PRODUCTION OF DRY PHOSPHATE BINDERS FOR FOUNDRY CORES
The purpose is to create core mixtures with river quartz sand and phosphate binders, which have a minimum number of components and are not inferior to sand-resin mixtures in terms of properties.
Methods. A number of inorganic materials of technical purity were used in the experiments: sodium chloride, sodium carbonate, potassium chloride, potassium bromide, aluminum nitrate 9-aqueous, aluminum sulfate 18-aqueous, manganese sulfate 5-aqueous, sodium tripolyphosphate. As a result of the interaction of these materials with 85% aqueous solution of orthophosphoric acid, phosphate binders are formed when heated. The properties of the mixtures were determined on standard cylindrical samples with a diameter and height of 50 mm. In all experiments, river quartz sand was used as a filler 3К5О3025.
Results. Core mixtures with a new class of phosphate binder components have been developed, which are formed as a result of chemical interaction of orthophosphoric acid with inorganic metal salts. In order to simplify the processes of preparation of core mixtures, various options are considered and it is found that the method, which involves the use of ready-made dry water-soluble phosphates, is the most rational and fast.
The dependences of the strength of core mixtures on the ratio of orthophosphoric acid and inorganic metal salts during the synthesis of binders have been established. The optimal content of the developed binder components in the core mixtures has been determined. The influence of drying temperature of foundry cores on their strength has been studied.
Originality. For the first time, dry phosphate binder components for core mixtures were developed and the technology for their production was implemented. Pre-synthesized phosphate binder components are dry powder compositions and do not require the use of chemical hardeners. It has been established that the synthesis of such phosphates is possible in compositions of orthophosphoric acid with aluminum sulfate, manganese sulfate and sodium tripolyphosphate.
Practical implications. On the basis of the conducted researches three variants of structure of mixes for manufacturing of foundry cores are offered. The technology of their preparation is simple and little different from the technology of preparation of sand-resin cold-hardening mixtures. In terms of physical and mechanical properties, the developed mixtures are not inferior to industrial analogues.
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