Utilização de cimento de fosfato de magnésio como ligante na produção de moldes de areia para fundição.

Abstract

In this study it is discussed the possibility of the application of magnesium phosphate cement as an alternative binder for foundries sand moulds, due to the problem faced for foundries industries during the discard of yours toxics residues. Magnesium phosphate cement reacts by acid-basic mechanism, belongs to the class of chemically bonded ceramics and has excellent properties of adhesion, strength and mould ability. In this work, magnesium phosphate cement was made and analysed by the techniques of X ray difractometry and differential scanning calorimetry. The magnesium phosphate sand moulds setting time was adjusted, using a retarder and/or a low superficial area of the MgO component, considering the foundries parameters. Sand samples were made using phenolic resin binder and magnesium phosphate cement binder and analysed for the compression strength. Sand moulds were made using phenolic resin binder and magnesium phosphate cement binder and analysed with the mercury porosimetry technique. Sand moulds collapsibility, made with resin and cement, after casting metal was similar. After the solidification of the iron in the sand moulds described before, it was characterized by the techniques of scanning electronic microscopy (MEV), optic microscopy (MO) and colorimetric method (blue molybdenum photometry). The microstructures of the metals made in the sand moulds agglomerated with phenolic resin and magnesium phosphate cement was similar, as the piece finishing. The casting of metal, in the moulds of sand and cement, was also made in Metallux Foundry (São Carlos SP). The results obtained were very satisfactory compared as the resin sand mould, leading the Foundry to demonstrate interest for a future developing of a magnesium phosphate cement sand mould for industrial scale application.