OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 1 2024 In foreign literature the names compacted, vermicular, worm-shaped [22, 23, 25] can be found. In the domestic literature the term vermicular is used [24]. The intermediate graphite (CG) morphology provided an advantageous combination of the mechanical properties of ductile iron and the physical properties of gray cast iron. The purpose of this work is to identify the formation of the morphological form of graphite with the introduction of a combined modifi er from silicon production waste. The objectives of the work are: 1) to conduct research to assess the modifying eff ect of a combined modifi er obtained from silicon production waste in the smelting of gray cast iron; 2) to determine the eff ect of the combined modifi er on the nucleation of vermicular graphite; 3) to analyze the eff ects of compression/expansion during the crystallization of cast iron when using a combined modifi er. Experimental technique Experimental cast iron (type SCh15) was smelted in an electric induction furnace (15 kg; 8,000 Hz) using cast iron scrap, FeSi and carbonaceous material. The melt, heated to 1,500 °C and held in the oven for 5 minutes, was released into a pouring ladle at a temperature of 1,480 °C and poured into a sand mold made of furan resin at a temperature of 1470 °C. Cylindrical rods were produced (30 mm in diameter and 100 mm in height). A combined modifi er based on silicon dioxide and silicon carbide was added to the bottom of the mold cavity (additive from 0.5 to 1.5 wt. %, grain size less than 1.0 mm). Research included: determination of the chemical composition of cast iron; determination of specimens’ hardness using the Brinell method; tensile testing of specimens; study of the macro- and microstructure of gray cast iron. The combined modifi er was obtained from cyclone dust waste by fl otation treatment [1, 7, 32, 33]. The appearance of the modifi er is shown in fi gure 1, and the composition of the crystalline phase in Table 1 and fi gure 2. Compacting the modifi er was carried out from the resulting mechanical mixtures either by tableting using a press, or a product was obtained manually globulated using paraffi n. When analyzing the convex shape factor, the diff erence between the real and convex perimeter of the graphite particles is fi rst determined and then the resulting value is divided by the ratio of the square root of the convex perimeter to the real perimeter of the measured particle. The roundness shape factor is commonly used to defi ne the diff erent morphologies of graphite in cast iron, from fl ake to vermicular to nodular graphite, including various subclasses for each type of graphite. The graphite roundness shape factor (RSF) is considered (according to the international standard ISO 945-4-2019) to be a characteristic of the representative morphology of graphite in cast irons. The international standard ISO 16112:2017 “Compacted graphite cast irons – Classifi cation” [25] defi nes some of the graphite morphologies that may be present in this type of cast iron. In this RSF standard, a b Fig. 1. The appearance of the combined modifi er: formed out of silicon production waste (a); electronic photography of the structure (b)
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