Hodnocení sklonu nekřemenných písků k drcení

Abstract

This diploma thesis is focused on properties of natural and synthetic non-silica sands, which are increasingly used for making foundry moulds and cores. Hereafter are described their advantages and disadvantages in comparison with silica sands, which are most used. Because of economic aspect regeneration of them is necessary. Crushing of grains occurs with grain size diminution as a consequence of regeneration process. This may cause a change of their properties and casting defects may occur subsequently. Seven types of non-silica grog were chosen: natural – dunite, chromite, magnesite and shale; hybride sand kerphalite and synthetic sand cerabeads. Sands were subjected to mechanical testing and their tendency for crushing was evaluated. Change of mixture properties especially like water absorbtion, strength, permeability, consumption of binder and hardener; due to increased content of fine parts is described.