Analysis of the sulphur content in moulding sands with furan resins

Among various sands with organic binders, moulding sands with furan resins belong to the group most widely applied in the manufacture of castings from ferrous alloys. This is due to a number of undisputable advantages offered by these sands, although they are not free from certain drawbacks, which ultimately can result in casting defects. The main disadvantage of furan resin sands is the fact that the binder contains nitrogen, sulphur and phosphorus, and all these elements are transferred in the course of casting from sand to metal. Additionally, producers of furan resins are forced to reduce the free furfuryl alcohol content to <25 wt. %, due to its toxic properties. Special attention deserves the presence of sulphur in moulding sand when castings are made from the cast iron with nodular or vermicular graphite. Then, as very often occurs, the effect of degradation of these two graphite forms take the shape of flake graphite. The study shows how to calculate the amount of sulphur introduced into the moulding sand together with binder, related to the acid catalyst composition (most often, its main components are various organic sulphonic acids). It is expected that the results will be useful in the selection of an optimum catalyst for a given type of furan resin.

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