INFLUENCE OF THE COMPOSITION OF GYPSUM-BASED FOUNDRY MOLDS ON THE MECHANICAL AND MICROSTRUCTURAL PROPERTIES OF THE ALUMINUM CAST PART.

Abstract

In order to simplify and cheapen the shell molding process, while still obtaining its advantages, plaster, with the addition of refractory materials, is applied to replace sand. Thus, it is proposed to study the influence of the proportions of the material used to make molds made of a mixture of plaster and refractory cement on the mechanical properties and microstructure of the casting. The casting for the tests was a specimen for casting according to the ASTM -E8 standard, using a mold with dimensions 140x326x400 mm. For the analysis, a proportion was used, taking into account the percentage according to the mold mass, initially with 100% gypsum and 80% gypsum and 20% refractory cement. 6063 aluminum and an oven with a maximum working temperature and pouring temperature of 854 ºC and 750 ºC, respectively, were used. There was an increase in strength and hardness in the mold parts with the refractory cement, in addition, by microscopy analysis, there was a reduction in the number of pores and micropores when compared to parts produced with the mold of 100% plaster, on the other hand these had a better surface quality.