Plasticity Changes of Moulding Sands with Chemical Binders Caused by Increasing the Hardening Degree

The results of investigations of plasticity of moulding sands with binders obtained by measuring deflection angles in the single point bend test in dependence on their hardening degree are presented in the hereby paper. Shaped samples made of moulding sands obtained in the technology with urea-furfuryl resin Furanol FR75A and in the technology with water glass, were subjected to various tests. Shaped samples were made on the quartz matrix of a medium grains size =0,29 . Investigations were performed for the resin content being 1% and 2%, at a constant proportion of a hardener versus resin - equal 60%. In the case of sands from the technology with water glass, investigations were performed for 3.5% of water glass versus sand matrix and 0.35% of Flodur. Plasticity tests were carried out with using the strength machine with a continuous recording of a sample deflection value. Measurements of deflection angles values in the bend test were performed on a series of simultaneously made samples at constant time intervals from the moment of their making. To determine the sand hardening degree the ultrasound technique was applied, according to the previously developed methodology [1]. Every time from the obtained results the characteristic of the growing stress as a function of deflection was prepared (). In addition, for the tested group of moulding sands, empirical relationships between the maximum deflection angle (αmax) in the bend test and the hardening degree were determined (Sx): α = f(Sx)