OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 1 2024 [8–13] to be absorbed at graphite-iron interfaces and are likely to increase the undercooling required for growth, especially at the hexagonal facet plane. graphite lattice shapes. As a result, the direction of graphite growth changes to normal to the plane of the face (a-direction) and lamellar graphite is formed [1, 15-18]. Therefore, when producing compacted graphite cast iron, elements (Mg, La, Ce, etc.) are usually added to consume the surfactants around the graphite. As a result, graphite grows alternately in the a direction and then in the c direction, forming vermicular graphite [8–11]. In our case, compounds of silicon dioxide and silicon carbide perform the same roles, which leads to a change in the morphology of graphite in gray cast iron. It is important to note that for decades, graphite shapes in cast iron have been assessed by comparing microscopic images to stylized reference images, with a preferred magnifi cation of 100× [23–25]. Two different approaches to graphite classifi cation have been standardized by ISO and ASTM (see fi gure 5) and the domestic standard [24], which diff er in the number, name and examples of graphite particles depicted (fi gure 5). However, when analyzing foreign and domestic standards, all evaluation approaches subjectively change the shape of graphite from lamellar to nodular with some more or less degenerate shapes in between. In fi gure 5, we took the requirements for graphite morphology from each standard and combined them in one drawing. The domestic standard [24] contains more than 13 types of graphite morphology and is designated by the letters Г with the corresponding index. For example [22–25], the EN ISO 945-1 defi ned VI ISO and V ISO shapes can be considered similar to ASTM I ASTM and II ASTM shapes, although II ASTM are convex particles whereas V ISO shape appears more star-shaped. Both forms contain the desired round particles as well as less round particles that are not likely to aff ect the mechanical properties. IV ISO and III ASTM forms contain particles that are common in ductile iron, but the forms presented are diff erent. IV ISO and III ASTM forms are compacted particles that are desirable in ductile iron and may also be found in nodular cast iron. II ISO form is a stylized representation of degenerated graphite particles known as pointed or intercellular graphite, which is mainly formed from trace elements. Unlike its stylistic image, this form does not appear independently, but Fig. 5. Various standard approaches to graphite classifi cation: upper row: graphite types in accordance with EN ISO 945-1, middle row: graphite types in accordance with ASTM A247 – 16a. 9, lower row: graphite types in accordance with GOST 3443-77
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