Theory and practice of inoculation for high-grade gray cast iron railway castin

Abstract

JSC “Cheboksary Aggregate Plant” has mastered the production of high-strength gray cast iron "wedge friction" railway castings (grade SCH30) intended for freight wagon bogies. According to the casting's technical specifications, the presence of interdendritic graphite and cementite in the vertical and sloping walls of the casting is not allowed. However, in separate batches, interdendritic graphite and up to 10 % cementite were found in the controlled walls of the castings. To solve the problem of obtaining castings with a blemish-free microstructure, the iron modification technology was changed. Instead of ferrosilicon FS 75, a more effective composite dispersed inoculant was developed and implemented. The advantages of the latter, which consisted of chemically treated ultrafine modifier (USM) and a by-product of organosilane production (KSM), were theoretically substantiated. The advantages of the developed modifier over FS75 were confirmed by modeling the behavior of inoculant’s particles when filling the “wedge friction” cavities in the FLOW-3D program. USM and KSM particles were evenly distributed throughout the volume of the castings at all observed heights of the controlled casting walls. They served as graphite crystallization centers throughout the solidification time of the castings, ensuring the absence of blemishes in the castings. The introduction of the developed material into production allowed reducing the modifier consumption by 6.25 times, ensuring the absence of blemishes in the castings, achieving the required mechanical properties of the iron, and an economic effect of over 4 million rubles