Environmental characteristics of the reclaimed foundry self-hardening mould sands

Abstract

One of the most important environmental issues of foundries today is the efficient and effective recycling of the moulding sands which consist of the silica sand up to 95 %. In the world, the foundry industry produces millions of tonnes of various kinds of industrial waste. More than 70 % of that waste, which is disposed of in landfills, has made up the spent moulding sands. To increase the dimensional accuracy and surface quality of castings recently the chemically hardened moulding sands are increasingly applied in producing of moulds and cores. Their extended application, however, has entailed the potential ecological risks related to reclamation as well as to disposal or recycling of the used moulds and cores materials. The paper presents results of experiments focused on (1) the wet reclamation of the chemical bonded self-hardening mould sands with a bonding system based on the phenol-formaldehyde resin hardened by an addition of esterol and (2) studying the properties of the mould sands produced from the reclaimed sands. The experiments showed the mould sands can degrade after long-run water acting, and a polymer can be eliminated as drift substances or a leach. In comparison to cores produced from new sands, the cores made from the reclaimed sands exhibited the better wear resistant at inserting into the mould, and the surface quality of castings and holes was also higher.