EFFECT OF GRAIN SIZE OF THE RECLAIMED MATRIX CERAMIC MOULDS USED IN THE LOST WAX TECHNOLOGY ON THE STRENGTH AT HIGH TEMPERATURE

Abstract

Production technology of investment casting involves transmitting the elements of shape, dimensions and properties by filling in the appropriate liquid metal ceramic forms reproduccd by a model made of wax removed by melting it. The manufacturing process of investment casting in the lost wax technology consists of a number of technological operations: preparing of wax models and their assembling in the model units, the preparation of ceramic mixture, successive layers of debris, wax melting in an autoclave, drying the samples at 100 °C, heating the samples at temperatures ranging from 400 to 700 °C. So far, the technology was based on the use of ceramic mixture, which the bond was hydrolysed ethyl silicate. Currently, due to environmental protection and improvement of working conditions, more and more binders with alcohol is replaced with an aqueous solution of colloidal silica. In the study, as the basic of individual layers a ceramic form, used regenerated ceramic mixture derived from foundry and green ingredients. Used ceramic moulds after mechanical reclamation was given to sieve analysis to determine the grain size (dL). Grain sizes 0.2, 0.4 and 0.63 mm were used for the coating of ceramic moulds. The paper presents results of research aimed at the determination of the relationship between tensile wet strength and grain size of ceramic mould: Rm =f(dL). Tests were conducted on cylindrical samples, which deposited a layer of reclaimed ceramic material.