Effect of FeSi, FeB and FeSiB Ferroalloy Modifiers on the Microstructure and Mechanical Properties of High-Strength Cast Iron

Abstract

This study investigates the effect of ferrosilicon (FeSi), ferroboron (FeB), and complex ferrosilicoboron (FeSiB) modifiers on the microstructure and mechanical properties of high-strength cast iron produced by laboratory induction melting. Experimental melts (20-30 kg) were conducted in a medium-frequency induction furnace at 1450-1500 °C; the molten metal was poured into clay-sand molds at 1400-1450 °C. Mechanical properties were evaluated in accordance with ASTM E8/E8M (Standard Test Methods for Tension Testing of Metallic Materials), and microstructural analysis was performed by optical microscopy at magnifications of ×100-×500. The application of FeSiB at 0.3 wt.% of the melt yielded the highest tensile strength of 392 MPa - a 46% improvement over the unmodified control (268 MPa) - and the highest ductility (δ = 2.1%), demonstrating a clear synergistic effect of the combined silicon-boron system. Modification with FeB substantially increased hardness (236 HB) through formation of dispersed boron-containing carbide phases, while FeSi produced moderate improvements in both strength and graphite morphology. The results show that complex FeSiB modifiers are the most effective for simultaneously optimizing strength, hardness, and ductility in high-strength cast iron.