The Influence of Thermal Expansion of Unbonded Foundry Sands on the Deformation of Resin Bonded Cores

Abstract

Depending on the preparation and the applied materials, moulds and cores can be of high rigidity or can be flexible. Although, chemically bonded moulding materials have relatively good flexibility, their high temperature behaviour determines the dimensional accuracy, the stresses in the castings and can induce several casting defects, such as rattail, veining, etc. The phenomenon is based on two major effects: the thermal expansion of the unbonded foundry sands and the deformation of the sand mixtures. The main objective of the present work was to study the relationship between these two effects, and to improve the knowledge related to the thermo-mechanical interactions between the casting and the mould. Dilatometric analysis of unbonded sand samples were performed and compared to the results of hot distortion tests of moulding mixture specimens. The results showed, that the thermal expansion of foundry sand largely influences the hot distortion behaviour, but depending on the type of binder used.

Influence the Composition of the Core Mixture to the Occurrence of Veinings on Castings of Cores Produced by Cold-Box-Amine Technology

“…the binder consists of component i and component ii. Component I consists of a liquid yellow synthetic resin with a density of 1.07-1.08 g ‧ cm -3 called gasharz 6747. component ii consists of a liquid solution of a modified brown isocyanate with a density of 1.21-1.23 g ‧ cm -3 in a separate solvent [13]. the binder consisting of components i and ii was added to the core mixture in a ratio 50:50 in an amount 0.7-1.2% designated a-e.…”

“…other authors [12] evaluate the effect of thermal deformation on cores produced by cold-and hot-box methods. the authors [13] study the correlation between thermal expansion and sand mixtures deformation.…”

The Influence of the Matrix Grain Size and Mineral Addition on Improving the Knock-Out Properties of Molding Sands with an Inorganic Binder

“…This is achieved by introducing a mineral material in the form of swelling aluminosilicate, specifically perlite ore. Research has demonstrated that the addition of perlite ore or ground vermiculite positively influences the reduction in the final strength and improvement in the knock-out properties [20,27]. Importantly, these additives do not adversely affect the mechanical and technological properties of the molding sands, the casting surface quality, or the ecological properties [28]. The molding sands also exhibit temperature stability, a crucial factor in preventing mold deformation when subjected to the high temperatures of liquid casting alloys [29].…”

Effect of the Composition of Hybrid Sands on the Change in Thermal Expansion

“…The relationship between grain size distribution and thermal properties such as thermal expansion is commonly studied in foundry research on unbonded and bonded sand samples [ 9 , 10 , 11 , 12 , 13 ]. From the mould/metal interface, the mould layers heat up to a certain temperature range due to the relatively low thermal conductivity of the porous mould.…”