RESEARCH ON THE POSSIBILITY OF IMPROVING THE HIGH-STRENGTH CAST IRON MECHANICAL PROPERTIES TAKING INTO ACCOUNT THE RECOMMENDATIONS OF THE DSTU EN 1563:2019 STANDARD

https://doi.org/10.33815/2313-4763.2024.2.29.084-097

Keywords: high strength cast iron, spheroidal graphite, ferrite, pearlite, “sandwich”-process, relative elongation, ultimate tensile strength, carbon equivalent

Abstract

The technological issues of the strength and relative elongation of high-strength cast irons (HSCI) are considered in the paper. The main method chosen is to increase the silicon content to obtain a ferrite matrix strengthened by the solid-solution mechanism. To ensure low production costs, special attention was paid to determining the permissible content of trace and harmful impurities in order to use cheap commercial scrap. The issue of the stability of the mechanical characteristics of cast iron during fluctuations in the technological parameters of its production is also considered. It is shown that main sources of variability in characteristics are the instability of the results of metal processing in the ladle when using the “sandwich” process, as well as fluctuations in the content of trace and harmful impurities due to the instability of the quality of metal scrap. It was found that in the studied range of chemical composition, an increase in the content of magnesium and silicon contributes to a simultaneous increase in the strength and ductility of cast iron, while an increase in the content of manganese increases the strength but reduces the ductility. It is shown that to obtain a relative elongation A5 ≥ 14%, the content should be: S < 0.006, P < 0.02, Cr < 0.04. The Sn < 0.008% does not create a negative impact on the mechanical properties of HSCI. It was also found that with an increase in the content of silicon and magnesium in cast irons with a high carbon equivalent at a high pouring temperature, a tendency to form torn and star-shaped graphite appears, which leads to a decrease in the mechanical characteristics of cast iron. It is recommended to introduce additional metallographic control for the presence of particles of this morphology in the structure.

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Published
2025-01-24
Issue
Vol 2 No 29 (2024): Scientific Bulletin of the Kherson State Maritime Academy
Section
MATERIALS SCIENCE