Assessment of core sands suitability for filling the core box and for compaction - by blowing methods

The obtained effects of filling the core box cavity and moulding sand compaction in processes of core production by blowing methods (blowing, shooting) depend on several factors. The most important are: geometrical parameters of cavity and complexity of its shape, number, distribution and shape of holes feeding sands as well as the way of deaeration of a technological cavity. Values of individual parameters are selected according to various criteria, but first of all, they should be adjusted to properties of the applied core sand. One of the ways of a preliminary estimation of suitability of a core sand for filling the core box and for compaction by means of blowing methods is the determination of its fluidity and assessment how this parameter is changing when core sand is awaiting to be shot. Another criterion of suitability of core sands for the blowing process is their apparent density obtained at filling the testing core box of a complicated shape (Boenisch test). Various methods developed by several researchers, including the authors, allow to assess the tested property on the basis of special technological tests projecting the process into a laboratory scale. The developed criteria defining a degree or a filling ability factor provide a better possibility of assessing the core sand behaviour during flowing and core box filling, which indicate the value and structure of the obtained compacting decisive - after hardening - for strength and permeability. The mentioned above aspects were analysed - on the basis of authors' own examinations - in the hereby paper.