Published on 03/06/2014 by Euskatfund

Reactive refractories coatings for cores and moulds

Reactive refractories coatings for cores and moulds

Foundriess are increasingly facing the problem of metal/mould reaction, which can cause defects in castings. Traditional coatings - even with high refractoriness - may not be sufficient to block and neutralize substances originating from the moulds and which react with the metal. The new series of coatingss AZ has been developed to solve this problem.
To reduce costs foundries are forced to minimize the amount of new sand introduced into the moulding system, whereby the sands with respect to the past, used and recycled many times. This implies an accumulation in the sand of certain substances such as oxides, salts, derivatives of reactions, compounds of sulfur, nitrogen and others, that will react with the metal when comes into contact with the sand mould.
The most obvious defect is formed in casting is due to the reaction of the magnesium content of nodular iron with sulfur compounds found in the sand. The result is an irregular, rough surface with small cavities; Sometimes it may be that pinholes or similar defects are formed.
The new series of coatings AZ contains refractories high quality, high melting point and good particle size distribution, forming a compact and resistant metal shell. Besides these coatings contain additives that prevent the reaction of these compounds with the molten metal.
Therefore s various surface defects are removed from the beginning, instead of using, for example, more new sand, which mean more costs and uncertain results.
The AZ coatings are available to water and alcohol, for steel and iron castings, and can be used with all types of castings or only in some particular cases most problematic castings.

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