The Influence of Technological Parameters of the Lost Foam Casting Process on the Microstructure of Cast Iron Modified by Disperse Ferrosilicon in the Mold Cavity
Processy litʹâ, 2020, Tom 140, №2, p.53-64
DOI:
https://doi.org/10.15407/plit2020.02.053Keywords:
lost-foam casting, gray cast iron, dispersed inoculator, perlite, cementite, lamellar graphiteAbstract
Received 25.04.2020
UDC 669.131.7:621.742.5
One of methods of preventing a chilling of cast iron is to modify it with the dispersed ferrosilicon FeSi75 DSTU 4127:2002 placed in the foam model. In this work, the dependence of structure parameters of the gray cast iron GJL300 DSTU 8833:2019 on the content of ferrosilicon in foam model, the model material density, the rate and temperature of metal pouring were investigated by the method of full-factorial experiment. As a result of mathematical processing of the experimental data, regression models were created for the quantities of perlite, cementite and lamellar graphite and the length of lamellar graphite. These models allowed us to derive the corresponding regression equations, the graphical interpretation of which showed the nature of the influence of each independent factor on the parameters of the cast iron microstructure. Thus, an increase in the content of disperse ferrosilicon in the foam model leads to a decrease in the amount of structurally free cementite while increasing the amount of perlite and lamellar graphite, which is caused by the graphitizing effect of silicon on the structure of the test material. The increase in the expanded polystyrene density has the same effect as in the previous case, but not so rapidly, which is explained by the restorative action of hydrocarbons, which are released during thermal degradation of the model material and create favorable conditions for the increase of the coefficient of silicon absorption by the matrix melt. Increasing the casting rate and pouring temperature of the liquid metal leads to an increase in the degree of turbulence of the stream and an increase in the intensity of convective flows, which also promotes better absorption of silicon and leads to a decrease in the amount of primary cementite and an increase in the amounts of perlite and lamellar graphite in gray iron structure. It was also found that the length of inclusions of graphite depends most of all on the content of disperse ferrosilicon in the foam model, and the smallest on the density of the model material.
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