Abstract
More and more foundry plants applying moulding sands with water-glass or
its substitutes for obtaining the high-quality casting surface at the
smallest costs, consider the possibility of implementing two-layer moulds,
in which e.g. the facing sand is a sand with an organic binder (no-bake
type) and the backing sand is a sand with inorganic binder. Both kinds of
sands must have the same chemical reaction. The most often applied system
is the moulding sand on the water-glass or geopolymer bases – as the
backing sand and the moulding sand from the group of self-hardening sands
with a resol resin – as the facing sand. Investigations were performed for
the system: moulding sand with inorganic GEOPOL binder or moulding sand
with water glass (as a backing sand) and moulding sand, no-bake type, with
a resol resin originated from various producers: Rezolit AM, Estrofen,
Avenol NB 700 (as a facing sand). The LUZ apparatus, produced by Multiserw
Morek, was adapted for investigations. A special partition with cuts was
mounted in the attachment for making test specimens for measuring the
tensile strength. This partition allowed a simultaneous compaction of two
kinds of moulding sands. After 24 hours of hardening the highest values
were obtained for the system: Geopol binder - Avenol resin.
Go to article