OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 1 2024 Ta b l e 1 The composition of the crystal phase of the combined modifi er according to XRD results No. Phase Content (%) 1 SiO2 (Quartz) 50 2 SiC (Moissanite) 35 3 SiO2 (Cristobalite) 10 4 C (Graphite) 5 Fig. 2. Diff raction pattern of the combined modifi er nodular graphite (ISO Form VI) was defi ned using RSF = 0.625–1.0, with intermediate forms of graphite (ISO Forms IV and V) with RSF = 0.525–0.625 and vermicular graphite (ISO Form III) with RSF < 0.525. In our case, the graphite roundness shape factor (RSF) was in the range of 0.425–0.519. Results and discussion The chemical composition of specimens of gray cast iron and with modifi cation is presented in Table 2. It can be seen that the use of the modifi er does not signifi cantly change the chemical composition of gray cast iron, with the exception of a slight increase in silicon by 0.1 %. It is known that for gray cast iron the main indicators of mechanical properties are the minimum value of tensile strength and hardness. Table 3 presents the results of mechanical tests of witness cast iron and specimens after modifi cation. It can be seen that with the same chemical composition, the use of a modifi er increases the mechanical properties of the casting. The study of the macro- and microstructure of gray cast iron was carried out in accordance with GOST 3443-87 using optical and electron microscopy, which made it possible to identify the peculiarities of the infl uence of modifi ers. Figs. 3, 4 present the results of optical and electron microscopy. Typically, the eutectic solidifi cation unit is represented by austenite and plate-shaped graphite (fi gure 3). In all cases, a predominantly lamellar structure of Gf1 type graphite is observed according to GOST 3443-87. Foundry practices can infl uence the nucleation and growth of graphite fl akes such that size and type improve
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