Alignment of the microstructure of castings from the heterophase lead bronzes

This paper reports on the use of nanopowders in the coating composition forms in casting blanks from lead bronzes for the petrochemical industry. Influence of composition of used protective separating coating of casting mold on the microstructure castings was investigated. For experimental investigations the following coating were selected [1]: the mixture of zirconium dioxide nanopowder with industrial oil and the same composition as it's, but on the basis of aluminum oxide nanopowder. As the test material multicomponent and lead bronzes were selected. The cooling curves castings using coatings of different compositions by means of the developed device thermograph were constructed using techniques developed by the authors. The study results showed that the greatest reduction in the cooling rate at the time of crystallization bronze corresponds to coating casting mold based on powder of zirconium dioxide (45 °C/c). The cooling rate is reduced only to 65 °C/c when coating was based on aluminum oxide. Decrease the cooling rate of castings using these coatings can change the shape and size of lead inclusions and align the casting structure in section. Form inclusions lead is becoming more spherical and their interfacial surface is leveled. The greatest changes occur in the surface layers of castings. Is shown that the multicomponent bronzes decreased speed the cooling due to the use plasters leads not only to changes in the morphology of inclusions but also to lead the change in the phase composition. Decrease of cooling rate leads to increasing the amount of eutectoid and growth of hardness casting.